Quaternary Geology 

of Alaska 

By TROY L. PEWE 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 835 

A study of the glacial, periglacial, eolian, fluvial, 

lacustrine, marine, and volcanic deposits of 

Quaternary age in Alaska and paleoclimatic 

fluctuations in light of formation and 

disappearance of glaciers and permafrost 

and changes in the distribution of 

plants and animals 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1975 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

First printing 1975 

Second printing 1977 

Third printing 1983 

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract __ __ __ _ _ _ ___ __ _ _ __ ___ _ _ _ ___ _ _ _ _ _ _ _ __ _ _ __ __ _ _ _ __ _ __ 1 

Introduction ---------------------------------------------- 2 

Geography____________________________________________ 2 

Location and extent of area ________________________ 2 

Physiography __ _ _ _ _ __ __ _ _ _ _____ __ _ _ _ _ __ _ _ _ _ _ _ _ _ __ 2 

Climate _ _ _ _ __ _ _ _ _ _ _ __ ___ _ _ _ __ __ __ _ _ _ ___ _ _ _ _ _ _ _ _ _ _ 2 

Acknowledgments _ _ _ _ _ _ _ _ __ ____ _ _ _ __ ____ _ _ _ _ _ __ ___ _ _ _ 5 

History of research ---------------------------------------- 5 

Glaciology -------------------------------------------- 6 

Glacial stratigraphy _ _ __ _ ____ ___ _ _ __ __ __ _ _ _ _ ___ _ ____ _ _ 7 

Nonglacial deposits____________________________________ 9 

Archaeology _ _ _ _ _ _ _ _ _ _ __ _ _ __ _ _ __ _ __ __ _ _ _ __ ____ _ _ _ _ ____ 9 

Marine deposits _ _ _ _ __ __ __ _ _ _ _ _ _ _ _ ___ _ _ _ ____ _ _ _ _ _ _ ____ 10 

Periglacial studies __ _ _ _ _ _ _ _ _ _ _ _____ _ _ _ _ _ ____ _ _ _ _ _ _ ____ 10 

Volcanic activity ___ _ _ _ _ _ ___ _ _ _ __ ___ _ _ _ _ _ ____ __ _ _ _ _ __ __ 11 

Paleomagnetic studies _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 11 

Quaternary tectonism ______ __ __ __ _ _ _ _ _ ___ __ _ _ _ _ ____ __ 11 

The Pliocene-Pleistocene boundary ________________________ 11 

Glacial geology____________________________________________ 15 

Evidence of Miocene to early Pleistocene glaciation______ 16 

Early Pleistocene glaciations -------------------------- 17 

Glaciation of Illinoian age ---------------------------- 18 

Distribution of drift ------------------------------ 18 

Basis for age assignment -------------------------- 19 

Evidence of multiple glacial advances ______________ 19 

Surface morphology _ _ __ ____ _ _ __ __ __ _ _ _ _ _ ___ __ _ _ _ _ 19 

Soils and weathering profiles ______________________ 19 

Snowline __ ____ __ __ ___ _ ____ _ ____ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ 21 

Significance of the distribution pattern of Illinoian 

drift ----------------------------------------- 21 

Glaciation of Wisconsinan age-------------------------- 21 

Distribution and extent---------------------------- 21 

Basis for age assignment __________________________ 24 

Surface morphology _ _ __ _ _ __ _ _____ _ _ __ _ _ ___ _ _ _ __ __ 25 

Soils and weathering profiles ______________________ 25 

Snowline _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ __ __ _ _ ___ _ _ _ _ _ __ _ _ _ _ 26 

Modern snowline------------------------------ 27 

Methods of determination__________________ 27 

Modern snowline in Alaska ___ _______ ___ ___ 28 

Methods used in this report ____________ 28 

Interpretation of the map______________ 28 

Wisconsinan snowline ------------------------ 30 

Methods of determination__________________ 30 

Methods used in this report _______ _________ 30 

Interpretation of the map __________________ 31 

Holocene glaciations ---------------------------------- 32 

Summary -------------------------------------------- 34 

Eolian deposits ___________________________ ~_____________ ___ 34 

Sand dunes ------------------------------------------ 35 

Active dunes-------------------------------------- 35 

Stabilized dunes _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 

Illinoian _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 

Wisconsinan and post-Wisconsinan _________ ___ 36 

Ventifacts -------------------------------------------- 37 

Loess ------------------------------------------------ 37 

History _ _ _ _ __ _ _ _ __ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ 37 

Page 

Eolian deposits-Continued 

Loess-Continued 

Origin and physical characteristics ________________ 37 

Distribution and thickness ________________________ 40 

Stratigraphy _ _ __ __ _ _ ______ _ _ ___ __ _ _ _ ____ ____ _ _ ____ 40 

Rate of deposition -------------------------------- 42 

Summary __ _ __ _ _ __ _ _ _ _ _ __ _ _ ___ _ _ __ __ ___ _ _ _ _ __ __ __ ___ _ 42 

Permafrost and periglacial deposits ------------------------ 43 

Permafrost____________________________________________ 44 

Ground ice____________________________________________ 48 

Ice wedges _ _ __ __ _ _ _ _ _ _ __ _ _ __ _ __ _ _ ___ _ ___ _ _ __ ___ _ __ 49 

Age of ice wedges -------------------------------- 53 

Ice wedge casts____________________________________ 53 

Pingos____________________________________________ 56 

Geochemistry of permafrost ---------------------------- 59 

Periglacial processes and deposits ______________________ 61 

Thermo karst features__________________________________ 65 

Geobotanical periglacial features ---------------------- 66 

Summary __ __ _ ___ __ _ _ __ __ __ _ __ _ __ _ _ ____ ___ _ __ _ ___ _ _ _ _ 66 

Fluvial deposits __ _ _ _ ___ ___ _ _ _ _ ___ ___ _ _ _ _ _ __ _ _ _ ___ ____ _ ___ 67 

Yukon Flats _ _____ _ _ __ ___ _ _ _ _ ___ __ _ _ _ ___ _ ___ _ _ ____ __ _ _ 67 

Tanana River valley ---------------------------------- 67 

Kuskokwim region _ _ _ __ _ __ __ _ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __ _ _ 68 

Koyukuk River valley -------------------------------- 68 

Other fluvial basins ---------------------------------- 69 

Northern Alaska _ _ ___ _ _ _ __ ____ _ _ ___ __ _ _ _ _ _ _ _____ _ _ __ __ 70 

Deltas of Yukon, Kuskokwim, and Colville Rivers ______ 70 

Auriferous gravel of central Alaska ____________________ 70 

Lacustrine deposits---------------------------------------- 70 

Central Alaska _________________________ _: ______________ 70 

Nenana River valley --------------------------=-------- 72 

Copper River Basin____________________________________ 72 

Cook Inlet _ _ __ ____ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ ___ _ __ __ __ __ _ _ __ __ 73 

Middle Koyokuk River valley -------------------------- 74 

Western Brooks Range -------------------------------- 74 

Summary __ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ ___ _ ___ ___ __ __ 7 4 

Marine deposits ____ __ _____ _ _ _ _ _ _ _ __ ___ ____ _ ____ __ ____ ____ 7 4 

Beringian transgression _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 4 

Anvil ian transgression _ _ _ _ _ _ ___ _ _ __ __ __ _ _ __ _ __ _ ___ _ ___ 76 

Einahnuhtan transgression ---------------------------- 76 

Kotzebuan transgression _ _ _ __ _ __ _ _ __ _ __ _ _ _ __ __ _ _ _ _ __ _ _ 76 

Pelukian transgression _ _ _ __ _ _ __ _ _ __ _ __ _ _ _ _ __ __ _ _ __ ___ _ 77 

Woronzofian transgression _ _ _ _ _ _ _ _ _ _ ____ _ _ _ _ __ __ _ _ ____ 77 

Krusensternian transgression ______________ ____________ 78 

Summary _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____ _ _ __ _ ____ _ __ ____ _ _ 78 

Volcanic ash deposits __ ________ _________________ _ __________ 78 

Southern Alaska -------------------------------------- 79 

Seward Peninsula ------------------------------------ 79 

Central Alaska________________________________________ 79 

Flora ---------------------------------------------------- 81 

Early to middle Pleistocene ---------------------------- 81 

Yarmouth(?) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ 83 

Illinoian __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __ 83 

Sangamon -------------------------------------------- 84 

Wisconsinan __________________ __________ ________ ______ 85 

Post-Wisconsinan______________________________________ 86 

III 
IV CONTENTS 

Page Page 

Fauna ____ _ _ __________ _ _ ____ ________ _ _ _ _ _ ___ ____ _ __ _ _ _ _ _ _ _ 88 Climate-Continued 

Invertebrates ---------------------------------------- 88 

Nonmarine mollusks ------------------------------ 88 

Terrestrial mollusks ----~--------------------- 88 

Freshwater mollusks -------------------------- 88 

Marine mollusks ---------------------------------- 90 

Insects____________________________________________ 91 

Middle Pleistocene ------------------------------------ 105 

Yarmouth(?) ------------------------------------------ 106 

Illinoian __ ____ __ _ _ _ _ _ _ ______ ______ _ _ _ _ _ _ _____________ _ 107 

Evidence from glaciated areas---------------------- 107 

Evidence from unglaciated areas __________________ 107 

Sangamon ---------------------------- --------------- 107 

VVisconsinan ------------------------------------------ 108 

Evidence from glaciated areas---------------------- 108 

Bacteria in permafrost ---------------------------- 91 

Vertebrates ____ __ ___________ _ __ _ _ __ _____________ _ _ _ _ _ 91 

Distr-ibution ___________ _____ _ _ ________________ _ ___ 92 

Stratigraphy __________ ------------- _ ___ _ ____ ____ __ 92 

Pre-Illinoian---------------------------------- 93 

Illinoian ___ _____________ ______ _ _ ___ _____ ______ 93 

VVisconsinan ---------------------------------- 95 

Distribution ------------------------------ 95 

Carcasses _ _ _ _ __ _ _ __ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 98 

llolocene ______________________________________ 101 

Extinction _ _ __ _ _ _ _ _ _ __ __ _ __ _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ 102 

Marine vertebrate and bird remains ________________ 103 

Summary ------------------------------ __________ 103 

Evidence from unglaciated areas __________________ 109 

Biogeographical evidence -------------------------- 110 

Summary _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ __ __ _ __ _ _ _ _ _ ____ __ _ _ _ _ 110 

llolocene______________________________________________ 111 

Late Cenozoic history of Alaska ---------------------------- 113 

Late Tertiary ---------------------------------------- 113 

Early Pleistocene______________________________________ 114 

Middle Pleistocene ------------------------------------ 115 

Yarmouth(?) -----------------------------------~------ 116 

Illinoian _ _ _ ____ _ _____ _ __ _ _ ___ ___________ ___ _________ _ _ 116 

Sangamon -------------------------------------------- 118 

Climate -------------------------------------------------- 103 

Evidence from glaciated areas-------------------------- 103 

Evidence from unglaciated areas ---------------------- 104 

Late Tertiary ---------------------------------------- 104 

Early Pleistocene-------------------__________________ _ 105 

VVisconsinan _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ ______ _ _ _ _ 118 

llolocene______________________________________________ 121 

References cited ------------------------------------------ 122 

Index __________________________ ---------------- ________ __ 141 

PLATE 1. 

FIGURE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

29. 

30. 

31. 

ILLUSTRATIONS 

Page 

Physiographic divisions of Alaska ___________________________________________________________________________ In pocket 

Sketch map showing Quaternary deposits of Alaska --------------------------------------------------------------- 3 

Map showing mean annual precipitation in climatic zones --------------------------------------------------------- 4 

Map showing mean annual air temperature in climatic zones ------------------------------------------------------- 5 

Photograph showing Columbia Glacier ·------------------------------------------------------------------ _________ 6 

Photograph showing 1964 earthquake-induced landslide on Sherman Glacier--------------------------------_________ 8 

Map showing extent of Quaternary glaciations in Alaska----------------------------------------------------------- 16 

Photograph showing terminal moraine of Illinoian age ----------------------------------------- ____ ______ _ _________ 20 

Cross section (east-west) across central Alaska showing past and present snowline ----------------------------------- 22 

Cross section (north-south) across central Alaska showing past and present snowline ------------------------ _________ 23 

Photograph showing terminal moraine of VVisconsinan age _________ --------------------------------------- _________ 26 

Map showing modern snowline surface ___ ______ ______ ________ ______________ ________________________ _____ _________ 29 

Map showing VVisconsinan snowline surface -------------------------------------------------------------- _________ 31 

Map showing drowned cirques ----------------------------------------------------------------------------------- 32 

Orthographic drawing of Nuka Bay _______________________________________________________________________________ 33 

Map showing sand dunes in Alaska ---------------------------------------------------------------------- _________ 35 

Map showing distribution of loess, sand dunes, and ventifacts in the Big Delta area _______________ __ _____________ ____ 36 

Map showing loess deposits of Alaska ----------------------------------------------------------------------------- 38 

Graph showing cumulative frequency grain size of loess from various,locations in Alaska ----------------------------- 39 

Diagram showing cross section of Baldwin Peninsula --------------------------------------------------------------- 41 

Diagram showing composite cross section of Quaternary deposits in central Alaska ----------------------------'------- 41 

Photograph showing wind-blown silt from Delta River flood plain --------------------------------------------------- 43 

Map showing distribution of permafrost in northern hemisphere--------------------------------------------'--------- 45 

Map showing permafrost of Alaska _ ___ _ _ _ _ ____ ______ _ _ __ ____ _ _ _ _ _______ _ __ ________ _ _______ __ _ _ __ _ __ _ ____ ____ __ ___ 46 

Graph showing geothermal profile for Cape Simpson ---------------------------------------------------------------- 47 

Graph showing hypothetical temperature-depth profile ________ ___ _ ________ _ _ ____ ____ _ _ __ __ _______ _ ___ _ ______ __ ___ _ _ 48 

Photograph showing foliated ground-ice mass (ice wedge) near Livengood --------------------- --------- ---~-------- 50 

Photograph showing ice wedge polygons near Barrow--------------------------------------------------------------- 51 

Map showing distribution of ice wedges and permafrost in Alaska ------------------~-------------------------------- 52 

Diagram showing section of frozen sediments at Eva Creek ---------------------------------------- _________________ 54 

Map showing distributio~ of ice wedge casts in Alaska ----------~---------------------------- -- -------------------- 57 

Map showing distribution of pingos in Alaska ___________________________________________ ::. ________ ---~------------- 58 
CONTENTS v 

Page 

FIGURE 32. Photograph showing altiplanation terraces cut into Indian Mountain ________________________________ ----------------- 62 

TABLE 

33. Diagram showing solifluction deposits and ice wedge casts, University of Alaska. ------------------------------------- 63 

34. Photograph showing rock glacier on Sourdough Peak ---------------------------------------------- _________________ 65 

35. Photograph showing Yukon-Koyukuk flood plain ------------------------------------------------------------------- 69 

36. Map showing lake in Copper River Basin during Wisconsinan Glaciation _____________________________________________ 72 

37. Diagram showing section of northeastern part of Copper River Basin _________________________________________________ 73 

38. Diagram showing cross section of coastal plain at Nome _____________________________________________________________ 75 

39. Photograph showing Ester Ash Bed between Ester and Cripple Creeks----------------------------------------------- 80 

40. Map showing vegetation of Alaska---------------------------------------------------------------- _________________ 82 

41. Photograph showing white spruce stump in soil and gravel _________________________________________________________ 84 

42. Mammals of late Wisconsinan time, Fairbanks _ _ __ _ _ __ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ __ __ __ ____ _ _ _ _ _ _ __ ___ _ _ _ _ _ _ _ _ _ __ _ 94 

43. Photograph showing partial mammoth carcass __ __ ____ _ _ __ __ __ _ _ _ _ _ _ _ __ _ _ _ __ __ __ _ ___ _ _ __ __ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ 98 

44. Photograph showing partial bison carcass _________________________________________________________________________ 100 

45. Graph showing ground temperature and depth in Arctic Alaska _____________________________________________________ 112 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

TABLES 

Page 

Position of the Pliocene-Pleistocene boundary_______________________________________________________________________ 12 

Correlation of local Quaternary glacial sequences in Alaska--------------------------------------------------- In pocket 

Correlation of local nonglacial sequences in Alaska ---------------------------------- _________________________ In pocket 

Rates of deposition of Holocene loess along rivers in central Alaska ------------------------------------------------- 42 

Ice wedge cast localities in Alaska ____ ____ _ _ _ _ _ _ _ _ _ __ ___ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ ____ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ ___ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ 56 

Conductivity and stratigraphy of sediments exposed at Eva Creek gold placer mining cut ----------------------------- 60 

Elevation above sea level of active solifluction lobes in Alaska------------------------------------------------------- 63 

Quaternary marine transgressions recorded on Alaskan coasts ___________________________________ --------------~----- 75 

Fossil nonmarine mollusks from the Kotzebue Sound area, northwestern Alaska ------------------------------------- 89 

Stratigraphic distribution of the more significant fossils found in marine beds of Pleistocene age in Alaska _____________ 90 

Mammal remains found in beds of pre-Wisconsinan age in Alaska--------------------------------------------------- 96 

Fossil mammals reported from perennially frozen creek-valley silt deposits of Pleistocene age in the Fairbanks 

district ----------------------------------------------------------------------------------------------------- 97 

Radiocarbon dates of Pleistocene mammals from the perennially frozen silt in the Fairbanks area _____________________ 99 

Present-day and Wisconsinan mean July temperatures of selected stations in Alaska calculated from present lapse rate 

and estimated change of snowline based on elevation of Wisconsinan cirque floors _________________________________ 109 

QUATERNARY GEOLOGY 

OF ALASKA 

By TROY L. Ptwt 

ABSTRACT 

The earliest account of the geology of an Alaskan area was concerned largely with Quaternary deposits. Otto von Kotzebue in 1816 

examined the famous bone-bearing frozen silt and mysterious masses 

of ground ice at a place now called Elephant Point in western Alaska. 

Alaska has long intrigued Pleistocene geologists, not only because of 

its interesting, and in places remarkably complete, stratigraphic record of Pleistocene events, but also because spectacular effects of the 

cold-climate geomorphic processes are well recorded there. 

If colluvium is included, Quaternary deposits mantle virtually all of 

Alaska. Glacial deposits are widespread in southern Alaska and on 

the north and south sides of the Brooks Range. Eolian sediments are 

widespread in the interior and western part of the State as well as in 

the far north. Lacustrine sediments of middle and late Pleistocene age 

are exposed in the Copper River Basin and elsewhere, and fluvial 

deposits are extensive in major valleys and large tectonic basins. 

Glaciers have covered about 50 percent of the present area of Alaska 

at one time or another, but large areas in central and northern Alaska 

have never been glaciated. The extents of late Tertiary and early 

Pleistocene glacial advances remain almost unknown, but those of 

middle and late Pleistocene and Holocene advances are well established. In lllinoian, Wisconsinan, and Holocene times, glaciers were 

much more extensive in southern Alaska than in northern Alaska and 

much more extensive on the south flanks than on the north flanks of 

individual mountain ranges, indicating that glaciers were nourished 

chiefly by air masses moving northward or northeastward from the 

northern Pacific Ocean. 

D. J. Miller's pioneering work and the subsequent work of others in 

southern Alaska indicate that glaciation in Alaska started by at least 

late Miocene time and perhaps early middle Miocene time. Glacial 

deposits of Illinoian age were not commonly recognized prior to 1945, 

but field and photogeologic studies since then have shown that drift of 

Illinoian age is present in nearly every glaciated area in Alaska. Drift 

of Wisconsinan age is found in nearly all the mountainous areas of 

Alaska. Areas south of the crest of the Alaska Range and the Alaska 

Peninsula were almost completely inundated by ice, and icecap conditions prevailed over large areas. The Wisconsinan glacial cycle in 

Alaska was clearly a complex event consisting of at least two major 

glacial advances. 

Loess probably is the most widely distributed sediment of Quaternary age in Alaska. It forms a blanket, ranging in thickness from a 

few millimetres to more than 60 m, that covers almost all areas lying 

below altitudes of300-450 m. Thick deposits of loess are most widely 

distributed in central and western Alaska. Most of the loess was 

deposited during Illinoian and Wisconsinan time, but windblown silt 

is still being deposit~d in many areas, particularly along most braided 

streams in Alaska; measurements indicate an accumulation of 

0.2-2.0 mm per year at present. 

Extensive areas of Alaska are underlain by deposits that are the 

result of mass wasting or frost action in a rigorous climate--a climate 

widely known as periglacial. A widespread and unique phenomenon 

of this climate is permafrost, or perennially frozen ground, which is 

present throughout 82 percent of Alaska. The greatest known thickness is 650 mat Prudhoe Bay. 

It is estimated that 10 percent of Alaska is covered by fluvial 

deposits, excluding the overlying loess blanket on the terraces. Many 

large tectonic basins such as the valleys of the Kuskokwim and 

Tanana Rivers, the Yukon Flats, and Yukon-Koyukuk lowland are 

filled with 1 to a few hundred metres of Quaternary fluvial sediments. 

Known lacustrine deposits are relatively limited in Alaska, and only 

one large area, the Copper River Basin, exhibits widespread, welldeveloped lake deposits. Alaskan marine deposits of Quaternary age 

now above sea level are limited to a narrow strip of land along the 

present coast, except in northern Alaska and perhaps in the YukonKuskokwim Delta area where they are more extensive. 

Volcanic ash deposits are widespread and abundant in Quaternary 

sediments throughout southern Alaska, from the far west in the 

Aleutian Islands to southeastern Alaska. These ash layers have great 

potential for resolving problems of Quaternary geology, archaeology, 

paleopedology, and palynology. 

The distribution of vegetation in Alaska is divided phytogeographically into two large areas, the glaciated and unglaciated regions. The 

glaciated areas have a floral history of repopulation by either tundra 

or forest during the past 1,000 to tens of thousands of years. The 

unglaciated areas constitute 50 percent of the State and represent 

refugia for plant and animal life during glacial maximums. In Wisconsinan time, the pollen record indicates that an Arctic herbaceous 

tundra was present on Seward Peninsula; forest was essentially absent from the interior of Alaska until the end of Wisconsinan time. 

The tree line was 500-600 m lower near Fairbanks at that time. 

A rich Quaternary fauna is present in Alaska, but only in the study 

of marine invertebrates and terrestrial vertebrates has a serious 

beginning been made. During the two decades since detailed studies of 

Quaternary stratigraphy began in Alaska, a modest but growing 

number of vertebrate fossils have been found in significant stratigraphic context; most are from the Fairbanks area. Canis, Rangifer, 

Mammuthus, Bison, Cerous, Ochotona, Lemmus, Microtus, Equus, 

andPliomys are now known from sediments ofpre-lllinoian age. The 

list of documented finds of mammal remains of lllinoian age is slowly 

growing, and it is evident that many taxa were present in North 

America earlier than is generally recognized. It is now known, for 

example, that Rangifer, Ouibos, Alces, Saiga, Pliomys, Bootherium, 

Symhos, andDicrostonyx, as well asBison, Mammuthus, andEquus, 

were in North America prior to Wisconsinan time. 

Many mammals became extinct in Alaska at the end of Pleistocene 

time, and most of the species were grazers. It is thought that the loss of 

grassy habitat alone did not cause the extinction of the grazers at this 

time; rather, the restriction of ideal habitat plus additional stress in 

the form of man probably caused the demise of these species. 

Climatic fluctuations during Quaternary time in Alaska were responsible for the formation and disappearance of glaciers and permafrost and changes in distribution of plants and animals. Extensive 

glacial advances during lllinoian time indicate a long duration of a 

1 
2 QUATERNARY GEOLOGY OF ALASKA 

colder or wetter climate than now. The growth of ice wedges in central 

Alaska indicates a rigorous periglacial climate with a mean annual 

air temperature of at least -7° to -8°C, which is about 2°-4°C colder 

than the present. In Wisconsinan time precipitation probably did not 

increase markedly, but rather, mean summer temperatures decreased, and summer cloudiness increased. According to the calculated position of the past snowline, the mean July air temperature in 

Nome and Kotzebue during Wisconsinan time was 1.9°-2.1oC colder 

than today. Fairbanks and Northway were a minimum of 4°C and 

4.8°C colder, with mean July Wisconsinan air temperatures of 11.5° 

and 9.9°C, respectively. 

Frozen mammal carcasses found in Wisconsinan sediments support 

the concept that permafrost has existed from the time of their death 

until now, indicating that the mean annual air temperature has been 

colder than about -1 oc since their death, except perhaps for short 

periods of time. 

It is believed that in much of Alaska the climate of Wisconsinan 

time gradually warmed to a postglacial thermal maximum between 

3,500 and 7,500 years ago. However, in central and western Alaska 

there is good evidence for a warm period beginning 10,000 years ago. 

It is as yet unclear whether evidence from the north slope represents 

the early postglacial warm period or the conventional thermal maximum. Glacial retreats and thermal records from permafrost indicate 

a warming during the last 100 years. 

INTRODUCTION 

It has been accurately said that the environment of 

the Pleistocene Epoch that formerly existed in temperate climes still exists in Alaska. Volcanic, marine, 

fluvial, lacustrine, glacial, and eolian deposits of 

Quaternary age are widespread in Alaska and are being 

formed today, many under periglacial conditions. Both 

glacial and nonglacial marine sediments are accumulating along the extensive coast, and volcanic 

eruptions are common in the southwestern part of the 

state. Glaciers are widespread. Dust is blown from active valley trains and outwash fans to be deposited as 

loess over adjacent terrain (fig. 1). Geologic processes, 

such as solifluction, frost action, and formation of permafrost, common in cold regions under periglacial conditions, are active in most parts of the State. 

This paper summarizes resultH of studies in many 

areas of Quaternary geology. It is hoped that this account will lead to a better understanding of the Pleistocene and Holocene Epochs in Alaska and will also be a 

useful resume of the progress of investigations in 

Quaternary geology in this important section of North 

America. A serious attempt has been made to point out 

current areas of disagreement, unsolved problems, and 

fertile areas for future research. · 

The following discussion is arranged according to the 

age of the deposits or events, insofar as information on 

age is available. Where the age data are too scanty, the 

presentation is ordered on the basis of the character and 

distribution of the deposits and landforms. This report 

was written between 1960 and 1972, and no studies 

published after 1972 are included, unless unpublished 

versions were available earlier. 

GEOGRAPHY 

LOCATION AND EXTENT OF AREA 

Alaska is part of the largest peninsula of North 

America and extends 'from long 130°W to 173°E and 

from lat 52° to 72° N. (pl. 1). It is bounded on the north by 

the Arctic Ocean, on the south by the Pacific Ocean, on 

the east by Canada, and on the west by the Bering Sea, 

Bering Strait, and Chukchi Sea. 

The area of Alaska is 1,520,000 km2 , about 20 percent 

of the area of the 48 contiguous United States. The state 

contains extensive lowlands and towering glacier-clad 

mountains, including Mount McKinley, 6,660 min elevation, the highest peak in North America. 

PHYSIOGRAPHY 

The main physiographic provinces of Alaska are outlined by major topographic units and are similar to 

those of the western United States and Canada. The 

four major provinces, which were outlined by Brooks 

(1906) and were used in the most recent description of 

the physiographic divisions of Alaska (Wahrhaftig, 

1965), are from south to north the Pacific Mountain 

System, the Intermontane Plateaus, the Rocky Mountain System, and the Arctic Coastal Plain (pl. 1). The 

Pacific Mountain System extends in an arc from southeastern to south-central Alaska and includes to the west 

the Alaska Peninsula and the Aleutian Islands. It contains the coastal mountains, Alaska Range, Wrangell 

Mountains, Talkeetna Mountains, Aleutian Range, and 

intervening lowlands. The Intermontane Plateaus include the lowlands and rolling hills of interior and western Alaska between the Alaska Range on the south and 

the Brooks Range on the north and also the Bering 

platform. The Brooks Range constitutes the Rocky 

Mountian System. The Arctic Coastal Plain extends 

north from the Rocky Mountain System to the sea. 

These major divisions have been subdivided into 12 

provinces and further subdivided into 60 sections by 

Wahrhaftig (1965) (pl. 1). 

CLI~1ATE 

As might be expected, the climate of Alaska varies 

greatly; in fact, its range is greater than that between 

Florida and Maine 'in the conterminous United States. 

This is caused by a varied topography, different conditions of the seas bounding Alaska on three sides, and its 

great geographical extent. The northernmost point of 

Alaska is within 18° of the latitude of the North Pole, 

and the southernmost tip of southeastern Alaska is near 

the latitude of Copenhagen, Denmark. 

Several distinct climatic zones have been recognized 

in Alaska, and the early climatic subdivisions (Abbe, 
620 

580 

54° 

172° 180° 

USSR 

., ., 

., /" Qg 

/~Qu St Lawrence I ~ 

\. 

BERING SEA 

Aleutian Islands 

~&\. Qg ~. , . ., 

172° 

• 

Pribilof Islands 

Umnakl '. ~ U 

~ 

.. fo"Qg ~r~ 

164° 

172° 

I 

164° 156° 148° 140° 132° 124° 

66° 

0 100 200 300 MILES 

0 100 200 300 KILOMETRES 

62° 

CANADA 

58° 

6JcD PACIFIC OCEAN 

156° 148° 140° 132° 

FIGURE 1.- Sketch map of major regional groups of surficial deposits in Alaska. Qg, glacial and other deposits associated with heavily glaciated alpine mountains; Qgl, 

glaciolacustrine deposits of larger Pleistocene proglacial lakes; Qu, undifferentiated deposits associated with generally unglaciated uplands and lowlands of the Interior 

and North Slope; Qa, fluvial deposits; Qe, eolian deposits; Qc, coastal deposits of interbedded marine and terrestial sediments. Solid black areas are deposits associated 

with volcanic peaks and flows of Tertiary and Quaternary age. Modified from Karlstrom (1960b, fig. 154.1). 

-

z 

~ 

~ 

0 

t::J 

~ 

Q 

~ 

-

0 

z 

w 
4 QUATERNARY GEOLOGY OF ALASKA 

1906, p. 140--141) differ only slightly from the four used 

today by the U.S. Weather Bureau (fig. 2) (Watson, 

1959, p. 24). The southernmost climatic zone, a zone of 

dominant maritime influence, includes southeastern 

Alaska, the south-central coast, the southeastern coast 

of the Alaska Peninsula, Kodiak Island, and the Aleutian Islands (fig. 2). This area is characterized by small 

temperature variations, high cloudiness, and abundant 

precipitation, especially in southeastern Alaska. The 

highest recorded mean annual precipitation, 560 em, is 

at Little Port Walter in southeastern Alaska. This zone 

has no permafrost but contains extensive glaciers. 

A zone of transition from maritime to continental 

climate lies north of the maritime zone (fig. 2). This zone 

includes the Wrangell Mountains and extends to the 

west, widening to include the C~ok Inlet area, the 

8 

southern Alaska Range, the Yukon-Kuskokwim Delta, 

and the southern half of the Seward Peninsula. Temperature variations in this zone are more pronounced, 

and there is less cloudiness and precipitation than in 

the maritime zone. The mean annual air temperature is 

colder that ooc (fig. 3), and permafrost is common in this 

zone. 

The dominant continental climate zone lies north of 

the Alaska Range, south of the Brooks Range, and east 

of the Seward Peninsula (pl. 1). These topographic barriers and remoteness from the closest open ocean areas 

tend to prevent the inland movement of moist maritime 

air masses; the area is semiarid. This zone has great 

extremes of temperature, from 37 .soc to -60°C. The 

mean annual air temperature ranges from -4°C to 

-soc (fig. 3), and permafrost is widespread. 

PACIFIC OCEAN 

EXPLANATION 

---30---

Isohyet 

Line of equal average annual 

precipitation. Interval 

variable, generally 10, 

50, or 100 em 

0 150 300 MILES 

0 150 300 KILOMETRES 

FIGURE 2.-Mean annual precipitation (centimetres) in climatic zones. A, Arctic; B, Continental; C, Maritime-Continental Transition; D, 

Maritime. Modified from Watson (1959, p. 19). 
HISTORY OF RESEARCH 5 

In the zone of Arctic climate, in northern and northwestern Alaska including the north half of the Seward 

Peninsula (fig. 2), mean annual air temperature ranges 

from -4°C to -l2°C, and precipitation is slight (1{}.-30 

em annually). Permafrost is present almost everywhere. 

ACKNOWLEDGMENTS 

The writer wishes to express deep appreciation to D. 

M. Hopkins, who assisted with the organization of the 

report and reviewed the manuscript. Others who reviewed and made valuable suggestions and contributions to the sections dealing with their specialties are 

Jerry Brown, R. L. Detterman, 0. J . Ferrians, Jr., A. H. 

Lachenbruch, D. S. McCulloch, M. F. Meier, D. R. 

Nichols, George Plafker, A. S. Post, C. E. Ray, C. A. 

I 

/ 

Repenning, P. V. Sellmann, Dwight Taylor, F. R. 

Weber, and J. R. Williams. Their help is greatly appreciated. L. R. Mayo and R. D. Reger assisted in the 

compilation of many of the illustrations and tables and 

in the preparation of the manuscript. 

HISTORY OF RESEARCH 

The earliest account (Kotzebue; 1821) of the geology 

of an Alaskan area was concerned largely with Quaternary deposits. Kotzebue's report contains an account of 

the famous bone-bearing frozen silt and of mysterious 

masses of buried ice at a place now called Elephant 

Point on Eschscholtz Bay, about 35 km south of the 

Arctic Circle. Accounts of exploration in Alaska during 

the latter part of the 19th century and the many accounts of the regional geology published by the GeologiP A C I FIC OCE AN 

EXPLANATION ----2---

Isotherm 

Line of equal mean annual air 

temperature. Interval, 2° C 

0 150 300 Ml LES 

0 150 300KILOMETAES 

~ 174 °. ~~8° 17.8• 17 4° 

f.. East of Greenwich · I. West of Green wi ch \ 

~1 1--- I i 

1 52._-J___ ALEU~~~,! - .-.... "1""' .1 .. ISLANDS r)=:::::o<" C: I [ I !··~~ ,;'fzmr~T-"J 

FIGURE 3.-Mean annual air temperature (degrees Centigrade) from Pewe (1966b, fig. 4; effect of topography not considered). Climatic 

zones: A, Arctic; B, Continental; C, Maritime-Continental Transitional; D, Maritime. Modified from Watson (1959, p. 24). 
6 QUATERNARY GEOLOGY OF ALASKA 

cal Survey from 1898 through 1940 almost invariably 

contain descriptions of the physiography and of the 

Quaternary sediments as well as descriptions of the 

bedrock geology. Brooks (1906) wrote the earliest comprehensive account of Alaska Quaternary geology. 

GLACIOLOGY 

The magnificent and spectacularly fluctuating 

glaciers of southern Alaska (fig. 4) began to receive 

attention in the latter half of the 19th century, through 

the work of Muir (1884), Reid (1892, 1896), and Russell 

FIGURE 4.-0blique aerial view of Columbia Glacier entering Prince William Sound, south-central Alaska. View to the north with 

Chugach Range in the background. The highest peak is Mount Witherspoon, 3,644 m in elevation. Columbia Glacier has an area of 

960 km2 . Photograph by Austin S. Post, U.S. Geological Survey, August 25 , 1965. 
HISTORY OF RESEARCH 7 

(1892a, 1892b, 1893). Coastal Alaska's great glaciers 

have always been of interest to Pleistocene geologists 

and have been under close observation since the 1890's 

(Russell, 1892a; Reid, 1896; Gilbert, 1910). Tarr and 

Martin (1914) summarized their systematic observations, and Grant and Higgins (1913) carefully observed 

the glacier termini in Prince William Sound and Kenai 

Peninsula. Continuing studies between 1920 and 1950 

(Cooper, 1937; 1939; Field, 1932a, 1932b, 1941, 1942, 

1947, 1950; Wentworth and Ray, 1936) led ultimately to 

coordinated glaciological and glacial geological studies 

of the Malaspina-Seward ice field system (Sharp, 1951a, 

1951b, 1956, 1957) and of the Juneau ice field (Miller, 

1952, 1953, 1970; Field and Miller, 1950, 1951; Hubley, 

1955. 1957; Thiel and others, 1957; Heusser and Marcus, 1964). The glaciers of interior Alaska received less 

intense scrutiny for many years, although the spectacular advance of Black Rapids Glacier in 1937 (Hance, 

1937; Moffit, 1942; Geist and Pewe, lt157) and Muldrow 

Glacier (Pewe, 1957a; Post, 1960) indicated that interesting problems awaited study. Only recently, with 

the growth of the study of glacier surges (Meier, 1969; 

Post, 1969; Meier and Post, 1969). has it been understood that Black Rapids Glacier and Muldrow Glacier 

advances were the vanguard of documented glacial 

surges. 

Systematic glaciological and glacial geological 

studies in the Alaska Range and in the Brooks Range 

did not begin until the In tern a tiona l Geophysical Year 

in 1957, with the studies of Pewe and his associates in 

the Alaska Range, mainly on Gulkana Glacier, (Pewe, 

·1957a, 1957b, 1961a, 1961b, 1963; Sellmann, 1962; 

Moores, 1962; Mayo and Pewe, 1963; Mayo, 1963; 

Rege~ 1964, 1968; Ragan, 1964, 1966, 1967, 1969;Ru~ 

ter, 1965; Ostehso and others, 1965; Reger and Pewe, 

unpub. data, 1963) and of R. C. Hubley, G. W. Holmes, 

and E. G. Sable in the Brooks Range (Keeler, 1958; 

Sater, 1959; Holmes and Lewis, 1961; Sable, 1961) . 

Also, pioneer glaciological studies in the Wrangell 

Mountains were published (Benson, 1968). The U.S. 

Geological Survey now has a long-range detailed program of glacier studies on Gulkana Glacier in the 

Alaska Range and on Wolverine Glacier on the Kenai 

Peninsula (Meier and others, 197 n. 

The Alaska earthquake of March 27, 1964, provided 

an unequaled opportunity to examine the effect of an 

earthquake on glaciers, because the epicenter was in 

Prince William Sound, an area bordered by hundreds of 

glaciers. Many observations and studies were made of 

glaciers and of avalanches on glaciers during the first 

days and months after the quake (Bull and Marangunic, 

1968; Field, 1965, 1968; Field and others, 1964; Hackman, 1965; La Chapelle, 1968; Marangunic and Bull, 

1968; Marcus, 1968; Miller, 1965a, b; Pewe, 1964a, b, 

1968b; Plafker, 1968; Post, 1967; Ragle and others, 

1965a, b; Reid, 1968; Sater, 1964; Shreve, 1966, 1968; 

Tuthill, 1966; Tuthill and others, 1968). 

As a result of the 1899 earthquake in southern 

Alaska and a study of glacier advances there, Tarr and 

Martin (1914) discussed the ideas that earthquakes 

caused glaciers to advance either immediately or at a 

later date as a result of great quantities of snow on 

mountainsides being shaken loose and cascading down 

on the glaciers below. After the 1964 quake observations from the air of hundreds of glaciers revealed no 

advancing ice streams as the result of the earthquake. It 

will take some time, however, to determine whether the 

glaciers will expand as the result of snow avalanched 

down onto the ice. Observations indicate that most of 

the snow knocked down would have fallen later in the 

spring under ordinary circumstances. Spectacular debris avalanches (fig. 5) on glaciers did occur, and studies 

are underway to evaluate the effect of the debris on 

glacier regimen (Bull, 1969). 

GLACIAL STRATIGRAPHY 

Aside from attempts to date Holocene fluctuations of 

the coastal glaciers, studies of glacial stratigraphy were 

for many years quite desultory. To be sure, most Geological Survey reports took note of the distribution of 

moraines and glaciated terrain; Capps particularly concerned himself with the possibility that more than one 

glacial cycle was represented in Alaska and summarized (1931) the existing knowledge of the glacial 

history of Alaska. Most of the recognized glaciated 

areas rather clearly dated from the glaciation of Wisconsinan age (Capps, 1915b), and older glacial deposits 

were commonly overlooked; however, Capps (1916b) 

discovered deformed deposits of apparent glacial origin 

and of probably early Pleistocene age in the White River 

area on the north and east flanks of the Wrangell Mountains (Capps, 1910b, 1915a), and Taliaferro (1932) discovered marine tillites of late Tertiary and possible 

Pleistocene age along the Gulf of Alaska; these were 

·. studied in more detail by Miller (1953a, 1957). Shortly 

• after World War II, intensive studies of glacial stratig-

. raphy were begun in many parts of Alaska and resulted 

in a brief publicatio-n by Pewe and others (1953). Several notable papers on individual areas include those by 

Wahrhaftig (1958), Detterman and others (1958), Miller and Dobrovolny (1959), Fernald (1960), Hopkins and 

others (1960), Holmes and Lewis (1961), Coulter and 

Coulter (1961, 1962), Pewe and Holmes (1964), and 

Karlstrom (1964). These and other works were summarized by the Alaska Glacial Map Committee of the 

U.S. Geological Survey in a map showing the extent of 

glaciations in Alaska (Coulter and others, 1965). 

Pewe, Hopkins, and Giddings (1965) summarized 
8 QUATERNARY GEOLOGY OF ALASKA 

various events, and Pewe, Ferrians, Nichols, and Karlstrom (1965) presented detailed information on 

Quaternary geology in central Alaska. Detailed work 

on glacial deposits of the Brooks Range was only recently undertaken (Fernald, 1964; Porter, 1964, 1966; 

Holmes and Lewis, 1965; Hamilton, 1969; Reed, 1968). 

The following glacial mapping elsewhere in Alaska 

adds a fuller understanding of the glacial history of the 

State: The upper Tanana valley (Fernald, 1965a), York 

Mountains (Sainsbury, 1967a), Chagvan Bay area in 

southwest Alaska (Porter, 1967), the Johnson River 

area of the Alaska Range (Holmes and Foster, 1968), 

and the Ray Mountains (Yeend, 1971). The chronology 

of the late Holocene in Alaska was well summarized by 

Porter and Denton (1967). Rampton (1970) reported 

recent glacial changes near the Alaska-Canada line. 

FIGURE 5.-Earthquake-induced landslide of 1964 on Sherman Glacier, south-central Alaska; 107m3 of slide debris covers 8 km2 of ablation 

zone. Glacier regimen changed from negative to strongly positive (Marangunic and Bull, 1968). Photograph by Austin S. Post, U.S. 

Geological Survey, 1965. 
HISTORY OF RESEARCH 9 

Glacial mapping is being continued on the south flank 

of the Brooks Range by T. D. Hamilton and his associates at the University of Alaska. Denton and others 

are unravelling the interbedded volcanic and glacial 

deposits in the Wrangell Mountains with the aid of 

potassium-argon dating (Denton and Armstrong, 1969; 

Stui ver and others, 1969). The great challenge of glacial 

geology today in Alaska is to relate the glacial record to 

the volcanic deposits by radiometric dating and 

paleomagnetic observations. Alaska abounds with 

areas in which these methods can be employed. 

NONGLACIAL DEPOSITS 

The stratigraphy and paleontology of the richly fossiliferous silts ofnonglaciated areas of Alaska continue 

to arouse interest that began with the earliest studies 

by the Kotzebue and Beechey expedition. In 1907 and 

1908, Quackenbush (1909) revisited and reexcavated 

the historic bluff at Elephant Point. Eakin (1916; 1918) 

and Mertie (1937) gave extended accounts of silt deposits in central Alaska. Taber (1943) presented an 

even more elaborate account of the stratigraphy of silts 

near Fairbanks that he considered to be the result of 

long-continued frost-riving of bedrock; however, Tuck 

(1940) had shown that these deposits were actually 

loess, and Pewe (1955) confirmed this conclusion and 

also demonstrated a long and complex late Pleistocene 

history in the Fairbanks area. The University of Alaska 

in cooperation with the American Museum of Natural 

History has collected vertebrate remains from the 

placer pits near Fairbanks, and in other parts of Alaska 

through the efforts of Geist (1953), an enormous quantity of vertebrate material has been accumulated 

(Frick, 1930, 1933, 1937) of which only the bison have 

been systematically described (Skinner and Kaisen, 

1947). Guthrie and his associates at the University of 

Alaska initiated a new era of study of Pleistocene vertebrates in Alaska, especially a study of the great collection from the Fairbanks area (Guthrie, 1966a, b, c; 

1967; 1968a, b; 1972). The Quaternary geology of unglaciated central Alaska has been under study by Pewe 

(1952a; 1958a, b; 1965a, b; 1970a, b; 1975). 

Understanding of the climatic history recorded in the 

nonglacial deposits has been deepened greatly by 

palynological studies conducted during the last two 

decades by many investigators, most notably by Heusser (1960, 1966), Livingstone (1955, 1957), Colinvaux 

(1962, 1963, 1964a, b; 1967a, b, c), and Matthews 

(1968a, 1970). 

ARCHAEOLOGY 

The latest events of Quaternary time involve the coming of man. In addition to enlarging our knowledge 

concerning the record of man, archaeological studies in 

Alaska have contributed greatly to our understanding 

of sedimentation, climatic and vegetation changes, and 

stratigraphy of nonglacial deposits of the last 

8,00~10,000 years. A summary of the archaeology of 

Alaska is beyond the scope of this report, but a brief 

review of such research is presented because it concerns 

the Quaternary record. 

Alaska is almost surely the route by which the first 

humans came to North America, but until the recent 

discoveries of Giddings (1962), no undisputed occupation sites or artifacts older than 6,000 years had been 

found there. Until the early 1940's, in fact, the only 

known archaeological sites aside from the Campus site 

(Rainey, 1939) were those occupied within the last few 

centuries by Eskimos. The discovery of the lpiutak site 

at Point Hope, occupied about 2,000 years ago, marked a 

tremendous advance in our understanding of Eskimo 

prehistory (Larsen and Rainey, 1948). The reports of 

Geist and Rainey (1936) and Collins (1937) on St. Lawrence Island presented a nearly complete understanding of the last 2,000 or 3,000 years of Eskimo history 

there. More recently, the discovery of the Denbigh Flint 

complex at lyatayet, on Norton Sound (Giddings, 1951, 

1964, 1967; Hopkins and Giddings, 1953), and of 

6,000-year-old artifacts in the Trail Creek caves on 

Seward Peninsula (Larsen, 1951, 1953, 1968) indicated 

that the Eskimo has had a long history in Alaska. Research on Anangula Island in the Aleutian Islands produced insight into about 8,000 years or more of AleutEskimo history there (Laughlin, 1963). Radiocarbon 

dates of 8,000 and 8,500 years are reported, but Black 

and Laughlin (1964) believed the age may be more 

easily 12,000 years. In more recent years, many workers have found sites comparable in antiquity to the 

Denbigh Flint complex in other parts of northern and 

western Alaska (Campbell, 1962; Hadleigh-West, 

1963). The present knowledge of Eskimo archaeology is 

ably summarized by Giddings (1960) and more recently 

by Dumond (1965). Shortly before his death, Giddings 

compiled a succinct summary of archaeology in Alaska 

in (Pewe, Hopkins, and Giddings, 1965). 

The record of man in Alaska is constantly being 

pushed back in time, and latest views involve one of the 

oldest known sites and one of the newest. Discovered in 

1933 on the campus of the University of Alaska (Rainey, 

1939, 1941), the Campus site, with its typologically old 

artifacts with Old World relations is of major importance. Clear stratigraphy and dating are missing. Recently, Hadleigh-West (1967) described artifacts from 

the Donnelly Ridge site on a moraine of Wisconsinan 

age (Pewe and Holmes, 1964) 120 km southwest of the 

University of Alaska. He believed that the artifacts in 

the Donnelly Ridge site have many affinities with the 

Campus site artifacts. Because of affinities of the ar-
10 QUATERNARY GEOLOGY OF ALASKA 

tifacts of both sites with Asian finds 10,000-15,000 

years old, Hadleigh-West believed the Alaskan artifacts fall into this range of time. 

There is no geologic reason to believe the Campus site 

cannot be this old, or older. The Donnelly Ridge site may 

perhaps be this old but not more, because the Donnelly 

moraine is not more than 15,000 years old. Recent discoveries by McKennan and Cook (1968) at Healy Lake 

150 km southwest of Fairbanks show cultural layers 

older than 11,000 years, and materials similar to the 

Campus site seem to occur in a level dated at 8,960 years 

old (Hosley, 1969). 

After more than 20 years of patient searching, which 

revealed outstanding finds, J. L. Giddings discovered in 

1961 ((what is undoubtedly the most important archeological site ever found in the Arctic" (Collins, 1967). 

This was the Onion Portage site on the Kobuk River (pl. 

1; Giddings, 1962, 1967; Anderson, 1968, 1970), a 

clearly stratified site of silt and sand of eolian and 

fluvial origin that is as much as 6 m thick and contains 

many occupational levels. The oldest dated level is 

8,500 years old, and the record may go back 6,500 years 

more, making it the oldest site in Alaska as well as the 

one with the longest continual record. , 

With a growing body of evidence that man was present in North America at least as early as 25,000-30,000 

years ago or more, it is imperative to search further for 

man in Alaska in deposits of late Quaternary age. 

MARINE DEPOSITS 

Pleistocene and Holocene marine deposits are found 

in many areas on the coasts of Alaska and were recorded 

(though erroneously assigned to the Miocene Epoch) 

early in the history of exploration of Alaska by Dall and 

Harris (1892). The most comprehensive accounts of the 

Pleistocene marine mollusks are those of MacNeil and 

others (1943) and MacNeil (1957); Black (1964) and 

O'Sullivan (1961) studied the stratigraphy of the Pleistocene marine Gubik Formation of the Arctic Slope; 

Hopkins devoted much attention to the Pleistocene sequence at Nome (Hopkins and others, 1960); and Miller 

(1953b) presented the most complete account of the late 

Cenozoic marine deposits along the Gulf of Alaska 

coast. Twenhofel (1952) described the deposits of the 

postglacial marine transgressions in southeastern 

Alaska. Present knowledge of the stratigraphy and age 

of Quaternary marine deposits in Alaska is summarized 

by Hopkins (1965, 1967b), and correlation with marine 

deposits in the U.S.S.R. across Bering Strait has been 

presented (Hopkins and others, 1965). McCulloch 

(1967; see also MeCulloch and others, 1965) studied 

marine Pleistocene deposits along the northwest coast 

as far south as Seward Peninsula, with special emphasis on the Kotzebue Sound area. 

PERIGLACIAL STUDIES 

Alaska has intrigued Pleistocene geologists not only 

because of its interesting, and in places remarkably 

complete, stratigraphic record of Pleistocene events, 

but also because the spectacular effects of cold climate 

geomorphic processes are well recorded there. Many of 

the early Geological Survey Bulletins on Alaska contain discussions of the surface features resulting from 

solifluction and intense frost action. Eakin (1916) and 

Cairnes (1912a, b) called attention to the unique aspects 

of the landscape cycle in regions where frost action is 

intense. Porsild (1938) described ice laccoliths in tundra 

regions of Alaska and christened them pingos. More 

recently, pingos were discovered and dated in central 

Alaska (Krinsley, 1965; Holmes and others, 1966, 

1968). Sharp (1941, 1942) described microrelief features 

in the WolfCreek Range just east ofthe Alaskan border 

in Canada. During the late 1940's and early 1950's 

interest quickened in frost features and the resulting 

landscape. Hopkins and Sigafoos (Hopkins and 

Sigafoos, 1951, 1954; Sigafoos and Hopkins, 1952) wrote 

a series of papers dealing with the interrelations of frost 

action and vegetation. Wallace (1948), Hopkins (1949), 

Anderson and Hussey (1963), and Black (1969b) described the origin and development of thaw lakes. Black 

and Barksdale (1949), Livingstone (1954), Carson and 

Hussey (1959, 1960a, b, 1962, 1963), and Black (1969b) 

offered explanations for the pronounced orientation 

shown by thaw lakes in many parts of Alaska. Capps 

(1910a) coined the word ((rock glacier'' for glacierlike 

tongues of rock debris that are common in mountainous 

areas in Alaska; Wahrhaftig and Cox (1959) thoroughly 

described rock glaciers, the mechanisms by which they 

move, and the climatic conditions that control their 

distribution. 

Most writers discussing frost action and the development of periglacial landscapes have been concerned 

with tundra landscapes, but Drury (1956) wrote an interesting and widely quoted aecount of the geomorphic 

and vegetational processes involved in the development 

of ((bog flats," a conspicuous variety of muskeg that is 

widespread on gently sloping surfaces in the forested 

region of central Alaska. 

Leffingwell gave the first description of ice wedge 

polygons in Alaska and the first correct explanation of 

their origin in 1915. Taber (1943) contributed greatly to 

our understanding of frost heaving and the origin of 

small lenses of ground ice, but his explanation for the 

origin of ice wedges is no longer accepted by most workers. The investigations of Black (1951b, 1952a, 1969a), 

Pewe (1952a, 1958a, 1962, 1966b, 1973, 1974a, b, 1975), 

Lachenbruch (1960a, b, 1961, 1962, 1966), and Brown 

(1967a) considered the structure, petrography, stratigraphy, and thermal environment of ice wedges. Their 
THE PLIOCENE-PLEISTOCENE BOUNDARY 11 

distribution and climatic significance were noted by 

Pewe (1964c, 1966a). 

Dissemination of information on the periglacial features in Alaska was stimulated by the field conference 

and symposium held in central Alaska in 1965 (Pewe, 

Ferrians, Nichols, and Karlstrom, 1965). 

Among the least known, but most widespread, periglacial features in the world are altiplanation terraces. 

Study of the origin, age, and distribution of these features in central Alaska has begun (Pewe and Reger, 

unpub. data 1969; Pewe, 1969b, 1970b; Reger and Pewe, 

unpub. data 197 4). 

VOLCANIC ACTIVITY 

The presence of active volcanoes in the Aleutian Islands and on the Alaska Peninsula was known tQ the 

earliest explorers of Alaska. An eruption on Bogoslof, a 

minute volcanic island north of the Aleutian chain, was 

described by Dall (1884, 1885). The cataclysmic, 

caldera-forming eruption of Mount Katmai and theresulting deposits were described in detail by Griggs 

(1922, and several later publications) and Fenner (1920, 

1923, and many later publications). The discovery of 

Aniakchak caldera by Smith (1925) indicated tha~ caldera-forming eruptions took place elsewhere in theregion. An eruption at a small cone in Okmok caldera 

near the military post at Fort Glenn, Umnak Island, in 

1945 and an eruption of Mount Cleveland on 

Chuginadak Island in 1944 demonstrated potential 

threat of the volcanoes in the Aleutian chain to human 

activities and resulted in a coordinated study by the 

Geological Survey of the geology of the entire region 

during the late 1940's and early 1950's (U.S. Geological 

Survey, 1955-61). 

Basaltic lava plateaus that occupy large areas in central and western Alaska constitute a separate and different sort of volcanic province from the andesitic volcanoes of southern and southwestern Alaska. Barth 

(1956) and Hopkins (in Cox and others, 1966) prepared 

detailed descriptions of basaltic volcanic rocks on the 

Pribilof Islands, and Hopkins (1963) on central Seward 

Peninsula. Geologic mapping, paleomagnetic stratigraphy, and potassium-argon dating were used in a 

thorough study to determine the time and volume relations of tholeiitic and alkalic basalt on N uni vak Island 

(pl.1) (Hoare and others, 1968). A summary of the distribution and importance of volcanic ash deposits is 

included in the present report, but no summary is attempted of the Quaternary volcanoes and flows. 

PALEOMAGNETIC STUDIES 

Quaternary paleomagnetic stratigraphy in Alaska is 

in its infancy, but significant contributions have already been made. The first confirmation of the Olduvai 

normal polarity event was made in a study of basalt 

flows on St. Paul Island (Cox and others, 1966), and the 

Nunivak normal polarity event was established on the 

basis of studies on Nunivak Island (Cox and Dalrymple, 

1967; Hoare and others, 1968). With further examination of the abundant widespread volcanic rocks of 

Quaternary age in Alaska and sediments in the Arctic 

Basin, great opportunities will be present to tie into, 

and perhaps refine, the geochronometric time scale of 

geomagnetic polarity epochs (Cox and others, 1963a, b, 

1964a, b, 1965; Cox, 1969; Clark, 1969). 

QUATERNARY TECTONISM 

The first summary of Quaternary tectonics in any 

large part of North America was by King (1965). No 

such summary is available for Alaska, or perhaps yet 

possible in any detail. More than half of Alaska is seismically active today and has a rich tectonic record. 

Effects of Quaternary tectonism have long been known 

and are reflected in faulting of glacial deposits (Richter 

and Matson, 1971; Stout and Brady, 1972; Stout and 

others, 1972), uplifted glacial terraces in mountains 

(Wahrhaftig, 1958), uplifted marine terraces in southcentral Alaska (Twenhofel, 1952; Miller, 1953a), the 

York terrace on western Seward Peninsula (Sainsbury, 

1967a, b), and faults in the frozen nonglacial deposits in 

central Alaska (Pewe, 1958b; Patton and Hoare, 1968) 

and elsewhere. 

The study of Quaternary tectonics received a tremendous impetus from the great Alaska earthquake of 1964 

(Plafker, 1965; Wood, 1966; National Academy of Sciences, 1968,1970, 1971). Various aspects of Quaternary 

tectonism are discussed by Plafker and Rubin (1967). 

THE PLIOCENE-PLEISTOCENE BOUNDARY 

The position of the worldwide Pliocene-Pleistocene 

boundary is currently a controversial issue. The problem was reviewed by Flint (1971, p. 381-382) and can 

be summarized as follows. Historically, the boundary 

was placed on the basis of either evolutionary differences between fossil organisms or evidence for the 

climatic cooling (Flint, 1965), expressed mainly in 

glaciation. In fact, the Pleistocene became equated with 

the glacial or the ice age period. It has been known from 

Alaska since 1932 (Taliaferro, 1932) that glacial deposits in the Gulf of Alaska were Pliocene in age, and 

this was carefully documented by Miller (1953a, 1957). 

However, not until the sixties did widespread evidence 

appear that glacial sediments, both terrestrial and 

marine, were deposited in Pliocene and Miocene time 

(table 1), especially in the high latitudes. 

The presence of cold-water marine and terrestrial 

faunas in lower latitudes, representing a migration 

from the polar areas, is thought by many to mark the 
12 

~ 

2S. 

1-

z 

w 

(f.) 

w 

a: 

a.. 

w 

a: 

0 

u. 

w 

Ol 

0 

Paleomagnetism 

(Cox, 1969) 

QUATERNARYGEOLOGYOFALASKA 

TABLE I.-Position of the Pliocene-Pleistocene boundary 

Type locality 

La Castella 

section 

(SeUi, 1967; Nakagawa 

and others, 1971) 

Gulf of Alask-a 

(Taliaferro, 1932; 

Q) 

c: 

Miller, 1953a, 1957; 

Bandy, Butler, and 

Wright, 1969; MacNeil, 

1967; Plafker, 1971) 

c: c: .!2 o ... .., u 

UNIT 17 = .!!~ :g"tl 

·- c: ::?!.!! 

Top of unit 17 

Chlamys plafkeri 

appears 

Pleistocene 

Pliocene 

Chlamys 

(Leochlamys) 

tugidakensis 

..!!! 

II '"'~~lr u~ i mate DO!Iitil)n II 

of Middleton Island 

section inferred 

from paleomagnetic 

data (George Plafker, 

Edward Mankinen, 

and Richard Doell, 

written commun., 

May 9, 1972) 5 .!2 IL-----.------'1 

ALASKA 

St. Elias and Bering Sea Alaska Range 

Wrangell Mts (Hopkins, 1967b; (Wahrhaftig, oral 

(Denton and oral commun., 1972) commun., 1970) Armstrong, 1969) 

2 or more 

tillites 

l-----2.7 

Browne 

Glaciation 

1-----+- 8.4 

Q) 

c: 

8 

0 

~ 

Turborotalia 

pachyderma appears 

Poul Creek Fm. 

10t lites 

~----L--10.0 

14L_------~----------~L_--------~------~--------~-----~ 
50 km south of 

Cape Deceit 

(Hopkins and 

others, 1971) 

f-------5.7 

Basalt flow 

Hoogendorn 

flora 

(forest of spruce, 

birch, pin~. 

and hemlock) 

THE PLIOCENE-PLEISTOCENE BOUNDARY 

TABLE 1.--Position of the Pliocene-Pleistocene boundary-Continued 

Nome 

(Hopkins, 1973) 

Glaciation 

ALASKA 

fStevenwald and (Hopkins and 

others, 1968) others, 1971) 

Ocean no 

warmer than 

present 

Permanent 

ice pack 

unchanged 

for last 105 

years 

(inferred 1 .5 --+----L- 1.5 

date) Possibly 

warmer 

water and 

ice rafting 

Ice rafting 

I 

activity began 

Glacial-marine 

4.5 

Brown lutite 

(Herman, 1970; 

Herman and 

others, 1971; 

Herman, oral 

commun., Dec 

1973) 

Intermittent 

permanent 

ice pack 1---~- 0.7 

Pack ice 

free 

Nunivak Island 

paleomagnetism 

(Hoare and 

others, 1968) 

Antarctica 

(Denton and 

others, 1971) 

Ice sheet 

in West 

Antarctica 

Iceland 

Tjornes Peninsula 

(Einarsson and 

others, 1967) 

13 

2 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

L_ ________ J_ ________ _L ________ ~---------L--------~----------~--------~--------~14 

Compiled by T. L. Pe'we' 
14 QUATERNARY GEOLOGY OF ALASKA 

beginning of Pleistocene time; however, such migrations are also represented in strata oflate Tertiary age. 

Therefore, glacial climates are not a satisfactory 

method for determining the position of the PliocenePleistocene boundary. As Flint remarked (1971, p.2), 

we now think in terms oflate Cenozoic cold climates and 

glaciers and do not associate them only with the 

Quaternary. In a rather informal manner, some scientists use the term Quaternary to mean the last 2 or 3 

m.y. (million years). 

Under the auspices of international congresses, the 

position of the Pliocene-Pleistocene boundary (and 

therefore the Tertiary-Quaternary boundary) has received much study and official recommendations have 

been made. It was recommended at the 18th International Geological Congress in 1948, the 6th International IN QUA Congress in 1961, and at the 8th International INQUA Congress in 1969 that the La Castella 

section in southern Italy be regarded as the boundary 

stratotype fixing the position of the PliocenePleistocene marine boundary. The boundary is placed 

at the horizon characterized by the sudden appearance 

of Hyalinea baltica (table 1), a cold-water species of 

Foraminifera which migrated from the North Atlantic. 

Selli (1967) and Nakagawa, Niitsuma, and Elmi (1971) 

gave a date of 1.8 m.y. for the Pliocene-Pleistocene 

boundary in the La Castella section (table 1) on the 

basis of magnetic, microfauna!, and radiometric evidence. 

In this report, the writer uses the date 1.8 m.y. for the 

temporal position ofthe Pliocene-Pleistocene boundary, 

although it is abundantly evident that in Alaska there 

is no known sharp break at this time in the glacial 

record, in either marine or terrestrial sediments, or an 

abrupt change in faunal or floral types (table 1). 

Attention has only recently been focused on the problem of defining the Tertiary-Quaternary boundary in 

Alaska. Continuing studies of faunas, floras, and remnant magnetism coupled with potassium-argon dating 

of rocks of late Tertiary or early Quaternary age have 

begun to provide more precise age assignments (table 

1). In many areas, sediments of middle or late Pleistocene age lie unconformably on much older, preQuaternary rocks; in other areas the oldest Quaternary 

rocks whose ages can be established rest on still older, 

little deformed sediments or volcanic rocks of either 

early Quaternary or late Tertiary age. 

At the present time, the position of the Pliocene and 

Pleistocene boundary can be most closely approximated 

in sequences of fossiliferous marine sediments. A land 

bridge existed in early Pliocene time; Hopkins (1967a, 

p. 454) stated ((there is a clear record of repeated dispersals of land animals across Beringia through much of 

the Pliocene, during the interval from 10 to 4 million 

years ago." However, in late Pliocene time, about 3.5--4 

m.y. ago, Bering Strait was reopened and p~rmitted 

marine animal migrations. This is inferred from the 

presence of identical species of diagnostic Pliocene mollusks in both the North Pacific and the North Atlantic 

at this time (Durham and MacNeil, 1967). Late Pliocene 

sediments interbedded with basaltic lava flows and tillites on the Tjornes Peninsula of Iceland record an 

influx of Pacific mollusk species, reflecting the opening 

of Bering Strait about 3.5 to 4 million years ago (Einarsson, 1967) (table 1). It also now seems possible to correlate certain marine deposits in Alaska with the Pliocene 

Coralline Crag of England and certain other Alaskan 

marine deposits with the Pleistocene Red Crag of England on the basis of the common occurrence of several 

members of rapidly evolving stocks of Neptunea, 

Chlamys, and Astarte. Most of the beds diagnosed as 

Pliocene in Alaska on the basis of these genera also 

contain mollusks apparently restricted to Pliocene beds 

on the Californian, Siberian, and Japanese coasts. 

Alaskan beds diagnosed as Pleistocene contain few or 

no forms indicative of Pliocene age elsewhere on North 

Pacific shores. 

One of the most complete records of late Cenozoic 

glacial and faunal data in the world is that reported 

from the Gulf of Alaska. It is also here that a good 

chance exists for the accurate placement of the 

Pliocene-Pleistocene boundary. The Yakataga Formation has long been known to contain Pliocene and Pleistocene fossiliferous marine tillites (Taliaferro, 1932; 

Miller, 1953a, 1957; MacNeil, 1967; Bandy and others, 

1969). The most critical exposure is the welldocumented section of 1,220 m of conglomerate, siltstone, and conglomeratic sandy mudstone beds on Middleton Island (pl. 1; Miller, 1953a, table 1). 

On the basis of the study of pectin ids in the section, 

MacNeil (1967, p. 32) suggested that the PliocenePleistocene boundary be placed at the top of unit 17 of 

Miller's section. Unit 17 is about 300m from the top of 

the section and marks the position where Chlamys 

pseudislandica plafkeri first appears. The top of the 

range of Chlamys (Leochlamys) tugidakensis lies immediately below and is Pliocene (table 1 ). 

Because of the critical nature of the Middleton Island 

section in regard to the Pliocene-Pleistocene boundary, 

Plafker, Mankinen, and Doell (written commun., May 

9, 1972) attempted to relate the section to the standard 

paleomagnetic scale. On the basis of preliminary examination, they inferred that the section covers the 

time interval from about 2 to 0.7 m.y. ago (table 1 ). Unit 

17 would be at about 1.5 m.y. ago, if the deposition rate 

were constant. 

Subsequent to MacNeil's (1967) report, additional 

fossil collections have been made, and Plafker stated 

(oral commun., May 11, 1972) that C. plafkeri now is 

more widespread and occurs lower in the section than 
GLACIAL GEOLOGY 15 

previously reported. Future studies will undoubtedly 

reframe the placement of Pliocene-Pleistocene boundary on Middleton Island. 

Small late Pliocene or early Quaternary floras (of 

pollen and wood) provide broad correlations between 

marine and nonmarine sediments in Alaska. However, 

an essentially modern taiga flora (spruce to birch) has 

been found in sediments underlying a 5.7-m.y.-old lava 

flow 30 km south of Cape Deceit (Hopkins and others, 

1971). More details will be needed to position the 

Pliocene and Pleistocene boundary on the basis of floras. 

Paleomagnetic and potassium-argon studies made on 

some of the widespread and almost continuous late Tertiary and Quaternary volcanic sequences in Alaska aid 

in relating the events near the Pliocene and Pleistocene 

boundary to the worldwide geomagnetic chronology. A 

rather complete record of late Cenozoic volcanism is 

documented by paleomagnetic and potassium-argon 

studies on Nunivak Island (Hoare and others, 1968) 

(table 1). GLACIAL GEOLOGY 

Because of the difficulty of correlating one isolated 

area in Alaska with another and the early impossibility 

of relating Alaskan glacial sequences to the better 

known glacial sequences of the north-central United 

States and western Europe, provincial names were 

given to many local Alaskan glacial chronologies established during the late 1940's and the 1950's. As field and 

photogeologic studies have progressed, however, it has 

become possible to trace or compare sequences of 

moraines in series of adjoining valleys throughout large 

areas. Radiometric dates, significant stratigraphic relations with marine sediments and other interglacial deposits, and an improved understanding of the nature 

and rates of weathering and denudation have now made 

it possible to make correlations with considerable 

confidence within single mountain ranges and with 

somewhat less confidence between different mountain 

ranges (table 2). It has also become possible in a general 

way to separate drift sheets in most areas into units of 

pre-Illinoian, Illinoian, Wisconsinan, and postWisconsinan ages. By no means have correlation problems been completely eliminated; nevertheless, progress has been sufficient to permit the preparation of a 

glacial map of Alaska at a scale of 1:2,500,000 (Coulter 

and others, 1965); figure 6 is based upon this compilation but incorporates certain modifications resulting 

from new information since the map was compiled and 

from the writer's differences of opinion concerning certain correlations. 

Eventually, it will no doubt be possible to relate preIllinoian Quaternary events in Alaska to the classical 

glacial sequences of north-central United States and 

western Europe. However, until the. earlier glacial sequences in the classical areas, as well as in Alaska, are 

dated accurately, terms such as Nebraskan and Kansan 

probably should not be applied to pre-Illinoian glacial 

events in Alaska, and only provincial names should be 

used (table 2). 

The most reliable correlations are based on the tracing of moraines from one area to another, on radiocarbon dating, and on similar stratigraphic relations. A 

comparison of the topographic expression of moraines of 

various ages in widely separated areas is more difficult 

and less reliable because, in Alaska, denudational processes differ in nature and rate of operation from one 

region to another. Moraines are modified much more 

rapidly by solifluction and frost creep in northern 

Alaska than in southern Alaska; stream erosion and 

gullying probably progress more rapidly in southern 

Alaska than in northern Alaska. Furthermore, the surfaces of the older moraines differ considerably, even 

within small areas, as a result of local and regional 

differences in the thickness of the loess mantle. 

Glaciers have covered about 50 percent of the present 

area of Alaska at one time or another, but large areas in 

central and northern Alaska have never been glaciated 

(fig. 6). Deposits assigned to each of the four major 

Pleistocene glaciations recognized in north-central 

United States are present in at least some parts of 

Alaska. The extents of the late Tertiary and early Pleistocene glacial advances remain almost unknown, but 

the extents of middle and late Pleistocene and Holocene 

advances are well established. 

During Illinoian, Wisconsinan, and Holocene time, 

glaciers were much more extensive in southern Alaska 

than in northern Alaska and much more extensive on 

the south flanks than on the north flanks of individual 

mountain ranges, indicating that the glaciers were 

nourished chiefly by air masses moving northward or 

northeastward from the northern Pacific Ocean. In 

western Alaska glacial ice was much more extensive 

during Illinoian time than during Wisconsinan time, 

but in eastern Alaska the maximum Illinoian and Wisconsinan glacial advances differed very little. Illinoian 

snowline was about 170 m lower than Wisconsinan 

snowline throughout Alaska, and the greater difference 

between the extent of Illinoian and Wisconsinan 

glaciers in western Alaska seems to reflect the wide 

distribution of uplands there that were just high enough 

to serve as source areas for glaciers during Illinoian 

time but not high enough to serve as source areas during Wisconsinan time. 

Wisconsinan time as used in this report encompasses 

the interval that started at the end of the Sangamon 

Interglaciation (approximately 70,000 years ago) and 

ended about 10,000 years ago. The maximum 

Wisconsinan ice advance was attained during early 

Wisconsinan time; advances of late Wisconsinan time 

were less extensive. Glacial advances during· the past 
16 QUATERNARYGEOLOGYOFALASKA 

164" 149" 140° 

T I C R C 0 C E -4N p.. 

GULF OF ALASKA 

EXTENT OF GLACIERS 

• Present glaciers 

'; I 6,000 years ago 

~ Wisconsinan 

ETIJ Illinoian 

E Pre-Illinoian 

U Undifferentiated, mostly 

of Wisconsinan or 

Illinoian age 

150 300 MILES 

0 150 300 KILOMETRES 

PA C/FIC 0 C E AN 

156° 148" 140" 

FIGURE 6.-Extent of Quaternary glaciations in Alaska. Modified from Coulter, Hopkins, Karlstrom, Pewe, Wahrhaftig, and Williams 

(1965). Additional information on Seward Peninsula and Bering Strait from D. M. Hopkins and C. L. Sainsbury (written commun., 1968) and Nelson and Hopkins (1972). 

10,000 years were much less extensive than any late 

Wisconsinan glaciai advance in most parts of Alaska, 

but Holocene glacial advances that culminated 

1,000-2,000 years ago extended well beyond any recognized glacial advance ofV7isconsinan age on the Pacific 

coastal plain and the Pacific slope of the Chugach 

Mountains between Cape St. Elias and Russell Fiord 

(the eastern arm of Yakutat Bay) (Plafker and Miller, 

1958; D. J. Miller, oral commun., 1961). The anomalously large extent of Holocene glaciation between Cape 

St. Elias and Russell Fiord may reflect great uplift of 

this tectonically active coastal area during late Wisconsinan and Holocene time. Reid (1970a, b) showed that 

the late Wisconsinan terminal moraine of Martin 

Glacier, a few miles west of Cape St. Elias, marks the 

most extensive advance of that glacier on land; earlier it 

was a tidewater glacier. Reid concluded that this 

phenomenon too is probably the result of the tectonically active coast during late Wisconsinan and 

Holocene time. 

EVIDENCE OF MIOCENE TO 

EARLY PLEISTOCENE GLACIATION 

The strongly deformed Yakataga Formation and correlative deformed sedimentary sequences exposed between Cape Spencer and Cape St. Elias, on Middleton 
GLACIAL GEOLOGY 17 

Island, and on some of the Trinity Islands south of 

Kodiak Island contain many thick beds of conglomeratic sandy mudstone. This mudstone contains abundant 

striated clasts; its completely ungraded texture and the 

abundant mollusk shells in apparent growth positions 

indicate that the sediment consists of material ~~rained" 

upon the sea bottom rather than material transported 

laterally by turbidity currents or submarine landslides 

(Miller, 1953a, 1957). For these reasons, this mudstone 

is interpreted as glacial drift that accumulated either 

beneath an ice shelf or beneath icebergs broken from 

tidewater glaciers in Tertiary time (table 1). The composite outcrop thickness of the Yakataga Formation is 

about 5,500 m (Plafker, 1967, 1971). The base of the 

Yakataga Formation is of early to middle Miocene age 

on the basis of its molluscan fauna (Miller, 1961b, fig. 

46; Plafker, 1971). Foraminifera, however, indicate 

that it could be as young as late Miocene (Bandy and 

others, 1969). Cooling is first indicated by the influx of a 

cold-water molluscan fauna (Addicott and others, 1970, 

p. 5c) and the cold-water foraminifera Turborotalia 

pachyderma at about the same stratigraphic horizon as 

the lowest beds containing marine glacial deposits. 

These faunas indicate decreases of surface water temperatures of 10°-15°C in early Yakataga time. The 

youngest beds of the Yakataga Formation, which are 

exposed at the top of a 1,170-m-thick section on Middleton Island, are presumably of early Pleistocene age according to F. S. MacNeil (in Plafker, 1967, 1971). At 

least one sheet of tillite at Middleton Island, in the 

upper part of the section was deposited by grounded 

glaciers, not by icebergs or shelf ice (D. M. Hopkins, 

written commun., 1968). 

In an area in the eastern Wrangell Mountains, Capps 

(1915a, 1916b, p. 63-67) reported at least 10 layers of 

supposed tillite in a deformed sedimentary sequence 

that is clearly no younger than early Pleistocene in age, 

but it seems possible that the tillite layers actually 

represent volcanic agglomerate or volcanic mudfl.ow 

deposits. Denton and Armstrong (1969) demonstrated 

that these deposits are tillites, and that the earliest 

tillite is about 10 m.y. old. In the Arctic Ocean, work on 

magnetic stratigraphy, coupled with faunal patterns in 

deep sea cores taken from Ice Island T-3, suggests that 

glaciation began more than 4 m.y. ago (Steuerwald and 

others, 1968; Clark, 1969, 1971). Herman (1970; Herman and others, 1971) suggested that glaciation began 

2.4 m.y. ago (table 1). 

Thus, D. J; Miller's pioneering work and the subsequent work of others in southern Alaska indicate that 

glaciation in Alaska started at least in late Miocene 

time, and perhaps as early as early middle Miocene 

time. This conclusion agrees with the data suggesting 

late Tertiary glaciation in Antarctica (table 1) (Denton 

and others, 1969, 1971) and Iceland (Einarsson, 1967). 

EARLY PLEISTOCENE GLACIATIONS 

Local patches of pre-Illinoian drift have been recognized in most of the glaciated areas in Alaska; widespread deposits are found only along the coast of the 

Gulf of Alaska, on Middleton Island, possibly in the 

upper part of the Y aka tag a Formation, and in a few 

places on the north flanks of the Alaska Range and the 

Brooks Range. Many areas are too small to be shown in 

figure 6. Throughout much of Alaska, glacial advances 

of Illinoian age evidently were approximately coextensive with or more extensive than, the early Pleistocene 

advances~ Where early Pleistocene drift is present, it is 

found only in isolated patches on ridges above the limits 

of ice advances during Illinoian time, in rare exposures 

beneath Illinoian drift, or in areas slightly beyond the 

outer limits of Illinoian drift. 

Along the Gulf of Alaska coast, drift of early Pleistocene age occurs in areas where ice advances of 

Holocene age extended well beyond the limits of late 

Pleistocene ice advances. Here, drift is assigned preIllinoian age on the basis of its degree of deformati~n 

and induration and of molluscan faunas enclosed In 

intercalated marine sediments. The fauna suggests 

that the beds are equivalent in age to the Beringian, 

Anvilian and Einahnuhtan transgressions (Hopkins, 

1967b, p.' 57). Two large shells from Pleistocene beds 

on Middleton Island have been dated by the U238/ 

Th230 method as being 210,000 ± 20,000 years 

and 220,000 ± 20,000 years (Blanchard, 1963), which 

places the beds in late Pleistocene time. However, an 

extensive molluscan fauna collected from these same 

beds indicates to F. S. MacNeil an early or early mi(ldle 

Pleistocene age (in Plafker, 1971). Furthermore, a complex postdepositional tectonic history-involving 

northwestward tilting at an average angle of 28°, truncation of the tilted strata, uplift .above sea level, and 

offset by active minor faults-suggests to George 

Plafker (written commun., Apr. 21, 1970) that the 

radiometric dates are probably too young. 

In areas away from the Gulf of Alaska coast, the early 

Pleistocene drift typically consists of patches of till or 

sprinklings of erratic boulders scattered over old erosion surfaces high above the present valley bottoms. 

There are no recognizable glacial landforms, such as 

end moraines, but in the north-central Alaska Range, 

Wahrhaftig (1958, p.22-27) distinguished the outer 

limit of his Browne Glaciation of early Pleistocene age 

by concentrations of boulders on a loop pattern en.closing the lower middle course of the lower Nenana River. 

Karlstrom (1964, pl. 1) mapped extensive areas covered by pre-Illinoian glaciers on the north side of the 

Alaskan Range from the Tonzona River to the Delta 

River. Many glacial geologists working in this area do 
18 QUATERNARY GEOLOGY OF ALASKA 

not hold this view, and this controversy gave rise to the 

straight-line boundary of the early Pleistocene extent of 

glacier ice along the 153 degree meridian on the map of 

glacial extents in Alaska (Coulter and others, 1965). 

The writer believes the glaciers of early Pleistocene 

time were not as extensive as shown by Karlstrom. One 

point to consider is that these early glaciations may 

have occurred 1-2 m.y. ago or earlier, and the Alaska 

Range may not have been as high as it is now. This 

controversy may stimulate further work on the north 

side of the Alaska Range. 

Submarine drift and glacial topography are now 

known on the sea floor in the Bering Strait (fig. 6)(Grim 

and MacManus, 1970; D. M. Hopkins, oral commun., 

1969) and are thought at this time to represent both 

Illinoian and pre-Illinoian glacier advances or perhaps 

an icecap in the Strait area. Carsola (1954) indicated a 

lack of glaciation of the Continental Shelf of the Chukchi Sea to the north. 

Precise age assignments can be given to a few of the 

occurrences of drift of early Pleistocene age. Hopkins (in 

Hopkins and others, 1960, p.61) considered the single 

sheet of pre-Illinoian drift in the coastal plain at Nome 

to be early and middle Pleistocene because it underlies the marine sediments ofttlntermediate Beach." ttlntermediate Beach" was formerly considered to be of 

Yarmouth age, but it is now (Hopkins, 1967a) assigned 

to the Anvilian transgression because its molluscan 

fauna contains many more extinct species 'and in other 

respects contrasts sharply with the Kotzebuan fauna in 

marine sediments of later pre-Illinoian (Yarmouth?) 

age in the Kotzebue Sound area (Hopkins and others, 

1962; McCulloch and others, 1965; Hopkins, 1967a). 

The writer tentatively considers the Browne and Dry 

Creek Glaciations in the north-central Alaska Range to 

be two early and middle Pleistocene advances because 

they were separated from one another and from the 

later Healy Glaciation of probably Illinoian age by long 

periods during whieh considerable regional tilting and 

stream erosion took place (Wahrhaftig, 1958, p. 31, 

41-42). Recently, Clyde Wahrhaftig (oral commun., 

July 4, 1970) suggested that the Browne Glaciation is 

more than 2. 7 m.y. old on the basis of field relations and 

radiometric dating near Jumbo Dome on the north side 

of the Alaska Range and therefore is pre-Pleistocene in 

age. 

Karlstrom (1960a) considered the Mount Susitna and 

Caribou Hills Glaciations of Cook Inlet areas to represent the Nebraskan and Kansan Glaciations, but without dates all that can be said is that they are preIllinoian in age. Glacial landforms assigned to these 

stages are much more modified than those of the Eklutna Glaciation, and the Illinoian age of the Eklutna 

Glaciation seems well established. 

GLACIATION OF ILLINOIAN AGE 

DISTRIBUTION OF DRIFT 

Prior to 1945, where abundant erratic boulders forced 

the recognition of a glacial event, the glaciation was 

ascribed to an ice advance of Wisconsinan age. Studies 

since 1945 have shown, however, that drift of Illinoian 

age is present in nearly every glaciated area in Alaska. 

There is general agreement as to which areas of surface 

drift should be assigned to the Illinoian glacial cycle 

throughout most of Alaska. However, uncertainties 

persist for areas in southeastern Alaska and on the 

north flank of the Brooks Range. 

The largest areas of Illinoian drift exposed at the 

surface are in western Alaska in the Kotzebue Sound 

and Bristol Bay areas and on Seward Peninsula (fig. 6). 

Farther eastward along the flanks of the Brooks Range 

and along the north flank of the Alaska Range, Illinoian 

end moraines lie only short distances in front of 

moraines of Wisconsinan age. An Illinoian glaciation 

has been identified on the Pribiloflslands (Hopkins and 

Einarsson, 1966). No till of either Illinoian or Wisconsinan age is recognized along the Alaskan coast between Cape Fairweather and Russell Fiord; apparently 

glacim·s in this area were thinner and less extensive 

during Illinoian and Wisconsinan time than they have 

been during the last few thousand years. Little attention has been given to the pre-Holocene glacial history 

of southeastern Alaska, and no attempt has been made 

there to recognize traces of glaciation of Illinoian age. 

Distribution of drift of Illinoian age in far western 

Alaska has been clarified recently. Sainsbury (1967a, b; 

oral commun., 1969) stated that Skull Creek erratics 

are widespread in western Seward Peninsula, and he 

believed that much of the Bering Strait was covered by 

ice at this time. One of the active areas of glacial research in Alaska today centers on the extent and age of 

glaciations in Bering Strait and adjacent Bering and 

Chukchi Seas and the relation to sea level. As indicated 

in figure 6, glaciers from the Chukotka Peninsula of 

U.S.S.R. adjacent to the Bering Strait once extended 

southward and eastward more than 100 km onto the 

Bering shelf, reaching St. Lawrence Island (Hopkins 

and others, 1972, p. 125). Hopkins (1972) believed that 

the glaciers could hardly have extended this far if it 

were a time of high sea level and glacial margins were 

afloat as suggested by Soviet workers. Grim and 

McManus (1970) indicated large-scale d€formation 

structures on the sea floor probably caused by glacial ice 

in contact with the ground surface. Hopkins (1972) 

further concluded that this extent of Siberian ice then 

occurred during Illinoian time rather than during a 

time of high sea level, the Kotzebuan transgression. 

New work by Hopkins has extended the limits of the 
GLACIAL GEOLOGY 19 

Nome River Glaciation in the southern part of the Seward Peninsula and in Bering Strait (compare fig. 6 this 

paper and fig. 3 in Pewe, Hopkins, and Giddings, 1965). 

BASIS FOR AGE ASSIGNMENT 

Drift of Illinoian age is most firmly identified on 

stratigraphic and radiometric evidence near Nome and 

in the shore bluffs of Kotzebue Sound and Cook Inlet. 

Elsewhere, drift sheets are assigned to the Illinoian 

Glaciation on the basis of similarities in surface expression and in positions in local glacial sequences to the 

Illinoian drift in the Nome, Kotzebue Sound, and Cook 

Inlet areas. The drift of Illinoian age at Nome (till and 

outwash of the Nome River Glaciation-Hopkins and 

others 1960, p.51) overlies marine sediments of an earlier Pleistocene interglacial interval and is covered locally by marine sediments ofSangamon age from which 

shells have been dated by radiocarbon as more than 

38,000 years old (W-810, Rubin and Alexander, 1960, p. 

17 4) and by the U 23s/Th2ao method as 100,000 years old 

(Blanchard, 1963). The Illinoian drift on the shores of 

Kotzebue Sound was first described by Hershey (1909). 

More recent work (Hopkins and others, 1962; McCulloch and others, 1965) showed that the till overlies 

marine sediments dated by the U 2as/Th230 m~thod as 

175,000± 16,000 and 170,000± 17,000 years (Blanchard, 

1963); this drift is covered in some places by marine 

sediments and in others by a forest bed more than 

38,000 years old (W-344, Rubin and Alexander, 1958, p. 

1483) of probable Sangamon age. Here sediments of 

Sangamon age are overlain in turn by unoxidized loess 

of probable Wisconsinan age. 

In the Cook Inlet area near Anchorage, oxidized drift 

of the Eklutna Glaciation of Illinoian age is overlain by 

unweathered drift of the Knik Glaciation of early Wisconsinan age (Miller and Dobrovolny, 1959, p. 11; Karlstrom, 1964, p. 33; Trainer and Waller, 1965). On St. 

George Island in the Pribilofs (fig.1 ), Illinoian till is 

bracketed by marine deposits of Kotzebuan (preIllinoian) and Pelukian (Sangamon) age (Hopkins and 

Einarsson, 1966). 

EVIDENCE OF MULTIPLE GLACIAL ADVANCES 

Most areas of Illinoian drift contain more than one 

recognizable morainal ridge, suggesting that the Illinoian glacial cycle, like the Wisconsinan cycle, was a 

complex event consisting of several glacial advances, 

retreats, and readvances. Stratigraphic evidence of 

multiple glacial advances during Illinoian time has 

been found, however, only in the Selawik Lake area, 

inland from the southeast corner of Kotzebue Sound. 

Here, D. M. Hopkins, D. S. McCulloch, and R. J. Janda 

(unpub. data, 1961) found two exposures about 40 km 

apart in which marine and fluvial sediments about 

175,000 years old are overlain by two sheets of Illinoian 

drift separated from one another by a few metres of 

stratified silt and peat. 

SURFACE MORPHOLOGY 

The degree of preservation of primary microrelief on 

the Illinoian drift varies greatly in different physiographic settings. The larger primary relief features resulting from glacial erosion and sedimentation, cirques, 

U-shaped valleys, major morainal ridges, and outwash 

terraces, remain recognizable, but smaller features, 

such as minor morainal ridges, kames, eskers, and kettles have been modified by and commonly obscured by 

mass wasting, deposition of colluvium from nearby 

slopes, and dissection by consequent gullies. In many 

places, the addition of a mantle of loess, several metres 

thick, of late Illinoian and Wisconsinan age has 

contributed further to the obliteration of minor surface 

features on the Illinoian moraines. 

Illinoian moraines consist oflarge, smoothly rounded 

ridges with irregular crests and gentle slopes that are 

devoid of primary microrelief features (fig. 7) and that 

are incised by consequent gullies at intervals of about 1 

km. In the northeastern part of the Alaska Range, 

Pewe and Holmes (1964) and Holmes and Foster (1968) 

showed that slopes are consistently more gentle on 

moraines of the Delta (Illinoian) Glaciation than on 

moraines of the Donnelly (Wisconsinan) Glaciation. 

Lakes are common on Illinoian moraines, but nearly all 

are ((second cycle" thaw lakes developed in initial low 

areas on the surface of the drift. The Delta moraine of 

Illinoian age contains only 1.2 kettle ponds per km2 

while the adjoining Donnelly moraine of Wisconsinan 

age contains an average of 6.2 kettle ponds per km2 ; 

bogs, however, are twice as abundant ·on the Delta 

moraine as on the Donnelly moraine (Pewe and Holmes, 

1964; Holmes and Benninghoff, 1957, p. 6S-69). Mining 

excavations in Illinoian drift near Nome show that original kettle holes have been obliterated by a fill of colluvial silty gravel several metres deep (D. M. Hopkins, 

unpub. data, 1955--1957). Cirques that were occupied by 

Illinoian ice but have remained vacant ever since display the typical hemiamphitheater form, but the original rock cliffs at the head walls have been reduced to 

lines of low rock bluffs 2-6m high on the upper slopes, 

adjoined by long smooth aprons of colluvium or vegetated talus. 

SOILS AND WEATHERING PROFILES 

Drift of Illinoian age commonly displays a soil and 

weathering profile several times deeper and much more 

intensely developed than profiles of Wisconsinan drift 

in the same area. The post-Illinoian weathering profile 

is most easily interpreted as a product of surficial 

weathering processes in places where it is developed in 

fine-grained sediments such as till or glaciolacustrine 
20 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 7.-High oblique aerial photograph of part of a terminal moraine of Illinoian age along the east side of Delta Creek, interior Alaska. 

View looking southwest toward Alaska Range. Photograph by U.S. Army Air Corps, April 24, 1947, 10,000 feet elevation. Photograph No. 75RT-46PL-m-7m5~46RS-24 Apr 47-65A. 

silt and clay; well-exposed fine-grained sediments of 

Illinoian age are easily distinguished from similar sediments of Wisconsinan age on the basis of their weathering profiles. In coarse sediments such as outwash sand 

and gravel, deep and intense oxidation caused by 

surficial weathering frequently has been confused with 

discolorations resulting from the redistribution of iron 

by ground water (for example, see discussion in Miller 

and Dobrovolny, 1959, p. 33-34); thus, distinctions between coarse sediments of supposed Illinoian and Wisconsinan age based only upon the presence or absence of 

oxidation colors must be regarded with suspicion. 

The post-Illinoian weathering profile on Illinoian 

· drift is deeper and better developed in southern Alaska 

than in northern Alaska. Till, silt, sand, and gravel of 

the Eklutna (Illinoian) Glaciation near Anchorage are 

oxidized to depths of 10 m or more (Miller and Dobrovolny, 1959, p.11; Karlstrom, 1964). Drift of Illinoian 

age in mining excavations near Platinum is oxidized to 

depths of nearly 15 m (D. M. Hopkins, unpub. data, 

1957). Illinoian till near Nome and on the shores of 

Kotzebue Sound shows oxidation to depths of about 3 m, 

and an excavation in an Illinoian esker showed a 

well-defined Arctic Brown soil profile more than 1. 7 m 

thick (D. M. Hopkins, D. S. McCulloch, and R. J. Janda, 

unpub. data, 1961 )_ Till of the Delta (Illinoian) Glacia-
GLACIAL GEOLOGY 21 

tion in the northeastern Alaska Range is oxidized to 

depths of 1.2-3 m near Big Delta (Holmes and Benninghoff, 1957, p. 79; Holmes and Pewe, 1965) and to 3 m 

near the Johnson River (Holmes, 1965, p. H10; Holmes 

and Foster, 1968). No descriptions of weathering 

phenomena in drift of Illinoian age are available for the 

north flank of the Brooks Range. 

Some investigators (for example, Pewe and others, 

1953; Pewe and Holmes, 1964; Holmes and Benninghoff, 1957, p. 79; Wahrhaftig, 1958, p. 32) found a high 

proportion of rotten clasts, especially of granitic rocks, 

in near-surface zones in the Illinoian drift. In western 

Alaska, however, D. M. Hopkins (unpub. data, 1957) 

was unable to recognize a consistent relation between 

abundance of weathered clasts and age ofthe enclosing 

drift. 

A deep post-Illinoian weathering profile underlies 

drift of early Wisconsinan age in several places in the 

Cook Inlet area (Miller and Dobrovolny, 1959, p. 11). 

The post-Illinoian weathering profile is covered by loess 

of Wisconsinan age on the shores of Kotzebue Sound 

(Hopkins and others, 1962; McCulloch and others, 

1965), indicating th~t most of the weathering was accomplished during the Sangamon Interglaciation. 

SNOWLINE 

The writer and his coworkers made a series of compilations of the former positions of snowline during Illinoian and Wisconsinan time as interpreted from the 

altitudes of cirque floors in various parts of Alaska. 

Illinoian snowline lay approximately 500--600 m below 

present snowline and about 150--250 m below Wisconsinan snowline throughout a large part of Alaska (figs. 

8, 9). Snowline was highest in the dry continental climate of east-central Alaska and lay at an altitude of 

about 1,250 m during Illinoian time (Pewe and Burbank, 1960; Pewe and others, 1967). It sloped downward 

to an altitude ofless than 300m on Seward Peninsula in 

western Alaska (fig. 8). Snowline lay appreciably lower 

on the south sides than on the north sides of individual 

mountain ranges. 

Hopkins (written commun., 1968) suggested that at 

one time the Illinoian(?) snowline intersected present 

sea level on the Aleutian Ridge because glacial ice came 

from present water areas southwest of Amchitka Island 

(pl.1 ) and overrode the east end of the island. On St. 

George Island 700 km northwest of the Aleutians, the 

Illinoian snowline was at an altitude of 150m (Hopkins 

and Einarsson, 1966). 

SI GI\' IFICANCE O F THE DISTRIBUTION 

PATTERN O F ILLINOIAN DRIFT 

In Western Alaska, glaciers were vastly more extensive during Illinoian time than during Wisconsinan 

time, but the difference in extent decreases eastward. 

However, snowline during Illinoian time lay about 170 

m below the position of snowline during Wisconsinan 

time (fig 8) (Pewe and others, 1967) throughout a large 

part of Alaska. The relatively greater extent of glaciers 

during Illinoian time in western Alaska evidently is a 

result of the wide distribution of upland areas that were 

just high enough to support cirques and small icecaps 

during Illinoian time and that were not high enough to 

project above snowline during Wisconsinan time. 

The pronounced asymmetry in the extent of glaciation and the position of snowline on all mountain ranges 

of Alaska, including the Brooks Range, indicate that 

during both the Illinoian and Wisconsinan glacial cycles, the glaciers were nourished primarily by moisture 

from airmasses arriving from the south or southwest. 

This feature was first pointed out by Capps (1912) and 

restated by Karlstrom (1964) and later workers. 

Neither the common features in the two patterns of 

glaciation nor their differences seem explicable in 

terms of changes in the amount of moisture that might 

have been contributed by airmasses entering Alaska 

from the Arctic Basin as suggested by Ewing and Donn 

(1956, 1958). The Bering shelf, constituting approximately the northwestern third of the Bering Sea, was . 

evidently dry land during most ofWisconsinan time and 

probably during most of Illinoian time (Hopkins, 

1959b). Airmasses moving into Alaska during these 

glacial intervals must have obtained most of their moisture while passing over the north Pacific Ocean and 

western Bering Sea. 

GLACIATION OF WISCONSINAN AGE 

DISTRIBUTION AND EXTENT 

Drift of Wisconsinan age is found in nearly all the 

mountainous areas of Alaska (fig. 6). North of the crest 

of the Alaska Range and of the Alaska Peninsula, the 

glaciers were essentially alpine in character; they filled 

mountain valleys and in places spread as piedmont 

lobes in adjoining lowlands. However, most lowland and 

upland areas in central and northern Alaska were free 

of ice. Areas south of the crest of the Alaska Range and 

the Alaska Peninsula were almost completely inundated by ice, and icecap conditions prevailed over large 

areas. Glaciers originating in the mountains filled adjoining lowland basins such as the broad Susitna valley 

and spread onto the then-dry continental shelf, thickening to form icecaps as much as several tens of kilometres 

wide and several hundreds ofkilometres long. An icecap 

in Shelikof Strait sent outlet glaciers northward 

through low passes in the mountainous backbone of the 

Alaska Peninsula (pl.1) to spread as piedmont lobes on 

the coastal plain along the southeastern coast of Bristol 

Bay; other ice tongues pushed from Shelikof Strait 

southward into valleys in southwestern Kodiak Island 
(/) 

w 

a: 

~ 

~ 

~ 

z' 

0 

f-

<1: 

> 

w 

...J 

w 

w 

a: 

:J 

f-

<1: 

14 ~~~~~~~~~~~==========================~~~~~~~~~~~~~~~=:==========================~;====================================;, 12 F • Mean June-August air temperature • • • •1 1~ ~ • 

a: u w c 

"-Z 

~-w 

fa: 

;:( 

6 

4 

2 

of-------------------------------------------------------------------ooc :~ • • Mean annual air temperature 

-6 • • --

-8 

1000 

SEA 

LEVEL 

(1) Present snowline 

(2) Wisconsinan snowline 

(3) Illinoian snowline 

(4) Solifluction lobes 

(5) Present tree line 

(6) Altiplanation terraces 

Index map 

~ 

.•. ~~~'•o-o- •ot:J~· 

0 

HORIZONTAL SCALE 

100 200 MILES 

0 100 200 KILOMETRES 

VERTICAL EXAGGERATION X 106 

FIGURE 8.-East-west section across central Alaska illustrating change of certain meterological parameters and elevations of present snowline, snow lines of Wisconsinan and 

Illinoian age, well-developed altiplanation terraces, solifluction lobes, and present tree line. Compiled by T. L. Pewe and L. R. Mayo. (Past snowlines were determined 

from the base of cirques.) 

1:\::1 

1:\::1 

.{) 

e 

~ 

~ 

~ 0 

tz:l 

0 

t'"' 

0 

~ 0 

"'r:: 

r:n 

~ ~ 

> 
Mean June-August air temperature 

u 

0 

+10z 

w 

a: 

::::> 

•LL 

~01-

Ucnz Www 

a:: ..... -l 

0.~<(2 

-lw> 

<(:::1ES 

=>zo Z-w 

Mean annual air temperature 

1- 00 <( 

a: 

w 

Q. 

:::1E 

w 

1-

ffc 

~ -1o1I 

z ;i a: 1 

<(ow 

~~~ w<(s; 

:::1E!::: 

~ 4000 a: 

1-

w 

:::1E 3000 

~ 

z' 

0 2000 

i= <( 

~ 1000 -l 

w 

Fort Yukon 

-(1) 

Alaska 

K 

~Yukon-Tanana 

_______ _t __ ~--~~-v---~-~(\-~-~-~~:!:~ \ " · · ~-~ -~ --------;-----~ --···- -- ----, -- -- --- -- vv . ' 

SEA 1 Lh 1 V \ 1}:\K 1\ 1 _ .. _, __ , .... v Range Upland '-" "'-- LEVEL~~~~~--~L------------------~~~--~~~~~----~===========:------------~~~~~~ 

Index:[) . SOUTH 

(1) Present snowline 

(2) Wisconsinan snowline 

(31 Illinoian snowline 

(4) Present treeline 0

'\:1 ~. 0 0

0 

map~ 0

oOI: 

HORIZONTAL SCALE 

0 100 200 MILES 

0 100 200 KILOMETRES 

VERTICAL EXAGGERATION X53 NORTH 

~ 

FIGURE 9.-North-south section across central Alaska illustrating change of certain meterological parameters and elevations of present snowline, snow lines of Wisconsinan 

and Illinoian age, and present tree line. Climatological data from the Brooks Range is modified from Porter (1966). Those stations are about 250 km west of the section. 

Compiled by T. L. Pewe and L. R. Mayo. (Past snowlines were determined from the base of cirques.) 

§J 

g; 

~ 

~ 0 

5 

~ 

l'-:1 

C>:l 
24 QUATERNARY GEOLOGY OF ALASKA 

that were too low to support local alpine glaciers during 

the Wisconsinan glacial cycle (Coulter and others, 1965; 

E. H. Muller, Clyde Wahrhaftig, and T. N. V. Karlstrom, oral commun., 1955--57). Similar icecaps accumulated in several places on the southern half of the 

Aleutian Ridge and moved northward over the lower 

parts of the present islands (Judson, 1946; Bradley, 

1948; Scruton, 1953; Coats, 1956; Byers, 1959; Powers 

and others, 1960; Hopkins and Einarsson, 1966). Wisconsinan drift is lacking along the coast of the Gulf of 

Alaska between Cape St. Elias and Russell Fiord. 

Glaciers there may have been less extensive during 

Wisconsinan time than during Holocene time; apparently mountains north of this part of the Gulf of Alaska 

coast were lower during Wisconsinan time than at present and consequently supported less extensive glaciers 

(D. J. Miller, oral commun., 1960). 

Wisconsinan glaciers pushed south into Prince William Sound and are in part responsible for the present 

submarine topography (Von Huene and others, 1967). 

The increase in submarine geological work in Prince 

William Sound and adjacent areas, stimulated by the 

1964 Alaskan earthquake, has already enlarged our 

views of glacial action in this area and may lead to a 

better understanding of ice shelf deposits. 

Deglaciation during late Wisconsinan time in areas 

of alpine glaciation north of the crest of the Alaska 

Range seems to have consisted of a gradual shrinkage in 

the thickness and extent of ice tongues that remained 

active even in their frontal areas. However, deglaciation in areas of large coalescent and piedmont ice masses south of the Alaska Range was much less orderly. 

Widespread dead-ice features, su~h as areas of kamekettle topography, networks of eskers, and successions 

of(annual?) marginal channels in the wider valleys and 

lowland areas, record ice stagnation and down-wastage 

without further movement in large areas. Dead-ice features are especially abundant in the lower Matanuska 

Valley northeast of the head of Cook Inlet (Trainer, 

1960), in parts of the Copper River Basin (D. R. Nichols 

and J. R. Williams, oral commun., 1955--60), and in the 

belt of the lowlands just south of the Alaska Range 

between the Alaska Railroad and the Richardson 

Highway (Pewe, 1961c, 1965c; Kachadoorian and 

others, 1954; Jahn, 1966, fig. 38, p. 127). 

BASIS FOR AGE ASSIGNMENT 

The Wisconsinan glacial cycle in Alaska was clearly a 

complex event consisting of at least two major glacial 

advances; several minor oscillations of ice fronts occurred during the latter of the two major glacial events 

(table 2). In several areas the two major divisions of the 

Wisconsinan glacial cycle are well established by 

stratigraphic investigations and radiometric dating as 

approximately equivalent to the early and late Wisconsinan glacial cycles in north-central United States. 

Some of these areas are Cook Inlet (Karlstrom, 1964; 

Trainer and Waller, 1965), southwestern Brooks Range 

(Hamilton, 1969), Chagvan Bay (Porter, 1967), and 

York Mountains (Sainsbury, 1967a, b) (table 2). 

Records of early Wisconsinan Glaciation have not yet 

been recognized in some areas. Sainsbury (1967a, b) 

pointed out that early Wisconsinan deposits have not 

yet been mapped in the Kigluaik Mountains of the Seward Peninsula but that they probably do exist. 

Drift of Wisconsinan age in the shore bluffs of Cook 

Inlet has been dated as a result of detailed studies by 

Miller and Dobrovolny (1959) and by Karlstrom (1965). 

An abundance of stratigraphic observations and 

radiometrically dated organic specimens establish that 

the Knik Glaciation is of post-Sangamon age but older 

than 37,000±2,000 years, and thus it is of early Wisconsinan age (Karlstrom, 1964, p. 57). 

Karlstrom (1957, 1960a) considered the Knik drift to 

be of ((post-Illinoian, pre-Wisconsinan (Sangamon)" 

age, and Miller and Dobrovolny (1959, p. 15) considered 

it to be pre-Wisconsinan but not necessarily as old as 

Sangamon or Illinoian. These differing age assignments reflect different concepts of the duration of the 

Wisconsinan Glaciation, rather than different opinions 

as to the absolute age and correlation of the Knik Glaciation. 

Drift of the Knik Glaciation rests on interglacial deposits ofSangamon age and is covered by the Bootlegger 

Cove Clay. The clay consists of three units and was 

regarded in the past as estuarine, lacustrine, or marine. 

Smith (in Hanson, 1965, p. A20) studied the Foraminifera and concluded that the clay is entirely marine. After 

deposition of the middle unit, the Naptowne glacial 

advance occurred in the Anchorage area. 

During the fifties and sixties, the Bootlegger Cove 

Clay was thought to be middle Wisconsinan in age and 

indicative of a higher stand of sea level. A U2as/Truao 

date of38,000-48,000 years (Blanchard, 1963) on shells 

from the clay supported this concept. The N aptowne 

Glaciation was thought to be late Wisconsinan in age 

(Karlstrom, 1964). 

Four recent radiocarbon age determinations and a 

new urani urn series age on shells from the Bootlegger 

Cove Clay indicate that it was deposited about 14,000 

years ago (Schmoll and others, 1972). The clay, designated the type deposit for the Woronzofian transgression, is now interpreted by Schmoll, Szabo, Rubin, and 

Dobrovolny (1972) as representing a marine transgression after the maximum development of the glaciation 

of Wisconsinan age, rather than an interstadial event of 

middle Wisconsinan age or an older glacial or interglacial event. The N aptowne advance is younger than 

14,000 years and is not of conventional late Wisconsinan age as c}.ocumented by Karlstrom. 
GLACIAL GEOLOGY 25 

In the Anaktuvuk Pass area of the central Brooks 

Range, Porter (1964) showed by radiocarbon dating that 

the Itkillik Glaciation of Detterman, Bowsher, and 

Dutro (1958) is late Wisconsinan in age instead of early 

Wisconsinan aud also divided the Itkillik Glaciation 

into four stades (table 2), the youngest of which culminated about 6,200-8,300 years ago and the second oldest 

of which culminated about 13,300 years ago. On the 

south side of the central Brooks Range, Hamilton (1969) 

demonstrated by use of radiocarbon dating that his 

Siruk Glaciation is late Wisconsinan in age (younger 

than 31,000 years) and his Alatna Glaciation is early 

Wisconsinan in age (older than 38,000 years). 

In the Chagvan Bay area southeast of the Kilbuck 

Mountains at Platinum (fig. 6), Porter (1967) reported 

multiple glaciations. Although early workers (Mertie, 

1940; Hoare and Coonrad, 1961a, b) assigned the drift a 

Wisconsinan age, Porter recorded two glaciations of 

pre-Wisconsinan age and two of Wisconsinan. His 

Chagvan Glaciation is early Wisconsinan and more 

than 45,000 years old. The overlying Unaluk drift is 

termed late Wisconsinan and dated as older than 8,900 

years but less than 45,000 years. 

In the far western part of Seward Peninsula, Sainsbury (1967a, b) mapped drift of early Wisconsinan age 

overlying the Lost River terrace of Sangamon age and 

itself overlain by drift of a younger glaciation older than 

10,000 years. Near Mount McKinley National Park organic material in the sediments of a former lake that 

had been partly confined by the outermost glacial ice at 

the culmination of the Riley Creek Glaciation in the 

Nenana River valley has been radiocarbon-dated as 

being 10,560±200 years old (W-49, Suess, 1954; also see 

Wahrhaftig, 1958, p. 45--46). 

~~stop dates" establishing minimum ages of 

8,000-12,000 years for Wisconsinan drift are available 

from the upper and lower Delta River areas (Pewe, 

1965c, p. 66 and 91; Ives and others, 1964, p. 67-68) and 

in a few other areas, but throughout most of Alaska, the 

assignment of particular drift sheets to the vVisconsinan glacial cycle is based upon similarities in topographic expression and position in local glacial sequences to the Wisconsinan drift in dated positions in 

Alaska. 

SURFACE MORPHOLOGY 

Primary depositional and erosional topography on 

Wisconsinan drift is so sharply defined and well preserved that the glaciated character of the terrain is 

immediately obvious to the most casual observer (fig. 

10). Mass wasting has modified the surfaces of 

moraines, valley walls, and cirques of the older advances of Wisconsinan age compared with those affected by the latest Wisconsinan advances, but the differences are subtle and emerge only upon detailed examination. 

Frontal slopes on older Wisconsinan moraines appear 

to be slightly less steep than those on youngest Wisconsinan moraines, but no quantitative studies have been 

published demonstrating a consistent difference. Kettles on the older moraines commonly contain an appreciable thickness (as much as 3-5m) of fine sediment and 

peat, and some kettles are now the sites of meadows and 

bogs; but, again, no studies demonstrating a systematic 

difference in the character of kettles on the older and 

younger Wisconsinan moraines have been reported. 

Older and younger Wisconsinan lateral moraines have 

not been observed to differ appreciably in most places. 

The steep walls of alpine valleys and cirques 

glaciated during earlier and later Wisconsinan time 

differ more appreciably. The walls of valleys glaciated 

in earlier Wisconsinan time have been markedly regraded by mass wasting. 

SOILS AND WEATHERING PROFILES 

Soils and weathering profiles on drift of Wisconsinan 

age are much thinner and less conspicuous than those 

on drift of Illinoian age. Older Wisconsinan moraines 

commonly show soil profiles about twice as thick as 

those developed on the younger Wisconsinan moraines 

in the same area. In general, soils are thinner and less 

intensely developed as one proceeds northward or to 

higher elevations. 

In the Anchorage area, till of the early Wisconsinan 

Knik Glaciation is oxidized to depths of 1-2m where it 

is exposed at the surface and to depths of 35--60 em 

where it is covered by the Bootlegger Cove Clay; no 

depths of oxidation are reported for till of theN aptowne 

Glaciation, but outwash of N aptowne age has a soil 

profile 60 em deep in one exposure (Miller and Dobrovolny, 1959, p. 6, 22, 24). Till of late Wisconsinan age 

in the southwestern Copper River Basin is oxidized to a 

depth of 1 m (J. R. Williams, written commun., 1964). 

Holmes and Benninghoff (1957, p. 84) reported soils 

only 30-90 em deep, expressed by oxidation and secondary lime concentrations, in moraines of the Donnelly 

Glaciation probably of late Wisconsinan age. Donnelly 

till in the Johnson River area is weathered to a depth of 

50 em (Holmes and Foster, 1968, p. 32). Till of late 

Wisconsinan age at altitudes of 250-900 m along the 

Denali Highway on the south flank of the Alaska Range 

displays a well-developed podzol accompanied by oxidation extending to depths of30-60 em (Kachadoorian and 

others, 1954). D. M. Hopkins (unpub. data 1957) was 

unable to detect soil profiles on Wisconsinan drift on 

Seward Peninsula, but outwash and alluvial fan gravel 

of probable late Wisconsinan age show Arctic Brown 

soil profiles 30-60 em thick. In the northeastern Brooks 

Range, Holmes and Lewis (1961) reported a ~~faint 

weathering profile approximately 1 m thick" and the 

presence of iron-stained and weathered rocks in the 
26 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 10.-High-altitude oblique aerial photograph of part of a terminal moraine of Wisconsinan age along the Delta River in interior 

Alaska. The roughness of this moraine is typical of moraines of Wisconsinan age in Alaska. View looking southwest toward Alaska 

Range from over Delta Junction. Photograph by U.S. Army Air Corps, August 29, 1949, 10,000 feet elevation, photograph No. 

206RT-55RT M864 55SRW 29 Aug. 49 9M58. 

upper 60 em of till of the Schrader Glaciation. Till of the 

Peters Glaciation lacks a perceptible weathering profile. 

SNOWLINE 

One of the parameters which yields quantitative information about the distribution of Pleistocene glaciers 

in Alaska as compared with today is the position of past 

and present snowlines. Such information is also valuable in speculating on Pleistocene climates. The term 

snowline is used in various ways, and also, different 

methods of calculations are in vogue. Definitions used 

here are those suggested by glaciologists and appear in 

the revised glossary of the American Geological Institute (1972) and in the International Hydrological Decade guide entitled ((Seasonal Snow Cover" 

(UNESCO/lASH, 1970). 

Climatic snowline. (1) The average line or altitude 

delineating, as of a specified time, the area with more 

than 50 percent snow cover on horizontal surfaces, averaged over a long time period (for example, 10, 30 

years) of climatic significance. (2) The preceding line as 

observed in late summer so that it approximately coincides with the firn line or equilibrium line on glaciers. 

Cf.: regional snowline. 

Equilibrium line. The level on a glacier where the 

net balance equals zero and accumulation equals ablation; the line separating the superimposed ice zone of 

the accumulation area (below). For some temperate 
GLACIAL GEOLOGY 27 

mountain glaciers, it is very nearly coincident with the 

firn line, in which case it is common practice to use the 

latter term; on subpolar glaciers, the equilibrium line is 

lower than the firn line because freezing of meltwater 

occurs below the firn line forming superimposed ice. 

Synonym: equilibrium limit. 

Firn line. (1) The highest level to which the winter 

snow cover retreats on a glacier. (2) The edge of the snow 

cover at the end of the summer season, thus the boundary between the superimposed ice zone below and the 

saturation zone above. Cf.: equilibrium line. Synonym: 

firn limit. 

Glaciation limit. The lowest altitude in a given 

locality at which glaciers can develop or form, usually 

determined as below the minimum summit altitude of 

mountains on which glaciers occur but above-the maximum summit altitude of mountains which have topography favorable for glaciers but on which no glaciers 

occur. 

Orographic snowline. Term not recommended. 

See climatic snowline. 

Regional snowline. The level above which, averaged over a large area, snow accumulation exceeds 

ablation year after year. Cf.: climatic snowli11e. 

Snowline. (1) Momentary line delimiting an area 

or altitude with complete snow cover, or in a zone of 

patchy snow the area or altitude of more than 50 percent 

cover of snow. Synonym: transient snowline. Cf.: 

climatic snowline. (2) The line or altitude on land 

separating areas in which fallen snow disappears in 

summer from areas in which snow remains throughout 

the year; on glaciers it is identical with the firn line. Cf: 

orographic snowline, regional snowline, equilibrium 

line. Also written snow line. 

MODERN SNOWLINE 

METHODS OF DETERMINATION 

Existing methods for determining the height of modern snowline was succinctly summarized by 0strem 

(1966, p. 126-129). The methods can be divided into 

three groups: (1) Those related to the firn line on 

glaciers, (2) those based on distribution of glaciers, and 

(3) those not directly connected with the study of 

glaciers. 

Various methods have been used to plot the distribution of firn line, or climatic snowline of present usage. 

The best method is to make direct mass-balance measurements on a glacier for several years. From this it is 

possible to determine the average height of firn line 

(equilibrium line altitude, ELA); however, this method 

requires extensive fieldwork. A variation of this method 

is to use one or two glaciers, for which there are massbalance measurements, as standards and extend the 

area of snowline distribution by using good topographic 

maps or aerial photographs taken at the end of the 

ablation season. This has been used in Norway (Liest0l, 

1962) and western North America, including Alaska 

(Meier and Post, 1962). 

Another technique for finding the position of equilibrium line altitude on glaciers is to use the accumulation 

area ratio (AAR). Accumulation area ratio is defined 

(Meier, 1962, p. 256) as the quotient of accumulation 

area divided by the total surface area of the glacier. 

Meier and Post (1962, p. 73) demonstrated that healthy 

glaciers (glaciers in dynamic equilibrium or advancing) 

have accumulation area ratios of0.6 or more. Therefore 

by measuring the total surface area of the glacier, the 

equilibrium line is placed in that position on the glacier 

to permit an assumed accumulation area of that ratio. 

This method is gaining favor and has recently been used 

by Andrews and Miller (1972). 

Other methods which are less accurate but entirely 

satisfactory require only good topographic maps and 

permit plotting of snowline over large areas. These 

methods are those in which climatic snowline (firn line) 

is (1) determined from an interpretation of the contour 

lines on a glacier to place the boundary between accumulation and ablation areas, (2) determined to be the 

mean elevation of the glacier, or (3) determined to be a 

line separating the accumulation and ablation areas at 

a position separating a percentage (one-quarter to 

three-quarters) of the lower part of the glacier from the 

upper part. 

A method which eliminates considerable subjectivity, 

does not refer to firn line, and has wide use is the plotting of the ((glaciation limit." 0strem (1964, 1966) 

showed that the altitude of glacier formation can be 

determined by studying the distribution of glaciers and 

the altitude of surrounding summits. It is possible to 

determine a critical height (the ((glaciation limit") 

which has normally to be exceeded to form glaciers. 

0strem (1966) stated that the glaciation limit is about 

100m higher than climatic snowline (firn line). This has 

been supported by work in Baffin Island (Andrews and 

Miller, 1972). The ((glaciation limit" method works best 

where there are many small local glaciers; it is not 

applicable to icecap areas. 

Another method for determining modern snowline 

disregards modern glaciers and relies instead on 

meteorological data. Modern snowlines are controlled 

in part by summer temperatures, and some writers report the elevation of modern climatic snowline may 

nearly coincide with the level of the mean ooc summer 

or July isotherm (Leopold, 1951). By using the known 

lapse rate at a particular point and knowing the mean 

summer temperature near the ground, it is possible to 

calculate the elevation of the ooc summer isotherm and 

thus, perhaps, elevation of modern climatic snowline at 
28 QUATERNARY GEOLOGY OF ALASKA 

that particular locality. Charlesworth (1957, p. 9-10) 

concluded from his literature review, however, that the 

correlation is invalidated locally by the effects of precipitation and wind drifting. He stated (p. 9) that for 

climates between lat. 35° and 70° north, snowline coincides with the isotherm of 4°C±3° in the warmest 

month. MoDERN SNOWLINE IN ALASKA 

The modern snowline in Alaska was probably first 

discussed by Romer (1929) and first sketched from 

glaciers on reconnaissance maps for eastern Alaska by 

Wasowicz (1929). A small-scale map of the equilibrium 

line altitude of the same area was plotted by Meier and 

Post (1962) from firn line and mass-balance measurements on five Alaskan glaciers and observations of firn 

lines on other glaciers from aerial photographs. A more 

detailed map of the equilibrium line altitude was prepared by Meier, Tangborn, Mayo, and Post (1971) for 

the entire western part of North America using the 

same techniques as in 1962. Karlstrom (1964) plotted 

modern snowline from cirque glaciers in south-central 

Alaska. 

To test the technique for locating modern climatic 

snowline in Alaska by using meteorological data alone, 

several localities were analyzed where temperatures, 

lapse rates, and past snowline locations are known 

(Pewe and Reger, 1972). The climatic snowline level is 

close to 1,800 m elevation on two small north-facing 

cirques at the head of the east fork of Itikmalakpak 

Creek approximately 27 km east-northeast of Anaktuvuk Pass (pl. 1). Using the mean July temperature of 

Anaktuvuk Pass (10.3°C at 700 m elevation) and applying the lapse rate of 0.59°C/100 m suggested by Porter 

(1966, p. 87), one can extrapolate that the mean July 

temperature at the 1,800-m level is close to 6.8°C. A 

similar analysis with data provided by Larsson (1960) 

for Chamberlin Glacier shows that the 1958 climatic 

snowline (2,400 m) occurred where the mean July 

temperature was 4.0°C. At McCall Glacier, Benson, 

Fahl, Trabant, Well, and Wendler (1970) showed that 

the 1969 firn line was at an elevation of2,210 m. Using 

their measured lapse rate of 0.57°C/100 m, the writer 

concludes that climatic snowline for that year was 

found where the mean July temperature was -1.5°C. 

Aerial photographs, topographic maps, and data provided by Pewe, Church, and Andreson (1969, table 1, p. 

71-72) were used to determine that the mean July 

temperatures of 10 north-facing glaciers in the northern part of the east-central Alaska Range within 58 km 

of Delta Junction approximate 3.8°C. Thus in the 

Brooks Range and the northern flank of the east-central 

Alaska Range, the mean July temperatures at climatic 

snowline probably range at least from -1.5° to 6.8°C. 

This wide variation is undoubtedly a function of differing amounts of precipitation owing to differences in 

distance from precipitation source, wind drifting, and 

topographic effects. The writer thinks that the variation is too large and unpredictable to use for estimating 

the level of modern snowline in Alaska, unless no other 

data are available. 

Methods Used In This Report 

Several maps of modern and past snowlines have 

been compiled over the years by the writer and colleagues. Figure 11 is a map of Alaska showing distribution of isolines (isoglacihypses) of modern climatic 

snowline altitudes as determined from glaciers and 

perhaps a few perennial snowbanks. The points are 

located by plotting elevations of the lowest, small, 

north-facing cirque glacier from maps on a scale 

1:63,360. Actually the points in each quadrangle are 

generally an average of the lowest cirques, thus 

eliminating an isolated single anomalous low point. 

Many of the central and western Brooks Range data are 

from maps on a scale of 1:250,000. Aerial photographs 

were used where necessary, especially for Grand Union 

Glacier on the Seward Peninsula. On the map, snowline 

was located at two-thirds of the elevation difference 

between the glacier toe and the upper ice limit on small 

circular cirque glaciers, or it was located where low 

medial moraines disappear beneath the snow cover on 

valley glaciers. 

A few of the points plotted from the maps may be on 

perennial snowbanks and below modern snow line. 

Manley (1949, p. 185-186) concluded that in moist, 

cloudy, maritime areas such as Scotland, small snow 

beds may survive 450 m below firn line, as determined 

meteorologically. lves (1960, p. 51) suggested that for 

continental climates the distance of snow patches below 

firn line could be between 763 and 825 m. 

This method of snowline surface determination can 

be readily used in Alaska because good topographic 

maps are available for the entire State. However, the 

writer believes that although such a method gives a 

good representative pattern of modern snovv-line in 

Alaska, because of selecting the lowest cirque glaciers 

and perhaps also including a few snow patches, the 

snowline surface portrayed is perhaps slightly lower 

than it actually is. 

Interpretation Of The Map 

As Flint remarked (1971, p. 66), the snowline in three 

dimensions is the trace of a surface with complex undulations determined by temperature, precipitation, and 

forms of the land. The feature most clearly revealed by 

the map of modern snowline (fig. 11) is the characteristic rise from the windward coast of the State toward the 

interior-a broad effect of precipitation. This feature is 

also graphically demonstrated by the cross sections 

from west to east and south to north showing positions 
GLACIAL GEOLOGY 29 

lica of the mountain mass, owing to a decrease of precipitation with altitude, especially with the windward 

of snowline and the amount of precipitation (fig. 8, 9). In 

the central part of the State, the snowline rises steadily 

from a low of about 600 min far western Alaska to about 

2,000 m in adjacent Yukon Territory. Landward from 

the Gulf of Alaska, an abundant source of moisture, the 

snowline rises abruptly inward from about 400 to 600 m 

to the northwest, to the north, and to the northeast. It is 

interesting to see that moisture for the south side of the 

Alaska Range, even in the eastern part, apparently 

enters through the Cook Inlet trough. 

~direction . If precipitation is insufficient for development of a complete icecap over a mountain mass, then 

small cirques and valley glaciers must form at various 

favorable sites up the slopes on all sides of the mountain 

range. 

Besides generally rising inland, the snowline rises 

over major topographic highs and forms a subdued repPerhaps the most interesting point illustrated by the 

map of modern snowline is the apparent lack of moisture for the glaciers contributed by the Arctic Ocean. 

Snowline rises from west to east along the axis of the 

Brooks Range and northern Alaska in general owing to 

0 150 300 KILOMETRES 

PACIFIC OCEAN 

r~ 114 · 178. 

I 

<:::::;:! .t·· East of Greenwich 1,' 

52• J ALEUTIAN ' 

tT~- FIGURE 11.-Modern snowline surface in Alaska. Data points indicate 

the positions of north-facing glaciers found on maps at scales of 

1:63,360 or 1:250,000. A total of27 data points were mapped in the 

Yukon Territory, Canada, but 13 of these could not be shown as 

they lie within the area covered by the information block. Snowline 

was located at two-thirds of the elevation difference between the 

glacier toe and the upper ice limit on small circular cirque glaciers, 

or it was located where low medial moraines disappear beneath the 

snow cover on valley glaciers. The level of snowline on the small 

cirque glacier at the head of Grand Union Creek, western Seward 

Peninsula, was more precisely located using 1950 U.S. Navy aerial 

photographs. Compiled by R. D. Reger, 1970; data points in southeastern Alaska were plotted by R. H. Stinchfield, 1970. 
30 QUATERNARY GEOLOGY OF ALASKA 

moisture from the west. This relative lack of moisture 

contribution from the north today perhaps results from 

the perennial ice cover over most of the Arctic Ocean. 

WISCONSINAN SNOWLINE 

METHODS OF DETERMINATION 

Position of snowline in Wisconsinan time can beestimated in many ways. One group of methods is concerned with utilizing the position of the cirque, another 

involves the reconstruction of the past equilibrium line 

by reconstructing past glacier surfaces, and another 

method develops a ~~glaciation limit" similar to the line 

determined with modern glaciers. 

Wisconsinan snowline is commonly inferred to be the 

average altitude of floors of small cirques (Flint, 1957). 

Andrews (1965) placed the altitude at the junction of the 

cirque floor and the back wall. Another method for approximating former snowline is to follow the suggestion 

of Manley (1959) that snowline occurs at three-fifths of 

the altitudinal difference between the terminal and 

upper ice limit of a cirque glacier. Some place the Wisconsinan snowline at the median altitude between the 

terminal moraine of a given glacial advance and the 

highest point of a cirque headwall. Another method is to 

estimate snowline from the lower limit of icecaps. 

Richmond (1965) showed that for the Rocky Mountains, 

the late Pleistocene snowline depression obtained by 

using the figure for the median altitude between the 

terminal moraine and the highest point on the cirque 

wall is greater than using the figure obtained from 

cirque floors. He finds that the greatest snowline 

depression is recorded by a line approximated by the 

lower limit of icecaps. 

It is possible to reconstruct a past ((glaciation limit" 

using the same technique described for the modern 

snowline. Instead of mapping the summit altitudes of 

peaks containing small glaciers, one would map the 

summit altitude of peaks containing fresh cirques and 

the summit altitude of nearby mountains that have no 

cirques. This method would probably produce a surface 

that is actually above the past snowline surface but a 

generalized one quite acceptable for use. Flint (1971, p. 

68) stated that using the ~~glaciation limit" produces a 

past snowline about 450 m higher than the actual past 

snowline. 

Another technique for finding the position of past 

snowline is to determine the position of equilibrium line 

altitude on past glaciers using the accumulation area 

ratio (Porter, 1968, 1970), as mentioned under modern 

snowline. To apply this technique, the average accumulation area ratio of healthy glaciers (glaciers in dynamic 

equilibrium or advancing) in an area must be known, 

and the extent of the former ice limit must be accurately 

mapped so that the surface topography of the former 

glacier can be reconstructed. This technique applies 

only to symmetrical area-altitudinal distributions 

about the median altitude; piedmont glaciers cannot be 

used, nor can valley glaciers with large terminal bulbs. 

Meier and Post (1962, p. 73) demonstrated that 

healthy glaciers have accumulation area ratios of0.6 or 

more; therefore, as mentioned under the calculation for 

modern snowline, it is necessary to assume that the 

active past glaciers had an accumulation area ratio 

close to the 0.6 when calculating past equilibrium line 

altitude. 

Determination of the elevation of snowline by this 

more accurate method puts the position of Wisconsinan 

snowline many metres lower than the position obtained 

for snowline using floors of empty cirques. In a study of 

Indian Mountain near Hughes, the writer determined 

the lowering of Wisconsinan snowline from modern 

snowline to be about 450 m on the basis of cirque floor 

studies (figs. 11, 12). R. D. Reger (in Reger and Pewe, 

unpub. data, 197 4) calculated that Wisconsinan snowline was 585 m lower than modern snowline using the 

above equilibrium line altitude method. Therefore, 

snowline changes determined by differences in cirque 

floor must be considered minimum for valley glaciers. 

Aside from the example from Indian Mountain, the 

writer knows of no application of this new method in 

Alaska. Calculation of the positions of Wisconsinan 

snowline in Alaska by this method must be made widely 

in the future and will be a strong step forward. 

METHODS USED IN THIS REPORT 

Because elevations of empty cirques can be easily 

plotted for most areas of Alaska and because all the 

information needed to calculate Wisconsinan snowline 

by Porter's method is not yet available, a surface representing the altitude of snowline in Alaska during 

Wisconsinan time (fig. 12) was compiled by plotting 

elevations of junction of the floor and back wall of sharp, 

empty, north-facing cirques from maps on a scale 

1:63,360. Data for much of central and western Brooks 

Range are from maps on a scale of 1:250,000. Critical 

areas on the north side of the Brooks Range, Seward 

Peninsula, and on St. Lawrence Island were studied 

using aerial photographs. All maps used are modern 

compilations made by the U.S. Geological Survey using 

aerial photographs. The lowest sharp cirque was plotted 

in each 1:63,360 map that showed cirques except in 

southeastern Alaska where 593 cirques were plotted. 

Inasmuch as it is difficult to differentiate between 

cirques of early and late Wisconsinan and Holocene 

ages without detailed studies and because some cirques 

were possibly reoccupied and deepened during two or 

more glaciations, the snowline surface is regarded as 

generalized Wisconsinan in age. 
GLACIAL GEOLOGY 31 

Another factor to be considered is tectonic displacement of cirques during and since Wisconsinan time. 

Many cirques along the edge of the Gulf of Alaska (especially Blying Sound, pl. 1) and along the south side of 

the Alaska Peninsula have been lowered or raised by 

tectonic movement. This movement accounts for the 

many cirques near or below sea level (figs. 13, 14) 

{Alpha, 1970). 

I NTERPRETATION OF THE MAP 

The surface of climatic snowline in Wisconsinan time 

in Alaska parallels modern climatic snowline everywhere at a lower elevation. The surface is lowest in the 

south and far west. There is an abrupt rise in the Gulf of 

Alaska from near sea level to about 1,500 m in interior 

Alaska and adjacent Yukon Territory. There is a 

steady, gradual rise from the Bering Sea on the west, 

eastward to Canada through central Alaska. In general, 

the depression of Wisconsinan snowline from modern 

snowline is about 300-400 min the west and 450-600 m 

in the east (figs. 8, 9), but local variations occur. The 

vertical separation of the two snowline surfaces becomes greater toward the drier interior, as Hastenrath 

(1967, p. 546; 1971, p. 255) discovered in Peru. 

The map supports the concept that the source of moisture in Wisconsinan time was the same as now, even 

PACIF IC 

EXPLANATION 

---3oo----

Isoglacihypse 

Line of equal elevation of lowest 

north-facing Wisconsinan cirque 

bases. Interval, 150 and 300m 

0 150 300 Ml LES 

0 150 300 Kl LOMETAES 

.. 

O CEAN 

r~ 11·· 178' 178' 174' 

I <::::;] f·· East of Greenwich li I West of Greenwich \ 

I 52• / ALEUTIAN . I ISLA,Nbs . <1·- · ~.· _ • I -r------ -#+~·~- __c_~2)2)~TsXt - ~ 

I I ~ . i I .. 

FIGURE 12.-Wisconsinan snowline surface in Alaska. Data points indicate the positions ofthe bases of the lowest, empty, north-facing 

cirques found on maps at scales of 1:63,360 or 1:250,000. Southward from Yakutat Bay only even-hundred-metre contours are 

shown owing to the steep gradients ofthe snowline surface. A total 

of 573 data points have been mapped in southeastern Alaska, but to 

preserve clarity, their locations are not shown. In adjacent Canada 

a total of 4 7 data points have been mapped, but not all are plotted; 

some lie within the area covered by the information block. Compiled by R. D. Reger, 1970. E. M. Schern plotted data points from 

southeastern Alaska, 1970. 
32 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 13.-Cirques drowned largely by tectonic lowering of the 

land. South side of the Kenai Peninsula. U.S. Geological Survey 

Blying Sound C--7, D-7 topographic quadrangles, 1950, 1952. Scale 

1:63,360; contour interval on land 100 ft. 

though the Bering Sea was smaller or perhaps absent 

during part of Wisconsinan time. The snowline distribution illustrates an apparent lack of significant 

moisture for glaciers contributed by the Arctic Ocean, 

which supports the suggestion that the Arctic Ocean 

has long been ice covered (Steuerwald and others, 1968) 

but does not support the concept of Ewing and Donn 

(1956, 1958; Donn and Ewing, 1966) that the Arctic 

Ocean was ice free and contributed abundant moisture 

to form ice sheets during Pleistocene time. 

On the south side of the Chugach Mountains and the 

east side ofthe Kenai Mountains (figs. 13, 14) of southern Alaska, Wisconsinan snowline is detected as lying 

below present-day sea level (fig. 9). Such a lowering of 

cirques is the result of tectonic activitiy since Wisconsinan time (Plafker and Rubin, 1967; Plafker, 1969, p. 

158). In 1964 parts of the area were further warped 

downward by the March 27 earthquake (Plafker, 1965). 

The snowline study indicates that except in certain 

tectonically active areas, Wisconsinan topography, 

wind belts, and precipitation were generally similar to 

what they are today. It is perhaps now timely to consider a position reconstruction of the climatic pattern 

and atmospheric circulation in Alaska during Winconsinan time by statewide information on snowline 

depression. 

HOLOCENE GLACIATIONS 

Events that took place less than 10,000 years ago are 

assigned in this report to the Holocene Epoch. The date 

10,000 B.P. (before present) has been adopted as the 

beginning of the Holocene by the International Association for Quaternary Research (INQUA). At about 

10,000 B.P., a worldwide warming occurred, recorded in 

marine deposits, the pollen spectrum, and snowline position (Fairbridge, 1968, p. 528-530; Morrison, 1969). A 

warming is recorded at this time in northwest Alaska 

(McCulloch and Hopkins, 1966) and in central Alaska 

(Pewe, 1975). Two or possibly three glacial cycles are 

recorded in many parts of Alaska during this interval. 

The early cycle took place between 8,500 and 6,000 

years ago in some areas. A later series of glacial cycles 

began about 4,000 years ago and ended only a century 

ago, but the multiple early and late glacial advances 

within this interval may have been separated by a 

significant deglacial interval of unknown duration 

approximately 1,500--2,000 years ago. 

The Holocene glacial record as recognized throughout 

much of central and northern Alaska is typified by the 

sequence recorded by Porter (1964) in the Anaktuvuk 

Pass area of the Brooks Range. Glaciers were there in 

an advanced position from about 8,300 years ago until 

about 6,300 years ago (table 2), during Porter's Anivik 

Lake Stade of the Itkillik Glaciation (as interpreted by 

Porter). A long deglacial interval was followed by the 
GLACIAL GEOLOGY 33 

Alapah Mountain Glaciation (as interpreted by Porter), 

which culminated about 2,800 years ago. Finally, the 

double moraines of the Fan Mountain Glaciation, which 

generally lie near or in the cirques or near small remnant glaciers, are believed to have formed during the 

last several centuries. 

D][N<GlLJES'lr.AD'lr 

YAJL][oc:- <GlLA<C][JEJR 

lPlE'lrROF 

Karlstrom (1964, pl. 7, p. 44, 56, 64) reported a somewhat similar sequence on the Kenai Peninsula of southern Alaska. The last read vance during the Tanya Stade 

of the Naptowne Glaciation is thought by Karlstrom to 

have taken place about 6,000 years ago. Logs buried in 

drift indicate that some glacial advances during the 

MC <CARTY 

FEET METRES 

4000 

1000 

2000 500 

10,000 3000 

VERTICAL EXAGGERATION 3:1 

160° 

Index map of Alaska 

Sources of information: 

Reimnitz and Von Huene (1969) 

U.S. Geological Survey, map 1:250,000, 

Alaska topographic series, Seldovia, 

1-~~~~~=::==::===~~=:::~~==:::======~F=:=:=:=::::===::;;:;;;;=:;;~~==~~3 U.S. Alaska, Geological 1963 Survey, oblique aerial 

photographs of Nuka Bay, 1961-70, 

Austin Post, Tacoma, Wash . 

FIGURE 14-0rthographic drawing of Nuka Bay, Alaska, south side ofKenai Peninsula, showing drowned cirques and glacial valleys. Drawing by Tau Rho Alpha, U.S. Geological Survey, 1970. 
34 QUATERNARY GEOLOGY OF ALASKA 

Tustumena Stade of the Alaskan Glaciation took place 

more than 2,500 years ago, and indirect evidence led 

Karlstrom to conclude that the Tustumena Stade extended from about 5,000 to 2,000 years ago. The Tunnel 

Stade, also of the Alaskan Glaciation and well dated by 

radiocarbon analyses of logs buried in the older 

moraines and by ring counts from trees growing on 

young moraines, consists of several glacial advances 

during the last 1,500 years. 

Records of early Holocene glaciations along the coast 

of the Gulf of Alaska and in southeastern Alaska are 

lacking. Plafker and Miller's careful study (1958) of the 

moraines of the Malaspina and neighboring glaciers 

records a glacial advance that culminated between 

1,400 and 700 years ago and that was more extensive 

than any Wisconsinan or early Holocene glacial advance. A glacial recession followed, succeeded by a 

readvance that began before A.D. 1700 and that ended 

in different places between A.D. 1791 and A.D. 1904. 

Studies of various parts of southeastern Alaska also 

suggest that glaciers advanced farther during the last 

few centuries than at any previous time within the last 

10,000 years (Lawrence, 1950, 1958; Heusser and Marcus, 1964). The most detailed record is provided by 

Goldthwait's study of Glacier Bay (1963, 1966). A prolonged process of filling the bay with outwash gravel 

began about 7,000 years ago. Glaciers were present in 

the mountains but were lacking in the fiords and lowland valleys of the Glacier Bay area; glacierp in southeastern Alaska then withdrew farther than where they 

are today. Forest beds and beds of sand apparently record a slackening of sedimentation and perhaps an accelerated or renewed glacial retreat during a few centuries after 2000 B.C., but by 1500 B.C., glaciers had 

begun to advance again, and during the ensuing three 

millennia they filled the entire bay. Finally, shortly 

before A.D. 1791, a rapid glacial recession began that 

has continued essentially without interruption to the 

present day. This catastrophic retreat has resulted in 

recessions of the major ice tongues through distances of 

75-100 km. 

Work by Williams and Ferrians (1961) in the upper 

Matanuska River valley reveals a history of Holocene 

advances of the Matanuska Glacier supported by 

radiocarbon dating (table 2). After its retreat in late 

Wisconsinan time, the glacier readvanced 4-8 km more 

than 8,000 years ago and then receded. After local canyon cutting by streams, the glacier readvanced 1.6 km a 

few thou~and years ago. Moraines a few hundreds of 

years old 'lie near the glacier front. 

Detailed work using dendrochronology and 

lichenometry enabled Pewe and Reger (Pewe, 1951a, 

1957b; Reger, 1964, 1968; Reger and Pewe, 1969) to date 

recent advances of five glaciers in the central part of the 

Alaska Range. Advances were dated as A.D. 1830, 1875, 

1650(?), 1580(?) and pre-1580(?). An inspection of aerial 

photographs shows that fresh moraines similar to those 

dated as A.D. 1830 and 1650(?) are widespread 

throughout Alaska. An unpublished report by James 

Rowe of Arizona State University on dendrochronologic 

and lichenometric dating of Holocene moraines ofPuget 

Glacier on the southeast side of the Kenai Peninsula 

indicates two prominent moraines that probably date 

from 1830 and 1650(?). 

Recent summaries of the glacial history of the last 

5,000 years in the North American Cordillera are by 

Porter and Denton (1967) and Viereck (1968). 

SUMMARY 

Alaska contains one of the longest and best records of 

late Cenozoic glaciations in the world, extending from 

late Miocene time until today and including both terrestrial and marine glacial sediments. The deposits in 

some areas may be tied into known marine deposits and 

correlated worldwide. Early and middle Pleistocene deposits not associated with the sea are correlated with 

difficulty, but Illinoian, Wisconsinan and Holocene deposits are widespread and dateable. 

Glaciers in the past occupied about 50 percent of 

Alaska and today cover only 5 percent. During glacial 

maximums, snowline was lowered many hundreds of 

metres, with Illinoian snowline about 170m below Wisconsinan snowline. The Wisconsinan snowline parallels 

the modern snowline everywhere at a lower elevation. 

A steady rise of modern and Wisconsinan snowlines 

from the west and south to the east and northeast 

reflects the broad effect of precipitation on snowline. 

There is no evidence for nourishment of glaciers by 

moisture from the Arctic Ocean. 

Glaciation in Wisconsinan time was complex, and 

deposits of at least two major glacial advances are widespread. Glacial advances of the last 10,000 years are 

excellently displayed in Alaska, and dendrochronology 

and lichenometry will be useful for differentiating 

widespread recent advances from erratic glacial surges. 

EOLIAN DEPOSITS 

Eolian deposits cover a large part of the low-lying 

areas of Alaska and are mostly of middle to late Pleistocene age; only a few deposits are Holocene. The deposits include large areas of loess and reworked loess, 

smaller areas of stabilized dunes, and very small areas 

of active dunes. Practically all loess was derived from 

glacial outwash plains, and the few areas where loess is 

accumulating in significant quantities today adjoin the 

braided flood plains of silt-laden glacial streams. Most 

stabilized sand dunes also adjoin sandy, gravelly glacial 

outwash plains of late Pleistocene age, but a large area 

of stabilized dunes on the Arctic Coastal Plain and a 
EOLIAN DEPOSITS 35 

small area of stabilized dunes on Adak Island in the 

Aleutians (Judson, 1946) probably accumulated on the 

lee side of extensive sandy beaches. Most of the presently active dune areas in Alaska adjoin low-lying 

sandy beaches, but two large active dune areas lie inland within larger areas of stabilized dunes. 

SAND DUNES 

Many of the older reports on the regional geology of 

areas in Alaska note the presence of active dunes, but 

the much larger areas of stabilized dunes commonly 

escaped notice. Not until1951 was the first small-scale 

map published showing the distribution of active and 

stabilized sand dunes (Black, 1951a), and four additional large areas of dunes have been recognized within 

the ensuing 10 years (fig 15). The areas of stabilized 

dunes are not easily recognized because they commonly 

are heavily vegetated, and until aerial photographs 

came into wide use, their distinctive form was not obvious. 

136" 

ACTIVE DUNES 

Active dunes on the coastal beaches are 0. 3-18 m high 

and consist mainly of blowout and transverse dunes, 

foredunes, and cliff-head dunes. They are known 

mainly from the Yakutat area (Miller, 1961a), the delta 

of the Copper River (Tarr and Martin, 1914, p. 466), the 

Bristol Bay area (Black, 1951a, p.103), Seward Peninsula (D. M. Hopkins, unpub. data, 1957), and northern 

Alaska (Black, 1951a) but are present everywhere on 

sandy coasts. The two largest areas of active dunes in 

Alaska are not, however, along modern beaches but are 

in the Koyukuk and Kobuk River valleys. The active 

Nogahabara dune field in the lower valley of the 

Koyukuk is only a small part of a much larger Pleistocene dune field that is now mostly inactive. The active 

dune area is approximately 65 km2 and is composed 

mainly of transverse dunes 15- 60 m high and 90 m long 

or more. The middle Kobuk valley contains another 

large area of Pleistocene dunes, of which 130 km2 contains active dunes (Fernald and Nichols, 1953; Fernald, 

1964). 

STABILIZED DUNES 

700 Stabilized dunes, probably of Illinoian and Wisconsinan age, are widespread, especially in central and 

northern Alaska, but only locally have they been mapped in even a reconnaissance fashion. Most of the dunes 

occur in the valleys of the Tanana, Yukon, Kuskokwim, 

Koyukuk, and Kobuk Rivers-rivers that were impor6Ef tant streams draining glaciated areas in the past. 

0 100 200 MILES 

0 100 200 KILOMETRES 

FIGURE 15.-Major areas of stabilized sand dunes in Alaska. Most 

coastal dunes as well as small parts of the stabilized sand dune 

areas on the Koyukuk and Kobuk Rivers are active today. 

Symbols: D, small areas of sand dunes; K. R., Kantishna River. 

Compiled by F. R. Weber from published and unpublished sources, 

1961. 

ILLINOIAN 

An area of about 780 km2 of poor to fairly well formed 

sand dunes lies against the bedrock hills up to an elevation of520 m north ofthe Tanana River in the vicinity of 

Big Delta, about 145 km southeast of Fairbanks. These 

dunes are parabolic and have rather subdued to fairly 

fresh relief. Local relief is from 0.3 to 3m. The dunes are 

thought to have originated in Illinoian time (table 3) 

when winds blew sand northward from the widespread 

outwash plains and glacial flood plains of the Delta and 

Tanana Rivers (Pewe, 1965b, p. 46 -51). Most of the 

sand forms a blanket covering the hills and has no dune 

form. The sand blanket and dunes subsequently have 

been dissected and covered with loess 0.3-2 m thick (fig. 

16). 

The largest area of stabilized dunes in Alaska extends 

from the Tanana River southward for 160 km into the 

drainage of the upper Kuskokwim River (fig.l). These 

dunes, which are thought to be Illinoian in age, occur on 

high terraces of the Tanana River and its tributaries 

from the south, especially the Kantishna River. Several 

masses of sand dunes, which total 15,500 km2 (fig.16), 

were mapped by F. R. Collins (unpub. data, 1958) and 

Pewe, Wahrhaftig, and Weber (1966). The dunes are 
36 QUATERNARY GEOLOGY OF ALASKA 

Delta Glaciation 

;y::: :::::::::::::::::::, ;,:~~~ ::;:i!lilliiiliillll!i!lliiiiiiiliiiiiliiiiiiiiiiilili ::::::::::::::::::::::::::::: ...... . 

Loess 

mm Terminal moraine 

• Ventifacts 

Sand --dunes 

N 

1 

0 10 MILES 

5 0 5 10 KILOMETRES 

. ... .. . ... .. . .. .. ...... . ... ............. ......• 

5 

EXPLANATION 

ITIJITI 

Loess 

Terminal moraine 

• Ventifacts 

Sand -dunes 

N 

1 

0 10 MILES 

0 

Donnelly Glaciation 

FIGURE 16.-Distribution of loess, sand dunes, and ventifacts in the Big Delta area, Alaska, in the time of the Delta Glaciation (Illinoian) 

and Donnelly Glaciation (Wisconsinan) in relation to the glacial advance. From Pewe (1965b). 

well formed and have a local relief of 2-60 m. In most of 

the areas, they occupy the lowland at an elevation of100 

m; elsewhere, they lap up against the bedrock hills and 

are well formed up to 300 m above sea level. These 

stabilized dunes are dominantly longitudinal but locally have a parabolic form. Like others in interior 

Alaska, they are covered with spruce, birch, and aspen. 

Dune sand was blown by northeast winds from the glacial outwash plains of such rivers as the Tanana, Kantishna, Toklat, and others draining the Alaska Range. 

The dunes are covered with a few centimetres to a few 

metres of loess. 

An area of 500 km2 of gently rolling sand ridges 

occurs in the valley of the middle Kuskokwim River 

(Fernald, 1960). These dunes were derived from sediments of outwash plains and are related to the Selatna 

Glaciation (tables 2, 3). Fernald believed they are Wisconsinan and pre-Wisconsinan in age; however, the writer believes that they are Illinoian in age because of 

their association with the Selatna Glaciation. 

Vegetated, topographically rather subdued dunes, 

largely of the parah>lic type, occupy an area of 3,200 

km2 on high terraces in the lower Koyukuk River valley 

(Weber and Pewe, 1961). These dunes, formed by northeast winds blowing across outwash deposits, are probably pre-Wisconsinan in age (table 3). 

Dunes that are now stabilized were deposited by wind 

blowing across glacial outwash in the middle Kobuk 

River valley (Fernald, 1964). These dunes cover approximately 600 km2 of high river terraces and may have 

originated as early as late Illinoian time but no doubt 

were reactivated and enlarged during Wisconsinan 

time. 

WISCONSINAN AND POST-WISCONSINAN 

Well-formed parabolic and compound dunes of Wisconsinan age (table 3) cover approximately 1,150 km2 

on high terrace remnants of the upper Tanana valley 

(Fernald, 1965b). These dunes are 30-60 m high and are 

best developed in the vicinity of Northway and Tok (fig. 

15). Much of the sand blanket laps up on the bedrock 

hills to the north of the present river valley. The sand is 

gray to black and is derived from the wide glacial valley 

trains and outwash plains. The dune areas are much 

dissected and covered with a thin blanket of loess. 

Fernald (1960) described an area of about 800 km2 of 

well-formed parabolic dunes of Wisconsinan age on 

high terraces in the middle Kuskokwim River valley. 

About 600 km2 of eolian sand of Wisconsinan or greater 
EOLIAN DEPOSITS 37 

age covers most of the upland marginal to the Yukon 

Flats (Williams, 1962), and eolian sand of Wisconsinan 

age covers approximately 500 km2 of the Yukon Flats. 

Dunes are widespread in an area of13,000 km2 on the 

Arctic Coastal Plain west of the Colville River (fig. 15). 

In this region large areas of stabilized longitudinal, 

parabolic, and multicycle dunes and local areas of active 

dunes occur along most rivers and streams (Black, 

1951a, p. 92--96; Walker, 1967). Stabilized dunes generally have a longitudinal and parabolic form. Most of the 

longitudinal dunes are less than 1 km long, but the 

longest is about 2.4 km. These sand deposits are as 

much as 3-6 m thick. Black believes that these 

stabilized dunes were formed in Holocene time by 

northeast winds, the same direction as the present prevailing winds that formed the active dunes along the 

streams (Rickert and Tedrow, 1967). There have been 

many incidental observations on the sand dunes of 

northern Alaska during the geomorphic studies of the 

past 10 years (Rosenfeld and Hussey, 1958; Livingstone, 1954). 

Stabilized dunes cover a belt several miles wide on 

the east and northeast sides of St. Paul Island. The 

dunes are of the transverse type but have been slightly 

modified by secondary development of small paraboloid 

dunes prior to.complete stabilization. Dune crests stand 

3-5m above interdune areas. The dunes were formed by 

winds blowing from the east and northeast. The dunes 

cover a Pelukian (Sangamon) (table 3) shoreline and lie 

on pillow lavas ofSangamon age; they contain ice wedge 

casts, and a thick soil profile is developed on them. The 

sand contains abundant quartz and mica minerals that 

are not found in the basaltic lavas of St. Paul Island. 

These observations indicate that the dunes formed during the Wisconsinan Glaciation at a time when sea level 

was low, the Bering shelf exposed, and a large braided 

river-probably the Yukon-was delivering large 

quantities of sediment to a shoreline nearby (D. M. 

Hopkins, written commun., Feb. 3, 1968). 

VENTIFACTS 

Ventifacts, stones abraded by wind-blown sand were 

reported in Alaska (Smith and Mertie, 1930, p. 249; 

Black, 1951a, p. 108-109; Pewe, 1965b) but are not 

widespread. Well-developed ventifacts were reported by 

D. M. Hopkins (written commun., 1968) on Black 

Diamond Hill on St. Paul Island in the Pribilofs. These 

ventifacts, which are as much as 2m in diameter, are 

Holocene and are still being formed today. The most 

widespread and best developed ventifacts known in 

Alaska occur in the glaciated Big Delta area and in the 

adjacent unglaciated terrain in the middle Tanana valley. Here the ventifacts of both Illinoian and 

Wisconsinan age have been useful in interpreting the 

geologic history of the area (Pewe and others, 1953; 

Pewe and Holmes, 1964; Pewe, 1965b, p. 4 7-52) (fig. 16). 

LOESS 

HISTORY 

Loess probably is the most widely distributed sediment of Quaternary age in Alaska. It forms a blanket, 

ranging in thickness from a few millimetres to more 

than 60 m, that covers almost all areas that lie below 

altitudes of300-450 m. Thick deposits ofloess are most 

widely distributed in central and western Alaska (fig. 

17) (Pewe, 1968a). Most of the loess was deposited during Illinoian and Wisconsinan time, but wind-blown silt 

is still being deposited in many areas (Pewe, 1951a). 

The loess is of great economic importance because it 

forms the soils of the principal agricultural areas in 

Alaska (Bennett and Rice, 1919; Pewe, 1954, 1958b; 

Trainer, 1961). 

The wind-blown silt of Alaska was first described by 

Spurr (1898 p. 200-211), who applied the name !!Yukon 

silts" to deposits in the valleys of the Yukon River and 

its tributaries. For nearly 50 years, the origin of these 

silts was a matter of controversy; various workers argued for a fluvial origin, a lacustrine origin (Spurr, 

1898, p. 200-230; Prindle, 1913, p. 50; Eakin, 1916, p .. 

73, 1918, p. 45; Dorsh, 1934, p. 4), a marine and estuarine origin (Harrington, 1918, p. 30), or a residual 

origin (Wilkerson, 1932, p. 18-19). Although Tuck 

(1938) and Eardley (1938) correctly recognized that 

most of the silt was of wind-blown origin and Capps 

(1940) referred to eolian origin, Taber (1943, p. 

1471-14 79; 1953, p. 321-336; 1958) argued that the silt, 

including the reworked valley-bottom silt rich in organic material, was entirely the product of prolonged 

disintegration of local bedrock by frost riving. The writer, however, (Pewe, 1955) showed that the thick silt 

deposits of the Fairbanks district are of eolian origin, 

and Trainer (1961) and Hopkins (1963) confirmed the 

eolian origin of surficial silt blankets in the Matanuska 

Valley and central Seward Peninsula. 

ORIGIN AND PHYSICAL CHARACTERISTICS 

The loess of Alaska was blown from the vegetationfree flood plains of braided glacial rivers; consequently, 

loess is thickest near streams draining glaciated areas. 

At the present time, loess is being deposited most 

rapidly near the modern outwash streams. Loess has 

been deposited on ridges as high as 760 m above sea 

level, but most seems to have been deposited at altitudes of less than 450 m. A large part of the loess 

falling on summits and slopes of hills has been washed 

into valley bottoms to form thick deposits of bedded to ~ 

massive silt that is rich in organic debris. These deposits locally are called muck (Pewe, 1952a). The bed-
38 QUATERNARY GEOLOGY OF ALASKA 

ded character of the valley-bottom silt has been used as 

evidence to support hypotheses for the marine, lacustrine, and residual origin of loess. 

The loess in Alaska is similar in texture and color to 

loess elsewhere in the world. Typically, 80-90 percent of 

the particles are between 0.5 and 0.005 mm in size (fig. 

18). Particle size increases with decreasing distance 

from the river flood plains that constitute the source 

areas (Trainer, 1961; Pewe and Holmes, 1964; Davidson 

Point 

Hope 

and others, 1959; Lindholm and others, 1959, p. 49). 

Colors range from chocolate brown through tan to olive 

gray and neutral gray. Mineral and chemical composition reflect differences in bedrock composition of the 

glaciated valleys from which the particles were ultimately derived. Loess typically contains minerals that 

are not present in the bedrock of areas where it was 

deposited by the wind (Pewe, 1955; Hopkins, 1963). 

Textural studies by Dement (1962) indicated no im-

·.·.· . : .. :_: ... :··>:. ··:·-:· : 

0 50 100 150 Ml LES 

0 50 100 150 KILOMETRES 

FIGURE 17.-Loess deposits of Alaska. General thickness indicated by density Qf stippling. Compiled by T. L. Pewe, 1961. 
EOLIAN DEPOSITS 39 

100 

90 B - lkpikpuk River Q 

E - lmuruk Lake area E H Nulato 

J Manley Hot Springs h /u,/ 80 L Livengood AA /6 / 

0 Circle / /J y // y 

/~ / 1- Q Fairbanks / r / / 

z I I / / w 70 u Big Delta I I ;/ / ~ y - Medfra I w /I I AA- Palmer I a.. I/ /I I ~ I/ I 

60 I // >-" t/ / I ~ I // I /I w I lj ;f /I ::> 50 I 0 

w /; /; a: I f u. 

I w II /j 1 40 > I /; /t ~ I 1/ .J I tV /; ::> 30 I/ I 

:::E I I //; ::> I I. I I I u I I / 

20 I 1 I / I z I / I// /I 

10 !/ / / / / 

/' / I I / 

I I / / 

/ / / / 

0 

0.3 0.1 0.05 0.01 0.005 0.1 0.05 0.01 0.005 0.1 0.05 O.Q1 0.005 

DIAMETER, IN MILLIMETRES 

FIGURE 18.-Cumulative-frequency grain size curves ofloess from various locations in Alaska. Letters refer to locations in figure 17 (map). 

portant changes in clay content throughout the Fairbanks Loess. Thin textural bands high in fresh claysized particles occur parallel to the surface. The textural bands are not generic and not part of a soil deSource of data for specific localities cited 

[Symbols:.a.3, thickness in metres; mechanical analyses 

shown in figure 18 .• 15, thickness in metres] 

A-• R. F. Black (written commun., 1961). 

B-.a. P. V. Sellmann (oral commun., 1961). 

C- • R. F. Black (written commun., 1961). 

D-• D. M. Hopkins (unpub. data, 1961). 

E-.a. Do. 

f-e Do. 

G-e A. T. Fernald (written commun., 1961). 

H-.a. T. L. Pewe' (unpub. data, 1961). 

1-e Do. 

J-.a. T.L Pewe'(l955,p.708). 

K-e 1. R. Williams (written commun., 1961). 

L-.a. T. L. Pewe' (1955, p. 707). 

M-e J. R. Williams (written commun., 1961). 

N-e Do. 

0-.a. Do. 

P-e T. L. Pewe' (unpub. data, 1961). 

Q-.a. T. L. Pewe' (1955, p. 704). 

R- e Clyde Wahrhaftig and R. F. Black (1958, p. 87). 

S-• Do. 

T-. T. L. Pewe' and G. W. Holmes (1964). 

U-.a. T. L. Pewe' (1955, p. 707). 

V-e T. L. Pewe'and G. W. Holmes (1964). 

W-e T. L. Pewe' (unpub. data, 1961). 

X-. A. T. Fernald (1960, p. 247). 

Y-.a. A. T. Fernald (1960, p. 247-249). 

Z-e A. T. Fernald (1960, p. 247). 

AA-.a. F. W. Trainer (1961, p. 14). 

BB-e D. R. Nichols (written commun., 1961). 

CC-e A. T. Fernald (written commun., 1961). 

FIGURE 17.-Continued. 

velopment. They probably are depositional, the result of 

slight changes in source and deposition of loess. Frost 

action also has been suggested as a process involved in 

the concentration of clay. 

The carbonate content differs from place to place, 

both as a result of differences in the amount of carbonate rocks in the ultimate source areas and as a result of 

local differences in the history of postdepositional 

weathering. Near Fairbanks the freshest loess has no 

appreciable quantities of carbonate, but unweathered 

loess near Manley Hot Springs, 130 km to the west, 

effervesces vigorously upon application of hydrochloric 

acid. Most loess is highly micaceous, but Fernald (1960, 

p. 250) found very little mica in loess in the upper 

Kuskokwim River valley. The few mineral and chemical analyses of Alaskan loess that have been published 

are from the Fairbanks area (Pewe, 1955), Palmer and 

Big Delta (Stump and others, 1959, p. 17; Lindholm and 

others, 1959, p. 53), the upper Kuskokwim River valley 

(Fernald, 1960, p. 250), and the Imuruk Lake area of the 

Seward Peninsula (Hopkins, 1963). 

As is typical of loess throughout the world, Alaskan 

loess is massive, cliff forming, and locally perforated 

with swallow-nesting tunnels. Only in some areas of 

Alaska does the loess contain fossils of air-breathing 

mollusks. In the great loess areas of the interjor of 

Alaska, especially the Tanana and Yukon valleys, the 
40 QUATERNARY GEOLOGY OF ALASKA 

loess, though examined in hundreds of exposures, has 

yielded fossils of air-breathing snails in only the very 

young loess near Big Delta (Pewe, 1955) and in loess of 

probable Wisconsinan age near Tofty (Repenning and 

others, 1964). However, the loess near Chitina and Gulkana in the Copper River Basin contains many pulmonate snails, as does the loess near Fort Hamlin in the 

middle Yukon River valley (Williams, 1962). In the 

Kotzebue Sound area, air-breathing and aquatic snails 

and clams were collected from the deposits of thaw lakes 

that existed during loess deposition (McCulloch and 

others, 1965). 

DISTRIBUTION AND THICKNESS 

The extent of loess in Alaska and thickness data at 

selected localities are presented in figure 17. The thickest loess known in Alaska is north of the Tanana River 

near Fairbanks, where a blanket 61 m thick covers the 

top of Gold Hill (Pewe, 1955). Greater thicknesses of 

silty sediments (as much as 95 m) occur in the bottoms 

and lower slopes of small valleys in the Fairbanks area, 

but these represent deposits reworked from adjoining 

slopes. Deposits 3-12 m thick occur along the entire 

north side of the Tanana valley and on both sides and in 

the middle of the lower Yukon River valley (Eardley, 

1938). Loess is thick adjacent to the Yukon Flats (Williams, 1955, p. 125; 1962) and the upper Kuskokwim 

valley (Fernald, 1960, p. 24 7) (fig. 17). Many metres of 

wind-blown silt exist along the central Copper and 

lower Chitina valleys and near Palmer (Stump and 

others, 1959). Loess more than 1.5 m thick covers about 

three-quarters of the area of Seward Peninsula (Hopkins, 1963, pl. 3). The major river valleys on the Arctic 

Slope are flanked by loess that is generally many metres 

thick, but the loess blanket thins considerably immediately away from the rivers (Smith and Mertie, 

1930, p. 249; Black, 1951a, p. 92; Detterman and others, 

1963, p. 304-305). Loess on the Pribilofislands (outside 

area mapped in fig. 17) averages 15 em thick, and some 

slopes on St. George Island have 2m of loess. This loess 

probably originated as silt blown from the extended 

flood plains of the Yukon and Kuskokwim Rivers across 

the Bering platform in Illinoian and Wisconsinan times 

(D. M. Hopkins, unpub. data, 1965; S<(holl and others 

1968, p. 320). Deposits a few centimetres o a few metres 

thick are known locally elsewhere in A'iaska (Black, \ 

1951a; Muller, 1955, p. 132; Karlstrom, 1~55, p. 133; 

Hoare and Coonrad, 1959; Coonrad, 1957; Hoare and 

Condon, 1971; Chapman and others, 1971) (fig. 17). 

It is interesting to note that loess is said to be absent, 

or nearly so, from St. Lawrence Island. J. M. Hoare, W. 

H. Condon, D. S. McCulloch, and D. M. Hopkins (written commun., 1968) confirmed this, for example, in the 

vicinity of Savoonga on the north .side of the island. 

These observations perhaps suggest that the position of 

the major rivers across the Bering shelf in glacial times 

may not have been close to the island. This suggestion 

should be added to the growing body of evidence shedding light on the environment and glaciation of the 

Bering shelf, a subject of current controversy and investigation. 

A thin layer (about 10 em) of loess of Holocene age 

seems to be present near Barrow, but loess of 

Wisconsinan time apparently is lacking. Brown (1965a) 

believed that the Holocene silt is loess and was derived 

from drained lake basins; however, Carson (1968, p. 25) 

stated the silt does not represent uwind-laid deposit, but 

simple reworked Gubik sediments winnowed from 

lighter weight organic fines by normal wave processes." 

Detailed studies were made in some localities regarding the thicknesses of loess. Hundreds of measurements 

were taken in the Fairbanks area (Pewe, 1955, 1958b; 

Pewe and Rivard, 1961; Williams and others, 1959), and 

isopach maps were made for the Matanuska Valley 

(Trainer, 1961) and for the lower reaches of the Delta 

River valley (Davidson and others, 1959; Pewe and 

Holmes, 1964). In all instances, the loess is thickest 

near the rivers. 

STRATIGRAPHY 

The periods of greatest loess deposition in Alaska 

correspond to glacial maximums. During these periods 

the source areas, vegetation-free flood plains and outwash plains, were at their greatest extent. In the periglacial areas, such as the Tanana, Yukon, and Kuskokwim valleys, repeated glacial advances with related 

wind conditions and source areas favorable for loess 

deposition have created multiple loess blankets (table 

3) (Pewe, 1955; Fernald, 1960; Pewe, 1965b). At Cape 

Deceit near Deering (pl. 1) on the south shore of Kotzebue Sound, Guthrie and Matthews (1971) recorded 

thin loess layers of pre-Illinoian, Illinoian, Wisconsinan, and Holocene age. This is the oldest loess reported in 

Alaska. 

Detailed stratigraphic studies of loess are limited to 

the Seward Peninsula and adjoining a;rea (Hopkins, 

1963; McCulloch and others, 1965; Guthrie and Matthews, 1971) (fig. 19) and to the central Yukon-Tanana 

Upland (Pewe, 1952a, 1955, 1958b). 

One of the most interesting records of Quaternary 

events in Alaska comes from an interpretation of the 

loess deposits and underlying creek gravel near Fairbanks (table 3). Extensive exposures created by placer 

mining operations have revealed a complicated history 

of loess deposition alternating with periods of fluvial 

erosion. 

In Illinoian time, the hills were blanketed with loess 

derived from the flood plain of the Tanana River and 

glacial outwash plains south of the Fairbanks area. 

Much of this windblown silt was retransported to creek 

valley bottoms, incorporated much organic debris, in-
EOLIAN DEPOSITS 41 

w 

ice wedges 

Holocene alluviu md;:::~:.k--=--- -=--=--,----~ 

-

E 

Early Holocene beaver dams -__:-- > and beaver pond sediments, 

Wisconsinan loess, thaw lake 

sediments, and inactive ice 

wedges 

r--::;;:;:;!;.A\-:'~-::-1} ~c~r:~dfg';~:~t:nd 

~....,-""-ji.I:;;;;:z~---.,....-ff~---,-.,,.-,-----,----.,....-~~c---~...-----..-1 < buried forest, and ice wedge >

Sangamon weathering profile, 

Sangamon marine { 

deposits cut by 

ice wedge casts 

casts 

Late-Illinoian loess, thaw lake 

deposits, and flood plain 

sediments 

FIGURE 19.-Diagrammatic cross section of Baldwin Peninsula, Alaska, showing Quaternary deposits. From 

McCulloch (1967). 

eluding vertebrate remains, and became perennially 

frozen. Indications of the antiquity of this loess are (1) 

its position unconformably beneath a younger silt deposit, the base of which is older than 56,900 years 

(Matthews, 1968b, 1970) (fig. 20), (2) joints that were 

Bedrock 

heavily stained by iron oxide and cemented before the 

deposit became perennially frozen, and (3) evidence 

from fossil ice wedges that the loess, once frozen, was 

thawed, then again perennially frozen. 

This period of loess deposition was followed by an 

0 

0 

HORIZONTAL SCALE 

Inactive 

altiplanation 

terraces 

500 FEET 

100 METRES 

VERTICAL EXAGGERATION X4 

FIGURE 20.-Schematic composite cross section of a creek valley in central Alaska illustrating the relations of the Quaternary silt and 

gravel deposits. 
42 QUATERNARY GEOLOGY OF ALASKA 

TABLE 4.-Rates of deposition of Holocene loess along rivers in central Alaska 

Measured Duration of Rate of 

thickness accumulation accumulation 

Area Location Source (metres) (years) (mm per yr) 

East side of Adjacent to east side of Pewe, Hopkins, and 2.4 1950±150 1.14---1.33 

Delta River. river flood plain 32-80 Giddings (1965, p. 362). (L-163K) 

km south of Big Delta 4650±250 .78-.86 

on terraces and alluvial Reger, Pewe, Hadleigh- 3.8 (L-137Q) 

fans. West, and Skarland 7000±275 1.93--2.07 

(1964 p. 95-96). 14.0 5900±250 .85-.92 

5.2 {1-646) 

3.7 2300±180 1.49-1.75 

(1-647) 

North side of Adjacent to north side of Pewe (1965b, p. 48-49, ( 1) 0.61 2565±290 .21-.27 

Tanana River. river near junction with p. 53). (GX0254) 

Delta River. (2) 1.2 8040±190 .15 

(1) On southeast facing (GX0255) 

slope 1 km from river. 

(2) On low terrace at 

edge river. 

Fairbanks ___ _____ Gold Hill 70 m above and Pewe (1965a, p. 16, 20). 6.0 4020±200 1.40--1.57 

5.4 km north of the 

present Tanana River. 

erosional period when most of the retransported silt in 

creek valley bottoms and some of the loess on the hillside slopes and hilltops were removed. The loess was 

deeply gullied, and block slumping occurred. Long 

parallel gullies more than 10 m deep and 180 m long 

formed on almost all loess-covered slopes in the Fairbanks area. Permafrost thawed and perhaps disappeared during this warm erosional interval (Pewe, 

1975). 

In Wisconsinan time, additional loess was deposited 

on the uplands, and much loess was retransported to 

valley bottoms to form a carbonaceous, fetid, perennially frozen deposit, locally termPd ~~muck" (fig. 20). 

This valley-bottom facies of loess of Wisconsinan age is 

3-46 m thick and contains abundant vertebrate and 

plant fossils, including partial carcasses of vertebrates 

that were entombed in the silt and perennially frozen. 

The most common vertebrate remains in the muck of 

Wisconsinan age, in order of their abundance, are those 

of bison, mammoth, and horse. The retransported silt 

(valley-bottom facies) of Wisconsinan age contains 

many ice wedges 0.3-3 m wide and as much as 10m 

long. 

The gullies and ridges of pre-Wisconsinan age cut in 

loess of the middle and upper slopes in the Fairbanks 

area were rounded and subdued by the blanket of loess 

deposited over these undulations in Wisconsinan time. 

About 10,000 years ago a warming interval occurred 

that caused the permafrost table to be lowered 2-3 m 

and the top of the ice wedges to melt down about 0.3-3 

m. Loess and the valley-bottom facies (retransported 

silt) of the loess that has been deposited since and during the thawing lie unconformably over the thaweddown flat-topped ice wedges and retransported silt of 

Wisconsinan age (fig. 20). This Holocene silt is 0.3-8 m 

thick, and all but the upper 1.5. m is perennially frozen 

(W-183) 

(Pewe, 1975). The silt contains no bones of extinct animals. 

On the hilltops, the loess deposited in Illinoian, Wisconsinan, and Holocene time constitutes one relatively 

uniform loess layer, and it has not yet been possible to 

differentiate this loess into layers of separate ages. All 

the upland loess is grouped together under the name 

Fairbanks Loess (fig. 20). 

RATE OF DEPOSITION 

Loess is still being deposited along most braided glacial streams in Alaska, most notably adjoining the 

Delta River (fig. 21) (Pewe, 1951a), along the Knik and 

Matanuska Rivers (Tuck, 1938; Trainer, 1961), and 

near the junction of the Tanana and Yukon Rivers. 

Information on the rate of eolian silt accumulation can 

be obtained in some of these areas. The 7.2 m of silt 

measured on the top of Boden berg Butte in the western 

Matanuska Valley near Palmer (Stump and others, 

1959, p. 9), for example, is entirely post-Wisconsinan in 

age. Measurements of loess thicknesses and radiocarbon dating of stumps and logs in the loess have yielded 

rates of loess accumulation in a few places in central 

Alaska (table 4). Assuming no erosion of the accumulating loess during the measured interval, the rate of accumulation is 0.2-2.0 mm per year. The writer considers this to be a valid figure because the areas of accumulation are flat to almost flat and heavily vegetated. 

SUMMARY 

Most of the low-lying areas of Alaska (except perhaps 

the southeastern part) are covered with either sand 

dunes or loess from a few millimetres to 100 m thick. 

Almost all these deposits are associated with glaciations. Most sand dunes are stablized and have not received detailed study. 
EOLIAN DEPOSITS 43 

Alaska has one ofthe largest, if not the largest, areas 

of loess in North America and perhaps contains the 

thickest deposits. The loess has been studied in some 

detail, and valuable stratigraphic sections of Illinoian, 

Wisconsinan, and Holocene loess are known in central 

and western Alaska. The sections, especially in central 

Alaska, illustrate a detailed history of deposition, retransportation, and permafrost and a record of mammalian remains. 

The rate of loess deposition in North America has 

~long been sought, and perhaps the best place to find the 

answer is in association with Holocene glaciations in 

Alaska. Studies here indicate loess is accumulating at 

0.2-2.0 mm per year. 

PERMAFROST AND PERIGLACIAL DEPOSITS 

Extensive areas of Alaska are underlain by deposits 

that are the result of mass wasting or frost action in a 

FIGURE 21.-0blique aerial photograph of clouds of silt transported by wind from the Delta River flood plain, central Alaska. View looking 

north. Photograph by U.S. Navy, 1948 (Pewe, 1951a). 
44 QUATERNARY GEOLOGY OF ALASKA 

rigorous climate-a climate widely known as periglacial. Lozinski (1909) introduced the term (!periglacial" 

for the concept of a cold climate outside of the glacial 

border; specifically, the term (!periglacial" referred to 

the area that bordered the continental ice sheet, its 

climate, and features developed in this rigorous environment. 

The term (!periglacial" has not been accepted by all, 

although the concept is now firmly entrenched (Tricart 

and Cailleux, 1967). Such terms as ((subnival," ((subglacial," and ((subgelid" and ufrost-climate" have been suggested, but the term ((periglacial" remains most widely 

used. No single definition agreeable to everyone studying the periglacial environment has been formulated, 

owing to differences of opinion concerning the climate of 

the periglacial zone. For instance, Zeuner (1945) restricted the periglacial zone to that area where the 

annual air temperature is -2° C or colder. Others stated 

that permafrost is not actually necessary for a periglacial environment and that such a climate could include 

regions where it is absent but where a considerable 

number of freezing and thawing cycles occur annually. 

Although exact definition of the periglacial environment has not been developed, workers agree that it has 

a rigorous climate. The writer consider~ all areas of 

existing permafrost to be in the modern periglacial 

zone. 

The periglacial environment is characterized by frozen ground and intense frost action in fine-grained sediments and considerable sorting of fine and coarse materials. Therefore, mechanical weathering is accelerated, and ice is abundant in perennially and seasonally 

frozen ground. Local sorting of sediments is com:mon, 

producing small-scale patterned ground. Water is concentrated in fine-grained surficial sediments by ice segregation. This concentration of water, when released, 

and the impeded infiltration of surface waters owing to 

impervious frozen subsoil aids in downslope mass 

movement of debris. Growth of large masses of ground 

ice occurs in permafrost with the formation of tundra 

polygons and pingos. 

PERMAFROST 

Permafrost, the most widespread phenomenon of the 

periglacial climate, is defined as a thickness of soil or 

other superficial deposits, or even bedrock, which has 

been colder than ooc for 2 years or more; it is defined 

exclusively on the basis of temperature, irrespective of 

texture, degree of induration, water content, or 

lithologic character (Muller, 1945, p. 3). Permafrost, 

perennially frozen ground (Mozley, 1937; Taber, 1943), 

or vechnaya merzlota1 (Sumgin, 1927) is widespread in 

I This tenn means "eternal frost" and is being replaced in the recent Russian literature by 

"mnogoletnemerzlyy grunt" which means "perennially frozen ground." 

the northern part of the northern hemisphere (fig. 22), 

as well as in Antarctica. About 20 percent of the land 

area of the world is estimated to be underlain by permafrost (Muller, 1945, pl. 1; Black, 1954, p. 842; Pewe, 

1966c, 1969a, fig. 1; Ferrians and others, 1969). 

Perennially frozen ground is present throughout 82 

percent of Alaska (fig. 23) but is more widespread and 

extends to greater depths in the north than in the south 

(Ferrians, 1965a, b, 1966). Permafrost in Alaska has 

long been divided arbitrarily into three generalized 

zones: the continuous, discontinuous, and sporadic 

zones (Black, 1950, 1954; Pewe, 1954; Hopkins and 

others, 1955; Pewe and Paige, 1963; Wahrhaftig, 1965). 

The terms refer to lateral continuity of permafrost. This 

threefold division has followed the manner of mapping 

employed in the U.S.S.R., where the divisions are 

further qualified by the temperature of permafrost 

(Sumgin and others, 1940). (See Baranov (1956) for a 

later, more refined division.) Inasmuch as the boundaries between the discontinuous and the sporadic permafrost zones are difficult to place without temperature 

information, and inasmuch as thermal data for permafrost in Alaska are still limited, the writer uses only two 

permafrost zones in Alaska (Pewe, 1966b), the continuous and the discontinuous. A similar classification has 

been followed in Canada for the same reason (Jenness, 

1949; R. J. E. Brown, 1960, 1966, 1969, 1970). The 

discontinuous zone as used here includes the discontinuous and sporadic zones of the earlier classification. 

In the continuous zone of the northern part of Alaska, 

permafrost is almost everywhere present and extends to 

a calculated depth of 405 m, 12 km south of Barrow 

(Brewer, 1958, p. 19), and to 650 m at Prudhoe Bay 

according to Stoneley (in Lachenbruch, 1970b, p. 

J3-J4). In this area, away from large bodies of water, 

permafrost at a depth of 15-25 m is colder than -5°C 

(15-25 m is the maximum depth to which appreciable 

annual temperature fluctuations occur). 

Although permafrost was known to exist offshore 

northern Alaska and Yukon Territory, only recently 

has extensive work been undertaken to investigate its 

extent and origin (Shearer and others 1971; MacKay, 

1972b; Lewellen, 1973). One of the pressing problems 

for future work is the study of offshore marine permafrost in North America. 

Southward, in the discontinuous permafrost zone of 

Alaska, permafrost thickness decreases, and unfrozen 

areas are more and more abundant until, near the 

southern boundary (fig. 23), only rare patches of permafrost exist. The southern boundary of permafrost as 

shown in figure 23 is placed to include relict permafrost 

as well as small areas of permafrost existing because of 

current favorable microclimatic conditions. This boundary lies a short distance south of the ooc mean annual 
EOLIAN DEPOSITS 45 

180° 

50° 

400 

EXPLANATION 

Zone of continuous permafrost 

Zone of discontinuous permafrost 20o 

50° 

140° 100° 

FIGURE 22.-Distribution of permafrost in the northern hemisphere. 

Sources: Alaska, Pewe (1969a); Canada, Brown (1969); Greenland, 

Weidick (1968); Iceland, Thorleifur Einarsson, Iceland Industrial 

Research and Development Institute, written commun., 1966; 

Norway, B. J. Andersen, University of Bergen, written commun., 

air2 isotherm, an isotherm generally thought to be now 

2 In this report the air temperature referred to, unless otherwise stated, is that measured at 

a height of 1.5 m above the ground, the standard height for the U.S. Weather Bureau 

recording stations. 

1966; H. Svensson, Lund University, oral commun., 1966; Sweden, 

Rapp and Annersten (1969); Mongolia and China, Shumskiy, 

Schvetzov, and Dastavolov (1955); U.S.S.R., Baranov (1956). From 

Pewe (1969a). 

at the southern boundary of permafrost. The temperature of permafrost at a depth of 15-25 min this zone 

ranges from -5°C in the northern part of the zone to 

approximately ooc farther south. 
46 QUATERNARY GEOLOGY OF ALASKA 

176" 

EXPLANATION 

PERMAFROST-Data in metres 

122 • Thickness, depth to base 

• Thickness unknown 259-299. 

18+ • Minimum thickness, base unknown 

66° 12-15• Relict permafrost, ground frozen 

between depths shown 

·6.5oC • Temperature of permafrost 

at 15 to 25-metre depth 

OTHER DATA 

Permafrost zone boundary 

Approximate position of 0°C 

mean annual air-temperature 

isotherm 

Point 30+ 

Hope 

288 ·~~~oc 

.38+ 

18+ •• 9 

244+. 

11 11 0 • 231 

0 k. s 

24. .55 

16 

0 50 100 150 MILES 

0 50 100 150 KILOMETRES 

FIGURE 23.-Permafrost map of Alaska. Compiled by T. L. Pewe and L. R. Mayo. Permafrost thickness from map compiled by J. R. 

Williams, published and unpublished sources. Ground temperature at Glenallen measured at a depth of 6 m. 

The maxim urn thickness of permafrost in Alaska 

ranges from an estimated 650 min the north to a few 

metres on the Alaska Peninsula in the south (fig. 23). 

Permafrost has not been found in the Aleutian Islands 

or in southeastern Alaska. North of the Brooks Range, 

thickness ranges from 180 to 650 m, on the basis of a few 

deep test holes drilled for petroleum investigations. At 

Prudhoe Bay on the north coast of Alaska, holes drilled 

for petroleum penetrated permafrost to depths of about 

650 m (Stoneley, 1970; Howitt and Clegg, 1970). 

Lachenbruch (1970b) noted that this is 50 percent 

deeper than at Barrow (fig. 23) and 100 percent deeper 

than at Cape Simpson, although all three localities probably have similar mean surface temperatures. He explains this difference as the result of ((an increased 

proportion of siliceous sediments from Simpson to Bar-
EOLIAN DEPOSITS 47 

row to Prudhoe, which would cause a corresponding 

increase in conductivity and decrease in geothermal 

gradient." Maximum thickness of permafrost in central 

and southwest Alaska ranges from a few metres to 180 

m. Borings are numerous but mostly limited to valley 

bottoms and lowlands. 

No attempt has been made to map isopachs of permafrost thickness in Alaska because of the almost complete lack of information in the mountainous areas. 

This lack of information precludes any but the broadest 

generalizations at this time. Bateman and McLaughlin 

(1920) record permafrost in the Kennecott mine in the 

Wrangell Mountains. This record, plus one from Keno 

Hill (Wernecke, 1932) at an elevation of 1,500 m, 150 

km east of Dawson in adjacent Yukon Territory, 

Canada, constitute about the only information of permafrost at great depth in mountainous areas in Alaska 

and adjacent Canada. 

The temperature of permafrost is one of the most 

critical quantitative parameters necessary to evaluate 

not only the existence of frozen ground at depth, but also 

to calculate the thicknesses, mean annual air temperature, and even history of permafrost and geomorphic 

changes on the surface (Lachenbruch, 1962). Accurate 

mapping of permafrost is possible only with abundant 

temperature data. Temperature data in northern 

Alaska (fig. 23) were collected by the U.S. Geological 

Survey at Cape Simpson (fig. 24), Barrow, the 

Shaviovik River area (Brewer, 1958), and at Ogotoruk 

Creek near Point Hope (Lachenbruch and others, 1961). 

Lachenbruch (oral commun., 1962) provided data on the 

permafrost at Umiat. The coldest permafrost temperature recorded in Alaska is -10.69C, 12 km south of 

Barrow (Brewer, 1958, p. 20). 

Permafrost temperature in central Alaska near Fairbanks is -0.9°C at a depth of 1&-25 m in frozen silt 

(Pewe and Paige, 1963, p. 376). In the Copper River 

Basin the temperature of permafrost at a depth of6 min 

undisturbed ground along the Richardson Highway is 

-1.5°C (Greene and others, 1960, p. B141; Williams, 

1970, fig. 10). 

Permafrost forms when more heat leaves the ground 

than enters and when a temperature below ooc is produced continuously for 2 years or more. This heat balance is delicate, and the ~~cold reserve" grows or shrinks 

as heat flow is modified by either climatic changes or by 

changes at the interface between permafrost and the 

atmosphere-that is, changes in the vegetation, snow, 

and characteristics of the upper layer of thawed ground. 

Inasmuch as permafrost is defined on the basis of 

temperature alone, any material, whether it is silt, 

sand, gravel, peat, refuse piles, or bedrock, as long as it 

has been colder than oac continuously for more than 2 

years, is termed permafrost. In some places, permafrost 

o~~rl~~~----~~----~T--~r~ 

100 1-

C/) 

~ 200 IIw 

~ 

0 

0 

0 

0 

0 

00 

0 

I 

I 

I 

I 

I 

o I 

0 

-

-

o I 

oo I 

t 300 :----------;o~t~;;,-o~,R----------------~ 

~ permafrost I 0

00 

I o 

I o 

I 0o 400 - 1-

I 0o 

i

l 00 

sooL_~------~------~-------~L--~--~~ -12 -6 0 +6 +12 

TEMPERATURE, IN °C 

FIGURE 24.-Geothermal profile for Cape Simpson well 28, northern 

Alaska; data for May 22, 1953, after well had essentially returned 

to thermal equilibrium. Modified from Brewer (1958, p. 20). 

has been formed by artificial freezing, as under coldstorage rooms in England (Cooling and Ward, 1944; 

Ward and Sewell, 1950) and in Canada (Hardy and 

D' Appolonia, 1946). Oddly enough, perenially frozen 

ground was created by artificial means in unfrozen loess 

to prevent landsliding in placer mining operations near 

Fairbanks, Alaska (J.D. Crawford, oral commun., Feb. 

6, 1955). 

Lane (1946, p. 401-402) stated that the temperature 

of permafrost below the depth of measureable seasonable change is approximately the same as the local mean 

annual air temperature if the permafrost is in equilibrium with the existing climate. Redozubov (1946, p. 2) 

stated that the mean annual air temperature is always 

slightly lower than the local permafrost temperature, in 

some places several degrees lower (Brewer, 1958, p. 22). 

Actually, at a. depth where the seasonal temperature 

fluctuations are minimal, the average temperature of 

permafrost is close to the average temperature of the 

ground surface; however, it is 2-6°C warmer than the 

mean annual air temperature determined from U.S. 

Weather Bureau recording stations (Lachenbruch, 

1970b). Temperature records of the U.S. Weather 

Bureau are the only ones readily available over widespread areas and therefore must be used in constructing 

maps of climatological data such as figure 3. The southern boundary of permafrost roughly approximates the 

position of the oac mean annual air isotherm. This 
48 QUATERNARY GEOLOGY OF ALASKA 

supports the suggestion that most permafrost is a product of the present climate. Redozubov (1946, p. 10) 

showed that it would take many thousands of years to 

form 700 m of permafrost. Permafrost no longer in contact with seasonal frost may be a holdover from earlier 

colder climates. 

Many temperature profiles show that permafrost is 

not in equilibrium with the present climate at the sites 

of measurements (Lachenbruch and others, 1962; 

Lachenbruch and Marshall, 1969; Lachenbruch, 1968, 

p. 835). Lachenbruch, Greene, and Marshall (1961, 

1966) stated, for example, that only 260m of the 356m 

of permafrost observed in a drill hole in Ogotoruk Valley, 35 km southeast of Point Hope (pl. 1), would exist if 

present surface conditions were to persist for several 

thousands of years. ttin a sense, about 25 percent of the 

permafrost beneath Ogotoruk Valley is a product of an 

extinct climate" (Lachenbruch and others, 1966, p. 158). 

In a hypothetical example in central Alaska near 

Fairbanks, the temperature of permafrost below the 

zone of annual change is -1 oc (fig. 25). By extrapolation 

downward along the known curve of the geothermal 

gradient, it is possible to calculate that the thickness of 

permafrost is about 60 m. This agrees with known 

thicknesses measured in the Fairbanks area. The mean 

annual air temperature in the region is -3°C, 2.5°C 

colder than the temperature of permafrost. 

As the climate becomes colder or warmer (mean annual air temperature remaining below 0°C), the temp- r 

erature and thickness of the permafrost change accordingly. The base level of permafrost fluctuates but not 

the top (the permafrost table), providing that the active 

layer, vegetation, and snowfall do not change. If the 

mean annual air temperature rises above 0°C, the top of 

the permafrost will be lowered by thawing. The rate at 

which the base or top of permafrost changes depends not 

only on the amount of climatic fluctuation, but also on 

the_ amount of ice in the ground. Frozen silt generally 

thaws more slowly than gravel because it generally 

contains more ground ice. Many unfrozen areas in the 

discontinuous zone of permafrost in Alaska (fig. 23) 

consist of sand and gravel, and the nearby perennially 

frozen areas consist of silt (Pewe and others, 1969). 

GROUND ICE 

Ice content is probably the most important feature of 

permafrost affecting human activity in the north. Of 

equal importance is the fact that it provides evidence 

concerning past climates beyond the range possible by 

geothermal calculations. Ice in the perennially frozen 

ground varies in size and shape and has definite distribution characteristics. The origin of ground ice constitutes one of the most interesting and controversial 

problems connected with permafrost. The writer groups 

TEMPERATURE, IN °C 

-2 -1 0 +1 +2 +3 +4 +5 

I I I I I I I I or-~--~-~~~--~~rcs~~~s~o~na~l~fr~o~st~~--~~ 

2r-~~-----4------~~~~~~--~~--~ 

(I) 

~ Minimum mean 

t- monthly temperatur 

~ 25 

~ 

I 

.... 

ll.. 

w 

Q 

J Permafrost table 

Mean annual ground termperature 

I 

I 

Maxim1um mean monthly temperature 

I ---l----~-----------

Level of zero annual 

1 amplitude 

I 

I 

I 

I 

I 

Geothermal g-radient 

FIGURE 25.-Hypothetical example showing temperature profile and 

thickness of permafrost in central Alaska. 

ground ice into five main types: (1) pore ice, (2) segregated or Taber ice, (3) foliated or ice wedge ice, (4) pingo 

ice, and (5) buried ice. 

Pore ice is defined as ice that fills or partly fills pore 

spaces in the ground. It forms by freezing pore water in 

situ with no addition of water. The ground contains no 

more water in the solid state than it could hold if the 

water were in the liquid state. Black (1954) termed 

frozen ground with such ice as undersaturated or saturated. 

Segregated or Taber ice is described as ice seams, 

lenses, or layers generally 1-100 mm thick that grew in 

the ground by drawing in water as the ground became 

frozen. Taber (1929, 1930) was a pioneer in demonstrating this phenomenon, although Beskow (1947) worked 

actively in this field at about the same time. Although 

the idea that water must be supplied for an ice crystal to 

grow is generally accepted, not everyone agrees on how 

this is accomplished (Jackson and Chalmers, 1956; 

Jumikis, .1955; Cass and Miller, 1959; Winterkorn, 

1943). 

Segregated ice has been referred to by various 

terms-ice seams, ice segregations, ice gneiss (Taber, 

1943), and sirloin-type ice (Higashi, 1958), among 

others. The writer has long used the term ttTaber" ice, 

originally suggested to him by A. H. Lachenbruch, U.S. 

Geological Survey, for ice segregations in the ground. 

Pore ice and Taber ice occur both in seasonally frozen 

ground and in permafrost. Black (1954) referred to permafrost composed of this type of ice as being supersaturated because it contains more water in the solid state 
PERMAFROST AND PERIGLACIAL DEPOSITS 49 

than the ground could possibly hold if the water were in 

the liquid state. 

Foliated ground ice or wedge ice is the term given to 

large masses of ice that grow in thermal contraction 

cracks in permafrost. 

Pingo ice is clear or relatively clear ice that occurs in 

permafrost in nearly horizontal or lens-shaped masses 

3-15m in diameter. It evidently originates from ground 

water under hydrostatic pressure (Muller, 1963). 

Buried ice in permafrost includes buried sea, lake, 

and river ice and recrystallized snow. Buried blocks of 

glacier ice in a permafrost climate would also fall into 

this category. 

Small ice segregations are the least spectacular and 

yet one of the most extensive types of ground ice. They 

occur in both seasonally and perennially frozen ground, 

and as grains, granules, films, lenses, layers, pods, 

dikes, and irregular masses that range in diameter from 

less than 1 mm to 4 em. The freezing of ground and 

formation of small, clear ice segregations has received 

much study from engineers and geologists interested in 

ice growth and its effect on engineering structures. As 

population increases in the far north, the effects of the 

growth of ground ice on construction have been the 

subject of growing concern (Beskow, 1947; U.S. Army 

Corps ofEngineers, 1946, 1947, 1949, 1954, 1956; Johnson, 1952; Reed, 1969). 

When considering the subject of ground ice, the question if generally raised as to how much ice actually 

exists in the ground. Because such information would 

be interesting and valuable from a historical standpoint 

as well as essential in solving engineering problems 

posed by permafrost (Lachenbruch, 1970a), the question is being considered in an ambitious attempt to 

make an inventory of all perennial ice and snow masses 

on and beneath land surfaces of the earth as a project of 

the International Hydrological Decade (Fritz Muller, 

unpub. data, 1968). 

Estimates the volume of worldwide ground ice range 

from 0.2 to 0.5 million km3 , less than 1 percent of the 

total volume of the earth (Shumskiy and Vtyurin, 1966; 

Shumskiy and others, 1964, p. 433). Estimates of 

ground ice in Alaska are sorely needed and represent a 

challenging project. Brown (1967c) made a first approximation of the ground ice inventory for the Arctic 

Coastal Plain (pl. 1). The plain lies in the continuous 

permafrost zone (fig. 23) and represents a fairly uniform 

set of geologic, geomorphic, and permafrost conditions. 

An underground ice inventory for other regions of 

Alaska would be more difficult owing to discontinuities 

in the permafrost and the presence of large ice masses 

with no physiographic expression. 

On the basis of an examination of ice in the ground in 

many bore holes in the Barrow area (Brown, 1965b, 

1966a, b, 1967b, 1969a, b; Brown and Johnson, 1965; 

Sellmann and Brown, 1963, 1965; Sellmann and others, 

1964, 1965) and the extrapolation of information from 

the bore holes to the rest of the coastal plain by use of 

aerial photographs and geologic maps, it is estimated 

(Brown, 1967c) that 10 percent by volume of the upper 

3.5 m of permafrost on the coastal plain is composed of 

ice wedges (foliated ground ice); Taber ice is the most 

extensive type of ground ice, in places representing 75 

percent of the ground by volume. In measurements 

made by the writer in the Fairbanks area, samples of 

frozen ground may contain as much as 200-1,000 percent ice by weight (Pewe, 1958b; Williams and others, 

1959). For purposes of computation, Brown (1967c) assumed that no segregated ice exists below 8 m and that 

the only ground ice present is pore ice. This is probably 

correct for most areas, but especially in syngenetic ice 

areas, the writer has seen deposits below a depth of8 m 

with ice seams 1 em thick and buried ice 2 m thick. 

Brown calculated that the pore and Taber ice content in 

the depth between 0.5 and 3.5 m (surface to 0.5 m is 

seasonally thawed) is 61 percent and between 3.5. and 

8.5 m is 41 percent by volume. The total amount ofpingo 

ice is less than 0.1 percent of the permafrost. The total 

amount of perennial ice in the permafrost of the Arctic 

Coastal Plain is estimated to be 1,500 km3 and below 8.5 

m most of that is present as pore ice. 

ICE WEDGES 

The most conspicuous and controversial type of 

ground ice in permafrost is the large ice wedges or 

masses characterized by parallel or subparallel foliation structures. Most foliated ice masses occur as 

wedge-shaped, vertical, or inclined sheets or dikes 1 em 

to 3m wide and 1-10m high where seen in transverse 

cross section (fig. 26). Some masses seen on the face of 

frozen cliffs may appear as horizontal bodies a few centimetres to 3m in thickness and 0.5-15 m long. The true 

shape of these ice wedges can be seen only in three 

dimensions. Ice wedges are parts of a polygonal network 

of ice enclosing polygons or cells of frozen ground 3-30m 

or more in diameter. 

The network of foliated ice in the ground generally 

causes a microrelief pattern on the surface of the 

ground, generally called polygonal ground or tundra 

polygons (fig. 27). Troughs that delineate polygons are 

generally underlain by ice wedges 1-2m wide at the top. 

These polygons are 2-30 m in diameter and should not 

be confused with small-scale polygons or patterned 

ground produced by frost sorting. 

Polygons may be low centered or high centered. Upturning of strata adjacent to the ice wedge may make a 

ridge of ground at the surface on each side of the wedge 

(Leffingwell, 1919, fig. 25 and pl. 29b), thus enclos-
50 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 26.-Foliated ground-ice mass (ice wedge) in silt exposed in placer gold mining operations on Wilber Creek near Livengood, 

Alaska. Photograph No. 474 by T. L. Pewe, September 19, 1949. 
PERMAFROST AND PERIGLACIAL DEPOSITS 51 

FIGURE 27.-0blique summer aerial view of raised-edge ice wedge polygons on the northern Alaskan sea coast near Barrow, Alaska. Diameters of polygons are 7-15 m. Photograph by R. I. Lewellen, August 11, 1966. 

ing the polygons. Such polygons are lower in the center 

and are called low-centered polygons or raised-edge 

polygons. They are erroneously termed by some ((depressed center" polygons. Low-center or raised-edge 

polygons indicate that ice wedges are actually growing 

and that sediments are being actively upturned (Brown, 

1969c, p. 124). If erosion, deppsition, or thawing is more 

prevalent than the up-pushing of the sediments along 

the sides of the wedge, or, if the material being pushed 

up cannot maintain itself above ground level, low ridges 

will be absent, and there may be either no polygons at 

the surface or the polygons may be higher in the center 

than troughs over the ice wedges that enclose them. 

Such high-center polygons are erroneously termed 

Hraised center" polygons by some. Both high-center and 

low-center tundra polygons are widespread in Alaska 

and are good indicators of the presence of foliated ice 

masses; but care must be taken to demonstrate that the 

pattern is not a relic and evidence of ice wedge casts. 

The origin of large ground-ice masses in perennially 

frozen ground of North America has been discussed in 

print since Kotzebue recorded ground ice at Elephant 

Point in Eschscholtz Bay (Kotzebue, 1821). The origin of 

ground ice was first discussed in Siberia (Bunge, 1884, 

1902). The general theory for the origin of ice wedges 

now accepted is the thermal contraction theory of 

Leffingwell (1915, 1919), which was succinctly summarized by Lachenbruch ( 1962): 

During the Arctic winter, vertical fractures on the order of onetenth of an inch wide and several feet deep are known to form in the 

frozen tundra-this process is generally accompanied by loud reports. 

They are assumed to be the result of tension caused by thermal 

contraction of the tundra. In early spring it is supposed that water 

from the melting snow freezes in these cracks and, with accumulating 

hoarfrost, produces a vertical vein of ice that penetrates permafrost. 

Horizontal compression caused by reexpansion of the permafrost during the following summer results in the upturning of permafrost by 

plastic deformation. In the winter that follows, renewed thermal 

tension supposedly reopens the vertical ice-cemented crack which is 

presumed to be a zone ofweakness. Another increment of ice is added 

when the spring meltwater enters the renewed crack and freezes. 

Such a cycle, it is argued, acting over centuries, would produce the 

vertical wedge-shaped mass of ice. The polygonal configuration is 

generally thought to be a natural consequence of contraction origin. 
52 QUATERNARY GEOLOGY OF ALASKA 

The thermal contraction hypothesis receives the most 

support (Bunge, 1884, 1902; Leffingwell, 1915, 1919; 

Black, 1952b, 1954, 1963;Popov, 1955, 1965; Hopkins 

and others, 1955; Shumskiy and others, 1955; Washburn, 1956; Britton, 1958b; Pewe, 1958a, 1959, 1962, 

1966a, b; Lachenbruch, 1961, 1962, 1966; Brown, 

1967a; Journaux, 1969). Taber (1943) and Schenk 

(1965), however, do not agree with this hypothesis. 

For the maximum annual thermal tension at the top 

of the permafrost to be of the same order of magnitude as 

the strength of foliated ground ice, the ground must cool 

at a certain rate for a certain period of time during a 

winter cold snap. A. H. Lachenbruch (oral commun., 

1962) stated that although the relations that determine 

whether an ice wedge cracks are extremely complex, a 

single simple criterion that takes account of many of the 

factors is the minimum winter temperature at the top of 

the permafrost. He suggested that when its value is 

below -15° to -20°C, the active cracking of ice wedges 

might be expected in many permafrost materials. 

Ice wedges may be classified as (1) active, (2) inactive, 

and (3) ice wedge casts. There is a complete gradation 

from one category to the next in areal distribution. 

Active ice wedges are defined as those which are actively growing. The wedge may not crack every year, 

but during many or most years cracking does occur, and 

an increment of ice is added. Under these conditions, 

low-center (raised-edge) polygons are well developed 

aruluhiquitons,Such microtopography is widespread in 

polar areas of actively growing ice wedges and sand 

wedges (Pewe, 1959; Pewe and Church, 1962). Highcenter polygons may also be present. 

The area of active ice wedges in Alaska appears to 

coincide roughly with the continuous permafrost zone 

(fig. 28) and is, in a general way, restricted to northern 

and northwestern Alaska. The meager thermal data 

available indicate that the winter temperature of the 

ground at the top of permafrost is about -15°C or colder. 

This area is limited almost entirely to tundra. Here 

active ice wedges occur in silt, sand, and gravel. From 

north to south across Alaska, a decreasing number of 

wedges crack frequently. The line dividing zones of active and inactive ice wedges is arbitrarily placed at the 

position where low-center or raised-edge polygons are 

uncommon and where it is thought most wedges do not 

frequently crack. When more data become available 

concerning the termperature at the top of the permafrost, this arbitrary line may be more accurately placed. 

The area of active wedges in Alaska outlined in figure 

28 has the most rigorous climate of the State. The mean 

annual air temperature ranges from about -6° to -soc 

on the south to -12°C at Barrow on the north (fig. 3). 

Minimum temperature of the ground in winter at the 

permafrost table (top of the ice wedge) ranges from 

172° 164° 156° 

70° 

66" 

580 

0 

0 

0 

148° 140° 

EXPLANATION 

--- Permafrost zone boundary 

Approximate position of 

0°C mean annual airtemperature isotherm 

Ice wedge zone boundary 

500 MILES 

500 KILOMETRES 

FIGURE 28.-Distribution of ice wedges and permafrost in Alaska. 

From Pewe (1966b). 

about -15°C on the south and -11° to -14°C nem 

Kotzebue (estimated from incomplete data from Cold 

Regions Research and Engineering Laboratory 

(CRREL), U.S. Army Corps of Engineers, Hanover, 

N.H., 1963) to about -30°C in the far north near Barrow 

(Lachenbruch, 1962). Temperature at the top of the 

permafrost table at Ogotoruk Creek near Point Hope is 

about -18° to - 20°C on the basis of a two-year record 

(A. H. Lachenbruch, oral commun., Nov. 20, 1962). 

Inactive ice wedges are defined as those that are no 

longer growing. The wedge does not crack in winter, and 

therefore no new ice is added. Of course, a gradation 

between active ice wedges and inactive ice wedges is 

represented by those wedges that crack rarely. Inactive 

ice wedges have no ice seam or crack extending from the 

wedge upward to the surface in the spring. The wedge 

top may be flat (fig. 26), especially if thawing has lowered the upper surface of the wedge at some time in the 

past. Low-center or raised-edge polygons are absent or 

rare, but high-center polygons are common. 

The area of inactive ice wedges in Alaska lies south of 

the Brooks Range and the south half of the Seward 

Peninsula (fig. 28); the northern boundary of the zone 
PERMAFROST AND PERIGLACIAL DEPOSITS 53 

roughly coincides with the discontinuous-continuous 

permafrost line (fig. 23). This region extends south to 

the Alaska Range and almost to the lower Kuskokwim 

drainage. Few data are available to permit the placing 

of even a broad line indicating the southern border of 

inactive ice wedges in the Yukon-Kuskowim Delta 

area. Inactive ice wedges in Alaska have been described 

only from frozen silt (Taber, 1943; Pewe, 1948, 1958b, 

1962, 1966b); none are known to exist entirely in sand 

or gravel. The inactive ice wedges are of Wisconsinan 

age. 

In the area of inactive ice wedges outlined in figure 

28, the mean annual air temperature ranges from about 

-2°C in the south to about -6° to -8°C in the north (fig 

3). Minimum winter temperatures at the top of permafrost are -3.3°C (temperature data for the cold winter of 

1961-62 from F. Kitze, oral commun., 1963) near Fairbanks, -4~C at Northway (temperature data from 

CRREL, U.S. Army Corps of Engineers, Hanover, N.H., 

1963), are estimated to be -3° to -6°C in the Copper 

River Basin on the basis of a 4-6-year record (A. H. 

Lachenbruch, oral commun., Nov. 20, 1962), and are 

suggested to be -10° to -15°C near the northern border 

of the zone. Such ground temperatures probably rarely 

permit thermal cracking of the ice wedges; therefore, no 

or rare ice increments are added to existing ice wedges, 

and they can be considered dormant, relict, or inactive. 

In this zone the permafrost in some areas of permeable sand and gravel has been thawed by heat supplied 

from moving ground water. Ice wedges that formerly 

existed in such sediments, therefore, are no longer present (Pewe and others, 1969). 

South of the zone of inactive ice wedges in Alaska, 

there lies a zone of discontinuous permafrost that contains practically no ice wedges. This area lies south of 

the Alaska Range and includes the Copper River Basin, 

the middle Susitna River valley, the Bristol Bay lowland (E. H. Muller, written commun., Mar. 8, 1963), and 

perhaps the southern part of the Yukon-Kuskokwim 

Delta (fig. 28). Ice wedges are not growing in this zone 

now. Perhaps they did not form in most of this zone 

during the Wisconsinan Glaciation because during all 

or part of Wisconsinan time most of the zone was under 

massive glaciers or proglaciallakes. After withdrawal 

of the ice or lakes, permafrost has formed locally, but 

the climate evidently has not been rigorous enough for 

many ice wedges to form except perhaps for a few small 

wedges that have grown in favorable places where the 

wind blows the snow cover away or where the vegetation cover is thin. Nichols reported (1966; written commun., 1968) that a few small ice wedges of Holocene age 

exist in the Copper River Basin. Areas outside glacial 

advances of late Wisconsinan age may have had ice 

wedges, but many or all of these wedges have now 

melted, as exemplified by the presence of ice wedge cast 

polygons in the Bristol Bay lowland. 

AGE OF ICE WEDGES 

The writer examined ice wedges in Alaska, Canada, 

Scandinavia, Siberia, and Antarctica and considers all 

wedges he has seen as Wisconsinan or Holocene in age. 

None to his knowledge have been proved to be preWisconsinan. Wedges in Alaska are of several ages, but 

none appear older than the last major cold period-the 

Wisconsinan. Those formed prior to that time have 

either melted or are so rare or deeply buried that they 

are no longer exposed or penetrated in drilling. 

Most wedges are dated by geologic association; however, attempts have recently been made to date wedges 

by radiocarbon analyses of the organic debris in the ice. 

This debris is primarily washed down the contraction 

crack throughout its history or is incorporated from the 

sides as the wedge grows. Radiocarbon dates should be 

younger or no older than the enclosing sediments, and 

this is borne out by samples collected by the writer (fig. 

29). A wedge at Barrow was dated at 14,000 years old 

(Brown, 1966b), wedges at Fairbanks near Fox at 

31,400 and 32,300 years old (Sellmann, 1967, 1972), and 

at Eva Creek (fig. 29) and Ready Bullion Creek near 

Fairbanks as older than 25,000 years. Problems of dating ice wedges using radiocarbon have not yet been 

solved. One of the first refinements probably should be 

to date samples collected systematically along vertical 

and horizontal lines from a Htypical" large wedge. Associated soil and wood should also be dated as illustrated in figure 29. Another method to study the age of 

ice wedges would involve the use of the 0 16-018 ratio in 

the ice. To the writer's knowledge, this technique has 

not yet been tried. 

ICE WEDGE CASTS 

In places in western, central, and south-central 

Alaska ice wedges have melted, and these voids have 

been filled with sediments collapsing from above and 

the sides. Although it is well known that ice wedges are 

common in Alaska, it is not generally realized that ice 

wedge casts exist. Actually, although most work on ice 

wedge casts has been done in Europe (see Pewe and 

others, 1969, for list of references; see Brown and Pewe, 

1973, and Pewe, 1973, for discussion of ice wedge casts 

and their paleoclimatic significance in North America), 

Alaska offers perhaps a great opportunity for the study 

and use of ice wedge casts as paleoclimatic indicators. 

This is because a good record of pre-Illinoian, Illinoian, 

and Wisconsinan permafrost exists in Alaska as well as 

sediment replacements of ice wedges of those ages. Such 

is not recorded elsewhere. Also, in Alaska, ice wedges 

and permafrost of Wisconsinan age still exist and aid 
CONDUCTIVITY, ,umhoa 

~ ~ § § i ~ - - - ~ c 

SAMPLE 

LOCATION 

• :WDEPTH IN 

METRES 

STRATIGRAPHIC 

SECTION 

25,000 yHrs (3) 

24,000 yeers (4) 

I 

(8) 

>28,000 yean (9) 

I 

I 

I 

I 

AGE AND 

UNIT 

HOLOCENE; 

bedded loen, ice 

content 1111 then 

Wiaconainen 

WISCONSINAN; 

retr81'1aported 

loeu; brown 

SANG AMON 

foreat bed 

ILLINOIAN 

loen;grHn 

YARMOUTH(?); 

for"t bed, 

or11nic ailt 

PREYARMOUTH(7); 

coer• creek 

grevel 

I 

I 

I 

FIGURE 29 .-Stratigraphic section oflate Quaternary perennially frozen sediments with radiocarbon dates, vertebrate occurrences, and geochemical analyses of sediment. Eva 

Creek, 16 km west of Fairbanks, Alaska. Photograph No. 2540, by T. L. Pewe, July 2, 1967. See table 5. 

01 

*"" 

.0 

c:::: 

t;rj 

~ 

::0 

z 

?d 

-<: 

0 

t;rj 

0 

t"'4 

0 

0 

-<: 

0 

"%j 

~ > r:n 

~ 

> 
Notes for figure 29: 

(1) The permafrost table was lowered throughout central Alaska 1-5m about 

10,000 years ago and has subsequently risen to its present position. All 

sediments in the deep thaw layer were unfrozen for hundreds if not 

thousands of years. Flat-top ice wedges and collapse of sediments over 

ice wedges remain as evidence of this thawing episode. 

(2) The age of this formation in the Fairbanks area is well documented (Pewe, 

1952a, 1958b, 1965a, 1975). More than a dozen samples have been dated 

from the Holocene loess and retransported loess in many different mining exposures; the dates range from about 3,000 to 10,000 years, with 

most of them in the neighborhood of 5,000--7,000 years. A date of 

3,750±200years (L-117H) was obtained on a sample of wood collected by 

the writer in 1951 from the Holocene loess and retransported loess in 

Eva Creek 2m below the surface. A date of 10,000±500 years (L-1378) 

was obtained on a sample of wood collected by the writer in 1951 from the 

base of the Holocene loess on Eva Bench mining exposure 3 m below the 

surface. 

(3) In 1967 the writer collected for dating samples of ice, wood, and organic-rich 

silt that were adjacent. All were dated by the radiocarbon laboratory at 

the University of Arizona as more than 25,000 years old. More detailed 

dating probably would have indicated an age between 25,000 and 30,000 

years. A wood sample collected in 1951 by the writer 2.5 m below the top 

of the Wisconsinan sediments on Eva Creek was dated at 23,300± 1,000 

years (W-435). Wood samples collected by the writer in 1952 at the base 

of the Wisconsinan formation and near the middle were dated as greater 

than 23,000 years old (L-157 A) and greater than 30,000 years (L-163J), 

respecti velJl. 

(4) A radiocarbon date of 24,400±650 years (1-2116) was obtained on wood 

collected at the base of the ice wedges (Matthews, 1968a, p. 207). 

(5) Matthews (1968a, b) examined fossil beetles from Wisconsinan and Sangamon deposits. Beetles, plus a pollen study by Matthews and of samples 

collected by the writer, indicate a treeless tundra environment during 

Wisconsinan time. In 1949 Pewe also collected bones of mammoth and 

Citellus undulatus from Wisconsinan sediments here. Guthrie (1968b) 

recovered Microtus gregalis, Lemmus sibericus, Dicrostonyx torquatus, 

and Citellus undulatus from both Wisconsinan and Illinoian deposits in 

this section. 

(6) Pewe (1952a) reported a forest bed at this stratigraphic horizon from many 

exposures in the Fairbanks area. The oldest date obtained on this bed 

was reported by Matthews (1968b) as more than 56,900 years (Hv-1328). 

This organic-rich silt layer with tree stumps and logs unconformably 

overlies the deformed loess. (See fig. 20). 

(7) In innumerable exposures ofthe contact between Wisconsinan and Illinoian 

silt in the Fairbanks area a 1-cm-thick, white, vitric, volcanic ash bed 

occurs at the top of the Illinoian loess and is truncated by an unconformity. This bed is deformed by faulting and solifluction (Pewe, 1975). 

(8) The writer collected (194~67) mammoth tusks and various bones of bison 

from loess of Illinoian age of Eva Creek. 

(9) At Dawson mining cut and others a well-developed organic silt crops out 

(Pewe, 1952a, 1975). This unit contains large stumps and logs that are 

partly flattened and deformed; it is thought to represent an interstadial 

or interglacial forest bed. One particularly fine white spruce stump (fig. 

39) from the organic silt of the Eva Creek section and with roots in the 

underlying gravel is more than 28,000 years old (L-137X). 

;g 

~ 

~ ~ 

> 

~ >-tl 

trj 

~ 

~ 

~ 

~ t:=' 

trj 

~ rn 

::3 

rn 

01 

01 
56 QUATERNARY GEOLOGY OF ALASKA 

tremendously in the interpretation of description, 

origin, and paleoclimatic importance of ice wedge 

pseudomorphs. The presence of ice wedges in permafrost offers a refinement in paleoclimatic interpretation 

not possible in permafrost without ice wedges. 

Although ice wedge casts have been reported from 

southern Canada and the northern part of the United 

States, they have been most thoroughly studied in 

North America in Alaska, particularly in glacial outwash of Wisconsinan age near Big Delta (pl. 1) (Pewe 

and others, 1969). To date, of the 21localities where ice 

wedge casts have been mentioned in North America 

outside Alaska, none have been demonstrated to be 

pre-Wisconsinan in age. In Alaska both pre-Wisconsinan (Illinoian(?)) and pre-Illinoian ice wedge casts 

are present (table 5; fig. 30). 

In Alaska ice wedge casts in sediments of Wisconsinan age occur south of the glacial border in Bristol Bay 

(Hopkins and others, 1955, p. 139), on the Pribilof Islands (D. M. Hopkins, oral commun., Dec. 4, 1972), and 

near Nome (Hopkins and others, 1960). Ice wedge casts 

indicative of Wisconsinan permafrost have been reported in gravel along the Tanana valley outside the 

Wisconsinan ice limits (Pewe and others, 1969; Blackwell, 1965; Ager, 1972). Ice wedge casts in the south 

probably indicate a northward retreat of the southern 

boundary of permafrost. Those in the Tanana valley 

indicate a thawing of permafrost in well-drained gravel 

areas with a minimum of vegetation and winter snow 

cover. 

In addition to aiding in the reconstruction of the distribution of permafrost in Alaska during Wisconsinan 

time, ice wedge casts indicate the earlier existence of 

permafrost, for example in Illinoian(?) time on the 

Pribiloflslands (Hopkins and Einarsson, 1966) and varTABLE 5-lce wedge cast localities in Alaska 

Location Time of No. ice wedge 

(fig. 30) Author Date Locality formation 

Hopkins, MacNeil, 1960 Nome---------------- Wisconsin 'in. 

and Leopold. 2 Pewe ________ __ (unpub. Fairbanks ______ ______ Wisconsinan. data) 3 Blackwell ___ ___ 1965 Tanana River ________ Wisconsinan. 4 Pewe, Church, and Andreson. 1969 Big Delta ------------ Wisconsinan. 

5 Ager __________ 1972 Healy Lake ___ _______ Wisconsinan. 6 Hopkins 1972 (oral Pribilof Island ______ __ Wisconsinan. commun.) 

Hopkins ------ 1972 (oral Kvichak Peninsula __ __ Wisconsinan{?). commun.) 8 Hopkins 1955, Bristol Bay ---------- Wisconsinan. and others. p. 139 9 H]Fi~~:S:onn~ 1966 Pribilof Island _______ _ lllinoian(?). 

10 McCulloch 1966 Northwestern Alaska Illinoian(?). 

11 and Ho~kins . McCulloc , 1965, Baldwin Peninsula, Illinoian(?). Taylor, and Rubin. p. 449 northwestern Alaska. 

12 Pewe __ ________ 1966b Fairbanks ____ ______ __ Illinoian(?). 13 Guthrie and 1971 Northern Pre-Illinoian. Matthews. Seward Peninsula. 14 Pewe __________ 1965a, Fairbanks ____________ Pre-Illinoian. 

15 Pewe __________ p. 17 1965b, Shaw Creek ---------- Pre-Illinoian. fig. 4-22 

ious places in northwestern Alaska (McCulloch and 

others, 1965; McCulloch and Hopkins, 1966). Ice wedge 

casts in two areas in Alaska permitted the writer to 

delineate permafrost of an extremely ancient age, 

perhaps a million years or more. In central Alaska Pewe 

(1965b, fig. 5--22) described well-developed ice wedge 

casts of pre-Illinoian age in solifluction deposits at Shaw 

Creek. Also, an ice wedge casts of sand underlying two 

different ages ofloess are exposed in excavations on the 

University of Alaska campus and are thought to be 

pre-Illinoian in age (Pewe, 1965a, p. 17). 

In the far western part of Alaska, Guthrie and Matthews (1971) indicated the presence of ice wedge casts 

near Cape Deceit which were thought by Hopkins 

(1972) to be at least a million years old. 

PINGOS 

Another type of massive ground ice in permafrost is 

that found in pingos. Pingos are conical ice-cored hills or 

mounds, round to oval in plan, 2~400 min diameter, 

and 1~ 70 m high that form when large, massive layers 

of ice grow near the surface in permafrost (Porsild, 

1938; Muller, 1963; MacKay, 1966; Holmes and others, 

1968). Pingos are of two distinct genetic types: the 

closed system and the open system. The closed-system 

type forms in nearly level areas when unfrozen ground 

water migrates under pressure to a site where then 

permafrost is domed up to form a mound. These are the 

larger of the two types of pingos and occur in areas of 

continuous permafrost, the tundra areas. The opensystem type is generally smaller and forms on sloping 

ground where water beneath, or within, the permafrost 

penetrates the permafrost under high hydraulic pressure, which along with crystallization pressure heaves 

the overlying material to form a mound. 

The distribution of pingos in Alaska has become 

much better known in the last decade. The presence of 

pingos are not only of value in indicating the presence of 

permafrost, but in indicating continuous or discontinuous permafrost. With one or two exceptions, the first 

local maps ofpingo distribution in Alaska and adjacent 

Canada have appeared in the last 10 years (MacKay, 

1963, 1973; H.olmes and others, 1968; Hughes, 1969); 

the first map of pingo distribution in north-northwest 

North America is shown in figure 31. 

Considerable progress has been made in the discovery 

and mapping of many open-system pingos in unglaciated central Alaska and adjacent Yukon Territory 

(fig. 31), as well as in the discovery ofpingolike mounds 

in the shallow waters of the Beaufort Sea north of the 

mouth of the Mackenzie River (Shearer and others, 

1971). The greatest advance in pingo research in the 

last decade has been a consideration and understanding 

of theory and rate of pingo growth by MacKay (1968, 
PERMAFROST AND PERIGLACIAL DEPOSITS 57 

Limit of Wisconsinan 

~ glacial ice 

ICE WEDGE CASTS 

,A5 

Wisconsinan 

.,0 .,5 

Illinoian(?) Pre-Illinoian 

Permafrost zone boundaries 

0 0 0 

7°C air isotherm 

0 100 200MILES 

I' I I 11\ 1 

0 100 200 Kl LOM ETRES 

FIGURE 30-Distribution and age of ice wedge casts in Alaska. 

1971, 1972a, b, 1973; MacKay and Stager, 1966; MacKay and Black, 1973). 

After restudy of the photographs of the mounds in the 

Yukon-Kuskokwim Delta in Alaska and an examination ofpalsas elsewhere in the world, Pewe believes that 

the 200 so-called closed-system pingos mentioned by 

Burns (1964) occurring on the Yukon-Kuskokwim 

Delta are probably not pingos, but palsas. 

Pingos are abundant in the forested, subarctic, discontinuous permafrost zone of Alaska. Although Harrington photographed pingos in central Alaska 60 years 

ago (Leffingwell, 1919, pl. 17 A; Mertie and Harrington, 
58 QUATERNARY GEOLOGY OF ALASKA 

• 

• • 

• 

EXPLANATION 

NO PERMAFROST Limit of Wisconsinan • glacial ice 

• 0 t:. 

Area of closed- Area of open- Area of subsystem pingos system pingos marine pingos 

Permafrost zone boundaries 

200 MILES 

II II 1111 I 

0 100 200 KILOMETRES 

FIGURE 31.-Distribution of open- and closed-system pingos in relation to permafrost zones and areas covered by Wisconsinan glacial ice 

in North America. Compiled from all published and unpublished sources, including written comments from D. M. Hopkins, J. R. 

MacKay, I. Tailleur, 0. J. Ferrians, Warren Yeend, Helen Foster, and 0. L. Hughes in 1972. 

1924, p. 8), and although the writer and his colleagues 

noticed mounds and circular lakes in permafrost of the 

valleys in central Alaska for many years, the overriding 

idea that pingos were arctic features probably prevented acceptance or recognition of pingos in forested 

areas until the late fifties. 

It then became obvious that open-system pingos are 

widespre~d in central Alaska and are even adjacent to 
PERMAFROST AND PERIGLACIAL DEPOSITS 59 

the University of Alaska and the populated environs of 

Fairbanks (Pewe, 1965a). At least one was even chosen 

for a house site (Pewe, 1965a, p. 31). Holmes, Hopkins, 

and Foster were the first to point out the existence, type, 

distributuion, and abundance of pingos in central 

Alaska (Holmes and others, 1966, 1968). Subsequently 

more than 700 open-system pingos have been recognized in central Alaska (Pewe, 1965a; Krinsley, 1965; 

Foster, 1967) and adjacent Yukon Territory (Vernon 

and Hughes, 1966; Hughes, 1969; Fyles and others, 

1972; Hughes and others, 1972). 

From figure 31 it is easily seen that open-system 

pingos are essentially restricted to discontinuous permafrost zones. Open-system pingos lie near the base of 

slopes. Evidently water enters the subsurface system 

from the surface in the nonpermafrost areas upslope. 

Studies in the last decade indicate overwhelmingly that 

almost all open-system pingos in northwest Alaska and 

Yukon lie on the south or southeast-facing slopes of 

alluvium-filled valleys (Holmes and others, 1968; 

Hughes, 1969). The reason for this is still unknown, 

although perhaps there are more opportunities for surface water to enter the ground in the nonpermafrost 

areas on south-facing slopes. 

One of the most interesting features of the distribution of pingos in northwestern North America is the 

relation of pingos to the glacial border (fig. 31). Almost 

all open-system pingos lie in the unglaciated part of the 

country, but a few pingos are known in areas that have 

been glaciated more than 25,000 years ago. Pingos are 

extremely rare in areas glaciated within the last 25,000 

years; none are known in Alaska and only two are 

known in Yukon Territory (Hughes, 1969), but perhaps 

about halfofthe 1,500 in the Mackenzie delta (MacKay, 

1973) are in areas glaciated during the late Wisconsinan. Hughes (1969) speculated that the absence of opensystem pingos in the glaciated areas may be attributed 

to glacial modification of the topography and surficial 

materials necessary for their origin or to differences in 

the extent and thickness of permafrost resulting from 

glacial and postglacial history of the area. The reason 

for such a distribution of open-system pingos in relation 

to the glacial border constitutes one of the problems that 

should be investigated in the near future. 

Radiometric dating indicates that most pingos in 

Alaska are less than 4,000--7,000 years old (Krinsley, 

1965). MacKay (1973) showed by careful field Ineasurement over several years that many are probably less 

than 1,000 years old and some less than 100 years. 

One of the remaining problems in need of more research is a study of the water associated with opensystem pingos as well as the roll of artesian pressure. In 

1968, Lissey began a study of hydrology of open-system 

pingos near Dawson, Yukon Territory, but no detailed 

results are yet available (Lissey, 1970). Williams and 

vanEverdingen (1973) mentioned that one of the problems to be solved is a better understanding of the 

pressure developed to lift the static load of a pingo, 

inasmuch as a total force of 6--22 atmospheres is 

thought to be required. The only work known on the 

chemical and biological properties of water in a pingo 

lake is the preliminary study by Lotspeich, M iieller, 

and Frey (1969) on a lake in east-central Alaska. 

GEOCHEMISTRY OF PERMAFROST 

A relatively new approach to the study of perennially 

frozen ground is the chemical investigation of ice and 

sediments associated with permafrost; this approach 

appears to hold great potential. The work is being 

pioneered in Alaska by Jerry Brown and his associates 

of the U.S. Army Cold Regions Research and Engineering Laboratory (Brown, 1965b, 1966a, b, 1967a, 1969a, 

b, d; Brown and Johnson, 1965; Brown and others, 1967, 

1969; Sellmann, 1967, 1968; Allan, 1969), although the 

first worker in the field in Alaska was perhaps 

O'Sullivan (1961, 1966). Brown stated (1969a, p. 1) 

The spatial distribution of cations and anions in near-surface, 

earthy materials, such as soils and frozen ground, provides a means of 

interpreting and assessing present and past chemical regimes and 

geomorphological activities of a given landscape. This technique is 

particularly applicable to cold, perennially frozen ground in which 

movement of soluble ions is small and perhaps even insignificant. 

Therefore, the existing ionic concentration gradients and their lateral 

dimensions can be indicative of cold regions environments and provide a measure of conditions prior to the formation of the perennially 

frozen ground. ·• 

The distribution of soluble and exchangeable ions in soils, perennially frozen ground, and sediments underlying water bodies is 

influenced by both the materials and the present and past depositional 

and leaching environments. For the same material and environment, 

low concentrations indicate considerable leaching or freshening and 

high concentrations indicate lack of these active processes or enrichment by ground or surface waters. Silts and clays retain more soluble 

and exchangeable ions than do sand and gravels. Ionic concentration 

generally increases with depth, particularly in uplifted marine sediments. 

Most of the work in this field has revolved around the 

distribution of soluble salts of sodium, magnesium, calcium, and potassium in perennially frozen sediments as 

a reflection of past thermal and leaching regimes. It has 

been shown that a relatively low concentration of soluble salts in permafrost indicates leaching during an 

unfrozen state and then refreezing. At Barrow (Brown, 

1969a), this low concentration in Holocene marine sediments has been interpreted as freshening due to past 

lake migration or to local or regional thawing, leaching, 

and refreezing. 

For the Fairbanks area, Sellmann (1967, 1968) indicated an abrupt change in chemical concentrations of 

extractable cations in permafrost at a stratigraphic unconformity in retransported sediments of Wisconsinan 
60 QUATERNARYGEOLOGYOFALASKA 

age (fig. 20). Preliminary interpretations suggest thawing and refreezing above the unconformity. Four cores, 

the longest 25m deep, of perennially frozen ground from 

near Fairbanks were examined by Brown (Brown and 

others, 1967, 1969) and also indicate an increase of 

soluble salts beneath an unconformity. The soluble salt 

content is low in the active layer and increases in steplike fashion at depth in the perennially frozen ground. 

The writer applied techniques developed by Jerry 

Brown and P. V. Sellmann to the excellent exposures of 

frozen ground in the mining cuts near Fairbanks that 

have long been studied by other means. Perennially 

frozen samples collected by the writer from critical 

points in a 40-m vertical exposure on Eva Creek, 16 

km west of Fairbanks, were analyzed for soluble salts by 

Brown and Sellmann at the U.S. Army Cold Regions 

Research and Engineering Laboratory (written commun., Dec. 28, 1967 and May 19, 1971) by a method 

described earlier (Brown and others, 1967) and reported 

in terms of conductivity (JLmho). The work is continuing, but preliminary results are presented here, in table 

6 and figure 29, to illustrate possible value of such 

studies and their application elsewhere. 

As table 6 shows, the present active layer is characterized by the low conductivity figure of 65-85. It has 

long been known that the upper 1 or 2m of permafrost in 

interior Alaska thawed during early to middle Holocene 

time and then refroze (Pewe, 1952a, 1968b, 1975). This 

cycle is supported by the relatively low conductivity 

TABLE G.-Conductivity and stratigraphy of sediments exposed at Eva Creek gold placer mining cut 

[Conductivity examination made at U.S. Army Cold Regions Research and Engineering 

Laboratory, Hanover, N.H., by Jerry Brown and P. V. Sellmann] · 

Thickness (m) Unit 

Surface 

Conductivity ~J.mhos) of samples 

1-------------1 Age 1967 1970 

2 Loess 65 Holocene 

r!r~r ~~afro~t-r- ------ 156--- --- --- -- i~~----

(dashed line = ------------------------------------- past permafrost 314 235 

table) ~~~ 

285 13 Retransported 304 Wisconsinan 

1 

19 

1 

loess 317 

Silt-forest bed 

Sangamon soil? 

Loess 

Silt-forest bed 

Gravel 

234 

250 

410 

143 

100 

1,125 

1,100 

883 

1,285 

Sang am on 

355 

965 

300 

450 

300 Illinoian 480 200 

Y arniouth(?) 

Pre-Yarmouth(?) 

figure in the perennially frozen Holocene silt, a figure 

lower than frozen Wisconsinan sediments but higher 

than current active layer sediments. Leaching was active during the thaw period. Conductivity jumps to 300 

just below the Wisconsinan-Holocene unconformity, 

and all values in Wisconsinan sediments are about that 

magnitude, supporting the suggestion of an accumulation and freezing period. Thermal ~~unconformities" 

within the Wisconsinan sediments could be present but 

missed in the sampling. 

The drop in conductivity from 410 at the base of the 

Wisconsinan sediments to 143 in the forest layer (Sangamon) is quite striking and supports the suggestion of 

an interglacial period of no permafrost and perhaps 

little accumulation. A period when the ground was unfrozen or when little or no loess accumulated would be 

favorable for leaching (Pewe and Sellmann, 1971). 

A sample at the very top of the loess section of Illinoian age yields a conductivity of 100. It is thought 

that this low figure represents the Sangamon soil and 

indicates thawing and leaching of Illinoian loess. 

The pronounced drop in values in the forest soil layer 

at the base of the section relative to bounding deposits is 

similar to the forest layers higher in this section and 

strongly supports the suggestion of an interglacial or 

interstadial period with thawing and little deposition. 

The figures for conductivity of the sediments near the 

base of the section are much different from the upper 

part (table 6). The base of the permafrost in many exposures in central Alaska today, and perhaps in the 

past, was at the base of the silt deposits, that is at the 

contact between the overlying loess or retransported 

loess and the underlying creek gravel. Ground water 

may have circulated freely in the gravel just under the 

silt and may have been high in soluble salts. This would 

account for the high conductivity figures at the base of 

the silt section, including the forest bed, and the top of 

the creek gravel. In nearby exposures many ironston6 

and calcium carbonate concretions occur at the contact 

between the silt and the gravel. Also, contemporary 

ground water analyzed from near Fairbanks has a conductivity figure of about 1,000 JLmhos. Therefore, 

perhaps the high conductivity figures at the base of the 

section at Eva Creek are the result of ground-water 

modification. 

It is perhaps logical to assume, as Brown, Gray, and 

Webster (1967) mentioned, that the low soluble salt 

content of fine-grained soil is probably due to removal 

by ground-water movement (leaching) during a time 

when the sediments are unfrozen, especially near the 

surface. Specifically, they found that unfrozen sediments of the present active layer at Fairbanks, which 

has been leached for many years, have a conductivity 

value of 25. Also, in periods of rapid, thick accumula-
PERMAFROST AND PERIGLACIAL DEPOSITS 61 

tion, sediments have less opportunity to be leached than 

in periods of little or no accumulation. This has been 

clearly demonstrated in loess in Iowa (Davidson and 

Handy, 1952, table 5) and Mississippi (Krinitzsky and 

Turnbull, 1967, p. 9). In areas there where loess accumulates slowly, the carbonate is almost entirely 

leached out, in contrast to high carbonate content in 

areas where loess accumulates rapidly. 

Preliminary geochemical investigations dealing with 

ice wedges indicate that the ionic content of the ice is not 

all from surface meltwater moving down the contraction crack as was earlier assumed but in part is the 

result of addition of debris from the sides by wedge 

growth. The percentage of soluble salts increases with 

depth in the wedges at Barrow. It would be well to 

continue this work on wedges of different ages, sizes, 

shapes, and geologic locations elsewhere in Alaska. 

Preliminary geochemical analyses of frozen sediments and ice in northern and central Alaska suggest 

that the chemical investigation of frozen ground in 

permafrost regions holds a great potential for gross 

correlations, and perhaps for interpretat_ion and 

geomorphological and thermal changes in Quaternary 

time. 

PERIGLACIAL PROCESSES AND DEPOSITS 

In parts of central, northwestern, and northern 

Alaska, some of the modification of the landscape is by 

geologic processes active in a periglacial region. These 

processes include nivation, frost riving, frost stirring 

and sorting, solifluction, and choking of small streams 

with detrital material moved downslope in part by frost 

action. Both Troll (1948, fig. 1) and Peltier (1950) proposed a specific geomorphic cycle of denudation and 

wearing down of the landscape by the processes which 

might be described by Bryan's (1946) term ucryoplanation," although terms such as ((altiplanation" (Eakin, 

1916, p. 78) and ((equiplanation" (Cairnes, 1912a, p. 

338-348) suggested by earlier workers in Alaska and 

the Yukon perhaps are equally appropriate. 

Periglacial processes can be grouped into two types: 

processes such as nivation and frost action that produce 

erosional landforms and erosional debris, and processes 

such as solifluction, rubble sheet and block stream, and 

rock glacier movement that transport this debris down 

slopes to form depositional landforms. The erosional 

landforms produced are altiplanation terraces, scarps, 

cliffs, and tors. The deposits include slope and valley 

bottom accumulations owing to mass wasting and are 

termed solifluction deposits, rubble sheets, block fields, 

and rock glaciers. The term ucolluvial" deposits or colluvium of some authors has been used, at least in part, 

synonymously in Alaska for periglacial deposits (Fernald, 1960, p. 214-219; Hopkins and others, 1960, p. 54; 

Holmes, 1959b, p. 54; Pewe and Holmes, 1964). 

Inherent in the term uperiglacial" is that the process-

.es and the deposits under consideration generally occur 

below snowline. Inasmuch as the position of snowline 

varies from one part of the State to another, the altitude 

at which the processes are active also varies. In addition, the position of snowline changed several times 

during the Quaternary Period. Both present and past 

variations in snowline are shown along a line extending 

from Seward Peninsula east to the Canadian border and 

another line extending from the Gulf of Alaska north to 

the Arctic Ocean (figs. 8, 9). 

In Alaska it may be possible to study the gap that 

exists between actively forming periglacial deposits 

and the ufossil" deposits. Therefore, periglacial deposits 

may occur at various altitudes in Alaska and be of 

various ages. Variations in location of deposits and activity of the processes occur with changes in latitude 

and altitude. The writer and his colleagues are analyzing the past and present distribution of periglacial processes and deposits in Alaska. 

Altiplanation terraces are the most widespread periglacial erosional form in Alaska (fig. 32); fresh and 

relict forms occur throughout the central, western, 

northwestern, and southwestern part of the State. Altiplanation terraces are large bedrock steps or terraces on · 

ridgecrests and hilltops (Eakin, 1916, p. 78); the terraces possess at least one scarp (ascending and (or) 

descending) and a tread surface. The tread or ((flat" area 

is 10 to several hundred metres wide and long, and 

slopes from 1 o to 15°, parallel to the ridgecrest. Terrace 

scarps are from 1 to 30m high. Treads and scarps are cut 

into all bedrock types, but altiplanation terraces are 

best developed on closely jointed resistant rocks such as 

basalt and andesite. They are more poorly developed on 

granite and tilted sedimentary or low-grade metamorphic rocks. Residual bedrock knobs (tors) project above 

some terrace treads. 

Altiplanation terraces form perhaps a little below the 

general altitude of snowline. The scarp retreats by nivation, forming a tread, and surficial debris is removed 

across and over the treads by mass movement. Above -

snowline, glaciers, cirques, horns, and aretes form. On 

isolated ridges and peaks not large enough to support 

large glaciers, however, altiplanation terraces form 

above snowline. As terraces form, frost-rived debris is 

shed as a blanket of mass-wasting material from the 

terraces down the slopes to creek valley bottoms. 

Whether this abundant bedrock rubble is transported 

as solifluction material, rubble sheets, or rubble steps 

depends largely on the amount of fine material and 

water. 

The widespread altiplanation terraces in Alaska 

occur at different altitudes and vary in sharpness of 

form; some are well developed with sharp edges to the 
62 QUATERNARYGEOLOGYOFALASKA 

FIGURE 32.-Altiplanation terraces cut into a greenstone ridge of Indian Mountain, Hughes A-2 quadrangle, Alaska. View toward 

south of transverse snowbanks against north-facing terrace scarps. Photograph No. 2498 by T. L. Pewe, June 25, 1967. 

scarps, and some are less ((fresh." In all areas the 

fresher, sharper ones are at higher altitudes, and in 

some places they can be traced continuously to lower 

altitudes on the same ridge, where they are older and 

more rounded. 

Well-formed altiplanation terraces occur at 

1,100-1,400 min the Yukon-Tanana Upland. Farther 

west in the Indian Mountain area near Hughes, they 

occur at 900-1,000 m above sea level (Eakin, 1916, pl. 

7). They are well formed at lower altitudes farther west, 

for example, at 400 m above sea level near Marshall 

(Harrington, 1918, pl. V). A plot of the elevations of 

well-formed altiplanation terraces from east to west in 

Alaska falls on a line below, but parallel to, past and 

present snowlines (fig. 8). 

It is not known if altiplanation terraces are actively 

forming in Alaska today. It is known that terraces were 

formed in Wisconsinan time (Pewe, 1965c, p. 90; Reger 

and Pewe, unpub. data, 1974), and some may still be 

slightly active. 

One of the problems remaining is the determination 

of the climatic conditions necessary to produce the terraces. The exact knowledge of such conditions would aid ' 

in determining the paleoclimatic conditions under 

which ancient altiplanation terraces formed. Relict altiplanation terraces have elevations of about 1,600 min 

the Yukon-Tanana Upland; at Fairbanks, however, altiplanation terraces of pre-Illinoian age occur at an 

elevation of 260-900 m (Pewe, 1969b, 1970b). 

Most periglacial deposits in Alaska can probably be 

attributed to the mass-wasting processes described by 

solifluction. The meaning of the term as introduced by 

Andersson (1906) is now slightly modified, and Smith's 

(1949, p. 1499) definition, uprogressive downslope 

movements of presumably saturated detrital material 

under action of gravity, probably working in conjunction with frost-heave in most instances," is used here. 

The fact that this material moves in a semifluid condition is suggested by the lobelike or sheetlike flows commonly exhibited on slopes. One of the outstanding features of solifluction is the mass transportation of material over low-angle slopes (Capps, 1919, p. 69; Wahrhaftig, 1951, p. 180; Sigafoos and Hopkins, 1952, p. 183). 

Solifluction deposits are widespread in Alaska and 

consist of a blanket, approximately 0.3--6 m thick, of 

unstratified or poorly stratified, unsorted, heterogeneous, till-like detrital material of rather local provenance. The debris is either angular or rounded, depending upon the parent material. In actively forming deposits, turf and peat may be incorporated. 

In some areas of active solifluction in Alaska, the 

terrain is characterized by relatively smooth, rounded 

hills and slopes bearing well to poorly developed 

solifluction lobes or terraces. If the debris is blocky and 
PERMAFROST AND PERIGLACIAL DEPOSITS 63 

angular and fine material is absent, the lobes are poorly 

developed or absent entirely. Areas in which 

solifluction lobes are well formed lie almost entirely 

above or beyond the forest limit (fig. 8). The lobes are at 

an elevation of 1,200 min central Alaska on the Canadian border and at progressively lower altitudes to the 

west, until on the Seward Peninsula they are only a few 

hundred metres above sea level (fig. 9). Table 7 gives 

elevations of some active solifluction lobes in Alaska. 

In northern Alaska, solifluction deposits are actively 

forming over a wide area from elevations near sea level 

to near 1,500 m. Solifluction lobes have been detected on 

aerial photographs of central, western, and northern 

Alaska. It should be noted that whereas well-formed 

lobes are an easily recognizable indication of the process 

of solifluction, the process may be active and important 

at altitudes several hundreds of metres lower than 

where such lobes occur. 

Quantitative studies of active mass wasting in 

Alaska are only beginning (Everett, 1962, 1966). Most 

studies of solifluction deposits have been made in temperate latitudes where solifluction is no longer active. 

These studies have proved valuable in the interpretation of past geologic events and paleoclimatic environments. Examination of the widespread stabilized 

solifluction deposits in Alaska has only just begun, but 

they hold great promise for a more detailed interpretation of Quaternary events in nonglaciated regions. 

At Cape Denbigh (Hopkins and Giddings, 1953, p. 

18), along the Firth River in northwest Yukon Territory, in Canada near the Alaska-Canada boundary 

(Mackay and others, 1961, p. 46), and at the Onion 

Portage site on the Kobuk River (Giddings, 1967), evidence of solifluction within the past few thousands of 

years has been helpful in interpreting the geologic history of archaeological sites. 

Stabilized solifluction sheets of pre-Illinoian age are 

widespread in the Yukon-Tanana Upland and are best 

known in the Fairbanks area. Underlying the extensive 

TABLE 7 -Elevation above sea level of active solifluction lobes in Alaska 

Elevation (m) Location 

Central and Western Alaska 

1,100-1,200 ______ Yukon-Tanana Upland ___________ _ 

1,400 ____________ Central Alaska Range ___________ _ 

600-900 ________ Kokrine Hills ___________________ _ 

750______________ Near Hughes, north side 

of Ray Mountains. 200______________ Nome and vicinity _______________ _ 100-150 ________ Cape Denbigh ___________________ _ 

150_ __ __ ___ _ __ ___ Pribilof Islands ___________________ _ 

Northern Alaska 

Source 

Taber (1943, p. 14), Pewe (1952a, fig. 7). Pewe (1952a, fig. 8), 

Wahrhaftig (1958, p. 59). Eakin (1916, pl. 7 A). T.L. Pewe (unpub. date, 1970); Eakin (1916, pl. 7 A). 

Sigafoos and Hopkins (1952). 

Hopkins and Giddings 

(1953, pl. 1). D.M. Hopkins (written commun., 1969). 

Near sea level __ Alaska-Canadian border __________ MacKay, Matthews, and MacNeish (1961, p. 44-46). 

500______________ Alaska-Canadian border __________ Drew and Shanks (1965). 600-900 ________ North flank of Brooks Range ______ Holmes (1959b, p. 55). 

600______________ Anaktuvuk Pass ----··------------- Porter (1966, pl. 18). 

loess deposits of central Alaska are one or more sheets of 

stable solifluction material 0.3-3 m thick blanketing 

the hillsides (fig. 20) (Pewe, 1965a, fig. 1-2; 1965b, figs. 

4-21, 4-22; Blackwell, 1965; Pewe, 1969b). The poorly 

developed stratification is ~~dragged out downslope." 

One of the most thoroughly studied areas of ancient 

solifluction deposits is on the campus of the University 

of Alaska. Here a complex series of events is recorded by 

solifluction layers and ice wedge casts Cfossil" ice 

wedges) beneath Wisconsinan and Illinoian loess (fig. 

33). The two mass-wasting deposits are thought to be 

early to middle Pleistocene in age, and the ice wedge 

casts probably are evidence for the oldest permafrost 

known in Alaska. D. M. Hopkins (oral commun., 1965) 

observed a similar stratigraphic record in the Tofty 

mining district 130 km west of Fairbanks. It should be 

noted that the stabilized solifluction deposits in the 

Yukon-Tanana area occur at an elevation of 150 m 

above sea level or even lower, a lowering of at least 900 

m from the position of the well-formed lobes present 

today (table 7). In the absence of tectonic movement, we 

must assume a dramatic lowering of rigorous 

Surface of ground 

0 5 10 15 FEET 

0 3 METRES 

FIGURE 33.-Early Quaternary solifluction deposits and ice wedge casts of sand exposed in excavation for Duckering Building, University 

of Alaska campus. Drawn by L. Burbank and R. D. Reger. 
64 QUATERNARY GEOLOGY OF ALASKA 

solifluction conditions on the north side of the Tanana 

valley. 

In many areas the frost-rived debris contains less fine 

material and less water and consists of angular fragments of well-jointed, resistant rock such as quartzite, 

basalt, or andesite. Under such circumstances 

solifluction lobes do not commonly occur; instead, conspicuous sheets or streams of angular rubble form. 

These rubble sheets consist of angular to semirounded 

bedrock fragments a few to 60 em in diameter; they form 

a blanket 30 em to 2 m thick on slopes and hills. These 

sheets may be hundreds of metres long and wide. Active 

rubble sheets occur in northern and western Alaska, 

but little is known of the mechanics of movements and 

distribution. 

The best documented inactive rubble sheets in 

Alaska are on Jumbo Dome on the north side of the 

central Alaska Range (Wahrhaftig, 1949). Here the 

evidence indicates at least five periods of rubble-sheet 

formation on the andesite dome, interspaced with 

periods of dissection. The sheets are between elevations 

of900 and 1,200 m and were active during times of more 

rigorous climate. The snowline was 370m lower during 

Wisconsinan time (Wahrhaftig, 1949, p. 220), and 

periods of rubble-sheet formation are correlated with 

glaciations in the Alaska Range. The youngest rubble 

sheet may be correlative with the late Wisconsinan 

glacial stage. 

In the Amphitheater Mountains on the south side of 

the central Alaska Range along the Denali Highway, 

rubble sheets of Wisconsinan age occur at 1,200 m 

(Pewe, 1965c, fig. 7-39). The rubble was derived from 

higher slopes during formation of altiplanation terraces 

during the rigorous climate of the Denali (Wisconsinan) 

Glaciation (table 2; Pewe, 1961c, D200-D201; 1965c). 

The rubble overlies till of Illinoian age. 

Rock glaciers, tongue-shaped or lobate masses of unsorted, angular frost-rived material with interstitial ice 

(if active) and with steep lichen-free fronts 10-100 m 

high, are one of the most spectacular periglacial deposits (fig. 34) but are limited in aerial extent. They are 

150-3,200 m wide and 300-1,600 m long, and in Alaska 

most of them occur in cirques. Rock glaciers are abundant in the Talkeetna Mountains and the Chugach 

Range and were reported by Capps (1910a) and Moffit 

and Capps (1911, p. 52) from the Wrangell Mountains 

(fig. 34). They are widespread in the central Alaska 

Range (Wahrhaftig and Cox, 1959; Foster and Holmes, 

1965). 

Active rock glaciers occur below snowline, and a 

study of topographic maps and aerial photographs indicates that they are at an elevation of approximately 

1,600 m on the north side of the Alaska Range, at 1,500 

m in the Talkeetna Mountains,- at 1,200 m in the 

Chugach Range, and at 1,150 min the Wrangell Mountains. Porter (1966, fig. 85) reported active rock glaciers 

at an elevation of 1,600-1,800 min the central Brooks 

Range. 

The most detailed study of rock glaciers in Alaska 

was by Wahrhaftig and Cox (1959) in the central Alaska 

Range. They defined a rock glacier as a type of glacier 

formed under the influence of a periglacial climate in an 

area lacking the net accumulation of snow required for 

a conventional glacier to form. A permafrost environment must be present (mean annual air temperature 

colder than 0°C) to enable the snow and water which 

trickles down into the interstices between the rocks to 

remain as ice. The abundant supply of coarse blocky 

debris necessary for formation of rock glaciers is most 

often found at the base of cirque walls. A periglacial 

climate with its intense frost action is ideal for frost 

riving of the fractured bedrock of the cliffs. 

Active rock glaciers move slowly. Measurements of 

one rock glacier in the central Alaska Range by Wahrhaftig and Cox (1959, p. 383) indicate that it moved at 

the average rate of 73 em annually from 1949 to 1957. 

An active rock glacier is in equilibrium with a climate necessary to produce the frost-rived debris and to 

permit the interstitial ice to exist. The rock glacier 

becomes inactive when these climatic conditions are not 

met and thus loses its steep front, interstitial ice, and 

forward motion. In Alaska, inactive rock glaciers can be 

found at lower elevations than the presently active 

ones, and no doubt they represent the lowering of snowline and changing of other climatic parameters in the 

past. Wahrhaftig and Cox (1959) carefully showed that 

an understanding of rock glaciers permits an interpretation of paleoclimatic conditions. They documented 

many post-Wisconsinan inactive rock glaciers in the 

Alaska Range. In the central Alaska Range, they stated 

that the rock glaciers formed in two separate cold 

periods that occurred after the post-Wisconsinan thermal maximum. Almost all inactive rock glaciers in 

Alaska occur in Wisconsinan cirques and must therefore be post-Wisconsinan in age; however, at an elevation of 1,200 m along the Denali Highway between the 

Tangle Lakes and MacLaren River, inactive rock 

glaciers(?) of Wisconsinan age are reported (Pewe, 

1965c, p. 91). In the Anuktuvuk Pass area, Porter (1966, 

fig. 85) found inactive rock glaciers at elevations from 

1,200 to 1,500 m. 

Rock glaciers in Alaska are excellent records of late 

Holocene events, but only in the central Alaska Range 

have they been used in interpreting the history of the 

last tens of thousands of years (W ahrhaftig and Cox, 

1959). A great opportunity exists in most of the mountains in Alaska to document this span of history carefully by means of rock glaciers. 
PERMAFROST AND PERIGLACIAL DEPOSITS 65 

FIGURE 34-Rock glacier on Sourdough Peak in the southern foothills of the Wrangell Mountains 13 km east of McCarthy. View looking 

north. Photograph by Bradford Washburn. 

THERMOKARST FEATURES 

One phenomenon restricted to the periglacial landscape is thermokarst topography. The thawing of permafrost creates an uneven topography which consists of 

mounds, sinkholes, tunnels, caverns, short ravines, 

lake basins, and circular lowlands caused by melting of 

ground ice. Thermokarst f3atures differ from other 

periglacial phenomena inasmuch as they are not 

formed by the repeated freeze and thaw of bedrock with 

subsequent breakup of the rock and transfer of the debris; they are the result of thawing of permafrost and 

associated ground ice, and they form either by warming 

of the climate or by artificial or natural removal of the 

overlying vegetation cover. 

Thermokarst features have been noted in Alaska for 

many years. In the Arctic Coastal Plain, modern and 

ancient lake basins (Black and Barksdale, 1949; Black, 

1969b; Britton, 1958a, b; Tedrow, 1969) as well as 

ravines (Anderson and Hussey, 1963) and polygonal 

topographic microrelief (Hussey and Michelson, 1966) 

(fig. 28) are widespread. Sinkholes and lake basins are 

reported from the Seward Peninsula (Hopkins, 1949) 

and central Alaska (Wallace, 1948; Pewe, 1965a, 1966c, 

p. 27). Mounds and pits are abundant in cultivated fields 

near Fairbanks (Pewe, 1949, 1954). 

Despite these observations, no systematic studies of 

the thermokarst topography have been made on aregional basis such as those done in the U.S.S.R. (See 

references in Czudek and Demek, 1970.) Several areas 

in central Alaska appear to exhibit well-developed, 

widespread thermo karst topography, such as the lakepitted plains on the south side of the Yukon Flats (pl. 1). 

The same type of topography in the middle reaches of 

the Tozitna River may yield basic data on the origin of 

thermokarst topography and the regional history of 

permafrost. 
66 QUATERNARY GEOLOGY OF ALASKA 

Ice wedge casts are one of the features ofburied thermokarst topography that have been used in the interpretation of Quaternary climates; however, recognition of other interesting thermokarst features is rare, 

although ancient slumping and gulleying are known in 

the Fairbanks area (Pewe, 1952a, 1965a). 

GEOBOTANICAL PERIGLACIAL FEATURES 

Two periglacial geobotanical features that are well 

developed in Alaska but have not been studied, even in 

a reconnaissance manner, are palsas and string bogs, 

which are geobotanical features related to permafrost 

and seasonal freezing of the ground; they have been 

studied in the subarctic in Europe, Asia, and Canada. 

Palsas are mounds of peat and ice, 1-7m high and 

10-50 min diameter, that occur in bogs. They protrude 

well above the level of the bog, have a rather hard and 

dry surface, and are generally blown clear of snow in the 

winter. The segregation of ice in thin layers and in 

bodies 2m thick is palsas, plus the accumulation of peat, 

accounts for their formation. Palsas are thought to belong to the southern region of discontinuous permafrost 

(Lundquist, 1969). They are well developed and abundant along the Denali Highway west of the MacLaren 

River valley on the south side of the Alaska Range and 

are probably widespread in the nearby upper Susitna 

valley and perhaps in the upper Kuskokwim valley. The 

grass and peat-covered pingos reported near Bethel in 

the Yukon-Kuskokwim Delta by Burns (1964) are 

thought by the writer to be palsas (fig. 31). 

Though Alaska is an ideal place to study pals as and to 

learn more of their origin, age, and relation to the glacial record and permafrost, thus far only one has been 

investigated, a dissected palsa in the MacLaren River 

valley. The feature was termed a peat pingo, and 

a radiocarbon date of 10,565±225 years (GX-0249) 

(Pewe, 1965c) (table 2) was obtained from the peat at the 

upper contact with the clear-ice core. This paisa was 

photographed (Hamelin and Cook, 1967, p. 29) and discussed during the 1965 Alaska-INQUA field excursion. 

A nearby undissected paisa has also been photographed 

(Jahn, 1966, p. 93). 

String bogs (strangmoore; tourbiere reticulee) are 

boggy areas marked by a gentle undulating surface 

characterized by long, low serpentine moss ridges alternating with long, water-filled swales. The ridges or 

ttstrings" are 1-3m wide and as much as 1m high. They 

trend across the bog generally at right angles to the 

areal drainage. Troll (1944, p. 72-7 4) reported them 

from various parts of Europe, Asia, and Canada. 

The only detailed study of their origin was done 40 

years ago in Finland by Auer (1920), who believed that 

they are produced by seasonal ice growth under ridges 

which are generally blown clear of snow. Different 

moisture situations permit certain species of moss and 

other plants to grow on the ridges while other species 

grow in the wetter swales. Auer concluded that string 

bogs are an expression of seasonal frost and are not 

related to permafrost. 

There is considerable controversy at present over the 

origin of string bogs, and other ideas of origin concern 

their relation to solifluction and to permafrost. Schenk 

(1966) stated that string bogs are the result of collapse 

of formerly perennially frozen bogs when permafrost 

disappears. Rapp and Annersten (1969) strongly objected to this idea. 

String bogs are excellently developed and widespread 

in the lower Susitna River valley and other drainages 

from the Alaska Range and are well exhibited in bog 

fiats of the western Kenai Peninsula. Drury (1956) 

studied bogs in the upper Kuskokwim River region and 

discussed them in detail. However, string bogs are 

poorly developed, if at all, there and in central Alaska. 

They are best formed near the southern border of permafrost. Although the writer has examined them from 

the air and on the ground and although photographs of 

these bogs were published by Schenk (1966) and in a 

classic paper on Alaskan bogs (Drury, 1956), no research has been undertaken to determine their origin 

and relation to the glacial record and permafrost distribution. 

SUMMARY 

Permafrost is perhaps the most impressive periglacial phenomenon in Alaska. Currently present in about 

82 percent of the State, it was more extensive in glacial 

cold periods and less extensive in past interglacial 

periods. It is more continuous, thicker, and colder north 

of the Brooks Range than in central Alaska. Although 

permafrost is forming today in most of Alaska, much of 

the deep-lying permafrost is not in thermal equilibrium 

with the present climate. 

Ground ice, the most significant feature in permafrost 

affecting human activity in the north, is a key factor in 

the creation of microrelief and macrorelief forms and 

provides evidence useful in the interpretation of Wisconsinan and Holocene geologic history. Although detailed studies of ground ice have been made, more are 

needed, and new information is becoming available 

with increased engineering construction in central and 

northern Alaska. New information is now available 

concerning pingos in central Alaska and even under the 

shelving shores of the Arctic Ocean. 

Periglacial processes are active, and periglacial erosional and depositional landforms are widespread in 

Alaska. The landforms and deposits are mainly Wisconsinan and Holocene in age, but some Illinoian and preIllinoian forms and deposits exist and are excellent 

clues for the reconstruction of geologic history and 
FLUVIAL DEPOSITS 67 

paleoclimates. Some provide opportunity for more critical work, especially periglacial geobotanical features 

such as palsas and string bogs. 

FLUVIAL DEPOSITS 

Some 10 percent of Alaska may be covered by fluvial 

deposits, if the overlying loess blanket on the terraces is 

excluded (fig. 1). In addition to low- and high-level terraces and modern flood plains of rivers, huge areas of 

glacial outwash fans flank most major mountain 

ranges. Many large tectonic basins (Payne, 1955), such 

as the valleys of the Kuskokwim and Tc:nana Rivers, 

the Yukon Flats, and Yukon-Koyukuk lowland, are 

filled with 1 to a few hundred metres of fluvial sediments of Quaternary age. Extensive areas of delta deposits occur in western and northern Alaska. 

A complex Quaternary history is recdtded by the 

fluvial deposits in Alaska, but only in the last 25 years 

have systematic investigations of fluvial deposits been 

undertaken, particularly in connection with various 

engineering geology projects of the U.S. Geological Survey. 

YUKON FLATS 

One of the most extensive areas of fluvial deposits in 

Alaska is in a tectonic basin termed «the Yukon Flats 

basin" (Miller and others, 1959), which lies along the 

Yukon River south of the Brooks Range and north of the 

Yukon-Tanana Upland. According to Williams (1962), 

the basin includes two physiographic units: the Yukon 

Flats and the marginal upland. The Yukon Flats is a 

broad lowland, approximately 23,000 km2 in extent, 

which lies along the Yukon River and its tributaries 

and includes flood plains, terraces, alluvial fans, and 

small areas of sand dunes. The marginal upland, occupying an area of more than 12,000 km2 around the 

edge of the basin, is 30--150 m above the alluvial lowland and consists of a thick sequence of older alluvial 

deposits of the Yukon and its larger tributaries and of 

alluvial aprons formed by small streams draining the 

adjoining highlands. The fluvial deposits of the upland 

are a few to more than 30m thick, but in the center of 

the flats near Fort Yukon, 30 m of fluvial deposits of 

Quaternary age overlies more than 90 m of lacustrine 

deposits (Williams, 1960, 1962); the lowest part of the 

lacustrine deposits contains a pollen flora of late 

Pliocene or early Pleistocene age (Williams, 1960, 

1962). 

The high-level alluvium consists of rounded pebble to 

cobble gravel with lenses of sand and silt. These fluvial 

deposits are remnants of a system of high river terraces 

and are late Tertiary and early Quaternary in age (table 

3). A very small pollen flora from an exposure of the 

alluvium at Birch Creek suggests that this high-level 

gravel is the same age as lake deposits in wells at Fort 

Yukon (E. B. Leopold, written commun., 1959). 

In the central and eastern part of the Yukon Flats, 

large alluvial fans and related terraces of the Yukon 

and its tributaries that drain the Brooks Range cover an 

area of thousands of square kilometres. The higher and 

older parts of these fans are correlated with the early 

and middle Pleistocene morainal complexes in the 

southern Brooks Range (Williams, 1962) (table 3). The 

stream deposits of the older fans and terraces are, where 

observed, heavily iron stained and slightly cemented by 

iron oxide. Younger alluvial fans and related terraces 

that can be traced to the younger glacial moraines in the 

Brooks Range are thought to be of middle and late 

Pleistocene age (table 3). The apices of the younger fans 

are at lower elevations than those of the older fans, but 

toward the Yukon River the younger fans appear to 

bury the older ones. 

Major streams today have wide flood plains, and flood 

plain and low terrace alluvium cover thousands of 

square kilometres. The alluvium is of late Pleistocene 

and Holocene age and is still being deposited at the 

present time. 

TANANA RIVER VALLEY 

The upper Tanana River valley, upstream from 

Cathedral Bluffs, is 160 km long and 15-30 km wide. 

Drainage is poor, and many lakes dot the surface. Fluvial and glaciofluvial sediments have accumulated here 

for at least the last half of the Quaternary Period; the 

total thickness of sediments is unknown. Most of the 

sediments poured into the valley from the Alaska 

Range on the south in the form of glacial outwash fans 

and alluvial fans. Wallace (1948) and Black (1951a, 

1958) held that much of the sediment in the upper 

Tanana valley may be lacustrine. The most detailed 

work in this area was done by Fernald (1965b), who did 

not recognize widespread lacustrine deposits; he described outwash, alluvium, and sand dunes (table 3). 

The middle Tanana Lowland is a 21,000-km2 basin 

between the Alaska Range on the south and the 

Yukon-Tanana Upland on the north and extending 

from near Big Delta on the east to near Manley Hot 

Springs on the west. It is a structural basin, the floor of 

which is below sea level in much of the trough (Pewe, 

1958b; Williams and others, 1959; Barnes, 1961; Andreasen and others, 1964). Quaternary deposits 

120--180 m thick are largely an accumulation of fluvial 

and glaciofluvial sediments shed from the rising Alaska 

Range. This deposition pushed the Tanana River to the 

north against the Yukon-Tanana Upland (Mertie, 1937, 

p. 22; Pewe, 1958b). The sediments bury a fairly rugged 

topography, the hilltops of which now form small knobs 

above the plain. Well-drained fans 50 km long flank the 

Alaska Range. The northern part of the basin consists of 

a swampy flood plain and the terraces of the Tanana and 
68 QUATERNARY GEOLOGY OF ALASKA 

smaller streams. In the western part of the basin, fluvial 

deposits are covered with a thick blanket of eolian sand. 

Pewe, Wahrhaftig, and Weber (1966) suggested that 

in Illinoian time, when glaciers were more extensive on 

the north side of the Alaska Range than now, great 

alluviation occurred in the basin, and several lakes, 

which still exist today, were formed between the fill and 

the Yukon-Tanana Upland (Blackwell, 1965). Some of 

the fill may be related to continuing tectonic activity. In 

Sangamon time the rivers cut down, forming prominent 

terraces 30 m high along the Tanana River upstream 

from Fairbanks and in the huge outwash fan of the 

Wood River in the southern part of the basin. In Wisconsinan time alluviation was renewed, especially along 

the glacial streams, and was followed by local dissection 

in Holocene time. 

KUSKOKWIM REGION 

In the vicinity of Lake Minchumina, between the 

middle Tanana Lowland and the upper Kuskokwim 

region, is a lowland 80 km wide blanketed partly with 

fluvial sediments. Little is known yet about this region, 

although the Quaternary history is perhaps similar to 

that of the upper Kuskokwim region (Fernald, 1960), a 

15,000-km2 lowland and bordering piedmont between 

the Alaska Range on the southeast and the Kuskokwim 

Mountains on the northwest (pl. 1). Fernald (1960) 

showed that more than half of the are~ is underlain by 

fluvial deposits of flood plains, outwash plains, and alluvial fans. Fluvial sedimentation on the south side of 

the basin pushed the Kuskokwim River northward 

against the edge of the Kuskokwim Mountains. A well 

at McGrath reveals 70 m of fluvial sediment, and a well 

at Farewell, near the foot of the mountains, penetrated 

110m of unconsolidated sediments, most of which are 

fluvial, although a small amount may be glacial (A. T. 

Fernald, oral commun., April 16, 1969). 

The outwash plains and fans are composed of wellrounded boulder, cobble, and pebble gravel that becomes increasingly fine downstream. The fluvial deposits of the Kuskokwim River flood plain are mainly 

silt and sand with only local beds and lenses of gravel. 

Considerable organic material is present. Much of the 

lowland is covered with bogs (Drury, 1956) that are 

several hundred square kilometres in extent. 

The history of fluvial deposits is related to glacial 

advances from the nearby Alaska Range. In Illinoian 

time (thought to be Wisconsinan(?) by Fernald, 1960, p. 

268) considerable alluviation occurred, and dissection 

followed in Sangamon time. In Wisconsinan time, more 

fluvial deposits were laid down, and the major rivers, 

especially near the Alaska Range, are aggrading today, 

according to Fernald (1960), p. 269). 

KOYUKUK RIVER VALLEY 

Extensive lake-dotted lowlands underlain by fluvial 

deposits occur in the Koyukuk valley. The largest lowland, and the only one that has been investigated, is the 

Yukon-Koyukuk lowland, where the Koyukuk River 

joins the Yukon River (Weber and Pewe, 1970) (fig. 35). 

The Yukon-Koyukuk lowland is an unglaciated area of 

10,000 km2 that was subject to alternating periods of 

great deposition and erosion. Quaternary fluvial deposits are more than 126m thick in places, and locally, a 

few bedrock knobs project above the alluvium. It cannot 

be ruled out that some of these sediments may be estuarine (Eardley, 1938), because the major rivers in the 

area are only 30m above sea level today and much of the 

bedrock floor is 50--100 m below sea level. 

The low land consists of two major terraces and broad 

flood plains of the Yukon and Koyukuk Rivers. The 

terraces, composed of silt and locally of sand, are 10--75 

m above the flood plain (Weber and Pewe, 1961, p. 

D371). 

The flood plains of the Yukon and Koyukuk Rivers in 

this area are classic examples of development of flood 

plains by meandering rivers under subarctic conditions 

(Pewe, 1947). The flood plains are composed of four 

mappable units, each successively older: linear, advanced linear, coalescent, and scalloped; the units are 

arbitrary phases in the development of the flood plain 

(fig. 35). The classification of these flood plain units has 

been extended successfully to the flood plain of the Kuskokwim River (Drury, 1956). The four units can be 

distinguished on the basis of shape of the lakes, vegetation, shape and position of the unit, depth to permafrost, 

amount of ground ice and organic material, as well as 

character of the river bank and distribution of driftwood 

(Pewe, 1948, p. 8), and can be easily distinguished on 

aerial photographs and maps. 

Precise dating of the events in the area is not yet 

possible; however, tracing the periods of alluviation to 

the mountains suggests that deposits forming the high 

terrace accumulated during Illinoian time (table 3). 

This was followed by terrace formation with downcutting in Sangamon time. Inasmuch as this area is only 

30--60 m above sea level, however, the fluctuations of 

sea level in Quaternary time may have reversed the 

period of downcutting from interglacial to glacial time, 

similar to events in the lower Mississippi River valley 

(Fisk and MacFarlan, 1955). Also, movement along the 

Kaltag fault may have complicated the Quaternary history of the valley (Patton and Hoare, 1968). Bones of 

Pleistocene land mammals have been found in deposits 

of the oldest terrace, but none have been reported from 

younger units. 

In Wisconsinan time, alluviation occurred and dissec-
FLUVIAL DEPOSITS 69 

FIGURE 35.-High-altitude oblique aerial photograph looking south 

toward the junction of the Yukon and Koyukuk Rivers. The 

Koyukuk River (dark color) joins the silt-laden Yukon River 

(light color) at the right. Flood plain units indicated by number 

tion followed, possibly at the end of Wisconsinan time, 

forming low terraces. A radiocarbon date of 8,140±300 

years (W-472) (Rubin and Alexander, 1958, p. 1479) 

was obtained from organic material taken from frozen 

organic-rich silt of the scalloped phase of the flood plain. 

Therefore, the formation of much of the modern flood 

plain postdates this time (Pewe, 1962), and the lowest 

terrace is more than 8,000 years old. 

OTHER FLUVIAL BASINS 

In addition to the major fluvial basins where geologic 

investigations have been undertaken, many major and 

are the (1) linear phase, (2) advanced linear phase, (3) coalescent 

phase, and (4) scalloped phase. Unit (5) is the high terrace. Photograph by U.S. Army Air Corps, August 24, 1941. From Pewe, 

(1948) and Weber and Pewe (1961). 

minor river valleys with large areas of fluvial deposits 

exist (pl. 1) about which little or nothing is known, 

except for casual references or generalized mapping as 

reported in the early bulletins of the U.S. Geological 

Survey devoted mainly to bedrock geology. Little is 

known, for example, of the fluvial deposits in the Innoko 

Lowland of western Alaska or of the Holitna lowland in 

the middle Kuskokwim region. The Kobuk and Noatak 

River valleys in the western Brooks Range contain extensive fluvial sediments, especially in their lower 

reaches, but to date mostly reconnaissance information 

(Fernald, 1964) is available. 
70 QUATERNARY GEOLOGY OF ALASKA 

NORTHERN ALASKA 

The Arctic Slope of Alaska contains extensive fluvial 

deposits about which little is known except for recent 

studies along the route of the Alaskan oil pipeline. The 

two physiographic provinces that lie north of the Brooks 

Range and compose the North Slope are the Arctic 

Foothills and Arctic Coastal Plain provinces (pl. 1). 

The Arctic Coastal Plain province is almost completely blanketed by the Gubik Formation of Pleistocene age (Gryc and others, 1951, p. 167; Black, 1964). 

Only part of the Gubik Formation consists of fluvial 

sediments (Coulter and others 1960; Faas, 1966); most 

of it is composed of unconsolidated marine deposits. 

Fluvial deposits of Pleistocene age in the Arctic 

Foothills province consist of numerous terrace deposits 

along the major streams. In the Utukok-Corwin area of 

northwestern Alaska, Chapman and Sable (1960, p. 

128-129) reported Quaternary gravel deposits 4.5--7.5 

m thick, capping terraces 6--150 m above major rivers. 

As many as three levels of terraces are recognized. The 

position of the terraces may indicate uplift or changes in 

the fluvial regimen caused by glaciation during 

Quaternary time. 

Conspicuous terraces covered with gravel exist along 

the middle and upper Colville River. In the eastern part 

of the Arctic Foothills province, the major rivers also 

are flanked by Pleistocene terrace deposits, but no detailed studies have been made. 

DELTAS OF YUKON, KUSKOKWIM, 

AND COLVILLE RIVERS 

The delta of the Yukon-Kuskokwim Rivers is a large 

area of fluvial sedimentation that undoubtedly records 

a complex history of alternating marine and freshwater 

deposition, probably like the Mississippi River Delta. 

The delta of the Yukon-Kuskokwim Rivers, about 

62,000 km2 in extent, is a vast lowland 15--60 m above 

sea level and is termed the ((Bethel Basin" by Miller, 

Payne, and Gryc (1959, pl. 1). Local bedrock knobs protrude through the sediments; some are of the basement 

rock, and others are volcanic cones of Quaternary age 

(Coonrad, 1957; Hoare and Condon, 1971). 

Subsurface data are needed to interpret the history of 

these deltaic sediments; to date, only 14 water wells, 

one attempted oil well, and two core tests have penetrated the delta in the Yukon-Kuskokwim area. The 14 

water wells near Bethel (Waller, 1957) penetrated as 

much as 184m (Feulner and Schupp, 1964) of silt and 

fine sand, with sparse gravel layers, without reaching 

bedrock. The presence of wood chips and bark in the 

sediments suggests freshwater or estuarine deposits. A 

wood fragment, believed to have come from just below 

the base of permafrost, has been dated as older than 

34,000 years (W-1287) (Feulner and Schupp, 1964). The 

Pan American Oil Co. drilled a well near N apatuk 

Creek and penetrated 296 m of Quaternary(?) sediments before reaching old rocks (William Van Alen, 

written commun., Mar. 14, 1963). Tests of the Pleistocene foraminifer,Elphidium orogonese, were found at 

a depth of 195 m in this well. The Quaternary sediments, which contained wood chips and usnail" shells, 

have not yet been studied in detail, but no doubt many of 

the sediments are of marine origin, deposited during 

marine transgressions. 

The subsurface of the delta of the Colville River in 

northern Alaska is even less known. It is considerably 

smaller than the Yukon-Kuskokwim Delta and undoubtedly frozen to greater depths. Walker and his associates are currently studying the surface of the delta 

and its erosional processes (Walker and Morgan, 1961, 

1964; Walker and Arnborg, 1966; Walker, 1967; Walker 

and McCloy, 1969). 

AURIFEROUS GRAVEL OF CENTRAL ALASKA 

Perhaps the most famous of the fluvial deposits of 

Alaska and adjoining Yukon Territory, Canada, are the 

late Tertiary(?) to middle Quaternary auriferous creek 

and river gravels now buried by frozen silt or other 

sediments. These gravel deposits are almost entirely 

confined to unglaciated central Alaska and, in most 

instances, are buried by retransported loess. Although a 

large part of the geologic literature on central Alaska is 

associated in some way with placer gold deposits, emphasis has not been on the Quaternary history of the 

deposits. Since 1945, the emphasis has shifted. 

Not all is yet published, but considerable material 

has been assembled on Quaternary stratigraphy of 

nonglacial fluvial deposits in the Yukon-Tanana Upland (Pewe, 1952a, 1958b, 1965a, 1975; D. M. Hopkins, 

1963, unpub. data), the Seward Peninsula (Hopkins, 

1963; unptib. data), the Platinum area (Hopkins, field 

notes), and the adjoining Klondike area near Dawson, 

Yukon Territory (0. L. Hughes, written commun., 1962). 

The lithology of the buried gravel varies widely depending upon the locality. Cobb and Kachadoorian 

(1961), among others, described the auriferous 'gravel 

deposits. The larger streams typically have rounded 

river gravels, but the hundreds of small creeks have 

gravel that is characteristically angular and poorly 

sorted. Most of the gravel represents solifluction material that has been transported only short distances by 

stream action. The placer gold generally lies on bedrock 

or in the basal gravel, but in some places gold may be 

concentrated in the gravel section (Pewe 1952a). In 

glaciated areas on or in stratified glacial drift (Mertie, 

1925, p. 241), the gold may be on ((false" bedrock. The 

thickness of gravel varies from several centimetres to at 

least 74 m, the latter recorded under 57 m of silt near 

Fairbanks (Pewe, 1958b, boring log No. 78). 
LACUSTRINE DEPOSITS 71 

The Fairbanks area is one locality where the auriferous gravels have been studied (Pewe, 1952a, 1958b, 

1965a, 1975; Anderson and Johnson, 1970). In late 

Tertiary or early Quaternary time, creeks in the area 

began to alluviate, and rich gold placers were buried 

under 3-75 m of coarse, very angular, local, sandy 

gravel. This gravel has been stained brown by percolating ground water. The alluviation may have been 

caused in part by tectonic action and in part by raising 

of local base level, the Tanana River, as a result of 

glacial advances in the nearby Alaska Range. This 

early period of gravel deposition was followed by erosion 

and removal of most of the gravel. Streams reconcentrated much of the gold in the earlier placers and deposited additional geld placers. Most of the stream channels of the second gold placer concentration are offset 

from the location of the earlier channels, and therefore 

some of the first placer accumu!:::ttions still exist as 

fragmentary bench deposits (Pewe, 196F;3, fig. 109) (fig. 

20). A second cycle of gravel alluviation followed. The 

younger gravel is not stained as dark a brown as the 

older deposit and so is easily differentiated from the 

older in gold dredge tailing piles of the Fairbanks area. 

Both gravel deposits are unconformably overlain by 

loess, or if in valley bottoms, by retransported loess rich 

in organic remains (fig. 20). 

The younger gravel deposit appears to be definitely 

Quaternary in age because it contains the tusks and 

bones of mammoths. Identifiable wood remains are 

rare, but white spruce is recorded. The poorly sorted, 

angular gravel grades into, and in some places is overlain by, solifluction deposits thought to have originated 

under periglacial climatic conditions. · 

In almost all creeks, both gravel deposits lie on a 

3-cm- to 2-m-thick auriferous clay layer thought toresult from decomposition of the underlying bedrock. 

Whether the clay resulted from pre-Pleistocene weathering or formed by percolation of ground water during 

Pleistocene time is currently being studied by the writer and his associates. (Bell, 197 4) 

If the age of the gravel is Quaternary, it is early to 

middle Quaternary because the deposits are deeply 

buried under two or more reworked silt deposits of considerable antiquity. Because of the antiquity, faunal 

content, and probable origin under rigorous climatic 

conditions (solifluction), the older gravel deposit of the 

creeks in the Fairbanks area is thought to be Pliocene to 

Pleistocene in age, and the younger gravel deposit is 

thought to be early to middle Pleistocene (Pewe, 1975.). 

In some glaciated areas, buried placers and associated gravel deposits are known to be Quaternary in 

age, although details of their ages are not yet available 

(Mertie, 1925, p. 241). 0. L. Hughes (written commun., 

1962) of the Geological Survey of Canada stated that the 

high-level auriferous gravel deposits of the Klondike at 

Dawson, Canada, near the Alaska-Canada border are 

pre-Pleistocene in age, but the auriferous gravel deposits of the inner valleys of the area are early Pleistocene. 

LACUSTRINE DEPOSITS 

Known lacustrine deposits are relatively limited in 

Alaska, and only one large area, the Copper River 

Basin, exhibits widespread, well-developed lake deposits. In the early days of geologic reconnaissance in 

Alaska, several workers reported Quaternary lake deposits throughout the central part of the State. This 

concept was based on the presence of a widespread 

blanket of well-sorted tan silt on the valley slopes, valley bottoms, and on the tops of low hills throughout 

central Alaska. Spurr (1898, p. 20~230) was the first to 

consider some of the silt in the Yukon River area as 

lacustrine in origin. Prindle (1913, p. 50) extended this 

concept to the upland silts of central Alaska. 

CENTRAL ALASKA 

The strongest support for the existence of widespread 

bke deposits in central Alaska came from Eakin (1916, 

p. 73; 1918, p. 45), who postulated two vast inland lakes. 

One lake is thought to have existed in the Yukon Flats 

and Porcupine River valley. It was supposed to have 

been formed when the middle Yukon, which was assumed to have flowed north up the Porcupine to the 

Arctic, was blocked by glaciers in the present upper 

regions of the Porcupine River. This hypothetical lake 

later drained to the southwest by cutting through a 

bedrock constriction near Rampart. The other lake was 

created when the Tanana-Nowitna drainage, supposed 

to have flowed south to the Kuskokwim River basin, 

was blocked by glacier tongues extending northwest 

from the Alaska Range. Later this lake drained by cutting through a bedrock ridge near Ruby. 

The existence of these large lakes was seriously questioned by A. H. Brooks (in Eakin, 1916, p. 9). The concept of lacustrine origin for the upland silt in central 

Alaska is considered invalid for several reasons: The 

glacier barriers cannot be demonstrated to have existed; shorelines ·and deltas are absent; the silt is present above the 360-m level, the upper level of the lakes; 

no stratification exists in the silt; little clay is present; 

no lacustrine fossils are found in the upland silt; and 

mud cracks and ripple marks are unknown (Pewe, 1955; 

p. 715-716). 

Although the middle and late Quaternary deposits, 

now known to be loess, around the Yukon Flats do not 

indicate a lake at that time, it is noteworthy that Williams (1960) reported lake sediments 45 m below late 

Quaternary deposits in a borehole at Fort Yukon. Williams believed that the presence of at least 89 m of 
72 QUATERNARY GEOLOGY OF ALASKA 

relatively uniform, fine-textured sediments and the 

topographic form of the basin suggested a large lake; 

palynology indicates a late Tertiary or early Quaternary age. (See p. 67.) 

Instead of a lake formed in the Yukon Flats and 

Porcupine River valley in Wisconsinan time by glacier 

blockage in the upper regions of the Porcupine, recent 

work indicates that a different situation existed. In 

Wisconsinan time, glaciers in the Yukon Territory 

blocked river drainage in the upper Porcupine, and a 

large lake formed in Old Crow Flats near the Alaska 

border (0. W. Geist, 1949, T. D. Hamilton, 1970, 0. L. 

Hughes, 1971, all oral communs.). The lake overflowed 

a bedrock divide and drained largely to the southwest 

down the Porcupine River into the Yukon Flats. 

Black (1951a, p. 100; 1958,p. 79) stated that a lake 

about 4, 700 km2 in extent existed in the upper Tanana 

valley from Tetlin to the Canadian border and drained 

southeast into Canada. The silt and sand deposits in the 

area were therefore assumed to be lacustrine in origin. 

Fernald (1965a, b), however, believed that the sand and 

silt, as well as the gravels of the upper Tanana valley 

area, are mostly glaciofluvial sediments and represent 

aggradation of the valley in middle and late Quaternary 

time rather than deposition into an extensive lake. 

NENANA RIVER VALLEY 

A small deposit oflacustrine clay in the Nenana River 

Gorge in the central Alaska Range is well documented 

(Wahrhaftig, 1958, p. 34-36). During the retreatoficeof 

the Healy Glaciation (table 2), the Nenana River gorge 

was occupied by a lake 0.5 km wide and 15 km long; this 

has been termed Lake Moody. The lake deposits are as 

much as 75 m thick and consist of blue and yellowishgray, varved silty clay. Delta deposits of coarse sand and 

gravel interfinger with the clay. The Alaska Railroad 

traverses the clay for several kilometres, and thawing 

of this perennially frozen clay produces serious landslide conditions (Wahrhaftig and Black, 1958, p. 

77-109). 

COPPER RIVER BASIN 

Lake sediments are widely distributed in the Copper 

River Basin, an intermontane basin about 14,000 km2 

in extent, bounded by the Chugach, Wrangell, and Talkeetna Mountains and the Alaska Range (fig, 36). It is 

termed a basin in this report, although listed as the 

Copper River Lowland by Wahrhaftig (1965). The basin 

is drained by rivers which flow in canyons (pl. 1) 

through the surrounding mountains that support large 

glaciers today and that contained much larger glaciers 

in the past. During Pleistocene glaeial cycles, glacial ice 

repeatedly blocked the exits from the basin, producing 

huge lakes (fig. 36). 

GLACIER ICE 

~"~ 4Mt Drum 

~ .... .!~~ f!fl 

~ 

{/ '· 

Chitna\ 

\h 

0 25 MILES 

I I 1 1 I I 

0 25 Kl LOMETRES 

FIGURE 36.-Extent of a lake in the Copper River Basin during the 

last major Wisconsinan glaciation. Modified slightly from Coulter, 

Hopkins, Karlstrom, Pewe, Wahrhaftig, and Williams (1965). 

The lacustrine sediments in the Copper River Basin 

were first reported by Mendenhall (1900, 1905) and by 

Schrader and Spencer (1901, p. 74), but detailed studies 

of the Quaternary glacial, volcanic, and lacustrine deposits were not undertaken until the 1950's. Only preliminary accounts of these studies were published (Ferrians and others, 1958; Nichols, 1956, p. 11-12; 1961, 

1963; Ferrians, 1963a, b; Ferrians and Schmoll, 1957; 

Ferrians and Nichols, 1965; Nichols and Yehle, 1961a, 

b; 1969). 

The Copper River and its tributaries have dissected 

the Quaternary sediments of the basin in Holocene 

times and now flow in steep-walled valleys and canyons 

as deep as 170 m. Lacustrine, glacial, fluvial, and volcanic mudflow deposits are well exposed in the valley 

walls (Ferrians and others, 1958). A generalized 

stratigraphic section of the deposits in the northeastern 

part of the Copper River Basin is shown in figure 

37 (0. J. Ferrians, unpub. data, 1964). 
LACUSTRINE DEPOSITS 73 

.-:-----:--:----::--:---,---, 1750 feet above sea level 

----Eolian deposits (cliff-head 

dunes) 9,400 years 

Lacustrine deposits (including 

diamicton) and tiU 

----38,000 years 

Fluvial deposits 

UNCONFORMITY 

Lacustrine deposits 

Fluvial deposits 

MINOR UNCONFORMITY 

Volcanic mudflow 

Fluvial deposits 

UNCONFORMITY 

Lacustrine deposits 

Till 

Lacustrine deposits 

X, position ofC-14 dated 

organic material 

FIGURE 37 .-Generalized stratigraphic section, northeastern part of 

Copper River Basin. Compiled by 0. J. Ferrians. 

The lacustrine deposits are, in many places, finely 

laminated, rhythmically bedded sand, silt, and clay 

with a few layers of volcanic ash (Nichols, 1960). The 

laminated silt and clay deposits are gray to bluish gray 

and dry with a blocky fracture. In some places the beds 

are folded by subaqueous sliding (Nichols, 1960). Many 

of the fine-grained deposits contain ice-rafted pebbles, 

cobbles, and boulders, and these grade laterally into 

well-sorted sand and gravel. Some of the beds were 

described as diamiction deposits (Ferrians, 1963a, b). 

Ripple marks are common in the ancient lake sands. 

The lake sediments deposited during the last major 

glaciation are as thick as 45 min the lower parts of the 

basin, but they are very thin along the margin of the 

basin. More than 5,000 km2 of the basin floor is underlain by these deposits. 

Apparently, a large lake formed in the basin during 

each major glaciation that blocked the rivers. During 

some pre-Wisconsinan glaciations, however, the ice expanded until it filled the basin, overriding previously 

deposited lake sediments and incorporating them into 

glacial material. Ferrians (oral. commun., 1962) found 

evidence in the northeastern part of the Copper River 

Basin of three major periods of deposition of lake sediments. No basis exists at the present time for relating 

these major periods of lake sedimentation to glacial 

sequences elsewhere in Alaska (table 2), except that the 

most recent episode began more than 38,000 years ago 

and ended shortly before 9,400 years ago (Ferrians and 

Schmoll, 1957). Ferrians believed that the three stratigraphic units of lake sediments probably represent 

episodes oflate and early Wisconsinan and Illinoian age 

(written commun., 1962), whereas the author views 

them as representing Wisconsinan, Illinoian, and preIllinoian episodes. 

In the southeastern part of the Copper River Basin, 

Nichols (oral commun., 1965) found evidence of three 

periods of lake-sediment deposition that correspond to 

those of Ferrians and, in addition, two or more older 

periods. The record of the last lake is clearest, not only 

because it is more recent, but also because the basin was 

not completely filled with glacial ice during this interval, and shorelines and deltas remain. The highest 

shorelines of this age reported by Ferrians and Schmoll 

(1957) in the northeastern part of the basin lie at an 

altitude of 750 m, but D. M. Hopkins and D. R. Nichols 

(unpub. data, 1954) observed lake sediments and 

shoreline features as much as about 975 m high in the 

western and northwestern parts of the basin. A 

radiocarbon date gives a minimum age of 9,400 years 

for the former lake at Gakona in the northeastern part 

of the Copper River Basin (Ferrians, 1963a, p. 120). 

The glaciolacustrine deposits are now perennially 

frozen and presumably became so as the lake withdrew 

(Nichols and Yehle, 1961a, p. 1080-1081; Nichols, 

1966). These lake beds are rich in ice and cause serious 

construction and ground-water problems (Nichols, 

1956, p.11-12). The ice-rich lake clays would present 

one of the most serious problems in the construction of 

an oil pipeline from northern Alaska to Valdez 

(Lachenbruch, 1970b). 

COOK INLET 

Lake clay has been reported from the Cook Inlet area. 

Near Anchorage, the Bootlegger Cove Clay, a lightgray to dark-greenish-gray silty to pebbly clay ranging 

in thickness from 1 to 7 5 m (Miller and Dobrovolny, 

1959, p. 41), underlies much of the local sand and clay 

(Trainer and Waller, 1965) and was the cause of the 

destructive slides during the 1964 earthquake (Hansen, 

1965; Shannon and Wilson, Inc., 1964). Karlstrom 

(1964) and Schmidt (1963) believed that the clay was 

lacustrine or estuarine in origin, but detailed studies of 

its Foraminifera obtained from continous drill cores by 

P. J. Smith (Hansen, 1965, p. A20) indicate that the 

entire unit is of marine origin. Schmoll, Szabo, Rubin 

and Dobrovolny (1972) demonstrated that the clay is 

14,000 years old and not middle Wisconsinan age as 

previously thought (p. 24). 

According to Karlstrom (1960b, fig. 154.1), a glacial 

lake 13,000 km2 in extent occupied the upper Cook Inlet 
74 QUATERNARY GEOLOGY OF ALASKA 

and lower Susitna valley in late Wisconsinan (Naptowne) time and deposits from this lake, ttLake Cook," 

covered the lowland and moraines of much of the Kenai 

lowland and the lower part of the Susitna valley (Karlstrom, 1964, 1965, fig. 9--47; Karlstrom and others, 

1964). However, the study of drill cores of the Bootlegger Cove Clay discussed refutes this interpretation. 

MIDDLE KOYUKUK RIVER VALLEY 

Large lakes are known to have existed in the Middle 

Koyukuk River valley near Allakaket in late Pleistocene time (pl. 1). Lake clays and drainage anomalies 

were noted by early workers. Hamilton (1969) outlined 

parts of these ancient lakes, among them two large 

ones, 780 and 520 km2 in area, which occupied part of 

the middle Koyukuk valley in nearly Wisconsinan 

time. These lakes were ponded by glaciers pushing 

south from the Brooks Range in Illinoian and 

Wisconsinan time. 

Much work remains to be done on the drainage 

anomalies and the determination of the extent of former 

lakes. R. D. Reger and T. L. Pewe (unpub. data, 1969) 

mentioned lake clay associated with Illinoian moraines 

along the northeastern base of Indian Mountain, 67 km 

southwest of Allakaket. Modern topographic maps, aerial photographs, and the use of helicopters will permit 

efficient study of these swampy lowlands. These studies 

will augment knowledge of the Pleistocene events in 

this area and will aid in planning roads and other construction on the lake clays, which are extremely susceptible to frost action. 

WESTERN BROOKS RANGE 

A large Wisconsinan proglacial lake, 60-70 km 

across, is thought to have formed in the Noatak River 

valley and its tributaries, between the De Long and 

Endicott Mountains of the western Brooks Range (Coulter and others, 1965). Most information concerning the 

lake comes from aerial photograph interpretation, and 

a great need exists for detailed information on character, extent, origin, and age of this lake, or lakes. 

SUMMARY 

Pleistocene lakes have been postulated for many 

areas of Alaska. Detailed work, however, indicates that 

the sediments of supposed lacustrine origin in central 

Alaska and the Cook Inlet area can best be ascribed to 

other origins. Lake deposits are present in the Copper 

River Basin and present a fine record oflate Pleistocene 

time, but most of the work on these sediments is as yet 

unpublished. Widespread lake deposits may have 

formed in the western Brooks Range area when glacial 

advances blocked drainages. The history and extent of 

these deposits have not yet been studied. 

MARINE DEPOSITS 

Alaskan marine deposits of Quaternary age now 

above sea level are limited to a narrow strip of land 

along the present coast, except in northern Alaska and 

perhaps in the Yukon-Kuskokwim Delta area. Most of 

the deposits were laid down during episodes of higher 

stands of the sea. 

Quaternary marine deposits were recognized in 

Alaska at the turn of the century (Spurr, 1900; 

Schrader, 1904), especially on the North Slope (Meek, 

1923), in southwestern Alaska, and on the Seward 

Peninsula (Dall, 1920). However, these isolated reports 

and later faunal studies were not, for the most part, 

placed in a firm stratigraphic perspective until the late 

1950's and 1960's (Hopkins, 1959b, 1965, 1967a, b; 

Hopkins and MacNeil, 1960; Hopkins and others, 1960; 

Hopkins and others, 1962). 

Hopkins (1967a) summarized existing knowledge of 

the distribution, correlation, paleontology, and paleoclimatic and tectonic implications of the Quaternary 

marine deposits of Alaska, and the following short 

summary is based mainly on his work. He divided the 

Quaternary marine deposits of Alaska into seven distinct ages on the basis of flora and faunal content, 

stratigraphic and geographic position, and paleomagnetic information. Deposits of each age represent a 

higher eustatic sea level and, therefore, marine sequences of transgression and regression. The marine 

transgressions affected wide areas simultaneously and 

have been given provincial names. He then attempted 

to correlate these transgressions and glacial sequences 

in western Europe and central United States, although 

only for the later part of the record because the ages of 

pre-Wisconsinan events are not precisely known for the 

classical areas (table 8). 

BERINGIAN TRANSGRESSION 

The type locality of the Beringian transgression is 

near Nome (fig. 38). The deposits consist of a few metres 

of gold-bearing and richly fossiliferous sand and clay 

(Submarine Beach), of marine origin, covered by till of 

the Iron Creek Glaciation (table 2) and are characterized by a molluscan fauna that has a decidedly modern aspect (although some assemblages are unlike any 

modern ones). Other bodies of marine sediments tentatively assigned to the Beringian transgression on the 

basis of their marine fauna are the lower part of the 

Gubik Formation (Schrader, 1904) on the lower Colville 

River and possibly at Skull Cliff near Point Barrow on 

the Arctic Coastal Plain; deposits of clay and sand 6-9 m 

above present sea level near the mouth of the Kivalina 

River; deposits on the Pribilof Islands (Cox and others, 

1966) and on some of the Aleutian Islands; and some of 

the upper part of the Y aka tag a Formation near Lituya 

Bay and on Middleton Island. Hopkins (1967a) sug-
MARINE DEPOSITS 

TABLE B.-Quaternary marine transgressions recorded on Alaskan coasts 

[After Hopkins (1967a)] 

Transgression Type locality 

Krusensternian Recent beach ridges at Cape Krusenstern. 

Woronzofian ___ ____ __ _ Bootlegger Cove Clay 

near Point Woronzof, Anchorage area (Miller and Dobrovolny, 1959). 

(Seep. 77 .) Pelukian ____ __ ____ __ Second Beach at Nome 

(Hopkins and others, 1960). 

Kotzebuan __ ____ _____ _ Marine beds below 

Illinoian drift along eastern shore of Kotzebue Sound (McCulloch and others, 1965). Einahnuhtan Einahnuhto Bluffs, St. Paul Island (Cox and others, 1966). Anvilian ____ ___ ____ _ Third Beach-Intermediate 

Beach at Nome (Hopkins and others, 1960). 

Beringian ___ ___ __ ____ Submarine Beach at 

0 

-20 

Nome (Hopkins and others, 1960). 

Vertical exaggeration 1 Ox 

Q){ Q) c:= [EJ· ::Qti: ··· .. : ... .· C,) • 

,g Beach gravel in 

o Norton Sound 

::r:: (Krusensternian) 

r·~ ·q~~: :J 

Alluvium 

j j ~] P{eat, Roe;. :~iollurium § ·~ Outwash and alluvial 

a ~ fan gravel of 

~ 6 Snake River 

Altitude of shoreline 

~ 

Climate as compared with the present 

Within 2m of present Same ------- ----------- sea level for deposits < 4,000 yr old. 

Probably a few metres Water colder; below present sea air colder. level. 

Two distinct high Water warmer; sea-level stands at air slightly warmer. +7-10 m. 

Probably ca Water same; +20m. air unknown. 

Probably ca. Water same; +20m. air unknown. 

Probably much higher Water warmer; than Kotzebuan and air warmer. Einahnuhtan: < +100m; > +20m. Two distinct episodes Water much warmer; during which sea air much warmer. level was higher than at present but probably lower than Anvilian sea level. 

Pzs 

Arch-aeological or radiometric dating 

<5,000 yr at Cape 

Krusenstern; up to 10,000 yr for terraces along Gulf of Alaska coast. <48,000 yr; >25,000 yr. 

Ca. 100,000 yr. 

170,000 yr; 175,000 yr. 

<300,000 yr; >100,000 yr. 

Probably < 1,900,000; 

>700,000. 

Last EtlJisode ca. 2,200,000 yr on St. George Island. 

0 5000 FEET 

0 1000 METRES 

EXPLANATION 

Marine sand 

~I 

~ 

and gravel 

of Second Beach 

(Pelukian) 

Till and 

~ 

~ 

outwash 

Marine sediments of Fourth Beach 

(Einahnuhtan or Kotzebuan) 

B 

Marine sand and gravel of Third 

Beach and Intermediate Beach 

(Anvilian) 

Correlation 

North America Europe 

Late Wisconsin and Recent. 

Middle Wisconsin Interstade. 

Late Wiirm and Recent. 

Middle Wiirm Interstade. 

75 

Sangamon 

Interglaciation. 

Broerup 

Interstade(?) 

and Riss-Wiirm Interglaciationc 

Pre-lllinoian 

Interglaciation. 

Mindel-Riss 

Interglaciation. 

Pre-Mindel 

Interglaciation. 

Middle Pleistocene Inter glaciation. 

Late Pliocene. 

A' 

>- ~ Q)~ § { ~ 1 << I ll:l 

~.~ ITU ~::>Z § ~ Till ) 0' ~ 

:. !".oo cay }f of Submarine ll:l 

Beach (Beringian) ~ 

G 

Schist 

li;l ... 

}

10 

~0 <N 

~0 

Contact; dashed where 

inferred 

FIGURE 38.-Cross section through coastal plain at Nome (from Hopkins, 1967a). Recent work by Hopkins and Nelson at Nome reveals 

that drift of the Nome River Glaciation extends 2,500 m offshore, and 

thick deposits of drift of the Iron Creek Glaciation extend 4,500 m 

offshore. Also, a Pliocene beach was reported at the depth of 50 m 

offshore, as well as Pleistocene beaches lying offshore from 1,000 to 

7,500 mat depths of 12, 22, and 25m (Nelson and Hopkins, 1972, fig. 

5; see also Tagg and Greene, 1970). 

gested that there were two distinct episodes during 

which sea level was higher than now but not as high as 

during the later Anvilian transgression. Later work 

(Hopkins, unpub. data, 1974) indicates the beds of Skull 

Cliff are no older than middle Pleistocene. 

The deposits of Beringian age are considered to be of 
76 QUATERNARY GEOLOGY OF ALASKA 

Pliocene age (D. M. Hopkins, oral commun., Dec. 10, 

1969) (table 1). (See also Tagg and Greene, 1970, figs. 3, 

13.) The Beringian transgression beds on St. George 

Island in the Pribilofs were deposited during the early 

part of the Matuyama reversed geomagnetic polarity 

epoch. The pillow lava overlying the youngest part of 

the Beringian deposits on this island has a potassiumargon date of 2.13±0.06 m.y. (Cox and others, 1966) 

(table 3). 

ANVILIAN TRANSGRESSION 

The type locality of the Anvilian transgression is near 

Nome (fig. 38), and the transgression occurred after the 

first glacial advance recorded in the area (table 2). Deposits of this transgression can be distinguished from 

the preceding Beringian and the following 

Einahnuhtan transgression by their fauna and stratigraphy. The fauna of the Anvilian transgression contains appreciable numbers of extinct species but more 

closely resembles modern faunas than do Beringian 

forms. 

The deposits at N orne consist of a discontinuous sheet 

2-3 m thick of gold-bearing and fossiliferous sandy and 

gravelly beach and littoral sediments that extend inland 5 km from the present coastline. These sediments 

are known locally as Third Beach, Monroeville Beach, 

and Intermediate Beach. In places the deposits lie on 

drift of the Iron Creek Glaciation of early Pleistocene 

age, and in most places they are covered by drift of the 

Nome River Glaciation (table 2). 

According to Hopkins (1967a), sediments of the Anvilian transgression perhaps constitute most of the 

Gubik Formation in that part of the Arctic Coastal 

Plain that lies inland from the highest beaches of the 

Einahnuhtan transgression (the middle Pleistocene 

transgression of McCulloch, 1967). The formation extends 120 km from the sea and is 1-50m thick. Both 

Black (1964) and O'Sullivan (1961) described measured 

sections of the Gubik but have no age control; Hopkins 

(1967a) considered parts of the measured sections to be 

of Anvilian age on the basis of fauna and stratigraphy. 

Other localities with evidence of the Anvilian transgression include Solomon, 55 km east of Nome, the 

Pribilof Islands, and tentatively, some of the Aleutian 

Islands. Sea level probably stood at least 20 m higher 

than at present and may have been as high as 100m 

above present sea level. 

The deposits of the Anvilian transgression at Nome 

were considered for many years to be Pliocene (Dall, 

1920; MacNeil and others, 1943); however, new findings 

show that the Anvilian deposits at Nome were laid 

down after the Iron Creek Glaciation. A recent discovery of well-preserved Anvilian deposits with a rich 

fauna (Hopkins and others, 1974) was made on 

California Creek in western Seward Peninsula. Study 

of this area suggests that two glaciations preceded the 

middle Pleistocene Nome River Glaciation, rather than 

one early Pleistocene glaciation. A shoreline of 90 m on 

St. George Island lies considerably above fossiliferous 

Beringian beds and is cut in reversely magnetized volcanic rocks, which belong to the latter part of the 

Matuyama polarity epoch and which are dated as between 0.7 and 1.9 m.y. old. These lines of evidence suggested to Hopkins (1967a) that the shoreline is of Anvilian age. 

EINAHNUHTAN TRANSGRESSION 

The Einahnuhtan transgression is represented by a 

sequence of fossiliferous beach and littoral sediments 

about 30 m thick at its type locality in the Einahnuhto 

Bluffs on St. Paul Island in the Pribilofs. These deposits 

overlie a basaltic flow that has been dated at 280,000 

and 380,000 years (Cox and others, 1966) and in turn 

are overlain by sediments of Kotzebuan age that are 

capped by a lava flow around 100,000 years old. Sediments ofEinahnuhtan age were reported by McCulloch 

(1967) on the Arctic Coastal Plain. Fourth Beach at 

Nome may be either Einahnuhtan or Kotzebuanin age. 

The name Middletonian transgression was proposed 

by Karlstrom (1965, 1968) for a high sea-level stand 

that he believed took place at about the same time as the 

Einahnuhtan transgression. Hopkins (1967a) did not 

use this term because he believed the results of 

radiometric dating of the Middletonian beds are open to 

question, and the molluscan fauna suggests the beds are 

Anvilian in age. 

The fauna of the Einahnuhtan deposits is essentially 

modern in aspect. The Einahnuhtan transgression represents an interglacial interval of late middle Pleistocene time. 

KOTZEBUAN TRANSGRESSION 

The Kotzebuan transgression took place during the 

interglacial interval that immediately preceded the Illinoian Glaciation (table 3). The type locality is the sea 

cliffs facing Kotzebue Sound on the west shore of Baldwin Peninsula south of Kotzebue (McCulloch and 

others, 1965). The deposits are silty clay and peaty silt 

of deltaic origin. In places they are covered by drift 

comparable in topographic expression to drift of the 

Nome River Glaciation at Nome. Sediments of the 

Kotzebuan transgression are recognized in many other 

places on the shores of Kotzebue Sound. Sediments of 

possible Kotzebuan age are recognized on the Pribilof 

Islands, Cape Prince of Wales, and N ushagak and 

K vichak Bays of southwestern Alaska. McCulloch 

(1967) tentatively assigned some of the marine deposits 

along the northwest coast to this transgression. 
MARINE DEPOSITS 77 

Sea level during the Kotzebuan transgression in Kotzebue Sound was about 21-36 m higher than at present, 

and the sediments generally lie inland from, and higher 

than, the well-preserved wave-cut cliffs and ancient 

beach ridges formed during the following Pelukian 

transgression (Sangamon). 

On western St. Lawrence Island, sediments of Kotzebuan age occur under drift of Illinoian age. A comparison of the mollusk fauna of this age from St. Lawrence 

Island, Chukotka Peninsula, and Kotzebue Sound suggest that during Kotzebuan time cold Arctic water 

pushed so,uthward through the Bering Strait, a flow 

which is reversed from the present northward flow 

through Bering and Anadyr Straits (Hopkins and 

others, 1972). 

PELUKIAN TRANSGRESSION 

The type locality of deposits of the Pelukian transgression is at Nome and consists of a sheet of marine 

sand and gravel3-7 m thick, overlying drift of the Nome 

River Glaciation, and a layer of estuarine sandy silt and 

black organic clay 2-4 m thick on the south side of the 

Snake River valley, also lying on drift of the N orne 

River Glaciation (fig. 38). Pelukian sediments are covered by eolian silt and colluvium of late Wisconsinan 

and Holocene age and were deposited during an eustatic 

rise of sea level that coincided with the Sangamon Interglaciation. The Pelukian transgression is represented by well-preserved marine terraces and fairly 

well preserved marine scarps that lie inland from 

Holocene deposits. 

Deposits of the Pelukian transgression are also present in northern and western Alaska (Sainsbury and 

others, 1965; Sainsbury, 1967a, b) as well as on St. 

Lawrence Island and the Pribilofs. The highest terraces 

along the coast of the Gulf of Alaska between Katalla 

and Icy Point may have been carved by the sea during 

the Pelukian transgression. Two distinct Pelukian sealevel stands probably lay between 7 and 10 m above 

present sea level. 

A fossiliferous interglacial beach deposit at South 

Bight on Amchitka in the Aleutian Islands (pl. 1), 35m 

above sea level, yielded bones of Steller's sea cow 

(Hydrodarnalis) which were dated as 135,000 years 

(Gard and Szabo, 1971; Gard and others, 1972). It is 

thought the deposit in this tectonically active area is 

Sangamon (Pelukian) in age. 

WORONZOFIAN TRANSGRESSION 

The marine Bootlegger Cove Clay in the vicinity of 

Anchorage constitutes type sediments for the 

VI oronzofian transgression as described by Hopkins 

(1967a, b). The clay contains mollusks and Foraminifera (Hansen, 1965, p. A20) as well as ostracodes 

(Schmidt, 1963). It is as much as 16 m thick and 

interfingers laterally with proglacial outwash deltaic 

sediments. Underlying it is drift of the Knik (early 

Wisconsinan) Glaciation (table 2); overlying it are outwash sediments and an end moraine of the Naptowne 

(late Wisconsinan) Glaciation. On the basis of a Th 230 

date of 33,000--48,000 years (Sackett, 1958) on mollusk 

shells from the Bootlegger Cove Clay, Hopkins (1967a) 

assigned an age of 25,000--35,000 years to the 

Woronzofian transgression. He believed that sea level 

then was a few metres lower than at present, as also 

suggested by Curray (1965). 

Because the Bootlegger Cove Clay has evoked widespread interest and controversy both as a stratigraphic 

unit important in establishing a late Pleistocene 

chronology for southern Alaska (p. 24, 73) and as the 

formation responsible for the disastrous landslides that 

occurred in Anchorage during the 1964 earthquake (p. 

73), Ernest Dobrovolny and H. R. Schmoll (oral commun., 1970), in their detailed geologic work in the Anchorage area, attempted to determine the age of the unit 

more precisely. Four radiocarbon age determinations 

on shells indicate that the Bootlegger Cove Clay was 

deposited about 14,000 years ago (Schmoll and others, 

1972). A new uranium-series age of 15,200 ± 2,800 

years on shells supports the radiocarbon age (Schmoll 

and others, 1972, p. 1110); thus the previously reported 

uranium-series dates are apparently incorrect. 

As reported by Schmoll, Szabo, Rubin, and Dobrovolny (1972), the Bootlegger Cove Clay particularly 

the zone with some microfossils, may be interpreted as 

representing a marine transgression during an early 

phase of eustatic rise in sea level that followed the 

maximum extent of glaciation in Wisconsinan time. 

Inasmuch as the Bottlegger Cove Clay was designated as the type deposit for the Woronzofian marine 

transgression, it is clear that this transgression can no 

longer be considered a mid-Wisconsinan interstadial as 

defined by Hopkins (1965, 1967a) or a pre-Wisconsinan 

interglacial event as considered by Karlstrom (1964, 

1968). As Schmoll, Szabo, Rubin, and Dobrovolny 

(1972) suggested, the term Woronzofian should either 

be redefined as an event of late Wisconsinan age (as 

already suggested by Morner, 1971) or be discarded to 

avoid further confusion. In any case, dated deposits 

elsewhere that have been considered part of the 

Woronzofian transgression, such as marine deposits at 

Point Barrow (MacCarthy, 1958; Hopkins, 1967a; 

Brown, 1965a) or the Karginsky deposits of northern 

Siberia (Hopkins, 1965; Karlstrom, 1968; Kind, 1967), 

probably should be reclassified. 

Schmoll, Szabo, Rubin, and Dobrovolny (1972) illustrated that other events in various parts of the world, 

however, can be correlated, on the basis of the new 
78 QUATERNARY GEOLOGY OF ALASKA 

radiometric dates, with the transgression represented 

by the Bootlegger Cove Clay. Among these are (1) a 

short-lived warm phase at 14,100 years B.P. recorded in 

ice cores in Greenland (Dansgaard and others, 1969); (2) 

deposition of marine ttClay III" at Boston (Kaye, 1961) 

from which radiocarbon dating of four shell samples 

yielded an average age of 13,900±300 years B.P. (Kaye 

and Barghoorn, 1964; Krueger and Weeks, 1966, p. 142; 

Stuiver, 1969, p. 566); and (3) a sea level stillstand at 

-38m in the Bering and Chukchi Seas which probably 

is between 13,000 and 14,000 years old (D. M. Hopkins, 

oral commun., April 1972; Creager and McManus, 

1967; Sheth, 1971, p. 13). 

KRUSENSTERNIAN TRANSGRESSION 

Marine deposits of the last 10,000 years or so are from 

the transgression that resulted from the melting of continental glaciers during the late Wisconsinan and 

Holocene time. This was named the Krusensternian 

transgression, from Cape Krusenstern in northwestern 

Alaska. In most parts of Alaska, deposits of the Krusensternian transgression lie within a few metres of present sea level and are less than 6,000 years old; however, 

elevated marine terraces in southern and southeastern 

Alaska that formed 11,000-6,000 years ago are considered to have been carved early in the Krusensternian 

transgression. 

Archeological studies of associated cultural sequences suggest that progradation of the coast began, in 

different places, from 1,000 to 4,500 years ago. The 

marine sediments of the vast Yukon-Kuskokwim Delta 

are in part of Krusensternian age, and many major 

tributaries were diverted during Krusensternian time. 

Hopkins (1967a) believed that sea level lay far below its 

present position until6,000 years ago and within a few 

metres of its present position since· about 5,000 years 

ago. This is supported at Barrow by radiocarbon dating 

of coastal peat (Brown and Sellmann, 1966a) and by 

geothermal studies by Lachenbruch (1957). However, 

Moore (1960) suggested from a study of arctic beach 

ridges that sea level rose about 3m during the last 5,000 

years. 

Regressions of the sea during glacial maximums in 

Pleistocene time exposed many shallow-water offshore 

areas in the world. One of the most interesting and 

well-studied areas is the Bering-Chukchi platform, a 

wide, gently sloping area between the Alaskan and 

Siberian coasts and now covered by 30-150 m of water 

(Scholl and others, 1974). Although this area formed a 

barrier to the migration of marine organisms during 

glacial times, it also provided a land bridge between 

Siberia and Alaska for the migration of vertebrates, 

including man, during these times. This wide, treeless 

land bridge with a severe Arctic climate existed during 

major Pleistocene glaciations (Hopkins, 1959b; 1967a, 

p. 451-484), and the history of the land bridge during 

the past 35,000 years is summarized as follows: (1) 

Bridge present more than 35,000 years ago; (2) bridge 

narrowed and probably severed during middle Wisconsinan time about 35,000-25,000 years ago; (3) land connection restored during late Wisconsinan advances 

from 25,000 to 12,000 years ago, although land connections may have been drowned occasionally for short 

periods during the interval; and (4) land bridge drowned 

by the rising sea between 11,000 and 10,000 years ago. 

SUMMARY 

The first clear stratigraphic picture of Alaskan 

marine deposits of Quaternary age now above sea level 

has appeared over the past decade. Well-preserved 

beaches and shallow-water sediments from late 

Pliocene to Holocene age represent marine transgressions during higher eustatic stands of sea level. The 

transgressions are fairly well dated radiometrically and 

are given provincial names. Because eustatic sea level 

changes can be correlated worldwide, they provide an 

excellent means of tying Alaskan Quaternary events 

_into happenings elsewhere. 

VOLCANIC ASH DEPOSITS 

Volcanic ash deposits are widespread and abundant 

in Quaternary sediments throughout southern Alaska 

from the far west in the Aleutian Islands to southeastern Alaska. Ash deposits are present but less abundant 

in central Alaska, and are unknown in northern 

Alaska. An ash layer constitutes an ideal stratigraphic 

marker and forms the basis of what Wilcox (1965) calls 

volcanic-ash or volcanic-ejecta chronology. Ash deposits 

have been useful in solving stratigraphic problems 

throughout the world; Thorarinsson (1944, 1949) used 

the name ((tephrochronology" for the use of ash deposits 

in stratigraphic correlations in Iceland. 

The ash deposits in Alaska have been noted for years, 

but despite their potential, little use has been made of 

them in Quaternary stratigraphy. A technique recently 

developed for ash identification-accurate, rapid, quantitative chemical analyses of the glass shards of an ash 

by using the electron microprobe (Smith and Westgate, 

1969)-should greatly stimulate use of recognized ash 

horizons in Quaternary work (Smith and others, 1969). 

Potassium-argon methods make it possible to date 

some ash horizons, especially near the source where the 

ash may be thick. A radiometrically dated ash horizon is 

an excellent marker bed when traced from the source 

into sediments of different origins. The distribution of 

an ash bed may also be used to infer wind directions at 

the time of eruption. Such work has already been done 

in Alaska with the Katmai ash (Curtis, 1969, p. 159) 
VOLCANIC ASH DEPOSITS 79 

and the White River Ash (Lerbekmo and others, 1968). 

SOUTHERN ALASKA 

In Southern Alaska, as might be expected of this 

volcanic area, ash beds are numerous. However, since 

much of this area was once covered and scoured by 

glacier ice, almost all the ash layers are postglacial or 

post-Wisconsinan in age. Many layers have proved useful in providing dates in several areas. Ash horizons 

have been used by Black to date Anangula, the oldest 

archeological site in the Aleutians (Black and Laughlin, 1964), estimated to be between 8,000 and 12,000 

years old. 

Heusser (1960, p. 186--188; table 5) used ash layers as 

stratigraphic markers in his pollen work along the 

south and southeast coast of Alaska. An ash layer about 

6, 700 years old is recorded on Kodiak Island and Kenai 

Peninsula; an ash layer about 1,200 years old is noted in 

the Prince William Sound and Icy Cape section. 

An ash bed in southeastern Alaska has been dated as 

about 2,300 years old. This may be the same as the ash 

layer from Mount Edgecumbe described by Reed and 

Coats (1942, p. 48-57). McKenzie (1970a) suggested an 

age of 11,000 years for an ash layer at Glacier Bay 

thought to be derived from Mount Edgecumbe. 

At least four pre-Katmai ash marker beds occur in 

peat sections at Brooks Lake just northwest of Mount 

Katmai. The pre-Katmai ash beds are younger than 

6,000 years (Heusser, 1963a; Nowak, 1969; L. S. Cressman and D. E. Dumond, unpub. data, 1962). 

Miller and Dobrovolny (1959, p. 78) mentioned ash 

layers 1-10 mm thick in bogs near Anchorage. No mention of age is made except that they are perhaps postWisconsinan. Dachnowski-Stokes (1941) also mentioned ash horizons in bogs near Anchorage, as well as 

elsewhere in Alaska. 

The most outstanding ash fall in Alaska during historic time is from the 1912 eruption of Mount Katmai 

and Novarupta in the Aleutian Range (pl. 1). Griggs 

(1922, p. 29) estimated that 20 x 109 m3 of ash was 

ejected over an area of at least 280,000 km2 . Ash deposits as much as 15m thick exist in the mountains, and 

an ash layer 6 mm thick was deposited at a distance of at 

least 660 km from the mountains. 

The tephra described by Griggs (1922) and by Fenner 

(1920) was restudied in considerable detail by Curtis 

(1969). This new work shows that nine layers of tephra, 

each with distinguishing characteristics, can be recognized and that practically all the ejecta came from 

Novarupta instead of Mount Katmai. This so-called 

Katmai ash is now a valuable stratigraphic marker and 

has been recognized by Heusser (1960, table 5) on 

Kodiak Island and on Kenai Peninsula. 

The glaciers adjacent to Mount Katmai were buried 

under many feet of ash, and the ablation of the ice has 

been severely hindered since 1912. Except for reconnaissance observations of changes in glacier regimen by 

Muller and Coulter (1957), the opportunity to study 

glacier regimen and ablation changes caused by a thick 

ash deposit of known age has been little used. 

One significant application of volcanic ash beds is 

that of marker beds in firn fields of glaciers in Alaska. It 

is suggested that the 1912 Katmai ash bed can be 

identified in the firn of the Greenland icecap (C. C. 

Langway, Jr., oral commun., 1964). 

The application of the new techniques, which permit 

precise dating and chemical identification of source, 

may make the isolated small occurences of ash more 

useful in deciphering Quaternary history in Alaska. 

There is great potential for the use of recognizable ash 

horizons in archeology, paleopedology, and palynology. 

This is especially true in southern Alaska, where volcanic ash is still being deposited. On July 9, 1953, a 

6-mm layer of volcanic ash from Mount Spurr was 

deposited on the city of Anchorage (Juhle and Coulter, 

1955; Wilcox, 1959, fig. 63). The ash fall partly blocked 

the sunlight. 

SEWARD PENINSULA 

An area of about 1,000 km in northern Seward Peninsula near Cape Espenberg is overlain by volcanic ash. 

The ash is derived from several large maars the 

youngest of which, Devil Mountain, erupted in late 

Wisconsinan time, near the end of the last episode of 

loess deposition in the area (D. M. Hopkins, unpub. 

data, 1968). 

CENTRAL ALASKA 

The oldest volcanic ash layers in central Alaska are 

known from gold mining exposures in the central part of 

the Yukon-Tanana Upland, especially over a large area 

in the vicinity of Fairbanks (Pewe, 1952a). Except for 

the White River Ash of Lerbekmo, Hanson, and Campbell (1968) in east-central Alaska, no source area has 

yet been identified. Ash horizons 1 from Illinoian to 

Holocene, have been used in stratigraphic work near 

Fairbanks. The oldest and thickest deposit is the Ester 

Ash Bed (fig. 39; table 3) (Pewe, 1955, p. 713; 1965a, fig. 

1-8), a 15-cm-thick white vitric ash bed of at least early 

Illinoian age; it lies near the base of the oldest known 

loess deposit. A white vitric ash bed (Pewe, 1952a, p. 

86), 1-2 em thick, thought to be late Illinoian in age, is 

exposed in many placer cuts (fig. 29). In all exposures 

the ash has been contorted by solifluction movement 

and block slumping (Pewe, 1975). A 1-cm-thick white 

ash layer is known from Wilber Creek (Pewe, 1952a, p. 

156), where it is thought to be less than 4,200 years old. 

A 1-cm-thick white ash layer, dated as 14,000 years old 

by bracketing radiocarbon dates, is exposed along the 

Chatanika River, 40 km north of Fairbanks, and has 
80 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 39.-Ester Ash Bed of Illinoian age in Fairbanks Loess, exposed near base of mining cut between Ester and Cripple Creeks 16 km 

east of Fairbanks, Alaska. Photograph No. 354 by T. L. Pewe, August 23, 1948. 

been named the Chatanika Ash bed (Pewe, 1975). The 

ash layer is characteristically distorted by ice wedge 

growth (Pewe, 1965a, fig. 1-15). The stratigraphic position of the ash layers seems fairly well authenticated 

(Pewe, 1975); electron microprobe analysis is now underway to refine these interpretations and correlate 

these ash layers with other exposures. 

A distinctive 6-mm-thick white ash bed, widespread 

in the lower Delta River area, is well exposed along the 

Delta River and Jarvis Creek and has been termed the 

Jarvis Ash Bed (Pewe, 1965c, p. 63--66). The ash layer is 

exposed in many loess sections and is dated as 2,000-

4,000 years old (Pewe and Holmes, 1964; Reger and 

others, 1964). 

The most remarkable ash fall recorded in Alaska is a 

light-colored pumiceous ash described by Capps (1916a) 

in the upper White and Yukon River valleys and named 

the White River Ash by Lerbekmo, Hanson, and Campbell (1968). It was termed an andesitic pumiceous ash by 

Knopf (Moffit and Knopf, 1910, p. 43--44) and a 

rhyodacitic or dacitic ash by Berger (1960). The possible 

source of the ash was Mount Natazhat, at the east end of 

the Wrangell Mountains approximately 7 km west of 

the Alaska-Canada border (Lerbekmo and others, 1968, 

p. 284). Capps (1916a) estimated that about 40 x 107 m3 

of ash was deposited over an area of more than 360,000 

kr 2 • Ash beds as much as 90 m thick are noted near the 

source. The ash thins to less than 0.5 min 30 km and 

then spreads a thin blanket 1-25 mm thick for 500-700 

km north and east in a bilobate pattern (Lerbekmo and 

others, 1968; Lerbekmo and Campbell, 1969). The thin 

seam of white ash is widespread in east-central Alaska 

and western Yukon Terri tory and has been reported 

since 1885 (Schwatka, 1885; Dawson, 1889; Hayes, 

1892; Johnson, 1946; Bostock, 1952; Hansen, 1953; 

Hanson, 1965). The ash lies generally just beneath the 
FLORA 81 

vegetation mat, except where peat or loess accumulation has been rapid. 

Capps (1916a) estimated the age of the ash fall to be 

1,400 years by counting growth rings of spruce trees 

that produce successively higher lateral roots as peat 

accumulated over the ash with consequent rise of the 

permafrost table. The accuracy of this ingenious dating 

method has been borne out inasmuch as Fernald's 

(1962) radiocarbon data indicate that the ash layer is 

about 2,000 years old, and Stuiver, Borns, and Denton 

(1964) radiometrically dated the ash fall at 1,425 years 

in adjacent Canada. Recent work (Lerbekmo and 

others, 1973) suggest the ash fall may be more complex 

than previously realized. There may be three layers 

closely spaced in time, with the youngest about 1,000 

years old. 

The White River Ash has proved useful in archeological studies, studies of Holocene glacial advances (Borns 

and Goldthwaite, 1966, p. 615), and investigations on 

the deposition rate of loess and peat. 

Heusser (1960, table 5, p. 188) believed that a thin ash 

horizon in peat bogs from Kodiak Island to Icy Cape 

near Mount Saint Elias is correlative with the ash bed 

described by Capps (table 3). He placed the age of the 

ash, in absence of radiocarbon dates, at about 2,500 

years. The work of Lerbekmo, Hanson, and Campbell 

(1968), however, showed that the White River Ash did 

not drift along the southern coast. The ash described by 

Heusser, therefore, has a different source, and its age 

estimate is less tenable. 

In addition to these stratigraphically controlled ash 

horizons in central Alaska, there are many other ash 

beds, some of them mentioned in the literature. Fernald 

(1960, p. 251) and Capps (1935, p. 87) reported a thin ash 

layer near the surface in the upper Kuskokwim region. 

Florence Weber (oral commun., 1961) noted a lenticular 

pocket of white volcanic ash 30 em thick in Quaternary 

sediments along the lower Koyukuk River. 

FLORA 

The present-day vegetation of Alaska consists of 

three major types: the coastal Sitka spruce-hemlock 

forests of southeastern and south-central Alaska, the 

interior white spruce-birch forest of central Alaska, 

and the treeless tundra of western and northern Alaska 

(Sigafoos, 1958) (fig. 40). 

The coastal forests extend a few tens of kilometres 

inland along the coast of southeastern and southern 

Alaska westward to Cook Inlet and northeastern 

Kodiak Island. In addition to the Sitka spruce (Picea 

sitchensis) and western hemlock (Tsuga heterophylla), 

the coastal forest includes mountain hemlock (Tsuga 

mertensiana), Alaska cedar (Chamaecyparis nootkatensis), lodgepole pine (Pinus contorta), and Douglas fir (Pseudotsuga menziesii), and smaller areas 

of Alpine fir (Abies lasiocarpa, Pacific silver fir (Abies 

amabilis), , and western redcedar (T huya plicata) 

(Sigafoos, 1958; Heusser, 1960). 

The interior forest is distributed today through most 

of central Alaska north of the coastal mountains and 

south of the Brooks Range. In addition to the white 

spruce (Picea glauca) and birch (Betula papyrifera), the 

common species are black spruce (Picea mariana), balsam poplar (Populus balsamifera), aspen (Populus 

tremuloides), larch (Larix larician), and willow (Salix 

sp.) (Sigafoos, 1958; Hilten, 1941-48). Various species of 

alder (Alnus) grow in both forest and tundra regions. 

The tundra is found beyond the limits of forest in 

central and western Alaska and elsewhere in highland 

areas above tree line. Tundra covers approximately 25 

percent of Alaska and is a mosaic of many different 

types of vegetation, some of which are limited to either 

southern or northern tundra regions (Griggs, 1936; 

Spetzman, 1959; Britton, 1958b; Wiggins, 1962). 

The distribution of vegetation in Alaska falls into two 

large phytogeographic areas: the glaciated and the unglaciated regions (fig. 6). The glaciated areas have a 

floral history of repopulation of the land by either 

tundra or forest during the last 1,000 to tens of 

thousands of years. The unglaciated part of Alaska constitutes 50 percent of the State and represented refugia 

for plant and animal life during glacial maximums 

(Hulten, 1937; Heusser, 1960). In the unglaciated areas, 

especially of central and western Alaska, the vegetation 

history records the shifting of tree line and the change 

from one type of tundra vegetation to another. 

In general, the changes in vegetation from glacial to 

interglacial times in Alaska are small compared with 

the great changes in temperate latitudes (Sears, 1935, 

1938). Yet, recognizable changes in the vegetation did 

occur in Alaska throughout Quaternary time. 

The record of Quaternary vegetation is based largely 

on palynology. In the Arctic, however, palynology is a 

blunt instrument because the tundra pollen diagram is 

much simpler and less informative than forest records 

of temperate regions (Colinvaux, 1967a). Information 

concerning vegetation of Wisconsinan age or earlier is 

limited mainly to deposits of the Yukon-Tanana Upland 

and to terrestrial and marine sediments of western and 

northern Alaska. Studies of post-Wisconsinan vegetation are available for some parts of Alaska, particularly 

of the southern and southeastern coastal areas. 

EARLY TO MIDDLE PLEISTOCENE 

The floral record in Alaska earlier than about Yarmouth(?) time is scanty and limited to western Alaska, 

particularly Seward Peninsula. Because the classical 

midwestern glacial terminology of North America has 

not been dated, the early Quaternary deposits in Alaska 

cannot be directly related to it. However, the deposits 
82 QUATERNARY GEOLOGY OF ALASKA 

18cf 11cf 160° 150° 140" 130° 120° 

1 c OcEA 

c N 'f D 

540 

BERING 

S E A 

P Pribilof 

Islands ~ 

,. 1l 

Cape 

Thompson 

.umiat 

B R 0 0 K s R 

~0 

Unforested areas 

Interior white spurce-birch forest 

Coastal sitka 

-

spruce-hemlock forest 

100 0 100 200 300 MILES 

100 0 100 200 300 KILOMETRES 

0 C E AN 

17o" 

FIGURE 40.-Generalized map of major forest types and unforested areas in Alaska. After Sigafoos (1958) and Hopkins (1959a). 

can be related to named Alaskan marine transgressions 

or glaciations. 

The earliest record of flora in Alaska important to the 

Quaternary history is the pollen and wood preserved in 

deposits of the Beringian transgression (late Pliocene) 

in western and northern Alaska and the Aleutian Islands (Hopkins, 1967a). Picea and Pinus were reported 

on the Arctic coast, near N orne, and on Tanaga Island in 

the Aleutians; Larix also occurs in the coastal and Nome 

areas (Hopkins, 1965). Abies, Tsuga, and Carya that 

were reported in Beringian deposits at Nome (Hopkins, 

1965) probably represent pollen reworked from older 

beds (Wolfe and Leopold, 1967, p. 197-198; Hopkins, 

1967a, p. 61) a few miles off the present coast (Nelson 

and Hopkins, 1972). It is noteworthy that in Beringian 

time Pice a and Larix were several hundred kilometres 

beyond their present limits, and Pinus was many hundreds of kilometres beyond its present limit. 

The lowest part of a lacustrine deposit in the Yukon 

Flats contains a pollen flora of pine, spruce, alder, birch, 

hemlock, fir, and hickory (Williams, 1962, p. 304) and 

may be late Pliocene or early Pleistocene in age. 

The record of pre-Yarmouth(?) Quaternary flora is 

limited to the detailed study made by Guthrie and 

Matthews (1971) on a complex sequence of vegetationrich silts at Cape Deceit near Deering on the south shore 

of Kotzebue Sound. The sediments are rich in fossil 

vertebrates and flora, peat, pollen, and tree macrofossils. The vertebrate study was reported (Guthrie and 

Matthews, 1971) along with comments about the vegetation; work on description and interpretation of the 

flora is not yet finished. This study reported the most 

complete sequence of Quaternary sediments in Alaska, 

from perhaps earliest Pleistocene to and including the 

Holocene. The section is divided into three formations: 

the Cape Deceit Formation, early Pleistocene to and 
FLORA 83 

including Iron Creek Glaciation [Gunz I(?)-Gunz I!Gunz 

II(?)-Gunz II(?)]; Imnachuk Formation [Mindle/Gunz 

II(?)-Mindel(?)-Einahnuhtan or Anvilian transgression]; and Deering Formation [from Mindel/Riss(?) 

(Kotzebuan transgression) to present]. 

Guthrie and Matthews (1971) believed that on the 

north side of eastern Seward Peninsula during a very 

early interglacial(?) period thought to be Waal(?) (Gunz 

I/Gunz II) a forest tundra existed and conifer tree line 

advanced as far as Cape Deceit. Larix was sparsely 

distributed in the region. This environment was followed by a period with a more severe tundra environment than now and with the formation of nonwoody 

peat. This is thought to correlate with the time of the 

Iron Creek Glaciation (tables 2, 3). 

No vegetation record is present for the next interglaciation, which may be either the Einahnuhtan or 

Anvilian, but a peat deposit representing a tundra environment is thought to be equivalent to a glaciation 

(Mindel?). 

YARMOUTH(?) 

Three types of evidence, each from different areas, are 

available to indicate an interglaciation prior to the Illinoian Glaciation, the time of the Kotzebuan transgression (Yarmouth?): marine and nonmarine beds 

from Kotzebue Sound, pollen from lake deposits in central Seward Peninsula, and wood at the base of loess 

near Fairbanks. 

Hopkins (1967a) stated that plant remains are abundant in beds of the Kotzebuan transgression in the Kotzebue Sounsl area but as yet have received little study. 

Wood of Pinus and Populus is known, and Pinus pollen 

in silt is recorded. The presence of pine should be investigated further because studies at nearby Cape Deceit 

and Imuruk Lake reveal spruce but no pine at that time. 

Pine does not extend to central and western Alaska 

today. Guthrie and Matthews (1971) indicated that at 

Cape Deceit during the time of the Kotzebuan transgression(?) (Yarmouth?) the area was forested and 

spruce tree line advanced to at least that position (fig. 

40). 

Colinvaux (1962, 1963) studied the pollen of an 

8-m-long core from sediments of the bottom of Imuruk 

Lake in central Seward Peninsula (fig. 40). He found a 

record of changing tundra types consisting of three 

periods when vegetation was similar to now, alternating with periods when vegetation was different (colder). 

Because of an anomaly in the radiocarbon dating, the 

record can be interpreted as representing either the last 

22,000 years or the span of time from a pre-Illinoian 

interglaciation (Yarmouth?) until the present. Colinvaux favored the latter interpretation, and he (1967a) 

did not list the ccanomalous" radiocarbon dates, although he stated that there was no radiocarbon support 

for the lower part of the core. Black (1966) stated that 

the use of the lower part of the core might be meaningless. 

This controversy over the interpretation of the lower 

part of the core may now be solved by Colinvaux (oral 

commun., Oct. 24, 1969) and Colbaugh (1968). A core 

from a lake on St. Paul Island in the Pribilofs revealed 

the same type of anomalously young dates below older 

dates (Colinvaux, 1967c) as does the Imuruk Lake core. 

The young dates are not from organic mud but from 

sandy layers that permitted ground water to flow down 

the side of the basin under the mud plug and to enrich 

the sand with modern carbon and so produce the 

anomalously young radiocarbon ages. This idea of 

ground-water flow was confirmed with tritium tracers. 

The anomalously young dates in the first Imuruk 

Lake core are also from sandy sediment permitting 

ground-water flow. Since publication of the original 

data (Colinvaux, 1964a), other cores collected from Imuruk Lake by Colinvaux have been analyzed. Core II 

and core IV were analyzed by Colbaugh (1968, figs. 5, 6), 

including radiocarbon dating, and her work completely 

supports Colinvaux's interpretation. 

Accepting Colinvaux's later interpretation, the pollen record from Imuruk Lake indicates that during a 

pre-Illinoian interglacial time (Yarmouth?), the vegetation of the area was similar to now, with much tundra 

flora of cotton grass (Eriophorum), dwarf birch (Betula 

nana), and alder (Alnus) present. The spruce tree line 

was not far distant. 

In central Alaska at the junction of Engineer Creek 

and Dawson Cut, as well as at Eva Creek (fig. 29), Sheep 

Creek, and Ready Bullion Bench, there is exposed in 

mining cuts at the base of the Illinoian loess a bed of 

large white spruce stumps (22 em in diameter) in 

growth position (fig. 41) and prostrate spruce logs 3m 

long and 30 em in diameter (Pewe, 1952a). These plant 

remains appear older and more weathered than wood in 

the overlying Illinoian and Wisconsinan frozen loess. 

This wood is smashed, flattened, and iron stained. These 

stumps date from a time of a well-developed forest, a 

time that may be part of the interglaciationjust prior to 

the deposition of the Illinoian loess. This forest bed has 

been termed the Dawson Cut Formation (Pewe, 1975). 

The wood at the base of the loess and on the underlying 

tightly cemented iron-stained gravel at Sheep Creek 

was identified as spruce and that from Ready Bullion 

Bench as alder (R. C. Koeppen, written commun., Sept. 

28, 1967). 

ILLINOIAN 

The record of flora in Alaska is still scant in deposits 

of Illinoian age. Information is restricted to data from 

Seward Peninsula and Fairbanks. The record of the 

flora for the Illinoian interval of the Imuruk Lake core 

(Colinvaux, 1967a) shows that there was an Arctic 

grass tundra with little or no alder. Dwarf birch was 
84 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 41.-White spruce stumps rooted in soil and gravel at base of loess of Illinoian age, Eva Creek, 16 km west of Fairbanks, Alaska. 

Large stump was submitted to three different laboratories for radiocarbon dating and was beyond the range of dating-University of 

Michigan, 18,000 years; University of Chicago, > 20,000 years; Lamont Geological Observatory (1-137X), > 28,000 years. Photograph 

No. 471 by T. L. Pewe, September 18, 1949. (See fig. 29.) 

present but less common than during interglacial 

times. Sage (Artemisia) was more common than now or 

in an interglacial period. The tree line was not close. At 

Cape Deceit (Guthrie and Matthews, 1971) during Il-· 

linoian time, a tundra environment was present. 

Pollen analysis of peat collected by the writer in Illinoian loess in valley bottoms of the Fairbanks area 

indicates that the tree pollen content was conspicuously 

and significantly lower than today, indicating a relatively sparse tree cover. No pollen of the Gramineae was 

present (E. S. Barghoorn, written commun., May 1, 

1957). A lowering of tree line to the level of the creek 

valley bottoms requires a drop of 45{}-600 m, which 

suggests that the climate was colder than now. A much 

more restricted forest area is also borne out b¥ the 

greater number of grazers (mammoth, bison, horse) 

than present (Pewe, 1952a; Pewe and Hopkins, 1967). 

In the Fairbanks area today, the boreal forest is well 

developed, and tree line is approximately 60{}-700 m 

above sea level. Above this elevation, the rounded hills 

are clothed in a tundra rich in dwarf birch and alder as 

well as willow. Two contemporary peat samples collected from creek valley bottoms by the writer contain 

tree pollen percentages of 53 and 33 percent. The tree 

pollen percentage is entirely spruce except for three or 

four erratic pine pollen grains. The nonarboreal pollen 

in the samples is 35 percent shrubs and 10 percent 

herbs. Pollen of the Gramineae is less than 1 percent (E. 

S. Barghoorn, written commun. , May 1, 1957). 

SANGAMON 

The only records of known Sangamon vegetation reported from Alaska come from three localities on Seward Peninsula, one from the Baldwin Peninsula, two 
FLORA 85 

from St. Lawrence Island, and several in the Fairbanks 

area. Hopkins, MacNeil, and Leopold (1960, p.53) 

showed from pollen3 and from spruce logs found in estuarine sediments near Nome that tundra vegetation 

prevailed and that the forest was near at the time of the 

Sangamon maximum. In late Sangamon time, the tree 

line reached the Snake River valley (pl. 1). Spruce trees 

were 5{}..-80 km west of their present limit in the Kotzebue Sound and Nome areas (Hopkins, 1965). Locally, 

there was tundra with dwarf birch, and alder bushes 

were nearby. The pollen spectra suggest (Colinvaux, 

1967a, p. 217) that during at least part of Sangamon 

time, the vegetation near and at Nome was comparable 

to that of the present. 

Colinvaux (1962) studied pollen from the Imuruk 

Lake core in central Seward Peninsula and reported 

that the vegetation was a sage-alder tundra similar to 

the present conditions and that tree line was near. 

At Cape Deceit (Guthrie and Matthews, 1971) a 

tundra environment existed with the formation of nonwoody peat. From two adjacent localities on St. Lawrence Island in the Bering Sea (pl. 1), Colinvaux (1967b) 

cautiously suggested that pollen analyses show that the 

local tundra, at a time thought to be Sangamon, was 

comparable to the modern tundra. All evidence so far 

indicates that the Alaskan side of the Bering Sea had a 

vegetation comparable to that of the present. 

McCulloch, Taylor, and Rubin (1965) reported that in 

the Kotzebue area in Sangamon time, the forest had 

advanced westward into areas that are now treeless 

tundra. Stumps more than 42,000 years old rest on 

Illinoian till in this area of the Baldwin Peninsula. 

In all the mining-cut exposures in the Fairbanks 

area, the contact between the retransported silt of Wisconsinan age and the under lying loess of Illinoian age 

(fig. 19) is repr~sented by a poorly formed to well-formed 

topographic bench. In sections in Eva Creek (fig. 29), 

Dawson Cut, Gold Hill and elsewhere, the bench is 

conspicuous because of a forest layer of rooted stumps 

and prostrate logs of birch and spruce as much as 25 em 

in diameter (Pewe, 1952a). It is very likely that in most 

localities this concentration of tree remains represents 

forest of Sangamon time. These concentrations occur at 

the correct stratigraphic horizon and may represent the 

return of the forest to the area. Samples collected by the 

writer from the lower part of the Wisconsinan deposits 

in the area have all been older than 35,000 years. A 

sample from the possible Sangamon forest bed on Eva 

Creek was dated as more than 56,900 years (Matthews, 

1968b, p. 207, 1970). The forest bed is now termed the 

Eva Formation (Pewe, 1975). The forest environment 

was probably similar to that now. 

3Samples are from a basal peat on the Second Beach CPelukian transgression) (table 7) at 

Nome. Analyzed by E. B. Leopold. 

WISCONSINAN 

Information needed to reconstruct the vegetation pattern in Alaska during Wisconsinan time comes from 

two broad areas: the tundra zone adjacent to the Bering 

Sea, including Point Barrow, and the forested interior 

near Fairbanks. 

From the far west, most of the information is from 

pollen analysis, and only one record covers the entire 

Wisconsinan time, the other being mainly the end of 

Wisconsinan time. In central Seward Peninsula, 

Colinvaux's (1962) pollen analysis indicated that from 

early Wisconsinan time until the end of Wisconsinan 

time, an Arctic herbaceous tundra was present, Arctic 

sage was relatively common, but dwarf birch was absent or scarce. Tree line was not near. At Nome, 

analysis of pollen by Leopold (Hopkins and others, 

1960) indicated that at least near the end of Wisconsinan time (13,600 years ago), a grass-sage tundra existed. Tundra also existed at Cape Deceit (Guthrie and 

Matthews, 1971). 

Cores from Kotzebue Sound and Ogotoruk Creek to 

the north contain pollen representing a time near the 

end of the Wisconsinan. Heusser (1963b) concluded that 

the bottom of the core from Ogotoruk Creek represents 

the late glacial period and a tundra with little birch. 

The core from Kotzebue Sound indicates that 12,000 

years ago a tundra with dwarf birch was already present ·(Colinvaux, 1967a, p. 221). 

To the far north at Point Barrow, a peat sample dated 

at 25,000 years old (Brown, 1965a) lacks alder and 

birch, and Colinvaux (1967a) believed an herbaceous 

tundra prevailed in the Arctic Coastal Plain at least in 

that part of the Wisconsinan glacial episode. Pollen 

from St. Lawrence Island suggested that in Wisconsinan time a cold Arctic tundra existed in which grasses 

and sages predominated (Colinvaux, 1967b). A peat 

sample from near Goodnews Bay collected by Hopkins 

from a drained kettle lake in an end moraine of late 

Wisconsinan age was analyzed for pollen by E. B. 

Leopold. The oldest sample is 11,500 years old and contains pollen of an herbaceous tundra. Colinvaux (1967a) 

stated that even at the south margin of the Bering land 

bridge, the Wisconsinan tundra vegetation was comparable to that in the Bering Strait area in late Wisconsinan time. 

In central Alaska the greatest source of information 

concerning the flora of Wisconsinan time is from the 

exposures made by large-scale placer gold mining in the 

perennially frozen, retransported, organic-rich silt (fig. 

20), termed the Goldstream Formation (Pewe, 1975). 

The silt contains abundant layers, lenses, and isolated 

pods of plant remains. Peat beds as much as 2 m thick 

are present, and frozen nests and seed caches of rodents 

occur (Wilkerson, 1932, p. 15; Chaney and Mason, 1936, 

p. 14; Mertie, 1937, p. 193; Pewe, 1952a, p. 177; 1966c, 
86 QUATERNARY GEOLOGY OF ALASKA 

fig. 3). Some forest beds are present as well as beaver 

dams; wood from one dam was dated at 13,600 years 

B.P. (Pewe, 1975). Wood remains include alder (Alnus), 

spruce (Picea), willow (Salix), cottonwood (Populus), 

and birch (Betula). The logs and limbs throughout the 

formation are fresh, and some have pieces ofbark. Wood 

is not nearly so abundant, however, as in the overlying 

post-Wisconsinan silt deposits. In general, more 

megafossils occur in central Alaska than in the coastal 

tundra areas because of the existence of small patches of 

forests in valley bottoms in the interior. 

Peat samples collected by the author from different 

stratigraphic horizons in the Wisconsinan retransported silt (Goldstream Formation) (fig. 20) in the Fairbanks area were studied by E. S. Barghoorn. He reported that the samples from Fairbanks Creek are 

statistically and significantly low in tree pollen, indicating a very sparsely forested or almost treeless area. 

The samples from this creek valley indicate that the 

tundra was rich in alder and dwarf birch with little 

grass. Pollen from a thick peat bed near the base of the 

Wisconsinan retransported silt in Ester Creek indicates 

that coniferous trees were absent (E. S. Barghoorn, 

written commun., Nov. 23, 1954). The vegetation of the 

valley bottoms at the time was a grass-sedgemoss-Equisetum cover associated with small stands of 

dwarf birch and willow. Such evidence indicates a lowering of tree line by 600 m in Wisconsinan time. The 

most thorough study of pollen from the frozen silts of 

Eva Creek is by Matthews (1970), who reported conclusive evidence that spruce woodlands were almost totally eliminated from interior Alaska in Wisconsinan 

time. 

Among the vertebrate fossils of the retransported silt 

are Citellus undulatus, Lemmus siberius, Dicrostonyx 

torquatus, and mountain sheep (Ovis nivicola). These 

mammals do not live in the Fairbanks area today but 

live near or above tree line or on the tundra. Such 

mammal distribution also suggests that tree line was 

500-600 m lower in the Fairbanks area during Wisconsinan time. The restricted forest area is also shown by 

the high percentage of grazers at this time (Pewe, 

1952a; Guthrie, 1968a). 

Repenning, Hopkins, and Rubin (1964) clearly demonstrated lowering of tree line by 500 m in the Tofty 

area, 130 km to the west ofFairbanks, by the presence of 

tree-line fauna living in valley bottoms in late Wisconsinan time. 

All specimens studied by E. S. Barghoorn or by Rolland Brown of the U.S. Geological Survey or megafossils 

observed by the writer and those reported by Chaney 

and Mason (1936) and Chaney (1938, p. 390-391) are of 

the spec::ies living in the Fairbanks area today. Although the flora of the Wisconsinan time in central 

Alaska contains the same species as today, forest cover 

was greatly restricted, perhaps limited to major valley 

bottoms. 

Hopkins (1970; 1972) put forth the idea that a treeless 

vegetation prevailed in central Alaska during ttfull glacial" time and that the spruce persisted in a refugium 

somewhere in southwestern Alaska until 6,000-8,000 

years ago. The writer believes that such a source is not 

necessary, at least for central Alaska, because scattered 

spruce probably persisted in isolated creek bottoms in 

central Alaska, inasmuch as spruce wood occurs in the 

frozen retransported silt of Wisconsinan age in the 

Fairbanks area (fig. 20). Spruce wood in beaver dams, 

isolated sticks, and rooted stumps have been dated as 

13,600, 10,500, 9,685, 8,930, 8,500, and 7,500 years old 

(Pewe, 1975). Dates of 20,000-30,000 years are also 

known on small sticks, but the species of wood is not 

known. 

POST-WISCONSINAN 

The post-Wisconsinan vegetation record is, as might 

be expected, the most clearly and thoroughly 

documented part of the floral history. Evidence of the 

postglacial thermal maximum or hypsithermal interval 

is recognized from pollen spectra in northern and northwestern Alaska (north of the Brook8 Range). However, 

from central and western Alaska the record is mainly 

that of forest return or expansion about 10,000 years 

ago. 

The first pollen record of postglacial time in northern 

and western Alaska was that by Livingstone (1955) 

from a 5-m-long core taken from Chandler Lake (pl. 1) 

in the Brooks Range (fig. 40). He set up a threefold 

chronology that has been used as a general guide 

throughout northern and northwestern Alaska. The 

chronology, which is supported by pollen analyses of the 

radiocarbon-dated core of valley fill from the unglaciated part of the North Slope near Umiat (Livingstone, 1957) (table 3), shows that an herbaceous tundra 

was present 8,300 years ago but at 7,500 years ago 

yielded to a tundra in which dwarf birch was very abundant. About 5,800 years ago, alder became very common, and Livingstone stated the alder maximum is 

climatically equivalent to and contemporaneous with 

the thermal maximum. Today, the tundra in the Umiat 

region is characterized by alder and willow (Churchill, 

1955). 

Good support for the advance of alder north of the 

Brooks Range is from megafossils of alder found by 

Tedrow and Walton (1964) in the upper Killik valley 

(pl.1). Alder leaves 5,650 years old preserved in the 

frozen ground 13m beneath the surface led Tedrow and 

Walton to believe the climate of the area was warmer 

5,000 years ago than now, inasmuch as alder does not 

grow there today. 

Work by Colinvaux (1964b, 1965, 1967a, p. 212-213) 

on samples collected by Brown (1965a, 1969b) at Point 
FLORA 87 

Barrow revealed that from 8,000 to 9,500 years ago a 

grass-sage tundra was predominant. A stratigraphic 

hiatus covers 4,000 years, and the last 5,000 years records a higher alder content and vegetation similar to 

that now. Colinvaux (1967a, p. 213) stated that no broad 

change in the vegetation record is detectable in the 

pollen record of the last 5,000 years. However, because 

of the 4,000-year gap, it cannot be demonstrated 

whether an alder maximum, indicating the thermal 

maximum like that recorded at Umiat, was present in 

the Barrow area. 

A pollen analysis by Heusser (1963b) from peat deposits at Ogotoruk Creek about 500 km west of Chandler Lake records a change from an herbaceous tundra 

in early postglacial time to a tundra in which birch was 

common. Heusser showed that the record is similar to 

the early part of the Livingstone chronology determined 

in the Brooks Range farther east. Schweger (1971) carefully examined a detailed stratigraphic section on the 

Kobuk River near Onion Portage representing the last 

12,000 years and reported no record of a thermal maximum, but rather a gradual change from tundra vegetation to spruce cover. 

For an area near Nome, E. B. Leopold (in Hopkins and 

others, 1960) analyzed pollen that indicates that a 

threefold spectrum similar to that of Livingstone is 

present but that the sequence started earlier. Herbaceous tundra (zone I) was dated as 13,000 years B.P. and 

zone II (birch tundra) as 10,000 years B.P. Zone III is the 

alder tundra that began 3,500 years ago. Colinvaux 

(1967a) recognized these three zones from Imuruk Lake 

but indicated that they span a much. longer period of 

time, with only the sage alder tundra being postglacial. 

In the late forties, Hopkins determined from logs and 

stumps exposed in mining excavations that about 

8,000--10,000 years ago the spruce forest advanced 

westward from its present limits on the Seward Peninsula (Hopkins an Giddings, 1953). This evidence, plus 

additional findings of alder, birch, and poplar logs 

(8,500--9,500 yr) on Seward Peninsula and Baldwin 

Peninsula (McCulloch, 1967), indicates that the forest 

spread westward in response to the warming that ended 

the Wisconsinan Glaciation. Colinvaux (1967a) commented that this temporary westward extension of tree 

line has not yet been noticed in pollen diagrams, 

perhaps because pollen work in the tundra or near 

tundra areas is not a delicate enough measurement. 

To the south, on St. Paul Island of the Pribilofislands, 

Colinvaux (1967c) noted that the pollen record shows 

that vegetation similar to the present has existed for the 

last 9,000 years. From Goodnews Bay, pollen analyses 

reveal that in the last 10,500 years a threefold spectrum of herbaceous, birch, and alder tundras parallel to 

the three-zone sequence at Chandler Lake existed. 

The record of post-Wisconsinan vegetation distribution on the east side of the Bering land bridge from Point 

Barrow to Goodnews Bay was summarized by Colinvaux (1967a). Heusser (1960) showed by detailed pollen 

analyses and radiocarbon dating that from 10,000 to 

about 8,000 years ago tundra was present on the south 

coast and that pine forests were present in the southeast 

(table 3). From about 8,000 to 3,500 years ago, Sitka 

spruce and hemlock predominated in both areas. In the 

last 3,500 years hemlock predominated in both areas. In 

the last 3,500 years hemlock and Sitka spruce have 

been luxuriant on the southeast coast. The shifting of 

forest areas with variation of glacier extents in the 

southeastern part of Alaska in the last 8,000 years was 

chronicled by Cooper (1923, 1931, 1937, 1942). 

A few isolated pollen studies have been made elsewhere in Alaska. For an area near Naknek on the Alaskan Peninsula, Heusser (1963a) showed that in postglacial time alder pollen predominated over birch pollen in 

the tundra until 7,000 years ago. Birch pollen reached a 

maximum between 7,000 and 3,000 years ago and then 

declined in percentage. Spruce migrated from the interior of Alaska (fig. 40) within recent centuries. Little 

is known of the tundra changes in the Aleutians during 

Quaternary time, but Anderson and Bank (1952) indicated pollen analyses will be fruitful. 

In interior Alaska during post-Wisconsinan time, the 

birch-white spruce forest expanded rather rapidly 

around 10,000 years ago from valley bottoms to reclothe 

the hills as tree line rose 450 to 600 m higher than it was 

during Wisconsinan time. In the Fairbanks area, retransported organic-rich silt (fig. 20), deposition of 

which began 10,000 years ago (Pewe, 1975) and is still 

going on, has abundant plant remains, including rooted 

stumps. This silt is termed the Ready Bullion Formation (Pewe, 1975). Peat beds 25-30 em thick can be 

traced for 25 m. Taber (1943, p. 1538) was the first to 

recognize the unconformity between the Wisconsinan 

and Holocene sediments when visiting the Fairbanks 

area in 1935; however, he attributed it to erosion during 

Yarmouth interglacial time. 

Matthews (unpub. data, 1968) showed from a study of 

pollen from cores at Isabella Creek at Fairbanks that a 

climatic change occurred about 10,000 years ago and 

spruce became common around 8,000 years ago. Detailed pollen work by Rampton (1971) at the AlaskanCanadian border at the head of the Tanana River indicated a climatic amelioration around 10,000 years ago, 

with the invasion of shrub tundra and the invasion of a 

spruce woodland by 8, 700 years ago. Detailed study of 

the late Quaternary stratigraphy in the Fairbanks 

area, including occurrence of megafossil remains of 

spruce, leads the writer to believe that scattered stands 

of spruce remained in lowlands in central Alaska during Wisconsinan time. Reinvasion of the forest began 

about 10,000 years ago (Pewe, 1975) from these low-
88 QUATERNARY GEOLOGY OF ALASKA 

lands. This view contrasts with Hopkins' (1972) opinion 

that invasion occurred around 8,500 years ago from a 

refugium on the exposed continental shelf(Beringia) in 

the vicinity of Nunivak Island. 

As many as three spruce forest layers are superimposed upon one another (Giddings, 1938; Pewe, 1952a) 

in this Holocene formation at Fairbanks. The trees are 

typical of those today; the wood, which is excellently 

preserved in the frozen ground, differs only in color from 

trees of the modern interior forest. The superimposed 

forest layers have been cross-dated by tree-ring counting (Giddings, 1938), but the chronology outlined has 

not been connected with a chronology extending to 

present time. 

Isolated pollen analyses on post-Wisconsinan sediments from localities along the highways in central 

Alaska indicate spruce dominance throughout the sections (Hansen, 1953; Gerard, 1954). In addition toterrestrial flora, diatoms were recovered from pond sediments of Wisconsinan age in central Alaska (Taber, 

1943; Pewe, 1952a), Kenai Peninsula (Plafker, 1956), 

and near Palmer (Moxham and Eckhart, 1956). No 

stratigraphic, climatologic, or taxonomic importance 

can be ascribed to them at this time. 

Much work remains to be done toward refining the 

sequences of floras in the Pleistocene of Alaska. The 

large nonglaciated areas will undoubtedly provide most 

of this material, as they have to date. There are already 

clear indications of changes in the position of tree line 

and in the composition of floras which can be related to 

the climate during glacial and interglacial times and 

the Wisconsinan thermal maximum. 

Several other disciplines, in addition to palynology 

and the study of megafossils, may yield interesting results. Among these is the possibility of establishing a 

tree-ring chronology that can tie together Holocene and 

late Wisconsinan events. Much work remains to be done 

on lake sediment cores, correlating them with other 

areas and fitting them to a radiocarbon date chronology. 

With the continuing attemps to define the climatic requirements of modern arboreal and tundra species, the 

rather fragmentary record of vegetation distribution in 

Quaternary time will take on greater significance. 

FAUNA 

A rich fauna of Quaternary age is present in Alaska, 

but only in the study of the marine invertebrates and 

terrestrial vertebrates has a serious beginning been 

made. These preliminary studies have permitted 

statements concerning distribution and age of the 

fauna, and the marine invertebrates have also been 

instrumental in defining the times of emergence of the 

Bering land bridge, important to the coming of man to 

North America. 

INVERTEBRATES 

NONMARINE MOLLUSKS 

Fossil land and freshwater mollusks were reported 

near the turn of the century (Dall, 1905), but only recently has any systematic collecting relating to stratigraphy been done. Even though little can be done at 

present with nonmarine mollusks in Alaskan Quaternary stratigraphy, the writer has listed and summarized all finds for ready reference. 

TERRESTRIAL MOLLUSKS 

Fossil land mollusks are not abundant anywhere in 

Alaska except in loess of post-Wisconsinan age near 

Gakona and Chitina in the Copper River Basin. Here 

the Holocene loess is peppered with white shells, but 

this fauna has not been studied. A few mollusks were 

reported from loess of probable Wisconsinan age near 

Tofty (Repenning and others, 1964). The writer (Pewe, 

1955, p. 714) collectedSuccinea avara Say,Discus cronkhitei Newcomb, and Euconulus fulvus alaskensis 

Pilsbry. The last of these forms is identified by T. C. Yen 

of the U.S. National Museum, but the Succinea form is 

reported by Taylor (McCulloch and others, 1965, p. 450) 

to be less confidently identified. These species were 

found in loess less than 1,000 years old along the lower 

Delta River 160 km southeast of Fairbanks. These 

species also occur in loess of Wisconsinan age in Kansas 

(Leonard, 1952, p. 8) and Illinois (Leonard and Frye, 

1960). 

Fossil pulmonate snails were collected on the Seward 

Peninsula (D. M. Hopkins, unpub. data, 1955) and from 

near Rampart and Tanana (Mertie, 1937, p. 192), and 

Succinea strigata Pfeiffer (identified by J. P. E. Morrison, U.S. National Museum) was collected from loess at 

depths of 1-2.5 m near the Yukon River at the west end 

of Yukon Flats (J. R. Williams, unpub. data, 1960). Late 

Wisconsinan and Holocene forms were found in sediments of Kotzebue Sound (table 9) (McCulloch and 

others, 1965). 

Until more is known about both modern and fossil 

forms and more collections are available, however, it is 

not possible to make any positive statements about the 

importance -of Quaternary terrestrial mollusks in 

Alaska. 

FRESHWATER MOLLUSKS 

Near Fairbanks (fig. 20), retransported silt of Wisconsinan age rich in organic remains yielded the gastropods Helisoma subcrenatum (Carpenter), Stagnicola 

palustris (Muller), Gyraulus parvus (Say), and Valvata 

lewisi (Currier); the pelecypods Sphaerium tenue 

(Prime) and Pisidium casertnum are also present 

(Pewe, 1952a, p. 119--120). Taber (1943, p. 1491) also 

recorded the first three of these snail species in silt near 

Fairbanks. Mertie (1937, p. 192-193) listed fossil mol-
FAUNA 89 

TABLE 9.-Fossil nonmarine mollusks from the Kotzebue Sound area, northwestern Alaska 

[After McCulloch and others (1965, table 1). Numbers in column ht:adings are U.S. Geological Survey Cenowic locality numbers I 

Fossil 

Pelecypods: 

Anodonta beringiana Middendorff ____ ___ _ 

Sphaerium lacustre (Muller)? ---·---------

8. nitidum Clessin ---------------- ------ Pisidium casertanum (Poli) ____ _________ _ 

1.0 

~ 

~ 

C!:) 

~ 

Holocene 

c 

tU 

0 ~ ~ s 1.0 00 00 00 s ~ 

~ ~ ~ ~ 

C!:) C!:) C!:) :::; C!:) 

~ ~ ~ CIJ. ~ 

Late Wisconsinan to Wisconsinan early Holocene 

c c tU tU 

C!:) 0) 0 ~ ~ 0) ~ s ~ C!:) '<:t' ~ s ~ 

~ ~ t- t- t- t- 00 s ~ t- r- t- s ~ 

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 

~ C!:) C!:) C!:) ~ C!:) C!:) :::; ~ C!:) ~ C!:) :::; C!:) 

~ ~ ~ ~ ~ ~ ~ CIJ. ~ ~ ~ ~ CIJ. ~ 

xlx - X 

- - X 

- X X X - X X X -

X - X -xx x--x 

Sangamon 

t- '<:t' t- ~ ~ t- ~ ~ ~ 

C!:) C!:) ~ 

~ ~ ~ 

- X -

Late 

Illinoian 

c c tU tU 

s 00 ~ t- s 

s t- ~ ~ ~ ~ ~ s :::; C!:) ~ ~ :::; CIJ. ~ ~ ~ CIJ. 

X X X x · x - - ·x - x 

P. idahoense Roper--------------- ------- - X - I X - X - - X - - X X X X X X X X X X X X 

P. lilljeborgi Clessin _________ ___ ___ ____ _ X X - X X X X - X - X X - X X 

P. milium Held ----------------------- _ P. nitidum Jenyns ---- ------------·- ----- P. obtusale (Lamarck) _________________ _ 

Freshwater gastropods: ' 

X - -

X - XJ X X 

X ! - X X 

X - - . X 

x . xx- fx- - X - -

Valuata lewisi Currier ----------------·-- x I - Lymnaea ef. L. turricula Held _________ __ _ X XI X X X 

X, X xl X X X X X X X X X X fx X X X X - X 

X - - - -

L. randolphi Baker _____________ ____ ____ _ X - - X X ? X 

X 

X X 

X - X X X - - X X - ? X 

L. stagnalis (Linnaeus) ____ _________ ____ _ 

Gyraulus circumstriatus (Tryon) _____ __ _ 

G. paruus (Say) ----------------- ------- Armiger crista (Linnaeus) __ ·-____ ____ __ _ 

Helisoma subcrenatum (Carpenter) __ ___ _ Physa skinneri Taylor ______ ______ ___ __ _ 

Land gastropods: 

Discus cronkhitei (Newcomb) ___ ___ _____ x 

cf. succinea ______________ _ ------------- x X X X 

- - X 

X -

X I -

lusks collected by P. S. Smith from Quaternary silt 

deposits in this area. 

Gyraulus parvus (Say) and Valvata lewisi (Currier) 

were found in lake sediments radiocarbon dated as 

8,000 years old near ~datanuska glacier (J. R. Williams, 

written commun., 1964). F. R. Weber reported the freshwater pelecypod Pisidium lilljeborgii Clessin from late 

Quaternary sediments near the Porcupine River and 

from Cave-off Cliffs of the lower Yukon (oral commun., 

Jan. 20, 1963). Weber also collected Valvata lewisi 

(Currier) from late Quaternary sediments on the Porcupine River and at two localities in the YukonKoyukuk lowland. Hopkins (unpub. data, 1957) reported Pisidium sp., Valvata lewisi (Currier), Valvata 

helicoidea, and Stagnicola palustris (Muller) from 

Quaternary sediments near Tofty. 4 

A large collection of pelecypods and gastropods, made 

by McCulloch, Taylor, and Rubin (1965) near Kotzebue 

Sound, represents the first data available on specimens 

of pre-Wisconsinan age. As they point out (p. 442), however, our knowledge of geographic and stratigraphic 

differences between fossil and living groups in Alaska is 

so incomplete that we cannot at present use the faunas 

to interpret changes of climate and changes in geographic range of species. 

Sediments of Wisconsinan and post-Wisconsinan age 

4

Mollusks collected by Weber were identified by D. W. Taylor; tho:;e by Hopkins were 

identified by Taylor and by G. D. Hanna. The writer's specimens were identified by J.P. E. 

Morrison and R. D. Reger. 

X - - - -

- ! X - X 

X - - - -

- X X 

- X X -- x - ' x 

X - - - -

X X X - - - -

from the many lakes in Alaska are beginning to yield 

data on their fossil faunas (Livingstone and others, 

1958; Charlotte Homquist, unpub. data, 1959). 

Very little is known of the modern distribution of 

freshwater mollusks in Alaska, and this information 

seems essential to the interpretation of the fossil record. 

The gastropods Stagnicola palustris (Muller) and 

Helisoma subcreatum (Carpenter) live today in coldwater ponds in central Alaska, near Fairbanks and 

Galena (pl. 1). Hopkins (1963) stated that species of 

Valvata and Pisidium live in lakes in central Seward 

Peninsula today. In 1948 the writer collected specimens 

of Anodonta beringiana Middendorf from a clear-water 

tributary of the Yukon 16 miles southwest of Beaver, 

which represents one of the few localities in Alaska for a 

species that is probably widespread in both Alaska and 

Siberia (R. D. Reger, oral commun., Dec. 10, 1969). It is 

thought that this species migrated across the land 

bridge to Alaska in Illinoian or Wisconsinan time; these 

mollusks have not migrated farther east than the 

approximate position of the Wisconsinan continental 

ice sheet near the Canada-Alaska border. R. D. Reger 

and D. W. Taylor have compiled a wealth of unpublished information on freshwater mollusk distribution; 

this type of study has great promise for Alaska. 

The only study of living terrestrial and freshwater 

mollusks associated with modern glacier termini is the 

recent work of Tuthill (1970) near Martin Glacier in 

southern Alaska. This study was very helpful in relat-
90 QUATERNARY GEOLOGY OF ALASKA 

ing conditions of present glacier fronts to those that 

existed in Pleistocene time. 

MARINE MOLLUSKS 

The record of the Quaternary marine mollusks is 

much more completely known and useful than that of 

the terrestrial and freshwater mollusks. Marine ostracodes are reported but not yet widely used in stratigraphy (Swain, 1961; Schmidt, 1963; Schmidt and Sellmann, 1966). The foraminiferal fauna of the marine 

deposits of Quaternary age from northern Alaska was 

studied (Faas, 1962) and can be summarized as differing 

little, if at all, from those living in the same area today. 

This is equally true of the foraminiferal fauna from 

glaciomarine sediments from Juneau (Smith, 1970). 

Quaternary marine mollusks have been reported in 

Alaska since the turn of the century, but these data, 

plus later studies, were not of maximum stratigraphic 

use until the collections were reevaluated, compared 

with more recent collections, and put into stratigraphic 

position (Hopkins, 1959b; Hopkins and others 1960; 

Hopkins, 1965, 1967a). 

The record of the marine mollusks of Quaternary age 

in Alaska is from deposits formed by transgressions of 

the sea (p. 75). The information presented here is summarized from reports by Hopkins (1959b), Hopkins, 

MacNeil, and Leopold (1960), Hopkins (1965, 1967a), 

and McCulloch (1967). 

Marine invertebrates in deposits of the Beringian 

transgression (late Pliocene) have a decidedly modern 

aspect, but most have subtle differences from the living 

species. Some of the species are extinct. The stratigraphic distribution of the more significant fossils in 

marine sediments of Quaternary age in western and 

northern Alaska was summarized by Hopkins (1967a, 

table 2), Hopkins, MacNeil, and Leopold (1960, table 1), 

and McCulloch (1967, table 1). (See table 10.) 

Many of the extinct forms are unique to the deposits of 

the Beringian age and to Alaska. Some are related to 

Pliocene species of Japan or to the Pliocene and Pleistocene of California. Several living forms that are common in younger beds make their first appearance in 

Alaska in the deposits of Beringian age. 

Perhaps the most interesting observation to be made 

concerning the fauna of this age is in connection with 

the Bering land bridge as a barrier to migration of 

marine organisms. Hopkins (1959b, 1967b) pointed out 

that the bridge served as a barrier for marine organisms 

in the Pacific and Arctic Oceans. The presence of the 

large scallop Patinopecten (Ji'ortipecten) hallae (Dall) in 

Beringian deposits at Solomon and Kivalina north of 

Kotzebue indicates that by late Pliocene time a new 

seaway extended across the Bering-Chukchi platform, 

permitting marine organisms that had previously been 

TABLE 10.-Stratigraphic distribution of the more significant fossils 

found in marine beds of Pleistocene age in Alaska [From Hopkins 

(1967b )] 

Column hetUiinp: (1) Beringian, (2) Anvillan, (3) Einahnuhtan, (4) Kotzebuan, (5) Peluklan, 

(6) Woronzofian, (7) livina in Alukan -ten at pre~ent time. Symboll: Tapered enda of line 

indicate f"nt or lut recorded appearance In Aluka; aoUd Unes indicate pre~ence of animal 

firmly eatabUabed ; queried Unea indicate questionable identifications or questionable aae 

ualpment for encloain1 beda; duhed linea indicate animal probably pre~ent but hu not 

been collected. Note8: E-animal extirlet; EC-animal extinct but closely relatell to a llvina 

form ; A-nearest relative now cont)ned to North Atlantic; J-neareat relative now confined 

to Ja ane~e or Eutern Siberian -ten. 

Species 

GASTROPODA 

Margarltopm gronenorl Dall 

LittorlM sp. aff. L. pallltJta (Say) and 

L. nu~nd.rchurlCD Schenck 

Ejlitonium (Bont»ealtJ) groenltmdlcum (Perry) 

Tachyrhyncur er08U8 (Couthouy) 

1Wchotropm iMI,U Middendorf 

T. -biCDrlMtw (Sowerby) 

Amauropm purpuna Dall 

NattCD (CryptoNJtlca) janthMtoma Deshayes 

Trophon lcanuchatkanut Dall 

Bucctnum angulomm Gray 

Bucctnum frlngillum Dall 

Buccinum gltJcltJle Linne' 

Pyrulofu8W 8Chraderl Dall 

Pyrulo[u8U1 deformu (Reeve) 

&rlngiw kobeltt (Dall) 

PUcl{u8W sp. aff. P. waka.lanu.r Dall 

Neptunea lefflngweut (Dall) 

Neptunea herM me8lerl (Dall) 

Neptunea hero8 (Gray) 

Neptunea 8pp. 1 

Volutopnw sp. aff. V. ne{IUI#Oftl Dall 

Volutopnus ne{al'l#ont Dall 

Propebel4 sp. cf. _P. exqut.rtta Bartsch or 

P. tU81mtlU (Sara) 

PELECYPOD A 

YoldltJ koluntunenm Slodkewitsch 

Portltmd/4 arcttca (Gray) 2 

Chl4my.r(Leochl4mya) tugidaken811 MacNeil 

Chl4my.r (Swiftopecten) ldndlel (Dall) 

Chl4my8 (" Chl4my.r" ) coatn MacNeil 

Chl4my.r ("Chl4my8") coatn mtddletonenm MacNeil 

Chl4myt ("Chl4my8") Uotca Dall 

Chl4myt .(Chl4myl) berlngiana colv/UeiUU MacNeil 

Chl4my8 (Chl4my8) hana8hte11M!8 amchttkaNJ MacNeil 

Chl4my8 (Chl4my.r) pl4fkerl MacNeil 

Chl4my8 (ChltJmy.r) l814ndtca kaNJgae MacNeil 

Chl4my8 (Chl4myl) ill4ndtca powern MacNeil 

Forttpecten hall4e (Dall) 

Anarte actt.r Dall 

A8tarte nortonen818 MacNeil 

A.rtarte borealu Schumacher' 

Anarte browerl Meek 

Anarte lefllngwelll DaD 

Anarte hemtcymatll Dall 

Anarte sp. cf. A. 1oror Dall 

..tnarte sp. aff. A. bennettt Dall 

Anarte bennettt DaD 

Protothaca adamn (Reeve) 

TelUna (Perontdea) lutea Gray 

Macoma sp. cf. C4rlotte!UI4 White•ves 

Macoma baltica (Linne') 

StUqua patul4 (Dixon) 

Mya (Arenomya) japontca Jey 

CyrtodprltJ kumaNJ (Dunker) 

ECHINODERMATA 

Echinocyamw sp. cf. E. pu8illu8 (Muller) 

CIRRIPEDIA 

Verruca awkana Pilsbry 

1 2 3 4 5 6 7 NC?tea 

A or J 

E 

J 

J 

EC 

E 

EC 

J or A 

E 

E 

EC, J 

E 

E 

E 

EC 

EC 

E 

EC 

EC 

E 

E? 

EC 

EC 

E 

E 

A 

EC 

A 

E 

1 Berinpan and Anvilian beds contain complexes of Neptuneu, in addition to those listed 

above that are ancestral to but distinct from several modem species. 2 PortlimdltJ atv:tiCD has not been found in Alaskan beds older than the. Kotzebuan trans~res

lion. but it is pre~ent in Chukotka in the Pinakul' beda of Einahnuhtan age. 

'A.rtarte boreaU8 is found throughout the Pleistocene marine sequence of TjOmes, Iceland 

(Einar110n and othen, 1967), but this stock is represented in the older part of the Alaskan 

Pleistocene sequence by the closely related A . nortoneiUU. 

confined to the north Pacific Ocean to migrate northward. 

Marine invertebrates of the Anvilian transgression 

are best known from N orne and the Arctic coast and 

consist largely of forms living in adjoining waters at the 

present time. Some new forms first appear here. Extinct 

Neptunea heros mesleri andAstarte leffingwelli occur in 
FAUNA 91 

deposits of this age along the Chukchi Sea (McCulloch, 

1967) but not in deposits younger than those of the 

Einahnuhtan transgression. Several fossil forms are 

closely related to species now limited to waters adjoining Japan, or to the North Pacific Ocean or southern 

Bering Sea. 

The faunas of the Einahnuhtan transgression are 

essentially modern in character (table 10). 

Marine invertebrates of the Kotzebuan transgression 

(Yarmouth age) are best recorded in deposits from Kotzebue Sound. A rich molluscan fauna there consists 

entirely of species living in nearby waters at the present 

time. No extinct forms are present. Portlandia arctica 

(Gray) and others made their first recorded appearance 

in western Alaska at this time. 

Molluscan faunas of the Pelukian transgression 

(Sangamon age) consist entirely of living forms, with 

the exception of the extinct Cardita (Cyclocardia) subcrassidens MacNeil. Fossils of this age have been reported from northern and western Alaska and Pribilof 

Islands. Several forms are limited in their present distribution to areas well south of their northernmost fossil occurrence. Myajaponica Jay made its first Alaskan 

appearance in Pelukian beds. 

For the most part, marine mollusks of Quaternary 

age in Alaska record cool-water environments. Early 

Quaternary and late Pliocene forms indicate a warmer 

marine environment, but mollusks of middle and late 

Quaternary time indicate water temperatures about 

the same as now except perhaps during Sangamon time. 

The fauna is essentially modern in character, with a 

few to many extinct forms recorded in deposits of early 

Quaternary and late Pliocene age, but with only a rare 

extinct form in deposits of middle to late Quaternary 

age. An understanding of Quaternary marine deposits 

and associated fauna in western Alaska is now available and may stimulate study of the other coastal areas 

in the State. 

INSECTS 

A new and potentially important method of paleoenvironmental study of the Quaternary deposits of Alaska 

is based on examination of fossil insects, mainly beetles, 

from the frozen peats and silts. Well-preserved fossil 

insects occur in sediments in Alaska, but no studies 

have been done until recently. 

Spurred by the success of recent studies of insects of 

Pleistocene age in England, work was initiated on the 

frozen deposits near Fairbanks. A pioneer effort by 

Matthews (1968a, b) has led to enlarged studies elsewhere in Alaska. Beetles, because of their rather 

specific habitat preferences, may be more sensitive to 

climatic change than plants and may eventually provide a more detailed record than pollen. 

Matthews' study (1968a, b) of the carabid beetles 

(ground beetle) from the retransported silt of 

Wisconsinan age (fig. 20) from a mining exposure at Eva 

Creek (fig. 29) near Fairbanks indicated that there was 

a tundra environment during Wisconsinan time, that 

coniferous tree line must have been below the present 

elevation of the Eva Creek, and that the area was essentially treeless. This interpretation of the environment is 

also borne out by analysis of pollen from Eva Creek by 

Matthews (1968b, p. 222) and earlier work by E. S. 

Barghoorn (written commun., Nov. 23, 1954) on pollen 

samples collected by the writer. Matthews (1974) has 

now extended his study of insects to deposits at Cape 

Deceit in western Alaska and obtained challenging 

data on paleoenvironments of Pleistocene time. The 

writer believes that a great opportunity exists to extend 

this type of work elsewhere in the State and that only 

the beginning has been made in such paleoenvironmental studies. 

BACTERIA IN PERMAFROST 

The possibility that viable bacteria may exist in permafrost of Pleistocene age has intrigued microbiologists 

for many years, for such bacteria could be the oldest 

living organisms in the world. Investigations by Kriss 

(1940) in the Arctic of U.S.S.R. and James and Sutherland (1942) in Churchill, Canada, revealed bacteria in 

permafrost, but no age assignment is available. Becker 

and Volkmann (1961) recovered eight bacteria of four 

genera from a core taken from permafrost at the U.S. 

Army Cold Regions Research and Engineering Field 

Laboratory on Farmer's Loop Road at Fairbanks. 

Becker continued the project for several years with drilling at Ready Bullion Creek (Pewe, 1965a, p. 24) near 

Fairbanks but felt the absence of true sterile conditions 

prevented a positive proof of existence of viable bacteria 

in permafrost (oral commun., 1965). Boyd and Boyd 

(1964) carefully examined permafrost in large drill 

holes near Barrow and found a few living bacteria but 

noted that these may have been from the surface and 

not of Pleistocene age. Kj0ller and _0'dum (1971) carefully sampled permafrost from Ready Bullion Creek 

and believe it probable that living microorganisms are 

present in the frozen Pleistocene sediments. Obviously, 

too little is known of this subject and more detailed work 

should be undertaken. 

VERTEBRATES 

Alaska, like northern Siberia, has long been famous 

for the abundant remains of extinct Pleistocene mammals, found in frozen deposits along major rivers and in 

the valleys of many minor streams. The earliest account 

of these fossils seems to be that of Kotzebue (1821, p. 

21~220), who found abundant vertebrate remains at 

Elephant Point in Eschscholtz Bay during his expedition to the Chukchi Sea in 1816. F. W. Beechey also 
92 QUATERNARY GEOLOGY OF ALASKA 

collected there, and the mammal bones were reported 

by Buckland (1831). Because early explorers (Dall, 

1869, 1873) reported a great abundance of bones, several expeditions were conducted in Alaska in the hope of 

finding complete skeletons or perhaps even frozen carcasses comparable with those found in Siberia (Maddren, 1905; Gilmore, 1908; Quackenbush, 1909). When 

large-scale gold mining began in the Fairbanks district 

in 1928, extensive fossil collecting was undertaken 

there and elsewhere in Alaska by the late 0. W. Geist 

and others on behalf of the American Museum of 

Natural History. A small part of this material has been 

described by Frick (1937) and Skinner and Kaisen 

(1947). Later, Geist and others collected vertebrate fossils from the Fairbanks area and northern Alaska for 

the Museum of the University of Ala§ka. Some of the 

most detailed work ever done on the late Pleistocene 

mammals in central and western Alaska was that by 

Guthrie (1966a, b, c; 1967; 1968a, b; Guthrie and 

Matthews, 1971), who studied collections that he had 

made, as well as the vast collection of Geist. 

DISTRIBUTION 

Most of the remains of land mammals are from the 

unglaciated part of Alaska (fig. 42). Such distribution is 

to be expected because animals were mostly absent .in 

glaciated areas during glacial maximums and glacial 

advances tended to destroy or cover earlier fossil remains. 

The greatest collection of vertebrate specimens is 

from the Fairbanks area, where tens of thousands of 

specimens have been collected during the past 30 years. 

For example, in 1938, a typical year, 8,008 cataloged 

specimens weighing about 8 tons were collected by 0. 

W. Geist and shipped to the American Museum of 

Natural History in New York City (University of 

Alaska, ((Collegian," 1938, fall). Partial lists of mammals from the Fairbanks area were given by Frick 

(1930, 1937), Wilkerson (1932, p. 422), Mertie (1937, p. 

191), Stock (1942), Hibben (1943), Taber (1943, p. 1487), 

Skinner and Kaisen (194 7), Skarland (1949, p. 

132-133), Pewe (1952a, table 4), Geist (1953), Pewe and 

Hopkins (1967), and Guthrie (1968a). 

The geological literature (U.S. Geological Survey 

Bulletins) in Alaska dealing with early placer mining 

activities mentions in passing that bones of extinct 

animals such as mammoth, mastodon, bison, horse, and 

others were found in many localities in addition to the 

Fairbanks area. Vertebrate remains on the Seward 

Peninsula were mentioned by Collier (1902), Quackenbush (1909), Hopkins (1963), Harington (1970a, b), and 

many others. Mertie (1937, p. 190-191) summarized 

finds of several specimens from the Yukon-Tanana Upland. Whitmore and Foster (1967) listed finds from 

Chicken and Lost Chicken Creek, including Panthera 

atrox, and Repenning, Hopkins, and Rubin (1964) listed 

fossils from Tofty. 

Chapman and Sable (1960, p. 124) mentioned mammoth tusks found along banks of the Utukok and 

Kokolik Rivers of northern Alaska. Other references to 

vertebrates on the Arctic Coastal Plain (pl. 1) were 

made by Livingstone, Bryan, and Leahy (1958), 

Harington (1969), and others. William Quaide (unpub. 

data, 1953) collected mammal remains along the Kuk 

and Ikpikpuk Rivers in northern Alaska, and Robert 

Fladeland identified wolf, bear, large cat, ma1nmoth, 

horse, moose, caribou, musk ox, and bison. ASaiga bone 

was also identified in this collection by C. R. Harington 

(C. E. Ray, oral commun., Feb. 12, 1970). C. A. Repenning (written commun. to D. M. Hopkins, Feb. 5, 1962) 

provisionally identified many vertebrate remains collected by W. J. Maher from the Ikpikpuk River including Smilodon sp. and Felis (Lynx) lynx. Ray (1971) reported that bones of the woolly mammoth were found on 

St. Lawrence, Pribilof, and Unalaska Islands on the 

Bering-Chukchi platform. 

STRATIGRAPHY 

Unfortunately, the stratigraphic context of most of 

the vertebrate material of Pleistocene age from Alaska 

now in museums is unknown. Fossils are most readily 

seen when the enclosing matrix has been washed away, 

and so most of the vertebrate fossils have been found 

lying loose on beaches or riverbanks and the floors of 

placer-mining excavations. Furthermore, detailed 

studies of Alaskan Quaternary stratigraphy did not 

begin until the late 1940's; thus even when bones were 

collected in situ in earlier years, no conclusions could be 

drawn as to the age of the enclosing matrix. Skinner and 

Kaisen's (194 7) thorough study of fossil Bison is based 

upon Alaskan material whose stratigraphic context is 

not known; their speculations on Bison evolution are 

therefore based entirely upon the morphology of the 

skeletal material and upon assumptions as to probable 

evolutionary trends in critical dimensions such as horn 

width and tooth size. The great collection of Pleistocene 

mammal bones from the Fairbanks area in the Frick 

Laboratory of the American Museum of Natural History will be important in many taxonomic studies, but 

stratigraphic relations are missing. 

During the last two decades, a modest but growing 

number of vertebrate fossils have been found in 

significant stratigraphic contexts, most in the Fairbanks area but a few elsewhere. Most were in beds of 

Wisconsinan and Holocene age, but a significant few 

were in beds of Sangamon, Illinoian, and pre-Illinoian 

age (Pewe and Hopkins, 1967; Guthrie and Matthews, 

1971). Extensive collections of bones of small mammals 
FAUNA 93 

from silts near Fairbanks by Guthrie (1968b) are from 

sections where stratigraphy has been established. 

(Pewe, 1952a). 

PRE-ILLINOIAN 

Vertebrate remains of pre-Illinoian age are rare. 

Hopkins (in Pewe and Hopkins, 1967, p. 26&-269) found 

bones of Bison (Superbison) sp., Rangifer, and 

Dicrostonyx torquatus in beds of the Kotzebuan transgression at Kotzebue Sound, which he interpreted to 

have been deposited during a pre-Illinoian(?) interglaciation. 

Mammoth bones were found in the perennially frozen 

auriferous gravel in the Fairbanks area by early workers (Prindle, 1908, p. 32). The writer collected specimens of mammoth and bison from the gravel deposits 

that underlie Illinoian and Yarmouth(?) beds and 

thinks that these gravel units represent sediments laid 

down during one or more pre-Illinoian glacial intervals. 

These finds of Bison in central and western Alaska are 

perhaps the earliest recorded evidence of these genera 

in North America. The finds of Rangifer and 

Dicrostonyx were until recently the earliest recorded in 

North America. 

The only record of early Pleistocene mammals in 

Alaska was reported by Guthrie and Matthews (1971) 

from Cape Deceit on the south shore of Kotzebue Sound 

near Deering (pl. 1). A complex sequence of peat and 

organic rebedded loess (the Cape Deceit Formation) 

contains representatives of the genera Canis, Rangifer, 

Cervus, Ochotona, Lemmus, Microtus, andPliomys and 

a newly described genus and species, Predicrostonyx 

hopkinsi-predecessor of the extant genus Dicrostonyx 

(table 11). Guthrie and Matthews stated that, in addition, new species of Ochotona, Pliomys, and Microtus 

occur. From the stage of evolution of the fossils and from 

a study ofthe stratigraphy, it is assumed that the Cape 

Deceit Formation is at least pre-Cromerian in age. The 

Cape Deceit fauna contains the earliest North American record of Rangifer, Equus, and Microtus and the 

only North American record of Pliomys. 

ILLINOIAN 

The list of documented finds of fossil mammal remains of Illinoian age is slowly growing. Pewe (1952a, 

1958a, 1965a) reported such occurrences, and with continued work on Pleistocene mammal finds and interest 

in land bridge migrations (Hopkins, 1967a), a clear 

picture is beginning to appear. Much more work, however, is necessary to understand better the Palearctic 

and Neararctic mammalian dispersal in late Cenozoic 

time. 

All the finds of mammalian fossils known to the writer to be from Alaska sediments recognized as preWisconsinan are given in table 11. The evidence upon 

which the stratigraphic dating is based was discussed 

by Pewe (1952a, 1965a; Fairbanks area), Wahrhaftig 

(1958; Nenana Valley), Williams (1962; ChandalarValley), Hopkins, MacNeil, and Leopold (1960; Nome area), 

McCulloch, Taylor, and Rubin (1965) and Guthrie and 

Matthews (1971; Kotzebue Sound area), and Pewe, 

Hopkins, and Giddings (1965; Alaska in general). Many 

of the finds were discussed by Pewe and Hopkins (1967). 

From table 11, it is evident that many taxa were 

present in North America earlier than is generally recognized. One of the most recent good summaries of 

Quaternary mammals in North America (Hibbard and 

others, 1965, tables 2, 3; Flint, 1971, p. 766--768) indicated no pre-Wisconsinan record for Rangifer, Ovibos, 

Ovis, Alces, Saiga, Bootherium, Symbos, and 

Dicrostonyx and no pre-Illinoian record for Bison. 

Kurten (1968, p. 26&-269) also stated thatBison did not 

migrate to North America until Riss time and that 

Rangifer, Ovibos, and Saiga did not migrate to Alaska 

from Eurasia until Wurm time. However, all these genera listed by Hibbard and Kurten were present in 

Alaska by at least Illinoian time and represent 

Eurasian immigrants. Rangifer was in North America 

in early Pleistocene time. The find of Bison in the Fairbanks area in deposits of pre-Illinoian age is consistent 

with Flerow's (1967) idea that Bison priscus crassicornis migrated from Asia to America before the Riss 

Glaciation. 

The Siberian steppe antelope, Saiga (fig. 42), was 

found in the Pleistocene deposits of Alaska. The earliest 

published find was that ofO. C. Kaisen and 0. W. Geist 

at Lillian Creek near Fairbanks in 1930 (described in 

Frick, 1937). Geist and others also collected Saiga from 

Gold Hill in 1952, Cripple Creek Sump in 1949, Gilmore 

Creek in 1931, and Goldstream Creek in 1933 (M. F. 

Skinner, written commun., Mar. 3, 1970). Recently, 

Guthrie (1968a, p. 353) identified bones of Saiga collected by Geist from Cripple Creek in Gold Hill. John 

Dorsh collected the left metatarsus of Saiga from Banner Creek in 1935. Saiga was identified in the collection 

by William Quaide from the Arctic Coastal Plain from 

Alaska (C. E. Ray, oral commun., Feb. 12, 1970). The 

writer believes the Cripple Creek Sump and Gold Hill 

specimens are Illinoian in age; other specimens could be 

either Illinoian or Wisconsinan in age, most likely the 

latter. C. R. Harington of the National Museum of 

Canada is describing the Alaska specimens (written 

commun., July 10, 1970). 

Saiga is found nowhere in North America but Alaska; 

this area represents the easternmost extension of its 

Siberian range (Sher, 1967, p. 110). Southward penetration from Alaska by this animal was probably prevented by mountains, thick snow blankets, glaciers, or 

forests, because Saiga requires an environment of 
FIGURE 42.-Mammals of late Wisconsinan time. View is toward the southeast, across the westward flowing Tanana River near Fairbanks; Alaska Range is in background. 

Mural by J. H. Matternes. (Reproduced through the courtesy of National Geographic Society, copyright 1972.) 

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FAUNA 95 

plainlike relief with a hard surface, little forest, and 

little snow. The writer believes that such an environment existed in late Pleistocene time in Alaska on the 

windswept, fiat, braided flood plains of glacial streams 

that were abundant at that time. 

The yaklikeBos is another Siberian animal that was 

rare in Alaska in Pleistocene time and that did not move 

southward into North America. Since Frick's early description, other bones in the Geist collection have been 

identified as Bos from four different creeks in the Fairbanks area (Guthrie, 1968a), but they have no stratigraphic context; remains from Gold Hill perhaps are 

Illinoian. Future work on the Alaskan collection in the 

American Museum of Natural History may enlighten 

our concept of Bos in Alaska. 

Perhaps the only Pleistocene mammal that may have 

been restricted to pre-Wisconsinan time in Alaska is the 

extinct musk ox, Praeovibos. C. E. Ray (written commun., Oct. 25, 1967) reportedPraeovibos was quite rare, 

for all the identified specimens are from the Fairbanks 

area; only five brain cases or frontlets can be identified 

with reasonable certainty, and two fragmentary specimens are doubtfully referable to this genus. The five 

specimens come from Cripple Creek Sump, one example 

from Gold Hill, and are probably Illinoian in age. A 

specimen from lower Cleary Creek may be either Illinoian or Wisconsinan, but no stratigraphic information is available. 

Until recently, Praeovibos was known from only the 

middle Pleistocene deposits of Western Europe 

(Kahlke, 1963), but Sher since foundPraeovibos in middle and eastern Siberia in deposits of pre-Illinoian age 

(Vangengeim and Sher, 1970; Sher, 1969, 1971). 

WISCONSINAN 

DISTRIBUIION 

Most of the fossil vertebrate remains of Quaternary 

age in Alaska occur in frozen silt deposits of Wisconsinan age and are common in central, western, and northern Alaska. From Seward Peninsula Hopkins (1963) 

reported mammoth, horse, and bison remains in deposits of known Wisconsinan age. 

The most abundant large mammal remains in the 

Fairbanks area are those of the bison (fig. 42). The 

mammoth (M ammuthus primigenius) and horse (Equus 

alaskae and other species) are next in abundance (Pewe, 

1952a, p. 121). Bison (Superbison) crassicornis is the 

most abundant of the four bison types defined by Skinner and Kaisen (1947, p. 141), making up 87 percent of 

the total bison skulls. All four bison subgenera established by Skinner and Kaisen from central Alaska are 

known to occur in sediments of Wisconsinan age. The 

revision of the bison classification by Skinner and 

Kaisen is not accepted by all workers; Guthrie p966a, 
96 QUATERNARY GEOLOGY OF ALASKA 

TABLE 11.-Mammal remains found in beds of pre-Wisconsinan age in Alaska 

[From Pewe and Hopkins (1967), with additions (footnoted)] 

Fossil 

Order Rodentia: 

Castor sp (beaver)------------------------------------ Marmota sp. (marmot) __________________________ _____ _ Ondrata zibethecus (muskrat) _______________________ _ 

Pliomys sp. (meadow mouse)-------------------------- deeringensis (meadow mouse) ___________________ _ 

Microtus gregalis (vole) ------------------------------ sp. (vole) _______________________________________ _ 

deceitensis (vole) _______________________________ _ Lemmus sibericus (lemming) _________________________ _ 

cf. sibericus (lemming) -------------------------- Dicrostonyx torquatus (collared lemming) _____________ _ 

])o ----------------------------------------------

])0 ----------------------------------------------

Discrostonyx henseli -------------------------------- Predicrostonyx hopkinsi ------------------------------ Citellus undulatus (ground squirrel) _________________ _ 

1)0----------------------------------------------

sp. (ground squirrel) ---------------------------- Order Lagomorpha: 

Ochotona whartoni (pika) ----------------------------

I>o --------------------------------------------- Order Insectivora: 

Sorex (Sorex) sp. (shrew) _____________________________ _ 

Order Carnivora: 

Ursus sp. (bear) _____________________________________ _ 

Xenocyon sp. (hunting dog) -------------------------- Canis sp. (wolO -------------------------------------- Canis(?) sp. (wolO ------------------------------------ Vulpes sp. (fox) -------------------------------------- Felis sp. (large cat) ---------------------------------- Order Proboscidea: 

Mammut sp. (mastodon) _____________________________ _ 

Mammuthus sp. (mammoth) --------------------------

I>o ---------------------------------------------- I>o ---------------------------------------------- Order Artiodactyla: 

Cervus sp. (elk)--------------------------------------

cf. elaphus (elk)----------------------------------

Cervalces sp. (giant elk) ------------------------------ Alces sp. (moose) ___________________ .:. _______________ _ 

Rangifer sp. (caribou) --------------------------------

I>o ---------------------------------------------- I>o ---------------------------------------------- Saiga sp. (steppe antelope)_ __________________________ _ 

Bison (Superbison) sp. (large bison) _________________ _ 

])o ----------------------------------------------

])o ---------------------------------------------- ])o ----------------------------------------------- Bootherium sp. (extinct musk ox)_ ____________________ _ Ovibos moschatus (modern musk ox) _________________ _ 

sp. (musk ox) ------------------------------------ Symbos sp. (musk ox Bovid) -------------------------- Praeovibos sp. (extinct musk ox) ---------------------- Ovis sp. (mountain sheep) ----------------·------------ cf. Ovis sp. (mountain sheep)_ ____________________ _ 

Order Perissodactyla: 

Equus lambei (horse) -------------------------------- sp. (horse) _____________________________________ _ 

])o --------------------------------------------- - Order Pinnipedia: 

Odobenus sp. (walrus)-------------------------------- Eumetopias sp. (Steller's sea lion) ___________________ _ 

Order Sirenia: 

Hydrodamalis sp. (Steller's sea cow) _________________ _ 

Age 

Illinoian ------------------------------------ Early Pleistocene ---------------------------- Late Llinoian or Sangamon _________________ _ 

Middle Pleistocene----------------------------

Early Pleistocene ----------------------------

Illinoian ------------------------------------ Middle Pleistocene ___________________________ _ 

Early Pleistocene ----------------------------

Illinoian ------------------------------------ Early Pleistocene ---------------------------- Pre-lllinoian(?) interglaciation _______________ _ 

Illinoian ------------------------------------ do -------------------------------------- do -------------------------------------- Early Pleistocene ----------------------------

Illinoian ------------------------------------

do -------------------------------------- Early Pleistocene ----------------------------

do --------------------------------------

illinoian -------------------------------------

Early Pleistocene ----------------------------

Illinoian ________ -------- __ ---------- _______ _ 

do -------------------------------------- do -------------------------------------- Early Pleistocene ----------------------------

Illinoian ------------------------------------ do --------------------------------------

do -------------------------------------- do -------------------------------------- do -------------------------------------- Pre-lllinoian glaciation ----------------------

Illinoian ------------------------------------ Early Pleistocene ----------------------------

Illinoian ------------------------------------ do -------------------------------------- do -------------------------------------- Pre-lllinoian(?) interglaciation _______________ _ 

Early Pleistocene ----------------------------

lllinoian ------------------------------------ Sangamon ---------------------------------- Illinoian ------------------------------------ Pre-lllinoian glaciation _____________________ _ 

Pre-lllinoian(?) interglaciation _______________ _ 

Illinoian ------------------------------------ do -------------------------------------- do -------------------------------------- do -------------------------------------- do -------------------------------------- do -------------------------------------- do --------------------------------------

Illinoian(?) _________________________________ _ 

Illinoian ------------------------------------ Early Pleistocene ----------------------------

Sangamon ---------------------------------- do --------------------------------------

do --------------------------------------

6Harington (1970b). 

Location 

Fairbanks area. Cape ])eceit.l 

Kotzebue Sound area. Cape ])eceit. 1 

])o. 

Fairbanks area. 2 

Cape ])eceit.l 

])o. 

Fairbanks area.2 

Cape ])eceit.l 

Kotzebue Sound area. Fairbanks area. 

2 

Cape ])eceit. 1 

])o. 

])o. 

Fairbanks area. 2 

Fairbanks area.3 

Cape ])eceit. 1 

])o. 

Fairbanks area. 1 

Cape ])eceit. 1 

Fairbanks area. 4 

Fairbanks area. Fairbanks area. 5 

Cape ])eceit.l 

Fairbanks area. Fairbanks area. 5 

Fairbanks area. Nenana valley. 

Fairbanks area. 5 

Fairbanks area. 

Fairbanks area. 5 

Cape ])eceit.l 

Fairbanks area. ])o. 

Fairbanks area.5 

Kotzebue Sound area. Cape ])eceit. 1 

Fairbanks area.4 

Tofty mining district. 

Fairbanks area. 5 

Fairbanks area. Kotzebue Sound area. Fairbanks area. Nome area. 6 

Fairbanks area. 5 

Fairbanks area. 7 

])o. 

Fairbanks area. Nenana valley. 

Yukon Flats. 

Fairbanks area. 5 

Cape ])eceit.l 

Nome. 8 

St. Paul Island. 9 

Amchitka Island.1° 

1Guthrie and Mathews (1971). 2Guthrie (1968b, p. 232). 3Pewe, Fairbanks Creek, Fairbanks area, June 10, 1952. 

7C. E. Ray (written commun., Oct. 25, 1967). Stratigraphic interpretations by T. L. Pewe. 

4 0 . W. Geist (written oommun., Dec. 5, 1950). Stratigraphic interpretations by Pewe. Samples from Cripple Creek Sump. 5 In addition to specimens from Cripple Creek Sump given in Pewe and Hopkins(1967), Pewe and Geist collected bison, horse, mammoth, lion, fox, muskox, caribou, wolf, and elk from loess of lllinoian age in Gold Hill mining cut (unpub. data, June 1, 1952). 

Samples from Cripple Creek Sump. 

liD. W. McCulloch (written oommun., 1967). 90 . M. Hopkins (written oommun. from C. A. Repenning, Apr. 20, 1970). 10Gard, Lewis, and Whitmore (1972). 
FAUNA 97 

p. 739) believed that all the large extinct bison fossils in 

Alaska represent one species, Bison priscus (=B. crassicornis). 

Except for Citellus, the remains of small mammals 

had not been described in stratigraphic context from the 

Fairbanks area. Guthrie (1968b) made an exhaustive 

study of rodents that he carefully collected from known 

stratigraphic horizons. He found the following in sediments of Wisconsinan age: Microtus gregalis 

(predominant member of the assemblage), Lemmus 

sibericus, Dicrostonyx torquatus, Citellus undulatus. 5 

5Various species and subspecies names have been used for the ground squirrels in Alaska 

(Rausch, 1953). Citellus parryi (Richardson) was used in the older literature (Hill, 1942) but 

C. undulatus in the newer (Guthrie, 1968b). Rausch (1953, p. 121) pointed out that C. 

undulatus has priority over C. parryi. However, Liapunova and Vorontsov (1970), studying 

chromosomes of the Citellus and evolution of the various species, concluded that C. undulatus, C. pachyderma, and C. parryi are distinct species. (Similar habitats have resulted in 

the convergent similarity between C. parryi and C. undulatus, confusing to many taKonomists.) They further believed that C. undulatus became extinct over the territory from the 

right bank of the Lena River to Alaska and Canada during Sangamon time. In early 

Wisconsinan time, C. richardsoni migrated from the south and by late Wisconsinan time C. 

parryi had originated from it (Liapunova and Vorontsov, 1970, p. 1037). 

A detailed study (Repenning and others, 1964) of fossil rodents from the valley-bottom silt deposits of Wisconsinan and post-Wisconsinan age near Tofty, 150 km 

west of Fairbanks, listed the following: 

Lepus sp 

Spermophilus (Spermophilus) undulatus (Pallas) 

Beaver (gnawed wood) 

Discrostonyx torquatus 

Lemmus sibericus 

Synaptomys sp. (identified by T. M. Stout) 

Clethrionomys sp. (identified by T. M. Stout) 

Microtus miurus 

Microtus (large form) 

Also present in the Wisconsinan silt near Tofty are 

remains of Proboscidea?, Equus, Rangifer(?), Alces(?), 

Bison, bovid, and an unidentified fish. 

Most of the mammal remains from the Fairbanks 

area are from retransported valley-bottom silt of Wisconsinan age rich in organic material (figs. 20, 29; table 

TABLE 12.-Fossil mammals reported from perennially frozen creek- valley silt deposits of Pleistocene age in the Fairbanks district 

Name 

Insectivora: Shrevv _______________ _ 

Carnivora: Bear _________________ _ Do _______________ _ Do _______________ _ 

Dire vvolf _____________ _ Coyote _______________ _ Wolf _________________ _ Do _______________ _ Fox _________________ _ 

Badger _______________ _ 

Weasellike animal ___ _ Wolverine ___________ _ 

Saber-toothed tiger ___ _ Lion _________________ _ Lynx _______ __________ _ 

Proboscidea: Elephant _____________ _ ~astodon _____________ _ Do _______________ _ 

Perissodactyla: llorse _______________ _ Do _______________ _ Do _______________ _ 

Artiodactyla: Camel _______________ _ 

Antelope _____________ _ Do _______________ _ Do _______________ _ Bison _______________ _ 

Do _______________ _ 

Do _______________ _ 

Genus 

Genus not determined. 1 

Ursus sp. 2 

Ursus yukonensis Lambe.3 

U rs us arctos. 4 

Canis dirus alaskensis Frick.3 

Canis latrans. 4 

Canis sp. 5 

Canis lupus. 4 

Vulpes sp.2 

Taxidea sp.2 

Genus not determined.2 

Gulo sp. 5 

Smilodon sp.2 ,

4 

Felis atrox alaskensis Frick.3 

Felis (lynx) sp.5 

Mammuthus primigenius. 6 ,

7 

Mastodon sp.z 

Mastodon americanus alaskensis. 6 

Equus alaskae Hay. 3 

Equus lambei Hay. 8 

Equus caballus. 4 

Camelops race Gidley.3 

Saiga sp.2 ,

9 

Saiga ricei Frick.to,s 

Saiga tatarica. 4 

Bison (Superbison) crassicornis 

Richardson. 11 

Bison (}3ison) preoccidentalis 

S. and K. 11 

Bison (platycerobison) alaskensis 

Rhoads. 11 

'Pruitt (1955) (oral commun.; Arctic Aereomedical Lab., U.S. Air Force, Fairbanks, 

:'\Iaska). 

~i~~ ~i~~1}~5) (oral commun., research associate, Dept. of Paleontology, Univ. Alaska). 

4Guthrie (1968a). 5Geist (1953). 6Frick (1933). 7 0sborn (1942). sMertie (1937). 9Skinner (1970) (written commun., March 3, 1970) Am. Mus. Nat. History. 

Name 

Artiodacty !a-Continued 

Bison _______________ _ 

Caribou _____________ _ Do _______________ _ ~oose _______________ _ Do _______________ _ Elk _________________ _ 

Do-------~-------- Elk, giant ___________ _ 

SheeDo ================ _______________ _ ~usk ox _____________ _ Do _______________ _ 

Do _______________ _ Do _______________ _ 

~usk oxlike Bovide ___ _ Do _______________ _ 

Yaklike Bovid _______ _ Do _______________ _ 

Edentata: 

Groundsloth _________ _ 

Rodentia: 

Beaver _______________ _ 

Ground squirreL ______ _ Vole _________________ _ Do _______________ _ 

Lemming _____________ _ Do _______________ _ 

Collared lemming _____ _ Do _______________ _ 

Lag:~~~~h~e ------------

llare _________________ _ Pika _________________ _ 

10Frick (1937). 

Genus 

Bison (Platycerobison) geisti 

S. and K.U 

Rangifer sp. 5 

Rangifer tarandus. 4 

Alces sp.5 

Alces alces. 4 

Cervus sp.2 

Cervus elaphus. 4 

Cervalces alaskensis Frick. 10 

Ovis dalli kaiseni Frick. 10 

Ovis dorshi Frick. 1o 

Ovis nivicola4 

Ovibos yukonensis Gidley .

10 

(?)Ovibos giganteus Frick.10 

Ovibos moschatus. 4 

Praeovibos. 12 

Symbos tyrrelli Osgood.10 

Bootherium nivicolens llay. 10 

Bos sp.4 

Bos (Poephagus) bunnelli Frick. 10 

Megalonyx sp.13 

Castor sp.5 

Citellus parryi. 14,

15,16 

Microtus sp.5 

Microtus gregalis. 17 

Lemmus sp.2 

Lemmus sibericus. 17 

Dicrostonyx. 2 

Dicrostonyx torq uatus. 17 

Erethizon sp. 5 

Lepus sp.5 

Ochotona whartoni. ts 

11Skinner and Kaisen (1947); referred to as Bison Priscus by Guthrie (1966a, p. 739). 12Ray (1967), (written commun., Oct. 25, 1967) Supervisor, Div. Vertebrate Paleontology, Smithsonian Institution. 13Stock (1942). 14Hill (1942). 15Stout (1956) (written commun., Aug. 12, 1956) Univ. Nebraska. 16Guthrie (1968b) used the term "Citellus undulatus". (See footnote 5 and Rausch, 1953, p. 121.) 17Guthrie (1968b). '!Guthrie and Matthews (1971). 
98 QUATERNARY GEOLOGY OF ALASKA 

12). Most of the fossils are found in valley bottoms, 

owing to gradual downslope movement. Some transportation also occurs down the stream axes, and the 

greatest concentrations are found where small 

tributaries join large creeks. These great accumulations of bones are thus not ((animal cemeteries" or unnatural concentrations. Bones are recovered throughout a given valley and do not come only from ((bone pits" 

as stressed by Osborn (1942, p. 1035). Most vertebrate 

remains in interior Alaska are Wisconsinan; the 

vertebrate-rich valley-bottom facies of the loess of Illinoian age was, in most instances, removed before Wisconsinan sediments were deposited (fig. 20). 

The writer believes that all taxa reported from the 

perennially frozen silt in the Fairbanks area (table 11) 

are represented in silt of Wisconsinan age (fig. 42), 

except perhaps Praeovibos, because in most instances 

only sediments of Wisconsinan age were exposed in 

mining cuts at the times of collection. 

CARCASSES 

Frozen mammal carcasses have been known from the 

Arctic and subarctic for centuries (Nordenskiold, 1881, 

p. 408-410; Herz, 1904; Tolmachoff, 1929; Markov and 

Popov, 1959; Tikhomirov, 1958). The first direct report 

of a carcass of a mammoth in frozen ground of Siberia 

was by E. Yssbrants Ides in 1692 (Tolmachoff, 1929, p. 

21). 

Although not so well known as the Siberian carcasses, partial remains consisting ofbones with dried flesh, 

skin, or hair still clinging to them have been found in 

frozen silt (Dall, 1896, p. 857; Quackenbush, 1909, p. 

108-109; Wilderson, 1932, p. 6; Skarland, 1949, p. 68; 

Geist, 1940, 1953; Pewe, 1966c). Many important finds 

of carcasses have been from the retransported organicrich silt of Wisconsinan age in the Fairbanks area. 

Partial carcasses of mammoth, bison, musk ox, Symbos, 

Bootherium, moose, horse, lynx, caribou, and ground 

squirrel were found in the environs of Fairbanks (Pewe, 

1952a, p. 123-126). Several complete carcasses of the 

ground squirrel have been found in nests. The most 

celebrated find was the partial forequarters of a baby 

mammoth, collected in 1948 from Fairbanks Creek (fig. 

43) (Anthony, 1949). The well-preserved hide of the 

head, neck, trunk, and one front leg was about 6 mm 

thick and almost hairless. The partial carcass was preserved in commercial glycerine by the collector, 0. W. 

FIGURE 43.-Partial carcass ofajuvenile mammoth recovered in 1948 

by Otto W. Geist from perennially frozen silt of Wisconsinan age 

at Fairbanks Creek, 30 km northeast of Fairbanks, Alaska. 

Photograph from Bunnell Collection, University of Alaska. 
FAUNA 99 

TABLE 13.-Radiocarbon dates of Pleistocene mammals from the perennially frozen silt in the Fairbanks area 

[Specimens collected by 0. W. Geist were provisionally identified by Geist; they wer'.! then placed in the Frick Collection of the American Museum of Natural History and identification was confirmed by members of the staff of the American Museum. Laboratory numbers: ST =radiocarbon laboratory ofGeolo~cal 

Survey of Sweden, Stockholm; SI =radiocarbon laboratory of Smithsonian Institution, Washington, D.C.; GX =radiocarbon laboratory ofGeochron, nc., Boston; M = radiocarbon laboratory ofUniversity of Michigan, Ann Arbor; L = radiocarbon laboratory of Lamont Geological Observatory, New York; W = radiocarbon laboratory of U.S. Geological Survey, Washington, D.C.] 

Age Laboratory Collector Animal Sample years (B.P.) No. and year Locality Submitter Source Remarks 

Carnivora: Felis atrox Tendon from 22,680±300 SI 456 0 . w. Geist, Ester C. E. Ray - --- Stuckenrath 

left tibia. 1938. Creek. and Mielke (1970, p. 203). Proboscidea: Mammuthus Flesh from 15,380±300 SI 453 R. H. Osborne, Fairbanks R. H. Osborne __ _ ___ ____ do ________ 85 ft below surface; 

primigenius. lower leg. 1940. Creek. partial carcass. 

sp -------- Hide from 21,300± 1300 L 601 0 . W. Geist, ______ do ___ ___ W. R. Farrand_ . Farrand (1961). Hide soaked in 

carcass. 1948. glycerine by 

collector; date invalid(?). Do ------ Hair from 32,700±980 ST 1632 0. W. Geist, Dome Creek __ T. L. Pewe ____ Pewe (1965a, p. 33). skull. 1951. Perissodactyla: Equus __ ________ Bone -------- 26,760±300 SI 355 H. L. Foster, Lost Chicken F. C. Mielke and Long 1965. Creek. Whitmore, Jr. (1969, p. 177). Artiodacty Ia: Bison (Bison ) Hom sheath __ 11,735±130 ST 1631 0. w. Geist, Cleary T. L. Pewe ____ Pewe (1965a, p. 33). From internal piece of preoccidentalis. 1937. Creek type specimen; Do ____ __ do ______ 12,460±320 SI 290 ______ do __ __ __ _ _____ do ____ __ C. E. Ray ---- Mielke and Long Skinner andKaisen (1969, p. 177). (1947, p. 174-176). Bison ---- ------ ______ do ______ > 35,000 SI 844 0. W. Geist, Little Eldorado R. D. Guthrie __ Stuckenrath 

1938. Creek. and Mielke (1973, p. 397). preoccidentalis. ______ do ______ 5340±110 SI 845 0. w. Geist, Goldstream _ _____ do ____ Not preoccidentalis __ Stuckenrath 

1939. area. and Mielke or contamination 

(1973, p. 397). present Bison ______ do ___ ___ 29,295±2440 SI 842 0. W. Geist, Crlfr~~k. ______ do ______ Stuckenrath Small sample, diluted 

1940. and Mielke (1973, p. 397). Do ______ do ___ ___ > 39,000 SI 840 0. W. Geist, ___ ___ do ______ _ _____ do _____ _ Stuckenrath 

1947. and Mielke 

Do ___ ___ do ______ 21,065± 1365 SI 839 ______ do ____ __ (1973. p. 396). _ __ ___ do _____ _ ____ __ do __ ____ Stuckenrath and Mielke (1973, p. 396). Do _____ _ do ____ __ 18,000±200 SI 841 0. W. Geist, Manley Hot ______ do _____ _ Stuckenrath 

1948. Springs. and Mielke 

(1973,!"397). (Superbison) Hide from > 28,000 L 127 0 . W. Geist, Dome Creek __ 0. W. Geist -- Kulp an others, crasstcornts. carcass. 1951. (1952, p. 411). Do -------- Hide and hair 31,400±2040 ST 1721 ______ do ______ _ _____ do ______ T. L. Pewe ____ Pewe (1965a, p. 33). from carcass. Bison ---------- Hom sheath __ 17,170±840 SI 838 0. w. Geist, Fairbanks R. D. Guthrie __ Stuckenrath 1952. Creek. and Mielke (1973, p. 396). Do -------- ______ do ____ __ 20,445±885 SI 837 ____ __ do ______ _ _____ do ____ __ _ _____ do ___ ___ ________ do ______ __ 

preoccidentalis. _____ _ do ______ 31,980±4490 SI 843 0 . W. Geist, Fairbanks ____ ______ do _____ _ _ __ _____ do ________ Do. 

no date. 

(Super bison) ______ do ______ 16,400±2000 M38 __ ____ do ______ Creek near C. Hibbard ___ _ Crane (1956 p. 670). Date obtained by solid 

crass worms. Fairbanks. carbon method. 

(female). Hide from 11,980±135 ST 1633 ______ do ______ Fairbanks T. L. Pewe ____ Pewe (1965a, p. 33). 

carcass. Creek. Ovibos sp _______ ___ Hair from 17,210±500 SI 454 0 . W. Geist, Fairbanks C. E. Ray -----· Stuckenrath hind limb 1940. Creek. and Mielke 

Muscle 24,140±2200 SI 455 ______ do ______ ______ do ____ __ ____ __ do ____ __ --~~~~~~a~ ~~~~- --- From small from scalp. sample, 

diluted. 8ymbos -------- Hom 25,090± 1070 SI 850 0 . W. Geist, Cleary R. D. Guthrie __ Stuckenrath Do. 

sheath. 1939. Creek. and Mielke 

giganteus __________ Dung(?) > 40,000 SI 291 _____ _ do ______ Creek near C. E. Ray ----

(1973, p. 397). Mielke and Date may be 

Fairbanks. Long (1969 on gut. 

Symbos p. 177). 

---------- Hom 17,695±445 SI 851 0. W. Geist, Dome R. D. Guthrie __ Stuckenrath sheath. 1952. Creek. and Mielke, 

(1973'/"397). Bootherium ______ do ______ 22,540±900 SI 292 0. W. Geist, Creek near C.r.l a~ki~~er. Long an nivicoleus. 1935. Fairbanks. Mielke (1967, 

Rodentia: p. 380). 

Citellus Nest_ ___ ______ 14,760±850 GX 0250 T.L.Pewe Chatanika T. L. Pewe ____ Pewe (1965a, undulatus. 1963. River at p. 35). 

Livengood 

Road. Do -------- Coprolites ____ 14,510±450 w 2703 T. L. Pewe, ______ do ______ ______ do ______ M. Rubin 

1971 (oral commun., 1972). 

Geist; therefore the date of 21,300 ± 1,300 years must, 

unfortunately, be questioned (table 13). 

A partial bison carcass was found in perennially frozen silt at Dome Creek in 1951 during mining operations. The carcass consists of a head, complete with hide, 

horns, and one ear, as well as four legs with hooves; 
100 QUATERNARY GEOLOGY OF ALASKA 

FIGURE 44.-Partial carcass of an extinct bison, Bison (S uperbison) eras sicornis, discovered August 1951, in perennially frozen, retransported, 

organic-rich silt of Wisconsinan age during placer gold mining operations on Dome Creek, 13 miles north of Fairbanks, Alaska. Radiocarbon dated at 31,400 ( +2,040 or -1,815) years old (ST 1721). Collector, 0. W. Geist, is examining fragment of the hide. Photograph 

No. 600 by T. L. Pewe, September 3, 1951. 

much of the torso hide is about 4 mm thick (fig. 44). The 

carcass shows evidence of having been transported only 

a short distance. A date of more than 28,000 years old 

(L-217) was obtained on a piece of the carcass in 1951 

(table 13). In 1965 a date of31,400±2,040 years old CST 

1721) was obtained by the radiocarbon laboratory at the 

Geological Survey of Sweden on a piece of the same 

carcass (Pewe, 1965a). Pieces of fur and hide of a female 

superbison recovered from Fairbanks Creek near Fairbanks have been dated as 11,950± 135 years old (ST 

1633) (Pewe, 1965a). 

At Dome Creek near Fairbanks, a fairly complete 

skull and tusks of mammoth were recovered in the early 

1950's. The mammoth tusks are 3.7 m long (outside 

curve) and weigh approximately 160 kg apiece. Preserved with the skull was considerable mammoth hair 

which was dated at 32,700±980 years old (ST 1632) 

· (Pewe, 1965c). The writer submitted some of this hair to 

J. M. Gillespie, Senior Principal Research Scientist of 

Division of Protein Chemistry of CISRO, Australia, for 

examination. He reported (Gillespie, 1970) that although the mammoth hair at first sight seems undamaged, is intact externally, and is quite strong, it has, in 

fact, been extensively damaged, perhaps during decomposition that preceded freezing. This is additional evidence against instantaneous death and refrigeration. 

Some of the hair was also submitted to Prof. Shoichi 

Yada ofthe Department of Legal Medicine at Gifu University, School ofMedicine, Japan.He reported (written 

commun., May 13, 1971) that, morphologically, most of 

the specimens were in good condition, presumably 

owing to the extremely high resistance of the keratin 

tissue to decomposition. He further stated that the 

.mmoth h~ir is furn ished with an A antigen similar 
FAUNA 101 

to that of group A human hair and mentioned it is 

surprising indeed that the blood group A antigen occurring in the mammoth hair had successfully survived 

through tens of milleniums of weathering without losing its serological specificity. 

Within the last few years, samples of fleshy organic 

matter clinging to bones collected in the Fairbanks area 

in the 1930's and 1940's have been dated, especially by 

the Smithsonian Institution (table 13). R. D. Guthrie is 

continuing this work and is currently having approximately 100 mammal specimens from the Fairbanks 

area radiocarbon dated by the Smithsonian Institution. 

Many partial carcasses of rhinoceroses were reported 

from Quaternary deposits in Siberia (Tolmachoff, 1929, 

p. 20), but no carcasses or even bones of this animal have 

been recognized in Alaska. Flerow (1967, p. 273) believed the rhinoceroses did not migrate to Alaska because they were forest inhabitants and probably could 

not feed on the grass of the Bering land bridge. 

The frozen carcasses of extinct animals have long 

caught the fancy of the general public and scientist 

alike, especially the hugh mammoths reported from 

remote areas of Siberia. Stories quickly sprang up and 

have been repeated for many years, both in print and 

orally, regarding the mammoth meat being served at 

banquets, mammoths dying with buttercups in their 

mouths, and the large beasts perishing as cataclysmic 

climatic changes took place turning the tropical climate 

into the frigid Arctic. It is not necessary to envision such 

conditions to explain the distribution, preservation, and 

extinction of the ice age vertebrates as suggested over 

the years by Howorth (1887), Velikovsky (1955), Hapgood (1958, 1960), Hooker (1958), Sanderson (1960), 

Patten (1966), and Dring (1967). 

The presence of vertebrates of many species in the 

sediments of Illinoian and Wisconsinan age in Alaska 

abolishes the long-held idea that the animals must have 

lived only in interglacial times (Flint, 1957, 1971) or 

were exterminated by severe conditions of glacial times 

(Johnston, 1933, p. 32). Detailed work, especially near 

Fairbanks, demonstrated that all the carcasses are between 10,000 and 70,000 years old and could hardly be 

older because they probably would not have survived 

the Sangamon Interglaciation, a time when permafrost 

probably disappeared in central Alaska (Pewe, 1952a, 

1958b). It is evident that most of the permafrost present 

today in the Fairbanks area must have existed since 

Wisconsinan times to preserve the carcasses in nature's 

deep freeze. The geologic association, plus radiocarbon 

dates (table 13), indicates that the carcasses are Wisconsinan in age and not «a million years old," as casually announced. 

The mammoth, bison, and others lived on the 

tundra-covered hills and grassy flood plains (fig. 42), 

when a rigorous glacial climate prevailed. The tundra 

then, as today, supported several species of Ranunculus 

(buttercup) and Potentilla. For example, a fossil seed 

cache ofCitellus undulatus collected by the writer from 

Wisconsinan sediments in Dome Creek near Fairbanks 

was found by R. W. Browne (written commun., Jan. 29, 

1953) to consist of seeds of Ranunculus hyperboreus 

Rottboell (Arctic buttercup) and Potentilla sp. (a cinquefoil). Buttercups also made up a part of the diet of 

mammoths; pollen of Ranunculus has been found between the teeth and in the stomach of the frozen carcass 

of the Berezovka mammoth. Some mammoths did indeed die ((with buttercups in their mouths," but this is a 

perfectly natural association and occurrence. Virtually 

all evidence suggests that the carcasses represent 

natural deaths in a rigorous environment (Farrand, 

1961). 

HOLOCENE 

In the Fairbanks area no bones of extinct vertebrates 

have been found in the post-Wisconsinan sediments 

(figs: 20, 29). Only bones of living forms have been 

found. A complete frozen and untransported moose carcass was found in silt of Holocene age (Giddings, oral 

commun., Nov. 4, 1950). Guthrie (1968b) reported 

Microtus xanthognathus, a living form, from the frozen 

Holocene sediments at Eva Creek. Hopkins (1963) 

stated that there is no evidence for extinct species living 

after 11,000 years ago in the Seward Peninsula. He 

recorded the presence of beaver (Castor sp.) in central 

Seward Peninsula between 8,000 and 9,500 years ago 

and again around 3,500 years ago; they do not live there 

today. McCulloch reported an expanded range ofbeaver 

at about the same time in the Kotzebue Sound area 

(McCulloch and Hopkins, 1966). 

In the Holocene flood plain deposits of large streams, 

rare finds of Bison bison have been made. Geist stated 

(oral commun., 1950) that the finds of Bison bison reported in Skinner and Kaisen (1947) were from such 

sediments and that a bone of Bison bison was found in 

Holocene sediments of the Chena River (pl.1) at Fairbanks. 

The return of mammals to areas glaciated in Wisconsinan time, generally referred to as the postglacial distribution pattern of mammals, has been studied in 

temperate latitudes. However, except for Klein's work 

(1965) in the southern coastal regions, Karlstrom's report (1969) on Kodiak Island, and the studies of the 

distribution of early man in Holocene time, little systematic work has been done on this problem in Alaska. 

Perhaps the migration of mammals locally north and 

south from the large interior refugium presents no problem. Nevertheless, the present land areas of the coastal 

regions of Alaska bordering the Gulf of Alaska were 

virtually completely glaciated, and the present flora 
102 QUATERNARY GEOLOGY OF ALASKA 

and fauna of the region had to become established in the 

last 10,000 years, since the recession of the ice. Klein 

(1965) carefully showed that although some local refugia existed in this region, all large mammals in the 

region either migrated through mountain passes from 

the refugium in the interior of Alaska or came from 

south of the ice sheet. For example, the brown and black 

bear, wolf, goat, and mountain sheep probably came 

from the north as did one form of moose. Other moose 

forms and the blacktailed deer are known to have migrated from the south. 

EXTINCTION 

In Alaska, as in the rest of the world, many mammals 

became extinct at the end of Wisconsinan time. 

Moreover, many large mammal genera, grazers, browsers, and predators, present in both Illinoian and Wisconsinan time, became extinct. In Alaska the most 

common and largest were the bison, mammoth, and 

horse. These three grazers represent more than 90 percent of the large-mammal biomass (Guthrie, 1968a). 

Guthrie (1968a) concluded that during late Pleistocene 

time, vegetational patterns must have been radically 

different from those today, especially in central Alaska. 

He believed that a widespread grassland environment 

existed in the northern Holarctic region, rather than a 

shrub tundra or herbaceous tundra environment as exists today, and that it was the disappearance of this 

grassland that caused the animals to become extinct. 

It has long been known from studies of pollen and 

presence of grazers that tree line was lowered 450--600 

m in central Alaska and that the tundra environment 

was much more widespread than now. However, pollen 

studies by Livingstone (1955), Colinvaux (1967a), and 

Heusser (1963b) in western and northern Alaska did 

not indicate a ~~grassland" but, rather, an herbaceous to 

shrub tundra with some grass. Pollen analyses by E. C. 

Barghoorn on samples collected by the writer from critical localities in Illinoian and Wisconsinan sediments 

near Fairbanks indicated an absence of coniferous trees 

and the presence of a grass-sedge-moss cover with dwarf 

birch and willow, but no ~~grassland." 

A simple model of vegetation distribution in central 

Alaska during late Pleistocene time may account for 

extinction of a large percentage of grazers, in part without the necessity of postulating unique climatic conditions. During Illinoian and Wisconsinan time, all major 

and most minor streams in Alaska drained glaciated 

areas. These streams were extensively braided with 

wide, relatively fiat flood plains, and on the flood plains 

vegetation was in a disclimax condition. Such widespread, fiat flood plains also existed on the Bering land 

bridge. Evidence for the existence of these nonforested, 

wide, braided flood plains is the abundant loess of Illinoian and Wisconsinan age in Alaska adjacent to the 

flood plains (figs. 16, 20) (Pewe, 1951a, 1968a; Pewe and 

Holmes, 1964; Pewe and others 1966); the flood plains 

were the source of this loess (fig. 42). 

These extensive flood plains and adjacent low terraces in central, western, and northern Alaska were 

ideal locations for grasslands in Pleistocene time. The 

soil was well drained, permafrost table low, and muskeg 

at a minimum. Today the greatly restricted flood plains 

of glacial streams support grasslands. The two places 

where modern bison have successfully been introduced 

in central Alaska are in such habitats, and, 

significantly, extinction of the few lingering bison 

(Bison bison) of the great Pleistocene herds is recorded 

only in Holocene sediments oflarge glacial flood plains, 

and not in the creek valleys of the uplands where the 

Pleistocene bison remains are found. 

The wide grassy flood plains of major rivers were the 

home of and best food supply for the late Pleistocene 

grazers, especially in winter. In summer, undoubtedly 

many, if not most, grazers wandered to the hills, to the 

less grassy tundra, perhaps to escape flies. Like the 

modern elk (Murie, 1951, p. 241), perhaps the Pleistocene grazers ate less grass and more sedge, herbs, and 

other plants in summer, but in winter the grass, 

perhaps always their choice, became a necessity. Horses 

used by miners, trappers, and geologists years ago in 

Alaska subsisted on ~~native grasses" during the summer. But when the first frost came in the middle of 

September, the horse feed was ~~ruined"; the plants, 

mainly nongrass subsistence, lost their nutritional 

value (Brooks, 1953, p. 408). If this sort of seasonal 

change in environment also took place in early 

Holocene time, the grazers could live after a fashion 

away from the flood plain, especially in summer, but in 

the winter they probably searched for grass on the 

windswept flood plains where the snow blanket was 

thinnest. 

Therefore, the large population of grazers with fewer 

browsers and predators evidently thrived during the 

rigorous glacial climate in the nonforested areas of 

Alaska. In interglacial times forests reinvaded the valleys and low hills, and an environment not too different 

from that today must have existed in central Alaska. 

This tremendous reduction of their ideal habitat must 

have caused extensive stress for the grazers. Still, they 

did not become extinct in theY armouth(?) or Sangamon 

Interglaciations but died out at the end of the Wisconsinan Stage. 

If the grazers did not become extinct during the time 

of stress during interglacial times, it is unlikely that 

they would become extinct at the end of the Wisconsinan because of the loss of grassy habitat alone. No doubt 

an additional stress was added at this time, in the form 
CLIMATE 103 

of man. The combination of loss of ideal habitat and 

more efficient predation by man is therefore regarded as 

having caused the demise of the late Pleistocene grazers 

in Alaska, 10,000 years ago. 

MARINE VETEBRATE AND BIRD REMAINS 

To complete a summary of vertebrate remains from 

Quaternary deposits of Alaska, mention should be made 

of several finds that may lead to a detailed study. A 

walrus tusk and fish remains were recovered from the 

estuarine silt of Sangamon age (Pelukian transgression) at Nome (Hopkins and others, 1960, p. 52), and a 

metacarpal of a walrus (Odobenus) was found in late 

Pleistocene sediments from the south shore ofKuk Inlet 

on the north coast of Alaska (William Quaide, unpub. 

data). McCulloch dug a walrus humerus out of an old 

beach ridge 5-6 miles up the Kokolik River, northe.ast of 

Point Lay, and at one time he considered these to be 

deposits of the Pelukian transgression. Also, spinal 

disks from whales were collected by 0. W. Geist (oral 

commun., 1959) from the ~~muck" banks of the Inglutalik River (pl. 1), where it empties into Norton Bay 

at the base of Seward Peninsula. The first discovery of 

Steller's sea cow (Hydrodamalis) in place in Pleistocene 

deposits was made in beach sand and gravel thought to 

be interglacial, 35 m above present sea level on Amchitka, Aleutian Islands (Gard and others, 1972). The 

bone was dated at about 135,000 years old and is 

thought to be Sangamon in age. 

C. A. Repenning (written commun., Apr. 20, 1970) 

supplied the following identification of marine vertebrates of Pleistocene age collection by D. M. Hopkins in 

western Alaska from various Pleistocene horizons 

(table 10): 

P hoca vitalina(?) 

(? )Callorhinus sp. 

Pusa hispida 

E umetopias sp. 

In additon, F. H. Fay (written commun., Apr. 24, 

1970) stated that bones of walrus of Pleistocene age 

were recovered from Nelson and St. Lawrence Islands. 

Rare bones of birds of Pleistocene age were reported 

from the Fairbanks are (0. W. Geist, written commun., 

Dec. 5, 1950) and from the Arctic Coastal Plain. No 

informaion is available as to the exact age and 

identification. A unique study by Hoskin, Guthrie, and 

Hoffman (1970) demonstrated that bird gastroliths of 

Pleistocene age are perhaps widespread in Alaska. It 

would be well for workers in the Quaternary deposits of 

Alaska to be aware of the existence and the properties of 

these small gastroliths. 

SUMMARY 

Remains of Pleistocene mammals are widespread in 

Alaska, and large collections have been made. Although stratigraphic context is unknown for most of the 

early collections, good stratigraphic control is available 

for later and current work. Most of the remains are of 

Wisconsinan age, but there is a growing number of 

significant pre-Wisconsinan specimens. Only one good 

early Pleistocene collection is known. For a better understanding of mammal life in Alaska, more detailed 

knowledge is needed concerning early Pleistocene time 

and especially regarding the time between early Pleistocene and Illinoian time. Detailed meticulous sieving 

of the extensive silt deposits, especially in valley bottoms, should continue to yield valuable results. 

It is abundantly clear from the work in Alaska over 

the last 20 years that many taxa were present in North 

America earlier ' than generally recognized. Alaska 

perhaps will provide a significant link in the understanding of the time of Pleistocene vertebrate origins in 

North America. 

Remnants of frozen carcasses of Pleistocene mammals in permafrost are not rare in unglaciated Alaska, 

especially central Alaska. Geologic association plus 

radiocarbon dates indicate all carcasses are Wisconsinan in age and thus abolish the long-held idea that the 

animals must have lived only in interglacial times. All 

specimens show some sign of decay, and the animals 

were not frozen instantaneously by cataclysmic happenings. Specimens are available for detailed laboratory studies, and it is hoped that more work on the 

preserved specimens will be initiated by scientists in 

various disciplines. 

Studies of Alaska vertebrates shed light on extinction 

of mammals at the end of the Pleistocene. Although 

there is no complete agreement in regard to details, it is 

thought that the loss of grassy habitat and increased 

predation by man may have caused the extinction of the 

late Pleistocene grazers in Alaska 10,000 years ago. 

CLIMATE 

Quaternary climatic fluctuations in Alaska as elsewhere in the world were reponsible for formation and 

disappearance of glaciers and permafrost and changes 

in distribution of plants and animals. In this review the 

climatic changes of late Cenozoic time, mainly Quaternary, are based on available physical and biological 

data from glaciated and unglaciated areas. The causes 

of the climatic changes of the Quaternary are not dealt 

with here; they were recently summarized by Mitchell 

(1965; 1968). 

EVIDENCE FROM GLACIATED AREAS 

A parameter to be considered in evaluating past 

Quaternary climates in the glaciated areas, in addition 

to the existence and size of the glacial advanc~s, is the 
104 QUATERNARY GEOLOGY OF ALASKA 

past position of snowline and what it may mean in light 

of the vertical change of temperature of the atmosphere 

(lapse rate). A probable Pleistocene depression of mean 

annual or mean monthly air temperatures can be calculated by determining the difference in elevation between the present (fig. 11) and Pleistocene (fig. 12) 

snow lines and by multiplying this figure by the current 

average adiabatic lapse rate. Basic assumptions that 

must be made are that the Pleistocene lapse rate were 

similar to the present and that temperature decrease 

alone is responsible for lowering the snowline. Calculation of temperature depression from past snowline positions in Quaternary time has only been undertaken in 

Alaska in the last decade (Pewe and Burbank, 1960; 

Porter, 1966; Pewe and others, 1967; Pewe and others, 

1969). This technique is not applicable to climatic 

changes earlier than Illinoian time because cirques of 

pre-Illinoian age are not recognized. 

The temperature decrease calculated by this method 

is necessarily a minimum figure because snowline on 

even small valley glaciers is lower than cirque base. 

Probably more accurate is a calculation based on determining the position of the equilibrium line of past 

healthy glaciers using the accumulation area ratio 

(Porter, 1968, 1970). This technique has not yet been 

applied to Alaska except at Indian Mountain (R. D. 

Reger and T. L. Pewe, unpub. data, 1974). 

EVIDENCE FROM UNGLACIATED AREAS 

Geologic features useful in detecting Quaternary 

climatic changes in a periglacial area are frost features 

such as permafrost, ice wedges, altiplanation terraces, 

solifluction deposits, and patterned ground, and other 

features. The use of such features in interpretation of 

Quaternary climates in temperate latitudes is widespread (Wright, 1961); however, only recently have 

quantitative data become available to permit a more 

thorough understanding of the periglacial environment. 

The mere presence or absence of permafrost as a 

climatic indicator is actually less valuable in Alaska 

than in temperate latitudes because permafrost is still 

present in most of Alaska and is actively forming in 

certain areas where the mean annual air temperature is 

-1 oc or colder. The presence or absence of ice wedges is 

more valuable in Alaska than in temperate latitudes 

because of the different types of ice wedges still present, 

such as active, inactive, and ice wedge pseudomorphs. 

Ice wedges, or foliated ice masses, constitute the critical parameter in permafrost that is of the most value in 

reconstruction of past climates. From the earlier discussion of permafrost, it is apparent that ice wedges readily 

grow in regions where the mean annual air temperature is colder than -6oC to -8°C. Ice wedges may exist 

inactively for thousands of years in areas where the 

mean annual air tern perature is between -2° and - 6°C. 

Of course, it is always possibile that cold microclimatic 

conditions may occur so that a few small local ice 

wedges could grow in a broad area of ((inactive" ice 

wedges. 

Other geologic features used as climatic indicators 

are loess, sand dunes, and ventifacts. In Alaska these 

features (figs. 15, 16, 17) do not necessarily indicate 

greater aridity or wind action than at present, nor are 

they in themselves indications of a colder climate. It is 

felt that widespread loess and sand dune deposits of 

Quaternary age are mainly indicators of much larger 

source areas of silt and sand in the past. All these 

features, at least in central Alaska, are associated with 

extensive glaciations and, therefore, form with the 

changes of the climate. 

Biogeographic evidences of past climates are the 

changes in the position of tree line and floral communities (from pollen analyses) and the changes in environment and distribution of marine and terrestrial 

fauna. 

LATE TERTIARY 

As a generalization, it is believed that the climate of 

late Tertiary time in Alaska was relatively equable and 

not intensely cold, although glaciers were present in 

Alaska 1{}-13 m.y. ago (table 1). 

Glaciation was probably extensive in the mountains 

facing the Gulf of Alaska. Ice pushed to the interior from 

the Wrangell and St. Elias Mountains (Denton and 

Armstrong, 1969). Ice reached the sea to the south and 

sporadically for at least 10 m.y. repeatedly formed shelf 

ice and discharged icebergs into the ocean (Taliaferro, 

1932; Miller, 1953a, 1957; Plafker, 1971; Bandy and 

others, 1969; Kent and others, 1971; Scholl and others, 

1971). A record of the fauna and the glacial deposits 

exists in the Yakataga Formation and shows that the 

adjacent sea was about 10°C colder than now as indicated by the presence of the cold-water planktonic 

foraminifer Turborotalia pachyderma (Bandy and 

others, 1969). Plafker (written commun., Apr. 21, 1970) 

believed the molluscan and foraminiferal faunas indicate a decrease of surface-water temperature of 

10°-15°C in early Yakataga time. 

The Y aka tag a Formation is in an extremely rugged 

(pl. 1) and tectonically active region which today receives exceptionally heavy precipitation (upwards of 

250 em per year at sea level) (fig. 2). Despite a relatively 

mild climate, it is one of the most heavily glaciated 

areas in Alaska, and many glaciers reach sea level, 

invading the temperate Sitka spruce and hemlock 

forest that fringes the shore. The presence in this area of 

late Tertiary deposits of glacial origin probably indicates that relief was high, rainfall heavy, and the climate cool-temperate, much like the present; and not · 

intensely cold. 
CLIMATE 105 

Leaves of beech (Fagus sp.) were found with an early 

Pliocene mollusk fauna in the fine-grained beds 

interstratified with conglomeratic sandy mudstone at 

Cenotaph Island in Lituya Bay, indicating that land 

climates at sea level were somewhat milder than at 

present and that the glaciers probably invaded a forest 

of beech trees (Hopkins, 1972). 

From the Arctic Basin comes information regarding 

late Tertiary climate based on interpretation of fauna 

and sediments in deep cores. Evidence for glaciation 

and cooling, at least in the adjacent highlands 4-6 m.y. 

ago, is indicated by ice-rafted pebbles. This does not 

indicate ice-pack conditions or especially cold waters. 

According to Hopkins (1972), the Arctic Ocean could not 

have been frozen or even been very cold about 3.5 m.y. 

ago, because at that time Pacific mollusks invaded the 

North Atlantic (Beringian transgression) (table 1). He 

further stated that the recent discovery ofTurritella in 

Pliocene marine beds offshore at Nome indicates temperate shelf waters during Pliocene time. Later, icerafting increased and pack ice cover occurred (table 1). 

The forest vegetation of spruce, birch, pine, and hemlock in northern Seward Peninsula 5. 7 m.y. ago (Hopkins and others, 1971) (table 1) indicates an environment similar to southeastern Alaska and coastal 

British Columbia rather than the Arctic climate of 

today. In general, flora of Beringian times (table 1) 

indicates that the climate of western and northern 

Alaska was considerably warmer than at present (Hopkins, 1967a, p. 61). The tundra cover and associated 

cooler climate probably did not arise in the northern 

Seward Peninsula until early Pleistocene time. 

EARLY PLEISTOCENE 

The early and middle Pleistocene of Alaska record 

glacial episodes, interglaciations, and major changes in 

climate with corresponding modification of permafrost 

and other periglacial features and changes in the distribution of the flora and fauna of the sea and land. In 

this report, climatic changes of pre-Yarmouth time are 

labeled as early and middle Pleistocene in age, and 

provincial names are used. 

A cold episode of early and middle Pleistocene age is 

recorded in many areas of Alaska. The cooling of the 

climate resulted in the Iron Creek Glaciation on Seward 

Peninsula, deposits of which underlie beds of the Anvilian transgression and are thought by Hopkins to be 

1.0±0.5 m.y. old. The transgression is less than 1.8 m.y. 

old but more than 700,000 years old. Glacial advances 

elsewhere in Alaska around this time or before may be 

the Browne Glaciation (Wahrhaftig, 1958) in the 

Alaska Range, thought to be more than 2.7 m.y. old 

(Wahrhaftig, oral commun., July 4, 1970), and the 

Mount Susitna Glaciation in Cook Inlet (Karlstrom, 

1964). 

An excellent record of tundra biota is reported from 

Cape Deceit on the south shore of Kotzebue Sound 

(Guthrie and Matthews, 1971). Ice wedge 

pseudomorphs are reported at this locality, and Hopkins (1972) believed they represent a permafrost period 

of 1.0 ±0.5 m.y. ago. 

In valleys of small streams and rivers in central 

Alaska, an angular coarse auriferous gravel of great 

antiquity is preserved on benches (fig. 20) and represents a drainage pattern slightly different from that of 

the present. In places, the material grades laterally up 

slopes into solifluction deposits. The gravel is the result 

of the accumulation of frost-rived local debris produced 

in a rigorous climate. The solifluction layer is widespread in central Alaska and contains well-developed 

ice wedge pseudomorphs (fig. 33). They are thought to 

be at least 1 m.y. old inasmuch as they represent the 

older of two permafrost periods, both of which predate 

the Illinoian glaciation. As outlined earlier, ice wedges 

indicate that the mean annual air temperature was 

colder than -6° to -8°C. 

Data regarding temperature of sea water in early 

Pleistocene time are rare, but mollusks (particularly 

Portlandia) dredged from rocks of early Pleistocene age 

in the southern Bering Sea are indicative of water 

temperatures that were colder than at present (Hopkins 

and others, 1969). (Portlandia is not known to occur 

south of the Bering Strait at the present time.) 

After the early Pleistocene cold period(s), a warmer 

period termed ((the Anvilian transgression" occurred. 

Hopkins (1967b) stated that mollusks indicate a 

warmer sea water temperature than in the modern Bering and Chukchi Seas as well as the Arctic Ocean (Hopkins, 1972). For example,Naticajanthostoma was found 

in Anvilian sediments near Nome and Skull Cliff in 

northern Alaska but now is limited to waters adjoining 

Japan. During the warmer part of the Anvilian transgression, winter ice probably did not reach Nome and 

may not have reached the Arctic coast of Alaska. 

A warm episode also occurred in central Alaska, causing the glaciers to withdraw and permafrost with ice 

wedges to thaw. The ice wedges were replaced with 

windblown sand that filtered down from the overlying 

sand dunes forming ice wedge pseudomorphs (fig. 33). 

The lowering of the permafrost table and disappearance 

of the ice wedges indicate that the mean annual air 

temperature was at least warmer than 0°C. From both 

sea and land, then, comes strong evidence of a major 

warm interglacial period perhaps 1 m.y. ago. 

MIDDLE PLEISTOCENE 

In several parts of Alaska there is evidence of two or 

more Pleistocene cold periods of pre-Illinoian age. The 

exact stratigraphic positions are unknown, but one or 

two of the cold periods lie in what may roughly be called 
106 QUATERNARY GEOLOGY OF ALASKA 

middle Pleistocene time. The Dry Creek Glaciation in 

the Alaska Range (Wahrhaftig, 1958) and the Caribou 

Hills Glaciation in Cook Inlet (Karlstrom, 1964) are not 

the earliest recorded glaciations in the respective areas, 

yet they are pre-Illinoian. In many other Alaskan 

localities, glacial deposits indicate a major cooling of the 

climate sometime in pre-Illinoian, perhaps in middle 

Pleistocene time (table 2). Pack ice, for example, appeared in the Arctic Ocean at least 700,000 years ago 

(Herman, 1970; Hunkins and others 1971). 

In central Alaska, inactive solifluction deposits and 

altiplanation terraces record a major cold period. The 

upper of the two well-developed inactive solifluction 

layers on the campus of the University of Alaska (fig. 

33) is probably middle Pleistocene in age. The inactive 

solifluction layer lies at an elevation of 150 m and is 

covered by loess of Illinoian and Wisconsinan age. Active solifluction occurs in central Alaska today at an 

elevation of 1,000 m. 

Still preserved at elevations of 260--900 m are relict 

altiplanation terraces now covered by loess of Illinoian 

and Wisconsinan age. Well-developed but inactive altiplanation terraces of Wisconsinan age exist at 1,600 m 

near Fairbanks. A rigorous climate is necessary to form 

altiplanation terraces. Barring major tectonic movement, the low-level inactive solifluction deposits and 

relict altiplanation terraces at Fairbanks indicate that 

the climate was then much more rigorous than in any 

later Quaternary time (Pewe, 1970b). 

The last of two or perhaps three periods of deposition 

of coarse, angular, local, auriferous gravel in creeks of 

central Alaska is middle Pleistocene in age (fig. 20). It is 

felt that the gravel is the debris shed from the hills by 

solifluction during the time that the ancient altiplanation terraces were cut (Pewe, 1970b) and, therefore, is 

additional evidence of a rigorous cold period. 

In addition to the cold periods recorded in middle 

Pleistocene time, Hopkins (1967b) has evidence of an 

interglacial period, the Einahnuhtan transgression of 

between 250,000 and 50,000 years ago. The marine 

fauna indicates the temperature of the water was about 

the same as at present; no information is available on 

air temperature. According to Hopkins (1967b, p. 72), 

the transgression was preceded by a severe cold interval, because frost-disturbed beds under the 

Einahnuhtan beds on St. Paul Island indicate permafrost at low altitudes on the island. The warm interval 

cannot be directly associated with the cold intervals 

because of the lack of dating of the well-documented 

cold intervals of the middle Pleistocene in Alaska. 

YARMOUTH(?) 

Events associated with a climatic warming just prior 

to Illinoian time are treated here as Yarmouth(?) in age. 

Correlations with central United States and Europe 

time equivalents are probable, although not proved. 

The glacial record at various places in Alaska indicates 

that the immediate pre-Illinoian interglacial episode 

was an important warming period; however, more detailed information is available from western and central Alaska. 

In the Bering and Chukchi Sea areas, deposits from 

the marine transgression of Yarmouth time (termed 

((Kotzebuan transgression" by Hopkins, 1965, 1967a) 

contain a molluscan fauna indicative of a water temperature the same as that now at Amchitka and St. 

Lawrence Islands. However, deposits of the Kotzebuan 

transgression around the shores of Kotzebue Sound and 

along the Siberian coast contain high-Arctic molluscan 

and foraminiferal faunas indicative of very cold water 

(Hopkins, 1972). McCulloch, Taylor, and Rubin (1965) 

referred to this transgression as Yarmouth in age near 

Kotzebue. Later, McCulloch (1967, p. 102) labeled the 

transgression as pre(?)-Illinoian on the basis of 

Th230fU238 dates of 170,000 and 175,000 years (Blanchard, 1963). These dates may be suspect (Plafker, 

1971) on the basis of the Th230fU238 dates on shells by 

Blanchard from Middleton Island. Hopkins (1972) later 

stated that the marine beds at South Bight on Amchitka 

Island are of a Kotzebuan age, and uranium-thorium 

age determinations on bones and shells there are about 

130,000 years old (Gard and others, 1972). 

A study of pollen from the long core from Imuruk 

Lake (fig. 40) led Colinvaux (1964a, 1967a) to believe 

that the vegetation in central Seward Peninsula was 

similar to that now and that tree line was not too far 

distant. The summers were longer and warmer than 

those now. 

From interior Alaska comes a record of a warmer 

climate, especially summers, as indicated by welldeveloped forests and thawing of permafrost and ice 

wedges. Underneath loess of Illinoian age in several 

exposures in the Fairbanks area is a well-developed 

forest bed, the Dawson Cut Formation (figs. 29, 41) 

(Pewe, 1952a, 1975). 

It is thought that with warmer summers tree line rose 

and forests were widespread. Permafrost was gone, and 

loess deposition slowed, as suggested by geochemical 

analyses of silt of the forest bed (see p. 59; fig. 29). 

Thawing of permafrost indicates that the mean annual 

air temperature had warmed to at least ooc or probably 

a few degrees warmer. Presence of ice wedge 

pseudomorphs in solifluction deposits at Fairbanks 

(fig. 33) and near Shaw Creek in central Alaska indicates warming of the climate either in Yarmouth time 

or earlier (Pewe, 1965b, fig. 4-22). 
CLIMATE 107 

ILLINOIAN 

EVIDENCE FROM GLACIATED AREAS 

Extensive glacial advances during Illinoian time indicate a colder or wetter climate than now and of long 

duration. On the basis of cirque floors of Illinoian time, 

snowline was about 500--600 m lower than now and 

150--250 m lower than its position during Wisconsinan 

time in the southwestern Seward Peninsula (Pewe and 

others, 1967). The rising of snowline to the east and 

north (figs. 11, 12) indicates the source of moisture was 

to the west and south and the climate became drier and 

more continental toward the interior of the State. R. 

Reger and V. Reger (unpub. data, 1971) calculated the 

mean July lapse rate for nearby Nome from 250 to 3,600 

m elevation: 0.49°C per 100 m. On the .basis of this 

vertical air temperature gradient and the 500-m lowering of snowline, the mean July air temperature in Illinoian time at Nome was 7.4°C, 2.4°C lower than today. 

By this method, mean July temperature at Indian 

Mountain near Hughes was probably at least 3.3°C 

lower than today. AB previously noted, however, the 

amount of temperature drop calculated from cirque 

floor levels is a minimum figure. 

EVIDENCE FROM UNGLACIATED AREAS 

Abundant evidence indicates the presence of permafrost and ice wedges during Illinoian time in both central (Pewe, 1952a) and far western Alaska (McCulloch 

and others, 1965). These features reflect a rigorous 

periglacial climate with a mean annual air temperature 

of at least -7°C, 2°-4°C colder than the present mean 

annual air temperature in these localities. 

Undoubtedly, periglacial frost features other than 

permafrost and ice wedges were present in unglaciated 

areas during Illinoian time, but as yet, none are recognized, except perhaps the rubble sheets on Jumbo Dome 

(Wahrhaftig, 1949). No quantitative data are available 

on the climate needed to produce the rubble sheets on 

Jumbo Dome; however, a rigorous climate must have 

existed. 

Thick loess deposits of Illinoian age are widespread in 

central and western Alaska, indicating widespread glacial advances and extensive accompanying vegetationfree flood plains that existed a long time. The loess 

indicates great source areas and not necessarily higher 

winds or greater aridity. Silt deposits of Illinoian age in 

Fairbanks (fig. 20) have a conspicuous unconformity in 

the middle, which may mean a change in rate of deposition and perhaps in climate. 

Biogeographical evidence to support the rigorous 

climate in Illinoian time is available but difficult to 

quantify. For the Imuruk Lake area, Colinvaux (1962) 

showed a colder climate than now, with an Arctic grass 

tundra and little or no alder and some dwarf birch; the 

tree line was not very close. In the Fairbanks area, tree 

line was lowered 600 m, and trees were sparse as the 

result of cooler and shorter summers (see p. 84). 

In summary, the climatic conditions of at least central and western Alaska were rigorous and thought to 

be colder and of longer duration than during Wisconsinan time on the basis of more extensive glaciation and 

lower snowline. Ice wedge studies indicate that the 

mean annual air temperature in the central and western part of the State was at least -7°C, 2°-4°C colder 

than now. Snowline studies on the basis of cirque floor 

elevations suggest a depression of mean July temperature of 2.4 oc in the far west. Reconstruction of forest 

distribution also indicates shorter and colder summers. 

SANGAMON 

During the Sangamon interval, the climate was 

warmer than now. Marine molluscan and fish fossils 

indicate that water temperatures off western and 

northern Alaska also were warmer in Sangamon time 

(Pelukian transgression of Hopkins) than at present 

(Hopkins, 1965). Plant remains interbedded with 

marine sediments indicate that the present forests of 

western Alaska extended 50--80 km more to the west, 

which suggests that the summers were appreciably 

warmer and longer than at present in that part of the 

State. This was also suggested by Colinvaux (1962) 

from his work at Imuruk Lake. He stated that the vegetation of Sangamon time was a sage-alder tundra similar to present conditions and tree line was nearby. 

McCulloch, Taylor, and Rubin (1965) also recorded 

westward advance of forests in Sangamon time into 

areas now tundra covered near Kotzebue. Hopkins 

(1972) cited R. L. Detterman to support the suggestion 

that spruce forest extended into the Arctic drainage of 

the Brooks Range in regions now supporting only shrub 

tundra. 

The exposures near Fairbanks of white sprucebirch-aspen forest beds ofSangamon age indicate warm 

summers and severe winters. Summers were considerably warmer than in Illinoian and Wisconsinan tirne. 

However, vegetation alone does not reveal whether the 

mean summer air temperature was warmer than now. 

From far western and central Alaska more quantitative paleoclimatic information is obtained from the 

study of past permafrost. The presence of ice wedge 

casts in now perennially frozen sediments of Illinoian 

age in both western (McCulloch and others, 1965; Hopkins, unpub. data) and central Alaska (Pewe, unpub. 

data, 1952) indicates that during the interval between 

Illinoian and Wisconsinan time the climate ameliora-
108 QUATERNARY GEOLOGY OF ALASKA 

ted to give a mean annual air temperature that was 

warmer than 0°C, thereby causing the ice wedges to 

melt. 

The geochemical studies of perennially frozen sediments at Fairbanks (p. 59; fig. 29) (leaching of salts, as 

well as other evidence of ground-water movement 

through now perennially frozen sediments) further 

support the belief that most of or all the permafrost in 

central Alaska thawed in Sangamon time, and therefore, the mean annual air temperature was warmer 

than ooc for a considerable length of time. Thawing of 

permafrost would necessarily thaw mammal carcasses 

preserved in the frozen ground; no carcasses of preWisconsinan age are known, thereby strengthening the 

concept that permafrost perhaps thawed entirely in 

central Alaska in Sangamon time. 

Formation of a weathering profile 3 m thick on the 

drift of the Nome River Glaciation (Illinoian in age) (p. 

20) and on loess near Kotzebue (McCulloch and others, 

1965) on the Seward Peninsula indicates that the permafrost table was lower or that permafrost was absent. 

On the north shore of Eschscholtz Bay during Sangamon time, there may have been a warm period followed 

by a cold period (regarded as pre-Wisconsinan in age) 

with formation of ice wedges, and then a return to a 

warm climate (Hopkins, 1965). 

The climate ofSangamon time in central and western 

Alaska was warmer than now to allow permafrost to 

thaw and had longer and warmer summers to permit 

rise of tree line and further extension of it to the west 

and north. The mean July temperature in Sang am on 

time, for example, probably was warmer than the present mean July temperature of9.9°C at Nome andl5.5°C 

at Fairbanks. 

WISCONSINAN 

The Wisconsinan Stage in Alaska represents the 

latest major cold phase in Quaternary time, as it does 

elsewhere; however, in this region work has not progressed in sufficient detail to divide climatic 

fluctuations of Wisconsinan time, except perhaps in a 

few areas. Therefore, all discussions of climatic conditions in Wisconsinan time will mean ((Wisconsinan undifferentiated" unless otherwise indicated. 

EVIDENCE FROM GLACIATED AREAS 

A comparison of snowline maps of the present and 

Wisconsinan time for Alaska reveals quite strikingly 

the similarity of pattern of the isolines and of wind and 

moisture sources during these two times. This pattern 

and the close parallelism of modern and Wisconsinan 

snow lines strongly suggests that there probably was no 

increase in precipitation to produce Wisconsinan 

glaciers, but rather that glaciation probably was caused 

by a decrease in mean summer temperatures and increase in summer cloudiness which resulted in decreased snow and ice ablation. 

Wisconsinan July mean temperatures were calculated from present lapse rate and the position of snowline in Wisconsinan time in many parts of the world 

(Charlesworth, 1957, p. 645). Values for Wisconsinan 

July mean temperatures range from 3° to 12°C. However, snowline was perhaps a bit lower than cirque 

floors (R. D. Reger and T. L. Pewe, unpub. data, 1974), 

especially for all but cirque glaciers. Nevertheless, elevation of cirque floors, an easily obtainable figure, is 

used throughout the world and therefore is used in this 

report. It may eventually be possible to calculate the 

position of snowline in Alaska from equilibrium lines 

(the level on a glacier where the net balance equals zero, 

and the accumulation equals ablation) on past glaciers. 

This should permit more accurate calculations of past 

temperature changes. 

Calculations also assume that for a given locality the 

present lapse rate is the same as in Wisconsinan time. 

R. Reger and V. Reger (unpub. data, 1971) showed that 

this is probably not true. Especially in Alaska, proximity to the coast should probably be taken into consideration (R.D. Reger and T. L. Pewe, unpub. data, 1974). 

Table 14 shows that the lapse rate for coastal stations is 

much lower than for those in the interior part of the 

State. During Wisconsinan time, when the strait area 

was dry and stations such as Nome and Kotzebue were 

inland, the lapse rate was probably higher than now. 

However, the amount of difference is not known, and in 

this report modern lapse rate will be used; only 

minimum temperature changes are thus recorded. 

A traverse from the west coast of Alaska to the interior reveals that snowline dropped more in the central 

part of the State than near the moisture-rich coasts 

(figs. 8, 9, 11, 12). Modern lapse rates also increase from 

coastal stations toward the interior. Therefore, the difference between Wisconsinan and modern mean July 

temperatures increases from the coast inland (table 14). 

In Wisconsinan time, the mean July air temperatures 

at Nome and Kotzebue were soc and 9.2°C, respectively, 

drops of 1.9oand 2.1 °C. In the interior, however, Fairbanks and Northway show minimum drops of 4°C and 

4.8°C for a mean July air temperature of11.5oand 9.9°C 

respectively, in Wisconsinan times. At Indian Mountain near Hughes, the drop in mean July temperature 

was 2.7°C for early Wisconsinan time from calculations 

of past snowline on the basis of cirque floors. Calculations using the equilibrium line give a drop of mean 

July temperature of 3.9°C at Indian Mountain. Evidence of a middle Wisconsinan climatic change is the 

withdrawal of glaciers and transgression of the sea at 

this time. 
CLIMATE 109 

TABLE 14.--Present-day and Wisconsinan mean July temperatures of selected stations in Alaska calculated from present lapse rate and 

estimated change of snowline based OlJ. elevation of Wisconsinan cirque floors 

Station 

Nome -------------------- Kotzebue ______ _____ _____ _ _ 

Utopia -------------------- Fairbanks ---------------- Northway ---------------- McGrath ------------------ Anchorage __ ________ _____ _ Anaktuvuk Pass7 __ __ _____ _ 

'Estimated from figures 11 , 12. 

Elevation (m ) 

5 

3 330 

150 

522 

102 

38 700 

:~~~ ·. :.eW:a~h~r ~!:~~ l9l~f.b . data, 1971). 

4R. D. Reger and T. L. Pewe (unpub. data, 1974). 5Early Wisconsinan. 

Estimated 

lowering of snowline (m)' 

400 

400 

450 

600 

600 

450 

300 

8 700 

EVIDENCE FROM UNGLACIATED AREAS 

Present July 

lapse rate per 100m2 

0.49 

.54 

.61 

.67 

.81 

.62 

.58 

.59 

Permafrost was more extensive during Wisconsinan 

time than now. Deep-lying relics of Wisconsinan permafrost are present in the glacial outwash sediments 

near Big Delta (Pewe and Holmes, 1964; Pewe and 

others, 1969), as well as along the south border of the 

permafrost area in Alaska (fig. 22). Such information 

means only that the mean annual air temperature was 

-1 oc or colder. Along the south border of the State this 

indicates a rise in the mean annual air temperature of a 

few degrees centigrade since Wisconsinan time. 

In northern and northwestern Alaska, ice wedges 

were actively growing in Wisconsinan time and still 

are. All that can be deduced from this information is 

that the climate there in Wisconsinan time was at least 

as cold and snow cover as thin as now. In central Alaska, 

however, inactive ice wedges are widespread. If large, 

typical ice wedges such as are present require a mean 

annual air temperature of -6° to -soc or colder to form, 

then the mean annual air temperature near Fairbanks, 

for example, would have to have been at least 3°-4°C 

colder than at present. The mean annual air temperature of the Fairbanks area thus must have been at least 

-7°C in Wisconsinan time. 

Many of the large deep-lying ice wedges in the Fairbanks area have flat tops, indicative of downward thawing of permafrost and ice wedges. This thawing was 

dated at more than 3S,OOO years old (Sellmann, 1967) 

and is thought to represent a short middle Wisconsinan, 

or earlier, warm period with a mean annual air temperature of more than 0°C. 

If the large-scale polygonal ground in the Bristol Bay 

area (Hopkins, Karlstrom, and others, 1955, pl. 39) is 

the result of ice wedge growth, as believed by the writer, 

the Wisconsinan mean annual air temperature in that 

area was at least -6° to -S°C, S0-10°C colder than at 

present. 

Preliminary results of work by R. D. Reger and T. L. 

Elevation of interval of 

lapse rate (m) 

250--3,600 

750--3,700 500--3,600 

500--3,600 1,250--3,700 

250--3,700 

250--3,700 

1,475-3,000 

Present 

July mean 

temperature3 

(oC) 

9.9 

11.3 4 13.8 15.5 2 14.7 2 14.5 

13.8 10.3 

Wisconsinan 

mean July 

temperature 

(oC ) 

8.0 

9.2 5 11.1 

11.5 

9.9 11.6 

12.1 9 6.5 

Difference between present and Wisconsinan 

mean July temperature 

(oC) 

-1.9 

-2.1 L2.7 

-4.0 

-4.8 

-2.9 

-1.74 

-3.8 

6 A figure of3.9°C was obtained by R. D. Reger and T. L. Pewe (unpub. data, 1974) calculating 

early Wisconsinan snowline from the equilibrium line of the past glacier. 7From Porter (1966, p. 93). 8Modern snowline placed above existing glaciers by Porter. 9Classical Wisconsinan. 

Pewe (unpub. data, 1974) on paleoclimatic implications 

of altiplanation terraces indicate that at an elevation of 

S40 m on Indian Mountain near Hughes in western 

Alaska, the mea~ July temperature was at least as cold 

as about 5° or 6°C when the terraces were forming in 

Wisconsinan time. By extrapolation, it was at least that 

cold in July in the highlands of the Yukon-Tanana 

Upland, in the Amphitheater Mountains 30 miles west 

of Paxson, in the highlands of the Seward Peninsula, 

and elsewhere where altiplanation terraces formed during Wisconsinan time. 

Other periglacial frost features, such as solifluction 

deposits, rubble sheets, rock glaciers, and patterned 

ground, are present in Alaska, both in the active and 

inactive form, but are less quantitative indicators of 

Wisconsinan climatic changes than ice wedges, altiplanation terraces, or permafrost. Throughout central and 

western Alaska a colder climate in the Wisconsinan 

glacial phase is indicated by the lower altitudinal limit 

of solifluction (fig. S) (T. L. Pewe, unpub. data, 1964), 

rubble sheets (Wahrhaftig, 1949; Pewe, 1961c), and 

other frost features at that time. 

There has been little investigation of paleowinds, or 

winds of Wisconsinan time, in Alaska similar to studies 

that have been done in Europe. Except for one or two 

local references, no critical work has been done, and in 

fact some misinterpretations of the paleoenvironment 

of the eolian sand and loess distribution are known. To 

produce the widespread, now stabilized sand dunes, it 

was necessary either to have had more widespread and 

more powerful winds than exist now or to create a much 

more widespread source of sand and silt. To produce a 

greater source, it is necessary to remove much of the 

vegetation. This can be done by creating more arid 

conditions, by dropping the water table, or by greatly 

increasing the size and number of wide, braided flood 

plains and outwash fans of glacial streams. Withdrawal 

of the sea from shelving shores would create larger 

sandy beaches than now exist. Both the increased size 
110 QUATERNARY GEOLOGY OF ALASKA 

and number of braided streams as well as the lowering 

of the sea level took place as glaciation occurred in 

Wisconsinan time in Alaska. For example, Hopkins 

(1972) stated that the sheet of dune sand and loess 

covering some 12,000 km2 of northwestern Seward 

Peninsula is evidently derived largely from a blanket of 

marine sand left exposed beneath the present-day 

Chukchi Sea. 

Until detailed work reveals new facts, the model the 

writer suggests for paleowinds is that the extensive 

eolian sand and loess of Wisconsinan age do not indicate 

former greater aridity of any substantial change in 

amount or direction of winds but instead indicate an 

extensive increase in poorly vegetated or treeless 

gravelly-braided flood plains and outwash fans and 

plains throughout Alaska. 

Comparison of modern and Wisconsinan snowline 

maps (figs. 111 12) suggests that there was no increase in 

precipitation in Wisconsinan time and that the major 

wind directions and sources of moisture were probably 

the same. Grass and some sage (Artemisia) perhaps 

were abundant on the well-drained, more extensive active flood plains, outwash fans, and outwash plains. 

These broad generally fiat areas were favored by great 

herds of grazers such as the bison, mammoth, and horse. 

The writer believes that grazers, grasslands, and xeric 

vegetation can be explained by the great increase of the 

treeless flood plains, outwash plains, and active sand 

dune areas in Wisconsinan time, and it is not necessary 

to call on greater general aridity throughout the entire 

unglaciated part of the State. The rolling lower hillslopes and small creek bottoms were probably boggy, 

perhaps more so than today, because the permafrost 

level was higher in Wisconsinan time and drainage was 

even poorer than now. Peat layers are common in the 

frozen retransported loess in valley bottoms, contrary to 

suggestions by Hopkins (1972). 

In the pioneer study of the oriented lakes of the North 

Slope of Alaska, Black and Barksdale (1949) suggested 

that the lakes were oriented by winds blowing northwest (or southeast), parallel to the long axis of the lakes. 

This direction is 90° from the present northeast winds 

and from the wind direction associated with the modern 

and Wisconsinan sand dunes. Later studies by Carson 

and Hussey (1959, 1960a, b, 1962, 1963) showed that 

the lakes were, and still are, oriented by winds from the 

northeast. 

BIOGEOGRAPHICAL EVIDENCE 

It has been shown that the position of tree line in 

Wisconsinan time was 450-600 m lower in central 

Alaska and had withdrawn eastward of its present position on the Seward Peninsula. Tundra replaced the 

forests. Such changes indicate a more rigorous climate 

in Wisconsinan time than now. But inasmuch as the 

forest boundary is probably independent of the severity 

of winter temperatures, such shifts in tree line indicate 

changes in summer climate. Summers were shorter and 

cooler than now. Hopkins (1959a) showed that the 

spruce forest in Alaska is restricted to areas that have 

at least 90 ((degree days" per year when the temperature 

reaches or exceeds 10°C. ((Degree days" above 10°C was 

calculated by multiplying the amount by which the 

mean monthly temperature of the warmer months exceeds 1 ooc by the number of days in these warm 

months. In Fairbanks, for example, today the mean 

annual number of ((degree days" above 10°C is 440 

(Hopkins, 1959a, table 1). During much of the Wisconsinan interval, at least, the hills in the Fairbanks area 

were forest free; therefore, it is assumed that the 

number of mean annual degree days above 10°C was 

less than 90. There were a few spruce in the valleys (fig. 

42), and the valley bottoms probably were at the 

threshold value of 90 ((degree days" above 10°C; thus, 

Fairbanks probably had a summer climate similar to 

Moses Point or Council on the Seward Peninsula today. 

Terrestrial mammal remains also provide information about Pleistocene climates. As shown, all forms 

known from Quaternary deposits could have lived 

under severe conditions; many live today in central 

Alaska. Forms such as the bison, mammoth, and horse 

were grazers and thus indicate more widespread grasslands. Mountain sheep, ground squirrels, and lemmings 

live today in tundra above tree line. These species indicate the reduction of forest and the concurrent shorter, 

colder summers. The Wisconsinan frozen carcasses suggest that permafrost has existed since the time of the 

animal's death. The mean annual air temperature must 

therefore have been colder than -1 oc since their death, 

except for short warm periods which did not greatly 

affect the permafrost. Further, the presence of certain 

ground beetles (Matthews, 1968b) in silts near Fairbanks indicates a tundra environment and colder, shorter summers in Wisconsinan time. 

SUMMARY 

Many lines of evidence converge to indicate that 

summers were colder and cloudier in Wisconsinan time. 

Lower snowline suggests that mean July temperature 

dropped by 3° or 4°C, and the distribution of tree line, 

mammals, and beetles suggests colder summers also. 

Permafrost, especially ice wedges, demonstrates that 

the mean annual air temperature was several degrees 

colder in many parts of the State. A mean annual air 

temperature of at least ..,...6o to -8°C is indicated for 

central Alaska and perhaps even as far south as Bristol 

Bay. 

Although active sand dunes and loess deposits were 
CLIMATE 111 

widespread in Wisconsinan time, there is no good 

evidence to prove higher wind velocities or greater aridity. 

HOLOCENE 

With the amelioration of climate since Wisconsinan 

time, the massive glaciers have withdrawn, and snowline has risen. The climatic record in Alaska does not 

illustrate a simple warming since Wisconsinan time but 

an oscillation of climate. Throughout the State, the 

rather abrupt warming that began 10,000 years ago is 

reflected in a dramatic change in vegetation, permafrost, and glaciers. In some areas the Holocene warming 

peaked in a thermal maximum (hypsithermal interval) 

from about 7,500 to 3,500 years ago; in others, the 

warming maximum was recorded earlier. The thermal 

maximum of 7,500-3,500 years ago is not only recorded 

as a time of glacial minimum, and thus a warm period, 

but also is well inscribed in the botanical record. In the 

Brooks Range and near Umiat on the north side of the 

range, the slight warming at about 6,000 years ago may 

have been responsible for an alder maximum recorded 

(Livingstone, 1955, 1957). The warming is further supported by a date of 5,600± 230 years from frozen alder 

remains in soils north of the Brooks Range (Tedrow and 

Walton, 1964). To Tedrow and Walton, the fossils indicate that the climate was warmer than now; they believe that alder does not grow in the area today. However, R. L. Detterman reported (written commun., Dec. 

10, 1970) that there are good stands of alder today in the 

Colville River valley near Umiat. Perhaps because of an 

incomplete record, no thermal maximum is documented 

in the pollen record from Barrow. 

On the Alaskan Peninsula (Heusser, 1963a) and in 

south-central and southeastern Alaska, detailed work 

by Heusser (1960) indicates a cool moist period from 

about 10,000 to 8,000 years ago, followed by a warm and 

drier thermal maximum period of 8,000-3,500 years 

ago (table 3). On St. Lawrence Island (Colinvaux, 

1967b) and at the MacKenzie River delta (Ritchie and 

Hare, 1971), pollen studies indicate that the thermal 

maximum peaked at about 5,000 years B.P. 

A detailed glacial record of Anaktuvuk Pass in the 

Brooks Range suggests that a period of maximum 

warmth somewhere between 6,260 and 2,800 years ago, 

but no quantitative data as to the degree of warming are 

available (Porter, 1966, fig. 22). 

In parts of Alaska the classic postglacial thermal 

maximum (hypsithermal interval) is not recognized. 

Instead, an earlier dramatic warming and vegetation 

change are apparent, or the vegetation record shows 

only gradual warming and forest establishment to the 

present. In coastal Alaska, from Nome northeastward 

to at least the Sagavanirktok River,. a warming is recorded 10,000-8,000 years ago, during which the climate became milder than at any other time since the 

last interglacial interval (Hopkins, 1972). Summers 

were considerably warmer, but winters may have been 

as severe as now. 

Beaver-gnawed wood 9,400-8,300 years old in now 

treeless areas (Hopkins and Giddings, 1953; Hopkins, 

1963) and evidence of thawing of3 m of permafrost and 

melting of ice wedges 10,000-9,000 years ago on the 

Seward Peninsula (Hopkins and others, 1960, p. 54-55) 

are examples of this warming. Hopkins (1972) found 

wood of a large willow 8,360 years old in an ice wedge 

cast near Bering Strait where only depauperate herbaceous tundra now exists. 

Evidence from the Kotzebue Sound area, combined 

with stratigraphic studies and radiocarbon dating, 

thoroughly documents a well-developed warming between 10,000 and 8,300 years ago in western and northern Alaska (McCulloch and Hopkins, 1966). In addition, 

in the Barrow area, Douglas and Tedrow (1960) found a 

buried discontinuous organic horizon in permafrost 

that is between 8,200 and 10,000 years old (Brown, 

1965a) and, as such, might reflect a warmer climate. 

A recent discovery of a poplar log 8,400± 300 years old 

(Detterman, 1970) in stream gravels near the 

Sagavanirktok River in northern Alaska some 50 km 

north of the present limit of poplar trees is thought to be 

further evidence of the early Holocene warm interval. 

Not all studies in western Alaska support this early 

thermal maximum. Schweger's (1971) pollen study 

from Onion Portage (p. 10) representing the last 12,000 

years reports no record of a thermal maximum but a 

gradual change from tundra vegetation to spruce cover 

as the climate ameliorated. 

The warming of the climate to give a mean annual air 

temperature of ooc or warmer has long been recognized 

in central Alaska from the lowering of the permafrost 

table and melting of tops of ice wedges. This conspicuous 

feature was noticed by Taber (1943) but attributed to 

the Yarmouth interglacial warming. 

From stratigraphic studies in the forties, it soon became apparent that this warming with subsequent lowering of ice wedge tops and the permafrost table was a 

post-Wisconsinan feature (Pewe, 1952a, 1958b, 1965a), 

possibly the hypsithermal interval. As more radiocarbon dates became available it was established that the 

warming began 10,000 years ago and the forest expanded from valley bottoms. The summers were considerably warmer. 

Pollen studies from Fairbanks by J. V. Matthews 

(unpub. data, 1966) and from the Alaska-Canada border (Rampton, 1971) indicate only a general warming 

from 10,000 years ago but no hypsithermal warming. 

The cause of the early thermal maximum is not clear. 
112 QUATERNARY GEOLOGY OF ALASKA 

McCulloch and Hopkins (1966) suggested that the 

warming in the coastal areas may have been due to a 

lower sea level and more widely exposed continental 

shelf from 10,000 to 8,000 years ago. However, Hopkins 

(1972) stated that new work by C. H. Nelson (unpub. 

data, 1970) indicates sea level was not low enough to 

expose a wide continental shelf. Also it is not clear how 

this would seriously affect interior Alaska. At the present time, the cause of the early thermal warming is 

undetermined. 

Since the early or middle Holocene thermal maximum, glaciers have advanced in most parts of Alaska. 

Advances have been most extensive in south-central 

Alaska (Plafker and Miller, 1958) and indicate a cooler 

or moister climate,.as also indicated by Heusser's study 

(1960) of the pollen record in the same area. A cooler 

climate since 3,500 years ago is also recorded in the 

Brooks Range (Livingstone, 1955, 1957). In the Fairbanks area, permafrost has reformed in the sediments 

that were thawed starting 10,000 years ago, indicating 

a return to a mean annual air temperature colder than 

0°C. However, the climate is not cold enough or snowfall 

is too great to permit ice wedge growth, except in rare 

localities. 

Rock glaciers form only in a permafrost climate and 

at altitudes lower than snowline; therefore, they are 

excellent indicators of these parameters. W ahrhaftig 

and Cox (1959) indicated that the many rock glaciers of 

the Alaska Range formed after the hypsithermal interval. This indicates that the mean annual air temperature cooled until the interstitial water remained as ice 

and, therefore, a mean annual air temperature colder 

than ooc was reached. Yet, this cooling was not 

sufficient to bring the snowline down low enough to 

create new glaciers in these valleys. Therefore, the 

mean July temperature, although colder than in the 

thermal maximum, did not drop the 3°-5°C necessary to 

produce glaciers as it did in Wisconsinan time. W ahrhaftig and Cox believed that the two relatively cold 

periods that gave rise to corresponding periods of rock 

glacier formation consisted of a 1,000--2,000 year cold 

period about 4,000--2,000 years ago and another cold 

period of perhaps 600--1,000 years within the last millennium. 

Tree-ring studies in southeastern Alaska (Lawrence, 

1950) and interior Alaska (Pewe, 1951b, 1957b) and 

lichenometry (Reger and Pewe, 1969) suggest that the 

greatest extent of glaciers since the thermal maximum 

was reached about 200--300 years ago and that the climate has since become warmer. Several photographic 

sequences covering almost 100 years are available, 

showing glacier retreat and thinning in the Brooks 

Range (Hamilton, 1965b), central Alaska (T. L. Pewe, 

unpub. data, 1952), and southeastern Alaska (Field, 

50 

100 

(/) 150 w 

a: 

1-

~200 

z 

J: 

1- 250 D. 

w 

0 

-12 

TEMPERATURE, IN °C 

-10 -8 -6 -4 -2 0 +1 

FIGURE 45.-Temperatures measured at three locations in Arctic 

Alaska (solid lines). Extrapolations are shown as broken lines. 

From Lachenbruch and Marshall (1969). 

1932b, 1942, 1947; Cooper, 1937). Maps covering glacier 

retreat for about the last 200 years are available for 

areas in southeastern Alaska. 

Quantitative data on climatic changes in northern 

Alaska over the last 100 years are available. Lachenbruch and Brewer's (1962) study of thermal records of 

deep permafrost near Barrow (fig. 45) indicates that the 

mean annual ground surface temperature rose about 

4°C since about 1850, with about half of the increase 

occurring since 1930. In the Ogotoruk Creek area of 

northwestern Alaska, the thermal record of a borehole 

357m deep in permafrost approximately 1,200 m from 

the Chukchi Sea indicates that the mean ground surface temperature rose by 2°-2%°C in the last 100 years 

(Lachenbruch and others, 1966). Lachenbruch showed 

that the mean annual surface temperature at Barrow 

100 years ago was about -12°C, and with the recent 

warming it should be about -8°C. However, the mean 

annual surface temperature today is slightly colder 

than -9°C (Lachenbruch and others, 1962). He demonstrated that recent cooling must have taken place and 

has penetrated to a depth of only 30 m (fig. 45). This 

recent cooling is also recorded in the thermal profile 

from Cape Thompson (Ogotoruk Creek). Such a cooling 

probably has been in progress only about 10 years 

(Lachenbruch and Marshall, 1969). 

This warming of about the last 100 years is further 

substantiated by Hamilton (1965a), who deduced from a 

study of U.S. Weather Bureau records fr~m the late 
LATE CENOZOIC HISTORY OF ALASKA 113 

1800's to the present that there has been a net gain in 

air temperature of about 0.5°C-O. 75°C. 

Moore and Giddings (1962) suggested that wind direction for the past 5,000 years can be deduced from 

beach ridges at Cape Krusenstern. They hypothesized 

that the wind direction changed periodically as the 

polar front shifted. Additional information from elsewhere in the Arctic should be sought to more fully 

evaluate this idea. 

Thus, in far western, northern, and central Alaska, 

maximum postglacial warming was reached early in 

the Holocene with cooling later. A fairly well 

documented record exists outlining a warming of the 

climate from rigorous Wisconsinan time climaxing in 

the thermal maximum of7 ,500-3,500 years ago in some 

parts of Alaska. During this time the permafrost table 

dropped, the vegetation patterns changed slightly, and 

snowline rose. Since the early or middle Holocene 

warming, glaciers have advanced, rock glaciers have 

formed, the permafrost table has risen, and the climate 

has cooled slightly overall. However, glacier retreat and 

thermal records from permafrost indicate a warming 

over the last 100 years. 

LATE CENOZOIC HISTORY OF ALASKA 

A record of many events over the last few millions of 

years has been reviewed in the preceding pages, events 

that form a geological, biogeographical, and climatological history of Alaska during the development of modern landscapes, vegetation patterns, and faunal distributions, and the coming of man. Landscapes have 

been identified that, at one time, were forested, with 

glaciers mere pockets of ice in the high mountains; at 

another time landscapes were dominated by a tundra 

vegetation, disrupted by wide, braided glacial streams 

from which sand and dust were blown, and magnificient 

glaciers flowed from the ranges, spreading piedmont ice 

sheets on the lowlands. Other landscapes existed when 

sea level was lower, exposing wide tundra-covered 

shelves, then the home of large grazing land mammals; 

such terrains at other times were under the sea. Climates varied from those colder than now when ice 

wedges and permafrost existed even in southern 

Alaska and altiplanation terraces, solifluction lobes, 

and rubble sheets were actively forming at elevations 

hundred of metres lower than at present, to climates 

when permafrost was essentially absent in central 

Alaska and conditions were more equable than now in 

most of the State. A review of the late Cenozoic history 

can be pieced together from large and small fragments 

of information concerning the past 2-5 m.y. in Alaska; 

this history reveals controversies and paradoxes in a 

chronological review of events oflate Cenozoic time and 

points up problems that remain to be solved. 

LATE TERTIARY 

Mountain glaciation probably began about 10-13 

m.y. ago in the St. Elias Range and other ranges facing 

the Gulf of Alaska, and magnificent tidewater glaciers 

poured seaward. The earliest evidence of glaciation is 

about early middle Miocene (Miller, 1961b; Plafker, 

1971); Bandy, Butler, and Wright (1969) believed it 

could be as young as late Miocene. The glaciers repeatedly formed ice shelves and discharged icebergs 

into the ocean (Taliaferro, 1932; Miller, 1953a, 1957; 

Plafker, 1971; Bandy and others, 1969; Kent and 

others, 1971; Scholl and others, 1971). In the Gulf of 

Alaska a mudstone accumulated at this time with 

abundant striated clasts and completely ungraded textures. The sediment consists of material that ttrained" 

upon the sea bottom from floating glacier ice. This clastic mudstone is interpreted as glacial drift and is today 

part of the Yakataga Formation (table 1). Large 

glaciers also existed on the flanks of the Wrangell 

Mountains as early as 10 m.y. ago (Denton and Armstrong, 1969). 

The extremely rugged and tectonically active 

glacier-clad terrain bordering the Gulf of Alaska in late 

Tertiary time was probably one of high relief. The climate was of the cool, temperate type such as exists 

today, not intensely cold, and rainfall was heavy. In 

fact, Hopkins (1972) mentioned that leaves of beech 

(Fagus sp.) were found with an early Pliocene mollusk 

fauna in the fine-grained beds interstratified with the 

tillites, indicating that land climates at sea level were 

somewhat milder than at present. The glaciers probably 

invaded a forest of beech trees. 

The oceans off the southern coast into which the 

glaciers discharged were about 10° colder than now, as 

indicated by the cold-water planktonic foraminifer 

Turborotalia pachyderma (Bandy and others, 1969). 

Surface-water temperature decreased about l0°-l5°C 

in late Miocene time, as indicated by molluscan and 

foraminiferal faunas (George Plafker, written commun., Apr. 21, 1970). 

Little is known of glaciation elsewhere in Alaska 

prior to Quaternary time; however, evidence suggests 

(Clyde Wahrhaftig, oral commun., July 4, 1970) that 

one of the most extensive and earliest glaciations (the 

Browne Glaciation) on the north side of the Alaska 

Range may be 2. 7 m.y. old. If so, this would indicate that 

the Alaska Range was a prominent topographic barrier 

to moisture-bearing winds from the south before the 

Pleistocene began (fig. 12). 

In the highlands adjacent to the Arctic Basin, cooling 

and glaciation undoubtedly occurred 4-6 m.y. ago, as 

indicated by ice-rafted pebbles in the sediments on the 

sea floor (Steurwald and others, 1968). Although the 
114 QUATERNARY GEOLOGY OF ALASKA 

waters of the Arctic Ocean must have begun to cool 

slightly, Hopkins (1972) pointed out that the Arctic 

Ocean probably was either ice free or only seasonally ice 

bound prior to 3 m.y. ago because the rich fauna of the 

North Pacific mollusks migrated to the Atlantic Ocean 

by way of Bering Strait about 3.5 m.y. ago and later, the 

time of the Beringian transgression. 

Hopkins further stated that the recent discovery of 

Turritella in Pliocene beds offshore indicates temperate 

shelf waters during Pliocene time. Later, ice-rafting 

must have increased in the Arctic Ocean and eventually 

pack-ice cover formed (table 1). However, the Arctic 

Ocean probably remained essentially free of pack ice 

throughout the Pliocene epoch (Herman, 1970; Herman 

and others, 1971). 

In general, the climate oflate Tertiary time in Alaska 

must have been relatively equable and not intensely 

cold, although glaciers were present in the southern 

highlands during part of Miocene and all of Pliocene 

time. Little evidence is available concerning Alaskan 

vegetation in late Tertiary time, but in northern Sew-· 

ard Peninsula a forest of spruce, birch, pine, and hemlock existed 5. 7 m.y. ago (Hopkins and others, 1971), 

indicating an environment similar to southeastern 

Alaska and coastal British Columbia rather than the 

Arctic climate of today. In general, the flora of the time 

of the Beringian transgression indicates that western 

and northern Alaska was considerably warmer than at 

present. 

In late Tertiary time the Bering land bridge existed at 

various intervals. The Pacific and Arctic Oceans became connected by a shallow, sinuous seaway in late 

Miocene time, but the land bridge was reestablished 

about 5 m.y. ago. However, 3.5 m.y. ago, during the time 

of the Beringian transgression, there was free marine 

communication between the Bering and the Chukchi 

Sea. 

Apparently toward the end of Pliocene time, the climate began to become more rigorous when perhaps the 

glaciers grew and the climate cooled to produce frost 

features. Hopkins (1972) reported boulder pavements 

created by frost action on basaltic lavas as old as 2 m.y. 

on St. George Island. Also, in very late Pliocene or very 

early Pleistocene time in central Alaska, angular, 

coarse auriferous gravel was being created in part by 

cutting of altiplanation terraces by nivation. The frost 

rubble produced by nivation and hillside rubble produced by frost action and other weathering processes 

moved downhill by solifluction to be buried by later 

Quaternary sediments. The tundra cover and associated colder climates probably did not arise in northern Seward Peninsula until early Pleistocene time. 

EARLY PLEISTOCENE 

The early Pleistocene history of Alaska is less clearly 

seen than the late Tertiary or the later part of the 

Pleistocene. Massive glaciers drained from mountains 

on the north side of the Gulf of Alaska and discharged 

into the sea, forming marine till. The fauna in most of 

the marine till indicates that part of the sediment is 

equivalent in age to the Anvilian transgression and 

later. In fact, sediments in the upper part of the section 

described by Miller (1953a) from Middletown Island 

represent the earliest Pleistocene ice advances and 

represent continual deposition from Pliocene time. 

Also, large glaciers of early Pleistocene age existed in 

parts of the St. Elias Range and Wrangell Mountains 

(Denton and Armstrong, 1969). Large glaciers evidently poured south from the Alaska Range (pl. 1) 

through the Cook Inlet trough and probably represent 

the Mount Susitna Glaciation of Karlstrom (1964). On 

the Seward Peninsula, glaciers moved south from the 

Bendeleben Mountains and entered the sea. This glaciation, called the Iron Creek Glaciation by Hopkins 

(1972), is thought to be 1.0±0.5 m.y. old. The glacial 

deposits underlie beds of the Anvilian transgression 

(table 8) that are less than 1 m.y. old but more than 

700,000 years old. 

Little information is available regarding temperature of the sea water in early Pleistocene time, but 

mollusks, particularly Portlandia, dredged from rocks 

of early Pleistocene age in the southern Bering Sea 

indicate that water temperatures were colder than now 

(Hopkins and others, 1969). Portlandia is not known to 

occur south of the Bering Strait at the present time. 

Undoubtedly, the ice cover on the Arctic Ocean was 

becoming more extensive than in late Pliocene time, 

because by about 1 m.y. or 700,000 years ago, the permanent icepack was established (Herman, 1970; Herman and others, 1971). Steurwald, Clark, and Andrews 

(1968) believed that the Arctic Ocean was no warmer 

than at present for as long as the last 1.5 m.y. 

The cooling of Alaska in early Pleistocene time is 

further borne out by periglacial phenomena. Ice wedge 

pseudomorphs are reported at Cape Deceit on the south 

shore of Kotzebue Sound (Guthrie and Matthews, 1971), 

and Hopkins (1972) believed they represent a permafrost period of 1.0±0.5 m.y. ago. 

Around the beginning of Pleistocene time, the valleys 

of the small streams and rivers in central Alaska began 

to receive great amounts of angular, coarse auriferous 

gravel as altiplanation terraces were cut on the glacierfree highlands in the periglacial environment. The angular gravel was carried downhill by solifluction to accumulate in the valley bottoms, inasmuch as most of the 

material could not be removed by the drainage of the 

time. Remnants of solifluction layers of this age are 

widespread in central Alaska and contain welldeveloped ice wedge pseudomorphs (fig. 33). The ice 

wedges are thought to be at least 1 m.y. old because they 
LATE CENOZOIC HISTORY OF ALASKA 115 

represent the older of two permafrost periods, both of 

which predate the Illinoian Glaciation. Central Alaska 

must have had a mean annual air temperature less than 

-6° to -soc at this time. 

On the north side of eastern Seward Peninsula during 

a very early glaciation, thought to be correlative with 

the Iron Creek Glaciation, the forests were absent, and 

a more severe tundra than now existed. At this time 

nonwoody peat formed. However, just prior to this cold 

period and in very early Pleistocene time, a forest 

tundra existed, and the tree line advanced as far as 

Cape Deceit (Guthrie and Matthews, 1971); the vegetation was vastly different from that oflate Tertiary time. 

There is a clear record of repeated dispersals of land 

mammals from Asia to Alaska through much late 

Cenozoic time. The environment was such that most 

northern species of mammals could migrate-across the 

land bridge; however, animals that inhabited forested 

mountain regions found it difficult or impossible to 

move across the open tundra landscape. The musk deer 

as well as the woolly rhinoceros were confined to the 

forest areas and did not move from Asia into Alaska. 

Many genera and species of animals moved across the 

bridge into Alaska much earlier than ordinarily recognized. In the Cape Deceit Formation (Guthrie and 

Matthews, 1971), there is evidence that in rather early 

Pleistocene time Rangifer, Equus, and Microtus had 

already moved into Alaska as had Pliomys. Other 

mammals that definitely were in Alaska in the early 

Pleistocene were Canis, Cervus, Ochotona, Lemmus, as 

well as an early collared lemming, Predicrostonyx hopkinsi (table 11). 

MIDDLE PLEISTOCENE 

The nature of the subaerial climate and landscape in 

Alaska is still poorly known in the rather ill-defined 

period of time from the earliest glaciation in the Pleistocene Epoch to the definite interglacial period prior to 

the Illinoian Glaciation. Nevertheless, enough 

significant data are becoming available from various 

areas to attempt to construct an outline of events during 

this interval. 

After the early Pleistocene cold period, or periods, the 

Anvilian transgression occurred. This higher stand of 

sea level probably took place between 1.8 and 0.7 m.y. 

ago (Hopkins, 1972) (tables 1, 3). Warmer water temperatures than in the modern Bering and Chukchi Seas 

as well as the Arctic Ocean existed in Anvilian time, 

according to mollusk distribution. N atica janthostoma 

lived in the vicinity of Nome and Skull Cliff in northern 

Alaska but is now limited to waters adjoining Japan. 

During the warmer part of Anvilian time, winter ice 

probably did not reach Nome and may not have reached 

the Arctic coast of Alaska (Hopkins, 1967b). The Arctic 

Ocean was somewhat warmer than at present, but there 

is no unanimity as to whether pack ice was present 

(Herman, 1970; Herman and others, 1971; Hunkins and 

others, 1971). 

A warm episode in central Alaska that possibly may 

be correlated with the Anvilian transgression in the 

west caused the glaciers to withdraw and permafrost to 

thaw. The ice wedges in solifluction deposits melted and 

were replaced with windblown sand that filtered down 

from the overlying sand dunes, forming ice wedge 

pseudomorphs (fig. 33). Lowering of the permafrost 

table and disappearance of ice wedges indicate that the 

mean annual air temperature was at least warmer than 

0°C. From both marine and terrestrial deposits, then, 

comes strong evidence of a major warm interglacial 

period perhaps 1 m.y. ago. 

In several parts of Alaska, there is evidence of two or 

more Pleistocene cold periods of pre-Illinoian age. The 

exact stratigraphic positions are unknown, but one or 

two of the cold periods lie in what may roughly be called 

middle Pleistocene time. After the warm period marked 

by the Anvilian transgression, the climate became more 

rigorous. Glaciers flowed northward into the Tanana 

valley from the Alaska Range during the Dry Creek 

Glaciation (W ahrhaftig, 1958) and Darling Creek 

Glaciation (Pewe and others, 1953). Larger glaciers 

pushed south from the ice-mantled Alaska Range and 

other ranges surrounding the Cook Inlet -Susitna valley trough to produce the massive trunk glacier of the 

Caribou Hills Glaciation (Karlstrom, 1964). 

In other areas scant evidence suggests (table 2) that 

glaciers were quite extensive in this middle Pleistocene 

time in such areas as the Alaska Peninsula, the Brooks 

Range, and the Delta River area of the central Alaska 

Range. Undoubtedly, massive glaciers also continued to 

exist on the Wrangell Mountains and the ranges facing 

the Gulf of Alaska. Pack ice was probably widespread in 

the Arctic Ocean, since it appears to have been established at least 700,000 years ago (table 1). 

Periglacial deposits in central Alaska record coldclimate processes active at this time. Solifluction lobes 

were moving downhill at an elevation as low as 150m 

above sea level in central Alaska at this time. Today, 

active solufluction lobes exist only above an elevation of 

1,000 min central Alaska. Perhaps the upper of two 

well-developed inactive solufluction layers on the campus of the University of Alaska (fig. 33) is middle Pleistocene in age. Periglacial processes in middle Pleistocene time were active in the creation of altiplanation 

terraces from the Canadian border to far western and 

southwestern Alaska. Near the Fairbanks area, altiplantation terraces were being cut at elevations between 300 and 900 m above sea level, indicating a most 

rigorous climate because such terraces are not being cut 

today even at elevations of 1,600 m near Fairbanks. 

Permafrost was widespread throughout Alaska dur-
116 QUATERNARY GEOLOGY OF ALASKA 

ing the one or more middle Pleistocene cold intervals, as 

indicated by the presence of ice wedges then. It is 

thought that permafrost existed even at low altitudes 

on St. Paul Island at this time (Hopkins, 1967b); permafrost does not exist on St. Paul Island today. 

In addition to the cold periods recorded in middle 

Pleistocene time, an interglaciation is recorded by a 

high stand of sea level, the Einahnuhtan transgression 

of between 250,000 and 100,000 years ago (Hopkins, 

1967b). The temperature of the sea water at that time 

was about as at present, and pack ice probably was 

present in the Arctic Ocean. The Bering Strait and the 

Arctic Ocean were connected at this time. The warm 

interval cannot be directly associated with the cold intervals because of the lack of dating of the welldocumented cold periods of middle Pleistocene time in 

Alaska. 

YARMOUTH(?) 

The history of the period of climatic warming just 

prior to Illinoian time is clearer in Alaska than earlier 

Pleistocene events and is here treated as an interglacial 

episode, probably Yarmouth(?) in age. Although the 

correlations with the central United States and Europe 

time equivalents are not proved, evidence accumulated 

from marine deposits in the far west indicates that this 

is probably a correlative event. 

During this time, the glaciers had greatly withdrawn, 

and sea level had risen probably 20 m above present sea 

level. This event was termed the Kotzebuan transgression by Hopkins (1965) and is correlative with the Holstein transgression of northern Europe. Hopkins (1972) 

thought it might correspond to the high sea level 

episode dated on many tropical shores at about 120,000 

years old. Perhaps the marine beds at South Bight on 

Amchitka Island are of a Kotzebuan age; bones and 

shells there are about 130,000 years old (Gard and 

others, 1972). 

During this high stand of the sea, the Pacific Ocean 

was connected to the Arctic Ocean. Hopkins (1972) believed that the usual northward circulation through 

Bering Strait was probably reversed at this time and 

cold water must have persistently flowed southward 

because high-Arctic molluscan and foraminiferal fauna 

around the shores of Kotzebue Sound, as well as on the 

Siberian side of the strait, indicate very cold water. 

During the interglacial period, northwestern Seward 

Peninsula was forested, and spruce line advanced to at 

least as far as Cape Deceit. Today this area lies in the 

tundra region (fig. 40). In central Seward Peninsula 

summers were longer and warmer than now. In interior 

Alaska the climate was warm, in fact warmer than now, 

tree line rose, and forests were widespread. Welldeveloped forests were present, as indicated by the 

widespread forest beds at the base of the Illinoian loess 

(figs. 29, 41). 

The thawing of the permafrost and melting of ice 

wedges in central Alaska indicate that the mean annual 

air temperature had warmed to at least ooc and probably a few degrees warmer. 

ILLINOIAN 

Illinoian time in Alaska was one of maximum glaciation. Glaciers were extensive, and about 50 per cent of 

the State was covered by ice (fig. 6) the earlier glaciations probably were not much more extensive. The 

mountains in southern Alaska were clothed with massive valley glaciers and small icecaps which coalesced to 

form large trunk or trough glaciers as well as piedmont 

ice sheets. Ice from the Alaska Range moved south, 

completely blanketing the lowlands between the 

coastal ranges to the south; the ice then moved south 

and southwest toward the Alaska Peninsula. Ice was 

undoubtedly widespread in southeastern Alaska at this 

time, but no information is available. Local cirque and 

short valley glaciers were present in central Alaska. Ice 

coverage in Illinoian time in the Brooks Range was 

extensive (fig. 6) and much greater than in later Wisconsinan time, probably because most of the Brooks 

Range was high enough to intersect the Illinoian snowline but not high enough to intersect the higher Wisconsinan snowline. The major ice coverages in the Brooks 

Range and the Alaska Range-Coastal Range complex 

extended to the east, where they joined to form part of 

the Cordilleran ice sheet of North America. 

Glaciers on Seward Peninsula pushed south from the 

central mountains and also were present on the far 

western tip of the peninsula. Glaciers from the 

Chukotka Peninsula of the U.S.S.R. adjacent to the 

Bering Strait pushed southward and eastward, reaching as far as St. Lawrence Island. Ice from U.S.S.R. 

probably pushed across dry land and did not exist as 

floating ice during the Kotzebuan transgression, as believed by Soviet workers (Hopkins, 1972). 

Between the major ice-covered areas of the south and 

north in Alaska the Beringian refugium existed, which 

extended westward across the Bering land bridge. 

Many lobes of valley glaciers pushed into this refugium 

both from the Brooks Range on the north and the 

Alaska Range on the south (fig. 6). To the north of the 

Brooks Range an ice-free polar desert existed (Pewe, 

1974a). 

The altitudinal and areal distribution of the glaciers 

clearly indicates that as today, moisture sources were 

clearly to the south and the southwest in the north 

Pacific Ocean and the shrunken Bering Sea. Little 

moisture was contributed by air masses entering 
LATE CENOZOIC HISTORY OF ALASKA 117 

Alaska from the Arctic Basin, as suggested by Ewing 

and Donn (1956, 1958). As in later time and today, the 

glaciers were more extensive in the southern part of the 

State than in the north and formed larger ice streams on 

the south side than on the north side of single mountain 

ranges (Karlstrom, 1964). Snowline was about 500-600 

m lower than now and 150-250 m lower than its position 

during Wisconsinan time in different parts of Alaska. It 

was highest in the dry continental climate of eastcentral Alaska where it lay at an altitude of about 1,250 

m during Illinoian time. Snowline sloped downward to 

an altitude of less than 300m on Seward Peninsula in 

western Alaska (fig. 8). 

If we visualize such an extensive glacial cover over 

Alaska in Illinoian time, we must, as a consequence, 

understand that all major streams and almost all minor 

streams drained glaciated terrain. Therefore, the glacial streams were undoubtedly choked with glacial silt, 

were aggrading, and had extensive braided, 

vegetation-free flood plains (fig. 42). Winds in the valleys blew silt from these barren flood plains and deposited it as loess over the countryside. Loess was deposited 

on ridges as high as 750 m above sea level, but most of it 

was deposited at lower altitudes, being thickest near 

streams. The Kuskokwim and Yukon Rivers wandered 

across the then dry floor of the Bering Sea, and from 

their flood plains, silt was blown to be deposited as loess 

on the Pribilof Islands. The greatest loess deposits are 

confined to central and western Alaska (fig. 17) and are 

locally as much as 50 m thick. Huge areas of dust blown 

from the flood plains were common throughout parts of 

Alaska, similar to areas of dust being deposited today as 

lpess near such outwash streams as the Delta and Knik 

Rivers (pl. 1). Although sparse vegetation on flood 

plains is indicated by this wide distribution of eolian 

deposits, it does not necessarily indicate sparseness of 

vegetation away from the flood plains or aridity 

throughout Alaska, nor does it require exceptionally 

high winds. 

Closer to the glaciers and mostly along the major 

streams, sand was blown, and widespread dune fields 

and sand blankets formed. Active dune fields were 

common along the Yukon, Tanana, Koyukuk, and Kuskokwim Rivers as well as near the flood plains of major 

rivers on the North Slope of Alaska. 

The climate of the Illinoian glacial interval was 

rigorous, and abundant evidence indicates that permafrost was widespread. Ice wedges throughout most of 

Alaska reflect a periglacial climate with a mean annual 

air temperature of at least -7°C, about 2°-4°C colder 

than the present mean annual air temperature in central and western Alaska. Undoubtedly, periglacial frost 

features other than permafrost and ice wedges were 

present in unglaciated areas during Illinoian time, but 

as yet few have been recognized except perhaps rubble 

sheets on Jumbo Dome (Wahrhaftig, 1949). 

In Illinoian time central Alaska and the North Slope 

were refugia, most probably with a tundra environment 

and perhaps with a scattering of some spruce and other 

trees in a few of the valley bottoms of central Alaska. 

The record of the flora in Alaska at this time is very 

scant and restricted to the Seward Peninsula and the 

Fairbanks area. In central Seward Peninsula, study of 

pollen from a core from Imuruk Lake (Colinvaux, 1962) 

indicates an Arctic grass tundra with little or no alder 

and some dwarf birch. Sage (Artemisia) was more common than now or in an interglacial period. Tree line was 

not close. On the northern part of Seward Peninsula at 

Cape Deceit, a tundra environment was present (Guthrie and Matthews, 1971). 

Pollen analysis of samples of peat from Illinoian loess 

collected by the writer in valley bottoms of the Fairbanks area indicates that at this time tree line was 

significantly lower and trees were conspicuously rare. A 

lowering of tree line to creek valley bottoms required a 

drop of 450-600 m from today's tree line, suggesting 

that the climate, especially the summers, was indeed 

colder than now. A much more restricted forest area is 

also borne out by the greater number of grazers (especially mammoth, bison, and horse) then than now. The 

increase in Artemisia at this time probably does not 

support a case for widespread aridity in Alaska. Artemisia probably found a more favorable habitat on the 

almost vegetation-free sand dunes and flood plains of 

braided glacial streams that were so abundant at this 

time, rather than a general widespread increase of Artemisia throughout the entire tundra environment of 

hillslopes and boggy valley bottoms. 

Although data are very meager, Hopkins (1972) believed that the exposed continental shelf of the Bering 

Sea at this time had a relatively maritime climate and 

supported a shrub tundra. 

Over this widespread tundra environment wandered 

a large vertebrate population similar to that which existed in Wisconsinan time (fig. 42). Animals such as 

ground squirrels, lemmings, goats, and sheep limited to 

above or near tree line today lived at lower altitudes. 

The most abundant of all the mammals in Illinoian time 

were mammoth, horse, and bison. Despite information 

in modern literature to the contrary, Rangifer, 

Praeovibos, Ovis, Alces, Ovibos, Saiga, Bootherium, 

Symbos, and Discrostonyx as well as others were widespread in Illinoian time in Alaska. Perhaps most of 

them lived near the flood plain in winter where the 

winds blew much of the snow from the sparse vegetation; in summer they may have migrated to the lower 
118 QUATERNARY GEOLOGY OF ALASKA 

slopes. Saiga is found nowhere else in North America 

but Alaska; this area represents the easternmost extension of its Siberian range, and southward penetration 

from Alaska was probably prevented by mountains and 

glaciers. Saiga is found both on the North Slope and in 

central Alaska during Illinoian time, and the environment favored by this animal is one that would have 

existed on the abundant windswept, flat, braided flood 

plains of glacial streams. 

SANGAMON 

The interglaciation between the Illinoian and Wisconsinan cold periods is well documented in Alaska. It 

was a time of great withdrawal of the glaciers, rising of 

sea level, thinning and disappearance of permafrost in 

many areas, and the return of the forests to most of the 

tundra regions, at least south of the Brooks Range. 

With the warming of the climate in Sangamon time, 

the glaciers withdrew in Alaska as elsewhere around 

the world, and sea level rose. The rise of sea level and 

transgression onto the land in Alaska was termed the 

Pelukian transgression by Hopkins (1965). It is recorded widely throughout Alaska by well-preserved 

marine terraces and fairly well preserved marine scarps 

that occur 7-10 m above present sea level. Mollusks and 

fish present in the waters at this time off western and 

northwestern Alaska indicate that the sea was warmer 

than at present. For example, Hopkins (1972) mentioned that the deposits near Nome contain several 

species of mollusks such asPholadidea penita, Littorina 

littorea, N atica janthostoma, and others which are now 

limited to more southern waters. 

The warming of the climate is further recorded by the 

deep oxidation profiles present on Illinoian glacial 

moraines throughout central and western Alaska and 

by evidence of thawing of permafrost. Permafrost probably completely disappeared in Fairbanks, as indicated 

by the abundant ice wedge pseudomorphs, thick oxidation profiles in Illinoian loess, and absence of preserved 

mammal carcasses of Illinoian age. The mean annual 

air temperature undoubtedly was well above ooc for a 

long period of time. Although it may have been absent 

in central Alaska, permafrost was still abundant in 

northern Alaska, and some was present in western 

Alaska, even though frozen ground melted to considerable depths and ice wedges melted (McCulloch, 1967). 

At the time of thawing, the loess in central Alaska 

was deeply gullied, and block slumping occurred. Long 

parallel gulleys more than 10m deep and 180m long 

were cut in the easily eroded loess on slopes in the 

Fairbanks area. 

The tundra environment present earlier in central 

Alaska was replaced by a spruce-birch forest. Forests 

were widespread, as indicated by buried forest layers 

dated at more than 56,900 years old between Illinoian 

and Wisconsinan loess (fig. 29). Summers were longer 

and warmer; the mean July temperature in the Sangamon, for example, was undoubtedly warmer than the 

present mean July temperature of 15.5°C at Fairbanks. 

The forest probably pushed northward to a position on 

the north side of the Brooks Range, as indicated by large 

logs found in the frozen ground (Hopkins, 1972), and 

advanced westward into the area of now treeless tundra 

(fig. 40) on the Baldwin Peninsula near Kotzebue 

(McCulloch and others, 1965). At Cape Deceit, however, 

a tundra environment existed; also, Colinvaux (1962) 

noted that at Imuruk Lake at this time the vegetation 

was a sage-alder tundra similar to the present conditions, but tree line was near. Colinvaux (1967b) suggested that in Sangamon time tundra was present on St. 

Lawrence Island, and all evidence so far indicates that 

the Alaskan side of the Bering Strait had a vegetation 

comparable to the present, even though spruce trees 

were 50-80 km west of their present limit in the Kotzebue Sound and Nome areas. 

WISCONSINAN 

In Wisconsinan time glaciers existed in nearly all the 

mountainous areas of Alaska. North of the crest of the 

Alaska Range and on the Alaska Peninsula, the 

glaciers were essentially the alpine type; they filled 

mountain valleys and in places spread as piedmont 

lobes in adjoining lowlands. However, central and 

northern Alaska were essentially ice free. Areas south 

of the crest of the Alaska Range and the Alaska Peninsula were almost completely inundated by ice, and 

icecap conditions prevailed over large areas {fig. 6). 

Glaciers filled adjoining lowland basins such as the 

broad Susitna valley and spread onto the then dry continental shelf, thickening to form icecaps as much as 

several tens of kilometres wide and several hundreds of 

kilometres long. The icecap in the Shelikof Strait sent 

glaciers northward where they penetrated passes into 

the mountainous backbone of the Alaskan Peninsula. 

Similar icecaps accumulated at several places in the 

Aleutian Range. During this latest major cold period, 

glaciers pushed south into Prince William Sound, and 

ice shelves were undoubtedly present. In the south half 

of Alaska the glaciers were almost as extensive as in 

Illinoian time. However, in northern Alaska the 

glaciers of the Brooks Range were much less extensive, 

as were those in the Bering Strait and on the Seward 

Peninsula (fig. 6). Wisconsinan glaciers may not have 

been very extensive along the Gulf of Alaska between 

Cape St. Elias and Russell Fjord because the mountains 

north of this part of the Gulf of Alaska coast were lower 

during Wisconsinan time. 

Glaciers in the Copper River Basin did not extend far 
LATE CENOZOIC HISTORY OF ALASKA 119 

enough to completely cover this lowland, and ice 

blocked all the exits from the basin, producing a huge 

lake at least once during Wisconsinan time. The lake(s) 

existed for thousands of years, and laminated clays 

were interbedded with glacial deposits and volcanic 

mudflows. Undoubtedly, volcanic flows poured from the 

Wrangell Mountains into the Copper River Basin probably over glaciers or under glacial ice. Near the end of 

Wisconsinan time, drainage from the basin was reestablished, the lakes drained, and the former lake floor 

was entrenched. 

In the western Brooks Range a large proglacial lake 

was formed by glacial blockage between the DeLong 

and Endicott Mountains. 

A comparison between snowlines in Wisconsinan 

time and the present in Alaska reveals a strikingly 

similar pattern of isolines and of wind and moisture 

sources. The pattern and close parallelism of modern 

and Wisconsinan snowlines strongly suggest that increased precipitation did not produce Wisconsinan 

glaciers, but rather a decrease in mean summer temperatures and an increase in summer cloudiness, which 

resulted in decreased snow and ice ablation. Also, in 

Wisconsinan times the major sources of moisture, as in 

the past, were from the south and southwest in the Gulf 

of Alaska and the shrunken Bering Sea. There is no 

evidence that the ice-covered Arctic Ocean contributed 

enough moisture to sustain glacier growth. Interestingly, much of the precipitation for the south side of the 

central and eastern Alaska Range evidently entered 

through the Cook Inlet trough, as it does today. As 

indicated in figures 8 and 9, and especially 11 and 12, in 

Wisconsinan time there was an abrupt rise in snowline 

from near sea level in the Gulf of Alaska to about 1,500 

min interior Alaska. There was a steady rise from the 

Bering Sea on the west, eastward to Canada through 

central Alaska. In general, Wisconsinan snowline was 

about 300-400 m lower than modern snowline in the 

west and about 450-600 in the east, but local variations 

occurred. The vertical separation of the two snow lines 

becomes greater toward the interior because probably 

in Wisconsinan time, as now, the interior is drier than 

the far west. 

Knowledge of the position of snowline in Wisconsinan 

time permits us to calculate past temperatures on the 

basis of the knowledge of the present lapse rate. For 

example, as indicated earlier, values for Wisconsinan 

mean July temperatures based on a critical evaluation 

of the present lapse rate and snowline in turn based on 

Wisconsinan cirque floors give us a broader view of 

summertime climate in central Alaska in Wisconsinan 

time (table 14). The difference between Wisconsinan 

and modern mean July temperatures is greater in the 

interior of Alaska than in the more cloudy, cool west. In 

Wisconsinan time, for example, the mean July air 

temperatures at N orne and Kotzebue were soc and 

9.2°C, respectively, which is 1.9°C and 2.1 oc lower than 

now. In the interior, however, at Fairbanks and Northway, mean July air temperatures were at least 4°C and 

4.8°C lower in Wisconsinan time, if the temperatures 

there were 11.5°C and 9.9°C, respectively. 

As in Illinoian time, all major and most minor 

streams drained glaciated areas and exhibited braided 

scantly vegetated flood plains which were excellent 

sources for silt and sand picked up and blown by the 

winds probably similar in velocity to those of today. 

Great quantities of sand were blown from these flood 

plains, glacial outwash fans, and outwash plains to produce extensive dune fields along the major streams such 

as the Tanana, Yukon, Koyukuk, and Coleville Rivers. 

These dunes, widespread as they were, were much more 

restricted than those of Illinoian time. With the lowering of sea level, large areas of the Bering Strait were 

exposed, presenting sand and silt to deflation. Hopkins 

(1972) believed that the great area of dune sand and 

loess covering 12,000 km2 of northwestern Seward 

Peninsula was derived from a blanket of marine sand 

left exposed beneath the present-day Chukchi Sea. 

Also, the sand and loess on the Pribilof Islands date 

back to a time when the shoreline was much farther 

south than present. 

During the Wisconsinan Glaciation, winds deposited 

a blanket of loess across central and western Alaska. 

Much of the loess deposited on the hills of central 

Alaska was retransported to valley bottoms to form an 

organic-rich, fetid, perennially frozen deposit. These 

deposits accumulated to a thickness as much as 60 m 

and incorporated abundant vertebrate and plant fossils 

of the time, including partial carcasses of vertebrates 

that did not completely decay prior to burial. 

The gulleys and ridges of pre-Wisconsinan age in the 

loess on middle and upper slopes in the Fairbanks area 

were rounded and subdued by the Wisconsinan loess 

blanket. 

The extensive eolian sand and loess of Wisconsinan 

age are interpreted not as an indication of former greater aridity or any. substantial change in the amount and 

direction of winds but, instead, as in earlier major glaciations, as an extensive increase in poorly vegetated or 

nonvegetated sandy, gravelly, braided flood plains and 

outwash fans and plains throughout Alaska. 

Permafrost in Alaska extended much farther south 

than at present (fig. 22), indicating that the mean annual air temperature was -1°C or colder at the south 

border of the State, a few degrees colder than now. In 

northern and northwestern Alaska, ice wedges were 

actively growing in the cold permafrost as they are 

today. In central Alaska permafrost and the mean an-
120 QUATERNARY GEOLOGY OF ALASKA 

nual air temperature may have been colder than today 

because ice wedges were actively growing then; today 

they are, for all practical purposes, inactive. Active ice 

wedges indicate that the mean annual air temperature 

was -6° to -8°C or colder; this would require a mean 

annual air temperature at least ~4°C colder than at 

present. Perhaps it also indicates that the light, fluffy 

snow was somewhat more windblown and packed, probably because of the scarcity of trees. 

Many of the existing large deep-lying ice wedges in 

the Fairbanks area have flat tops indicative of a downward thawing of permafrost and ice wedges som~time in 

Wisconsinan time. This thawing was dated as more 

than 38,000 years old (Sellmann, 1967) and is thought 

to represent a short middle Wisconsinan, or earlier, 

warm period when the mean annual air temperature 

was warmer than 0°C. 

Rubble sheets, rock glaciers, and solifluction lobes 

were active on the slopes of central and western Alaska 

at lower altitudes than at present. Rubble sheets indicating a colder climate and more rigorous frost action 

were common on the south side (Pewe, 1961c) and the 

north side (Wahrhaftig, 1958) of the Alaska Range. 

Such frost-shattered and transported bedrock is also 

common in Seward Peninsula and even reported active 

on St. Paul Island almost at sea level during Wisconsinan time (Hopkins, 1972). 

Approximately 50 percent of Alaska was ice free in 

Wisconsinan time and supported, for the most part, 

some form of tundra. The present taiga forest was 

greatly restricted and almost eliminated. Various types 

of tundra existed; in the far west Coljnvaux reported 

(1967a) an Arctic herbaceous tundra, and Arctic sage 

was relatively common. Heusser (1963b) assumed that 

a tundra with little birch existed around Kotzebue 

Sound and Ogotorok Creek. On St. Lawrence Island was 

a tundra with grasses and sages predominating (Colinvaux, 1967a) 

In central Alaska peat samples collected by the writer 

from Wisconsinan loess indicate that the valleys were 

covered with tundra rich in alder and dwarf birch with 

little grass. They also indicate that coniferous trees 

were scarce. In the valley bottoms at that time was a 

grass-sage-moss-Equisetum cover associated with 

small stands of dwarf birch and willow. The forest was 

not entirely absent as indicated by tree remains in 

beaver dams of late Wisconsinan age. Such dams include alder, spruce, willow, cottonwood, and birch wood. 

Matthews (1970) reported that the spruce woodlands 

were nearly eliminated from interior Alaska in Wisconsinan time. Tree line in central Alaska dropped about 

500 - 600 m, and the following tree-line mammals existed in lowlands near Fairbanks: ground squirrel, 

lemming, collared lemming, and mountain sheep. 

These animals now live at or above tree line on the 

tundra and not in the now-forested Fairbanks area. 

During much of Wisconsinan time, grass and some 

sage (Artemisia) perhaps were abundant on the welldrained, much more extensive braided glacial flood 

plains, outwash fans, and outwash plains in unglaciated Alaska. These broad, flat areas were favored 

places for great herds of grazers such as the bison, 

mammoth, and horse, especially for part of the year. 

The habitat for grazers and the records of grasslands 

and xeric vegetation can most easily be explained by the 

great increase of these treeless flood plains and active 

sand dune areas in Wisconsinan time, rather than by a 

widespread arid condition throughout the unglaciated 

part of the State. The rolling, lower hill slopes and small 

creek bottoms were probably boggy, perhaps more so 

than today, because the permafrost level was higher in 

Wisconsinan time and drainage was even poorer than 

now. Peat layers were common in the valley bottoms. 

It is also unnecessary to assume that a treeless vegetation prevailed in central Alaska in full glacial time 

and that the spruce persisted in a refugium somewhere 

in southwestern Alaska until about 6,000-8,000 years 

ago. Scattered spruce persisted in isolated creek bottoms in central Alaska (fig.42), inasmuch as spruce 

wood occurs in the frozen retransported silt of Wisconsinan age in the Fairbanks area. It seems more logical 

that repopulation of the forest of the interior and far 

west was from small nuclei preserved in the valleys of 

central Alaska. In fact, Young (1971) noted that the 

central part of Alaska would be expected to have a 

continental climate with summers warm enough to 

permit the growth of trees. 

Throughout Wisconsinan time, the unglaciated refugia were occupied by an extensive mammal population, many species of which no longer exist today. As 

mentioned elsewhere, many more grazers were present 

then than now, and many of the tree-line and above 

tree-line species were more widespread than at present. 

The most abundant larger mammals were the mammoth, horse, and bison. It is in this environment that 

many of the carcasses of the animals were preserved 

because of the _cold winters and short summers and 

eventually became buried to be perennially frozen until 

today. 

Toward the end of Wisconsinan time, as the forest 

began returning, the ideal habitat of many of the grazers began to disappear. With the loss of the ideal habitat 

and increased predation by man, many mammals became extinct about 10,000 years ago. In late Wisconsinan time a marine transgression, the W oronzofian (Hopkins, 1967a), occurred, during which sea level was only 

a few metres lower than at present. Recent work by 

Schmoll, Szabo, Rubin, and Dobrovolny (1972) indi-
LATE CENOZOIC HISTORY OF ALASKA 121 

cated that this transgression occurred around 14,000 

years ago. 

With the regressions and transgressions of sea in the 

Bering Strait area during Wisconsinan time, the Bering 

land bridge, the gateway from Asia to North America 

for many forms of life including man, was present for 

thousands of years and then narrowed and disappeared 

for intervals of time. It was demonstrated (Hopkins 

1967a) that the bridge was present prior to 35,000 years 

ago but that it probably narrowed and was severed 

during middle Wisconsinan time, about 35,000-25,000 

years ago. The land connection was restored during late 

Wisconsinan time, 25,000-12,000 years ago, although 

land connections may have been drowned occasionally 

for short periods during that interval. The land bridge 

was closed at the end of Wisconsinan time, between 

11,000 and 10,000 years ago, when the sea rose. 

HOLOCENE 

About 10,000 years ago, the landscape began to take 

on aspects present today. Glaciers began to retreat, the 

forest began to return to much of the unglaciated terrain of central Alaska, and permafrost began to thaw 

and retreat northward. The record in Alaska does not 

illustrate a simple warming, retreat of the glaciers, or 

change of vegetation since Wisconsinan time but an 

oscillation of events. In general, the glaciers did begin to 

retreat about 10,000 years ago, but they still were in a 

rather advanced position on the north side of the Brooks 

Range, for example, from 8,300 to about 6,300 years ago 

(Porter, 1964). In most of Alaska the glaciers record the 

greatest retreat and farthest withdrawal at a time of 

thermal maximum, perhaps around 5,000-3,000 years 

ago. In southeastern Alaska the glaciers had withdrawn farther at that time than they have today 

(Goldthwait, 1963, 1966). 

After this major post-Wisconsinan withdrawal, the 

glaciers advanced in the Brooks Range about 2,800 

years ago. In southeastern Alaska they started to advance about 3,500 years ago, reaching a maximum 

probably only 300 or 400 years ago. In central Alaska it 

appears that greatest glacier advance after postWisconsinan thermal maximum was reached only as 

late as 200 or 300 years ago. In most parts of the State, 

glaciers have been retreating dramatically for the last 

200 years. 

In parts of Alaska the classic postglacial thermal 

maximum (hypsithermal) is not recognized. Instead, an 

earlier dramatic warming and vegetation change began 

around 10,000 years ago, and then the record shows 

gradual warming and forest establishment with some 

cooling to the present. In the west and northwest, the 

spruce forests were farther westward 9,400-8,300 years 

ago than now, and 9,000-10,000 years ago permafrost 

with ice wedges thawed down 3 m on the Seward Peninsula (Hopkins and others, 1960). 

Around 10,000 years ago near Fairbanks, there was a 

thawing of permafrost, lowering of the tops of the ice 

wedges, and reintroduction of forest (Pewe, 1975). 

Subsequently, the permafrost table has risen. Pollen 

studies (Rampton, 1971) also indicate a major change of 

climate 10,000 years ago. 

The vegetation changes in the Holocene in Alaska 

reflect many local differences. In some localities spruce 

appears to have returned before alder; in others, alder is 

the vanguard. A thermal maxim urn is recorded by vegetation changes in some areas and not in others. For 

example, at Onion Portage, Schweger (1971) reported 

no record of a thermal maximum but a rather gradual 

change from tundra vegetation to spruce cover. Further 

north, pollen work at Barrow does not demonstrate a 

thermal maximum, possibly because of an incomplete 

record. However, support for the advance of alder north 

of the Brooks Range in what might have been thermal 

maximum time is from alder leaves 5,650 years old 

preserved in the frozen ground in the Killik valley (Tedrow and Walton, 1964). Alder does not grow in the 

Killik valley today where these ancient leaves were 

recovered. 

A record from Chandler Lake in the Brooks Range 

(Livingstone 1955, 1957) supports the presence of a 

thermal maximum and indicates that an herbaceous 

tundra was present 8,300 years ago, but at 7,500 years 

ago dwarf birch tundra became common. About 5,800 

years ago, an alder maximum occurred which Livingstone thought was climatically related to the thermal 

maximum. To the south, on St. Paul Island of the 

Pribilof Islands, Colinvaux (1967c) noted that the pollen record shows that the vegetation similar to the present has existed for the last 9,000 years. In southeastern 

Alaska 10,000-8,000 years ago, pine was present (table 

3), but from 8,000 to 3,500 years ago Sitka spruce and 

hemlock predominated (Heusser, 1960). 

As in interglaciations before, the return of the forest 

to central and western Alaska was the most dramatic 

change in the vegetation in that part of the State. A 

controversy exists as to whether the exact time when it 

returned was 10,000 or 8,000 years ago. However, early 

in Holocene time the central and near western part of 

the State was indeed forested, and through Holocene 

time the forest boundary has evidently oscillated, especially on the north side of the Brooks Range and in the 

central and western Seward Peninsula. Hopkins (1972) 

believed that the Alaskan summers in the western part 

of the State are at present becoming warmer, and the 

greatest expansion of forests since the early Holocene 

warm interval appears to be happening now in northwestern Alaska. 
122 QUATERNARY GEOLOGY OF ALASKA 

Therefore, it is apparent that in some areas the vegetation type present today was essentially established 

within 1,000 or 2,000 years after the Holocene began, 

while in other areas, the modern vegetation dates back 

to a period immediately after the thermal maximum, 

only a few thousand years ago. 

In addition to the advance of glaciers in the last 3,000 

years, it should be noted that ~ock glaciers were active 

in the Alaska Range 4,000-2,000 years ago as well as 

during, another cold period that occurred perhaps 

within the last 1,000 years (Wahrhaftig and Cox, 1959). 

The permafrost table rose in central and western 

Alaska since the warming of the early part of the 

Holocene. The advance of glaciers and rock glaciers and 

the rise in the permafrost table all point to a cooling of 

the climate in the last 3,000 years. 

For the last 100 or 200 years, glaciers throughout 

Alaska have been rapidly retreating, and from a study 

ofthermal records of deep permafrost near Barrow, it is 

evident that the annual ground surface temperature 

has increased about 4° since 1850 and half of this since 

1930 (Lachenbruch and Brewer, 1962). Further warming was substantiated by examination of detailed 

weather records from the 1800's (Hamilton, 1965a). 

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A 

Page 

Accumulation area ratio ---------------- 27, 30, 104 

Adak Island __ ------------ --- -- -- ------- _____ ___ 35 

Alapah Mountain Glaciation -------------------- 33 

Alaska Peninsula, climate -------------------- 4, 111 flora ___ ______ ___ ____________________________ 87 

glacial geology ---------------- 21, 115, 116, 118 

permafrost _______ ___________________________ 46 

physiographic area ---------- --------------- - 2 

tectonic activity ---------------------------- 31 

volcanic activity ----------- ___ ______________ 11 

Alaska Range , climate __________ 4, 105, 106, 112, 119 

fluvial deposits -------------------------- 67, 68 

glacial geology ___________ ______ ____ ___ ______ 7 

Holocene -------------------------- 34, 122 

Illinoian ------------------ -- 18, 19, 21, 116 

Pleistocene ____________________ 17, 114, 115 

present ___ _ _ _ __ _ __ _ ___ _ __ _ ___ _ _ _ _ __ _ _ _ _ 28 

Wisconsinan ------------------ 24, 118, 120 

glacial stratigraphy -------------------- 8, 21, 25 

periglacial deposits ---------------------- 64, 66 permafrost ___________________ __ __________ ___ 53 

physiographic area _________________________ _ 

precipitation _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ ___ _ ___ __ _ _ __ _ 29 

Alaskan Glaciation ----------------- ------------- 34 

Alatna Glaciation ----------------- ------------- 25 Alder _____________ ____________________________ _ 81 

Aleutian Islands, archaeology __________________ 9 

climatic zone -------------------------------- 4 eolian deposits ________________ ________ ______ 35 

fauna ______ ---____________ _____ ___ ________ _ 103 

flora __ ______ __ _____ ___ _____________________ _ 82 

marine deposits -- -------------------- 74, 76, 77 

physiographic area -------------------------- 2 

volcanic activity __________________________ __ 11 

Aleutian Range ____ _______ ____ ____ _ 2, 21, 24, 79, 118 

Allakaket area _ _ __ _ _ _ _ __ _ __ _ __ _ ___ _ __ _ ____ _ _ ____ 74 

Alluvium -------------------------------- 67, 68, 71 

Altiplanation terraces ____ 2, 11, 61, 104, 106, 109, 115 

Amchitka Island ------------------ 21, 103; 106, 116 

Amphitheater Mountains ____________________ 64, 109 

Anaktuvuk Pass ---------------- ---- 25, 28, 32, 111 

Anangula Island ------------------------------ 9, 79 

Anchorage area ---------------------- 20, 25, 77, 79 

Andesite _____ __________________ __________ _______ 11 

Aniakchak caldera ------------------------------ 11 

Anivik Lake Stade ------------------------------ 32 

Anuktuvuk Pass - ------------------------------- 64 

Anvilian transgression ____________ 17, 76, 90,105,115 

Archaeology __ ______ ___ __ ____ ______ __ ____ ____ ___ 9 

Arctic Basin -------------------------- 105, 113, 117 

Arctic Coastal Plain, eolian deposits ___________ 34, 37 

fauna ----- ------------------------- 92, 93, 103 

flora ____ __ __ __ ______________________________ 85 

fluvial deposits ------------------------------ 70 

marine deposits -------------------------- 74, 76 

periglacial deposits -------------------------- 65 permafrost ____ ______________________________ 49 

physiography---------------_________________ 2 

Arctic Foothills ____________________________ __ ____ 70 

Arctic Slope ------------------------------ 10, 40, 70 

Aspen -------------- ---- ------------------------ 81 Auriferous gravel ________ ____ __ __ __ 70, 105, 106, 114 

B 

Bacteria _______________________________ __ ___ ___ 91 

Baldwin Peninsula ___ _________________ ___ _ 76, 85,87 

Banner Creek area- ----------------------------- 93 

INDEX 

[Italic page numbers indicate major references] 

Page 

Barrow area, climate__ __________________ 111,112,122 

eolian deposits ___ __ __ ___ ____ ____ __ _______ ___ 40 

fauna -------------------------------------- 91 

marine deposits _ --------------------- ______ 78 

permafrost ___ _______ __ 44, 46, 47, 49, 52, 53, 59 

Basalt _ __ _ ___ _ _ _ _ ___ __ _ __ _ __ _ __ _ _ _ _ __ ___ _ _ _ _ ___ _ 11 

Beaufort Sea area ------------------------------ 56 Bendeleben Mountains ____________ _____ ________ _ 114 

Bering-Chukchi platform ______________ 2, 78, 90, 92 

Bering land bridge, fauna ---------------- 14, 90, 121 

flora _________ ___ __ ______________________ 85, 87 

glacial geology ---------------------------- 116 

history- __ ________ _____________________ _ 78, 114 

Bering Sea area ---------------------- 106, 117, 119 

Bering shelf ______ _____ ___________________ 18, 21, 40 

Bering Strait area __ ______ ______ 18, 19, 105, 118, 121 

Beringian transgression, fauna ________________ 17,90 

flora ------------------------------ 82, 105, 114 

marine deposits ------------- --------------- 74 Bethel area _______ ________ ____ __ ___ ____ ___ ____ _ 66 

Bethel Basin ------ ------------------------------ 70 

Big Delta area, climate ------------------------ 109 

eolian deposits _________ ____ __ ___ _____ _ 35, 37,39 

fluvial deposits _____ _____________________ ___ _ 67 

permafrost ____ _____ _____ ________ ____ _____ ___ 55 

Birch ___________ _____ _______________ __ __ _____ __ 83 

Birch Creek area --------------------- ----------- 67 

Black Diamond Hill ---------------------------- 37 

Black Rapids Glacier---------------------------- Block streams _____ ________________________ _____ 61 

Blying Sound area ------------------- ----------- 31 

Bodenberg Butte ___ ___ ____________ ________ __ ____ 42 

Bog Flats _____ ___________ __________________ ____ 10 

Bogoslof Island ____ ______ ______ ----- ---------- ___ 11 

Bootlegger Cove Clay --------- --- --- ---- - 24, 25, 73 

Bristol Bay area , climate ___________ _____ ____ ____ 109 

eolian deposits ______________ _______ _________ 35 

glacial geology -------------------------- 18,21 

permafrost __________________ ------------ 53, 55 

Brooks Lake area ___ ___ ___________ ________ _______ 79 

Brooks Range, climate ---------- ---- 4, 107, 111 , 112 

flora ------------------------------ 86, 118, 121 

fluvial deposits -------------------------- 67,69 

glacial geology ------------------------------ 7 

Holocene -- ------------------------ 32, 121 

Illinoian -- ---------------------- 18, 21, 116 

Pleistocene ------------------------ 17, 115 

present ______ _____ __ __ ----------------- 28 

Wisconsinan ---------------- 24, 25, 30, 118 

glacial stratigraphy -------------- ----- - 8, 9, 25 

lacustrine deposits -------------------------- 74 permafrost ______ __ _____________________ _____ 46 

physiographic area -------------------------- 2 

Brown, Jerry, quoted ---------------------------- 59 

Browne Glaciation ------------------ 17, 18, 105, 113 

Buried ice ___ ________ -------- ------------------ 49 

c 

California Creek area _______ _____ ________________ 76 

Campus site (archaeological) ------------------ 9, 10 

Cape Deceit, climate __________ ______ ___ __ ___ ___ _ 105 

eolian deposits ____________ ______ ____ ___ _____ 40 

fauna ---------------------------------- 91,93 

flora _____ _____ 82, 83, 84, 85, 115, 116, 117, 118 

permafrost ____ ________ __________________ ____ 55 

Pliocene-Pleistocene boundary ___________ ____ _ 15 

Cape Deceit Formation ------------------ 82, 93, 115 

Cape Denbigh -------------------- -------------- 63 

Cape Espenberg -------------------------- ------ 79 

Page 

Cape Fairweather ___ ___ __________ ____ ------ __ __ 18 

Cape Krusenstern __ _ _ _ _ __ _ _ _ _ __ _ _ _ __ _ _ _ _ _ __ _ _ _ _ 113 

Cape Prince of Wales---------- - ------ ----------- 76 

Cape St. Elias ----------------------- --- 16, 24, 118 Cape Simpson _________ ____________ ___ ________ 46,47 

Cape Spencer ______ ____ -------------------------- 16 

Cape Thompson ------------------ -------------- 112 

Caribou Hills Glaciation-------------- -- 18, 106, 115 

Carson, C. E., quoted----- ---------------~------- 40 Cathedral Bluffs ______ ____ _____ __ _________ ____ __ 67 

Cave-off Cliffs ___ _ --------------------- __ ____ ___ 89 Caverns _____ ______ __________________ ______ ___ __ 65 

Cedar _____________ ______ ___ ________ _______ ___ __ 81 

Cenotaph Island ___ __ __ _____ _______ _____ ________ 105 

Cenozoic history __ _______ _ ---------- ----- ____ ___ 113 

Ch:;.gvan Bay area ------------- ----------- 8, 24,25 

Chagvan Glaciation _______ _______ ____________ ____ 25 

Chamberlin Glacier ___ _______ __ ___ ---- -------- ___ 28 

Chandalar Valley _____ __ __ __ ______ __________ ___ __ 93 

Chandler Lake area -------------------- 86, 87, 121 Chatanika River area _________________ ___ ______ __ 79 

Chena River area --------------- --------------- 101 Chicken area _____ _____ _____ _____ ___ _____ __ _____ _ 92 

Chitina area ______________ ____ ___ __________ ___ 40, 88 

Chugach Mountains ---------------------- 16, 32,64 

Chuginadak Island area ____ _____ _____ ___ ____ ___ __ 11 

Chukchi Sea area ______________ _______ ___ 18, 91, 106 

Chukotka Peninsula ___ ______________________ _ 18,77 

Cirques ------- ----------------------- 19, 25, 30,31 

Clay ___________ _______ ____ ____ ________ 72, 73, 76,77 

Cleary Creek area ------------------------------ 95 Cliffs ___________ __ ____ ____ ____________ _________ 61 

Climate __ __________ ______ ______ __ 2, 52, 53,103, 113 

Holocene ______ ____ ______________ ______ ____ 121 

Illinoian ___ ------------------------------- 117 

relation to insects - ------------------------- 91 

relation to mammoths' deaths ------------ -- 101 

relation to vertebrate extinction _________ ___ 102 

Sangamon _ __ _ _ _ _ _ _ _ __ _ __ _ __ _ __ __ _ _ _ _ __ _ _ _ 118 

Wisconsinan _ _ _ __ _ _ _ _ __ _ __ _ _ _ _ __ _ _ _ _ _ _ ___ _ 119 

Climatic snowline, defined ------ --------- -- ----- 26 

Colville River area ___________ _________ ______ 74, 119 

Colville River delta ____ _____ _____ _______ __ _______ 70 

Conductivity of permafrost ---------------------- 60 

Cook Inlet area, climate ------------ 4, 105, 106, 119 

glacial geology ______ __ ____ __ 18, 19, 24, 114, 115 

glacial stratigraphy __________ __________ ______ 21 

lacustrine deposits ----------------- --- ------ 73 

precipitation _____ _____ ______ __ ____ ___ ------- 29 

Copper River Basin, eolian deposits ______ ____ 35,40 

faur_a ___ ____ ______ ___ _____ _____________ ____ 88 

glacial geology---- ---------------------- 24, 118 glacial stratigraphy ____________ ___ ______ ___ __ 25 

lacustrine deposits ------- -- ----------------- 72 

permafrost __ ___ ____ ______________ ------- 47, 53 

Corwin-Utukok area ---------------------------- 70 

Council area --------- ------------- ------------ 110 

Cripple Creek area------------------- ----------- 93 

Cripple Creek Sump area -------------- --- --- 93, 95 

D 

Darling Creek Glaciation - -- ----------- ------ -- 115 

Dating, archaeological --c--------------------- 9, 10 

fluvial deposits ------- -------------- ---- ----- 68 

glacial _____ ___ ______ ____________ ___ ______ ___ 9 

Holocene Glaciations ------ --------- -- --- 32, 34 

ice wedge --------------- ------------- - ----- 53 

Illinoian Glaciation------------------ -------- 19 

141 
142 

Dating-Continued Page 

moraines, glacial geology of 

Alaska related elsewhere - ----------------- 15 pingos __ __ _ ___ _ _ __ __ __ _ __ _ __ _ __ _ _ _ _ _ _ _ _ _ __ _ _ 59 

Pliocene-Pleistocene boundary __ ________ __ 14, 15 

volcanic activity ----- ----------------------- 11 

volcanic ash -------------- - - ------------ 78, 81 

Wisconsinan Glaciation ------------- -- ------- 24 

Dawson Cut -------------------------------- 83, 85 Dawson Cut Muck _____ ___ _________ __________ ___ 106 

Deering area ------- ------------------------- 40, 82 

Deering Formation ------------------------- ----- 83 

DeLong Mountains ---------------------------- 119 

Delta Glaciation --------- ------------------- 19, 21 Delta Junction area __________ _____ _____ ___ _______ 28 

Delta River area, eolian deposits ______________ 40,42 

fauna __ ________________ ___ _________________ 88 

glacial geology __________________ 17, 25,115,117 

volcanic ash deposits ----- - ------------------ 80 

Denbigh Flint site (archaeological)__ _______ _______ 9 

Dendrochronology __ __ ____ _____ __ ____ ______ _____ 34 

Devil Mountain - -------- ----------------------- 79 

Dome Creek area ---------------------- 99, 100, 101 Donnelly Glaciation _____ ____ ______ ______ _____ 19,25 

Donnelly Ridge site (archaeological) _____ ______ _ 9, 10 

Drift ----- ------------------------- 17, 18 , 19, 21, 25 

Dry Creek Glaciation --- ------------- -- 18, 106, 115 

Dust -- ____ _____ __ __ __ __ ___ _________ _________ __ __ 2 

E 

Earthquake, effect on glaciers - -------------------

effect on tectonic study - -------------------- - 11 

EinahnUhtan transgression ______ 17, 76, 91. 106, 116 

Eklutna Glaciation ---------------------- 18, 19,20 

Elephant Point_ ___ ___ _____ ________ ______ 5, 9, 51, 91 

Endicott Mountains ---------------------------- 119 

Engineer Creek - - --- - -------------------------- 83 

Eolian deposits----------- ------- 2, 34 , 109, 110, 119 

Equilibrium line altitude -------------------- 27,30 

Equilibrium line, defined - ----------------------- 26 

Eschscholtz Bay area ------------------ 5, 51 , 91; 108 

Ester Ash Bed ----------- ----------------------- 79 

Eva Creek area, fauna---------------------- 91, 101 

flora - -------------------- - ---------- 83, 85, 86 

permafrost ----------- - ------------------ 53, 60 

Extent of report area ---- - ------------------- ---- 2 

Extinction of vertebrates _____ ______ _________ ___ _ 102 

F 

Fairbanks area, climate 106, 107, 108, 110,112,119, 121 

eolian deposits-------------------- 35, 39, 40, 42 

fauna -------- 91, 92, 93, 95, 97, 98, 100, 101 , 103 

flora - -------------- - 83, 84, 85, 86, 87, 117, 120 

fluvial deposits ------------------------------ 71 

glacial geology -------------------- 109, 115, 118 

nonglacial deposits -------------------------- 9 

periglacial deposits - ----------- ------ 62, 63, 65 permafrost_ _____________ __ ___ ____ _ 47, 48, 53, 59 

volcanic ash deposits - ----------------------- 79 

Fairbanks Loess - --- - ------------ - ----------- 39, 42 

Fan Mountain Glaciation------------------------ 33 

Farewell area - ------------------------------ --- 68 Faulting ___ ____ ______ ___ ________ ___ ________ _____ 11 

Fauna ___ ______ ________ ______ ____ _______________ 88 

Illinoian _ __ ___ _ ____ _ ___ _ _ __ __ __ _ _ ___ __ _ _ _ _ 117 

Pleistocene _ ____ _ __ __ __ _ __ ____ _ _ _ ___ _ _ _ ___ _ 115 

Pliocene-Pleistocene boundary __ ___ ______ _____ 14 

Wisconsinan __ ___ _ __ _ _ __ _ __ ___ _ _ __ ___ _ __ _ _ 120 

F.ir ___ ___ ____ _______ __ _________ ___________ _____ 81 

Firn lin,e, defined ------ -- ------------------------ 27 

Flood plains-------------------------------- 68, 120 

Flora ----- ------------ -- --------- ___ _______ 81 , 104 

Holocene - ---- ------- -------------- ---- 111 , 121 

Illinoian - --------- -------------------- 107, 117 

Pleistocene ____ __ _ _ __ _ ___ __ _ _ __ ____ __ _ _ _ ___ 115 

Pliocene-Pleistocene boundary __________ ______ 15 

post-Wisconsinan ____ _________ _______________ 86 

relation to fauna ------------ -------------- 102 

Sangamon --------- - ------------------ 107, 118 

INDEX 

Flora-Continued Page 

Tertiary - ---- ------- -- ------------------- - 114 

Wisconsinan --- ---------------------- - 110, 120 

Yarmouth______________________ __ __________ 116 

Fluvial deposits -------------- ---------------- 2, 67 

Fort Yukon area ---------------------------- 67, 71 

Fourth Beach ---------------------------------- 76 

Fossils: 

Alces --- ------------ --------------- 93, 97, 117 

Alder (Alnus) ___ ___ 81, 82, 83, 84, 85, 86, 87, 107 

111, 120, 121 

Anodonta beringiana _ ----------------------- 89 

Aspen ______ ---- ---------- -------------- 81, 107 Astarte ______ __ ____________________________ 11 

leffingwelli . ______ ________ __ _ -- ____ ------ 90 

Bacteria ______ ________________ -------------- 91 

Bear ___ . ___ ___ ___ . ___ ____ ___ __ _______________ 92 

Beaver ___ ____ . ________________________ 97, 101 

Beech (Fagus) -------------------- 104, 105, 113 

Beetles ___ __________ _____ __ _________ _______ 91 

Betula nana -------------------------------- 83 

Birch (Betula) 82, 83, 85, 86, 87, 105, 107, 114, 117, 

118, 121 

Bird remains _________ --------------------- 103 

Bison 9, 42, 92 , 93, 95, 97, 98, 101 , 102, 110,117,120 

Bison bison ------------------------ ____ ____ 101 

priscus _______________ ___________________ 97 

crassicornts -------------------------- 93 

(Superbison ) crassicornis ---------------- 95 

(Superbison ) sp __________________________ 93 

Bootherium ------------------------ 93, 98, 117 Bas _________________ ____ ________________ ___ 95 

Bovid ______________________ __________ ______ 97 

Callorhinus sp ---------------------------- 103 

Canis ---------------------------------- 93, 115 

Carcasses -------------------- 98, 108, 110, 120 

Cardita (Cyclocardia ) subcrassidens __________ 91 

Caribou -------------------------------- 92, 98 Cat ______ _______________________________ ___ 92 

Ceruus -------------------------------- 93, 115 

Chlamys ___ -------------- ___ ___ _____ ___ _____ 14 

plafkeri -------------------------------- 14 

(Leochlamys) tugidakensis ---------------- 14 

pseudislandica plafkeri ------------------ 14 

Citellus undulatus __________________ 86, 97, 101 

Clethrionomys sp -------------------- -------- 97 

Cotton grass -------------------------------- 83 

Cottonwood -- ------------------------ ------ 120 

Deer -------------------------------------- 115 Diatoms _________ ______________ ______ __ _____ 88 

Dicrostonyx ___ ------------------------- 93, 117 

torquatus ------------------ ------ 86, 93, 97 

Discus cronkhitei ---------------------------- 88 

Elphidium orogonese ------------------------ 70 

Equisetum ------------------------------ 86, 120 

Equus ------------------------------ 93, 97, 115 

alaskae -------------------------------- 95 Eriphorum ______ ___ _______ _____ ____ ____ _____ 83 

Euconulus fuluus alaskensis ____ ______________ 88 

Eumetopias sp _ _ _ _ _ _ __ _ _ _ _ ___ _ __ _ _ _ _ _ _ _ _ _ __ _ 103 

Felis (Lynx ) lynx ---------------------------- 92 

Fir (Abies) ------------------------------ 81 , 82 

Fish -------------------------- 97, 103, 107, 118 

Foraminifers 14, 17, 70, 73, 77, 90, 104, 106, 113 

Gastroliths _ _ _ __ __ ___ __ _ _ _ _ _ _ __ ___ _ __ _ ___ __ 103 

Gastropods ____ _____ _____ ____ _______ __ ____ ___ 88 

Goats _______________ ______ ___ _____ __ ________ 117 

Gramineae __ _ _ _ _ _ __ _ ___ _ _ _ ___ ___ _ __ __ ___ __ _ _ _ 84 

Gyraulus paruus ------------------------ 88,89 

Helisoma subcrenatum ---- ------------------ 88 

Hemlock (Tsuga) ___ ______ _ 82, 87, 105, 114, 121 

Hickory (Carya ) ---------------------------- 82 

Horse ---------- 42, 92, 95, 98, 102, 110, 117, 120 

Hyalinea baltica ---------------- ____________ 14 

Insects ____ _____ __________________________ ___ 91 

Invertebrates _________ _____ _____ ____ _________ 88 

Larch (Larix ) ------------------------ 81, 82, 83 

Lemming-------------------- 110,115,117,120 

Lemmus -------------- ------------------ 93, 115 

siberius ______ _________________ _______ 86, 97 

Lepus sp - ---------------- ------------------- 97 

Fossils-Continued Page 

Littorina littorea ____________ __ __ _______ _____ 118 

Lynx _ _ _ _ __ _ ___ _ _ __ _ _ _ _ __ _ __ _ _ __ _ __ ___ _ ___ _ 98 

Mmrnnoth 42, 92, 93, 95, 98,101 , 102, 110,117, 120 

Mammuthus primigenius -------------------- 95 

Microtus ----- ------- ---------------- 93, 97, 115 

gregalis ----------- ---------- ----------- 97 miurus ________ ________________ ___________ 97 

xanthognathus ____ ___ _ _ _ _ _ _ _ ___ _ __ _ __ _ 101 

Mollusks _______________________ ___________ __ 88 

Cenozoic ---------------- 113, 114, 115, 118 

climate ------------------ 104, 105, 106, 107 loess ___________ ___ ____ ___ ____ ___________ 39 

marine deposits -------------- 10, 74, 76,77 

Pleistocene __ __ _____________________ ___ __ 17 

Pliocene-Pleistocene boundary ------ ------ 14 

Moose ---------------------------- - - 92, 98, 101 

Moss ____ _____ --------------- ----- _____ 86, 120 

Musk ox --------------- ____________ 92, 95, 98 

Mya japonica ______________ ______ ______ ______ 91 

Naticajanthostoma _______________ _ 105, 115, 118 

Neptunea ___ _ _ __ _ _ __ _ __ _ __ ___ _ ___ _ __ _ __ _ __ _ 14 

heros mesleri ---- --------------- --------- 90 

Ochotona ------------------------------ 93, 115 Odobenus ____ _ __ _ ___ _ __ _ _ _ _ _ _ _ ___ _ ___ __ _ _ __ _ 103 

Ostracodes ______________________________ 77, 90 

Ouibos _____ __ ------------------------- 93, 117 

Ouis ----------------- ______ ------------- 93, 117 

niuicola ------------------ ------------- - 86 

Panthera atrox ______ --------------- ________ _ 92 

Patinopecten (Fortipecten ) hallae. -------------- 90 

Pelecypods _______________________ ___________ 88 

Phoca vital ina _____ ____ ---------- ----------- 103 

Pholadidea penita -------------------------- 118 

Pine (Pinus)__ ______ __ ______ 82, 83, 105, 114, 121 

Pisidium casertnum ____ ____ ______ ___________ _ 88 

lilljeborgii ------------------------------ 89 sp ___ _ _ _ _ __ _ _ __ _ _____ _ __ _ _ _ _ _ _ __ _ _ _ __ _ __ 89 

Pliomys -------------------------------- 93, 115 

Poplar (Populus! _______ _ 83, 86, 87, 107, 111 , 120 

Portlandia ---------------------------- 105, 114 arctica _ __ _ __ __ _ __ ____ __ _ __ __ __ _ __ __ __ _ __ 91 

Potentilla sp. _ ___ _ _ __ __ _ _ ____ _ ___ ___ ___ _ __ _ _ 101 

Praeovibos -------------------------- 93, 98, 117 

Predicrostonyx hopkinsi ___________________ 93, 115 

Proboscidea ---- ---------------------------- 97 

Pusa hispida ---------- -------------------- 103 

Rangifer ________________________ 93, 97, 115, 117 

Ranunculus hyperboreus __________ __________ 101 

Rhinoceros - - ------------------------------ 115 

Sage (Artemisia ) ________ 83, 84, 85, 110, 117, 120 

Saiga -------------------------- 92, 93, 117, 118 Sedge __ ____ ____ _____ _______________ ___ _____ 86 

Sheep ------------------------ 86, 110, 117, 120 

Smilodon sp -------------------------------- 92 

Spermophilus (Spermophilus ) undulatus ______ 97 

Sphaerium tenue ---------- ------------------ 88 

Spruce (Picea) 81 , 82, 83, 85, 86, 87, 88, 105, 107. 

110, 114, 115, 116, 118, 120, 121 

Squirrels ---------------------- 98, 110, 117, 120 

Stagnicola palustris _ __ _ _ __ _ _ _ __ ___ _ _ ____ _ __ _ _ 88 

Steller's sea cGw - --------------- --------- 77, 103 

Succinea auara ____ __ _______ ____ _____ _______ _ 88 

strigata ------------------ -------------- 88 

Symbos ---------------------------- 93, 98, 117 Synaptomys ____ _____ ______ ____ _____________ 97 

Turborotalia pachyderma __ _____ ___ 17, 104, 113 

Turritella ---------------------------- 105, 114 

Valvata helicoidea ------------------- _______ 89 

lewisi ------------------------------ 88, 89 

Vertebrates ------------------ 9, 42, 86, 91 , 117 

Walrus tusk____ _____ ________________ _____ ___ 103 

Whales ------------------------------------ 103 

Willow (Salix) -------------- 81, 84, 86, 111, 120 

Wolf ____ _____ ________ _______ ____ ___ _________ _ 92 

Frost action _ ~ _ _ __ _ _ _ _ _ __ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ 10, 43, 61 

Frost rubble _____ ----------------- ____ ____ ______ _ 114 

G 

Gakona area _____ _ ---------------- 73,88 
Page 

Galena area .. -------------- ______ -----·- ____ ___ 89 

Geobotanical periglacial features _____ _____ _ . _ _ _ _ 66 

Geography ------ ---- -- ---- ------------------- --- 2 Gilmore Creek area __________ _______ _________ __ __ 93 

Glacial geology --- --------- -- 2, 15 , 30, 113, 116, 121 

Glacial stratigraphy ----------------··-- ---- --- 7, 19 

Glaciation limit, defined ________________ ____ __ 27 

Glacier Bay area ____ _______ ____ . ____________ 34, 79 

Glaciology ·------ _________ . ___ __ ___ __ _____ ____ __ 6 

Gold deposits ______________ ______ .. _. _____________ 74 

See also "Auriferous Gravel. " 

Gold Hill _______ _ -------··- -- _________ 40, 85, 93,95 

Goldstream Creek area _____________________ _____ 93 

Goodnews Bay area _______ __ ___ ______ ______ _ 85,87 

Grass --------- ---- --------------- 107, 110, 117, 120 GraveL ________ ___ _____ ________ ______ __ _ 68, 70, 105 

Ground ice _____ __ ----- - ------------------------- 48 

Gubik Formation __ _________ __ _________ 10, 70, 74,76 

Gulf of Alaska area, climate ________________ 104, 119 

fauna ____ __ ______________ ________________ __ 101 

glacial geology __ __ 17, 24, 34, 113, 114, 115, 118 

glacial stratigraphy ___ ___________ ___ ________ _ 7 

marine deposits __________________________ __ 10 

Pliocene-Pleistocene boundary ____________ 11, 14 

precipitation __ ___ _____________________ __ ___ _ 29 

tectonic activity --------------------------- - 31 

Gulkana area ------------------------- --- ------ 40 

Gulkana Glacier ___ - -- ---·---------- - ---- ------- 7 

H 

Healy Glaciation __ _______ _________ _____ ___ 18, 72 

Healy Lake ________________ _ ··--· __ _____________ 10 

Hemlock --------- ---- ---- ___________________ __ __ 81 

History of research ___ ___________ ____________ ____ 5 

Holitna lowland ___ _________ ----------- - ------ - 69 

Holocene ____ ___ __ ___ . _____ __ . _ 15,32, 101, 111, 121 

Hopkins, D. M., quoted ------------------------- - 14 

Hughes area -------- - ---· 62, 107, 108, 109 

Ice -- ----------- ·---------------- ----- 48, 114, 116 

Ice Island ___ __ ---------------- ___ ____________ 17 

Ice wedge casts - ----------------------- 53 , 107, 114 

Ice wedges ___ __ _ 10, 49, 104, 105, 106, 107, 109, 111, 

115, 116, 117. 119 

Icy Cape ___________________ _________ _______ 79, 81 

Ikpikpuk River area ___ ____ __ .. _______ ____ ___ __ __ 92 

Illinoian, climate ________ _________ . _____ ____ ___ 107 

fauna ___ ··--- __ __ _____ _______ .. _________ _____ _ 93 

flora _____ ___ . __ _______ __ ___ ___ ___ ________ ___ 83 

glaciation ----------- ------------- 15, 18 , 73, 83 

history ___________ _____________________ __ __ 116 

sand dunes __ __ ______ _______ ___ __ ________ ____ 35 

snowline __________________ ___ ____________ __ _ 34 

Imnachuk Formation _______ ·-----··- ------------- 83 

Imuruk Lake area, climate ________________ 106, 107 

eolian deposits __ __________ ___ ____ ________ ___ 39 

flora _______ _____ _______ ____ 83, 85, 87, 117, 118 

Indian Mountain, climate _________ 104, 107, 108, 109 

glacial geology ____________________ ____ _______ 30 

lacustrine deposits _____ _____ . _______ ____ ··- __ 74 

periglacial deposits ____ . _ -- ·· __ _ _ ____ __ ___ _ _ _ 62 

Inglutalik River area ______________________ __ ___ 103 

Innoko lowland _______________________________ ___ 69 

Intermediate Beach _________ __ .. ______________ __ __ 76 

Intermontane Plateaus ____________ __________ ____ _ 

Ipiutak site (archaeology) _____ -··- ---------------- 9 

Iron Creek Formation ____________________________ 82 

Iron Creek Glaciation .. _____ _______ 74, 76, 83, 105, 114 

Isabella Creek area ________________________________ 87 

Itikmalakpak Creek area ----------------------- 28 

Itkillik Glaciation _. _____ ________________ _____ 25, 32 

Iyatayet site (archaeological i __ . _. ___ _ _ _ _ _ _ ___ __ 9 

J 

Jarvis Creek area ------ --------- ----- -------- -- 80 

INDEX 

Page 

Johnson River area __ __ _____________ __ __ __ . 8, 21, 25 

Jumbo Dome -- ------ -··--·----- -- -- 18, 64, 107, 117 

climate ___ _______ ________________ _______ 107.117 

periglacial deposits -------- -----------····---· _ 64 

Juneau area _____ __ ------------------- --- ----·· 7, 89 

K 

Kala tag fault_ __ __ ___ __ ____________ ·------- _ __ 68 

Kantishna River area --------- -··----------- -· 35,36 

Kenai lowland __ ______ __ ·-------------------- - 74 

Kenai Mountains --- ------------------------- ____ 32 

Kenai Peninsula, flora ------------------------- - 88 

glacial geology --··------------------- -- 7, 33,34 

periglacial deposits- ------------------------- 66 

volcanic ash deposits ------------------------ 79 

Keno Hill ----- ----- -------------------- ------- - 47 Kettles __________ ______ ___________ ___________ __ 25 

Kigluaik Mountains - -- ------------ ----- ----··--- 24 

Kilbuck Mountains- - ---------------------- ------ 25 Killik valley __ ___ _______ __ __________ _____ ___ 86, 121 

Kivalina River area - ------------------------- 74, 90 

Knik Glaciation ---------------------- 19, 24, 25, 77 

Knik River area ------- ------ -------------··- 42, 117 

Kobuk River area, archaeology ----------------- - 10 

eolian deposits ---- ------ ------------- --- 35, 36 

flora ___ ____ ____ ___ ______ ---------------- ____ 87 

fluvial deposits-- ---------------------------- 69 

periglacial deposits---------------------··- -- - 63 

Kodiak Island -- ---- ---------------- 4, 17, 21, 79,81 

Kokolik River area ____ __ _______________ __ ____ 92, 103 

Kotzebuan transgression ______ 76, 83, 90, 93, 106, 116 

Kotzebue area ___ ___ ______ 52, 85, 107, 108, 118, 119 

Kotzebue Sound area, climate __________ 105, 106, 111 

eolian deposits _____ ____ ________ ________ ____ _ 40 

fauna _______ _____ ___ _________ 88, 89, 91, 93, 101 

flora ------ --------- -- ----------- 82, 83, 85, 120 

glacial geology ___ _______________ 18, 19,114, 116 

glacial stratigraphy ---- -- ----------- ----- 20,21 

marine deposits ---------------------- 10, 76, 77 

Koyokuk River area, eolian deposits ______ 35, 36, 119 

fluvial deposits -- - ------------------_______ _ 68 

glacial geology ---r---------------- - ------- 117 

lacustrine deposits --- ----------- --------··--- 74 

volcanic ash deposits ------------------------ 81 

Krusensternian transgression -------------------- 78 

Kuk River area --- ------- ---------------- -- 92, 103 

Kuskokwim River area, eolian deposits 35, 36, 39, 40 

fluvial deposits ------- ----------------------- 68 

glacial geology ---------------------------- 117 

lacustrine deposits ------------------------··- 71 

periglacial deposits - ----- -------------- ------ 66 

permafrost ---------------··-----··- _________ -·· 53 

volcanic ash deposits ----------------- ------ - 81 

Kuskokwim River delta __________________________ 70 

Kvichak Bay area ____ _ _____________ ___ 76 

L 

Lachenbruch, A. H., quoted _________________ 47, 48,51 

Lacustrine deposits ____ ______________ _____ _____ 2, 71 

Lake basins __ __ ______ ___________ _______________ 65 

Lake Cook -------- -- - ------- -------------- ------ _ 74 

Lake Minchumina - ----------------------- --- 68 

Lake Moody _____ __ _ ---------------------------- 72 

Lapse rate ---- ------------ ------------------- _ 108 Lava ___________ __ ____ _________________ ___ ___ . ___ 76 

Lichenometry _____ ___ _______ __ __ ______________ . 34 

Lillian Creek area ----------------------------- 93 

Little Port Walter --------------- ---------------

Lituya Bay area ---------------------------- 74, 105 Location __ _____ ___ __ ____ _______ __ __________ . _ __ 2 

Loess -------- 9,37, 104,107,109,110,117,118, 119 

Lost Chicken Creek area ------------- --------· - 92 

Lost River terrace __ _ 25 

M 

McCall Glacier----------------- - --------- ----- -· 28 

143 

Page 

McGrath area ____ __ ·--------------------------- 68 

Mackenzie River area __ __ ________________ 56, 66, 101 

MacLaren River area---------------------------- 64 

Malaspina Glacier --- ------ ------------------- 7, 34 

Manley Hot Springs area ------------- -- ---- - 39,67 

Marine deposits -- ------------------ 2, 10, 14, 34, 74 

Marine vertebrates __ ___ _______________________ 103 

Marshall area --- - ----- ------------------- -- --- - 62 

Martin Glacier ------ - - ----- ------- - -- -- - --- -- -- - 89 

Mass wasting - - ---··---------------------- 25, 43,62 

Matanuska Glacier ---- ---------------------- 34, 89 

Matanuska River area ___ ________ 24, 34, 37, 40,42 

Matuyama epoch - ----- - ----- -------------------- 76 

Middleton Island, climate --------------------- - 106 

glacial geology ------ -------------- -- 16, 17, 114 

marine deposits - ----------------- _____ ____ _ 74 

Pliocene-Pleistocene boundary ---------------- 14 

Middletonian transgression ---------------- ------ 76 

Modern snowline -------- ----------------- --- 27,34 

Monroeville Beach _____ __ ____ _____________ ------ 76 

Moraines _____ ____ _____ _____ ___ ______________ 19, 25 

Moses Point_ _____ ____ ____ ___________ _____ _____ _ 110 

Mount Cleveland - -------- --- -------------------- 11 

Mount Edgecumbe ------ --- - ---- ----- - -- -------- 79 

Mount Katmai --- --------------------------- 11, 79 

Mount McKinley National Park - - ---------------- 25 

Mount Natazhat --------- ---------------- ----··- - 80 

Mount St. Elias --- ------- ------ --- --- - --- --- --- 81 

Mount Susitna Glaciation -------------- 18, 105, 114 

Muck ___ _______ ______ ----------------------- 37,42 

Mudstone _________ _________________ ___________ _ 17 

Muldrow Glacier ------------------------------ _ 7 

N 

Naknek area ____ ___ ___ _ ------------------------ 87 

Napatuk Creek area ----------------------- 70 

Naptowne Glaciation··---------------- - 24, 25, 33, 77 

Nelson Island --- -- --- -------- -- ----~- ----- 103 

Nenana River area - ------------------ - 17, 25, 72, 93 

Nivation _______ _______________ ------------------ 61 

Noatak River valley ______ ______ ___ ______ _____ 69,74 

Nogahabara dune field --- ---- ------------- - -- --- 35 

Nome area, climate __ ____ ____ 105, 107, 108, 111, 119 

fauna ________ ______ __ ______ 90, 93, 103, 115, 118 

flora - ------- -- __ _____ __________ 82, 85, 87, 118 

glacial geology ------ ---- ------- --- -- - -- - ---- 19 

glacial stratigraphy ___ ____ __________________ _ 20 

marine deposits -- ---------------- 10, 74, 76, 77 

permafrost __ . __ ___ _________________________ _ 55 

Nome River Glaciation ______________ 19, 76, 77, 108 

North Slope, climate ______ ___________________ ___ 110 

flora ------ ----- -- - ---------------- 86, 117, 118 

glacial geology ______ __ -------------------- 117 

marine deposits ------ --------------------- - 74 

Northway area ____ ____ ____ __________ 36, 53, 108, 119 

Norton Bay area --- -- ----- ------ ------------- - 103 

Norton Sound area ------- ------------ ------- - -- - 9 Novarupta _____ _____ ____ ___ ___ _______ ________ __ 79 

Nunivak Island --------- ---------- ------- 11, 15, 88 Nushagak Bay area ______ ___________________ _____ 76 

0 

Ogotoruk Creek area, climate ------ ------------ 112 

flora _________ ____ _ __ _______________ 85, 87,120 

permafrost ------ --- -------- --------- 47, 48,52 

Okmok caldera --- ------------------------------ - 11 

Old Crow Flats ___ ___ __ ------------------------- - 72 

Onion Portage area ______ ________ 10, 63, 87, 111,121 

Orographic snowline, defined ----------- ---- -- - -- 27 

Outwash fans ___ ___ _____ _________________ __ 109, 120 

p 

Pacific Mountain System ------------- 2 

Paleomagnetic studies _____ ________________ _____ 11 

Palmer area _______ _ --- --------------- 39, 40, 42, 88 

Palsas _ ·· ------ ______ ------------------- ----- 57, 66 
144 

Page 

Palynological studies ____ ___ __ __ _ __ _ __ _ ___ ___ ___ _ 9 

Patterned ground -------------------------- 104,109 

Paxson area _________________ ____ ____________ ___ 109 

Pelukian transgression ____ __________ 77, 91, 107, 118 

Periglacial deposits -------------------------- 43,61 

Periglacial studies _______________ _______________ 10 

Permafrost ____________________ ____ 2, 4, 43 , 44 , 104 

geochemistry ____ ___ -- ---------------------- 59 

Holocene ___ ___ ____________________ 111, 112, 121 

Illinoian -------------------------- 107, 116, 117 Pleistocene ________________________________ 115 

Sangamon --- ------------------------- 108, 118 

Wisconsinan __________ __ ______ _______ _ 109, 119 

Peters Glaciation --------- ----------------------- 26 

Physiography ______________________________ 2, 19,25 

Pine _____ __ _________________ ______________ ______ 81 

Pingos -------------------- ---------- ---- 10, 49, 56 

Pipeline construction ---------------------------- 73 

Platinum area ------------------------------ 25,70 

Pleistocene ____ _______ ______ _____ 16, 17, 81, 105, 114 

Pleistocene-Pliocene boundary ________ _____________ 11 

Point Barrow ________ ___ ___________ 74, 77, 85, 86, 87 

Point Hope ---------------------------- 9, 47, 48,52 

Point Lay - ------------------------------------- 103 

Pollen studies ---------------- 82, 102, 111, 117, 121 

Polygonal ground --------- ----------------- 49, 109 

Poplar ____ ____ _______ ___________________________ 81 

Porcupine River area __ __________ ________ 71, 72, 89 

Pore ice ------------------------------------ 48,49 

Precipitation ____ ____ __ ______ 28, 32, 34, 104, 110, 119 

Previous research_____ ___________________ ________ 5 

Pribiloflslands, eolian deposits __________ 37, 40, 119 

fauna _______ ___________________________ 91 , 92 

flora ___ ____ __ ___________________ ____ 83, 87, 121 

glacial geology- --------------------- 18, 19, 117 

marine deposits ______________________ 74, 76,77 

permafrost -------- ------------------------- - 55 

volcanic activity ---------------------------- 11 

Prince William Sound area ____________ 7, 24, 79, 118 

Prudhoe Bay ---------------- ---------------- 44, 46 

Puget Glacier ---------------------------------- 34 

R 

Rampart area ---------- ---------- -- - ------- --- - 88 

Ray Mountains___ ___ ____ ____________ ____ ___ __ ___ 8 

Ready Bullion Creek area ___ ________ _____ 53, 83,91 

Regional snowline, defined ____ ___ _______ __ __ ____ 27 

Riley Creek Glaciation _______ __ ___ _____ _____ __ __ 25 

Ripple marks_ _________________________ __ ___ _____ 73 

Rock glaciers ___ _______ 10, 61, 64, 109, 112, 120, 122 

Rocky Mountain System ------------------------ 2 

Rubble sheets ____________ ______ 61, 64, 107, 109, 120 

Ruby area ___ ______ ____ ____ __ ________ __ ____ _____ 71 

Russell Fiord ____ __ ____ ___ ________ ___ 16, 18, 24, 118 

s 

Sagavanirktok River area - ------------ - -------- 111 

St. Elias Range _____ ________ _________ 104, 113, 114 

St. George Island __ _____________ _ 19, 21, 40, 76, 114 

St. Lawrence Island, archaeology ---------------- 9 

climate ____ ________ ___ ______ __________ _ 106, 111 

fauna -- --------------- -- -- ---- ------ --- 92, 103 

flora -- ---- --- ------------- -------- 85, 118, 120 

glacial geology ______________________ 18, 30, 116 

marine deposits ---------------------------- 77 

St. Paul Island, climate __ ___ ___ _____ ___________ 106 

eolian deposits __ --------------------------- 37 

flora __________________ ___ _____ ______ 83, 87, 121 

glacial geology ___________________ ____ 116, 120 

marine deposits ___ _ __ _ _ _ _ ____ _ ___ _ _ __ _ __ _ __ 76 

paleomagnetic studies______ _____ __ ___________ 11 

Sand ___ __ ______ ____________________ 67, 68, 72, 73, 109 

Sand dunes _________________ ___ 35, 67, 104, 117, 119 

Sangamon, climate ---------------------------- 107 

fauna -------------------- ----------- --- 91, 101 flora ____ __ _____ _________ __ __________________ 84 

glacial stratigraphy ----- ------------- ---- 19,21 

history -------- ----------- ---- -------- - 15,118 

IND 

Page 

Scarps ____________ ___ _________ ___ ____ _____ _____ _ 61 

Schrader Glaciation _________ ______ ___ ____________ 26 

Selatna Glaciation _______________ __________ _____ 36 

Selawik Lake area ------------------------------ 19 

Seward ice field ------------------------ -------- 77 

Seward Peninsula, archaeology __________________ 9 

climate __ 4, 105, 106, 107, 108, 109, 110, 111, 121 

eolian deposits __________ ______ 35, 37, 39, 40, 119 

fauna __________________ 88, 89, 92, 95, 101 , 103 

flora ______ 83, 84, 85, 87, 114, 115, 116, 117, 121 

fluvial deposits _________________________ ----- 70 

glacial geology 18, 19, 21, 24, 25, 30, 114, 116, 118, 

120 

glacial stratigraphy _______________ __________ _ 25 

marine deposits ---------------------- 10, 74, 76 

periglacial deposits ---------------------- 63, 65 

permafrost ___________________________ __ _____ 52 

tectonism _ _ _ _ __ _ _ __ ___ _ __ __ __ ___ __ __ _ __ __ _ _ 11 

volcanic activity ---------------------- -- 11, 79 

Shaviovik River area --------------------- ------- 47 

Shaw Creek area ____________________________ 55, 106 

Sheep Creek area ______ ________________________ __ 83 

ShelikofStrait area ------------------------ 21, 118 

Silt --- ------- 9, 37, 42 , 67, 68, 71 , 73, 76, 77, 85, 107 

Sinkholes ______________________________________ 65 

Siruk Glaciation ________________________ ________ 25 

Skull Cliff ---------------------------- 74, 105, 115 

Skull Creek area ---------------- - -------------- - 18 

Snails ----------------------------- --------- 40, 70 

Snake River valley ----- --------------------- 77, 85 

Snowline, climate relationship ------ ------------ 104 

defined ______ _______________________ ___ ____ 27 

Illinoian ________________________ 21, 34, 107, 117 

Wisconsinan ___ _______ ____ 26, 34, 108, 110, 119 

Soils __________ _____ __________ ____ ____ _______ 19, 25 

Solifluction ______________ __________ 2, 10, 61 , 62, 120 

Solifluction deposits __ 71 , 104, 105, 106, 109, 114, 115 

Solomon area -------------------------------- 76,90 South Bight_ ______________________ _____ 77, 106, 116 

Spruce __________________ --- -------------- __ _____ 81 

Stratigraphy, glacia l ---------------------------- 7 

String bogs ___ ______________________ ___ _____ __ __ _ 66 

Submarine Beach _____ ______ ___ __ ___________ ____ _ 74 

Susitna River valley, glacial geology ______ __ 21, 115 

glaciation __________ _ -,-____________ _____ ___ _ 118 

lacustrine deposits ---i----------------------- 74 

periglacial deposits------- ---------- - --- ---- - 66 permafrost _____ _______ ___ ___ ___ __ ___________ 53 

T 

Taber ice ------------------- - ---------------- 48, 49 

Talkeetna Mountains ___ ___ __________ ____ ______ 2, 64 

Tanaga Island _ _ __ _ _ __ _ __ _ ___ _ __ _ __ _ __ _ __ _ _ _ _ _ _ _ 82 

Tanana area __ __ _____ ___ ___ __ ___ ______ ___ ___ ____ 88 

Tanana-Nowitna drainage area - -- --------------- 71 

Tanana River area, eolian deposits ___ _ 35, 36, 37, 40, 

42, 119 

flora ______ _________________ _____ _________ ___ 87 

fluvial deposits ___________________ ____ ___ ___ _ 67 

glacial geology ------------------------ 115, 117 

glacial stratigraphy___________________ ______ __ 8 

lacustrine deposits ------------------ -------- 72 

permafrost ____ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ __ ___ _ 55 

Tangle Lakes area ------- ----------- ----------- - 64 Tanya Stade __________________________________ __ 33 

Tectonism _______ ______________ _____________ 11 , 16 

Temperature --- -------------------- --------- 4, 104 

Holocene _________ ______ ____ __ ___ ______ 111 , 122 

ice wedges ______ ----------------- -- --- - ----- 53 

Illinoian ------------------------------ 107, 117 permafrost _________________ ___ ________ ____ __ 4 7 

Pleistocene-------------------------- - - 105, 115 present ___ -c _ _______ _ _ ___ _____ ___ _______ _ _ _ 28 

Sangamon ------- ------ - --- ----------- 108, 118 

Wisconsinan _____________ __ ___ 109, 110, 119, 120 

Yarmouth ---------------------------- 106, 116 

Terraces ------ ------ ------------------- - 11, 67, 106 

Tertiary ------- ---- ------------ ----------- 104,111 Tetlin area _____ ___ _____ __ ________ _____ _____ ___ __ 72 

Thaw lakes ------- ----------------------------- 10 

Page 

Thermokarst features _____________ _____ _____ ---- _ 65 

Third Beach ------------------- ------------- --- - 76 

Tillite - ------------- - - C- - ---- - ---------------- 7, 17 

Tofty area - ------- ------------ 63, 86, 88, 89, 92, 97 

Tok area ________ __ ____ __ ______ _________ _________ 36 

Toklat River area ______ ____ _____ __ ____ ___ ___ __ ___ 36 

Tonzona River area _____ __ ___ _______ ______ _______ 17 

Topography _ _ ___ _ ___ ___ ____ _ _ __ ___ ____ __ _ _ ____ _ 2 

Tors _______ __ ______ _____ ___ _______ __ ___ __ ____ ___ 61 

Tozitna River area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 65 

Trail Creek caves (archaeological) ------- -------- - 9 

Tree line ________ 84, 102, 104, 107, 110, 116, 117, 120 

Tree-ring studies _____ ______ ___ __________ __ __ 34, 112 

Trinity Islands ------------- -------- ---------- --- 17 

Tundra 81, 85,105,107,110,111, 114, 117, 118,120,121 

Tundra polygons ------------------------ --- ----- 49 

Tunnel Stade _______ ___ _____ -- -------- __ _________ 34 

Tustumena Stade ____ ______ ________ ___ ___________ 34 

u 

Umiat area - ------ -- --------- -------- 47, 86, 87, 111 

Umnak Island --------------------- ---------- --- 11 

Unalaska Island ----- -- - ------------- -- --- ----- - 92 

Utukok-Corwin area ---------------- -- ------- -- - 70 

Utukok River area ----- - ------------ ------------ 92 

v 

Vegetation. See "Flora." 

Ventifacts--- ------------------------ ------- 37, 104 

Volcanic activity _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 11 

Volcanic deposits ----------- ------ ------ --- 2, 9, 78 

w 

Weathering profiles --- - - --------------------- 19,25 

White River area __ __________ ________ ___ ___ ___ _ 7, 80 

White River Ash --- --- - ----- ---------------- 79, 80 

Wilber Creek area --------------------- ---- ----- 79 Willow ___ __ ______ ______ ___________________ ______ 81 

Wind ______ __ _____ ____ _______ 109, 110, 111, 117, 119 

Wisconsinan, climate --- -------------------- --- 108 

fauna ___ __________ -------- --- ________ ____ __ 95 

flora ______ __ ____ __ ___ _________ _______ ___ __ __ 85 

glaciers----- ---- -------------------- - 15,21, 73 history _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 118 

sand dunes __ ____ ___ ____________ ____ ____ ___ __ 36 

snowline - ------ ---- -------- ---------- -- - 30, 34 

tectonic activity ---------------------------- 31 

WolfCreek Range --------------- ---- --------- -- 10 

Wolverine Glacier ------------------- - -------- -- 7 

Woronzofian transgression ____________ __ 24, 77, 120 

Wrangell Mountains, climate ____ ________ 4, 104, 113 

glacial geology--- --- --- - ---- 9, 17, 114, 115, 119 

glacial stratigraphy------ -----_______________ 7 

periglacial deposits------------------------- - 64 permafrost __ __ _____ _____ ____________ ________ 4 7 

physiographic area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 

volcanic ash deposits ________ ________ ____ ____ 80 

y 

Yakataga Formation 14, 16, 17, 74, 104, 113 

Yakutat area -------------------------------- 16,35 

Yarmouth ------------------ - - ----- - 83 , 91 , 106, 116 

York Mountains ------- -------------------- -- - 8, 24 

York terrace __ __ _ _ _ __ _ __ __ _ _ _ _ _ __ __ _ ____ ____ _ __ _ 11 

Yukon Flats, eolian deposits ___ _________ __ ____ 37,40 

fauna ------------ ------------------------- - 88 flora __________ ________________ _______________ 82 

fluvial deposits --------------- -------- ------- 67 

lacustrine deposits ---------------------- 71, 72 

periglacial deposits- ------------------------- 65 

Yukon-Koyukuk area---- - --------- ---------- 68, 89 

Yukon-Kuskokwim Delta area ___ ___ 4, 53, 57, 66, 78 

Yukon River area, eolian deposits __ 35, 37, 40, 42, 119 

fauna _ _ _ _ __ _ ___ __ _ __ __ _ _ __ _ __ _ _ __ _ __ _ __ _ _ _ _ 88 
Page 

Yukon River area-Continued 

fluvial deposits --------- ------------- 67, 68, 70 

glacial geology __________________________ __ 117 

volcanic ash deposits ------------------------ 80 

*GPO 790•115-1977 

INDEX 

Page 

Yukon-Tanana Upland, climate ____________ ____ 109 

eolian deposits ____ c ______ -------------- _____ 40 

fauna ______ ___________________ _____________ 92 

flora _______ ____ _____________________________ 81 

145 

Page 

Yukon-Tanana Upland-Continued 

fluvial deposits ---------------------- 67, 68, 70 

periglacial deposits ---------------- --- --- 62, 63 

volcanic ash deposits ------------------------ 79