Hoof Hill

CHAIX HILLS

Tyndall Glacier
Hoof Hill

CHAIX HILLS

Tyndall Glacier
J G
J G
McArthur Peak

Logan Glacier

Chitina Glacier

Mt. Logan King Peak

Baldwin Glacier
McArthur Peak

Logan Glacier

Chitina Glacier

Mt. Logan King Peak

Baldwin Glacier
Mt. Blackburn

Atna Peaks

Nunatak

NABESNA GLACIER
Mt. Blackburn

Atna Peaks

Nunatak

NABESNA GLACIER


of Northbound Terranes

MacKevett, Jr., George Plafker, Donald H. Richter, 

R. Schmoll 

rofessional Paper 1616

al Park Service

on
of Northbound Terranes

MacKevett, Jr., George Plafker, Donald H. Richter, 

R. Schmoll 

rofessional Paper 1616

al Park Service

on
 Geologic Terranes............................................................................................................ 19

f the Continental Backstop............................................................................................... 26

 and Cretaceous Adhesive .............................................................................................. 28

............................................................................................................................................. 30

or the Archipelago ............................................................................................................ 42

ranes—Accretionary Processes on Edge..................................................................... 43

Arrive .................................................................................................................................... 54

y Reshaped by Earthquakes, Volcanoes, and Glaciers............................................. 69

.............................................................................................................................................. 69

.............................................................................................................................................. 71.............................................................................................................................................. 76

 and Gold? .......................................................................................................................... 86

ble Spots .............................................................................................................................. 95

.............................................................................................................................................. 95

 Fault System..................................................................................................................... 102

–Skolai Pass........................................................................................................................ 103

aint Elias Mountains......................................................................................................... 110

ver Basin.............................................................................................................................. 121

.............................................................................................................................................. 126

River..................................................................................................................................... 132

.............................................................................................................................................. 136

.............................................................................................................................................. 138

.............................................................................................................................................. 138

.............................................................................................................................................. 141

lacier–Russell Fiord.......................................................................................................... 144
 Geologic Terranes............................................................................................................ 19

f the Continental Backstop............................................................................................... 26

 and Cretaceous Adhesive .............................................................................................. 28

............................................................................................................................................. 30

or the Archipelago ............................................................................................................ 42

ranes—Accretionary Processes on Edge..................................................................... 43

Arrive .................................................................................................................................... 54

y Reshaped by Earthquakes, Volcanoes, and Glaciers............................................. 69

.............................................................................................................................................. 69

.............................................................................................................................................. 71.............................................................................................................................................. 76

 and Gold? .......................................................................................................................... 86

ble Spots .............................................................................................................................. 95

.............................................................................................................................................. 95

 Fault System..................................................................................................................... 102

–Skolai Pass........................................................................................................................ 103

aint Elias Mountains......................................................................................................... 110

ver Basin.............................................................................................................................. 121

.............................................................................................................................................. 126

River..................................................................................................................................... 132

.............................................................................................................................................. 136

.............................................................................................................................................. 138

.............................................................................................................................................. 138

.............................................................................................................................................. 141

lacier–Russell Fiord.......................................................................................................... 144
en Hills north of the Denali fault..................................................................................... 27

assic and Cretaceous Nutzotin Mountains sequence ............................................... 29

 viewed to north from the east bank of the Nizina River............................................. 32

ek.......................................................................................................................................... 34

 in the Tetelna Volcanics along Cross Creek ................................................................ 35

ed carbonate rocks of the McCarthy Formation .......................................................... 37

d the north side of the Chitistone River at Grotto Creek.............................................. 39

sing above the west side of the Nizina River................................................................ 41

t and the trough of Art Lewis Glacier............................................................................. 45

e eastern Chugach Mountains ....................................................................................... 46

h Complex ............................................................................................................................ 47

st, looking west, near the Little Bremner River ........................................................... 48

d to west, from north of Natural Arch............................................................................. 53

 Libbey Glacier .................................................................................................................. 56

g northwest, from above The Nunatak ......................................................................... 57

movar Hills ......................................................................................................................... 58

Libbey and Agassiz Glaciers, looking northwest.......................................................... 60

a Formation in the Chaix Hills ......................................................................................... 63

w to north, fl owing from the slopes of Mt. Eberly ........................................................ 65

art of the Yakataga Formation in the Karr Hills ............................................................ 66

ormity in the Yakataga Formation, Pinnacle Pass Hills............................................... 68
en Hills north of the Denali fault..................................................................................... 27

assic and Cretaceous Nutzotin Mountains sequence ............................................... 29

 viewed to north from the east bank of the Nizina River............................................. 32

ek.......................................................................................................................................... 34

 in the Tetelna Volcanics along Cross Creek ................................................................ 35

ed carbonate rocks of the McCarthy Formation .......................................................... 37

d the north side of the Chitistone River at Grotto Creek.............................................. 39

sing above the west side of the Nizina River................................................................ 41

t and the trough of Art Lewis Glacier............................................................................. 45

e eastern Chugach Mountains ....................................................................................... 46

h Complex ............................................................................................................................ 47

st, looking west, near the Little Bremner River ........................................................... 48

d to west, from north of Natural Arch............................................................................. 53

 Libbey Glacier .................................................................................................................. 56

g northwest, from above The Nunatak ......................................................................... 57

movar Hills ......................................................................................................................... 58

Libbey and Agassiz Glaciers, looking northwest.......................................................... 60

a Formation in the Chaix Hills ......................................................................................... 63

w to north, fl owing from the slopes of Mt. Eberly ........................................................ 65

art of the Yakataga Formation in the Karr Hills ............................................................ 66

ormity in the Yakataga Formation, Pinnacle Pass Hills............................................... 68
er from the Richardson Highway north of Copper Center........................................... 130

 from the northern slopes of the Chugach Mountains ................................................ 131

rthy and its surroundings, 1964, looking north ............................................................. 133

rom the west fl ank of Bonanza Ridge............................................................................. 134

ach Mountains .................................................................................................................. 137

om a camp near Juniper Island, Bagley Ice Field ........................................................ 139

terminus of the Yahtse Glacier, 1980, looking south .................................................... 140

pina Glacier area taken in 1979 ...................................................................................... 142

 the tidewater terminus of Hubbard Glacier................................................................. 145

ancas Point on the north side of Disenchantment Bay, looking northeast ............ 146

Saint Elias region showing localities of photographs included in this report......... 148

By To obtain metric units

2.54 centimeter

0.3048 meter

1.609 kilometer

 (mi2) 2.590 square kilometer

ft3) 0.028 cubic meter

mi3) 4.17 cubic kilometer

METRIC CONVERSION FACTORS
er from the Richardson Highway north of Copper Center........................................... 130

 from the northern slopes of the Chugach Mountains ................................................ 131

rthy and its surroundings, 1964, looking north ............................................................. 133

rom the west fl ank of Bonanza Ridge............................................................................. 134

ach Mountains .................................................................................................................. 137

om a camp near Juniper Island, Bagley Ice Field ........................................................ 139

terminus of the Yahtse Glacier, 1980, looking south .................................................... 140

pina Glacier area taken in 1979 ...................................................................................... 142

 the tidewater terminus of Hubbard Glacier................................................................. 145

ancas Point on the north side of Disenchantment Bay, looking northeast ............ 146

Saint Elias region showing localities of photographs included in this report......... 148

By To obtain metric units

2.54 centimeter

0.3048 meter

1.609 kilometer

 (mi2) 2.590 square kilometer

ft3) 0.028 cubic meter

mi3) 4.17 cubic kilometer

METRIC CONVERSION FACTORS
67.

gins on page 150.

MacKevett, Jr.,2 George Plafker,3 Donald H. Richter,4

 R. Schmoll1

 and Preserve (fig. 6), the largest unit 

 encompasses nearly 13.2 million acres 

e, its geologic makeup is shared with 

uge in Alaska, Kluane National Park 

ory, the Alsek-Tatshenshini Provincial 

istrict of Chugach National Forest and 

Forest, and Glacier Bay National Park 

s panhandle—shared landscapes of 

ic features. In 1978, the United Nations 

angell–Saint Elias and Kluane by desig

Glacier Bay and Alsek-Tatshenshini were 

ome 24 million acres of international 

parklands. The array of geologic features makes these parklands an impressive outdoor laboratory. Within Wrangell–Saint Elias are displayed features that indicate (1) how the southern Alaskan continental margin has more than doubled in size in approximately the past 200 million years by incremental addition of far-traveled geologic fragments; (2) how underthrusting by the Pacific oceanic plate6 has prompted rapid uplift, voluminous volcanism, and powerful 

earthquakes; and (3) how uplift of the coastal mountains adjacent to the stormbrewery of the Gulf of Alaska has engendered large and scenic systems of alpine, piedmont, and tidewater glaciers.

In 1892, glaciologist Israel C. Russell, writing of one of the earliest scientific probes of the Wrangell–Saint Elias region—his explorations of Malaspina 

Glacier and Mt. St. Elias—characterized the vast mountains and glaciers whose realms he invaded with a sense of astonishment. His descriptions are filled with superlatives. In the ensuing 100+ years, earth scientists have learned much more about the geologic evolution of the parklands, but the possibility of astonishment still is with us as we unravel the results of continuing tectonic processes along 

the south-central Alaska continental margin. Russell’s superlatives are justified: 

Wrangell–Saint Elias is, indeed, an awesome collage of geologic terranes. Most wonderful has been the continuing discovery that the disparate terranes are, like us, invaders of a sort with unique trajectories and timelines marking their northward journeys to arrive in today’s parklands.

This geologic guide includes six parts: the first part briefly notes the 

150-year history of exploration in the Wrangell–Saint Elias region that preceded the 20th century and summarizes the ensuing 100-year history of earth-science investigations that have brought us to our present understanding of the geologic makeup of the parklands.

Introduction 1
67.

gins on page 150.

MacKevett, Jr.,2 George Plafker,3 Donald H. Richter,4

 R. Schmoll1

 and Preserve (fig. 6), the largest unit 

 encompasses nearly 13.2 million acres 

e, its geologic makeup is shared with 

uge in Alaska, Kluane National Park 

ory, the Alsek-Tatshenshini Provincial 

istrict of Chugach National Forest and 

Forest, and Glacier Bay National Park 

s panhandle—shared landscapes of 

ic features. In 1978, the United Nations 

angell–Saint Elias and Kluane by desig

Glacier Bay and Alsek-Tatshenshini were 

ome 24 million acres of international 

parklands. The array of geologic features makes these parklands an impressive outdoor laboratory. Within Wrangell–Saint Elias are displayed features that indicate (1) how the southern Alaskan continental margin has more than doubled in size in approximately the past 200 million years by incremental addition of far-traveled geologic fragments; (2) how underthrusting by the Pacific oceanic plate6 has prompted rapid uplift, voluminous volcanism, and powerful 

earthquakes; and (3) how uplift of the coastal mountains adjacent to the stormbrewery of the Gulf of Alaska has engendered large and scenic systems of alpine, piedmont, and tidewater glaciers.

In 1892, glaciologist Israel C. Russell, writing of one of the earliest scientific probes of the Wrangell–Saint Elias region—his explorations of Malaspina 

Glacier and Mt. St. Elias—characterized the vast mountains and glaciers whose realms he invaded with a sense of astonishment. His descriptions are filled with superlatives. In the ensuing 100+ years, earth scientists have learned much more about the geologic evolution of the parklands, but the possibility of astonishment still is with us as we unravel the results of continuing tectonic processes along 

the south-central Alaska continental margin. Russell’s superlatives are justified: 

Wrangell–Saint Elias is, indeed, an awesome collage of geologic terranes. Most wonderful has been the continuing discovery that the disparate terranes are, like us, invaders of a sort with unique trajectories and timelines marking their northward journeys to arrive in today’s parklands.

This geologic guide includes six parts: the first part briefly notes the 

150-year history of exploration in the Wrangell–Saint Elias region that preceded the 20th century and summarizes the ensuing 100-year history of earth-science investigations that have brought us to our present understanding of the geologic makeup of the parklands.

Introduction 1
1

NATIONAL PARK

NATIONAL

PRESERVE

NATIONAL

PRESERVE

Caution. Private

property interspersed

with public lands.

RNICKE GLACIER

RIVER GLACIER

BERING GLACIER

BAGLEY ICEFIELD

GUYOT GLACIER

TANA GLACIER

JEFFERIES GLACIER

YAHTSE GLACIER

KENNICOTT

NABESNA

GLACIER

ROOT GLACIER

HAWKINS GLACIER

BARNARD GLACIER

RU

KLUTLAN GLACIER

SSELL GLACIER

CHITINA GLACIER

WALSH GLACIER

DONJEK GLACIER

STEELE GLACIER

LOGAN

GLACIER

COLUMBUS GLACIER SEWARD GLACIER

MALASPINA GLACIER

SEWARD GLACIER

NEWTON GLACIER

AGASSIZ GLACIER LIBBEY GLACIER

OG LI VIE GLACIER

HUBBARD GLACIER

LOWELL GLACIER

KASKAWULSH

HUBBARD GLACIER

GLACIER

ALVERSTONE GLAC EI R

VALERIE GLACIER

TURNER GLACIER

WEST

NUNATAK GLACIER

Long

Lake Kennicott

River

Hidden

Creek 

Lake 

Malaspina

Lake

Oily

Lake

Ross Green 

Lake

Solo

Lake

Rock

Lake

Ptarmigan

Lake

Chitistone

Falls

Clear

Creek

Hanagita

Lakina

Gilahina

Kuskulana

Nizina

Chakina

McCarthy

Cr

River

River

River

River

River

Tana River

River

Creek

Young Chitina

Chitina

River

Klu

River

River

River

River

Gra

Creek

nite

White

Skola

Toby Creek

Chitistone River

Creek

River

Kluane

River

Donjek

Duke River

KLUANE LAKE

River

ICY BAY

YAKUTAT BAY

RUSSELL FJORD

NUNATAK FJORD

DISENCHAN TMENT BAY

Yahtse River

Slims River

GULF OF ALASKA

KLUANE

NATIONAL PARK

KLUANE

GAME

SANCTUARY

Destruction Bay

Kennicott

McCarthy

Strelna

Chokosna

Dan Creek

May Creek

Burwash Landing

Alaska Highway

Cape Suckling

Cape

Yakataga

Point Manby

Haenke

Island

SourdoughPeak6201ft1890m

Donoho

Peak

6696ft

2041m

Mt Blackburn

16390ft

4996m

Regal Mountain

13845ft4220m

13860ft

4225m

13600ft4145m

Atna Peaks

elson Mountain

5457ft

1663m

Hanagita Peak

8504ft2592m

Mt Tom White

11210ft

3417m

Mt Hawkins

10395ft

3168m

Mt Steller

10617ft3236m Mt Miller 8875ft

2705m

Haydon Peak

11945ft

3641m

Mt St. Elias

18008ft5489m

Mt Augusta

14070ft4289m

Pt Glorious

5000ft1524m

Mt Cook

13760ft4194m

Mt Vancouver

15700ft

4785m

Mt Alverstone

14565ft

4439m

Mt Kennedy13093ft3991m

Mt Hubbard

15015ft

4577m

Mt Seattle10070ft3069m

Mt Jette

8460ft

2579m

King Peak

16971ft5173m

McArthur Peak

14400ft4389m

Mt Logan

19850ft6050m

Baldy Mountain

7230ft2204m

Mt Walsh

14780ft

4505m

Mt Macauly

15405ft4695m

Mt Lucania

17147ft5226m

Mt Steele

16644ft5073m

Mt Slaggard

15575ft

4747m 

Mt Wood

15885ft

4842m

Mt Bear

14831ft

4521m

Mt Churchill

15638ft4767m

University Peak

14470ft

4411m

Mt Bona

16421ft

5005m

Mt Natazhat

13435ft

4095m

Mt Sulzer

10926ft3330m

Solo Mountain

5875ft1791m

Dixie Pass Skolai Pass

Castle

Mountain

Chitistone Peak

SITKAGI BLUFFS

CHAIX

HILLS

KARR HILLS

GUYOT HILLS

SAMOVAR HILLS

SUCKLING

HILLS

Juniper

Island

BRITISH COLUMBIA

YUKON TERRITORY

UNITED STATES CANADA

UNITE

D STAT

ES

CANADA

ALASKA

YUKON TERRITORY

CANADA

UNITED STATES

G R A N I T E R A N G E

MACCOLL RIDGE

UNIVERSITY RANGE

R O B I N S O N M O U N T A I N S

WAXELL RIDGE

N

T

A I N

S

N

G

E

L

L

M

O

U

N

T

A I N

S

S

A I N

T

E

L

I

A

S

M

O

U

N

T A

I

N

S

I C

E

F I E

L

D

R

A

N

G

E

S

McCarthy Road

0

0 10 20 MILES

10 20 KILOMETERS

Wrangell–St. Elias National Park

Native corporation lands

Wrangell–St. Elias National Preserve Unpaved road
1

NATIONAL PARK

NATIONAL

PRESERVE

NATIONAL

PRESERVE

Caution. Private

property interspersed

with public lands.

NICKE GLACIER

IVER GLACIER

BERING GLACIER

BAGLEY ICEFIELD

GUYOT GLACIER

TANA GLACIER

JEFFERIES GLACIER

YAHTSE GLACIER

KENNICOTT

NABESNA

GLACIER

ROOT GLACIER

HAWKINS GLACIER

BARNARD GLACIER

RU

KLUTLAN GLACIER

SSELL GLACIER

CHITINA GLACIER

WALSH GLACIER

DONJEK GLACIER

STEELE GLACIER

LOGAN

GLACIER

COLUMBUS GLACIER SEWARD GLACIER

MALASPINA GLACIER

SEWARD GLACIER

NEWTON GLACIER

AGASSIZ GLACIER LIBBEY GLACIER

OG LI VIE GLACIER

HUBBARD GLACIER

LOWELL GLACIER

KASKAWULSH

HUBBARD GLACIER

GLACIER

ALVERSTONE GLAC EI R

VALERIE GLACIER

TURNER GLACIER

WEST

NUNATAK GLACIER

Long

Lake Kennicott

River

Hidden

Creek 

Lake 

Malaspina

Lake

Oily

Lake

Ross Green 

Lake

Solo

Lake

Rock

Lake

Ptarmigan

Lake

Chitistone

Falls

Clear

Creek

Hanagita

Lakina

Gilahina

Kuskulana

Nizina

Chakina

McCarthy

Cr

River

River

River

River

River

Tana River

River

Creek

Young Chitina

hitina

River

Klu

River

River

River

iver

Gra

Creek

nite

White

Skola

Toby Creek

Chitistone River

Creek

River

Kluane

River

Donjek

Duke River

KLUANE LAKE

River

ICY BAY

YAKUTAT BAY

RUSSELL FJORD

NUNATAK FJORD

DISENCHAN TMENT BAY

Yahtse River

Slims River

GULF OF ALASKA

KLUANE

NATIONAL PARK

KLUANE

GAME

SANCTUARY

Destruction Bay

Kennicott

McCarthy

Strelna

Chokosna

Dan Creek

May Creek

Burwash Landing

Alaska Highway

Cape Suckling

Cape

Yakataga

Point Manby

Haenke

Island

SourdoughPeak6201ft1890m

Donoho

Peak

6696ft

2041m

Mt Blackburn

16390ft

4996m

Regal Mountain

13845ft4220m

13860ft

4225m

13600ft4145m

Atna Peaks

son Mountain

5457ft

1663m

Hanagita Peak

8504ft2592m

Mt Tom White

11210ft

3417m

Mt Hawkins

10395ft

3168m

Mt Steller

10617ft3236m Mt Miller 8875ft

2705m

Haydon Peak

11945ft

3641m

Mt St. Elias

18008ft5489m

Mt Augusta

14070ft4289m

Pt Glorious

5000ft1524m

Mt Cook

13760ft4194m

Mt Vancouver

15700ft

4785m

Mt Alverstone

14565ft

4439m

Mt Kennedy13093ft3991m

Mt Hubbard

15015ft

4577m

Mt Seattle10070ft3069m

Mt Jette

8460ft

2579m

King Peak

16971ft5173m

McArthur Peak

14400ft4389m

Mt Logan

19850ft6050m

Baldy Mountain

7230ft2204m

Mt Walsh

14780ft

4505m

Mt Macauly

15405ft4695m

Mt Lucania

17147ft5226m

Mt Steele

16644ft5073m

Mt Slaggard

15575ft

4747m 

Mt Wood

15885ft

4842m

Mt Bear

14831ft

4521m

Mt Churchill

15638ft4767m

University Peak

14470ft

4411m

Mt Bona

16421ft

5005m

Mt Natazhat

13435ft

4095m

Mt Sulzer

10926ft3330m

Solo Mountain

5875ft1791m

7655ft2333m

Dixie Pass Skolai Pass

Castle

Mountain

Chitistone Peak

SITKAGI BLUFFS

CHAIX

HILLS

KARR HILLS

GUYOT HILLS

SAMOVAR HILLS

SUCKLING

HILLS

Juniper

Island

BRITISH COLUMBIA

YUKON TERRITORY

UNITED STATES CANADA

UNITE

D STAT

ES

CANADA

ALASKA

YUKON TERRITORY

CANADA

UNITED STATES

G R A N I T E R A N G E

MACCOLL RIDGE

UNIVERSITY RANGE

R O B I N S O N M O U N T A I N S

WAXELL RIDGE

N

T

A I N

S

R

A

N

G

E

L

L

M

O

U

N

T

A I N

S

S

A I N

T

E

L

I

A

S

M

O

U

N

T A

I

N

S

I C

E

F I E

L

D

R

A

N

G

E

S

McCarthy Road

0

0 10 20 MILES

10 20 KILOMETERS

Wrangell–St. Elias National Park

Native corporation lands

Wrangell–St. Elias National Preserve Unpaved road
 for trading opportunities. In 1884, 

cting, examining several of the lower 

intering in Taral. Also in 1884, Lt. W.R. 

usive sortie to test the navigability of the 

ta. Although Abercrombie’s party was 

River, they reported an alternative route 

Basin. In 1885, a second military explor

 H.T. Allen successfully ascended the 

ntact the native leader Nicolai, ascended 

uth of Dan Creek. Like Russian traders 

lements in use by Nicolai’s band and 

ment on Dan Creek (today’s “Nizina 

t of the copper ore found by the Natives 

eans copper.) Returning to Taral, the 

per River to Batzulnetas, naming Mounts 

zing aboriginal trails that—although 

cess to the parklands today. At times, 

ectors Peder Johnson and John Bremner, 

n. After leaving the Copper River 

e Tetlin, Tanana, and Yukon Rivers to the 

alleled epic of Alaskan exploration.

.S. Army, led an expedition sponsored 

y Bay region and climb Mt. St. 

cient and no systematic surveys were 

 were published and place names were 

Crossing Skolai Pass, the expedition then descended the Nizina, Chitina, and Copper Rivers to the coast near Cordova. This expedition, like those of Abercrombie and Allen, primarily evaluated routes to Alaska’s interior. Nonetheless, it also expressly supported geologic studies of a general character and filled a geographic blank, connecting explorations of the Yukon River in 1883 with the headwaters of the Tanana and Copper Rivers and with Allen’s 1885 chart of the Chitina and Copper River drainages.

By the late 1890’s, the lure of gold discoveries in the Klondike region 

of Canada’s Yukon had irresistibly drawn thousands of argonauts inland from Alaska’s coasts, despite a paucity of reliable geographic information. Most stampeders followed a principally Canadian route over Chilkoot Pass near Skagway to the headwaters of the Yukon River, which they descended to the Klondike. However, unscrupulous promoters circulated stories of an easy, “all-American” passage from Prince William Sound to the interior, luring many would-be miners to Port Valdez. Stampeders tried many paths through the coastal mountains in the Wrangell–Saint Elias region, undergoing severe hardships and suffering. In attempts to investigate and publicize the most reliable routes, military exploring expeditions under W.R. Abercrombie were launched in 1898 and 1899. In 1898, F.C. Schrader, USGS, accompanied the expedition, which explored a large circuit from Valdez to the Copper River Basin and back via Valdez Glacier and the Klutina, Copper, Tasnuna, and Lowe River valleys. Concurrently, a separate expedition, led by USGS geologists W.J. Peters and A.H. Brooks, investigated overland routes from the White River to the Tanana River. In 1899, Oscar Rohn, USGS, accompanied a second military expedition, which explored both the southern and northern flanks of the Wrangell Mountains. Rohn was the first to report copper-bearing float on the Kennicott Glacier, although he did not track it to nearby bedrock sources. Rohn’s work, in particular, laid the groundwork for many subsequent geologic investigations in what later became Wrangell–Saint Elias National Park and Preserve. Like earlier expeditions, these government parties benefitted from the company of prospectors and natives, who already had acquired working knowledge of routes and conditions to be encountered, as well as locations of gold-bearing placers and gold- and copper-bearing lodes.

Introduction 5
 for trading opportunities. In 1884, 

cting, examining several of the lower 

intering in Taral. Also in 1884, Lt. W.R. 

usive sortie to test the navigability of the 

ta. Although Abercrombie’s party was 

River, they reported an alternative route 

Basin. In 1885, a second military explor

 H.T. Allen successfully ascended the 

ntact the native leader Nicolai, ascended 

uth of Dan Creek. Like Russian traders 

lements in use by Nicolai’s band and 

ment on Dan Creek (today’s “Nizina 

t of the copper ore found by the Natives 

eans copper.) Returning to Taral, the 

per River to Batzulnetas, naming Mounts 

zing aboriginal trails that—although 

cess to the parklands today. At times, 

ectors Peder Johnson and John Bremner, 

n. After leaving the Copper River 

e Tetlin, Tanana, and Yukon Rivers to the 

alleled epic of Alaskan exploration.

.S. Army, led an expedition sponsored 

y Bay region and climb Mt. St. 

cient and no systematic surveys were 

 were published and place names were 

Crossing Skolai Pass, the expedition then descended the Nizina, Chitina, and Copper Rivers to the coast near Cordova. This expedition, like those of Abercrombie and Allen, primarily evaluated routes to Alaska’s interior. Nonetheless, it also expressly supported geologic studies of a general character and filled a geographic blank, connecting explorations of the Yukon River in 1883 with the headwaters of the Tanana and Copper Rivers and with Allen’s 1885 chart of the Chitina and Copper River drainages.

By the late 1890’s, the lure of gold discoveries in the Klondike region 

of Canada’s Yukon had irresistibly drawn thousands of argonauts inland from Alaska’s coasts, despite a paucity of reliable geographic information. Most stampeders followed a principally Canadian route over Chilkoot Pass near Skagway to the headwaters of the Yukon River, which they descended to the Klondike. However, unscrupulous promoters circulated stories of an easy, “all-American” passage from Prince William Sound to the interior, luring many would-be miners to Port Valdez. Stampeders tried many paths through the coastal mountains in the Wrangell–Saint Elias region, undergoing severe hardships and suffering. In attempts to investigate and publicize the most reliable routes, military exploring expeditions under W.R. Abercrombie were launched in 1898 and 1899. In 1898, F.C. Schrader, USGS, accompanied the expedition, which explored a large circuit from Valdez to the Copper River Basin and back via Valdez Glacier and the Klutina, Copper, Tasnuna, and Lowe River valleys. Concurrently, a separate expedition, led by USGS geologists W.J. Peters and A.H. Brooks, investigated overland routes from the White River to the Tanana River. In 1899, Oscar Rohn, USGS, accompanied a second military expedition, which explored both the southern and northern flanks of the Wrangell Mountains. Rohn was the first to report copper-bearing float on the Kennicott Glacier, although he did not track it to nearby bedrock sources. Rohn’s work, in particular, laid the groundwork for many subsequent geologic investigations in what later became Wrangell–Saint Elias National Park and Preserve. Like earlier expeditions, these government parties benefitted from the company of prospectors and natives, who already had acquired working knowledge of routes and conditions to be encountered, as well as locations of gold-bearing placers and gold- and copper-bearing lodes.

Introduction 5
ell Glacier 

s Russell Glacier toward Castle Mountain and Skolai Pass in the summer of 1914. Having originated in 

cier’s terminus, source of the White River, in support of geologic explorations by a USGS party. The 

 upstream from Dawson. According to Oscar Rohn (USGS), the route from Valdez to Dawson via Skolai 

ew stampeders in the Klondike gold rush of 1898–99. (S.R. Capps)

Introduction 7

of the Kotsina, Kluvesna, and Kuskulana 

e Nikolai mine (named for the Taral 

ospectors, Clarence Warner and Jack 

 Nikolai mine were searching for the 

ott Glacier that Rohn had reported 

Within weeks, A.C. Spencer, USGS, 

ined talus marking the Bonanza lode, 

m markers on what he thought was 

ted several other significant copper lodes 

 Mountains and by 1902 had located 

nd Nizina districts. Prospectors also 

 the northern flank, discovering numer

d. Results in the Nabesna area, however, 

south.

Lake. In the Wrangell

Saint Elias region, these demonstrated resources of 

petroleum and coal were to influence the commercial developments and the 

politics of the early 20th century. They ultimately sparked renewed pulses of exploration between 1954 and 1986, and influenced the location of the southern boundary of Wrangell–Saint Elias National Park and Preserve that was legislated in late 1980.
ell Glacier 

s Russell Glacier toward Castle Mountain and Skolai Pass in the summer of 1914. Having originated in 

cier’s terminus, source of the White River, in support of geologic explorations by a USGS party. The 

 upstream from Dawson. According to Oscar Rohn (USGS), the route from Valdez to Dawson via Skolai 

ew stampeders in the Klondike gold rush of 1898–99. (S.R. Capps)

Introduction 7

of the Kotsina, Kluvesna, and Kuskulana 

e Nikolai mine (named for the Taral 

ospectors, Clarence Warner and Jack 

 Nikolai mine were searching for the 

ott Glacier that Rohn had reported 

Within weeks, A.C. Spencer, USGS, 

ined talus marking the Bonanza lode, 

m markers on what he thought was 

ted several other significant copper lodes 

 Mountains and by 1902 had located 

nd Nizina districts. Prospectors also 

 the northern flank, discovering numer

d. Results in the Nabesna area, however, 

south.

Lake. In the Wrangell

Saint Elias region, these demonstrated resources of 

petroleum and coal were to influence the commercial developments and the 

politics of the early 20th century. They ultimately sparked renewed pulses of exploration between 1954 and 1986, and influenced the location of the southern boundary of Wrangell–Saint Elias National Park and Preserve that was legislated in late 1980.
e southern Alaskan studies also provided 

retionary terranes. Neotectonic, seismo

at began in the region of the 1964 

Sound were expanded to evaluate all 

nd were accompanied by much new 

nt Elias region, major unrecognized fault 

t, were defined, and offset histories 

e Fairweather and Denali faults, were 

e Bay oil field in 1968 on Alaska’s 

on geologic investigations in southern 

ns-Alaska pipeline and an ice-free tide

e of geotechnical studies and surficial 

arly 800 mile long corridor for the 

from the Denali fault south through the 

inus and shipping facility near Valdez 

 of the distribution and physical and 

nsolidated deposits near the pipeline 

r than bury the pipeline in most perma

te between Willow Lake and Gakona 

Wrangell–Saint Elias National Preserve, 

nd.) Second, a mood of post-discovery 

ation of other possible oil provinces, 

the Federal government and company drilling of 13 test wells on the outer continental shelf in the northern Gulf of Alaska yielded information that helped to define the geologic characteristics of the offshore part of the Yakutat block, confirming the oceanward boundary of this latest addition to the collage of displaced terranes that makes up southern Alaska.

In 1989–90, eruptions of Mt. Redoubt, an active volcano in the northeastern 

part of the Aleutian arc, seriously impacted air transportation and ground facilities and services over a large region of northern Cook Inlet, and 1992 eruptions of Mt. Spurr, even closer to Anchorage, had similar regional impacts. In response, the Alaska Volcano Observatory, established in 1988 in Anchorage, began to institutionalize studies of volcanic processes and hazards and to develop 

eruption prediction capabilities—principally for active volcanoes in the Aleutian Islands, the Alaska Peninsula, and Cook Inlet. Topical studies of the Wrangell volcanic field had been underway for many years, having begun in the early 

1970’s during the last stages of regional geologic mapping in the Nabesna and McCarthy quadrangles. Volcanic studies continued during the 1980’s and early 1990’s, producing large-scale maps of most of the volcanic edifices in the western Wrangell Mountains, including the quietly active Mt. Wrangell. From the outset of these studies, it was clear that explosive volcanism is not typical for Wrangell volcanoes and that their remoteness from major population centers minimized their hazard. However, the discovery that the volcanic activity apparently is induced by underthrusting of the combined Pacific oceanic plate and piggybacking crust of the Yakutat terrane beneath the continental margin provided an important link between volcanic hazards investigations and concurrent earthquake hazards studies of major fault systems. Studies of both the faulting and the volcanism have yielded integrative clues about the geometry and chronology of terrane convergence and collision and plate configuration in 

the northern Gulf of Alaska. 

Introduction 9
e southern Alaskan studies also provided 

retionary terranes. Neotectonic, seismo

at began in the region of the 1964 

Sound were expanded to evaluate all 

nd were accompanied by much new 

nt Elias region, major unrecognized fault 

t, were defined, and offset histories 

e Fairweather and Denali faults, were 

e Bay oil field in 1968 on Alaska’s 

on geologic investigations in southern 

ns-Alaska pipeline and an ice-free tide

e of geotechnical studies and surficial 

arly 800 mile long corridor for the 

from the Denali fault south through the 

inus and shipping facility near Valdez 

 of the distribution and physical and 

nsolidated deposits near the pipeline 

r than bury the pipeline in most perma

te between Willow Lake and Gakona 

Wrangell–Saint Elias National Preserve, 

nd.) Second, a mood of post-discovery 

ation of other possible oil provinces, 

the Federal government and company drilling of 13 test wells on the outer continental shelf in the northern Gulf of Alaska yielded information that helped to define the geologic characteristics of the offshore part of the Yakutat block, confirming the oceanward boundary of this latest addition to the collage of displaced terranes that makes up southern Alaska.

In 1989–90, eruptions of Mt. Redoubt, an active volcano in the northeastern 

part of the Aleutian arc, seriously impacted air transportation and ground facilities and services over a large region of northern Cook Inlet, and 1992 eruptions of Mt. Spurr, even closer to Anchorage, had similar regional impacts. In response, the Alaska Volcano Observatory, established in 1988 in Anchorage, began to institutionalize studies of volcanic processes and hazards and to develop 

eruption prediction capabilities—principally for active volcanoes in the Aleutian Islands, the Alaska Peninsula, and Cook Inlet. Topical studies of the Wrangell volcanic field had been underway for many years, having begun in the early 

1970’s during the last stages of regional geologic mapping in the Nabesna and McCarthy quadrangles. Volcanic studies continued during the 1980’s and early 1990’s, producing large-scale maps of most of the volcanic edifices in the western Wrangell Mountains, including the quietly active Mt. Wrangell. From the outset of these studies, it was clear that explosive volcanism is not typical for Wrangell volcanoes and that their remoteness from major population centers minimized their hazard. However, the discovery that the volcanic activity apparently is induced by underthrusting of the combined Pacific oceanic plate and piggybacking crust of the Yakutat terrane beneath the continental margin provided an important link between volcanic hazards investigations and concurrent earthquake hazards studies of major fault systems. Studies of both the faulting and the volcanism have yielded integrative clues about the geometry and chronology of terrane convergence and collision and plate configuration in 

the northern Gulf of Alaska. 

Introduction 9
Introduction 11
Introduction 11
Figure 9 (following pages). Major lithotectonic terranes and geologic units of southern Alaska and nearby areas. (Modifi ed from Plafker, Moore, and Winkler, 1994.)

s persisted with only minor changes 

ific plate 

 in the 

nt Elias 

-transform 

e guaran

quakes 

pi

nd 

s 

ry 

d 

en 

 

red 

1964, the 

gest earth

ed a segment 

east end 

arge-scale 

thern Alaska; 

r a zone at least 90 mi wide. 

a trans-Pacific tsunami that caused 

ng the Pacific coast as far away as 

 compressional folds and faults marks 

utat terrane has been thrust obliquely 

mational zone is at least 60 mi wide, and 

re in major seismic events such as the 

In the Alaska Peninsula and Cook Inlet, where the subduction zone steepens to about a 45° dip beneath the axis of the arc, episodic but widespread magmatismhas characterized most of the last 50 million years, driven by orthogonal convergence of the Pacific plate beneath the continental margin since Eocene time. The subduction zone dips northward at a lower angle under the Wrangell Mountains and the axis of the arc is farther inland. Arc volcanism began in the Wrangell Mountains about 26 m.y. ago, when the northwestward-moving Pacific plate, 

with its piggyback load of the Yakutat terrane, reached sufficient depth in the subduction zone to generate magma.

These subduction-generated magmas have distinctive compositions. Thus, 

by analogy, plutonic-volcanic complexes in pre-Eocene rocks also provide compositional clues to their possible origins in magmatic arcs. Similar distinctive compositions in the older rocks enable geologists to decipher the magmatic arc settings and plate-tectonic histories of the pre-Eocene terranes that make up the majority of the Wrangell–Saint Elias region.

The Present Tectonic Setting of Southern Alaska—Key to the Past 13
Figure 9 (following pages). Major lithotectonic terranes and geologic units of southern Alaska and nearby areas. (Modifi ed from Plafker, Moore, and Winkler, 1994.)

ersisted with only minor changes 

plate 

the 

Elias 

nsform 

aran

kes 

4, the 

t earth

a segment 

t end 

e-scale 

rn Alaska; 

zone at least 90 mi wide. 

ans-Pacific tsunami that caused 

he Pacific coast as far away as 

mpressional folds and faults marks 

terrane has been thrust obliquely 

onal zone is at least 60 mi wide, and 

n major seismic events such as the 

In the Alaska Peninsula and Cook Inlet, where the subduction zone steepens to about a 45° dip beneath the axis of the arc, episodic but widespread magmatismhas characterized most of the last 50 million years, driven by orthogonal convergence of the Pacific plate beneath the continental margin since Eocene time. The subduction zone dips northward at a lower angle under the Wrangell Mountains and the axis of the arc is farther inland. Arc volcanism began in the Wrangell Mountains about 26 m.y. ago, when the northwestward-moving Pacific plate, 

with its piggyback load of the Yakutat terrane, reached sufficient depth in the subduction zone to generate magma.

These subduction-generated magmas have distinctive compositions. Thus, 

by analogy, plutonic-volcanic complexes in pre-Eocene rocks also provide compositional clues to their possible origins in magmatic arcs. Similar distinctive compositions in the older rocks enable geologists to decipher the magmatic arc settings and plate-tectonic histories of the pre-Eocene terranes that make up the majority of the Wrangell–Saint Elias region.

The Present Tectonic Setting of Southern Alaska—Key to the Past 13
0 50 200 MILES 100

0 50 100 200 KILOMETERS

YUKON TERRITORY

BRITISH COLUMBIA

CANADA ALASKA, U.S.

Yakutat

Sitka

F

WR

WR

WR

AX

YA

YA

CG?

?

CG

FF

QCF

DFS

FF

WR

AX

WR

AX

WR

CG

BRFS

TFS

DFS

DRZ

PACIFIC PLATE

NORTH AMERICAN PLATE

140 ̊ 135 ̊




























ry not obviously faulted

aled or inferred

n upper plate

dicate relative motion

own

late relative to North 

 in./yr 

Major faults

AM Aleutian megathrust

BRFS Border Ranges fault system

CFS Contact fault system

CSES Chugach-St. Elias fault system

DRZ Dangerous River zone

DFS Denali fault system

FF Fairweather fault

KIZ Kayak Island zone

PZ Pamplona zone

QCF Queen Charlotte fault

RF Resurrection fault

TF Totschunda fault

TFS Transition fault system

TT Talkeetna thrust

WFF West Fork fault

SL102030

A

PACIFIC PLATE 

 TFS 

 Czu

Eocene

eanic crust H/V=1

Czv Upper Cenozoic Wrangell Lava

Czu Upper Cenozoic deep marine

sedimentary rocks

Tg Tertiary granitic rocks

Ty Neogene Yakataga Formation

To Eocene and Paleocene Orca Group

Tl Paleogene sedimentary rocks

Mz Cretaceous metaflysch and

metamelange

Jg Jurassic granitic rocks

MzPzu Mesozoic and Paleozoic schistose rocks

Mzpz Mesozoic and Paleozoic sedimentary

and volcanic rocks

Pzg Paleozoic plutonic rocks

Movement away from readerMovement toward reader

EXPLANATION

 Present Tectonic Setting of Southern Alaska—Key to the Past 15
CHUGACH–ST. ELIAS

FAULT SYSTEM

Weak subduction

Yakutat

terrane

TRANSITION

FAULT SYSTEM

Strong subduction

The Present Tectonic Setting of Southern Alaska—Key to the Past 17

Yakutat terrane and the North American plate, has jammed the subduction zone and quieted the volcanism. (Modifi ed from 

Richter, Rosenkrans, and Steigerwald, 1995.)
CHUGACH–ST. ELIAS

FAULT SYSTEM

Weak subduction

Yakutat

terrane

TRANSITION

FAULT SYSTEM

Strong subduction

The Present Tectonic Setting of Southern Alaska—Key to the Past 17

Yakutat terrane and the North American plate, has jammed the subduction zone and quieted the volcanism. (Modifi ed from 

Richter, Rosenkrans, and Steigerwald, 1995.)
Some have been rotated relative to 

aced vast distances compared to less 

t fragments generally differ in the 

te them—their lithologies, and they 

hose rocks have undergone—their 

are called lithotectonic terranes—or, 

disparate terranes has created a collage 

ses by which the collage was assem

grown by the addition of exotic terranes 

termed accretionary tectonics. Terrane 

ntal margin today: the latest terrane 

eing displaced, jamming against and 

rse: some represent pieces of old 

erican craton), whereas parts of others 

 represent island arcs formed in the 

). Others represent arcs formed on the 

ian arc or western South America). 

e detritus eroded from the edge of 

The Yakutat terrane provides a prime example, having been transposed 375 mi along the Queen Charlotte–Fairweather transform fault system in the last approximately 30 million years.

The designation of terranes in regional tectonic analysis received its greatest 

impetus in the mid-1970’s from landmark papers on the Wrangellia terrane. Paleomagnetic data from 230 million-year-old Triassic basalts—the distinctive Nikolai Greenstone of the Wrangell Mountains (fig. 13)—provided quantitative evidence for post-Triassic northward displacement of the basalts for thousands of miles from where they formed near the Triassic equator. Subsequent studies of other nearby terranes in the Wrangell–Saint Elias region substantiated that they, too, were displaced, having been moved variable distances from their places of origin by tectonic processes. In fact, it has been shown that so much of Alaska consists of displaced terranes that only a small triangle-shaped area immediately north of the Tintina fault near the International Boundary, less than 1 percent of Alaska’s total area, is an undisplaced part of the North American continental nucleus. It is against this ancient continental edge that all terranes to the south accreted, including all the rocks of Wrangell–Saint Elias National Park and Preserve. 

Wrangell–Saint Elias—A Collage of Geologic Terranes 19
placed vast distances compared to less 

nt fragments generally differ in the 

tute them—their lithologies, and they 

 those rocks have undergone—their 

s are called lithotectonic terranes—or, 

f disparate terranes has created a collage 

sses by which the collage was assem

 grown by the addition of exotic terranes 

e termed accretionary tectonics. Terrane 

ental margin today: the latest terrane 

being displaced, jamming against and 

erse: some represent pieces of old 

merican craton), whereas parts of others 

ts represent island arcs formed in the 

c). Others represent arcs formed on the 

utian arc or western South America). 

he detritus eroded from the edge of 

mi along the Queen Charlotte–Fairweather transform fault system in the last approximately 30 million years.

The designation of terranes in regional tectonic analysis received its greatest 

impetus in the mid-1970’s from landmark papers on the Wrangellia terrane. Paleomagnetic data from 230 million-year-old Triassic basalts—the distinctive Nikolai Greenstone of the Wrangell Mountains (fig. 13)—provided quantitative evidence for post-Triassic northward displacement of the basalts for thousands of miles from where they formed near the Triassic equator. Subsequent studies of other nearby terranes in the Wrangell–Saint Elias region substantiated that they, too, were displaced, having been moved variable distances from their places of origin by tectonic processes. In fact, it has been shown that so much of Alaska consists of displaced terranes that only a small triangle-shaped area immediately north of the Tintina fault near the International Boundary, less than 1 percent of Alaska’s total area, is an undisplaced part of the North American continental nucleus. It is against this ancient continental edge that all terranes to the south accreted, including all the rocks of Wrangell–Saint Elias National Park and Preserve. 

Wrangell–Saint Elias—A Collage of Geologic Terranes 19
D

D D

D D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

D

ALASKA

YUKON TERRITOR

A

DRF

DFS

CFS

FF

?

ChugachPrince WilliamYakutat

Thrust fault—Sawteeth on upper plateStrike-slip fault—Queried where relations uncertain; barbs 

indicate relative motion

Fault—Displacement unknownDenali fault systemTotschunda faultDuke River faultBorder Ranges fault systemContact fault systemChugach–St. Elias fault systemRagged Mountain faultKayak Island zoneFairweather fault

D

DFSTFDRFBRFCFSCSERMFKIZFF

nes and major faults of Wrangell–Saint Elias National Park and Preserve.

Wrangell–Saint Elias—A Collage of Geologic Terranes 21
TERRANES

Windy (Yukon-Tanana?)Gravina-NutzotinWrangelliaAlexanderChugachPrince WilliamYakutat

Thrust fault—Sawteeth on upper plateStrike-slip fault—Queried where relations uncertain; barbs 

indicate relative motion

Fault—Displacement unknownDenali fault systemTotschunda faultDuke River faultBorder Ranges fault systemContact fault systemChugach–St. Elias fault systemRagged Mountain faultKayak Island zoneFairweather fault



EXPLANATION

DFSTFDRFBRFCFSCSERMFKIZFF

Wrangell–Saint Elias—A Collage of Geologic Terranes 21
posits

osits

its

mentary and volcanic deposits

ous deposits

 ophiolites

ic rocks

d sedimentary rocks

entary rocks

ks

c plutonic rocks

TECTONIC OVERPRINTS

Tectonic melangePenetratively deformed and (or) regionally metamorphosed

Major unconformitySteep fault—Arrows indicate sense of slipThrust fault—Sawteeth on upper plateRadiometric ageAGE DIAGNOSTIC FOSSILS

Marine megafossilMarine microfossilPlant fossilAge unknown

TECTONIC EVENTS

Accretionary episodeRifting episode

CONTACTS

Stratigraphic or intrusiveTime-transgressiveFacies change

D D

EXPLANATION

*

??

c characteristics of lithotectonic terranes in the Wrangell–Saint Elias region. (Modifi ed from Nokleberg and 

r, 1994.)

Wrangell–Saint Elias—A Collage of Geologic Terranes 23
Shallow-marine terrigenous deposits

Shallow-marine carbonate depositsShallow-marine siliceous depositsDeep-marine hemipelagic sedimentary and Deep-marine pelagic and siliceous depositOceanic crust, seamounts, and ophiolitesMafic volcanic and volcaniclastic rocksTurbidite depositsSubduction-related volcanic and sedimentaRift-related volcanic and sedimentary rockSubduction-related granitic rocksRift-related mafic and ultramafic plutonic rHiatusNote: Patterns may be combined

Figure 14 (below and pages 24–25). Geologic characte

others, 1994, and Plafker, Moore, and Winkler, 1994.)

Figure 13 (facing page). Remains of the tramline that c

right to lower left in this view. Mt. Blackburn rises abovbasaltic rocks of the Triassic Nikolai Greenstone. The pa near-equatorial latitude at the time the basalts formednear lat 61°30’ N. The depositional contact with overlyin

the right-hand skyline, as well as on Donoho Peak in the deposits, such as form in the Persian Gulf region today. northward. (E.M. MacKevett, Jr.)
**

*

Yakutat Group:

melange facies

FAIRWEATHER

FAULT

McHugh ComplexMcHugh Complex

Schist of Liberty Creek

ChitinaArc(SaintElias)SkolaiArc(IcefieldRanges)

?

Wrangell–Saint Elias—A Collage of Geologic Terranes 25
**

*

Yakataga Formation

Poul Creek Formation

Kulthieth Formation

Yakutat Group:

flysch facies

Yakutat Group:

melange facies

Anatecticplutons

FAIRWEATHER

FAULT

Plutonic rocks Stratified rocks Plutonic rocks

Yakutat Terrane

Names of geologic units or rock type

AnatecticplutonsAnatectic?plutons



Wrangell–Saint Elias—A Collage of Geologic Terranes 25
Terrane 

ali fault; view is to the south. The rounded hills in the foreground are 

tzotin Mountains in the background are underlain chiefl y by sedimentary 

r swans are using the lake as a stopover on their migratory fl ight south. 

imilarity of lithologies and structural features, some geologists 

 these fault-bounded sequences with the Windy terrane of the 

area about 140 mi to the northwest. In the Mt. McKinley area, 

ne consists of an assemblage of continental margin deposits, 

ke limestone bodies, that formed along the edge of the North 

n during the early Paleozoic. Other geologists have correlated 

h the Yukon-Tanana terrane, which extends 170 mi northward 

nds between the Tanana and Yukon Rivers. The Yukon-Tanana 

nsists of deposits formed along the continental margin in early 

 but contains much less limestone. In the Yukon-Tanana Upland, 

st of multiply deformed schists and gneisses formed by meta

verse sedimentary, volcanic, and plutonic rocks. Collectively, 

ed sequences of the Windy terrane that crop out in the Wrangell–

klands have protoliths and ages similar to those of the less dis

s of the Yukon-Tanana terrane. Thus, these rocks may represent 

derived from the edge of the Yukon-Tanana terrane, or from 

gin sequences fringing it, and were interleaved between strands 

ult system during Cenozoic dextral offset.

-Tanana terrane was accreted to the margin of North America 

c time, accompanied by intense deformation across the suture 

nism and metamorphism of regional extent. This crustal heating 

ved to weld the terrane to the continental margin. During the 

esozoic and Cenozoic time, the Yukon-Tanana rocks served as a 

o later arriving terranes as they continued to collide with and be 

Alaskan continental margin south of the Denali fault. Although 

en and crumpled episodically during subsequent accretionary 

re lodged firmly enough to bring the giant, northward-moving 

mposite terrane to a halt.
Wrangell–Saint Elias—A Collage of Geologic Terranes 27
zotin Belt

ved from the Yukon-Tanana terrane to the north (fig. 16). South 

a mine, the upper part of the Nutzotin Mountains sequence also 

shore and nonmarine strata. In the Chathenda Creek area, tuffaceous 

he top of the sequence is overlain conformably by fragmental 

canic rocks, which define the transition to the Chisana Formation. 

Formation contains marine and subaerial andesitic and basaltic 

volcaniclastic rocks as much as 9,500 ft thick, which contain minor 

marine sedimentary rocks in the lower part. Both the textures and 

he volcanic rocks are characteristic of an island arc assemblage. 

marine sedimentary rocks contain numerous pelecypods and ammo

ndicate the Early Cretaceous age of the Chisana Formation.

vina-Nutzotin belt in the Wrangell–Saint Elias region is intruded by 

us granitic plutons, such as the Klein Creek and Chisana plutons, 

sumed to represent the roots of the island arc for which the 

mation is the volcanic carapace. As in most magmatic arcs, the mid

adiometric ages of the deep-seated intrusive rocks are somewhat 

 the Early Cretaceous paleontologic and radiometric ages of the 

allow volcanic rocks. Millions of years are required for the 

ks to cool sufficiently for their constituent minerals to crystallize, 

ng in” isotopic ratios of radioactive elements that are used to 

ir absolute ages. In contrast, the volcanic rocks are quenched 

ly upon extrusion at the Earth’s surface.

tly, the flysch of the Nutzotin Mountains sequence was deposited 

th edge of the Wrangellia composite terrane as it approached the 

argin, close enough that the basin also received some detritus from 

nana terrane. The Chisana arc is interpreted to have formed on the 

h) edge of Wrangellia as subduction of oceanic crust was occurring 

ellia’s southern margin. At Wellesley Mountain, conglomeratic 

y be coeval with the latest stages of the Chisana arc lie unconform

ukon-Tanana terrane. Thus, at least locally, basin-margin facies 

st part of the Gravina-Nutzotin belt may have overlapped terranes 

and south. However, subsequent structural telescoping of the 

ularly its northern margins where all contacts are faults—makes 

ation tentative.
nglomerate in the Jurassic and Cretaceous Nutzotin Mountains sequence. 

lasts are quartz indicating that the sequence was receiving sediment from a 

ne terrane to the north (containing abundant quartz veins), which likely was 

na terrane; distinctive limestone clasts in the conglomerate can have been 

m the Wrangellia terrane to the south, which was advancing northward 

na-Nutzotin basin, eventually closing it completely. (D.H. Richter)

Wrangell–Saint Elias—A Collage of Geologic Terranes 29
rangellia

ged mountain ridges surrounding Kennicott and Root Glaciers and 

f the Chitistone and Nizina Rivers expose in nearly continuous 

most characteristic rocks of Wrangellia (fig. 17). The distinctive 

hering slopes of the Nikolai Greenstone contrast conspicuously 

-gray-weathering cliffs and ledges of the overlying Chitistone and 

tones. The color contrast can be seen easily from a distance, and 

00’s, the contact zone had gained the attention of prospectors and 

ho discovered that copper lodes were concentrated in its proximity. 

fabulous Bonanza lode east of Kennicott Glacier had been located. 

bably every linear foot of the contact zone in the southern Wrangell 

d been scrutinized, where it was accessible, and all major known 

its of the region had been staked.

olai Greenstone (fig. 14) consists of Triassic basalt flows whose 

ckness is nearly 10,000 ft. The greenstone formed a vast volcanic 

remnants cover large tracts on both north and south flanks of the 

untains and the south flank of the eastern Alaska Range, as well as 

s of Canada at least as far as the Kluane Lake region. Correlative 

own as far west as the Alaska Peninsula and at least as far east 

t Peninsula near Haines, Alaska. Large areas of Triassic basalt on 

harlotte and Vancouver Islands in British Columbia, known as the 

ormation, probably are offset continuations of the same volcanic 

h displaced by post-Triassic movement along the Denali, Queen 

other major transcurrent fault systems. The Nikolai Greenstone 

 during a 7–8 million year interval onto a mostly subaerial volcanic 

the perimeters of its outcrops, however, submarine flows have been 

olumetric estimates for the Nikolai Greenstone exceed a staggering 

nough to bury the entire State of Oregon with a quarter mile of 

Nikolai Greenstone is overlain by as much as 3,600 ft of Upper 

stone and dolomite in the area between the Kennicott Glacier and 

e River canyon, but the carbonate rocks thin rapidly westward, 

 northward. The lower part of the Chitistone Limestone in the 

ea contains stromatolites, relicts of evaporites, and algal-mat chips, 
widely scattered localities, remnants of fossiliferous marine silt

and limestone of Middle Triassic age, as much as 300 ft thick, inter

 the Nikolai Greenstone and underlying rocks. These strata contain 

e age-diagnostic pelecypod, Daonella, and provide biostratigraphic 

onset of basaltic volcanism represented by the overlying Nikolai 

stinctive Triassic and Jurassic rocks were deposited unconformably 

nants of an upper Paleozoic assemblage (fig. 14), consisting of 

anic flows and volcaniclastic rocks; shallow-marine shale, sand

mestone; and alkalic plutonic rocks. The stratified rocks may 

remnants of an intraoceanic island arc; their base is not exposed. 

ern slopes of the Wrangell Mountains, the stratified rocks are 

amed the Skolai Group, after the locality where they are exposed 

ely along Skolai Creek (fig. 18), and the conceptual arc also has 

e name, “Skolai” (fig. 11). At the Golden Horn, the limestone 

e lenses near the top of the Skolai Group that are as much as 800 ft 

tain abundant corals, crinoids, bryozoans, and brachiopods of Early 

The limestone is underlain by a Permian sedimentary sequence as 

0 ft thick, which is underlain in turn by Permian and Pennsylvanian 

 and volcanic rocks as much as 6,500 ft thick. Nearly complete 

the Skolai Group also occur in the areas of Chitistone Gorge, 

cier, and the head of the White River.

utons of mid-Pennsylvanian age (

≈300 million years old) invade 

ta of the Skolai Group in the Hawkins, Barnard, and Chitina 

(fig. 3) and consist principally of granite, monzonite, and syenite, 

at have relatively elevated levels of potassium compared to average 

s. These plutons probably are correlative with the more extensive 

es plutonic suite 20 mi to the east in Kluane National Park, Yukon 

ore than 50 mi to the west in the Gilahina River area, alkalic gabbro

iss of probable Pennsylvanian age intrude the Skolai Group; these 

be more mafic phases of the same intrusive suite. Metamorphosed 

se ages also are known in the Dadina River area on the west slopes 

ell, where they intrude foliated metasedimentary and metavolcanic 

 presumed to correlate with other less metamorphosed rocks 

 Skolai arc.

Wrangell–Saint Elias—A Collage of Geologic Terranes 31
Nizina Limestone

Chitistone Limestone

Nikolai Greenstone
iver

na River. The “Triassic Trinity” 

e dark-gray-weathering Nizina 

e of the Chitistone River are 

ion-collapse features are 

es are associated with major 

Wrangell–Saint Elias—A Collage of Geologic Terranes 33

Paleozoic Skolai arc sequence, the Triassic Nikolai Greenstone, 

ying Triassic-Jurassic shallow marine sedimentary rocks are the 

fy Wrangellia. Although they are widely and strikingly displayed 

re southern flank of the Wrangell Mountains, they also are wide

er parts of the parklands, underlying at least 50 percent of the 

nt Elias region (fig. 12) and forming one of the larger terranes 

laska. Upper Paleozoic and Mesozoic units that are broadly 

th the units of Wrangellia extend westward through the Talkeetna 

d southwestward along the Alaska Peninsula for more than 600 

he Peninsular (Alaska Peninsula) terrane. The Peninsular terrane 

inst Wrangellia, but the similarities between upper Paleozoic and 

imentary and volcanic units in the two terranes have been inter

cate that they were juxtaposed by no later than the Late Triassic, 

by the late Paleozoic. Only one small area of rocks that have 

d to the Peninsular terrane occurs within the parklands: on the 

 the Copper River near the mouth of the Cheshnina River, layered 

s crop out that are the easternmost occurrence of a Middle Jurassic 

afic assemblage. These rocks continue westward to Bernard Moun

sina, where layered ultramafi c rocks weather a conspicuous rusty 

ed on a sunny day from near Mile 80 on the Richardson Highway, 

ored tint contrasts markedly with surrounding dark, somber rocks.
Psc

Pgh

Phc

Qtw
Wrangell–Saint Elias—A Collage of Geologic Terranes 35
ality of volcanic and sedimentary rock units of the Pennsylvanian and 

ored rocks on the background ridge are composed of fossiliferous marine 

Formation (Pgh). Strata in the upper half of the Golden Horn contain 

ns. The Golden Horn forms bioclastic, reefl ike accumulations within the 

reek Formation (Phc). The sedimentary sequences apparently formed 

 by poorly bedded volcaniclastic rocks and andesitic flows, called the 

ek. In most places where it occurs in the region, the sedimentary part of 

olai Greenstone (

ng), which forms the west-dipping somber rocks north 

sic pelecypod-bearing strata (

d) intervenes between the Golden Horn 

 Mesozoic rocks are overlain unconformably by nearly fl at lying andesitic 

ngell Lava also underlies Chimney Mountain on the left edge of this view 

air (10,372 ft). (E.M. MacKevett, Jr.)

an Tetelna Volcanics along Cross Creek in the northern Wrangell 

eS2) and other sulfi de minerals. The Tetelna Volcanics along the north side 

reek Formation on the south side of the range. (D.H. Richter)

wing tightly folded thin-bedded rocks of the Lower Jurassic and Upper 

–Early Cretaceous mountain-building event that affected the entire region 

e folds indicates compression from the south (right to left in this view), 

ellia composite terrane. The light-colored dikes (Ti) intruding the McCarthy 

tic fl ows of the Wrangell Lava, which unconformably overlie the McCarthy 
Ti Ti

Ti

Ti

Ti

TiTi

Direction of

compression

Wrangell–Saint Elias—A Collage of Geologic Terranes 37
Mountain

hitistone River at the mouth of Grotto Creek. Gray cliffs and ledges 

zina Limestones, which overlie Triassic nonmarine basalt of the Nikolai 

 by brown-weathering thin-bedded rocks of the McCarthy Formation. 

 Limestone have been arched over into a recumbent anticlinal fold, which 

e fold outline is dashed where it is reconstructed to project above the 

eometry of this broken fold indicates southwest to northeast (left to right) 

uthern Wrangell Mountains and along the northern flank of the 

untains, Jurassic granitic plutons are widespread and intrude all 

f the Wrangellia and Alexander terranes. Several nonfoliated, 

granodioritic plutons occur north of the Chitina Valley between 

and the Gilahina River. South of the Chitina Valley, voluminous 

foliated plutons consisting of tonalite, quartz diorite, and granodio

ly parallel with older country rocks. One pluton stretches from 

r at least as far as the Canadian border and probably is continuous 

 Jurassic batholith that underlies Mt. Logan in Canada and extends 

Mt. Vancouver on the International Boundary, a total distance of 

 mi. Other Jurassic plutons are widespread in the Saint Elias 

iving rise to the name, “Saint Elias plutonic suite,” applied by 

logists to plutons of this age in the Yukon Territory. In fact, in the 

nt Elias region, most of the southern margin of the Wrangellia ter

underlain by Jurassic plutonic rocks. The plutons are interpreted to 

agmatic arc formed above a subduction zone during initial collision 

ch terrane (the McHugh Complex and correlative units—see next 

e Chugach and Prince William terranes) between about 170 and 150 

g the south edge of Wrangellia. So voluminous are the plutons 

y of the Chitina Valley that Alaskan geologists have borrowed the 

, Chitina arc.




McCarthy Formation Chitistone and Nizina Limestones 

Wrangell–Saint Elias—A Collage of Geologic Terranes 39
igh Cliffs” 

e of the Nizina River. The cliffs are composed of a synclinal fold more 

d to project above the current land surface.) From the base of the cliffs 

sists of the Triassic Nikolai Greenstone (

ng), Chitistone Limestone 

 right edge of the view, the northern limb of the syncline is folded back 

 overriding block.) The geometry of this paired fold and fault indicates 

n in the region in Late Jurassic time. On the left, the ridge is capped by 

ve an angular unconformity upon the folded Triassic sequence. Clearly, 

osed in the foreground ridges are Triassic marine carbonate sequences 

ea of today’s parklands, accretion of the Wrangellia composite 

een completed by Late Cretaceous time, no later than 85 m.y. 

uently, tectonic activity was driven by accretion of terranes south 

 Ranges fault. The most conspicuous features of today’s Wrangell 

he lofty young volcanoes that dominate the skyline in so many 

to form about 26 m.y. ago, long after Wrangellia had docked. Their 

attributable to interaction of other terranes to the south. Thus, 

volcanic field formed principally on subjacent Wrangellia, large 

eld also formed on the Alexander terrane and the Gravina-Nutzotin 

canic field will be discussed further in subsequent sections.


 



STEEP FAULT Direction of compression

Axis of

recumbent

fold

,800 ft

c

7,440 ft

ormation

one Limestone

Nikolai Greenstone

Wrangell–Saint Elias—A Collage of Geologic Terranes 41
exander
m

 accretion of fault-bounded slabs of deep-sea rocks against and 

Wrangellia composite terrane records Early Jurassic through mid

plating on the inner side of a subduction zone. These fault

s are called accretionary wedges and their successive underplating 

h has lifted up, placed on edge, or locally even tipped beyond 

segments of the Chugach and Prince William terranes, yielding 

omplete cross-sectional or edgewise views of both terranes.

p-sea rocks south of the Border Ranges fault system constitute one 

t and most extensive subduction-related accretionary complexes in 

e Chugach and Prince William terranes together form a composite 

Southern Margin composite terrane—that extends more than 1,300 

Alaska continental margin from as far west as the Sanak Islands 

Island on the east. These rocks form an outcrop width (including 

arts of the continental shelf) of as much as 125 mi. Their total volume 

000 mi3 (an estimate that does not include material already removed 

enough material to cover all of Alaska south of the Alaska Range 

more than 2 mi. The Southern Margin composite terrane underlies 

rcent of Wrangell–Saint Elias National Park and Preserve (fig. 12).

rangell–Saint Elias region, the Chugach terrane includes three 

sequences of Mesozoic age, and the Prince William terrane includes 

ene age. From north to south (and in order of decreasing age), 

he schist of Liberty Creek; (2) the McHugh Complex and melange

t Group; (3) the Valdez Group and flysch and basalt of the Yakutat 

ll as their metamorphosed equivalents in the Chugach and Saint 

ins; and (4) the Orca Group.

Wrangell–Saint Elias—A Collage of Geologic Terranes 43
Hugh Complex is a melange assemblage: it consists of a pervasively 

 variably metamorphosed array of deep-sea lithologies. The domi

 rocks are dark-weathering pillow basalt and related fragmental 

s, green-weathering altered volcanic tuff, and dark-gray argillite. In 

the McHugh contains subordinate lenses of medium-gray sandstone, 

reen, or maroon radiolarian chert, and light-gray limestone. The 

olcanogenic sandstone and andesitic tuff in the sedimentary units 

an active arc was a source for some of the sediment. Generally, the 

 dark argillite are chaotically mixed and intensely sheared, forming 

matrix within which are suspended lenses of the other lithologies 

raformational or exotic lithologies also are included in the melange 

ocks ranging in size from fractions of inches to miles. Limestone 

cks with Pennsylvanian, Permian, or Late Triassic fossils are known 

d areas outside the parklands, and ultramafic and mafic plutonic 

 present in several areas as conspicuous and large blocks. These 

rived from the adjacent Wrangellia and Peninsular terranes, which 

en located near the melange during its formation. 

west shore of Disenchantment Bay near the terminus of Turner 

ops of melange also are present and are structurally interleaved in 

roup. These rocks correlate in part with the McHugh Complex 

structural setting in the Yakutat terrane seaward of the Fairweather 

r melange assemblages extend discontinuously southeastward at 

 the east side of Chichagof Island, where they are truncated by 

Strait fault.

logic ages of radiolaria from beds within the melange range from 

ic to mid-Cretaceous, indicating multiple episodes of formation 

t 230 and 90 m.y. ago. The mixing of oceanic crustal rocks, 

etritus, and fragments of older rocks derived from the southern 

 Wrangellia composite terrane indicates disruption and accretion at 

plate margin during times of active subduction beneath Wrangellia. 

eontologic ages correspond in general with the radiometric ages of 

ed during magmatism in the adjacent evolving arcs.
BRFS

Debris flow

 SKOLAI ARC

ROCKS

(WRANGELLIA)

 Mt. Queen Mary

 Mt. Vancouver

n 

Debris

flow

Art Lewis Glacier 

Fiord is on the left; view is to the northwest from near the extreme 

er Paleozoic rocks of the Skolai arc (the Wrangellia terrane) on the right 

er fault (FF) is located at the base of the mountain front near the left edge. 

igh peaks in the background are, from left to right, Mt. St. Elias (18,008 

2,800 ft). Note the strongly curving moraines near the right edge of Art 

patches of brown-colored debris on the surface of Art Lewis Glacier near its 

of the glacier, but have now moved downglacier from their sources. If their 

Wrangell–Saint Elias—A Collage of Geologic Terranes 45

acier 

oreground spur are the 

g radiolarian chert, a rock 

hologies within an active 

t. Logan; it is eroded from a Late 

 assembled and deformed in 

ange of the McHugh Complex. A crude layering, which is defi ned by the 

sts, dips into the outcrop from upper right to lower left. This fabric is 

se shearing at all scales. At this location on Goat Creek Glacier south of 

 Valley, the clasts consist principally of metamorphosed plutonic rocks 

that occur in the nearby southern margin of the Wrangellia terrane. The 

lange is principally granulated mafi c volcanic material, probably derived 

ust. At other locations, the clasts may be much larger, in some cases 

e in maximum dimension, and the matrix may consist of dark argillite. 

Wrangell–Saint Elias—A Collage of Geologic Terranes 47


Mountains 

h Mountains in the vicinity of the Little Bremner River. Much of the 

aldez Group, which, in this view, is mostly thick bedded sandstone dipping 

y episodic underplating from the south of additional fault-bounded slabs 

ach terrane until it has reached a structural thickness of more than 9 mi, 

nary wedges of the Paleogene Prince William terrane outboard (south) 

nd basalt that have been metamorphosed to epidote-amphibolite 

p an east-west-trending structurally bound block 50 mi long and 

 mi that underlies the highest part of the Saint Elias Mountains 

luding Mt. St. Elias. These highly metamorphosed rocks are 

inst lower grade metamorphic rocks of the Valdez Group (Chugach 

e north along extensions of the Contact and Fairweather fault 

e they apparently merge beneath the icefields of Columbus and 

ers. To the south, the block is bounded by the Chugach and St. 

which emplace the block above unmetamorphosed Cretaceous and 

s of the Yakutat terrane (see next section). The metamorphosed 

salt of the St. Elias structural block are similar lithologically and 

o rocks of the Chugach terrane south of the Alsek River in Glacier 

 Park. If this correlation is correct, the structural block has been 

roximately 200 km northwestward by dextral offset along the 

ault.

 the Copper River and the vicinity of Mt. St. Elias, the Contact 

marks the south edge of the Mesozoic Chugach terrane. Within 

, the fault is not exposed, but is strongly expressed topographically, 

e nearly linear, glacier-filled trough of the Bagley Ice Field (fig. 

the parklands, the Contact fault is well exposed in the Prince 

nd region, where it forms sinuous traces suggestive of oblique 

g followed by minor dextral offset. The 50 million-year-old Tom 

intrudes both upper and lower plates of the Bagley segment of the 

system, indicating that little if any post-Eocene displacement has 

g the fault system in the eastern Chugach Mountains.
submarine ridges or chains of seamounts that were detached from 

oving Kula plate as it was being subducted beneath the Alaska 

argin. A contemporary analogy is provided on the Pacific oceanic 

he Gulf of Alaska, where volcanic edifices such as the Kodiak and 

unts are moving directly toward the subduction zone in the Aleutian 

 the seamounts enter the trench, they likely will be detached from 

eanic plate to be incorporated within accreting prisms of terrigenous 

ved from the Alaska continental margin.

tigraphic thickness of the Orca Group in Prince William Sound 

ouple of miles, but pervasive tight folding, imbricate faulting, 

il control preclude representative measurements. The entire Orca 

fected by the same regional thermal event at about 50 m.y. ago that 

ed and partially melted rocks of the Chugach terrane. However, 

morphic grades are generally less than for rocks of the Chugach 

, the entire thickness of the Prince William terrane had been 

formed, intruded, and accreted to the Chugach terrane within a span 

an 10 million years. This remarkably dynamic interval represents 

-fold increase in the pace of accretion, coinciding with a period of 

ence of the Kula and North American crustal plates.

Wrangell–Saint Elias—A Collage of Geologic Terranes 51
Ic 

west on Bagley Ice Field north of Natural Arch, taken in early July 1959 e Field 

ring the second known crossing of the ice fi eld on foot. Nearby Mount 

or one of a pair of prospectors (the other being James Barkley) who fi rst 

. The Bagley fault (of the Contact fault system) follows the ice-fi lled 

h and ocean-fl oor basalt of the Orca Group on the left from metamorphosed 

 tuff, and minor fl ysch of the Valdez Group on the right. At this location, the 

cross and feeds the enormous south-fl owing piedmont lobe of the Bering 

ell as the north-fl owing Tana Glacier, out of view to the right. In this view, 

bb are preparing to continue the day’s traverse; note the long aluminum 

es when crossing crevassed areas of the ice. (D.J. Miller)
Wrangell–Saint Elias—A Collage of Geologic Terranes 53
akutat

ore extension of the Kayak Island structural zone. To the east, 

gainst the Fairweather fault, which is the northeastern boundary 

terrane. The Transition fault system (fig. 9) marks the southern 

most of the Yakutat terrane, separating it from the Pacific plate, 

 has sustained 125 mi of oblique underthrusting during Cenozoic 

nsition fault system intersects the Fairweather fault seaward of 

nd in southeastern Alaska. The nearly vertical dextral strike-slip 

ult marks the northeast boundary of the Yakutat terrane. It is not 

 park, but between Hubbard Glacier and Cross Sound, its surface 

d by broad shear zones in bedrock and a topographic trench as 

i wide (fig. 29). Holocene scarps and dextrally offset drainages 

e trace in many places, and dextral and vertical displacements of 

respectively, occurred during the 1958 Lituya Bay earthquake. 

er fault forms part of a transform fault system between the Pacific 

erican crustal plates and has undergone at least 375 mi of dextral 

n the late Cenozoic. South of its intersection with the Transition 

he Fairweather fault (and its southern continuation in British 

 Queen Charlotte fault) accommodates all displacement between 

 North of the intersection, displacement may have been shared 

airweather and Transition fault systems during parts of the late 

day, however, the Yakutat terrane is moving mostly with the Pacific 

long the Fairweather fault) at about 2 in./yr relative to North 

ossibly only at about 0.16 in./yr relative to the Pacific plate (that 

ransition fault).
rphosed Cretaceous fl ysch and 

of the Yakutat Group (Ky). Thus, 

errane that are of approximately 

h American tectonic plate and 

nd are being thrust beneath 

uake of 1979 ruptured a 

e fault (and plate boundary) 

e dextral strike-slip fault 

rie Glacier in the distance. The 

nfluenced by dextral offset 

orth American plate (on the right), 

e Chugach terrane. Prominent 

 (10,070 ft). (George Plafker)

the Dangerous River zone, basement rocks for the Yakutat terrane 

e oceanic basalt, as determined from several dredge samples on 

inental shelf, and the Yakutat Group is not present. Immediately 

ks are lower Eocene through Oligocene clastic sequences contain

al and volcanic rocks. The composite thickness of this section is 

 ft, whereas the correlative section east of the Dangerous River 

han 6,600 ft thick and has different units in its lower part. These 

quences of the Yakutat terrane have no analogs in the inboard ter

are overlapped by Miocene to Holocene marine and glacial-marine

as much as 16,400 ft thick, which also overlap the Prince William 

 west and the Chugach terrane to the east.

Wrangell–Saint Elias—A Collage of Geologic Terranes 55









 Mt. Seattle

NUNATAK FIORD

CHUGACH

TERRANE 

Wrangell–Saint Elias—A Collage of Geologic Terranes 57
 Mt. Newton

 Mt. St. Elias

CH TERRANE

 YAKUTAT GROUP
ills

dge

s is underlain by strongly 

utat is faulted against, and 

r-colored ridges in the left 

iocene part of the Yakataga 

chistose rocks of the Mesozoic 

s. Haydon Peak (11,945 ft) and 

in the foreground is about 2 mi 

d terrestrial to marginal-marine 

 coal bearing. They were 

c conditions. They are typical 

 of the ridge are related to 

structurally higher rocks on 

of the Upper(?) Jurassic and 

ch terrane. (George Plafker)

Wrangell–Saint Elias—A Collage of Geologic Terranes 59

Mt. St. Elias

Wrangell–Saint Elias—A Collage of Geologic Terranes 61
S

Wrangell–Saint Elias—A Collage of Geologic Terranes 63

has been thrust at least 125 mi beneath the Prince William terrane along its northwest boundary. The Yakutat terrane must have been thrust at least 140 mi along its northern boundary beneath the Wrangell Mountains by Miocene time, the amount required for it to reach 60 mi depth and institute crustal melting and andesitic volcanism that began about 26 m.y. ago (see later section). As a result of this convergence, a wide fold-and-thrust belt has formed in the Cenozoic sequences and extends from the Pamplona zone to the north and west margins of the terrane (fig. 9). The Yakataga anticline, which extends westward from the 

Guyot Hills through Mt. Eberly to the toe of Yakataga Glacier, is a conspicuous fold in this zone (fig. 33). To its south, the Sullivan anticline is faulted along its 

crest, and strata on the seaward (south) side of the fault have been overturned so that they dip north. Such structural complexity reflects continued convergence 

across the widening zone. As folds grew and tightened in response to a continuing push of the Yakutat terrane from the south, in many places their crests broke and their seaward parts below the break were driven beneath their landward parts, in some places being overturned by the drag of the overriding plate. In addition, the fold-and-thrust belt migrated seaward over time. Faulted anticlines in a sedimentary section that is as young as Pleistocene are present near the seaward edge of the Pamplona zone, indicating growth of young structures beneath the outer continental shelf. They were targets for unsuccessful exploratory oil drilling in the northern Gulf of Alaska in the 1980’s.
S

Wrangell–Saint Elias—A Collage of Geologic Terranes 63

has been thrust at least 125 mi beneath the Prince William terrane along its northwest boundary. The Yakutat terrane must have been thrust at least 140 mi along its northern boundary beneath the Wrangell Mountains by Miocene time, the amount required for it to reach 60 mi depth and institute crustal melting and andesitic volcanism that began about 26 m.y. ago (see later section). As a result of this convergence, a wide fold-and-thrust belt has formed in the Cenozoic sequences and extends from the Pamplona zone to the north and west margins of the terrane (fig. 9). The Yakataga anticline, which extends westward from the 

Guyot Hills through Mt. Eberly to the toe of Yakataga Glacier, is a conspicuous fold in this zone (fig. 33). To its south, the Sullivan anticline is faulted along its 

crest, and strata on the seaward (south) side of the fault have been overturned so that they dip north. Such structural complexity reflects continued convergence 

across the widening zone. As folds grew and tightened in response to a continuing push of the Yakutat terrane from the south, in many places their crests broke and their seaward parts below the break were driven beneath their landward parts, in some places being overturned by the drag of the overriding plate. In addition, the fold-and-thrust belt migrated seaward over time. Faulted anticlines in a sedimentary section that is as young as Pleistocene are present near the seaward edge of the Pamplona zone, indicating growth of young structures beneath the outer continental shelf. They were targets for unsuccessful exploratory oil drilling in the northern Gulf of Alaska in the 1980’s.
taga Ridge

 Mt. Eberly

OGIVES

ICEFALL

Wrangell–Saint Elias—A Collage of Geologic Terranes 65
taga Ridge

 Mt. Eberly

OGIVES

ICEFALL

Wrangell–Saint Elias—A Collage of Geologic Terranes 65
formity 4? 

mation—a dynamic tectonic regime that persists today as the Alaskan continental margin continues to absorb the northwestward motion of the accreting Yakutat terrane. (George Plafker)

rr Hills

Wrangell–Saint Elias—A Collage of Geologic Terranes 67
formity 4? 

mation—a dynamic tectonic regime that persists today as the Alaskan continental margin continues to absorb the northwestward motion of the accreting Yakutat terrane. (George Plafker)

rr Hills

Wrangell–Saint Elias—A Collage of Geologic Terranes 67
mity

Mt. Cook
nconformity, highlighted by dashed line in the lower part of the view, in the glacial-marine Yakataga 

spina Glacier. Mt. Cook (13,760 ft) is in the right background. The banded alternation of dark pebbly 

nes is characteristic of the Yakataga Formation. Note that many sandstone strata, particularly in the 

nd discontinuous. In part, these strata may be so-called “push moraines,” soft sediment deformed 

ded ice, and, in part, slumps from rapidly accumulating water-laden sediment in a tectonically active 

mity may be an unusually large channel, scoured from a soft, water-saturated seabed, but elsewhere, 

ga unequivocably indicate the presence of growing structures within the depositional basin—no doubt 

f the Yakutat terrane against and beneath the continental margin. The rusty-weathering knob on the left 

on. Its normal stratigraphic position is beneath the Yakataga Formation; here, the Yakataga has been 

Sawteeth on line marking the fault surface are on the upper plate.) (M.D. Wilson)

s. The area of the Wrangell Mountains 

he north edge of the parklands contains 

ault systems. The Denali displays no 

s, but calculated dextral strike-slip 

om 0.3 to 0.4 in./yr. Thus, the fault is 

but large earthquakes that may rupture 

ength and have horizontal displacements 

ke-slip Totschunda fault, a major 

eismicity and shows no evidence of 

ever, calculated slip rates for the last 

8 in./yr, suggesting that infrequent large 

hunda and possibly adjacent parts of 

e parklands in the Chugach and Saint 

ve and has generated several powerful 

Charlotte

Fairweather fault system on the east (fig. 9) through a complicated 

network of faults partitioning lesser amounts of oblique dextral displacement along their surfaces. Thus, during late Cenozoic time, faults as far inboard as the Denali and Totschunda faults near the north edge of the Wrangell–Saint Elias region and faults in outboard positions, such as the Transition fault and the seaward end of the Pamplona zone, have ruptured, sharing part of the relative motion between the Pacific and North American plates. Faults in intermediate positions, such as the Chugach–St. Elias fault, the Castle Mountain fault north of Anchorage, and the Patton Bay fault in Prince William Sound, also have ruptured in response to the plate motions. 

Faults along the primary boundary between the Pacific and North American 

plates have broken at several places during the past 100 years. In September 1899, four major earthquakes (estimated moment magnitudes between 7.0 and 8.0) apparently ruptured the plate boundary segment between Yakutat Bay and Yakataga (fig. 36). At least two of these shocks were roughly the same magnitude as the great San Francisco earthquake of 1906. A wave-cut platform in the vicinity of Bancas Point on the north side of Yakutat Bay was uplifted as much as 46 ft during those events (see fig. 77).

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 69
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 71

de and was accompanied by regional 

of Alaska from the Bering Glacier 

tation by seismic shaking, ground 

mis, and seiches was even more wide

s region was located 100 or more 

m Sound, snowslides and landslides 

rticularly in areas of unconsolidated 

flats, networks of cracks were particu

 seeds quickly lodged in the cracks, 

vegetation patterns. In the area of the 

ned by dwarf fireweed still is visible 

hquake.

quake (magnitude 7.5) ruptured the 

ath the Jefferies Glacier, approxi

 zone buckles to dip more steeply 

k triggered a large landslide from 

cinity of Cascade Glacier (fig. 37) and 

nsolidated deposits along the margin 

mber 1987 and March 1988 (magnitude 

award of the Pamplona zone. These 

ation of the south edge of the Yakutat 

xtension of the Aleutian megathrust.

tal zone is indicated by seismic activity, 

uplift at rates as great as 0.4 in./yr. 

hquakes and the generation of tsunamis 

here is very little data on how often.

outcrops of similar volcanic rocks (fig. 39) extend southeastward to the vicinity of Icy Strait in Glacier Bay National Park and Preserve, and also are present on the south end of Admiralty Island in the Alaskan Panhandle. Correlation of the Admiralty Island Volcanics with the rocks near Icy Strait, if correct, documents about 75 mi of post-Oligocene dextral slip along the Chatham Strait fault.

The loftiest summits in the Wrangell Mountains and at least two of the 

high summits in the Saint Elias Mountains—Mt. Bona (16,421 ft), and Mt. Churchill (15,638 ft)—are composed primarily of voluminous piles of volcanic rocks or shallow intrusive rocks that formed beneath the volcanic edifices. At least 12 major eruptive centers occur in the Alaskan part of the volcanic field; activity began about 26 m.y. ago and has progressed generally northwesterly to reach Mt. Wrangell, the broad shield-shaped volcano rising above the southwestern Copper River Basin, which is still mildly active. Although no lavaproducing eruptions have been documented in the last 200 years, Mt. Wrangell’s summit caldera still has active fumaroles and occasionally emits minor bursts of ash, which darken the ice-covered summit. No other volcanoes in the field have been active in recent times. However, in the Copper River Basin west of Mt. Drum, three springs that produce warm, CO2-enriched, saline mud are thought to be the result of degassing from a deep-seated magma body still present at depth. These so-called mud volcanoes (see fig. 63) have built up mounds of 

mud as much as 300 ft high and 8,000 ft in diameter, resembling small shield

volcanoes. A small caldera near the summit of Mt. Churchill apparently was the source of two major eruptions of the White River Ash about 1,890 and 1,250 years ago. The two lobes of the White River Ash blanket an aggregate area of more than 130,000 mi2 northward along the International Boundary and 

northeastward in the Yukon Territory.
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 71

f of Alaska from the Bering Glacier 

astation by seismic shaking, ground 

namis, and seiches was even more wide

ias region was located 100 or more 

iam Sound, snowslides and landslides 

particularly in areas of unconsolidated 

r flats, networks of cracks were particu

ne seeds quickly lodged in the cracks, 

l vegetation patterns. In the area of the 

efined by dwarf fireweed still is visible 

rthquake.

hquake (magnitude 7.5) ruptured the 

eath the Jefferies Glacier, approxi

ff zone buckles to dip more steeply 

ock triggered a large landslide from 

vicinity of Cascade Glacier (fig. 37) and 

onsolidated deposits along the margin 

vember 1987 and March 1988 (magnitude 

eaward of the Pamplona zone. These 

tation of the south edge of the Yakutat 

n extension of the Aleutian megathrust.

astal zone is indicated by seismic activity, 

e uplift at rates as great as 0.4 in./yr. 

rthquakes and the generation of tsunamis 

t there is very little data on how often.

of Icy Strait in Glacier Bay National Park and Preserve, and also are present on the south end of Admiralty Island in the Alaskan Panhandle. Correlation of the Admiralty Island Volcanics with the rocks near Icy Strait, if correct, documents about 75 mi of post-Oligocene dextral slip along the Chatham Strait fault.

The loftiest summits in the Wrangell Mountains and at least two of the 

high summits in the Saint Elias Mountains—Mt. Bona (16,421 ft), and Mt. Churchill (15,638 ft)—are composed primarily of voluminous piles of volcanic rocks or shallow intrusive rocks that formed beneath the volcanic edifices. At least 12 major eruptive centers occur in the Alaskan part of the volcanic field; activity began about 26 m.y. ago and has progressed generally northwesterly to reach Mt. Wrangell, the broad shield-shaped volcano rising above the southwestern Copper River Basin, which is still mildly active. Although no lavaproducing eruptions have been documented in the last 200 years, Mt. Wrangell’s summit caldera still has active fumaroles and occasionally emits minor bursts of ash, which darken the ice-covered summit. No other volcanoes in the field have been active in recent times. However, in the Copper River Basin west of Mt. Drum, three springs that produce warm, CO2-enriched, saline mud are thought to be the result of degassing from a deep-seated magma body still present at depth. These so-called mud volcanoes (see fig. 63) have built up mounds of 

mud as much as 300 ft high and 8,000 ft in diameter, resembling small shield

volcanoes. A small caldera near the summit of Mt. Churchill apparently was the source of two major eruptions of the White River Ash about 1,890 and 1,250 years ago. The two lobes of the White River Ash blanket an aggregate area of more than 130,000 mi2 northward along the International Boundary and 

northeastward in the Yukon Territory.
 

Mt. Augusta

YAKUTAT GROUP

SCADE GLACIER
assiz Glacier (on the left). Similar debris avalanches were triggered at many locations in the Chugach 

quake (magnitude 9.2). Over the ensuing 30+ years, many debris fans have moved downglacier 

areas; their offset provides a means to measure aggregate surface glacier movement during the 

ed by rocks in the upper plate of the St. Elias fault and consists of schistose flysch and basalt of the 

proximate position of the fault; sawteeth are on the upper plate. The highest peak is Mt. Augusta 

m the Chugach Mountains across the southeastern part of the Copper River Basin to Mt. Drum (12,010 

14,136 ft). These three high peaks near the west end of the Wrangell Mountains display the varying 

t. Drum (left) is a composite stratovolcano, consisting of tabular dacite to andesite lava fl ows and 

ite domes. Its steeper profi le is, in part, related to climactic explosive events that destroyed much of 

. Mt. Sanford (center) displays an intermediate profi le and consists of coalesced lava fl ows from at 

t) is a broad shield volcano built chiefl y by the accumulation of hundreds of voluminous andesite fl ows. 

phology, it is the youngest volcano in the western Wrangell Mountains. Mt. Wrangell still is active, as 

craters near its summit that occasionally emit small bursts of ash. (G.R. Winkler)

st tongue of Hole in the Wall Glacier, which spills into the valley of Skolai Creek from an ice fi eld high to 

rimarily of nearly fl at lying andesitic fl ows of the Miocene and younger Wrangell Lava. The location of 

 overlie volcanic and sedimentary units of the Pennsylvanian and Permian Skolai Group, which form the 

ole in the Wall Glacier has receded 0.5 to 1 mi and thinned 300 to 600 ft recently, no longer extending to 

e. It remains active, however, and its ice falls are severely crevassed. (E.M. MacKevett, Jr.)

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 73
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 75
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 75
Figure 41. Fossiliferous marine tillite of the Yakataga Formation. Note that the pebbly siltstone is replete with clam fossils, yet also has numerous pebble and cobble clasts. If the clasts had been deposited by running water, the environment would have been too disturbed for clam growth; the clasts must have been carried to the site on rafts of ice, which melted—dropping the stones into the marine bottom sediment where the clams were living. (George Plafker)

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 77
Figure 41. Fossiliferous marine tillite of the Yakataga Formation. Note that the pebbly siltstone is replete with clam fossils, yet also has numerous pebble and cobble clasts. If the clasts had been deposited by running water, the environment would have been too disturbed for clam growth; the clasts must have been carried to the site on rafts of ice, which melted—dropping the stones into the marine bottom sediment where the clams were living. (George Plafker)

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 77
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 79
The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 79
uffs along the Copper River and its tributaries, volcanic debris flows and other deposits that probably originated 

atified with the alluvial, lacustrine, and glacial deposits. Taken together, the bluffs provide excellent cross-sectional 

ternary deposits.

evidence for the existence of glacial Lake Atna. The fl oor of the central Copper River Basin is generally a smooth, 

-grained deposits, commonly a stony silt and locally well laminated silt and clay. Strandlines marking former shores 

rather subtle, at several altitudes. In the western part of the basin, a major strandline occurs at about 2,450 ft, and 

2; another major strandline, well formed around the base of Mt. Drum, is at about 2,300 ft. Lower strandlines are 

aerial photographs at about 1,900 ft, 1,800 ft, and 1,600 ft. Many of these strandlines lie within parklands east of 

y fl anking present-day tributaries of the Copper River, deltas formed at the margins of Lake Atna where ancestral 

tas preserve locally prominent gravel deposits.

f the Copper River Basin are evidences of higher level lakes, and it is not clear whether some of these 

 lakes that never were connected to the main lake. In the western part of the basin, a shoreline is present 

st part of the basin within parklands along the Nabesna Road and the Copper River, a lake at a level as high 

smoothed, subdued nature of the topography and channels that lead to small deltas at this and somewhat lower 

e Boomerang, and it is thought to have formed separately from Lake Atna as the Copper River glacier retreated 

untains still extended across part of the upper basin in the vicinity of Cobb Lakes just north of the Copper River. 

evel of Lake Boomerang lowered until it merged with the separately existing 2,450-ft level of Lake Atna when 

bly had no outlet, although it may have drained repeatedly during this time when it succeeded in overtopping 

In due course, however, the damming glaciers were high enough and the lake large enough that an equilibrium 

ntained itself without any outlet. At times of highest lake levels, however, outlets probably existed to the northeast 

er but fl owing in a direction opposite to that of the present river) and in the northwest along Tyone Creek and into 

dlines probably formed at these times of stable thresholds. During the waning stages of the Wisconsin glaciation, 

red, and the lake migrated to the lower basin. As the lake level lowered, the Copper River and its tributaries became 

or of the lake as streams graded to successively lower base levels. Thus, all the major rivers in the basin presently 

t below the general level of the basin that formerly was the bottom of Lake Atna.

y down the canyons of the Copper River to the Gulf of Alaska. What a flood that final drainage must have been! 

 in the canyons above the mouth of the Bremner River, the canyon having been scoured to bedrock, probably 

lower lake level may have reformed at times, however, as glaciers readvanced in the canyons, and lakes may 

eginning of the next major glaciation at some unknown future time, when a glacial lake may form again in the 

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 81
uffs along the Copper River and its tributaries, volcanic debris flows and other deposits that probably originated 

atified with the alluvial, lacustrine, and glacial deposits. Taken together, the bluffs provide excellent cross-sectional 

ternary deposits.

evidence for the existence of glacial Lake Atna. The fl oor of the central Copper River Basin is generally a smooth, 

-grained deposits, commonly a stony silt and locally well laminated silt and clay. Strandlines marking former shores 

rather subtle, at several altitudes. In the western part of the basin, a major strandline occurs at about 2,450 ft, and 

2; another major strandline, well formed around the base of Mt. Drum, is at about 2,300 ft. Lower strandlines are 

aerial photographs at about 1,900 ft, 1,800 ft, and 1,600 ft. Many of these strandlines lie within parklands east of 

y fl anking present-day tributaries of the Copper River, deltas formed at the margins of Lake Atna where ancestral 

tas preserve locally prominent gravel deposits.

f the Copper River Basin are evidences of higher level lakes, and it is not clear whether some of these 

 lakes that never were connected to the main lake. In the western part of the basin, a shoreline is present 

st part of the basin within parklands along the Nabesna Road and the Copper River, a lake at a level as high 

smoothed, subdued nature of the topography and channels that lead to small deltas at this and somewhat lower 

e Boomerang, and it is thought to have formed separately from Lake Atna as the Copper River glacier retreated 

untains still extended across part of the upper basin in the vicinity of Cobb Lakes just north of the Copper River. 

evel of Lake Boomerang lowered until it merged with the separately existing 2,450-ft level of Lake Atna when 

bly had no outlet, although it may have drained repeatedly during this time when it succeeded in overtopping 

In due course, however, the damming glaciers were high enough and the lake large enough that an equilibrium 

ntained itself without any outlet. At times of highest lake levels, however, outlets probably existed to the northeast 

er but fl owing in a direction opposite to that of the present river) and in the northwest along Tyone Creek and into 

dlines probably formed at these times of stable thresholds. During the waning stages of the Wisconsin glaciation, 

red, and the lake migrated to the lower basin. As the lake level lowered, the Copper River and its tributaries became 

or of the lake as streams graded to successively lower base levels. Thus, all the major rivers in the basin presently 

t below the general level of the basin that formerly was the bottom of Lake Atna.

y down the canyons of the Copper River to the Gulf of Alaska. What a flood that final drainage must have been! 

 in the canyons above the mouth of the Bremner River, the canyon having been scoured to bedrock, probably 

lower lake level may have reformed at times, however, as glaciers readvanced in the canyons, and lakes may 

eginning of the next major glaciation at some unknown future time, when a glacial lake may form again in the 

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 81
Malaspina Glacier

Malaspina Lake

(1982)

≈ 1791–1823

1948

≈ 1750

≈ 1700

GULF OF ALASKA

Malaspina Lake

(1948)

l

l

l

l

l

l

l

l

l l l l l l l l l l l l l l l l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l l l

l

l

l

YAKUTAT–DISENCHANTMENT BAY LOBE

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 83
Malaspina Glacier

Malaspina Lake

(1982)

≈ 1791–1823

1948

≈ 1750

≈ 1700

GULF OF ALASKA

Malaspina Lake

(1948)

l

l

l

l

l

l

l

l

l l l l l l l l l l l l l l l l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l l l

l

l

l

YAKUTAT–DISENCHANTMENT BAY LOBE

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 83
bard Glacier 

ast of part of the terminus of Hubbard Glacier. The moraine-covered terminus of Turner Glacier is in the 

ght, and Gilbert Point is on the mainland in the right background. Arrows show direction of glacier ß ow. 

er background. Even a short advance of Hubbard Glacier is sufÞ cient to dam Russell Fiord, creating 

Point is a former outlet to the Yakutat foreland. Once a ÒLakeÓ Russell is formed, if it rises more than 

Old Situk Creek across the Yakutat foreland to the open Gulf of Alaska. (George Plafker)

hotographs taken in 1941 show the lake at 

edmont glaciers in Alaska, the Mala

urface moraines that are strikingly folded 

of the Hitchcock Hills. These folds 

Marvine, and other tributary glaciers, 

by large-scale, but short-lived forward 

have been noted in the eastern Wrangell 

ains, and the Saint Elias Mountains 

mmediately adjacent to one another 

e glacier is surging forward while its 

ng. Where such glaciers join, their 

very complex patterns. Like Malaspina, 

raines attributable to multiple surges.

A submerged moraine at the west end of Disenchantment Bay resulted from a temporary readvance that culminated between 1700 and 1791. At the time of explorer Malaspina’s search for the fabled Northwest Passage in 1792, he navigated Yakutat Bay without difficulty, but was turned back in the vicinity of Haenke Island by floating ice that was impenetrable to his vessels. The name he gave to the fiord at the head of Yakutat Bay, Desengaña, indicates his disenchantment that no passage existed. Between 1792 and 1894, the terminus of Hubbard Glacier resumed its retreat to a position about 2 mi east of its current location near Osier Island. Since 1894, when systematic mapping of its terminus began, Hubbard Glacier has slowly readvanced, threatening to seal the mouth of Russell Fiord (fig. 44). In early 1986, the threat came true: Hubbard Glacier advanced sufficiently to block the connection between Disenchantment Bay and Russell Fiord. The water behind the glacial dam began to rise, creating a temporary “Lake” Russell. In the 5 months that the dam held, the lake rose about 80 ft above sea level, but in early October 1986 the dam failed and the lake emptied completely within the course of 28–30 hours. A new closure will likely take place in the near future unless Hubbard Glacier’s slow advance is stabilized or reversed.

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 85
bard Glacier 

ast of part of the terminus of Hubbard Glacier. The moraine-covered terminus of Turner Glacier is in the 

ght, and Gilbert Point is on the mainland in the right background. Arrows show direction of glacier ß ow. 

er background. Even a short advance of Hubbard Glacier is sufÞ cient to dam Russell Fiord, creating 

Point is a former outlet to the Yakutat foreland. Once a ÒLakeÓ Russell is formed, if it rises more than 

Old Situk Creek across the Yakutat foreland to the open Gulf of Alaska. (George Plafker)

hotographs taken in 1941 show the lake at 

edmont glaciers in Alaska, the Mala

urface moraines that are strikingly folded 

of the Hitchcock Hills. These folds 

Marvine, and other tributary glaciers, 

by large-scale, but short-lived forward 

have been noted in the eastern Wrangell 

ains, and the Saint Elias Mountains 

mmediately adjacent to one another 

e glacier is surging forward while its 

ng. Where such glaciers join, their 

very complex patterns. Like Malaspina, 

raines attributable to multiple surges.

A submerged moraine at the west end of Disenchantment Bay resulted from a temporary readvance that culminated between 1700 and 1791. At the time of explorer Malaspina’s search for the fabled Northwest Passage in 1792, he navigated Yakutat Bay without difficulty, but was turned back in the vicinity of Haenke Island by floating ice that was impenetrable to his vessels. The name he gave to the fiord at the head of Yakutat Bay, Desengaña, indicates his disenchantment that no passage existed. Between 1792 and 1894, the terminus of Hubbard Glacier resumed its retreat to a position about 2 mi east of its current location near Osier Island. Since 1894, when systematic mapping of its terminus began, Hubbard Glacier has slowly readvanced, threatening to seal the mouth of Russell Fiord (fig. 44). In early 1986, the threat came true: Hubbard Glacier advanced sufficiently to block the connection between Disenchantment Bay and Russell Fiord. The water behind the glacial dam began to rise, creating a temporary “Lake” Russell. In the 5 months that the dam held, the lake rose about 80 ft above sea level, but in early October 1986 the dam failed and the lake emptied completely within the course of 28–30 hours. A new closure will likely take place in the near future unless Hubbard Glacier’s slow advance is stabilized or reversed.

The Dynamic Parklands —Continually Reshaped by Earthquakes, Volcanoes, and Glaciers 85
1

NATIONAL PARK

NATIONAL

PRESERVE

NATIONAL

PRESERVE

NICKE GLACIER

RTIN RIVER GL

CIER

BERING GLACIER

BAGLEY ICEFIELD

GUYOT GLACIER

TANA GLACIER

JEFFERIES GLACIER

YAHTSE GLACIER

KENNICOTT

NABES NA GLACIER

COPPER 

CHISANA GLACIER

GLACIER

ROOT GLACIER

HAWKINS GLACIER BARNARD GLACIER

KLUTLAN GLACIER

RUSSELL GLACIER

CHITINA GLACIER

WALSH GLACIER

DONJEK GLACIER

STEELE GLACIER

LOGAN GLACIER

COLUMBUS GLACIER SEWARD GLACIER

MALASPINA GLACIER

SEWARD GLACIER

AGASSIZ GLACIER LIBBEY GLACIER

OG LI VIE GLACIER

HUBBARD GLACIER

LOWELL GLACIER

KASKAWULSH

HUBBARD GLACIER

GLACIER

ALVER STONE GLACIER

VALERIE GLACIER

TURNER GLACIER

WEST

NUNATAK GLACIER

Long

Lake Kennicott

River

Hidden

Creek

Lake 

Malaspina

Lake

Oily

Lake

Ross Green 

Lake

Braye

Lakes

Solo

Lake

Rock

Lake

Ptarmigan

Lake

Chitistone

Falls

Clear

Creek

Hanagita

Lakina

Gilahina

Kuskulana

Nizina

McCarthy

Cr

River

River

River

River

Tana River

River

Chitina

River

Klu

River

River

River

River

Gra

Creek

nite

Lakes

White

Skolai

Toby Creek

Chitistone River

Creek

River

Beaver

Creek

White 

Kluane

River

Donjek

Duke River

KLUANE LAKE

River

a

er

ICY BAY

YAKUTAT BAY

RUSSELL FJORD

NUNATAK FJORD

DISENCHAN TMENT BAY

Yahtse River

GULF OF ALASKA

KLUANE

NATIONAL PARK

KLUANE

GAME

SANCTUARY

Chisana

Destruction Bay

Kennicott

McCarthy

Strelna

Chokosna

Dan Creek

May Creek

Burwash Landing

Alaska Highway

Cape Suckling

Cape

Yakataga

Point Manby

Haenke

Island

Atna Peaks

untain

Skolai Pass

Castle

Mountain

Chitistone Peak

CHAIX

HILLS

KARR HILLS

GUYOT HILLS

SAMOVAR HILLS

SUCKLING

HILLS

Juniper

Island

BRITISH COLUMBIA

YUKON TERRITORY

UNITED STATES CANADA

UNITED STATES

CANADA

ALASKA

YUKON TERRITORY

CANADA

UNITED STATES

N TERRITORY

ALASKA

G R A N I T E R A N G E

MACCOLL RIDGE

UNIVERSITY RANGE

R O B I N S O N M O U N T A I N S

WAXELL RIDGE

S L I N G R A N G E

U

N

T

A I N S

N S

W

R

A

N

G E L L M

O

U

N

T

A I N

S

S

A I N

T

E

L I A

S

M

O

U

N

T A I N

S

I C E F I E L D R A N G E S

0

0 10 20 MILES

10 20 KILOMETERS

KotsinaKuskulana

district

district

Chisana

district

McCarthyNizina

district

Bremner

district

Bering River

coal field

Gold and Copper—Or Was It Copper and Gold? 87
1

NATIONAL PARK

NATIONAL

PRESERVE

NATIONAL

PRESERVE

NICKE GLACIER

RTIN RIVER GL

CIER

BERING GLACIER

BAGLEY ICEFIELD

GUYOT GLACIER

TANA GLACIER

JEFFERIES GLACIER

YAHTSE GLACIER

KENNICOTT

NABES NA GLACIER

COPPER 

CHISANA GLACIER

GLACIER

ROOT GLACIER

HAWKINS GLACIER BARNARD GLACIER

KLUTLAN GLACIER

RUSSELL GLACIER

CHITINA GLACIER

WALSH GLACIER

DONJEK GLACIER

STEELE GLACIER

LOGAN GLACIER

COLUMBUS GLACIER SEWARD GLACIER

MALASPINA GLACIER

SEWARD GLACIER

AGASSIZ GLACIER LIBBEY GLACIER

OG LI VIE GLACIER

HUBBARD GLACIER

LOWELL GLACIER

KASKAWULSH

HUBBARD GLACIER

GLACIER

ALVER STONE GLACIER

VALERIE GLACIER

TURNER GLACIER

WEST

NUNATAK GLACIER

Long

Lake Kennicott

River

Hidden

Creek

Lake 

Malaspina

Lake

Oily

Lake

Ross Green 

Lake

Braye

Lakes

Solo

Lake

Rock

Lake

Ptarmigan

Lake

Chitistone

Falls

Clear

Creek

Hanagita

Lakina

Gilahina

Kuskulana

Nizina

McCarthy

Cr

River

River

River

River

Tana River

River

Chitina

River

Klu

River

River

River

River

Gra

Creek

nite

Lakes

White

Skolai

Toby Creek

Chitistone River

Creek

River

Beaver

Creek

White 

Kluane

River

Donjek

Duke River

KLUANE LAKE

River

a

er

ICY BAY

YAKUTAT BAY

RUSSELL FJORD

NUNATAK FJORD

DISENCHAN TMENT BAY

Yahtse River

GULF OF ALASKA

KLUANE

NATIONAL PARK

KLUANE

GAME

SANCTUARY

Chisana

Destruction Bay

Kennicott

McCarthy

Strelna

Chokosna

Dan Creek

May Creek

Burwash Landing

Alaska Highway

Cape Suckling

Cape

Yakataga

Point Manby

Haenke

Island

Atna Peaks

untain

Skolai Pass

Castle

Mountain

Chitistone Peak

CHAIX

HILLS

KARR HILLS

GUYOT HILLS

SAMOVAR HILLS

SUCKLING

HILLS

Juniper

Island

BRITISH COLUMBIA

YUKON TERRITORY

UNITED STATES CANADA

UNITED STATES

CANADA

ALASKA

YUKON TERRITORY

CANADA

UNITED STATES

N TERRITORY

ALASKA

G R A N I T E R A N G E

MACCOLL RIDGE

UNIVERSITY RANGE

R O B I N S O N M O U N T A I N S

WAXELL RIDGE

S L I N G R A N G E

U

N

T

A I N S

N S

W

R

A

N

G E L L M

O

U

N

T

A I N

S

S

A I N

T

E

L I A

S

M

O

U

N

T A I N

S

I C E F I E L D R A N G E S

0

0 10 20 MILES

10 20 KILOMETERS

KotsinaKuskulana

district

district

Chisana

district

McCarthyNizina

district

Bremner

district

Bering River

coal field

Gold and Copper—Or Was It Copper and Gold? 87
xceptionally large copper nugget 

 Creek, however, was salvaged for 

hen Anchorage, and finally Fairbanks, 

s place in the Natural History Museum 

given its higher unit value, was another matter. In 1913, Chisana was the scene of an old-style gold rush, a strike of 200 ounces of placer gold dug in 2 days by two men being rich enough to lure even miners from the Klondike, as well as from Puget Sound in the “Lower 48.” Gold camps in the Nizina district on the south side of the Wrangell Mountains nearly emptied of miners immediately and even the operation of the Kennecott mines was impacted significantly. Several thousand stampeders reached Chisana during 1913, and between 500 and 600 residents stayed through the winter in anticipation of the 1914 mining season. Between 1913 and 1917, about $530,000 in gold (at $20.67/oz) was produced from drainages east of Chisana, principally Bonanza Creek (fig. 47), but a steady 

decline already had set in. Due to the persistence of a few miners, the camp has continued to produce some gold each year until the present time.

Persistence also paid off at Nabesna. High on the slopes of White 

Mountain, prospectors located pockets of coarse-grained sulfide minerals with associated gold where Triassic limestone had been intruded by a Cretaceous pluton. By the late 1920’s, enough lode gold ore had been located in contactmetamorphic (skarn) deposits on the property that a mill was installed to treat the refractory ore. Between 1931 and 1940, gold ore valued at more than $1.8 million was shipped to smelters outside Alaska. However, the valuable pockets of ore were virtually exhausted by then, no new pockets were discovered, and the mine closed permanently in 1947.

Gold and Copper—Or Was It Copper and Gold? 89
xceptionally large copper nugget 

Creek, however, was salvaged for 

hen Anchorage, and finally Fairbanks, 

 place in the Natural History Museum 

of an old-style gold rush, a strike of 200 ounces of placer gold dug in 2 days by two men being rich enough to lure even miners from the Klondike, as well as from Puget Sound in the “Lower 48.” Gold camps in the Nizina district on the south side of the Wrangell Mountains nearly emptied of miners immediately and even the operation of the Kennecott mines was impacted significantly. Several thousand stampeders reached Chisana during 1913, and between 500 and 600 residents stayed through the winter in anticipation of the 1914 mining season. Between 1913 and 1917, about $530,000 in gold (at $20.67/oz) was produced from drainages east of Chisana, principally Bonanza Creek (fig. 47), but a steady 

decline already had set in. Due to the persistence of a few miners, the camp has continued to produce some gold each year until the present time.

Persistence also paid off at Nabesna. High on the slopes of White 

Mountain, prospectors located pockets of coarse-grained sulfide minerals with associated gold where Triassic limestone had been intruded by a Cretaceous pluton. By the late 1920’s, enough lode gold ore had been located in contactmetamorphic (skarn) deposits on the property that a mill was installed to treat the refractory ore. Between 1931 and 1940, gold ore valued at more than $1.8 million was shipped to smelters outside Alaska. However, the valuable pockets of ore were virtually exhausted by then, no new pockets were discovered, and the mine closed permanently in 1947.

Gold and Copper—Or Was It Copper and Gold? 89
Gold and Copper—Or Was It Copper and Gold? 91
Gold and Copper—Or Was It Copper and Gold? 91
Gold and Copper—Or Was It Copper and Gold? 93
Gold and Copper—Or Was It Copper and Gold? 93
Nabesna gold mine (fig. 49)

ever 

Wrangell Mountains, the area remained a 

until the late 1970’s. Much of this activ

ven by the search for porphyry copper

e concentrations of the minerals pyrite 

ybdenite (MoS2) disseminated through 

 deposits also contain gold and silver 

r-molybdenum deposit was discovered 

terminus of the Nabesna Glacier; by 

els and drilling. The deposit occurs 

eous granitic pluton—the Nabesna 

 and Permian Tetelna Volcanics, Permian 

olai Greenstone and younger Triassic 

 have been oxidized, forming brightly 

osit implies. Subsequent geologic 

d that similar plutons and host rocks 

0 mi east of the Orange Hill deposit 

lues in the porphyry deposits are 

stly molybdenum, some contain both 

ain mostly copper. By the late 1960’s 

enum deposits had been discovered and 

k (in the Nabesna pluton) and Carl 

in Creek pluton). Together, Orange Hill 

billion t of ore running about 0.2–0.3 

 too low to encourage development. 

y system also underlies Gold Hill; 

productive placer deposits of the 

hyry system or peripheral veins may 

urrounding placers.

visitors should check in prior to driving the road for information on current road conditions, land status, and facilities. The Nabesna Road originally was built in the 1920’s to carry supplies in to the mine and haul gold ore out. At that time, it extended all the way to the Richardson Highway near Gakona, a distance of about 105 mi. The western part of the original road was later incorporated into the Slana-Tok Cutoff portion of the Glenn Highway that was constructed during World War II to provide a direct link to Anchorage from the newly built Alaska Highway. At the present time, the Nabesna Road is maintained for year-round travel as far as Devils Mountain Lodge near mile 43.

The first 25 mi of the Nabesna Road traverses the northeasternmost extension 

of the Copper River Basin separating the Mentasta Mountains to the north from the Wrangell Mountains to the south. Leaving Slana, the road is built mostly on extensive, flat-lying alluvial deposits of the Slana and Copper Rivers until about Rufus Creek (mile 7), where it climbs up on a bench underlain by lake deposits of glacial Lake Atna. In this area, shorelines of the glacial lake record two prominent lake levels at about 2,450 ft elevation and at about 2,300 ft. On the south side of the road just before mile 9 is the turnoff to Batzulnetas; the vestiges of this 19th century Native village are on private property on the north bank of the Copper River about 2 mi from the Nabesna Road. The road continues over relatively flat terrain underlain by various deposits of glacial Lake Boomerang, including lake-modified glacial moraine and related alluvial deposits.

Geological Sketches of a Few Notable Spots 95
Nabesna gold mine (fig. 49)

ever 

Wrangell Mountains, the area remained a 

until the late 1970’s. Much of this activ

ven by the search for porphyry copper

e concentrations of the minerals pyrite 

ybdenite (MoS2) disseminated through 

 deposits also contain gold and silver 

r-molybdenum deposit was discovered 

terminus of the Nabesna Glacier; by 

els and drilling. The deposit occurs 

eous granitic pluton—the Nabesna 

 and Permian Tetelna Volcanics, Permian 

olai Greenstone and younger Triassic 

 have been oxidized, forming brightly 

osit implies. Subsequent geologic 

d that similar plutons and host rocks 

0 mi east of the Orange Hill deposit 

lues in the porphyry deposits are 

stly molybdenum, some contain both 

ain mostly copper. By the late 1960’s 

enum deposits had been discovered and 

k (in the Nabesna pluton) and Carl 

in Creek pluton). Together, Orange Hill 

billion t of ore running about 0.2–0.3 

 too low to encourage development. 

y system also underlies Gold Hill; 

productive placer deposits of the 

hyry system or peripheral veins may 

urrounding placers.

visitors should check in prior to driving the road for information on current road conditions, land status, and facilities. The Nabesna Road originally was built in the 1920’s to carry supplies in to the mine and haul gold ore out. At that time, it extended all the way to the Richardson Highway near Gakona, a distance of about 105 mi. The western part of the original road was later incorporated into the Slana-Tok Cutoff portion of the Glenn Highway that was constructed during World War II to provide a direct link to Anchorage from the newly built Alaska Highway. At the present time, the Nabesna Road is maintained for year-round travel as far as Devils Mountain Lodge near mile 43.

The first 25 mi of the Nabesna Road traverses the northeasternmost extension 

of the Copper River Basin separating the Mentasta Mountains to the north from the Wrangell Mountains to the south. Leaving Slana, the road is built mostly on extensive, flat-lying alluvial deposits of the Slana and Copper Rivers until about Rufus Creek (mile 7), where it climbs up on a bench underlain by lake deposits of glacial Lake Atna. In this area, shorelines of the glacial lake record two prominent lake levels at about 2,450 ft elevation and at about 2,300 ft. On the south side of the road just before mile 9 is the turnoff to Batzulnetas; the vestiges of this 19th century Native village are on private property on the north bank of the Copper River about 2 mi from the Nabesna Road. The road continues over relatively flat terrain underlain by various deposits of glacial Lake Boomerang, including lake-modified glacial moraine and related alluvial deposits.

Geological Sketches of a Few Notable Spots 95
 at the end of the Nabesna road. View is to the northeast from one of the mine adits high above the 

(tailings) from the mill covers the nearly barren area downhill to its left. The Nabesna mine produced 

940 from small, high-grade pockets of polymetallic ore in Triassic carbonate rocks near contacts with 

esna Mine

 short steep hill onto unmodified 

le 18 affords good views of the 

re underlain by ancient lava flows and 

n and Permian Tetelna Volcanics of the 

is west end of the Mentasta Mountains, 

ntrusions and metamorphic rocks that 

c. The small area of conspicuous bright 

s mountainside is an area of pyrite 

 oxidation.

y on hilly morainal deposits, occasion

rom streams flowing off the Mentasta 

 old unmaintained trail leads about 

eek where the only known Alaskan 

he corundum is present as gray crystals 

matite dikes cutting metamorphic rocks 

fans of Trail Creek (mile 29) and Lost Creek (mile 31). (If these streams 

are running high, which they occasionally do in the summer after heavy rains, caution is advised.) The absence of vegetation on the Trail and Lost 

Creek fans affords good views of the Mentasta Mountains to the north; they are underlain by the dark lavas of the Triassic Nikolai Greenstone and capped by contrasting light-colored Triassic limestones (fig. 51). Beyond, the higher peaks expose shale and sandstone of the younger Jurassic and Cretaceous Nutzotin Mountains sequence.

After crossing the fan at Chalk Creek (mile 33), the road begins a slight 

descent into the relatively narrow and fault-controlled Jack Creek valley that separates the Boyden Hills to the north from the Skookum Creek volcanic center of the Wrangell Mountains to the south. The Boyden Hills are composed of ancient lava flows and volcaniclastic rocks of the Pennsylvanian and Permian Tetelna Volcanics that have been intruded by a large Cretaceous granodiorite pluton. Locally, a few lava flows and pyroclastic rocks from the Skookum Creek center overlie the older rocks of the Boyden Hills. East of mile 33, glacial terraces form prominent hillside benches just above brushline on both sides of the road; they are particularly conspicuous in the Boyden Hills on the north side of the valley. The road crosses Jack Creek near mile 36 and continues high on the south side of the valley, crossing a number of steep alluvial fans from streams that drain the rugged Wrangell Lava terrain, before reaching Devils Mountain Lodge near mile 43.

Geological Sketches of a Few Notable Spots 97
 at the end of the Nabesna road. View is to the northeast from one of the mine adits high above the 

(tailings) from the mill covers the nearly barren area downhill to its left. The Nabesna mine produced 

940 from small, high-grade pockets of polymetallic ore in Triassic carbonate rocks near contacts with 

esna Mine

 short steep hill onto unmodified 

le 18 affords good views of the 

re underlain by ancient lava flows and 

n and Permian Tetelna Volcanics of the 

is west end of the Mentasta Mountains, 

ntrusions and metamorphic rocks that 

c. The small area of conspicuous bright 

s mountainside is an area of pyrite 

 oxidation.

y on hilly morainal deposits, occasion

rom streams flowing off the Mentasta 

 old unmaintained trail leads about 

eek where the only known Alaskan 

he corundum is present as gray crystals 

matite dikes cutting metamorphic rocks 

fans of Trail Creek (mile 29) and Lost Creek (mile 31). (If these streams 

are running high, which they occasionally do in the summer after heavy rains, caution is advised.) The absence of vegetation on the Trail and Lost 

Creek fans affords good views of the Mentasta Mountains to the north; they are underlain by the dark lavas of the Triassic Nikolai Greenstone and capped by contrasting light-colored Triassic limestones (fig. 51). Beyond, the higher peaks expose shale and sandstone of the younger Jurassic and Cretaceous Nutzotin Mountains sequence.

After crossing the fan at Chalk Creek (mile 33), the road begins a slight 

descent into the relatively narrow and fault-controlled Jack Creek valley that separates the Boyden Hills to the north from the Skookum Creek volcanic center of the Wrangell Mountains to the south. The Boyden Hills are composed of ancient lava flows and volcaniclastic rocks of the Pennsylvanian and Permian Tetelna Volcanics that have been intruded by a large Cretaceous granodiorite pluton. Locally, a few lava flows and pyroclastic rocks from the Skookum Creek center overlie the older rocks of the Boyden Hills. East of mile 33, glacial terraces form prominent hillside benches just above brushline on both sides of the road; they are particularly conspicuous in the Boyden Hills on the north side of the valley. The road crosses Jack Creek near mile 36 and continues high on the south side of the valley, crossing a number of steep alluvial fans from streams that drain the rugged Wrangell Lava terrain, before reaching Devils Mountain Lodge near mile 43.

Geological Sketches of a Few Notable Spots 97
mage of a northwest part of WrangellÐSaint Elias National Park and Preserve taken February 

ettlements, rivers, creeks, glaciers, and peaks discussed in the text are shown. The Nabesna 

unction with the Glenn Highway to the Nabesna mine, following the valleys of the Copper 

canic centers in the western Wrangell Mountains can be seen in this image. The pronounced 

ong the Denali and Totschunda faults are conspicuous in the upper half of the view. (U.S. 

Geological Sketches of a Few Notable Spots 99

tone Limestone, Nizina Limestone, and McCarthy Formation) along the south side of the Wrangell Mountains. (D.H. Richter)Figure 52 (page 101). Volcanic vent in the 2Ð3 million-year-old Skookum Creek volcanic center near the end of the Nabesna Road; the valley of Jack Creek is in the background. Actual vent is Þ lled with bedded, dacitic pyroclastic debris. Dark-colored rocks on ridge to right of vent are younger andesitic lava ß ows that lap onto the vent. Note person standing on the ridge crest. (D.H. Richter)
mage of a northwest part of WrangellÐSaint Elias National Park and Preserve taken February 

ettlements, rivers, creeks, glaciers, and peaks discussed in the text are shown. The Nabesna 

unction with the Glenn Highway to the Nabesna mine, following the valleys of the Copper 

canic centers in the western Wrangell Mountains can be seen in this image. The pronounced 

ong the Denali and Totschunda faults are conspicuous in the upper half of the view. (U.S. 

Geological Sketches of a Few Notable Spots 99

tone Limestone, Nizina Limestone, and McCarthy Formation) along the south side of the Wrangell Mountains. (D.H. Richter)Figure 52 (page 101). Volcanic vent in the 2Ð3 million-year-old Skookum Creek volcanic center near the end of the Nabesna Road; the valley of Jack Creek is in the background. Actual vent is Þ lled with bedded, dacitic pyroclastic debris. Dark-colored rocks on ridge to right of vent are younger andesitic lava ß ows that lap onto the vent. Note person standing on the ridge crest. (D.H. Richter)
Geological Sketches of a Few Notable Spots 101
Geological Sketches of a Few Notable Spots 101
 thin-bedded Triassic limestone strata in Cooper Pass. Beds have been deformed by movement along the unda Fault System 

ng in creek bed. (D.H. Richter)

Totschunda Creek in the foreground along the topographic depression that marks the course of the 

ta Mountains. Young fault movement is marked by the offset glacial deposits in the low area immediately 

Richter)

flows to form Chitistone Falls. These 

anic island arc between about 310 and 

ower canyon, the overlying Triassic 

itistone and Nizina Limestones, and the 

r level to the top of Chitistone Mountain, 

n above Peavine Bar. The Nikolai 

al volcanic plateau, beginning about 230 

as inundated and covered by marine 

ntertidal mudbanks, but progressively 

t 200 m.y. ago. Immediately west of 

y the Nikolai Greenstone is overturned 

-dipping thrust fault (fig. 21). This 

s produced by the Late Jurassic and 

d all of Wrangellia. Overlying the 

esozoic units of Wrangellia above a 

s sedimentary rocks of the Kennicott and 

These marine conglomeratic sandstones 

Pass and lower Russell Glacier, all outcrops are Wrangell Lava, including the rugged ramparts and pinnacles of aptly named Castle Mountain. For more than 90 mi west of Skolai Pass, from Nizina Glacier (fig. 57) to the Copper 

River Basin, the entire crest of the Wrangell Mountains consists of volcanic or intrusive rocks produced in the vast Neogene volcanic field.

The path over the Goat Trail and Skolai Pass has existed since the gold 

rushes of the late 19th century, forming a rugged segment of one route from Valdez to the White River followed by the ebb-and-flow of argonauts to and from the Klondike or the Fortymile mining districts on the Yukon River. Early in the 20th century, the route also was used by some stampeders to the Chisana gold rush on the north flank of the Wrangell Mountains.

Geological Sketches of a Few Notable Spots 103
 thin-bedded Triassic limestone strata in Cooper Pass. Beds have been deformed by movement along the unda Fault System 

ng in creek bed. (D.H. Richter)

Totschunda Creek in the foreground along the topographic depression that marks the course of the 

ta Mountains. Young fault movement is marked by the offset glacial deposits in the low area immediately 

Richter)

flows to form Chitistone Falls. These 

anic island arc between about 310 and 

ower canyon, the overlying Triassic 

itistone and Nizina Limestones, and the 

r level to the top of Chitistone Mountain, 

n above Peavine Bar. The Nikolai 

al volcanic plateau, beginning about 230 

as inundated and covered by marine 

ntertidal mudbanks, but progressively 

t 200 m.y. ago. Immediately west of 

y the Nikolai Greenstone is overturned 

-dipping thrust fault (fig. 21). This 

s produced by the Late Jurassic and 

d all of Wrangellia. Overlying the 

esozoic units of Wrangellia above a 

s sedimentary rocks of the Kennicott and 

These marine conglomeratic sandstones 

Pass and lower Russell Glacier, all outcrops are Wrangell Lava, including the rugged ramparts and pinnacles of aptly named Castle Mountain. For more than 90 mi west of Skolai Pass, from Nizina Glacier (fig. 57) to the Copper 

River Basin, the entire crest of the Wrangell Mountains consists of volcanic or intrusive rocks produced in the vast Neogene volcanic field.

The path over the Goat Trail and Skolai Pass has existed since the gold 

rushes of the late 19th century, forming a rugged segment of one route from Valdez to the White River followed by the ebb-and-flow of argonauts to and from the Klondike or the Fortymile mining districts on the Yukon River. Early in the 20th century, the route also was used by some stampeders to the Chisana gold rush on the north flank of the Wrangell Mountains.

Geological Sketches of a Few Notable Spots 103
TOTSCHUNDA FAULT

Geological Sketches of a Few Notable Spots 105
TOTSCHUNDA FAULT

Geological Sketches of a Few Notable Spots 105
HASEN CREEK FORMATION

Geological Sketches of a Few Notable Spots 107
HASEN CREEK FORMATION

Geological Sketches of a Few Notable Spots 107
Chimney Mountain

ROHN GLACIER

ER

NIZINA GLACIER

Geological Sketches of a Few Notable Spots 109
Chimney Mountain

ROHN GLACIER

ER

NIZINA GLACIER

Geological Sketches of a Few Notable Spots 109
Geological Sketches of a Few Notable Spots 111
Geological Sketches of a Few Notable Spots 111
t. Drum

), westernmost volcano in the Wrangell volcanic fi eld, is a stratovolcano built in at least two eruptive 

ars ago. Seen here from the southeast, its composite internal structure, consisting of lava fl ows and 

Snider Peak, the conspicuous gray craggy summit on the left, apparently was the last dome to be 

h the cataclysmic eruptions that destroyed much of the south face of Mt. Drum, producing pyroclastic 

aslina volcanic debris and mud fl ow that is exposed along the Copper River from the Chetaslina River 

ese eruptions. This series of events was much like the catastrophic eruptions of Mt. St. Helens in 1980, 

e of volcanic material. The hillside in the foreground consists of undated andesitic fl ows that emanated 

hese fl ows, which fi ll paleovalleys on the fl anks of the volcano, probably were erupted prior to 600,000 

gell began to form. (G.R. Winkler)

iderably dissected, consists of a thick 

ruded between 3 and 4 m.y. ago by large 

bvolcanic magma chambers.

Russell, Klutlan, and Hawkins Glaciers, are Mt. Bona (16,421 ft), Mt. Churchill (15,638 ft), and University Peak (14, 470 ft). They cannot be seen from any park roads. Other than the caldera on Mt. Churchill, which erupted the young White River Ash, the Bona-Churchill massif is apparently constructed of older andesitic lava flows of unknown age. University Peak is eroded mainly from a subvolcanic granodioritic intrusion that is about 8.4 million years old. The Miocene intrusion is so homogeneous and so little jointed that it has weathered into nearly sheer faces on all sides. Finally climbed in 1955, it was the last major peak within the parklands to be summitted.

Geological Sketches of a Few Notable Spots 113
t. Drum

), westernmost volcano in the Wrangell volcanic fi eld, is a stratovolcano built in at least two eruptive 

ars ago. Seen here from the southeast, its composite internal structure, consisting of lava fl ows and 

Snider Peak, the conspicuous gray craggy summit on the left, apparently was the last dome to be 

h the cataclysmic eruptions that destroyed much of the south face of Mt. Drum, producing pyroclastic 

aslina volcanic debris and mud fl ow that is exposed along the Copper River from the Chetaslina River 

ese eruptions. This series of events was much like the catastrophic eruptions of Mt. St. Helens in 1980, 

e of volcanic material. The hillside in the foreground consists of undated andesitic fl ows that emanated 

hese fl ows, which fi ll paleovalleys on the fl anks of the volcano, probably were erupted prior to 600,000 

gell began to form. (G.R. Winkler)

iderably dissected, consists of a thick 

ruded between 3 and 4 m.y. ago by large 

bvolcanic magma chambers.

Russell, Klutlan, and Hawkins Glaciers, are Mt. Bona (16,421 ft), Mt. Churchill (15,638 ft), and University Peak (14, 470 ft). They cannot be seen from any park roads. Other than the caldera on Mt. Churchill, which erupted the young White River Ash, the Bona-Churchill massif is apparently constructed of older andesitic lava flows of unknown age. University Peak is eroded mainly from a subvolcanic granodioritic intrusion that is about 8.4 million years old. The Miocene intrusion is so homogeneous and so little jointed that it has weathered into nearly sheer faces on all sides. Finally climbed in 1955, it was the last major peak within the parklands to be summitted.

Geological Sketches of a Few Notable Spots 113
Dacite

pluton

Conglomerate

Older andesite flows

Geological Sketches of a Few Notable Spots 115
Dacite

pluton

Conglomerate

Older andesite flows

Geological Sketches of a Few Notable Spots 115
lana Glacier 

up moraine-covered terminus of the Kuskulana Glacier toward Mt. Black

gell Mountains. The broad, domal summit of Mt. Blackburn is eroded from 

.4 million years old that intrudes a thick sequence of andesitic lava fl ows. 

ountain, the ledges of which are defi ned by snow, can be seen to dip 

g collapse of a fi lled caldera into the subsiding roof of the granitic magma 

(without snow cover) that lie between the forks of the Kuskulana Glacier are 

ng basaltic fl ows of the Triassic Nikolai Greenstone. Near the right edge of 

y scattered outcrops of Triassic marine carbonate rocks, the lighter colored 

Carthy Formation. (G.R. Winkler)

Geological Sketches of a Few Notable Spots 117
lana Glacier 

up moraine-covered terminus of the Kuskulana Glacier toward Mt. Black

gell Mountains. The broad, domal summit of Mt. Blackburn is eroded from 

.4 million years old that intrudes a thick sequence of andesitic lava fl ows. 

ountain, the ledges of which are defi ned by snow, can be seen to dip 

g collapse of a fi lled caldera into the subsiding roof of the granitic magma 

(without snow cover) that lie between the forks of the Kuskulana Glacier are 

ng basaltic fl ows of the Triassic Nikolai Greenstone. Near the right edge of 

y scattered outcrops of Triassic marine carbonate rocks, the lighter colored 

Carthy Formation. (G.R. Winkler)

Geological Sketches of a Few Notable Spots 117
Geological Sketches of a Few Notable Spots 119
Geological Sketches of a Few Notable Spots 119
ower Klawasi mud volcano in the Copper River Basin about 11 mi east of Glennallen. The summit pond, 

h warm saline mud that is agitated continually by exsolving carbon dioxide. (D.H. Richter)

 field is linked to subduction of the Pacific 

g Yakutat terrane. The volcanism began 

bout 26 m.y. ago. For the first 10–12 

as oblique, and volcanic activity may 

w large centers. The 20-million-year-old 

 White River, however, contains the 

lcanic field, and the volume of material 

 5 m.y. ago, the rate of plate convergence 

ecame less oblique. This change coin

duction in the west end of the Wrangell 

andesitic shield volcanoes were con

go. Although some underthrusting 

h of the stress imposed by northward 

lieved by movement along the strike-slip 

t systems, effectively stopping the gen

further suggests that movement on 

ay have been initiated 100,000–200,000 

magma production ceased. Reasons for 

ay be a consequence of the progressive 

he stress of the Pacific plate convergence 

ubduction.

in the last 5 million years or so, the already incised river still maintained its course—until a complicated Quaternary history of damming by glaciers in its middle and lower canyons interrupted its flow episodically, impounding Lake Atna in the Copper River Basin. The presence of the glacial lake is indicated not only by the accumulated lacustrine sediments, now exposed in many places in river bluffs within the Copper River Basin, but also by the ancient shorelines formed at several levels around the margins of the basin. The shorelines indicate positions at which the lake was stable for extended periods.

The bedrock and unconsolidated fill of the Copper River Basin is permanently frozen in most places, a condition called permafrost, or permanently 

frozen ground. It may extend to depths of 165–245 ft in the central Copper River Basin. Seasonal thawing of the upper 1–2 ft of the unconsolidated fill creates widespread quagmires, bogs, ponds, and landslides, because the water remains near the surface above the permanently frozen materials beneath. Permafrost presents obstacles to standard engineering procedures: once thawing is initiated, it is difficult to arrest or reverse, and differing properties of the diverse unconsolidated materials lead to unpredictable foundation conditions (fig. 65). Most engineering solutions attempt to shield or insulate the ground from thawing or to artificially freeze or refreeze it. In areas of permafrost, the Alaska pipeline has been elevated on insulated piers, not buried, as is the normal pipeline construction practice. Modern buildings and highways have been placed on thick gravel pads. Where engineering solutions were inadequate, however, differential settlement, sloughing, or catastrophic slope failures have resulted. A drive on the highways of the Copper River Basin may be the best indicator of the difficulties posed by differential melting of ice-rich permafrost: bulges, depressions, and cracks require perpetual repair of damage induced by disruption of the permafrost conditions beneath.

Geological Sketches of a Few Notable Spots 121
ower Klawasi mud volcano in the Copper River Basin about 11 mi east of Glennallen. The summit pond, 

h warm saline mud that is agitated continually by exsolving carbon dioxide. (D.H. Richter)

 field is linked to subduction of the Pacific 

g Yakutat terrane. The volcanism began 

bout 26 m.y. ago. For the first 10–12 

as oblique, and volcanic activity may 

w large centers. The 20-million-year-old 

 White River, however, contains the 

lcanic field, and the volume of material 

 5 m.y. ago, the rate of plate convergence 

ecame less oblique. This change coin

duction in the west end of the Wrangell 

andesitic shield volcanoes were con

go. Although some underthrusting 

h of the stress imposed by northward 

lieved by movement along the strike-slip 

t systems, effectively stopping the gen

further suggests that movement on 

ay have been initiated 100,000–200,000 

magma production ceased. Reasons for 

ay be a consequence of the progressive 

he stress of the Pacific plate convergence 

ubduction.

in the last 5 million years or so, the already incised river still maintained its course—until a complicated Quaternary history of damming by glaciers in its middle and lower canyons interrupted its flow episodically, impounding Lake Atna in the Copper River Basin. The presence of the glacial lake is indicated not only by the accumulated lacustrine sediments, now exposed in many places in river bluffs within the Copper River Basin, but also by the ancient shorelines formed at several levels around the margins of the basin. The shorelines indicate positions at which the lake was stable for extended periods.

The bedrock and unconsolidated fill of the Copper River Basin is permanently frozen in most places, a condition called permafrost, or permanently 

frozen ground. It may extend to depths of 165–245 ft in the central Copper River Basin. Seasonal thawing of the upper 1–2 ft of the unconsolidated fill creates widespread quagmires, bogs, ponds, and landslides, because the water remains near the surface above the permanently frozen materials beneath. Permafrost presents obstacles to standard engineering procedures: once thawing is initiated, it is difficult to arrest or reverse, and differing properties of the diverse unconsolidated materials lead to unpredictable foundation conditions (fig. 65). Most engineering solutions attempt to shield or insulate the ground from thawing or to artificially freeze or refreeze it. In areas of permafrost, the Alaska pipeline has been elevated on insulated piers, not buried, as is the normal pipeline construction practice. Modern buildings and highways have been placed on thick gravel pads. Where engineering solutions were inadequate, however, differential settlement, sloughing, or catastrophic slope failures have resulted. A drive on the highways of the Copper River Basin may be the best indicator of the difficulties posed by differential melting of ice-rich permafrost: bulges, depressions, and cracks require perpetual repair of damage induced by disruption of the permafrost conditions beneath.

Geological Sketches of a Few Notable Spots 121
123

Geological Sketches of a Few Notable Spots 123
123

Geological Sketches of a Few Notable Spots 123
BREMNER RIVER

COPPER RIVER

Heney

Glacier

CRNWR

Geological Sketches of a Few Notable Spots 125
BREMNER RIVER

COPPER RIVER

Heney

Glacier

CRNWR

Geological Sketches of a Few Notable Spots 125
 earthquake. It slid about one

third of 

coming to rest. The outermost part of 

hanneled by the river and the landslide 

getated also. However, it will remain 

nd landslides may recur because large 

way zone of the slide; adjacent bedrock is 

ailures. 

opes of the Crystalline Hills north 

t-bounded mass of metamorphosed 

e somber dark gabbro and orthogneiss 

stalline Hills. Where the road crosses 

outcrop of the gabbro is present on the 

e Permian limestone is well exposed 

site. At mile 50, the broad opening of 

ellent view to the north of Mt. Blackburn 

cuously layered andesitic flows of the 

k. 

shallow

seated intrusive phases of the Wrangell Lava. Much larger related 

plutons underlie Porphyry Mountain and Sourdough Peak east of McCarthy and much of Mt. Blackburn, where they range in age from at least 8.6 to 3.4 million years old; some bodies may be even younger, inasmuch as they intrude as high as the upper part of the Wrangell Lava on Mt. Blackburn. A small outcrop of Chititu Formation occurs along the McCarthy Road where it dips into Swift Creek at approximately mile 58.5.

At mile 62, the road ends on the west bank of the Kennicott River, which 

tumbles through bouldery outwash of the Kennicott Glacier, the source of the river a short distance to the north. Footbridges cross two channels of the Kennicott River at the east end of the road, providing access to McCarthy about 0.5 mi east of the footbridges, and Kennicott, which is located about 5 mi north of McCarthy. Camping, parking, meals, guided river trips, shuttle service, and lodging are available in the McCarthy or Kennicott areas. Air charters are available from McCarthy; reservations are recommended.

Geological Sketches of a Few Notable Spots 127
 earthquake. It slid about one

third of 

coming to rest. The outermost part of 

hanneled by the river and the landslide 

getated also. However, it will remain 

nd landslides may recur because large 

way zone of the slide; adjacent bedrock is 

ailures. 

opes of the Crystalline Hills north 

t-bounded mass of metamorphosed 

e somber dark gabbro and orthogneiss 

stalline Hills. Where the road crosses 

outcrop of the gabbro is present on the 

e Permian limestone is well exposed 

site. At mile 50, the broad opening of 

ellent view to the north of Mt. Blackburn 

cuously layered andesitic flows of the 

k. 

shallow

seated intrusive phases of the Wrangell Lava. Much larger related 

plutons underlie Porphyry Mountain and Sourdough Peak east of McCarthy and much of Mt. Blackburn, where they range in age from at least 8.6 to 3.4 million years old; some bodies may be even younger, inasmuch as they intrude as high as the upper part of the Wrangell Lava on Mt. Blackburn. A small outcrop of Chititu Formation occurs along the McCarthy Road where it dips into Swift Creek at approximately mile 58.5.

At mile 62, the road ends on the west bank of the Kennicott River, which 

tumbles through bouldery outwash of the Kennicott Glacier, the source of the river a short distance to the north. Footbridges cross two channels of the Kennicott River at the east end of the road, providing access to McCarthy about 0.5 mi east of the footbridges, and Kennicott, which is located about 5 mi north of McCarthy. Camping, parking, meals, guided river trips, shuttle service, and lodging are available in the McCarthy or Kennicott areas. Air charters are available from McCarthy; reservations are recommended.

Geological Sketches of a Few Notable Spots 127
129

Geological Sketches of a Few Notable Spots 129

Figure 68 (page 130). Bluffs along the Tazlina River just upstream from the Richardson Highway north of Copper Center expose about 200 ft of mainly alluvial and lacustrine deposits of Quaternary age. The alluvial deposits, consisting of well-sorted gravel interlayered with minor sand beds, are the darker colored beds above river level and in the middle of the section. Each section of gravel and sand represents a time when no lake was present in this part of the basin. The gravel along the river in the foreground is a present-day equivalent of those deposits. The lower alluvial beds in the section include the thin distal edge of the Sanford volcanic debris fl ow (v), the lighter colored lens less than 3 ft thick near the base of the bluff in the center. The debris fl ow, containing numerous clasts of andesite, originated from a collapsed dome on the eastern fl ank of Mt. Drum and invaded a river valley that was much like the present one, but which existed about 200,000 to 300,000 years ago. Overlying each major alluvial unit are conspicuous lighter colored beds of fi ne sand, silt, and clay which indicate that a lake fi rst encroached upon and then completely inundated the area. The younger of these lakes was glacial Lake Atna. Coarser grained lake deposits, including diamicton perhaps deposited when a glacier invaded this part of the lake, occupy most of the upper part of the section. (H.R. Schmoll)Figure 69 (page 131). The Chitina River Valley from the northern slopes of the Chugach Mountains. The McCarthy Road follows the lowlands directly behind Billy Lake just to the right of center. (Dashed line indicates approximate alignment of the road.) The lake-filled depressions, bedrock knobs, and complexly intertonguing lenticular surficial deposits of the valley floor (exposed locally in the Chitina River bluffs) indicate the former presence of glaciers that fi lled the entire valley. In the background, ice- and snow-clad Mt. Blackburn (16,390 ft), the highest peak in the western Wrangell Mountains, is a broad volcanic dome and caldera constructed of lava flows intruded by subvolcanic plutons between about 4.2 and 3.4 m.y. ago. The moraine-covered terminus of the Kuskulana Glacier can be seen at the foot of Mt. Blackburn. The peak rises above rugged ridges eroded from Paleozoic and Mesozoic units of the Wrangellia terrane. The sharp ridges in the foreground are eroded into metamorphosed Paleozoic rocks of the southern margin of the Wrangellia terrane as well as Jurassic plutons of the Chitina magmatic arc. (G.R. Winkler) 
129

Geological Sketches of a Few Notable Spots 129

Figure 68 (page 130). Bluffs along the Tazlina River just upstream from the Richardson Highway north of Copper Center expose about 200 ft of mainly alluvial and lacustrine deposits of Quaternary age. The alluvial deposits, consisting of well-sorted gravel interlayered with minor sand beds, are the darker colored beds above river level and in the middle of the section. Each section of gravel and sand represents a time when no lake was present in this part of the basin. The gravel along the river in the foreground is a present-day equivalent of those deposits. The lower alluvial beds in the section include the thin distal edge of the Sanford volcanic debris fl ow (v), the lighter colored lens less than 3 ft thick near the base of the bluff in the center. The debris fl ow, containing numerous clasts of andesite, originated from a collapsed dome on the eastern fl ank of Mt. Drum and invaded a river valley that was much like the present one, but which existed about 200,000 to 300,000 years ago. Overlying each major alluvial unit are conspicuous lighter colored beds of fi ne sand, silt, and clay which indicate that a lake fi rst encroached upon and then completely inundated the area. The younger of these lakes was glacial Lake Atna. Coarser grained lake deposits, including diamicton perhaps deposited when a glacier invaded this part of the lake, occupy most of the upper part of the section. (H.R. Schmoll)Figure 69 (page 131). The Chitina River Valley from the northern slopes of the Chugach Mountains. The McCarthy Road follows the lowlands directly behind Billy Lake just to the right of center. (Dashed line indicates approximate alignment of the road.) The lake-filled depressions, bedrock knobs, and complexly intertonguing lenticular surficial deposits of the valley floor (exposed locally in the Chitina River bluffs) indicate the former presence of glaciers that fi lled the entire valley. In the background, ice- and snow-clad Mt. Blackburn (16,390 ft), the highest peak in the western Wrangell Mountains, is a broad volcanic dome and caldera constructed of lava flows intruded by subvolcanic plutons between about 4.2 and 3.4 m.y. ago. The moraine-covered terminus of the Kuskulana Glacier can be seen at the foot of Mt. Blackburn. The peak rises above rugged ridges eroded from Paleozoic and Mesozoic units of the Wrangellia terrane. The sharp ridges in the foreground are eroded into metamorphosed Paleozoic rocks of the southern margin of the Wrangellia terrane as well as Jurassic plutons of the Chitina magmatic arc. (G.R. Winkler) 
a Glacier

Billy Lake

Geological Sketches of a Few Notable Spots 131
a Glacier

Billy Lake

Geological Sketches of a Few Notable Spots 131
Chitistone Limestone

Nikolai Greenstone

Kennicott

B

RG

J

133

Geological Sketches of a Few Notable Spots 133
Chitistone Limestone

Nikolai Greenstone

Kennicott

B

RG

J

133

Geological Sketches of a Few Notable Spots 133
Blackburn

ce budget. In August 1974, an unusually 

le bridge across the western channel 

o McCarthy in the summer months to 

bulent river. Replacement bridges, for 

both channels in 1996. The increasing 

 channel poses a potential hazard to 

hannel migration and discharge volumes 

surface moraine, and the ice is almost totally exposed. Each also has a steep, crevassed icefall; on Root Glacier, Stairway Icefall forms a striking scene from near Kennicott—particularly on a sunny day when the remarkably blue tint of the depths of its crevasses contrasts with the more normal white of the surrounding glacier.

Donoho Peak and the ridge extending to the north separate Gates and Root 

Glaciers. The north-dipping section exposes most of the definitive Triassic and Jurassic units of the Wrangellia terrane, overlain unconformably at the north end of the ridge by the Miocene Frederika Formation and the Miocene to Holocene Wrangell Lava. Donoho Peak is underlain by a conspicuous overturned syncline, which is cored by the Nizina Limestone, and forms a gray-colored zigzag on the east face of the peak (fig. 71). 

The Kennicott Glacier was named in 1899 by Oscar Rohn, USGS, for 

Robert Kennicott, a pioneer Alaskan explorer and director of the Western Union Telegraph Expedition to the Bering Straits region in 1865. The Kennecott Copper Corporation, formed in 1915, took its name from the glacier, but inexplicably replaced the “i” with an “e.”

390 ft) looking west from Bonanza Ridge in the early autumn. Kennicott Glacier (at the base of Mt. 

stance) are separated by Donoho Peak. Beyond Kennicott Glacier near the left edge of the view is a 

d of Hidden Creek valley is ice free but is dammed by Kennicott Glacier to form Hidden Creek Lake. 

ennicott Glacier, usually between late July and early September, sometimes forming damaging outburst 

uth shoulder of Donoho Peak is the darker weathering Triassic Nikolai Greenstone, which is overlain 

stones. An overturned syncline on the north fl ank of Donoho Peak forms a conspicuous zigzag in 

sic and Cretaceous mountain-building that affected much of coastal Alaska from the present Wrangell 

st copper lodes of the type found at the Kennecott mines occur in the lower part of the Chitistone, which 

ts extent in the Wrangell Mountains. This view is taken from above the angle station in the foreground 

he ridge above changed directions around a massive fl ywheel for the rest of its 16,000-ft journey down 

G.R. Winkler)

Geological Sketches of a Few Notable Spots 135
Blackburn

ce budget. In August 1974, an unusually 

le bridge across the western channel 

o McCarthy in the summer months to 

bulent river. Replacement bridges, for 

both channels in 1996. The increasing 

 channel poses a potential hazard to 

hannel migration and discharge volumes 

surface moraine, and the ice is almost totally exposed. Each also has a steep, crevassed icefall; on Root Glacier, Stairway Icefall forms a striking scene from near Kennicott—particularly on a sunny day when the remarkably blue tint of the depths of its crevasses contrasts with the more normal white of the surrounding glacier.

Donoho Peak and the ridge extending to the north separate Gates and Root 

Glaciers. The north-dipping section exposes most of the definitive Triassic and Jurassic units of the Wrangellia terrane, overlain unconformably at the north end of the ridge by the Miocene Frederika Formation and the Miocene to Holocene Wrangell Lava. Donoho Peak is underlain by a conspicuous overturned syncline, which is cored by the Nizina Limestone, and forms a gray-colored zigzag on the east face of the peak (fig. 71). 

The Kennicott Glacier was named in 1899 by Oscar Rohn, USGS, for 

Robert Kennicott, a pioneer Alaskan explorer and director of the Western Union Telegraph Expedition to the Bering Straits region in 1865. The Kennecott Copper Corporation, formed in 1915, took its name from the glacier, but inexplicably replaced the “i” with an “e.”

390 ft) looking west from Bonanza Ridge in the early autumn. Kennicott Glacier (at the base of Mt. 

stance) are separated by Donoho Peak. Beyond Kennicott Glacier near the left edge of the view is a 

d of Hidden Creek valley is ice free but is dammed by Kennicott Glacier to form Hidden Creek Lake. 

ennicott Glacier, usually between late July and early September, sometimes forming damaging outburst 

uth shoulder of Donoho Peak is the darker weathering Triassic Nikolai Greenstone, which is overlain 

stones. An overturned syncline on the north fl ank of Donoho Peak forms a conspicuous zigzag in 

sic and Cretaceous mountain-building that affected much of coastal Alaska from the present Wrangell 

st copper lodes of the type found at the Kennecott mines occur in the lower part of the Chitistone, which 

ts extent in the Wrangell Mountains. This view is taken from above the angle station in the foreground 

he ridge above changed directions around a massive fl ywheel for the rest of its 16,000-ft journey down 

G.R. Winkler)

Geological Sketches of a Few Notable Spots 135
To the

Chitina River

Wrangellia

terrane

Chugach terrane

Falls Creek

137

Geological Sketches of a Few Notable Spots 137
To the

Chitina River

Wrangellia

terrane

Chugach terrane

Falls Creek

137

Geological Sketches of a Few Notable Spots 137
Geological Sketches of a Few Notable Spots 139
Geological Sketches of a Few Notable Spots 139
eland area seaward of the glacier.

xpeditions to Mt. St. Elias in the late 

s of approach. Photographs taken during 

features, features that have stimulated 

ury and designation of Malaspina Glacier 

y because of the unusual patterns of its 

ory of the Malaspina area includes a 

 retreats (fig. 43). There has been little 

ulb of the Malaspina Glacier for more 

 has grown on moraine that covers the 

n A.D. 600 and 900 of Yahtse, Guyot, and 

a northwestern lobe that merged with the 

70 and 1290 of Hubbard Glacier formed 

ged with the Seward lobe. During these 

 presented a continuous tidal front from 

tructed on the terminal moraine from 

Yakutat area are about 600 years old, 

alaspina Glacier had begun to recede 

cy Bay and Yakutat Bay may have 

esent positions by about A.D. 1700, as 

by, and near Guyot, Lucia, and Hidden 

ves that a large bay formerly extended 

ginate from the deep recession in Icy 

tributary glaciers, as well as most glaciers in the Yakutat Bay area, show periodic short surges and retreats.

Surge cycles in such tributaries as Seward and Marvine Glaciers are 

responsible for the striking zigzag patterns exhibited by folded moraines on the Malaspina Glacier in such places as south of the Hitchcock Hills. Periods of instability in the tributary glaciers are marked by large-scale, but short-lived forward movement. Curiously, immediately adjacent glaciers can behave very differently: one glacier may surge forward while its neighbor is stable or even slowly retreats. Where such glaciers join, they can be strongly deformed below their point of merger, which is reflected in very complex patterns in the moraines on their surfaces.

oking south, taken in 1980 from above the terminus of the Yahtse Glacier. Karr Hills are on the left edge 

right. The iceberg-choked inner bay indicates active calving of the tidewater glaciers surrounding 

 of Alaska are in the distance, separated from Icy Bay by the fl at Malaspina foreland on the left. The 

rom the right end of the foreland—just barely visible behind the ridge on the skyline (in the upper 

. McPherson. Kichyatt Point, at the east end of the ridge, separates the inner and outer parts of 

the Yakataga Formation, fossiliferous glacial-marine siltstone, sandstone, and diamictite, that was 

d and tectonically active coastline during the last 6 million years. (George Plafker)

Geological Sketches of a Few Notable Spots 141
eland area seaward of the glacier.

xpeditions to Mt. St. Elias in the late 

s of approach. Photographs taken during 

features, features that have stimulated 

ury and designation of Malaspina Glacier 

y because of the unusual patterns of its 

ory of the Malaspina area includes a 

 retreats (fig. 43). There has been little 

ulb of the Malaspina Glacier for more 

 has grown on moraine that covers the 

n A.D. 600 and 900 of Yahtse, Guyot, and 

a northwestern lobe that merged with the 

70 and 1290 of Hubbard Glacier formed 

ged with the Seward lobe. During these 

 presented a continuous tidal front from 

tructed on the terminal moraine from 

Yakutat area are about 600 years old, 

alaspina Glacier had begun to recede 

cy Bay and Yakutat Bay may have 

esent positions by about A.D. 1700, as 

by, and near Guyot, Lucia, and Hidden 

ves that a large bay formerly extended 

ginate from the deep recession in Icy 

tributary glaciers, as well as most glaciers in the Yakutat Bay area, show periodic short surges and retreats.

Surge cycles in such tributaries as Seward and Marvine Glaciers are 

responsible for the striking zigzag patterns exhibited by folded moraines on the Malaspina Glacier in such places as south of the Hitchcock Hills. Periods of instability in the tributary glaciers are marked by large-scale, but short-lived forward movement. Curiously, immediately adjacent glaciers can behave very differently: one glacier may surge forward while its neighbor is stable or even slowly retreats. Where such glaciers join, they can be strongly deformed below their point of merger, which is reflected in very complex patterns in the moraines on their surfaces.

oking south, taken in 1980 from above the terminus of the Yahtse Glacier. Karr Hills are on the left edge 

right. The iceberg-choked inner bay indicates active calving of the tidewater glaciers surrounding 

 of Alaska are in the distance, separated from Icy Bay by the fl at Malaspina foreland on the left. The 

rom the right end of the foreland—just barely visible behind the ridge on the skyline (in the upper 

. McPherson. Kichyatt Point, at the east end of the ridge, separates the inner and outer parts of 

the Yakataga Formation, fossiliferous glacial-marine siltstone, sandstone, and diamictite, that was 

d and tectonically active coastline during the last 6 million years. (George Plafker)

Geological Sketches of a Few Notable Spots 141
Geological Sketches of a Few Notable Spots 143

acier area taken February 17, 1979; north is at the top of the image and the Gulf of Alaska at the 

y is conspicuous near the left edge of the photograph. It has formed by glacial recession since 

ciers combine to form the enormous bulb of the Malaspina Glacier; the two major tributaries 

m the Samovar Hills. The east edge of the Malaspina Glacier (on the right of this view) is 

ed from the Hitchcock Hills area. The pattern of the deformed moraines indicates uneven 

aciers along their merger zone. Forelands formed by unconsolidated sediment are expanding 

r. The western foreland now covers the area of a former coastal indentation called “Icy Bay” 

S. Geological Survey Landsat 2 image)
Geological Sketches of a Few Notable Spots 143

acier area taken February 17, 1979; north is at the top of the image and the Gulf of Alaska at the 

y is conspicuous near the left edge of the photograph. It has formed by glacial recession since 

ciers combine to form the enormous bulb of the Malaspina Glacier; the two major tributaries 

m the Samovar Hills. The east edge of the Malaspina Glacier (on the right of this view) is 

ed from the Hitchcock Hills area. The pattern of the deformed moraines indicates uneven 

aciers along their merger zone. Forelands formed by unconsolidated sediment are expanding 

r. The western foreland now covers the area of a former coastal indentation called “Icy Bay” 

S. Geological Survey Landsat 2 image)
VALERIE GLACIER

HUBBARD GLACIER

ND DAB PASSAGE

Osier Island RUSSELL FIORD

Gilbert Point

145

Geological Sketches of a Few Notable Spots 145
VALERIE GLACIER

HUBBARD GLACIER

ND DAB PASSAGE

Osier Island RUSSELL FIORD

Gilbert Point

145

Geological Sketches of a Few Notable Spots 145
chantment Bay

they have been heavily overgrown with 

cut bench at Bancas Point, encrusted 

ell above the reach of tides, provided a 

rately measure, the uplift and changes in 

e maximum uplift of 46 ft near Bancas 

writing in North America, exceeding even 

ue Island in Prince William Sound by 

is not known for certain which fault or 

e Esker Creek fault near Bancas Point and 

t. Numerous fissures also were formed 

airweather fault in Nunatak Fiord, 30 

ing some aftershock activity along the 

were particularly favorable. These eyewitness accounts clearly indicate that the impact of a series of major temblors of the type associated typically with a plate boundary seismic event can be widespread.

ast across Bancas Point on the north side of Disenchantment Bay near Yakutat, showing a wave-cut 

utat earthquakes. The current wave-cut bedrock cliff is subject to the wash of storm waves and 

a bench, the pre-earthquake beach, and a higher wave-cut bedrock cliff, which have been partially 

akes. This former shoreline was uplifted abruptly during the earthquakes, the maximum uplift recorded 

Plafker)

Geological Sketches of a Few Notable Spots 147
chantment Bay

they have been heavily overgrown with 

cut bench at Bancas Point, encrusted 

ell above the reach of tides, provided a 

rately measure, the uplift and changes in 

e maximum uplift of 46 ft near Bancas 

writing in North America, exceeding even 

ue Island in Prince William Sound by 

is not known for certain which fault or 

e Esker Creek fault near Bancas Point and 

t. Numerous fissures also were formed 

airweather fault in Nunatak Fiord, 30 

ing some aftershock activity along the 

were particularly favorable. These eyewitness accounts clearly indicate that the impact of a series of major temblors of the type associated typically with a plate boundary seismic event can be widespread.

ast across Bancas Point on the north side of Disenchantment Bay near Yakutat, showing a wave-cut 

utat earthquakes. The current wave-cut bedrock cliff is subject to the wash of storm waves and 

a bench, the pre-earthquake beach, and a higher wave-cut bedrock cliff, which have been partially 

akes. This former shoreline was uplifted abruptly during the earthquakes, the maximum uplift recorded 

Plafker)

Geological Sketches of a Few Notable Spots 147
l studies and wholehearted support of, 

trial, and governmental colleagues, the 

unt, breadth, and quality of earth

ion. Pursuing detailed studies in the 

setting and genetic controls for the 

ett established a framework for the 

uided an entire generation of follow-up 

aphic studies throughout the Gulf of 

ker has led multifaceted investigations 

ng of the dynamics of continuing conti

work provided the detailed substance 

 of accretionary tectonics have come to 

ogic mapping in the Nabesna area, Don 

rk for the northern Wrangell Mountains 

 corroborating studies throughout the 

logy soon led him and numerous col

in the Wrangell volcanic field that have 

raphy, eruptive history, and geologic 

field.

Ed MacKevett, August 1967, above the Chitistone River canyon.

George Plafker, July 1985, Chugach Mountains.Don Richter, August 1982, near the headwaters of the Copper River.

Acknowledgments 149

Wrangell–Saint Elias region showing localities 

ws indicate direction of view. (Modifi ed from 
l studies and wholehearted support of, 

trial, and governmental colleagues, the 

unt, breadth, and quality of earth

ion. Pursuing detailed studies in the 

setting and genetic controls for the 

ett established a framework for the 

uided an entire generation of follow-up 

aphic studies throughout the Gulf of 

ker has led multifaceted investigations 

ng of the dynamics of continuing conti

work provided the detailed substance 

 of accretionary tectonics have come to 

ogic mapping in the Nabesna area, Don 

rk for the northern Wrangell Mountains 

 corroborating studies throughout the 

logy soon led him and numerous col

in the Wrangell volcanic field that have 

raphy, eruptive history, and geologic 

field.

Ed MacKevett, August 1967, above the Chitistone River canyon.

George Plafker, July 1985, Chugach Mountains.Don Richter, August 1982, near the headwaters of the Copper River.

Acknowledgments 149

Wrangell–Saint Elias region showing localities 

ws indicate direction of view. (Modifi ed from 
e beneath trenches of the circum

Pacific 

cluster. According to the theory of 

ding, subducting lithospheric plates sink 

hquakes along their upper boundaries, 

ments broken from material of biologic 

 may consist largely of broken pieces 

hic rock that has a blue color owing 

 minerals; indicates relatively high pres

ditions of formation.

hat is bilaterally symmetrical. Age range, 

ly found as fossils in Paleozoic rocks. 

nsisting of angular fragments held 

 form by sedimentary, igneous, or 

her than bends. Ant: ductile.

as an external skeleton. Age range, 

ally found as fossils in Paleozoic rocks.

nic depression, whose diameter is many 

d vent; generally formed by collapse 

formed principally by organic or inor

gnesium, or iron carbonate minerals—for 

by severe mechanical deformation—

or fragment of a sediment or rock, 

g.

ntary rock in which grains of clay size 

ate.

Continental plate. A rigid segment of the Earth

s lithosphere made up of 

relatively less dense materials ( 2.7 g/cm3), called continental crust, that are 

typical of continental interiors; separated from adjacent lithospheric plates by zones of seismic activity. Ant: oceanic plate, oceanic crust. 

Continental shelf. That part of the continental margin that is between the 

shoreline and the continental slope—typically nearly flat and at depths 

between 0 and 200 m.

Continental slope. That part of the continental margin that slopes between 3° 

and 6° into the deeper parts of the ocean.

Convergence. The relative motion between two plates that are moving toward 

each other; convergence generally is taken up in subduction zones by displacement directly across the zone (along dip-slip faults, which slip down the 

dip), but may have components parallel to the zone (along strike-slip faults, which slip horizontally) or obliquely to it (along oblique-slip faults).

Coquina. A limestone composed predominantly of mechanically worked fossil 

debris.

Coral. Bottom-dwelling sessile marine invertebrate organism (polyp) that may 

be colonial or solitary. Age range, Ordovician-present.

Craton. A part of the Earth’s continental crust that has attained stability and has 

been little deformed for a prolonged time.

Crinoid. A type of echinoderm with a disk-shaped or globular body and 

branched appendages. Age range, Ordovician-present; stems or segments of stems (columnals) are more likely to be preserved as fossils, and are especially common in Paleozoic rocks.

Crust. The outermost layer of the Earth, that part above the mantle; it represents 

less than 0.1 percent of the Earth’s volume, and consists of continental crust and oceanic crust.

Dacite. A fine-grained volcanic rock that has an intermediate percentage of 

silica, the extrusive equivalent of granodiorite.

Detritus. Fragmental material, such as gravel, sand, silt, or clay, that is derived 

from older rocks and moved away from its place of origin. 

Glossary of Geologic Terms 151
e beneath trenches of the circum

Pacific 

cluster. According to the theory of 

ding, subducting lithospheric plates sink 

hquakes along their upper boundaries, 

ments broken from material of biologic 

 may consist largely of broken pieces 

hic rock that has a blue color owing 

 minerals; indicates relatively high pres

ditions of formation.

hat is bilaterally symmetrical. Age range, 

ly found as fossils in Paleozoic rocks. 

nsisting of angular fragments held 

 form by sedimentary, igneous, or 

her than bends. Ant: ductile.

as an external skeleton. Age range, 

ally found as fossils in Paleozoic rocks.

nic depression, whose diameter is many 

d vent; generally formed by collapse 

formed principally by organic or inor

gnesium, or iron carbonate minerals—for 

by severe mechanical deformation—

or fragment of a sediment or rock, 

g.

ntary rock in which grains of clay size 

ate.

Continental plate. A rigid segment of the Earth

s lithosphere made up of 

relatively less dense materials ( 2.7 g/cm3), called continental crust, that are 

typical of continental interiors; separated from adjacent lithospheric plates by zones of seismic activity. Ant: oceanic plate, oceanic crust. 

Continental shelf. That part of the continental margin that is between the 

shoreline and the continental slope—typically nearly flat and at depths 

between 0 and 200 m.

Continental slope. That part of the continental margin that slopes between 3° 

and 6° into the deeper parts of the ocean.

Convergence. The relative motion between two plates that are moving toward 

each other; convergence generally is taken up in subduction zones by displacement directly across the zone (along dip-slip faults, which slip down the 

dip), but may have components parallel to the zone (along strike-slip faults, which slip horizontally) or obliquely to it (along oblique-slip faults).

Coquina. A limestone composed predominantly of mechanically worked fossil 

debris.

Coral. Bottom-dwelling sessile marine invertebrate organism (polyp) that may 

be colonial or solitary. Age range, Ordovician-present.

Craton. A part of the Earth’s continental crust that has attained stability and has 

been little deformed for a prolonged time.

Crinoid. A type of echinoderm with a disk-shaped or globular body and 

branched appendages. Age range, Ordovician-present; stems or segments of stems (columnals) are more likely to be preserved as fossils, and are especially common in Paleozoic rocks.

Crust. The outermost layer of the Earth, that part above the mantle; it represents 

less than 0.1 percent of the Earth’s volume, and consists of continental crust and oceanic crust.

Dacite. A fine-grained volcanic rock that has an intermediate percentage of 

silica, the extrusive equivalent of granodiorite.

Detritus. Fragmental material, such as gravel, sand, silt, or clay, that is derived 

from older rocks and moved away from its place of origin. 

Glossary of Geologic Terms 151
perature or pressure conditions.

bearing intrusive igneous rock that 

gma at depth in the Earth’s crust; its 

uivalent to rhyolite, a volcanic rock.

rocks that consist of coarse-grained 

equal size; typical of granites.

ck that contains less alkali feldspar than 

me chemical composition as rhyodacite, 

on of rounded rock fragments consisting 

han sand (diameter greater than 2 mm); 

onglomerate.

ontaining poorly sorted and poorly 

rained matrix; generally reflects an 

nsportation, deposition, and burial were 

 mountain belt. 

morphic rock, consisting of well-aligned 

is due to the presence of the minerals 

e; believed to form at temperatures in 

ined altered or metamorphosed mafi c 

composition exhibiting a dark-greenish 

ed or semiconsolidated smooth rock 

depressions produced by the drag of 

 it; the surfaces beneath glaciers often 

 grooved by boulders entrained in the 

arser crystals in a porphyritic igneous

lline or glassy material.

Intrusive rocks. Igneous rocks emplaced in preexisting rocks beneath the 

Earth’s surface. Ant: extrusive rocks.

Island arc. A chain of islands, generally arcuate in map view, that are formed 

by magmatic processes above a zone of subduction. Island arcs generally are underlain by extrusive volcanic rocks, which are intruded by intrusiverocks formed from the same magma. Thus, approximate synonyms are magmatic arc and volcanic arc. The Aleutian island arc consists of a chain of volcanic islands rising above a subduction zone, the Aleutian (Trench) megathrust.

Isotope. One of two or more species of the same chemical element, having the 

same atomic number but a different atomic weight. Radiometric measurements of geologic time are obtained by comparing abundances of parent and daughter isotopes produced in geologic materials by radioactive decay having known decay rates.

Kame. A low hummock or irregular ridge deposited at the margin of a melting 

glacier as a delta or fan and composed of stratified sand and gravel.

Kettle. A bowl-shaped depression, commonly without surface drainage and 

occupied by a lake or swamp, that formed by the melting of a block of stagnant ice (left behind by a retreating glacier) that had been enclosed within glacial detritus.

Lacustrine. Pertaining to, or formed in, a lake; in particular, glacial-lacustrine

sediments often are finely banded, or varved, where bands are formed by coarser sediment accumulated annually during the ice-free season topped with thinner, finer (and often organic) sediment deposited during the winter.

Lentil. A minor stratigraphic unit of limited geographic extent that is a subdivision of a rock formation; it forms a lens that terminates on all sides within 

a formation. 

Lignite. A brownish-black coal that is intermediate in coalification between peat 

and subbituminous coal.

Limestone. A carbonate sedimentary rock, consisting predominantly of calcite 

(CaCO3).

Glossary of Geologic Terms 153
perature or pressure conditions.

bearing intrusive igneous rock that 

gma at depth in the Earth’s crust; its 

uivalent to rhyolite, a volcanic rock.

rocks that consist of coarse-grained 

equal size; typical of granites.

ck that contains less alkali feldspar than 

me chemical composition as rhyodacite, 

on of rounded rock fragments consisting 

han sand (diameter greater than 2 mm); 

onglomerate.

ontaining poorly sorted and poorly 

rained matrix; generally reflects an 

nsportation, deposition, and burial were 

 mountain belt. 

morphic rock, consisting of well-aligned 

is due to the presence of the minerals 

e; believed to form at temperatures in 

ined altered or metamorphosed mafi c 

composition exhibiting a dark-greenish 

ed or semiconsolidated smooth rock 

depressions produced by the drag of 

 it; the surfaces beneath glaciers often 

 grooved by boulders entrained in the 

arser crystals in a porphyritic igneous

lline or glassy material.

Intrusive rocks. Igneous rocks emplaced in preexisting rocks beneath the 

Earth’s surface. Ant: extrusive rocks.

Island arc. A chain of islands, generally arcuate in map view, that are formed 

by magmatic processes above a zone of subduction. Island arcs generally are underlain by extrusive volcanic rocks, which are intruded by intrusiverocks formed from the same magma. Thus, approximate synonyms are magmatic arc and volcanic arc. The Aleutian island arc consists of a chain of volcanic islands rising above a subduction zone, the Aleutian (Trench) megathrust.

Isotope. One of two or more species of the same chemical element, having the 

same atomic number but a different atomic weight. Radiometric measurements of geologic time are obtained by comparing abundances of parent and daughter isotopes produced in geologic materials by radioactive decay having known decay rates.

Kame. A low hummock or irregular ridge deposited at the margin of a melting 

glacier as a delta or fan and composed of stratified sand and gravel.

Kettle. A bowl-shaped depression, commonly without surface drainage and 

occupied by a lake or swamp, that formed by the melting of a block of stagnant ice (left behind by a retreating glacier) that had been enclosed within glacial detritus.

Lacustrine. Pertaining to, or formed in, a lake; in particular, glacial-lacustrine

sediments often are finely banded, or varved, where bands are formed by coarser sediment accumulated annually during the ice-free season topped with thinner, finer (and often organic) sediment deposited during the winter.

Lentil. A minor stratigraphic unit of limited geographic extent that is a subdivision of a rock formation; it forms a lens that terminates on all sides within 

a formation. 

Lignite. A brownish-black coal that is intermediate in coalification between peat 

and subbituminous coal.

Limestone. A carbonate sedimentary rock, consisting predominantly of calcite 

(CaCO3).

Glossary of Geologic Terms 153
 bands form during the winter when 

ny places, both types of ogives occur 

tures within mountainous areas are 

in the shallower levels of the crust and 

dies in the deeper crustal levels. 

morphism of an intrusive igneous rock.

nd or gravel) washed out from a glacier 

d in front of or beyond the margin of 

remanent magnetism in rocks in order 

nsity of the Earth’s magnetic field in 

geologic times, based on fossil plants 

c age is a relative age determined by 

ly is expressed by reference to a named 

 based on world-wide correlation of 

marsh or swamp; many paludal sedi

aring land previously on the public 

overnment to any citizen of the United 

ral resources exist on or beneath the 

 made on the land, and an official survey 

5/acre for lode claims and $2.50/acre for 

ssued, the claimant may make any use 

ined igneous rock, usually occurring as 

plutons.

 a clam, having a bilaterally symmetrical 

an to present.

Phyllite. A metamorphosed shale rock, in which minute crystals of micaceous 

minerals impart a silky sheen to the rock’s surfaces.

Piedmont glacier. A thick, continuous sheet of ice at the base of a mountain 

range, formed by the spreading out and coalescing of valley glaciers from higher elevations of the mountains.

Pillow basalt. A basaltic lava, displaying pillow structure—that is, discontinuous pillow-shaped masses formed by underwater extrusion. Generally, the 

pillows fit closely, such that the concavities of one match the convexities of another.

Placer. A surficial mineral deposit formed by mechanical concentration of 

mineral particles in unconsolidated materials. Ant: lode.

Plate tectonics. A theory of global scale, in which the lithosphere is divided 

into a number of rigid plates that interact with one another at their boundaries, causing earthquakes and deformation.

Plinian. An explosive volcanic eruption that produces large and persistent 

eruption clouds consisting of fragmental volcanic rock and gases; large volumes of tephra are characteristic.

Pluton. An igneous intrusion, implying no connotation as to shape, size, or 

depth of emplacement.

Porphyry. (1) An igneous rock of any composition that contains conspicuous 

large crystals (or phenocrysts) in a fine-grained groundmass; such a texture 

is said to be porphyritic. (2) Certain types of porphyritic igneous rocks contain disseminated deposits of gold, copper, or molybdenum and thus are called (for example) porphyry copper deposits.

Proglacial. Immediately in front of, or just beyond, the outer limits of a glacier 

or ice sheet and generally in direct contact with the ice.

Protolith. The unmetamorphosed rock from which a given metamorphic rock

was formed by metamorphism.

Provenance. A place of origin—in particular, the area from which the constituent minerals of a sedimentary rock are derived, as well as the rock types 

of which the area is composed.

Glossary of Geologic Terms 155
 bands form during the winter when 

ny places, both types of ogives occur 

tures within mountainous areas are 

in the shallower levels of the crust and 

dies in the deeper crustal levels. 

morphism of an intrusive igneous rock.

nd or gravel) washed out from a glacier 

d in front of or beyond the margin of 

remanent magnetism in rocks in order 

nsity of the Earth’s magnetic field in 

geologic times, based on fossil plants 

c age is a relative age determined by 

ly is expressed by reference to a named 

 based on world-wide correlation of 

marsh or swamp; many paludal sedi

aring land previously on the public 

overnment to any citizen of the United 

ral resources exist on or beneath the 

 made on the land, and an official survey 

5/acre for lode claims and $2.50/acre for 

ssued, the claimant may make any use 

ined igneous rock, usually occurring as 

plutons.

 a clam, having a bilaterally symmetrical 

an to present.

Phyllite. A metamorphosed shale rock, in which minute crystals of micaceous 

minerals impart a silky sheen to the rock’s surfaces.

Piedmont glacier. A thick, continuous sheet of ice at the base of a mountain 

range, formed by the spreading out and coalescing of valley glaciers from higher elevations of the mountains.

Pillow basalt. A basaltic lava, displaying pillow structure—that is, discontinuous pillow-shaped masses formed by underwater extrusion. Generally, the 

pillows fit closely, such that the concavities of one match the convexities of another.

Placer. A surficial mineral deposit formed by mechanical concentration of 

mineral particles in unconsolidated materials. Ant: lode.

Plate tectonics. A theory of global scale, in which the lithosphere is divided 

into a number of rigid plates that interact with one another at their boundaries, causing earthquakes and deformation.

Plinian. An explosive volcanic eruption that produces large and persistent 

eruption clouds consisting of fragmental volcanic rock and gases; large volumes of tephra are characteristic.

Pluton. An igneous intrusion, implying no connotation as to shape, size, or 

depth of emplacement.

Porphyry. (1) An igneous rock of any composition that contains conspicuous 

large crystals (or phenocrysts) in a fine-grained groundmass; such a texture 

is said to be porphyritic. (2) Certain types of porphyritic igneous rocks contain disseminated deposits of gold, copper, or molybdenum and thus are called (for example) porphyry copper deposits.

Proglacial. Immediately in front of, or just beyond, the outer limits of a glacier 

or ice sheet and generally in direct contact with the ice.

Protolith. The unmetamorphosed rock from which a given metamorphic rock

was formed by metamorphism.

Provenance. A place of origin—in particular, the area from which the constituent minerals of a sedimentary rock are derived, as well as the rock types 

of which the area is composed.

Glossary of Geologic Terms 155
e marked by topographic trenches on 

zones generally dip downward in the 

are paralleled, in the down-dip direc

uring subduction by the melting of the 

in the subduction zone.

ally flows very rapidly. During a surge, 

wn-glacier at velocities of as much 

surface of the glacier may become 

be sustained for more than brief periods 

 are separated by much longer periods 

wage.

contains mostly alkali feldspar.

ward, the core of which contains the 

er rocks. Ant: anticline.

me as, or forming as a result of, orogenic 

orces involved in creating the structures 

uter part of the Earth, including their 

ion.

tic materials of a volcano, categorized, 

largest), as ash, lapilli, blocks, and 

of regional extent, characterized by a 

 of contiguous terranes.

continent.

e crustal unit over another, as in thrust 

 that originally were deposited directly 

come the sedimentary rock called tillite.

sisting principally of quartz and plagio

e-slip fault.

Ultramafic rocks. A general name for very dark igneous rocks that consist 

mostly of minerals rich in iron and magnesium.

Unconformity. A break in the geologic record where a rock unit is overlain by 

another that is not next in the direct stratigraphic succession—the contact between the two units is said to be unconformable. A considerable interruption in deposition may be present at unconformities, often representing uplift and erosion indicated by loss of previously formed sequences. Thus, many—but not all—unconformities are marked by an absence of parallelism between strata below and above the unconformable contact.

Underplating. Said of a process that incrementally emplaces tabular faultbounded masses of rocks beneath like masses formed earlier, resulting in 

fault-bounded stacks (plates) of rock that enlarge from their underside. Underplating is a common process on the inner sides of many subduction 

zones, where materials derived from the converging tectonic plates are structurally stacked against and beneath the lip of the upper or overriding plate. 

Underthrust. A type of thrust fault in which the lower rock mass has been 

actively moved under the upper, passive rock mass.

Varve. A sedimentary bed or sequence of layers deposited in 1 year’s time—

usually in still water adjacent to glaciers. A glacial varve normally includes a thicker summer layer consisting of coarser, lighter colored sediment produced during the season of rapid melting, and a thinner winter layer consisting of finer, often organic and darker colored sediment slowly deposited from suspension in quiet, icebound water.

Vent. The opening at the Earth’s surface through which volcanic materials are 

emitted.

Volcanic rocks. Finely crystalline or glassy igneous rocks resulting from volcanic action near the Earth’s surface, either ejected explosively or extruded 

as lava. Ant: plutonic rocks.

Volcaniclastic rocks. Pertaining to clastic rocks that contain volcanic material.Window. An eroded area of a thrust sheet that displays the rocks underlying 

the thrust sheet.

Glossary of Geologic Terms 157
e marked by topographic trenches on 

zones generally dip downward in the 

are paralleled, in the down-dip direc

uring subduction by the melting of the 

in the subduction zone.

ally flows very rapidly. During a surge, 

wn-glacier at velocities of as much 

surface of the glacier may become 

be sustained for more than brief periods 

 are separated by much longer periods 

wage.

contains mostly alkali feldspar.

ward, the core of which contains the 

er rocks. Ant: anticline.

me as, or forming as a result of, orogenic 

orces involved in creating the structures 

uter part of the Earth, including their 

ion.

tic materials of a volcano, categorized, 

largest), as ash, lapilli, blocks, and 

of regional extent, characterized by a 

 of contiguous terranes.

continent.

e crustal unit over another, as in thrust 

 that originally were deposited directly 

come the sedimentary rock called tillite.

sisting principally of quartz and plagio

e-slip fault.

Ultramafic rocks. A general name for very dark igneous rocks that consist 

mostly of minerals rich in iron and magnesium.

Unconformity. A break in the geologic record where a rock unit is overlain by 

another that is not next in the direct stratigraphic succession—the contact between the two units is said to be unconformable. A considerable interruption in deposition may be present at unconformities, often representing uplift and erosion indicated by loss of previously formed sequences. Thus, many—but not all—unconformities are marked by an absence of parallelism between strata below and above the unconformable contact.

Underplating. Said of a process that incrementally emplaces tabular faultbounded masses of rocks beneath like masses formed earlier, resulting in 

fault-bounded stacks (plates) of rock that enlarge from their underside. Underplating is a common process on the inner sides of many subduction 

zones, where materials derived from the converging tectonic plates are structurally stacked against and beneath the lip of the upper or overriding plate. 

Underthrust. A type of thrust fault in which the lower rock mass has been 

actively moved under the upper, passive rock mass.

Varve. A sedimentary bed or sequence of layers deposited in 1 year’s time—

usually in still water adjacent to glaciers. A glacial varve normally includes a thicker summer layer consisting of coarser, lighter colored sediment produced during the season of rapid melting, and a thinner winter layer consisting of finer, often organic and darker colored sediment slowly deposited from suspension in quiet, icebound water.

Vent. The opening at the Earth’s surface through which volcanic materials are 

emitted.

Volcanic rocks. Finely crystalline or glassy igneous rocks resulting from volcanic action near the Earth’s surface, either ejected explosively or extruded 

as lava. Ant: plutonic rocks.

Volcaniclastic rocks. Pertaining to clastic rocks that contain volcanic material.Window. An eroded area of a thrust sheet that displays the rocks underlying 

the thrust sheet.

Glossary of Geologic Terms 157
0 p.

ns, Danny, and Ballestrazze, Vanessa, 

 studies of selected mineral deposits in 

k and Peserve, Alaska: U.S. Geological 

1 p.

Anchorage, Alaska, Alaska Northwest 

y—The town that copper built: Juneau, 

posits and occurrences in the McCarthy 

cal Survey Miscellaneous Field Studies 

250,000.

R.P., II, and Silberman, M.L., 1997, 

angell Mountains, Alaska—High-grade 

e contact, in Goldfarb, R.J., and Miller, 

ska: Economic Geology Monograph 

 copper—The epic triumph of Erastus 

Y., D’Aloquin Publishing Co., 195 p.

.P., 1975, Mineral resources map of the 

 Geological Survey Miscellaneous Field 

50,000.

pilers, 1988, Cordova to Kennecott, 

nal Park Service, and Cordova, Alaska, 

rish prince of the iron trails—Builder 

Copper River Northwestern Railways: 

ed, 62 p.

e story of Stephen Birch: Anchorage, 

cal Survey of Canada Maps 115B and 115C (E 1/2), Open File 830, 2 sheets, scale 1:125,000.

MacKevett, E.M., Jr., 1978, Geologic map of the McCarthy quadrangle, Alaska: 

U.S. Geological Survey Miscellaneous Investigations Series Map I-1032, scale 1:250,000.

Miller, D.J., 1971, Geologic map of the Yakataga district, Gulf of Alaska Tertiary 

province: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-610, scale 1:125,000.

Moffit F.H., 1938, Geology of the Chitina Valley and adjacent area, Alaska: U.S. 

Geological Survey Bulletin 894, 137 p.

Moffit, F.H., and Mertie, J.B., Jr., 1923, The Kotsina-Kuskulana district, Alaska: 

U.S. Geological Survey Bulletin 745, 149 p.

Muller, J.E., 1967, Kluane Lake area, Yukon Territory: Geological Survey of 

Canada Memoir 340, 137 p.

Nichols, D.R., and Yehle, L.A., 1969, Engineering geologic map of the southeastern Copper River Basin, Alaska: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map I-524, scale 1:125,000.

Plafker, George, and Miller, D.J., 1957a, Reconnaissance geology of the Malaspina district, Alaska: U.S. Geological Survey Oil and Gas Investigations 

Map OM-189, scale 1:125,000.

Sources and Suggested Additional Reading 159
0 p.

ns, Danny, and Ballestrazze, Vanessa, 

 studies of selected mineral deposits in 

k and Peserve, Alaska: U.S. Geological 

1 p.

Anchorage, Alaska, Alaska Northwest 

y—The town that copper built: Juneau, 

posits and occurrences in the McCarthy 

cal Survey Miscellaneous Field Studies 

250,000.

R.P., II, and Silberman, M.L., 1997, 

angell Mountains, Alaska—High-grade 

e contact, in Goldfarb, R.J., and Miller, 

ska: Economic Geology Monograph 

 copper—The epic triumph of Erastus 

Y., D’Aloquin Publishing Co., 195 p.

.P., 1975, Mineral resources map of the 

 Geological Survey Miscellaneous Field 

50,000.

pilers, 1988, Cordova to Kennecott, 

nal Park Service, and Cordova, Alaska, 

rish prince of the iron trails—Builder 

Copper River Northwestern Railways: 

ed, 62 p.

e story of Stephen Birch: Anchorage, 

cal Survey of Canada Maps 115B and 115C (E 1/2), Open File 830, 2 sheets, scale 1:125,000.

MacKevett, E.M., Jr., 1978, Geologic map of the McCarthy quadrangle, Alaska: 

U.S. Geological Survey Miscellaneous Investigations Series Map I-1032, scale 1:250,000.

Miller, D.J., 1971, Geologic map of the Yakataga district, Gulf of Alaska Tertiary 

province: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-610, scale 1:125,000.

Moffit F.H., 1938, Geology of the Chitina Valley and adjacent area, Alaska: U.S. 

Geological Survey Bulletin 894, 137 p.

Moffit, F.H., and Mertie, J.B., Jr., 1923, The Kotsina-Kuskulana district, Alaska: 

U.S. Geological Survey Bulletin 745, 149 p.

Muller, J.E., 1967, Kluane Lake area, Yukon Territory: Geological Survey of 

Canada Memoir 340, 137 p.

Nichols, D.R., and Yehle, L.A., 1969, Engineering geologic map of the southeastern Copper River Basin, Alaska: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map I-524, scale 1:125,000.

Plafker, George, and Miller, D.J., 1957a, Reconnaissance geology of the Malaspina district, Alaska: U.S. Geological Survey Oil and Gas Investigations 

Map OM-189, scale 1:125,000.

Sources and Suggested Additional Reading 159
GQ

1418, scale 1:63,360.

eologic map and sections of the northern 

gle, Alaska: U.S. Geological Survey 

ions Map I-410, scale 1:63,360.

 and Menzies, Martin, 2000, Geologic 

gle, Alaska: U.S. Geological Survey 

ions Map I-2695, scale 1:63,360.

, 1981, Geologic map of the McCarthy 

logical Survey Geologic Quadrangle 

and Schmoll, H.R., 1982, Geologic map 

aska: U.S. Geological Survey Geologic 

:63,360.

eologic map and section of the Nabesna 

logical Survey Miscellaneous Geologic 

63,360.

 map and section of the Nabesna B-4 

cal Survey Miscellaneous Geologic 

63,360.

map of the Nabesna A-4 quadrangle, 

Miscellaneous Geologic Investigations 

map of the Nabesna B-3 quadrangle, 

Miscellaneous Investigations Map I-904, 

Geologic map of the Nabesna A

6 quadrangle, Alaska: U.S. Geological 

Survey Open-File Report 97-475, scale 1:63,360.

Richter, D.H., and Schmoll, H.R., 1973, Geologic map of the Nabesna C-5 

quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1062, scale 1:63,360.

Richter, D.H., and Smith, R.L., 1976, Geologic map of the Nabesna A-5 

quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1292, scale 1:63,360.

Richter, D.H., Smith, J.G., Schmoll, H.R., and Smith, R.L., 1992, Geologic map 

of the Nabesna B-6 quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1688, scale 1:63,360.

Valdez quadrangleYehle, L.A., 1980, Preliminary surficial geologic map of the Valdez C-1 quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Investigations 

Map MF-1132, scale 1:63,360.

———1981, Preliminary surficial geologic map of the Valdez B-1 quadrangle, 

Alaska: U.S. Geological Survey Miscellaneous Field Investigations Map MF-1364, scale 1:63,360.

Sources and Suggested Additional Reading 161
GQ

1418, scale 1:63,360.

eologic map and sections of the northern 

gle, Alaska: U.S. Geological Survey 

ions Map I-410, scale 1:63,360.

 and Menzies, Martin, 2000, Geologic 

gle, Alaska: U.S. Geological Survey 

ions Map I-2695, scale 1:63,360.

, 1981, Geologic map of the McCarthy 

logical Survey Geologic Quadrangle 

and Schmoll, H.R., 1982, Geologic map 

aska: U.S. Geological Survey Geologic 

:63,360.

eologic map and section of the Nabesna 

logical Survey Miscellaneous Geologic 

63,360.

 map and section of the Nabesna B-4 

cal Survey Miscellaneous Geologic 

63,360.

map of the Nabesna A-4 quadrangle, 

Miscellaneous Geologic Investigations 

map of the Nabesna B-3 quadrangle, 

Miscellaneous Investigations Map I-904, 

Geologic map of the Nabesna A

6 quadrangle, Alaska: U.S. Geological 

Survey Open-File Report 97-475, scale 1:63,360.

Richter, D.H., and Schmoll, H.R., 1973, Geologic map of the Nabesna C-5 

quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1062, scale 1:63,360.

Richter, D.H., and Smith, R.L., 1976, Geologic map of the Nabesna A-5 

quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1292, scale 1:63,360.

Richter, D.H., Smith, J.G., Schmoll, H.R., and Smith, R.L., 1992, Geologic map 

of the Nabesna B-6 quadrangle, Alaska: U.S. Geological Survey Geologic Quadrangle Map GQ-1688, scale 1:63,360.

Valdez quadrangleYehle, L.A., 1980, Preliminary surficial geologic map of the Valdez C-1 quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Investigations 

Map MF-1132, scale 1:63,360.

———1981, Preliminary surficial geologic map of the Valdez B-1 quadrangle, 

Alaska: U.S. Geological Survey Miscellaneous Field Investigations Map MF-1364, scale 1:63,360.

Sources and Suggested Additional Reading 161
er, G.R., 1994, Geology of the southern 

fker, George, and Berg, H.C., eds., The 

, The Geological Society of America, 

G-1, p. 389-449.

ull, J.S., 1989, Bedrock geology and 

a, Peninsular, and Chugach terranes 

nsect in the Chugach Mountains and 

ka: Journal of Geophysical Research, v. 

A., and DePaolo, D.J., 1991, A mantle 

mation of Wrangellia and other oceanic 

54, p. 263–267.

U.S. Geological Survey Professional Paper 543

I, 74 p.

Plafker, George, Gilpin, L.M., and Lahr, J.C., 1994, Neotectonic map of Alaska 

(Plate 12), in Plafker, George, and Berg, H.C., eds., The geology of Alaska: Boulder, Colo., The Geological Society of America, The geology of North America, v. G-1, scale 1:2,500,000.

Plafker, George, Hudson, Travis, and Richter, D.H., 1977, Preliminary observations of late Cenzoic displacements along the Totschunda and Denali fault 

systems, in Blean, K.M., ed., The United States Geological Survey in Alaska—Accomplishments during 1976: U.S. Geological Survey Circular 751-B, p. B67–B69.

Plafker, George, Hudson, Travis, Rubin, Meyer, and Dixon, K.L., 1982, Holocene marine terraces and uplift history in the Yakataga seismic gap near Icy 

Cape, Alaska, in Coonrad, W.L., ed., The United States Geological Survey in Alaska—Accomplishments during 1980: U.S. Geological Survey Circular 844, p. 111–115.

Richter, D.H., and Matson, N.A., Jr., 1971, Quaternary faulting in the 

eastern Alaska Range: Geological Society of America Bulletin, v. 82, p. 1529-1540.

Tarr, R.S., and Martin, Lawrence, 1912, The earthquakes at Yakutat Bay, Alaska, 

in September 1899: U.S. Geological Survey Professional Paper 69, 135 p.

Sources and Suggested Additional Reading 163
er, G.R., 1994, Geology of the southern 

fker, George, and Berg, H.C., eds., The 

, The Geological Society of America, 

G-1, p. 389-449.

ull, J.S., 1989, Bedrock geology and 

a, Peninsular, and Chugach terranes 

nsect in the Chugach Mountains and 

ka: Journal of Geophysical Research, v. 

A., and DePaolo, D.J., 1991, A mantle 

mation of Wrangellia and other oceanic 

54, p. 263–267.

U.S. Geological Survey Professional Paper 543

I, 74 p.

Plafker, George, Gilpin, L.M., and Lahr, J.C., 1994, Neotectonic map of Alaska 

(Plate 12), in Plafker, George, and Berg, H.C., eds., The geology of Alaska: Boulder, Colo., The Geological Society of America, The geology of North America, v. G-1, scale 1:2,500,000.

Plafker, George, Hudson, Travis, and Richter, D.H., 1977, Preliminary observations of late Cenzoic displacements along the Totschunda and Denali fault 

systems, in Blean, K.M., ed., The United States Geological Survey in Alaska—Accomplishments during 1976: U.S. Geological Survey Circular 751-B, p. B67–B69.

Plafker, George, Hudson, Travis, Rubin, Meyer, and Dixon, K.L., 1982, Holocene marine terraces and uplift history in the Yakataga seismic gap near Icy 

Cape, Alaska, in Coonrad, W.L., ed., The United States Geological Survey in Alaska—Accomplishments during 1980: U.S. Geological Survey Circular 844, p. 111–115.

Richter, D.H., and Matson, N.A., Jr., 1971, Quaternary faulting in the 

eastern Alaska Range: Geological Society of America Bulletin, v. 82, p. 1529-1540.

Tarr, R.S., and Martin, Lawrence, 1912, The earthquakes at Yakutat Bay, Alaska, 

in September 1899: U.S. Geological Survey Professional Paper 69, 135 p.

Sources and Suggested Additional Reading 163
U.S. Geological Survey Miscellaneous 

, scale 1:125,000.

1, Glacier ice: Seattle, Wash., University 

Alaskan glacier studies: Washington, 

, 498 p.

, Austin, 1991, A preliminary forecast of 

d its influence on Russell Fiord, Alaska: 

ources Investigations Report 90-4172, 

 Map of western Copper River Basin, 

d shorelines, glacial moraines, and loca

adiocarbon-dated samples: U.S. Geo

6-390, 30 p., scale 1:250,000.

Report 96

4296, 90 p.

Yehle, L.A., and Rosenkrans, Danny, 1994, The 1993 Nelson Mountain landslide, Chitina Valley, southern Alaska, an aerial view, in Till, A.B., and 

Moore, T.E., eds., Geologic studies in Alaska by the U.S. Geological Survey, 1993: U.S. Geological Survey Bulletin 2107, p. 39–41.

Sources and Suggested Additional Reading 165
U.S. Geological Survey Miscellaneous 

, scale 1:125,000.

1, Glacier ice: Seattle, Wash., University 

Alaskan glacier studies: Washington, 

, 498 p.

, Austin, 1991, A preliminary forecast of 

d its influence on Russell Fiord, Alaska: 

ources Investigations Report 90-4172, 

 Map of western Copper River Basin, 

d shorelines, glacial moraines, and loca

adiocarbon-dated samples: U.S. Geo

6-390, 30 p., scale 1:250,000.

Report 96

4296, 90 p.

Yehle, L.A., and Rosenkrans, Danny, 1994, The 1993 Nelson Mountain landslide, Chitina Valley, southern Alaska, an aerial view, in Till, A.B., and 

Moore, T.E., eds., Geologic studies in Alaska by the U.S. Geological Survey, 1993: U.S. Geological Survey Bulletin 2107, p. 39–41.

Sources and Suggested Additional Reading 165
National Parkand Preserve, Alaska
National Parkand Preserve, Alaska