Please do hot destroy or throw away this publication. If you have no further use 

for it write to the Geological Survey at Washington and ask for a frank to return it

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY j-\ 

W. C. Mendenhall, Director II

Bulletin 849

INVESTIGATIONS IN 

ALASKA RAILROAD BELT, 1931

BY 

PHILIP S. SMITH AND OTHERS

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1933
tft*... I'

,yW 

.«*- 
CONTENTS

Page 

Foreword, by P. S. Smith_____ _____ __ 1

Progress of surveys in the Anthracite Ridge district, by R. W. Richards 

and G. A. Waring._________________ __________ 5

Lode deposits of the Fairbanks district, by J. M. Hill____________ 29

The Willow Creek gold lode district, by J. C. Ray_____________ 165 

The Mount Eielson district, by J. C. Reed__________________ 231 

Mineral deposits near the West Fork of the Chulitna. River, by C. P. Ross_ 289 

Lode deposits of Eureka and vicinity, Kantishna district, by F. G. Wells_ 335 

The Girdwood district, by C. F. Park, Jr____________________ 381

The Valdez Creek mining district, by C. P. Ross_____________ 425 

The Moose Pass-Hope district, Kenai Peninsula, by Ralph Tuck____ 469

ILLUSTRATIONS

Page 

PLATE!. Geologic map of Anthracite Ridge district_______ ___ 14

2. Geologic sections of Anthracite Ridge district 14

3. Map of the Fairbanks district, Alaska, showing geology, claims,

ditches, and cultural features- __ In pocket

4. Claim map of Cleary Hill mine__________________ 98

5. Plan and cross section of main workings, Cleary Hill mine___ 98

6. Claim map of properties on Fairbanks-Wolf Creek divide_ 106

7. Plan and cross section, Hi-Yu mine_ _ _____ 106

8. Plan and cross section, Ready Bullion mine_____________ 130

9. Claim map of Ryan lode, showing location of workings, roads,

and places sampled in 1931. ____________ 130

10. Plan and cross section, Mohawk mine_______________ 146

11. Geologic map of Willow Creek district _ _ _ 172

12. A, Chalcopyrite-molybdenite stringer in normal quartz diorite; B, Rhombic blocks produced by joining in quartz diorite; 

C, Lucky Shot mine and camp and War Baby mine______ 204

13. Underground workings at Lucky Shot and War Baby mines__ 204

14. Cross' sections of Lucy Shot mine_________________ 204

15. Workings on Skyscraper vein, Martin mine____________ 220

16. Independence and Gold Cord mines __ ___________ 220

17. Map of workings of Independence mine______________ 220

18. Map of Gold Cord mine __ __ _________ 220

19. Map and section of Mabel mine__________________ 220

20. Map of workings of Fern mine _ 220

21. Topographic map of the Mount Eielson district ______ In pocket

22. Geologic map of the Mount Eielson district__________ In pocket

23. Structure sections across the Mount Eielson district_____ In pocket

24. Geologic map of part of the Mount Eielson district_____ In pocket

25. Geologic sketch map of the area near the West Fork of the

Chulitna River, with structure sections_ _________ 296

in
IV ILLUSTRATIONS

Page 

PLATE 26. Sketch map of the Ready Cash prospect, Ohio Creek______ 320

27. Sketch map of the Golden Zone and Mayflower prospects___ 320

28. Geologic map of Eureka and vicinity, Kantishna district.. In pocket

29. Sketch map of lode claims in the vicinity of Friday and Eureka

Creeks_________________________________ 358

30. Assay map of Red Top tunnel___________________ 358

31. Contour sketch map of Little Annie claim, showing tunnel_ 366

32. Assay map of Little Annie tunnel________________ 366

33. Geologic map and sections of Girdwood district, Alaska_ In pocket

34. Geologic sketch map of the Valdez Creek mining district and

vicinity _____________________________ In pocket

35. Placer claim map of the Valdez Creek mining district_____ 448

36. Geologic and topographic map of the Moose Pass-Hope district

showing location of mines and prospects___ _____ 490 

FIGURE 1. Index map showing areas investigated in Alaska Railroad belt,

1931 __________________________________ 3

2. Gold and silver produced in the Fairbanks district, 1903-31 47

3. Directions and dips of veins and faults in the Pedro Dome area. 65

4. Directions and dips of veins and faults in the Ester Dome area_ 65

5. Structural relations of vein quartz in Fairbanks district___ 67

6. Metallization of veins with sulphide and free gold, Fairbanks

district _____ __________________________ 68

7. Camera lucida drawings of polished sections of bonanza ore,

Fairbanks district_________________________ 69

8. Camera lucida drawings of polished sections of bonanza ore

from Bank stope, Cleary Hill mine _ _____ 69

9. Map of Dome Creek drainage basin, showing location of mines

and prospects ______ _ _ _ _ ____ 77

10. Plan of surface workings on vein, Soo mine____________ 79

11. Map of Cleary Creek drainage basin, showing location of mines

and prospects _____ _________ ______ 85

12. Plan of 100-foot and 160-foot levels, Newsboy mine______ 87

13. Plan and cross section, Wyoming mine___ _____ 97 

34. Map of Fairbanks Creek drainage basin, showing location of

mines and prospects _________________________ 103

15. Plan of 60-foot level, Henry Ford no. 3 shaft, McCarty

property _ _____________________ .____ 105

16. Claim map, Hi-Yu mine________________-_____ 109

17. Map of upper Goldstream Creek Valley, including Pedro, Twin, 

and Granite Creeks and Skoogy Gulch, showing location of 

mines and prospects________________________ 113

18. Map of Ester Dome area, showing location of mines and

prospects______________________________ 121

19. Plan of Little Eva adit_______________________ 130

20. Plan of 40-foot level, Eva no. 2 shaft, Stay property______ 131

21. Plan and longitudinal section, Blue Bird shaft__________ 134

22. Cross section and plan of levels, Billy Sunday mine______ 141

23. Plan and section of workings, Grant mine____________ 151

24. Sketch map showing tungsten lode claims in the Fairbanks

district _________________________________ 158

25. Schlieren in rock near upper adit of War Baby mine on Craigie

Creek_________________________________ 178
ILLUSTRATIONS V

Page 

FIGURE 26. Contact of clacite dike rock with quartz diorite country rock

in Lucky Shot mine_______________________ 182

27. Mineralized pegmatite dike on Holland property, on eastern

valley wall of upper Purches Creek__________________ 184

28. Section of vein in Lucky Shot mine, 350-foot level______ 196

29. Section of vein in Lucky Shot mine, 500-foot level_______ 197

30. Section of vein in Lucky Shot mine, raise 553, 75 feet above

500-foot level ________.._________________ 198

31. Flow sheet of Lucky Shot mine__________________ 207

32. Sections of Gold Cord mine____________________ 219

33. Section of Fern mine, showing vein structure and assay values. 255

34. Mean monthly temperature and precipitation at McKinley

Park, Wonder Lake, and Broad Pass_____________ 241

35. Development of normal fault south of Mount Eielson_____ 264

36. Explanation of granocliorite mass in forks of Glacier and 

Crystal Creeks as part of the Mount Eielson mass cut off

by faulting______________________________ 265

37. Generalized sketch map showing location of claims on the

northern slope of Mount Eielson________________ 277

38. Diagrammatic view of the north flank of the valley of Copeland Creek near the ice-filled gorge______________ 306

39. Diagrammatic sketch of faulting along upper Blind Creek 307

40. Sketch map of the lower Ready Cash tunnel__________ 319

41. Sketch map of the Copper King prospect____________ 320

42. Tunnel on the Golden Zone prospect __ _________ 322

43. Sketch map of the Riverside workings______..______ 326

44. Sketch map of the Eagle prospect________________ 329

45. Geologic sketch map arid section of main tunnel of Red

Top claim________________________________ 362

46. Goat Mountain thrust fault___^_________________ 392

47. Normal fault caused by compressive stresses_________ 392

48. Section exposed in placer workings of lower Crow Creek___ 399

49. Cross section of a part of lower Crow Creek Valley______ 399

50. Sketch map of claims of Holmgren-Erickson mine.______ 400

51. Section on northeast side of the " big cut ", lower Crow Creek- 501

52. Sketch map of the upper workings, Bruno Agostino mine. 415

53. Probable location of buried channels near Denali with reference to present drainage__ _____ _ _ 447

54. Contour map of the Tammany Channel____________ 450

55. Contour map of hydraulic cut on the Folk claim- _ 452

56. Sketch map of the lodes on the Timberline prospects ____ 461

57. Plan of underground workings and position of the vein 'at

Hirshey mine____ - - _ 502

58. Plan of underground workings of the Oracle mine, showing

position of the vein 509

59. Longitudinal section of the Oracle vein,, showing limits of

the ore shoot____ 509

60. Sketch map of the mineralized area between Slate and Summit Creeks_____ 511

61. Geologic map of mineralized dike in lower tunnel of the

Gilpatrick property- 513

o
Ut.'AK I IVitN I UJ- fctUUiUY

Please do not destroy or throw away this publication.'"' If you have no further use 

for it, write to the Geological Survey at Washington and ask for a frank to return it

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Bulletin 849 A

PROGRESS OF SURVEYS

IN THE

ANTHRACITE RIDGE DISTRICT 

ALASKA

BY

RALPH W. RICHARDS and GERALD A. WARING

Investigations in Alaska Railroad belt, 1931 

(Pages 1-27)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1933

For aale by the Superintendent of Documents, Washington, D.C. ------ Price 5 cent*
CONTENTS

Page

Foreword, by Philip S. Smith_____----._____...-__-__-._____--___-- 1 

Progress of surveys in the Anthracite Ridge district, by R. W. Richards

and G. A. Waring______.._______._----____-__-_--_-__________._- 5

Abstract.____________________________________________________ 5

Introduction__ _ ____._______-__--_-_-_---___-_-____.-________ 6

Location and area__.__________--__-__---_---_-_-______..-- 6

Previous surveys_-__-_-____---_--_--_-_-_---___.__________ 6

Present investigation__-__-----_-_---__-__-__----__-__-__-_ 7

Acknowledgments. _______-_-__-___----_-____-__-_----____- 8

Geography. _ _____,______________----_--__-_-_--__-_-_--_____-_ 9

Drainage_ _ _______---___----__---------_---__-_--_-___-- 9

Relief________.____..._________________ 9

Climate.._ ________________---_-___-__-____-__-_____-__-__ 9

Vegetation.______________-_.-_-_-_----____-_-.-________-- 10

Population and routes of travel.____________________________ 10

Geology__ _____-_____________------_.-_________._________.__ 10

Principal features._._______-_-------_-___-_-._.__-_.__-._- 10

Stratigraphy and structure-------.-----.---.-----.-._______ 11

Quaternary deposits_-__--__-----------__------____---__--_ 11

Coal......._.....__-_____-____-----------___---.__-_-_-_-____ 12

Outcrops__ __-_.__-__._-_-_----___-__-__----_____-______ 12

Sections____________-__-----_-_-----_-_--_-__-_--_---___ 14

Synclinal area south of Anthracite Ridge.____________________ 18

Classification.______________-__--_.---_____________-____-_ 19

Chemical determinations.-__-_-_-_____-_-__--__.-.-___.__-- 21

Characteristics_ _ ________-------__-_-_______-_-_-________ 21-

Analyses..._-____.________---_---___---__--_-___--_--_.-_ 21

Quantity__--.._._--_...-...--_-_..-...._.....__.... 25

Possibility of undiscovered deposits________________________ 25

Transportation and markets..______________________________ 26

Conclusion __-_._-______.____----_----_------__----_----_--__- 26

ILLUSTRATIONS

Page 

PLATE 1. Geologic map of Anthracite Ridge district__--_.____-_______ 14

2. Geologic sections of Anthracite Ridge district_-._._____.-_.__ 14

FIGURE 1. Index map showing areas investigated in Alaska Railroad belt,

1931..... ___________-___----_-_------ _-_.-.-.-.-_--- 3

NOTE. Bulletin 849 will not be issued as a complete volume, but the last 

chapter will contain a volume title page and index for the use of those who may 

wish to bind together the separate chapters.

n
INVESTIGATIONS IN ALASKA KAILKOAD BELT, 1931

FOREWORD

By PHILIP S. SMITH

To help the mining industry of Alaska and to assist in the development of the mineral resources of the Territory have been the prime 

motives of the Geological Survey's investigations in Alaska during 

the past 35 years, in which nearly one half of the Territory has been 

covered by its reconnaissance and exploratory surveys. It was 

natural, therefore, that the Alaska Railroad, when it undertook intensive consideration of the problem of finding tonnage that would 

increase its revenues, should look to the Geological Survey to supply 

technical information as to the known mineral deposits along its 

route and to indicate what might be done to stimulate a larger 

production of minerals and induce further mining developments and 

prospecting that would utilize its service. Realization of the need for 

this information had long been felt by the officials responsible for the 

operation of the Alaska Railroad, and the need had been partly 

supplied by the Geological Survey, but funds to carry through an 

extensive inquiry of this sort had not been available until 1930, 

when a special committee of the Senate, composed of Senators Howell, 

Kendrick, and Thomas, visited Alaska, studied some of the railroad's 

problems, and successfully urged Congress to grant it $250,000 for 

investigations of this kind.

On the invitation of the Alaska Railroad the Geological Survey 

prepared various plans and estimates for the investigations that 

appeared to be most likely to contribute the desired information as to 

the mineral resources. Selection of the problems to be attacked 

proved difficult, because the choice necessarily was hedged about with 

many practical restrictions. For instance, each project recommended 

must give promise of disclosing valuable deposits a requirement 

that was impossible to satisfy fully in advance, as it involved prophecy 

as to the unknown and undeveloped resources. Then, too, it was 

desirable that the search should be directed mainly toward disclosing 

deposits which if found would attract private enterprises to undertake their development in the near future. Finally, some of the 

deposits that might be worked profitably did not appear likely to 

afford much tonnage to be hauled by the railroad. Under these
2 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

limitations it should be evident that the projects that could be recommended as worth undertaking with the funds available by no means 

exhausted the mineral investigations that otherwise would be well 

justified. In a large sense, all of Alaska may properly be regarded as 

indirectly contributory to the welfare of the railroad, but even in 

that part of Alaska contiguous to its tracks there are large stretches 

of country that are entirely unexplored and large areas that have had 

only the most cursory examination. Although areas of this sort 

might well repay investigation, they were excluded from the list of 

projects recommended because they were not known to contain 

mineral deposits of value, and it therefore seemed better to make the 

selection from other areas that had been proved to hold promise. 

Furthermore, several areas within the railroad zone were excluded 

because their value was believed to lie mostly in their prospective 

placers, which would not yield much outgoing tonnage; others because 

their lodes carried mainly base metals, for which development and 

the recovery of their metallic content in a readily salable condition 

were relatively expensive; and still others because their resources 

consisted mainly of granite, building stone, or some other product 

for which at present there is only a small local demand. 

... After careful consideration ten projects were selected, and the 

funds required for undertaking them were made available. The 

projects that were selected involved the examination of two areas 

principally valuable for their coal (Anthracite Ridge and Moose 

Greek), five areas likely to be principally valuable for gold (Fairbanks, Willow Creek, Girdwood, Moose Pass, and Valdez Creek), 

and three areas whose lodes consisted mainly of mixed sulphides (the 

Eureka area in the Kantishna district, Mount Eielson, formerly 

known as Copper Mountain, and the head of West Fork of Chulitna 

River). The general position of these different areas is indicated on 

t]ie accompanying diagram (fig. 1). A general study of the nonmetalliferous resources of the entire region traversed by the railroad 

was included in the projects to be undertaken, but the results obtained 

were not such as to permit adequate determination of their extent at 

this time.

Examinations were made in the field in each of the selected areas, 

all the known prospects and mines being critically examined and 

sampled so far as time and other conditions permitted. The records 

thus obtained, together with all other information bearing on the 

problems, were then subjected to further study in the laboratory and 

office, in the course of which other Geological Survey specialists whose 

knowledge and experience could be of assistance were freely consulted. 

The outcome of all these lines of analysis has been the reports which 

make up this volume. Although each chapter is presented as embodying the latest and most authoritative information available regarding 

the districts and properties described up to the time field work in them
ANTHRACITE RIDGE DISTRICT

oo Miles

FIGURE 1. Index map showing areas investigated in Alaska Railroad belt, 1931. A, Anthracite Ridge; 

B, Fairbanks; C, Willow Creek; D, Mount Eielson; E, West Fork of Chulitna River; F, Eureka and 

vicinity; O, Girdwood; H, Valdez Creek; I, Moose Pass and Hope
4 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

Was finished, the authors make no claim that all the results they have 

presented are to be regarded as final nor as solving all the problems 

that have arisen. Actually none of the mines have been developed 

to such an extent as to furnish all of the evidence desired to solve the 

problems involved. At none of the properties is any considerable 

quantity of ore actually "blocked out" in the engineering sense of 

that term, so that instead of specific measurements as to the quantity 

and grade of ore the different camps will yield, the Survey geologists 

and engineers have necessarily had to make numerous assumptions 

and be content with estimates and generalizations as to the potential 

resources. Furthermore, the work was planned so as not to invade 

the proper field of the private mining engineer in the valuation of 

individual properties, but rather to occupy the open field of considering 

the districts as a whole.

In two of the districts, Anthracite Ridge and Moose Creek, whose 

value lay in their prospective coal resources, the examinations that 

could be made by ordinary geologic means were not adequate to arrive 

at a final judgment of the resources of the area but pointed to the 

desirability of further tests by drilling. As a consequence additional 

exploration of these districts by means of diamond drilling was 

authorized, and this work was undertaken in the season of 1932. The 

results of these tests were not available at the time the manuscripts 

of the other reports were completed, and rather than delay their 

publication until the later reports could be finished and incorporated 

in the volume these reports have been omitted here and will be 

published later elsewhere.

This is not the place to summarize the detailed findings of the 

geologists as to the merits of the different districts, as those findings

are explained in detail and summarized in the respective chapters. 

Suffice it to say here that on the whole the principal purpose of the 

investigations was carried through satisfactorily and that while the 

studies in some of the districts indicate that they hold little promise 

of extensive mineral development in the near future, others appear to 

encourage development under existing conditions, and still others 

seem to be worth development when some of the existing factors such 

as transportation or price of base metals are improved. That conditions which are now temporarily retarding the development of some 

of the deposits will become more favorable cannot be doubted. The 

entire region is becoming more accessible each year, and as a result 

costs are being lowered and experience is being gained as to the habit 

of the various types of deposits, so that the conclusions expressed in 

this volume as to the resources of the different districts should be 

reviewed from time to time in the light of the then current conditions.
PROGRESS OF SURVEYS IN THE ANTHRACITE RIDGE

DISTRICT

BY RALPH W. RICHARDS and GERALD A. WARING

ABSTRACT

Anthracite Ridge is in south-central Alaska, on the north side of the Matanuska River Valley, about 200 miles north of Seward, the coastal terminus of the 

Alaska Railroad.

The specific object of the investigations in this field during the summer of 

1931 was to collect information regarding the character and extent of the anthracite deposits. These Studies were carried on in connection with similar intensive 

studies of deposits of other kinds of minerals throughout the country tributary 

to the Alaska Railroad.

The coal basin is about 4 miles wide and 7 miles long and lies between the 

ridge and the Matanuska River. The basin is in general synclinal, sharply 

folded and faulted along its north border. The coal beds are in the Chickaloon 

formation, oT Tertiary fresh-water deposits, intruded by igneous dikes and sills 

and unconformably overlying marine Upper Cretaceous beds.

The geologic section as partly exposed in the valleys of the creeks crossing the 

coal basin show that the coal-bearing formation consists chiefly of shales, with 

minor lenticular beds of sandstone and conglomerate. A dozen or more coal 

beds are found in a zone of several hundred feet belonging to either the lower or 

the middle portion of the Chickaloon formation.

Many of the coal beds range from a few inches to about 8 feet in thickness; 

but in one locality on the northwest border of the basin exceptional thicknesses 

of 34 and 24 feet were measured. These beds and others near by are of lowrank anthracite or semianthracite and are found in closely folded and faulted 

sediments further complicated by igneous intrusions. Most of the coal exposed 

in the southern and eastern parts of the basin is found in relatively thin beds 

and is of semibituminous to bituminous grade.

In the absence of actual development work scant reliable data are available 

from surface exposure for estimating the coal reserves of the basin. The most 

definite data are furnished by the locality showing the highest-rank coal, in the 

S>£NW^ sec. 12, T. 20 N., R. 7 E., where a conservative estimate indicates 

750,000 tons of coal, which in this isolated locality can not be regarded as 

sufficient to justify an attempt at commercial development.

The synclinal area immediately adjacent on the south holds possibilities for 

development, although it is not yet proved that thick beds of coal of as high a 

rank as that in the hills to the north are included in this area. However, as it 

is part of the same basin of deposition and as the thin beds of lower-rank coal 

which are exposed on the south side of the basin may thicken and improve in 

quality across the area into the exceptionally thick beds on the north, it undoubtedly warrants further study.

Additional surface prospecting on the flanks of the syncline would only partly 

serve to clear up the problems involved, hence core drilling is regarded as the 

most practical means of reaching definite conclusions as to the presence of coal 

and as to its quality and extent.

5
6 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

Several sites were selected which promised the best possibility of determining, 

the presence of low-rank anthracite within reasonable drilling depth, and a contract was entered into to obtain cores from these holes during the summer of 

1932. These drill-hole samples should supply data for determining conclusively 

whether or not high-grade coal is present in sufficient amount to justify further 

investigation relative to its commercial development.

INTRODUCTION 

LOCATION AND AREA

Anthracite Ridge (fig. 1) is in the south-central part of Alaska,, 

on the north side of the eastern part of the Matanuska River Valley. 

It is best reached from the seacoast, at Seward, by the main line of 

the Alaska Railroad to Matanuska station, near the mouth of the 

Matanuska Valley, 151 miles from Seward, and thence up the branch 

line 37 miles to its terminus at Chickaloon. A trail leads thence 

eastward along the north side of the basin of the Matanuska River,, 

and the south flank of Anthracite Ridge forms the northern boundary 

of the upper portion of the basin. The coal basin lies between the 

ridge and the river and has a width of about 4 miles. It is a structural 

basin limited on the east by the drainage basin of Packsaddle Creek 

and on the west by the drainage basin of Purinton Creek. This 

structural basin, traversed by the trail from Chickaloon, is about 20 

miles east of that station. Its extent is about 7 by 4 miles, and its 

area about 25 square miles.

PREVIOUS SURVEYS

This area was first examined geologically in 1898, when it was 

traversed by a military expedition in charge of Capt. Edwin F. Glenn, 

Twenty-fifth Infantry, United States Army. To this party W. C. 

Mendenhall was attached as geologist, and the report of his observations was published in 1900.*

In 1905 the area was studied by G. C. Martin,2 with special reference to the coal deposits, and in the following year by a party consisting of Sidney Paige and Adolph Knopf, geologists, and R. H. 

Sargent, topographer.3

In 1909 the lower part of the Matanuska Valley, including the area, 

for 2 or 3 miles above Chickaloon, was mapped topographically by 

R. H. Sargent, and in the following year a detailed geologic survey of 

the area was made by G. C. Martin and F. J. Katz, assisted by 

Theodore Chapin.4

1 Mendenhall, W. C., A reconnaissance from Resurrection Bay to the Tanana Eiver, Alaska, in 1898:: 

U.S. Qeol. Survey Twentieth Ann. Kept., pt. 7, pp. 265-340,1900.

> Martin, Q. C., A reconnaissance of the Matanuska coal field, Alaska, in 1905: U.S. Qeol. Survey Bull. 

289,1906.

8 Paige, Sidney, and Knopf, Adolph, Geologic reconnaissance in the Matanuska and Talkeetna Basins,. 

Alaska: U.S. Geol. Survey Bull. 327, 1907.

«Martin, G. C., and Katz, F. J., Geology and coal fields of the lower Matanuska Valley, Alaska: U.S. 

Geol. Survey Bull. 500,1912.
ANTHRACITE RIDGE DISTRICT 7

A topographic survey of the upper part of the Matanuska Valley, 

including the Anthracite Ridge district, was made by R. H. Sargent 

in 1913, and a geologic survey was undertaken by G. C. Martin and 

J. B. Mertie, Jr., assisted by R. M. Overbeck, with special attention 

to the coal resources. A preliminary report of their work was issued,6 

and also the results of further studies made by Martin 6 in 1917. 

In 1918 and 1919 additional data on coal mining near Chickaloon were 

obtained by Theodore Chapin.7

More comprehensive studies of the coal deposits and the mining at 

Chickaloon were made by Capt. W. P. T. Hill, T. E. Savage, and 

W. T. Foran, for the Navy Alaskan Coal Commission.8

In 1924, S. R. Capps, assisted by K. K. Landes,made further studies 

of the geology and mining developments in the area, with special 

attention to the structure and geology of the district.9

PRESENT INVESTIGATION

These earlier studies had shown the presence of anthracite and 

coals of lower rank in the Anthracite Ridge district, but their scope 

had not permitted intensive prospecting and tracing of the outcrops 

of the coal beds to determine their extent and thickness in sufficient 

detail to ascertain the commercial possibilities of the area.

In 1931 Congress requested and provided for a more thorough 

inventory of the natural resources of the region tributary to the 

Alaska Railroad, to facilitate the development of mineral deposits 

that might afford a source of sustaining revenue for the railroad. As 

the anthracite of this district, as shown by the analyses of the samples 

already obtained, compared favorably in quality with some anthracites of Pennsylvania, was in general superior to other grades of coal 

mined on the Pacific coast and far superior to the lower-rank coals 

now mined in the lower Matanuska Valley and Nenana River Valley, 

it appeared that intensive prospecting of this area might demonstrate 

that this high-rank coal, which was known to crop out at one locality 

in a bed over 30 feet thick, had a sufficient areal extent to justify 

exploitation. It was fully realized at the same time that, in addition to the question of tonnage, economic questions regarding utilization and markets would have to be considered before the expenditures 

involved in construction of additional transportation facilities could 

be regarded as warranted, but for the time it seemed essential to

i Martin, G. C., and Mertie, J. B., Jr., Mineral resources of the upper Matanuska and Nelchina Valleys: 

U.S. Geol. Survey Bull. 592, pp. 273-299,1914.

8 Martin, G. C., Geologic problems at the Matanuska coal mines: U.S. Geol. Survey Bull. 692, pp. 269-282, 

1919.

' Chapin, Theodore, Mining developments in the Matanuska coal fields: U.S. Geol. Survey Bull. 712, 

pp. 131-167, 1920: Bull. 714, pp. 197-199, 1921.

s Hill, W. P. T., Final report of the Navy Alaskan Coal Commission to the Secretary of the Navy, 1922 

(manuscript).

 Capps, S. K., Geology of the upper Matanuska Valley, Alaska, with a section on the igneous rocks, by 

J. B. Mertie, Jr.: U.S. Geol. Survey Bull. 791, 1927.

165264-33 2
8 INVESTIGATIONS IN ALASKA KAILROAD BELT, 1931

determine first of all how much high-rank coal was present in the 

area.

The specific object of the investigations here recorded was to collect 

all geologic-information available from surface examination, in the 

hope that this information would permit a definite conclusion to be 

reached regarding the value of the anthracite deposits.

During the summer of 1931 two field parties, a topographic party 

in charge of L. 0. Newsome, topographer, and a geologic party under 

R. W. Richards, geologist, were assigned to the area. Mr. Richards 

was assisted by G. A. Waring, geologist, during the second half of 

the field season. A base camp was established near Purinton Creek, 

on the bench on the south slope of Anthracite Ridge, at an elevation 

of 2,960 feet, on June 11, and maintained until September 13, 1931. 

Transportation connection with the railroad at Chickaloon was provided by a train of pack horses in charge of Len Oules, packer. Peter 

Sumanoff served as cook for the combined parties throughout the 

field season. The assistants to the topographic party were Fred 

Kubon, Sam Morgan, and Tom Scott. The laborers engaged in the 

prospecting work incident to the coal investigation for varied portions 

of the season were Hank Edwardson, foreman, Patrick McCullum, 

E. P. Shannon, Peter Toloff, Jake Angelo, and Frank Million.

Outcrops of coal beds and blossom indicative of coal were examined 

during the season at many localities in the area; of these 72 are indicated on the accompanying map and briefly described in the list on 

pages 12-13. In addition, 40 localities, some of which are more fully 

described on pages 14-17, were prospected by pits or trenches to 

expose the coal beds more completely.

It was found impracticable because of thick overburden of alluvium 

and moss, to trace or correlate individual coal beds except for short

distances, as in the case of the 30-foot anthracite bed, which was 

traced only about an eighth of a mile north and half a mile west of 

the principal outcrop, and consequently incomplete data were obtainable in the portion of the area lying on the south slope of Anthracite 

Ridge toward the Matanuska River, in which there is a possibility 

of high-rank coal being present at depth in sufficiently thick beds to 

afford commercial tonnage.

ACKNOWLEDGMENTS

The investigation was carried on under the general direction of 

S. R. Capps, geologist in charge of the projects in the Alaska Railroad 

belt, and his instructions and assistance, based upon his own previous 

experience in the area, were of the utmost value. Many courtesies 

were extended to the party by the Alaska Railroad, through the 

thoughtfulness and interest of Col. O. F. Ohlson, general manager. 

Special mention is due to the United States Bureau of Mines in 

affording prompt analytical service at the Anchorage laboratory, by
ANTHRACITE RIDGE DISTRICT 9

its chemist, Maurice L. Sharp. J. J. Corey, coal-mining engineer of 

the Anchorage office of the United States Geological Survey, rendered 

noteworthy assistance to the party at numerous times and places.

GEOGRAPHY 

DRAINAGE

The Anthracite Ridge district (pi. 1) is drained by several creeks 

that flow southward from the crest of the ridge to the Matanuska 

River. In order eastward the principal ones are known as Purinton, 

Cascade, Winding, Muddy, and Packsaddle Creeks. All carry water 

throughout normal summers, derived chiefly from the melting snow of 

the uplands. Their headwaters have cut deep ravines in the steep 

upper slopes of Anthracite Ridge. In the middle portions of their 

courses, where they cross moderate slopes partly covered with glacial 

deposits, the streams have shallow winding channels. In their lower 

courses their gradients steepen again, and the streams have cut deep 

into the cliffs along the north border of the channel of the Matanuska 

River.

RELIEF

The valley of the Matanuska River, along the south border of the 

area under consideration, is from 1,100 to 1,300 feet above sea level. 

Cliffs 200 to 500 feet high border the north side of the river, and 

the surface thence rises at an average slope of 500 to 600 feet to the 

mile to the base of steeper slopes that in turn rise to the crest of the 

ridge, 5,000 to 6,000 feet above sea level. In its western part the 

fairly uniform southward slope of the surface is broken by several 

prominent east-west ridges and in its central part by minor ridges 

and hills.

CLIMATE

Although there is a range in elevation of 5,000 feet within this 

small area, the climate is not so different between its highest and 

lowest portions as might be expected, for the prevailing winds blow 

lengthwise of the Matanuska Valley, bringing storms from Cook 

Inlet. These sweep along the slopes of the ridge, with perhaps 

snow and sleet in the upper portions at the time of cold rain in the 

lower. The open season for the area as a whole is from about May 

15 to September 15. About the middle of September in normal years 

the nights begin to be frosty, and two or three weeks later snow falls. 

The winter precipitation is not heavy, though 3 or 4 feet of snow may 

cover the ground until spring. June is perhaps the pleasantest 

month of the year; for in July, August, and early September there is 

likely to be a large proportion of days with rain and mist drifting up 

the valley from the inlet. The mean annual precipitation at Matanuska for 1917-21 was about 14 inches; the mean in the Anthra-
10 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

cite Ridge district is probably somewhat higher. The records at 

Chickaloon for 1919-23 showed mean temperatures well below 

freezing for the months of November to March, but above 50° during 

June, July, and August.

VEGETATION

The lower half of the coal basin is partly timbered with spruce, 

with some birches and cottonwoods near the watercourses. Much of 

the southern portion has been burned over within recent years, however, and is covered with fallen timber and young second growth of 

birch and cottonwood. The timber line is at an elevation of about 

2,800 feet, though along some of the shallow creek valleys spruce 

extends above 3,000 feet. The trees are nearly all less than 12 inches 

in diameter and because of their small size and distance from easy 

transportation have little commercial value.

In the sparsely timbered areas and on portions of some of the higher 

slopes there is sufficient grass in summer for the grazing of pack 

animals, but this feed is killed by the first sharp frost.

POPULATION AND ROUTES OF TRAVEL

In the basin of the Matanuska River above Chickaloon there were 

in 1931 no permanent inhabitants. There was a cabin on Boulder 

Creek occupied at times by hunters, a similar cabin beside the trail 

near Kutzkatna Creek, and one on upper Hicks Creek. Beside 

Tatondan Lake, near the mouth of Gravel Creek, on the south side 

of the Matanuska River, white hunters had established a camp. All 

these places were reached by the trail that leads northeastward from 

Chickaloon, parallel with Boulder Creek, and then swings south of 

east across the Anthracite Ridge district and eastward to the Nelchina gold-mining district, 40 miles away. The trail is kept in condition for pack-horse travel by the Alaska Road Commission.

GEOLOGY 

PRINCIPAL FEATURES

In general the geology of the region represents three main groupings. The Chugach Mountains, south of the Matanuska River, are 

composed chiefly of granitic rocks, altered sedimentary rocks, and 

bedded volcanic materials. The Talkeetna Mountains, to the north 

of Anthracite Ridge, are composed largely of granitic rocks. Anthracite Ridge and the structural basin immediately south of it are composed of comparatively unaltered shales, sandy shales, and sandstones, 

and the basin includes also minor areas of intrusive igneous rocks, 

chiefly diabase.
ANTHRACITE RIDGE DISTRICT 11 

STRATIGRAPHY AND STRUCTURE

Around the border of the basin marine Upper Cretaceous rocks 

(Matanuska formation) are exposed. These are mainly black shales, 

in which molluscan fossils have been found in a few places, and 

medium-grained indurated greenish-gray to brown sandstones. Over 

the main part of the basin dark-gray shales with minor beds of sandstone and conglomerate are exposed. Impressions of plant remains 

in many of the shale and sandstone beds and the presence of coal 

beds in some places show that the deposits are of fresh-water origin. 

These beds make up the Chickaloon formation, of Eocene age, which 

was first described by Martin and Katz 10 in 1912.

Considerable amounts of igneous rock, chiefly diabase, have been 

intruded into these sediments as sills. The larger masses exposed 

form prominent hills and ridges and are apparently 100 to 200 feet

thick. Many of the smaller sills, however, are less than 20 feet thick, 

and some of the igneous bodies break across the bedding as dikes 

rather than sills. They are probably of Pliocene age.

The structure of the basin is synclinal, but with a broad upfold 

through the central part. On the north the beds are highly tilted, 

with faulting and close folding; and the rocks that form the crest of 

Anthracite Ridge are upfaulted above the beds of the lower slopes. 

The character of this folding and faulting is shown in the three cross 

sections of plate 2.

The folding along the flank of the eastern half of Anthracite Ridge 

is exhibited by a zone, 30 to 50 feet thick, of whitened conglomeratic 

sandstone underlain by whitened shale. This zone shows prominently on the bare slopes of dark shale and sandstone and is indicated on plate 1. Its extent and fairly uniform thickness suggest 

that the whitening was caused by heat generated from some source, 

possibly from intrusive igneous rocks. However, there are no evidences of an extensive sill which might have supplied the heat for this 

alteration of the rocks.

QUATERNARY DEPOSITS

During the glacial epoch the valley of the Matanuska River was 

evidently filled with ice, for glacial gravel is found on the slopes to 

an elevation of 4,500 feet and higher. The front of Matanuska 

Glacier, from which the Matanuska River issues, is about 8 miles 

east of the east border of the district under discussion. The lower 

portions of Packsaddle and Muddy Creeks cut through extensive 

deposits of glacial-moraine gravel and boulders, but the main part 

of the district is remarkably free from such material. For the most 

part only thin patches of gravel or scattered pebbles indicate the 

former presence of glacial ice over the whole valley.

"> Martin, G. C., and Katz, P. J., Geology and coal fields of the lower Matanuska Valley, Alaska' 

U.S. Geol. Survey Bull. 500, pp. 42-52, 1912.
12 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

COAL

OUTCROPS

The only known mineral deposits of possible economic importance 

in the Anthracite Ridge district are the coal beds of the basin to the 

south of the ridge. This is structurally a separate basin from that 

of the Chickaloon area, to the west, where some mining of the coal 

has been done. Because of the presence of coal on the north side 

of the basin the area was surveyed by the United States General 

Land Office in 1915, and two tracts were designated as leasing units 

(nos. 18 and 19) of the Matanuska coal field. These were filed on 

by individuals, but no development work was done.

During the summer of 1931 about 40 prospecting openings were 

dug by the Geological Survey party in the area, mainly on obscure 

outcrops of the coal beds in an attempt to uncover concealed beds. 

From 14 of the openings 21 samples were collected by the writers 

and were analyzed by Maurice L. Sharp, chemist, of the United 

States Bureau of Mines, stationed at Anchorage. The results of his 

analyses are tabulated on page 22.

Outcrops of coal noted at other places in the area are shown on 

plate 1, and additional data concerning them are summarized in the 

following table:

Outcrops of coal in the Anthracite Ridge basin

Map 

no.

1

2 

3

4

5 

6 

7 

8

9

10 

11 

12

13 

14

15 

16 

17 

18 

19 

20 

21 

22

23 

24 

25 

26 

27 

28

29 

30

Location

T. 20 N., R. 7 E. 

NWMSWM sec. 3 

SEMSWJOec. 3 

SWMNEMsec.il...

NWKSEMsec.il 

NE^NWMsec. 12.. 

. do. . .......

.....do-..:..- ... .

SWJ£NWMsec.l2..

SEMNW^sec.12...

.....do-_ ........ .

....-do-..... . .... 

..... do 

SWMNW^sec.12..

SEMNWMsec.12 

NE}£SW>£sec.l2 

NWKSE)isec.l2 

.....do.. ... ... ... 

.....do.. .........

..... do.. .....

.....do .........

NEJiSEMsec.12... . 

SWMNWJisec.23-

NWKSWJisec.23.. 

NE}£SWJisec.23 

SEMSW^sec.23_... 

NWJiSEJisec.25 

NEMNW^sec.26.. 

 do . .......

SWJiNE^seo.26 

NWJiSEJisec.26...

Character

Coal, 5 beds _ ..

Coal . 

Coal, 3 beds.....

Coal. . .......... 

 -do- - 

Coal, 4 beds ..... 

 do 

Coal.. 

Coal, 4 beds _ ..

Coal, 2 beds ..... 

Coal, 3 beds ..... 

Coal, 4 beds .....

Coal, 6 beds . 

Coal, broken.. ..

.....do ....... 

.....do .......

..... do ....

.....do .......

Coal.. __ . _ - 

Coal and coaly 

shale. 

..... do-. ..... 

Goal.. .......... 

Coal, 2 beds. 

Coaly shale ..... 

Coal, 6 beds _ 

Coal... ___ 

Coal, 3 beds 

Coaly shale 

Total thickness

Ft. in. 

5

2 

2 9 

2 

4 

6 2 

6 8 

7 9

8

5 10 

6 4 

24

3 

34

2 

6 

5 

5 

3 

2 

2 

3

1 

6 

3 

2 

16 6 

1 6

1

1

Dip of beds

70° N. 25° E-.. .

70° N. 20° E.. 

45° S. 30° W ......

70° S....... .........

46° S _ _. T __ 

60°S .......

40° S. 20° W.........

60° S. 25° E. ........

30° S. 15° W 

25° S. 10° W 

30° S ...........

35° SW ... ....

40° S. 

20° N. 20° E ......

10° N. 30° E . 

30° S. 10° E ....

30° S ...... .

30° 8. 10° E .

30° S ..... .... ....

30° S ... ... .

30° N. 20° E- __ ...

70° N ........

20° N. 20° E ......

20° N. 30° E... _

50° N. 70° E... _ ...

45° S. 80° E. ........

60° N. 20° E... 

60° E _ . _ . ...

50° S. 70° E 

10° NE... ...... _ -

Analysis 

no.

4488

4484

4480

4490 

(3'6" bed) 

4487, 4390 

4388, 4389 

4444,4485, 

4486.

4443, 4445, 

4446. 4391

4481

4479

Bank

Semibituminous. Unclassified. 

Do. 

Bituminous. 

Unclassified. 

Do. 

Do. 

Semianthra 

cite. 

Do.

Do. 

Do. 

Semianthraciteand semibituminous. 

Unclassified. 

Semianthracite. 

Unclassified. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Bituminous.

Unclassified. 

Do. 

Do. 

Do. 

Do. 

Semibitumlnous. 

Unclassified. 

Do.
ANTHRACITE RIDGE DISTRICT

Outcrops of coal in the Anthracite Ridge basin Continued

13

Map 

no.

31

32

33

34

35

3ft

37 

38

39

40

41

42

43

44

45

46

47

48

49

60

61

62

53

M

65

66

67

68 ' 69

60

61

62

63

64

65

66

67

68

60

70

71

72

Location

T. SO N., R. 8 E. 

8EMNWtfsec.7....

NWjisWJisec.7...

SWJiNE^sec.7 

SE^NE^sec.7.....

NE^SWJisec.9 .

SE^SWMsec.9.....

SWMSE^sec.9 - 

SEXSE^sec.9.. 

.....do-_._- ...... ...

NW^NWJisec. 15.

SW^NW^sec.15..

NWHSWJiseo.15..

SEHSW^sec.15....

NWMNWJi sec. 16.

NEMNW}isec.l6..

..... do.. 

NWJiNEMsec.16-

NE^NE^sec.16 

SEMNWtfseo.16 

NEMSWMsec.18 

.....do.. ............

NW}4SEMsec.l6 

NE^NE^sec.17 

MWl/XrWl/ con 17

NWJiNE^sec.18.-

SW}iNE^sec.l9 

NE^SWMsec.19 

NEJiNW^sec.21..

NE^NE^sec.21 

NE^SE^sec.21 .

NW^NWM sec. 22.

SE^NW^sec.22...

SW^NEJisec.27...

NW}<SW^sec.27.-

8E.WSWUsec.27....

NW^NEKsec.30..

SW^NE^sec.30...

SEKNWj2seo.30 

NEKNEJi sec. 33...

NWJ<NEKsec.33..

8E^NW)iseo.33..-

Character

shale.

.....do. ......

Coal, 5 beds, 

closely folded, 

on side of 

ridge. Coal, same as

preceding, on 

crest of ridge.

__ do... .......

.....do.. ........

Coal..... ....

 ..do.. 

 ..do... .

thin beds.

Coal... 

thin beds.

eral thin beds.

thin beds. 

Coal 

..... do .... .

 ..do.. ...

..... do.. 

.....do 

... ..do ..

 do 

Coaly shale.. ...

.....do 

Total thickness

Ft. in. 

2

4

2

6

3

8 3 

20

2

1 6

6

6

5

3

5 9

5

3

2

6

5

2

7

1

1

1

1

2

10 1

1

2 9

1

1 4

6

1

6

1

1

5

Dip of beds

30° N. 20° E.........

20° N., overturned..

10° NW...... ....

80° NW ... ...

80° N. 30° W.-800 S. 

30° E.

60° N. 30° W.... . .

60° S. 10° E. .

60° S., and faulted ...

30°SW.._____ .

30°SW 

60°N.- 

60°N 

20° S. 20° E. ........

50° N. 30° W... .....

70° N. 20° W 

20° 8-80° N., overturned. 

30° SW. ......

30° SW.... .....

10° N. 10° E-. 

60° SW.... ...

50°S 

30° 8.30° E.. .......

10°S.30°E- _ ..

5°S. 30° E.. .

20° W. _ 

10° NW....... .... ..

30°S. 10°E ....

20° NW ....

20° NW... 

60°W ...

30° NW... .

30° N. 40° W 

10° N. 30° E.........

20° N. 30° E. 

20° N. 30° E. ___ ..

30° NW.. ...........

40° N. 30° W........

40° N. 30° W.. ...

Analysis 

no.

4483

dARQ

djlfift

4dS9

Rank.

Unclassified.

Do.

Do.

Do.

Do.

Do.

Bituminous. 

Unclassified.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.
14 INVESTIGATIONS IN ALASKA KAILROAD BELT, 1931

SECTIONS

Samples for analysis were taken mainly from pits in the 

sec. 12, T. 20 N., R. 7 E., where the thickest beds and best quality 

of coal were found. The sections- at nine of the ten localities listed 

in this quarter section and the beds sampled for analysis were as 

follows :

Sections in NW}i sec. 12, T. 20 N., 

R. 7 E.

Locality 5

Shale. Feet 

Coal (semianthracite) _______ About 4

Shale.

Locality 6

Shale. Ft. in. 

Coal (semianthracite) ________ 1

Shale_------------_----------- 6

Coal (semianthracite) ________ 1 2

Bone _ _____._---_--------- 6

Coal (semianthracite) ________ 3

Coal (semianthracite) ________ 1

Bone...- __--______--------- 1

Shale, brown.

Locality 7

Shale. Ft. in. 

Coal (semianthracite) ________ 3

Diabase sill_ _____________

Coal (semianthracite) _____

Shale. ----.--.--------

Coal (semianthracite) _____

Shale -----------------

Coal (semianthracite) ___--

Shale, black.

Locality 8

Soil and broken coal. Ft. in. 

analysis 4480, 

of the 7 feet 

9 inches of 

coal (semianthracite)

Coal--_-_. 

Shale_____ 

Coal and clay 

Coal---.-

Shale.

Shale. 

Diabase sill

Locality 9

Ft. in. 

1

Coal, broken, and shale __ __- 7 

Coal.. ___ ________________ 1

Shale. __ _. ___ ________ _

Coal__-.__ _ _______ ____ 1

Coal and shale

Sections in NW% sec. 12, T. 20 JV.» 

R. 7 ^. Continued

Locality 9 Continued

Coal (analysis 4490, semian- Ft. in. 

thracite) __ ______________ 3 6.'

Shale _______ _ ____ __. 1

Diabase sill _ __-__-____.___ 2

Shale.

Locality 10

Shale. Ft. in, 

Coal (analysis 4487, semianthracite) _ _._---_____-- 3

Diabase sill. _.________..__ 6-10

Coal, broken_____..__-___- 1 8"

Shale, gray. ____-_______.. 1 2

Coal, broken... __ _________ 10

2 1C*

Coal (analysis 4390, semianthracite) _ _____________

Shale.

Locality 11

Ft. in.

Coal (analysis 4388, of the 3 

feet 6 inches of coal, semianthracite) __ __----____._-_ 2 8 

Shale __ --____-..._______- 3

Coal.. -------_.--__________ 1Q

Diabase sill. ________________ 5

Coal (analysis 4389, semianthracite) _ _____-_...__-__ 2 10

Shale.

Locality 12

Shale. Ft. in* 

Coal (analysis 4444, semianthracite) __ __-_____-____- 10

Coal 1 analysis 4486, of the 7 [ 3 

Shale \ feet of coal (semian- ! 3 

Coal J thracite) [ 4

Coal v (analysis 4485,. semibituminous) ________________ 7

Shale _-___________-__. 1

Locality 14

Shale.

Coal | analysis 4443,, of the 10 

Shalej- feet 6 inches of coal 

Coal J (semianthracite)

Ft. 

3
a 

o

f O

CO uj

g 5.

2. O 

^

>

I 0

£ H

o i i -

.M 2 ^

CO ^

a 

o

Pliocene Recent

"^H

£. i

Hi

&i

^x si a^« - 

i -I

P* 

& 3 

^l0

ag -

^n ?

S^3

^l&

P

§2 

^ ji

" ^ ^ 

 *s 2

i|g

3&

l^g

ill

p CD

a^

&?

^S° 

55.

JURASSIC CRETACEOUS TERTIARY QUATERNARY
U.S: GEOLOGICAL SURVEY BULLETIN 849 PLATE 2

\-s.ooo

Section alon^ line A~A'

\-3,000

V-2,OOO

h I,OOO'

B

Anthracite 

Ridge 

Kmy$

\-5.OOO

-^000

\-3.000'

1-2,000

\- l,OOO

Section alon^ line B-B

Anthracite 

Ridge

W

Tc

Tc

Coal ^r^lP'- s ,in M 

^^SO^ Coa^' 

W

/;>'T, f ' r 'x! »6<:.r '

\-6,OOO'

\-5,000'

h 4,000

V 3,OOO

2,000'

\- I.OOO

Section along line C-C'

iMile

GEOLOGIC SECTIONS OF ANTHRACITE RIDGE DISTRICT.

For liaes of sections see plate 1.
15

Sections in NWy* sec. 12, T. 20 N., 

R. 7 E. Continued

Locality 14 Continued

Coal ] analysis 4445, of the 6 

Bone[ feet 6 inches of coal 

Coal J (semianthracite) __ 

Coal with thin shales (analysis 4446, semianthracite) _ _

Ft. 

3 

1 

3

Sections in NWy4 sec. 12, T. 20 N., 

R. 7 E. Continued

Locality 14 Continued

Coal (analysis. 4391, semian- Ft. in.

thracite)__--____-_-_----_- 10 

Shale.

To the west and south the sections at four localities from which 

coal samples were taken for analysis are as follows:

Section at locality 1, sec. 3, T. 20 N., 

R. 7 E.

Shale. Ft. in.

Coal shattered

Shale

Coal

Shale

Coal

Shale

Coal

Shale

Coal

analysis 4488, a

composite of

 the five thin«

coal beds

(semibituminous)____

2

6

6

6

9

2

10

3

10

Shale.

Section at locality* 4* sec. 11, T. 20 N.,

R. 7 E.

Shale, black. Feet

Coal and coaly shale (analysis

4484, bituminous). ___________ 2

Shale, black.

Section at locality 22, sec. 28, T. 20 N.,

R. 7 E.

Shale, black. Fed 

Coal and coaly shale, crushed

(analysis 4481, bituminous)____ 3 

Shale, gray; leaf impressions. _ ___ 2 

Sandstone, gray-brown, thinbedded.

Section at locality 28, sec. 26, T. 20 N., 

R. 7 E.

Ft. in. 

Diabase__--_-__-_-__.______ 20

Shale, sandy._______________ 35

Shale, gray.________________ 5

Shale, black_________________ 1

Coal, dirty.___.______ 6 

Shale, black___._._._______ 1

Shale, gray.__._.__.____.___ 2

Sandstone._________________ 8

Shale, sandy._______________ 20

Coal (analysis 4479, semibituminous) __________________ 1 5

Sandstone, brown ____________ 6

Shale, gray.
16 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

The thickest section measured in the southern part of the basin was 

in the side of the canyon of Purinton Creek, in the NE%NE%NW% 

sec. 26, T. 20 N., R. 7 E., as follows:

Section exposed on north side of canyon of Purinton Creek, sec. 26, T. 20 N., R. 7 E.,

locality 27

Ft. in. Ft. in.

125

15

Gray shale_____--_-___-____ 2

Ferruginous sandstone.

Coal, shattered-_-____--____ 2

Gray shale, with several bands

of ironstone concretions. __

Gray sandstone (dip 85° N.

20° E.) --

Gray shale alternating with 

brown sandstones.________ 38

Brown shale.______________ 2

Coal, shattered-_-__--_-____ 4

Gray shale, with thin ferruginous sandstone bands 

(beds nearly vertical at 

base of section, at creek) __ 75

544

Gray shales alternating with

brown ironstones____._.__ 100 

Coal (bituminous) __-_.._-__ 2 

Gray shale_______________ 2

Ferruginous sandstone. _____ 1 

Gray shale_______________ 3

Coaly shale______-____--__. 3

Gray shale_____________ 6

Gray lenticular sandstone

(dip 60° N.)_----------- 5

Coal (bituminous) __________ 1

Gray shale_________________ 15

Coal, grading to coaly shale.. 5 

Gray shale with lenticular

sandstones 6 inches to 3 feet

thick..___________ 60 

Coal (bituminous)-______.-_ 2

Gray shale with lenticular

sandstone 6 inches to 3 feet

thick......___._.___.._.. 75

The sections at the four localities in the eastern part of the basin 

where coal samples were taken for analysis are as follows:

Section at locality 87, sec. 9, T. 20 N., R. 8 E. 

[Measured southward along west side of ridge, to axis of sharp fold]

Ft.

Shale with thin sandstone beds. 

White sandstone..___________ 7

Gray shale________________ 14

Buff sandstone.-----------.. 2

Shale...______-----_.-- 6

Coal......._______-----

Shale.......-------.-___.--

Black, siliceous shale.________ 1

Gray shale________________ 4

Black shale.________________ 3

Gray shale________________ 2

Gray shale _ ___--_-____-_._ 1

Coal____-______--_.. __----.

Shale and coaly shale ________ 2

Black shale

fi

6

10

8

10

8

6 

7 

9 

5 

5

3

Coaly shale. ________________

Black shale. _______ _______

Gray shale _ ________ ___ __

Coaly shale. ________________

Gray shale _ _______________

Black shale_ ________________

Coaly shale. ... ________ ___

Gray shale _ __________ ____

n , (analysis 4483, of)

 , . I the 6 feet 2 inches I Shale. ___< , . ,, ., . > ~, , 1 of coal (bitumi-[ Coal _ _. v V, nous) )

Gray shale (axis of sharp anticlinal fold)__--___-_-___.__

I

1

1

1

5

1

5

?,

3 

6

50

8

8

1

9

?,

9

7

4

10

8 

4

8

8
ANTHRACITE RIDGE DISTRICT 17

Section at locality 51, sec. 16, T. 20 N., R. 8 E.

Top of bluff. Ft. in. 

Diabase sill.___----__._____ 75

Baked shale.,__.-----______ 4

Gray shale_.___.---___-__ 34 

Black shale, with 2 inches of 

coal___-__--------------- 4

Coal, lensing to bone -----___ 1

Black shale_____------__--_ 8

Black sandy shale.----.---- 8

Thin-bedded black sandstone 

and black micaceous, sandy 

shale.________--,__ 10 

Black shale with thin sandstone__--_--------_---- 16

Coal lens---..--------.---- 2 6

Dark-gray shale. .. 30

Gray shale with ironstone._._ 27 

Black shale with ironstone. __ 15 

Gray to brown cross-bedded 

sandstone-.--.----------. 8

Ft. in. 

Dark-gray shale.._____-_--- 15

Gray cross-bedded sandstone

lens_____-___.-.--._--- 17

Gray shale_____ _.. 23

Black shale.____.__----_--- 3

Ironstone____-_._____-_---- 1 9

Coaly shale__-_-.-------__- 4

Coal_1 analysis 4489, of thef 3

Shale.-I 6 feet 2 inches' of| 4

Coal_ J coal (bituminous) [ 3 2

Dark-gray sandy shale. _ _ _ . . 2

Ironstone___--____---_----- 2

Gray sandstone__-------- 9 6

Coal and coaly shale_-_---_. 9

Gray shale.____.._... 6

Gray to yellow sandstone..__ 1 6 

Shale with thin sandstone__ 30 

Shale. 

364 6

Section at locality 53, sec. 17, T. 20 N., R. 8 E.

Ft. in.

Gray shale, with thin gray 

sandstone and ironstone 

bands-----.-------.-.--- 100

Coaly shale._-------------- 5

Coal and coaly shale________ 1

Shale with ironstone bands_ 10 

Coal..-------------------- 1 3

Coaly shale.__--_-__-__-___ 1 

Shale and coaly shale _______ 4

White sandstone _-_____- 1

Coaly shale. __-------_----- 4

Ironstone.--.-------------- 2

Ft.

Clay shale.. 

Coal.______

Ironstone___

Coaly shale._.____--_--_-

mlysis 4466, 

of the 4 feet 

10 inches of 

coal (bituminous)

Coal and shale, broken.-..

Shale with ironstone.

Sandstone. __.___.-.__--_

Shale .-..--...-------

3

1

4

3

40

Diabase sill. _ . ___..--.-__-_ 10

Section at locality 62, sec. 22, T. 20 N., R. 8 E.

Top of bluff. Ft. in.

Gray shale________.-_-___ 3

Ironstone_________________ 6

Gray shale___________ 22 6

Buff sandstone-___--_-_--__ 10

Gray shale --------------- 5 3

Buff sandstone..---------.. 1

Gray shale___________ 10 2

Black shale.._________ 2 6

Coal_I , . . A0ty , ,, f 3 6 Shale., analysis 4482, o the

Coal...) 7^ feetofcoal 1 4

Black shale_..._..___ 2 6

Gray shale__---__-_--____ 5

Buff sandstone-_-.-_--___-__ 1

Gray shale_.__-__.--. 10 8

Ironstone ...--------___ 6

in. 

4

1

10

4

197 6

Ft. in. 

Gray shale______---_-__-_ 14 6

Black shale. __________ 1 8 

Coal...._---.....-------._ 1 4

Shale____._________ 1 

Coal.._____________ 1 3 

Shale.....-._.....--_-..--. 1 2

Sandstone. _--__----------_ 1 6

Shale.._.___.__----- 2

Sandstone.-____.------.-.- 2 6

Thin-bedded sandstone...... 3 9

Black shale._______---.---. 8

Gray shale, with thin sandstone. __-___.---_.___- 43 

Gray sandstone__-.--_-._ 4 

Shale. 

150 8
18 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931 

SYNCLINAL AREA SOUTH OF ANTHRACITE RIDGE

The diagrammatic structure section A-A', plate 2, shows the 

writers' interpretation of the distribution and deformation of the 

rocks of the Chickaloon formation as exposed along Purinton Creek. 

The zone of complex folding, intrusion, and faulting on the southern 

slope of Anthracite Ridge in which the thick beds of hard coal are 

found is succeeded by (1) a synclinal area about \% miles wide, 

characterized by low dips, gradually steepening toward (2) a fault 

zone beyond which beds dipping at a low angle to the north continue 

to a zone of prominent intrusives, followed by (3) another zone of 

steeply dipping beds a quarter, of a mile wide, containing coal beds 

and in fault contact with rocks of Upper Cretaceous age.

These southern coal beds may represent the coal zone on the south 

slope of Anthracite Ridge, but it is not possible to project them with 

certainty northward across the structure section or to estimate with 

any degree of accuracy the position they may occupy in the synclinal 

area. However, the outcrop of a 2-foot bed of bituminous coal, 

about half a mile west of the line of the structure section, at locality 

4, sec. 11, T. 20 N., R. 7 E., approximately on the strike of the southernmost intrusive mass found on the north flank of the syncline, suggests the presence of a coal zone at moderate depth.

The synclinal structure of the area in the IK-mile zone is clearly 

indicated by the attitude of the resistant sandstones protruding 

through the gravel and moss, which effectually conceal the softer beds.

The column of Chickaloon sediments forming the south limb of 

this syncline measured from the axis to a fault a few hundred feet 

south of the first intrusive sill on that side of the fold (where the dips 

change from about 60° to 10°) includes approximately 2,000 feet

of beds in which no coal was found, although coal may be present in 

parts of the interval that are concealed. Continuing from this line 

of faulting nearly 3,000 feet of Chickaloon rocks crop out to the fault 

contact with the Upper Cretaceous. Presumably these beds represent 

the continuation of the beds measured in the 2,000-foot interval, 

repeated to an unknown extent by faulting. The absence of recognized key beds makes it impossible to estimate accurately, because of 

this faulted sequence, the total thickness of the Chickaloon formation 

before the faulting took place. Martin n estimated it at 2,000 feet 

or possibly more. The writers may be in error in attributing the 

additional 3,000 feet present in this area to repetition by faulting, 

and the total thickness may even be as much as 5,000 feet.

Evidently, however, sufficient Chickaloon beds are present in this 

synclinal area between the Matanuska River and Anthracite Ridge to 

include the same coal zone that is exposed on the south flank of the

11 Martin, G. C., and Katz, F. J., Geology and coal fields of the lower Matanuska Valley, Alaska: U.S. 

Geol. Survey Bull. 500, p. 43,1912.
ANTHEACITE KIDGE DISTRICT 19

ridge, especially if this coal zone happens to be faulted downward in 

addition to having been disturbed by marginal igneous intrusions. 

There is ample physiographic suggestion of marginal faulting along 

the base of Anthracite Ridge, as was first noted by Martin 12 and 

indicated by the writers in structure section A-A', The amount of 

displacement has not been determined, but it is possibly several 

hundred to a thousand feet.

CLASSIFICATION

The coals found throughout the world are not susceptible of rigid 

classification, for the characteristics of the several kinds vary with 

their physical as well as their chemical properties, and coals that; are 

chemically similar may differ so much in their physical characters 

that they are not suitable for the same commercial uses. In general, 

the percentage of carbon is a fair indication of the class of coal; but

the fuel ratio (percentage of fixed carbon divided by the percentage of 

volatile matter) is more satisfactory for comparison of different coals 

and is used by Campbell and others. In this method of classification 

Campbell 13 says that the term "rank" is

used to designate those differences in coal that are due to the progressive change 

from lignite to anthracite, a change marked by the loss of moisture, of oxygen, 

and of volatile matter. This change is generally accompanied by an in'crease of 

fixed carbon, of sulphur, and probably of ash. When, however, one-coal is distinguished from another by the amount of ash or sulphur it contains, this difference is said to be one of grade. Thus "a high-grade coal" means merely one that 

is relatively pure, whereas "a high-rank coal" means one that is high in the 

scale of coals, or, in other words, one that has suffered devolatilization and that 

now contains a smaller percentage of volatile matter, oxygen, and moisture than 

it contained before the change occurred.

The several classes of coal have in general the following characteristics : u

Anthracite is a hard, bright, submetallic iron-black coal breaking 

with a conchoidal fracture and having a fuel ratio between about 60 

and 10, percentage of fixed carbon about 85 to 95, and specific-,gravity 

1.3 to 1.8. It ignites slowly, burns with little flame and smoke, and 

does not soften or swell on burning. Most of the known anthracite 

beds are in eastern Pennsylvania. Its peculiar quality has there 

been produced by regional metamorphism. Small areas of anthracite are found in other localities, but usually these are coals that have 

been converted to anthracite by the heat from some molten mass of 

igneous rock that has been intruded into the coal-bearing formation. 

Anthracite has been thus formed from low-rank bituminous coal in 

the Yampa coal field, in northwestern Colorado, and in the Cerrillos

" Martin, O. C., A reconnaissance of the Matanuska coal field, Alaska, in 1905: U.S. Oeol. Survey 

Bull. 289, p. 18, 1906.

" Campbell, M. R., The coal fields of the United States, General introduction: U.S. Oeol. Survey Prof. 

Paper 100A, p. 3,1917; also published as ch. 1 of vol. 1, American fuels, by Bacon and Hamor, 1922.

' Idem, pp. 5-8. Cosgrove, J. F., Coal, its economical and smokeless combustion, ch. l and 2,1916.
20 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

field, in New Mexico. Laboratory experiments indicate that this is 

accomplished at temperatures of 160° to 350° C. (320° to 662° F.), 15 

which is considerably below the temperature of iron at a dull-red heat.

Semianthracite is a hard coal, though not as hard as anthracite, 

having a fuel ratio between about 10 and 6. The lower limit is not 

very definite, for some "hard" coals have a fuel ratio as low as 6, 

whereas some "soft" coals have a fuel ratio as high as 7. The percentage of fixed carbon is about 84. Semianthracite contains more 

gas, kindles more readily, and burns more freely than anthracite 

and makes a hot fire.

Semibituminous coal has a fuel ratio between 7 and 3. It has a 

relatively high percentage of fixed carbon, about 65 to 84. It ignites 

easily and burns freely and rapidly, giving intense heat with little 

smoke. It is considered the best kind of coal for use under steam 

boilers because of its quick and intense heat production.

Bituminous coals are of many varieties, but all have a maximum 

fuel ratio of about 3. The percentage of fixed carbon ranges from 

about 42 to 64. The relatively large amount of volatile matter may 

consist of gases, oils, and tars, as well as the usual organic matter; and 

these coals burn with yellow smoky flame. Many of the bituminous 

coals will coke. These are rich in hydrocarbons and are valuable for 

gas making. When heated they swell and fuse to a spongy mass 

overlying the fire. The noncoking coals do not melt; they hold their 

shape and burn freely.

- Subbituminous coals are somewhat lower in fixed carbon than 

bituminous but may usually be best distinguished by their physical 

properties. On exposure to air subbituminous coal loses moisture 

and develops shrinkage cracks that cause it to break down or "slack" 

when subjected to alternate wetting and drying. Good bituminous 

coal will not thus break down, though owing to inherent fracturing, 

it may disintegrate into fine pieces. In the coals of bituminous rank 

each coal fragment remains fresh and unaltered for months or years, 

whereas the subbituminous coals undergo chemical as well as physical 

disintegration or breaking down.

Lignites, the coals of lowest rank, are readily distinguished from the 

subbituminous varieties, as they are brown and show either distinct 

woody or uniform claylike texture. Chemically the lignites contain 

a much greater percentage of moisture (20 to 40 percent) than the 

subbituminous coals. This reduces their heating value and usually 

prevents their extensive shipment, both because of the freight charges 

on the large amount of contained water and the fact that as much 

of this is rapidly lost on exposure to the air the lignites easily slack 

that is, break down into a powder and are susceptible to spontaneous 

ignition.

u McFarlane, G. 0., Igneous metamorphism of coal beds: Econ. Geology, vol. 24, no. 1, p. 10,1929.
ANTHRACITE RIDGE DISTRICT 21 

CHEMICAL DETERMINATIONS

The standard chemical analysis of coal determines the percentage 

of moisture, volatile matter, fixed carbon, and ash. These are usually 

figured in three ways for the sample as received, for the sample air 

dried, and for the sample calculated on a moisture-free basis. However, inasmuch as the higher-rank coals as purchased contain nearly 

the same amount of moisture, tightly held in their pores, that they 

contain when mined, it is becoming common to consider the figures 

based on the moisture condition of the sample as received most 

representative of the coal. Lignites and low-rank bituminous coals 

absorb moisture on exposure for several months and slack. The 

volatile matter of coal consists of gases and tarry substances as well 

as the usual decayed vegetable material. The ash consists of earthy 

matter and other mineral impurities that will not burn. It is usually

a mixture of silicates, oxides, and sulphates. The fusing temperature 

of the ash is sometimes determined, as it may be of value in judging 

the kind of clinker the coal will make. Ash that fuses above 2,700° F. 

rarely gives trouble, but ash that melts at a lower temperature may 

produce clinkers that will clog the grate. Hard clinker is formed by 

the melting of the ash itself, or some of its constituents. It hardens 

while in the ash or on the grates on cooling. It is formed by the combination of silica with fusible constituents of the ash. The percentage 

of sulphur is sometimes determined, as this substance has injurious 

effects on grates and flues. The Alaskan coals in general have low 

sulphur content, less than 1 percent, and no trouble from this substance has been experienced in their use.

CHARACTERISTICS

Such attempts as were made to burn fragments of the hard coals 

in the camp stoves were only partly successful, owing probably to 

the lack of suitable grates. A small amount of red ash similar to 

that obtained in burning red-ash Pennsylvania anthracite was observed, and it was inferred that under proper draft and grate conditions these coals are adaptable to the same uses as similar grades 

of anthracite. However, no thorough burning tests of coals from 

Anthracite Ridge were made during 1931.

ANALYSES,

The analyses of the samples collected during geologic study in the 

summer of 1931 are given in the following table:
Analyses of coals from Anthracite Ridge a

[By Maurice L. Sharp, chemist, U.S. Bureau of Mines, Anchorage, Al

No. 

on 

map

l 

4 

8 

9 

10

11 

13

14

22 

28

37 

51 

54 

62

Locality

T. ZO N., R. 7 E. 

Sec. 3 _ ____ __ ........

Sec. 12.........................

 .do.. -. . ....

 ..do. -

..-.-do--.-..---.-..-....-....

-.-.-do-.---..-.-.-.--...-......

 .do 

T. SO N., R. 8 E.

Sec. 16 

Sec. 17 __ .... _ .. _ ........

Sec. 22.. .

Analysis 

no.

4488 

4484 

4480 

4490 

4487 

4390 

4388 

4389 

4444 

4486 

4485 

4443 

4445 

4446 

4391 

4481 

4479

4483 

4489 

4466 

4482

Coal as received

Moisture

2.2 

7.2 

4.9 

4.5 

8.7 

6.1 

5.0 

6.3 

7.2 

3.1 

5.0 

3.5 

4.1 

5.0 

7.5 

6.8 

4.0

4.0 

3.6 

3.9 

4.7

Volatile 

matter

16.0 

26.3 

8.1 

9.4 

8.9 

8.6 

9.4 

8.4 

9.1 

9.3 

14.4 

10.5 

9.6 

10.0 

8.5 

29.9 

19.9

29.2 

22.9 

31.5 

27.6

Fixed 

carbon

78.0 

57.7 

71.8 

70.9 

69.0 

64.3 

59.0 

75.4 

75.4 

80.6 

71.5 

67.2 

71.0 

65.3 

72.6 

54.1 

73.7

44.2 

63.9 

47.4 

52.8

Ash

3.8 

 8.8 

"15.2 

, 15. 2 

13.4 

21.0 

26.6 

"10.9 

8.3 

-7.0 

9.1 

18.8 

15.3 

19.7 

0 11.4 

9.2 

2.4

22.6 

9.6 

17.2 

14.9

Sulphur

0.6 

.7 

.7 

.3 

.5 

.5 

.5 

.5 

.2 

.7 

.7 

.2 

.5 

.5 

.5 

.6 

.7

.6 

.5 

.6 

.6

Calo

Calori

7,8

6,4

6,4

6,5

6,1

5,9

5,4

6,5

6,9

7,4

7,0

6,2

6,5

6,0

6,5

6,3

7,6

5,6

7,1

6,2

6,3

1 Determinations of softening temperatures of the ash by EC. M. Cooper, chief chemist of U.S. Bureau o

Analysis

no.

4480

4486

Bureau

of Mines

laboratory

no.

76522

76523

Softening

temperature

(°F.)

2,785

2,445

Analysis

no.

4389

4391

Bureau

of Mines

laboratory

no.

76520

76521

' Apparent specific gravity, determined on lump samples. Specific gravity of the other samples determ
ANTHRACITE RIDGE DISTRICT 23

Local metamorphism lias produced coal of higher rank in places, 

as shown by the semibituminous coal in sec. 3, T. 20 N., R. 7 E. 

(analysis 4488), and sec. 26, T. 20 N., R. 7 E. (analysis 4479). In 

each of these places this alteration to a higher-rank coal seems to be 

due to Othe effect of adjacent diabase sills. In other coal beds near 

but perhaps not so closely adjacent to sills the coal has been practically 

unaffected. This is shown by analyses 4481, 4466, and 4489 of coals 

in sec. 23, T. 20 N., R. 7 E.; and sees. 17 and 16, T. 20 N., R. 8 E.

In the first two localities the coal lies about 50 feet above diabase 

sills. In the third the coal is about 230 feet below a 75-foot diabase 

sill, evidently too far away to be appreciably affected. However, in 

this locality there are several lenses of coal a few inches thick and 

less than 50 feet beneath the diabase, that have been in part altered 

to hard, shiny coal, probably of semianthracite rank. That appreciable alteration has not been everywhere caused by the close folding 

that has taken place along the north side of the basin is indicated 

by analysis 4483, of coal from the sharply folded bed in sec. 9, T. 20 

N., R. 8 E., the fuel ratio of which is only 1.5.

The highest-rank coals found in the district are all confined to the 

SKNWK sec. 12, T. 20 N., R. 1 E., in an area that is intensely folded 

and faulted and intruded by masses of diabase. The combined effect 

of the heat of the intrusive rock and the heat and pressure produced 

by the deformation of the rocks may account for the higher rank of 

the coals in this small area. As shown by the analyses of 13 samples 

from this area, the coals are classed as semianthracite or low-rank 

anthracite.

The thickest outcrop of coal is that in the SE^SEKNWK sec. 12, 

T. 20 N., R. 7 E., where 34 feet of coal was measured, divided into 

three beds by partings. Four samples of this coal, each embracing 

about 8 feet of successive portions of the bed, showed on analysis 

fuel ratios ranging from 6.4 to 8.5. The earliest analysis of coal from 

this outcrop showed volatile matter 7.08, fixed carbon 84.32, and fuel 

ratio 11.91; 16 recalculated to volatile matter 7.75, fixed carbon 92.25, 

and fuel ratio 11.90. 17 A reanalysis of material from the sample, 

made several months later, showed volatile matter 5.26 and fixed 

carbon 86.15,18 giving a fuel ratio of 16.4, owing to the loss of an 

appreciable amount of the volatile matter during the several months 

intervening between the analyses and to somewhat different methods 

of analysis used. 19

u Martin, G. C., Preliminary statement on the Matanuska coal field: U.S. Qeol. Survey Bull. 284, 

pp. 27,97, 98,1906; A. reconnaissance of the Matanuska coal field. AJaska, in 1905: U.S. Geol. Survey Bull. 

289, p. 30,1906.

" Faige, Sidney, and Knopf, A.dolpn, Geologic reconnaissance in the Matanuska and Talkeetna Basins, 

Alaska: U.S. Geol. Survey Bull. 327, p. 60,1907.

« Martin, G. C., and Mertie, J. B. Jr., Mineral resources of the upper Matanuska and Nelchina Valleys: 

U.S. Geol. Survey Bull. 592, p. 295,1914.

» See U.S. Geol. Survey Bull. 290, pp. 29-30,1906.
INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

The following two other analyses of coal from the vicinity of the 

thick bed have been made, though they may not represent coal from 

the principal outcrop.20

Analyses of coal from Purinton Creek 

[By the U.S. Bureau of Mines]

Analysis no.

A3639. .._. ..............__._._.__ .. .

A3640................................................

As reMoisture

3.2

4.7

Volatile 

matter

8.1

9.2

Air dried

Fixed 

carbon

85.8

81.4

Ash

4.2

6.3

Fuel ratio

10.6

8.9

The next thickest outcrop is about 1,000 feet to the northwest, in 

the NE%SE%NW% sec. 12, where 24 feet of clean coal was measured. 

The analyses of samples from the upper portion of this bed show 

fuel ratios of 8.3 and 8.7, but the lowest bench of the bed ran unexpectedly high in volatile matter (14.4) with lower fixed carbon (71.5), 

giving a fuel ratio of only 5.0.

The analysis showing the highest fuel ratio (8.9) was made on a 

sample taken directly under a 5-inch diabase sill from the outcrop of 

one of the benches of probably the same bed from which the samples for 

the preceding two analyses came, in the center of the NE%SE%NW% 

sec. 12. The fixed carbon (71.8) was not so high in this coal, 

however, as in the middle sample from the 24-foot bed, nor as in 

the coal from the westernmost pit, probably on the same bed, in the 

SE^NWMSWK sec. 3, T. 20'N., R. 7 E., which showed 78.0 per cent 

of fixed carbon; but this sample contained 16.0 per cent of volatile 

Jnatter, giving it a fuel ratio of only 4.9.

The analyses of the samples collected in 1931 from the thick bed 

of sec. 12 show that the coal is inferior in both fuel ratio and ash 

to the earlier samples. Although the differences observed may be 

due in part to changed methods of analysis, they seem to indicate 

that long exposure to the atmosphere resulted in a loss of volatile 

matter hi the earlier samples taken directly at the outcrop instead of 

from pits, and the possible inclusion of more bone in the 1931 samples 

may account for the higher percentage of ash.

Too great importance should not be given to these analyses of 

single samples, for the coals may easily vary appreciably within 

short distances along the beds. Actual burning tests on amounts of 

several hundred pounds would offer a sounder basis of comparing the 

relative fuel values of the coals from several localities.

The presence of low-rank coals in the Moose Creek, Eska, and 

Chickaloon districts, in the western part of the Matanuska VaUey,

*> Capps, S. R., Geology of the upper Matanuska Valley, Alaska: U.S. Qeol. Survey Bull. 791, p. 84, 

1927.
ANTHRACITE RIDGE DISTRICT 25

and of the higher-rank coal in the Anthracite Ridge district, in the 

eastern part of the valley, early suggested that there might be a 

progressive alteration of the coal eastward, produced by the intense 

folding and faulting along the north side of the valley. The more 

recent studies do not confirm this supposition, however, as the 

average-rank coals at Chickaloon have a fuel ratio of 3.5 and the 

easternmost outcrops that were sampled in the Anthracite Ridge 

district have fuel ratios as low as 1.5, 1.9, and 2.7.

QUANTITY

In the absence of development work, few reliable data are at hand 

for estimating the coal reserves of the district. In the S^NW^ 

sec. 12, T. 20 N., R. 7 E., the thicknesses of coal exposed in the several 

pits indicate that within the small area bounded on the south by a 

fault and on the north by the upturned edges of the coal-bearing 

beds there may be about 750,000 tons of low-rank anthracite. This 

estimate is based on an irregular area of 20 acres, with an estimated 

average thickness of possibly workable coal running 19.3 cubic feet 

to the ton. This tonnage is not sufficient to justify commercial 

operation. Sufficient data are not available for estimating the amount 

of coal present in other parts of the district, but it is possible that 

reliable data can be obtained by core drilling in the more gently 

folded area immediately south of the outcrops of thick beds of highrank coal.

POSSIBILITY OF UNDISCOVERED DEPOSITS

In the southern and eastern parts of the district the coal outcrops 

prospected in 1931 were all of lower rank than most of the coal found 

in sec. 12, T. 20 N., R. 7 E., and some of these coals, even where 

3 to 7 feet in thickness, change laterally into coaly shales within 

short distances. However, fragments of hard shiny coal with metallic 

luster were seen scattered throughout the basin. In one place a bed 

of coal of this type over 1 foot thick was found on the south side 

of the basin (locality 28), in sec. 26, T. 20 N., R. 7 E. The coal of 

this bed closely resembled a semianthracite in color, hardness, and luster, but analysis showed it to be semibituminous. Possibly if it could 

be traced around the margin of the basin it would be found to represent one of the beds in the zone of thicker higher-rank coals which 

now seem to be limited in distribution to the north side, and the 

variation in thickness and quality would change proportionally to 

the distance from the north measurement of 34 feet and the south 

measurement of 1.5 feet, or midway the coal would have a thickness 

of about 17 feet, which might be considered the average for the area. 

Sufficient evidence that these coal beds persist across the area and 

that such an average thickness will be found is not now available,
26 INVESTIGATIONS IN ALASKA RAILROAD BELT, 1931

but a bed of that thickness would require an areal extent of only half 

a square mile to contain sufficient tonnage to provide a mine of 1,000- 

ton daily capacity enough coal to operate for a period of over 35 years, 

which would afford this branch of the Alaska Railroad a sustaining 

source of revenue.

TRANSPORTATION AND MARKETS

In 1931 there was no improved route of transportation between the 

Anthracite Ridge district and the railhead at Chickaloon, except 

the trail. Commercial development of the coal resources would 

necessitate suitable means of transportation, presumably by tramway 

or by extension of the railroad from Chickaloon. Further exploration should precede any attempt to open mines, in order to determine 

whether the available deposits are sufficiently great and the quality 

of the coal sufficiently high to justify such rail construction. The 

commercial possibilities lie chiefly in the production of a coal of 

higher rank than the bituminous coals of the lower Matanuska 

Valley and the lignite of the Nenana River Valley.

CONCLUSION

The field work of the summer of 1931 demonstrated that surface 

exploration alone is not adequate to prove the presence of workable 

bodies of anthracite in the Anthracite Ridge district. It did, however, suffice to show that such high-rank coal as is or may be present 

in the area is of somewhat lower rank than was anticipated namely, 

semianthracite but is of superior rank to the coals mined in the 

lower Matanuska Valley and other areas tributary to the Alaska 

Railroad.

Inasmuch as only a small area of semianthracite of the exceptional 

thickness found on the south flank of Anthracite Ridge would be 

required for the development of a commercial tonnage, it was regarded 

advisable to prospect intensively during the summer of 1932 the synclinal area adjoining the south flank of the ridge by drilling a series 

of core holes to indicate definitely the depth, thickness, quality, and 

distribution of such coal beds as may exist in a square mile of the 

most promising portion of the area.

The discovery of a thick bed of semianthracite in one or more of 

the four to six holes planned for the area, within less than 2,000 feet 

of the surface, will tend to confirm commercial possibilities unless 

water is encountered in such quantities that it can not be handled 

without undue expense a contingent condition which is regarded 

as extremely remote.

Proposals and specifications were prepared by the Geological Survey for this drilling to be done by contract, under the supervision 

of the Alaska 'Railroad, and approved by the Secretary of the Inte-
ANTHRACITE RIDGE DISTRICT 27

rior December 9, 1931. Bids were opened at the Department of 

the Interior January 15, 1932, and a contract was entered into requiring the drilling of 8,000 feet prior to December 31, 1932. Equipment 

and drillers arrived in the area during March 1932, and drilling was 

started under the terms of the contract.

G. A. Waring, geologist, assisted by P. A. Davison, junior geologist, 

was detailed to the field as representative of the Geological Survey 

and placed in complete field charge of the Government's interest in 

the project. He will receive the cores, record measurements, and 

make any modifications of plans required to meet any contingencies 

which may arise. After the drilling is completed a more detailed 

report on the area will be prepared and published.

o