AFRO 

GEOLOGICAL SURVEY CIRCULAR 146 

November 1951 

REVIEW OF THE GEOLOGY AND COAL RESOURCES 

OF THE BERING RIVER COAL FIELD, ALASKA 

By 

F. F. Barnes 

P-ERMAFROST 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

Washington, D. C. 
A REVIEW OF THE GEOLOGY AND COAL RESOURCES 

OF THE BERING RIVER COAL FIELD, ALASKA 

CONTENTS 

Page 

Introduction .••..••••.•.•.....•.••.••.• o o • 1 

Location and extent . • . • • • . . • • • • . • • • . . • . . 1 

History of investigations • • • • • • • • • • • . • • • • 1 

Purpo~e and scope of present report...... 4 

Stratigraphy. • . • • . . • . . . • • . • • . • . • • • . • • • • • . . 4 

Igneous rocks............................ 5 

Structure • . • • • . • • • • • • • . • • . • . • . . • • . • . . • • • • 5 

Coal • • • • • • . • • • • • . • . . • • • • • • • • • • • • • • • • . • . • 6 

Areal extent • • • • • . • • • . • • . • • • . • • . • . . • . • • 6 

Stratigraphic position...... • • . • • • • • • • • . . 6 

Page 

Physical and chemical properties......... 7 

Prospective mining conditions............ 7 

Topographic position of the coal... . • • • • 7 

Attitude of the coal . . • . • • • • • • • . • • • • . • • 8 

Persistence of the coal.............. • • 8 

Presence of water and gas............. 9 

Physical condition of the coal • . • • . • • • • • 9 

Conclusions • • • • • • • • • • • • • • • • . • • • • • • • • • • . • 11 

Reference cited • • • • • • • • • • • • • • • • • . • • • . . • • . 11 

ILLUSTRATIONS 

Page 

Figure 1. Sketch map of the Bering River coal field, Alaska, 

showing public land surveys • . • • . • • . • • • • • • • • • • • • • • • • • • • • . • • .• • • • • • • • • • • • . • • • • • • • • 2 

2. Sketch map of the Bering River coal field, Alaska........... • • • • • • • • • • • • . • . • • . • • • • • 3 

INTRODUCTION 

Location and extent 

The Bering River coal field is in south-central 

Alaska, about 50 miles southeast of Cordova and 

12 miles northeast of the coastal village of 

Katalla. It lies between latitudes 60°15 1 and 

60°30 1 N., and longitudes 143°45 1 and 144°20' W. 

(fig. 1). Known coal-bearing rocks are exposed 

in a belt roughly 21 miles long and 2 to 5 miles 

wide trending northeast from the east shore of 

Bering Lake. (See figs. 1 and 2.) 

History of investigations 

The Bering River coal field was discovered in 

1896, and practically all of it was covered by 

coal claims entered under the law of 1904 (Fisher, 

1912, p. 12). 

The first extensive study of the area was made 

by the U. S. Geological Survey in 1905 and 1906, 

when the known coal-bearing area was mapped 

topographically and geGlogically, and many coal 

beds were measured and sampled (Martin, 1908). 

In 1907 Storrs (1910, pp. 2326-2345) made an. 

engineering study of the Cunningham group of coal 

claims in the basins of Trout and Clear Creeks. 

His report includes a large number of coal analyses, brief descriptions of numerous coal exposures, proposed plans for development, and estimates of mining and development costs. In 1909 

brief examinations of the Cunningham property 

were made for the General Land Office by Kennedy 

(1910, pp. 1039-1040) and for the Forest Service 

by Wingate (1910, p. 1043), for the purpose of 

determining whether the area should be classified 

as coal or noncoal land. As these two engineers 

did not agree, C. A. Fisher, a mining geologist 

of the U. S. Geological Survey, was sent to the 

area in the same year and made a detailed examination of the property (Fisher, 1910, pp. 1073-

1092), in the course of which he opened and 

·measured 201 coal prospects. As a result of this 

study he classified all 33 claims of the Cunningham group as coal land, the basis of such classification being the observed or inferred presence 

of a coal bed of workable thickness within 3, 000 

feet of the surface. 

- 1 -
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Figure 1. --Sketch map of the Bering River coal field, Alaska, showing public land surveys. 
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Figure 2. --Sketch map of the Bering River coal field, Alaska. 

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In 1912 a general examinatio·n of the most 

promising parts of the entire Bering River coal 

field was made by C. A. Fisher, W. R. Calvert, 

R. Y. Williams, and S. S. Smith, mining geologists and engineers, to determine the best 

localities from which samples could be taken for 

testing by the U. S. Navy. The geology of the 

field and its relations to coal mining were summarized by Fisher and Calvert (1914, pp. 29-50), 

and the mining conditions encountered in obtaining the sample were described by Williams 

(1914, pp. 12-28). The Navy sample, totaling 

about 600 tons, was obtained from four tunnels 

on Trout Creek. 

Coal beds in various parts of the field were 

measured and sampled by J. A. Holmes in 1911, 

W. A. Selvig in 1912, G. W. Evans in 1915, and 

Capt. W. P. T. Hill in 1920, 1921, and 1922. 

(Cooper, 1946, pp. 104-107.) 

In 1920 a detailed report on the property of the 

Bering River Coal Company on Carbon Creek 

was prepared by G. W. Evans (1920}. This report summarizes existing and proposed developments, lists detailed information on many coal 

exposures, and gives the results of coking and 

washing tests. 

Purpose and scope of pre sent report 

This report is an attempt to review and integrate the results of several examinations of the 

Bering River coal field, including some that 

have been published only in Congressional Hearings and probably are not widely known, and to 

evaluate these results insofar as possible in the 

light of present conditions. No new field studies 

have been made by the writer. The purpose of 

the present report is to make more readily 

available the considerable amount of information 

already in existence on an area that continues to 

attract considerable interest as a possible source 

of both anthracite and coking coal. 

STRATIGRAPHY 

The general succession of rocks in the region 

including the Bering River coal field, according 

to Martin ( 1908, p. 24}, is as shown in the following table: 

General section of rocks in the Controller Bay region 

Age Formation Character of rocks Thiclaless 

(feet) 

Quaternary Stream deposits, lake sediments, 

morainal deposits, marine silt 

and clay 

Tertiary or later Diabase and basalt dikes 

Tolrun Sandstone 500 

Shale 2,000+ 

Kush taka Arkose with many coal beds 2,soo! 

Tertiary Stillwater Shale and sandstone 1,ooo! 

Conglomerates, sandstones, and 

shales 2,500 

Sandstone 500 

Katalla1 Shale, concretionary 2,000 

Sandstone 1,000 

Shale SOOt 

Pre-Tertiary Graywacke, slates, and igneous 

rocks 

1The position of the Katalla formation with reference to the other Tertiary formations is not definitely established. (See following discussion.) 

- 4 -
The Stillwater formation was described by 

Martin ( 1908, p. 30) as consisting of shale 

and sandstone without known characteristic 

beds. The base of the formation was not . 

recognized. 

The Kushtaka formation, according to 

Martin (1908, p. 31): "* * * consists predominantly of coarse arkose, although some sandstone and much shale are present. It contains 

a large but unknown number of coal beds. 

Marine conditions are not known to be represented. 

"The thickness exceeds 2, 000 feet, the 

exact total not being known. '

1 

A generalized-section of the coal-bearing 

strata given by Fisher (1910, p. 1077) has 

a total thickness of about 3, 500 feet. 

In discussing stratigraphic relations 

Martin (1908, p. 31) stated that: 

"The Kushtaka formation overlies the Stillwater formation, probably conformably, although as the contacts are in many places 

faults the exact relations are none too well 

known." In the same report (p. 37) Martin 

admits the possibility that the sandstone and 

shale at the base of the Katalla formation 

may be equivalent to the Tokun formation, 

which would place the Katalla stratigraphically above the Kushtaka formation. Later work 

in adjoining areas by D. J. Miller (Manuscript in preparation) indicates that the lower 

part of the Katalla formation is equivalent 

to the upper part of the Tokun. Furthermore, 

according to a personal communication from 

D. J. Miller, re-examination of fossils collected by Martin from areas mapped as Stillwater has raised the possibility that the Stillwater formation may represent a part of the 

Katalla formation, in which case it also would 

be .7otratigraphically above the Kushtaka formation. 

The Tokun formation was described by 

Martin (1908, pp. 35-36) as follows: 

"These beds overlie the Kushtaka formation conformably, the transition apparently 

representing a change from fresh-water to 

marine conditions. The formation is at least 

2, 500 feet thick, the lower 2, 000 feet consisting chiefly of sandy shales * * *· The 

shales * * * are overlain by a bed of sandstone several hundred (possibly 500) feet 

thick. This sandstone is well exposed in the 

hills northeast of Lake Tokun and west of 

Lake Charlotte. The beds overlying this 

sandstone contain some shale, but are not 

well exposed." 

IGNEOUS ROCKS 

According to Martin (1908, p. 41), small 

basic dikes and sills are very abundant in the 

Tertiary rocks, north and east of Stillwater 

Creek. Most of them are less than 1 or 2 feet 

thick, and none could be traced more than a 

short distance. Although basalt is the predominant rock, sills at three localities were described as diabase. These include: three sills, 

interlayered ' with coke and ranging in thickness 

from l. to 8 feet, at the south end of Carbon 

Mountain; a sill of unspecified thickness at the 

base of the falls near the head of Clear Creek, 

which has coked the upper 12 inches of a 17 -foot 

coal bed; and a 4-foot sill underlying a 4-foot 

coal bed on the east bank of Clear Creek about 3 

miles above its mouth. Other basic dikes are 

shown on Martin's geologic map at several points 

on the east slope of Carbon Mountain. 

STRUCTURE 

The structure of the rocks of the Bering River 

coal field, particularly as reflected in the physical condition of the coal seams, is by far the 

.most important factor bearing on the potential 

economic value of the coal deposits. Thickness 

measurements and analyses of many samples 

of coal from all parts of the field leave no doubt 

that the area contains a large amount of both anthracite and coking coal of excellent quality in 

beds that are at least locally of minable thickness. The actual value of these deposits is dependent on their being minable in sufficient 

quantity and at low enough cost to warrant their 

exploitation. 

The principal structural features of the region 

were outlined by Martin ( 1908, pp. 42-43) as 

follows: 

"The pre-Quaternary rocks of this region have 

a general northeast strike; have steep dips, which 

are· northwestward throughout the greater part 

of the region; and are faulted. The northeast 

strike and northwest dip are the dominant structural features of the region. The strike varies 

from the northeast most markedly between 

Kushtaka Lake and Berg Lakes, where it is east 

and west, and at points in and .north of the valley 

of Burls Creek, where it is northwest. 

"Monoclinal northwest dip holds throughout the 

greater part of the region east of Kush taka Glacier 

and Kushtaka Lake. In the northeast part of this 

region the structure is not as simple as the uniform strike and monoclinal dip seem to indicate. 

The folds are in part overturned, in places complexly so, and a complicated system of overthrust faults * * * adds to the coml'-':l~xity of the 

structure, which gradually increase!l from southwest to northeast. 

"The structure between Kushtaka Lake and 

Shepherd Creek is somewhat more simple than 

in the· eastern district described above. In the 

greater part of this region the folds are open, 

and strike northeast, and the dip northwest, although southeast dips occur in several areas and 

there is considerable variation in strike along 

the valley of Shepherd Creek. * * * At least four 

faults traverse this area. An overthrust near 

the crest of the southern end of Kushtaka Ridge 

has cut out the Kushtaka formation and brought 

the Tokun and Stillwater formations in contact 

with each other. Another fault of somewhat un-

~ertain character extends along the western side 

• 5 • 
of and about half way down Kushtaka Ridge. Along 

the eastern side of the valley of Shepherd Creek, 

froll} a point near the northern end of Lake 

Charlotte to 1 t miles below the lake, two 

faults bound a block of southeastward-dipping 

Kushtaka formation between northwestwardqipping rocks of the Tokun formation. An anticline has its axis on Carbon Creek, and 

another, which is probably a prong of the former, on Queen Creek. Between these a synclinal mass 

of the Tokun formation lies transversely across 

the crest of Kushtaka Ridge." 

Martin measured a large number of coal exposures in all parts of the field, for most of which 

he gave the attitude of the bedding. Although dips 

were recorded in all four quadrants, they were 

preponderantly to the northwest, at angles ranging 

from zoo to 80o and averaging about 400. At only 

one point, at elevation 1, 450 feet on Barrett Creek 

(see fig. 2), did he mention a fault cutting the 

coal. At two other points, on the east bank of 

Canyon Creek 2 miles above its mouth, and in a 

tunnel on the west side of Kushtaka Lake, he 

mentioned coal beds pinching out, but did not state 

whether as a result of faulting or of stratigraphic 

thinning. 

The foregoing description of the structure by 

Martin agrees generally with the findings of later 

investigators, who confined their studies largely 

to the basins of Clear, Trout, and Carbon Creeks, 

where they found the structure to be characterized 

by moderate to steep northwest dips, varied in a· 

few places by tight folds, generally of unknown 

extent. 

In addition to the four major faults shown on 

Martin's map (1908, pl. 8), Fisher and Calvert 

( 1914, p. 34) reported: 11 * * * faults of lesser 

dimensions are exceedingly numerous, some 

representing a stratigraphic displacement of 

several hundred feet. 

"Every tunnel of any consequence encounters 

one or more of these lesser breaks. In the northeastern part of the field the Davis mine has struck 

at least six of these faults in 500 feet of entry. 

The McDonald mine at the opposite end of the 

field near Bering Lake discloses similar conditions, and the prospect tunnels in the intervening area encountered the same difficulty." 

They referred specifically to two faults--one a 

strike fault below the falls on the middle fork of 

Barrett Creek, which they inferred to have 

considerable displacement 11 as it appears to cut 

practically the entire middle group of coals, 11 

and the other a transverse fault that trends up 

the valley of Trout Creek. The Trout Creek fault 

was inferred from the fact, revealed during intensive prospecting by the Navy expedition, that 

several thick coal beds exposed on the west side 

of the creek were not present on the projection of 

their strikes east of the creek. A discrepancy 

• in the attitude of the strata- -almost flat strata 

on the east side of the creek opposite steeply 

dipping strata on the .west side- -also suggested 

major faulting. After examining many tunnels and 

outcrops Fisher and Calvert ( 1914, pp. 34- 35) 

concluded that "* * * every part of the field, except possibly the ridge lying between Trout Creek 

and Kushtaka Glacier, is traversed by an intricate system of fault lines, making underground 

development everywhere tedious and costly and 

in many places almost, if not quite, impracticable, 

except where the extraction of only a limited· 

amount of coal is contemplated." 

Storrs (1910, p. 2340) noted a zone of intense 

faulting on Barrett Creek and expressed the 

belief that "* * * the region to the northwest 

was raised very greatly relative to the region 

to the southeast, and the lower coal seams in 

the northwestern sections are, in my judgment, 

the same seams as those to the southeast." 

Fisher and Calvert (1914, p. 34), also noted 

a strike fault of considerable displacement on 

Barrett Creek but concluded (p. 36) that no 

duplication of coal beds had been produced by 

faulting in this area. 

Probably more important than the major folding and faulting, in effecting the quality of the 

coal, have been the shearing, crushing, and 

repeated small-scale faulting that characterize 

most of the known coal exposures in the field. 

Steep dips and fold axes may determine the 

method of mining to be used, and major faults 

may limit the extent of mining from a given 

entry, but the small-scale features, such as 

shearing and crushing, may so adversely affect the quality of the coal and the cost of 

mining as to preclude successful development. 

These features are discussed in detail under 

"Prospective mining conditions". 

COAL 

Areal extent 

The area underlain by the coal-bearing 

Kushtaka formation was estimated by Martin 

(1908, p. 65) to be about 50 square miles, of 

which roughly the eastern half contained mainly 

anthracite and the western half mainly semibituminous coal. Martin also es.timated that an 

additional 20 square miles may be underlain by 

coal "at a greater or less depth" beneath the 

overlapping Tokun formation. The principal 

coal-bearing areas lie in'~ belt extending northeastward from Bering Lake. and include the ridge 

culminating in Mt. Hamilton; the valley of Carbon 

Creek and the east slope of Kushtaka Ridge; and 

the upper drainage basins of Trout, Clear, and 

Canyon Creeks; and Carbon Mountain. (See fig. 

2~ 

Stratigraphic position 

According to Martin (1908, p. 66), the coal 

beds of the Bering River field are distributed 

thr"oughout the entire thickness of the Kushtaka 

formation and are also restricted to it, the overlying Tokun and underlying {?) Stillwater formations being entirely barren. Fisher ( 1910, pp. 

1076, 1088-1 089) on the other hand, found several coal beds in areas supposedly underlain by 

the Stillwater formation, and therefore concluded 

that at least the upper part of the Stillwater was 

also coal-bearing. It is possible either that 

Fisher found coal undetected by Martin within 

the Stillwater formation, or that the formational 

contact as mapped by Martin should be moved 

farther south to include, within the Kushtaka 

formation, the southernmost coal beds found by 

- 6 -
Fisher. In a later report Fisher (Fisher and 

Calvert, 1914, p. 32) expressed the opinion that 

"probably only the Kushtaka is coal-bearing." 

The following conclusions on the stratigraphic 

position of the coal beds in the basins of Trout 

and Clear Creeks were stated by Fisher and 

Calvert (1914, p. 36): 

"The coals are distributed throughout the entire thickness of the Kushtaka, and possibly into 

the upper part of the underlying Stillwater formations. It is believed that more than 20 beds of 

locally workable coal occur within the Kushtaka, 

but owing to the prevailing complexity of structure that exists in this field it is possible that 

some of the beds believed to be distinct are in 

reality duplications. These beds arrange themselves into three rather indefinite groups--a 

lower, a middle, and an upper. 

"The evidence favoring the belief that these 

groups are distinct within themselves and not 

duplications caused by major strike faulting 

consists in the wide variation in stratigraphic 

interval between individual beds in the respective groups, especially when the lower is compared with the middle or the upper; also in the 

difference in the aggregate number of coal beds 

present in each group, even when these groups 

are examined at nearby places across the strike, 

as on Barrett Creek, and further in the absence 

of indications of disturbance of strata such as 

should be present if strike faulting sufficient to 

cause group duplication had taken place. 

"The lower group contains eight beds of coal 

which are moderately thick and generally 100 to 

800 feet apart; the middle group has nine beds 

closely grouped within about 400 feet of strata, 

and the upper group contains five beds of variable dimensions and slightly more widely separated than those of the middle group.'' 

A study of a generalized stratigraphic section given by Fisher in an earlier report(l910, 

p. 1077) shows that the grouping mentioned 

above is indeed ''rather indefin:j.te. '' Of the 22 

coal beds 3 feet or more in thickness, 14 are 

rather evenly distributed through about 900 feet 

of strata near the top of the formation, and the 

remaining 8 beds are widely scattered, either 

singly or in pairs, through 2, 700 feet of under-· 

. lying strata. 

Physical and chemical properties 

Martin ( 1908, pp. 81-92) found that all unweathered samples of coal from the part of the 

field east of Canyon Creek possessed the physical characteristics of anthracite, and that fuel 

ratios based on proximate analyses of coal from 

that part of the field confirmed its classification 

as anthracite. 

The coal of the rest of the field, which Martin 

classified on the basis 'of fuel ratios as semianthracite in the middle district and as semibituminous in the western district (see fig. 2), 

"is all of a friable nat1:1re, the least crushed of 

it somewhat resembling part of the softer bituminous coals of the Eastern States." Storrs 

(1910, p. 2330) noted that the coal of the middle 

district that had not been crushed had a conchoidal fracture. 

For analyses of coals of the Bering River 

field the reader is referred to U. S. Bureau of 

Mines Technical Bulletin 682, which contains 

most of the previously published analyses as well as many previously unpublished analyses of 

coal from all parts of the field (Cooper, 1946, 

pp. 60-68, 101-107). These analyses show the 

coal of the field to range in heating value from 

12, 000 to 15, 000 B. t. u., as received, and in 

rank from anthracite in the eastern part, through 

semianthracite in the middle part, to low-volatile bituminous in the western part. The lowvolatile bituminous coal corresponds to the semibituminous coal described by Martin. 

As a result of field coking tests, Martin(1908, 

p. 82) concluded that practically all the coal of 

the field classed as semibituminous was of good 

coking quality. Storrs ( 1910, p. 2329) and Fisher 

and Calvert (1914, p. 38) concurred in this conclusion. However, the results of tests reported 

by Evans (1920, pp. 18-20) indicate that the 

Carbon Creek coal does not make a satisfactory 

coke in a beehive oven or in byproduct ovens of 

conventional type. 

Tests by the Navy Department (1914, pp. 62-

83) showed that the coal from Trout Creek, even 

after washing to reduce the ash content to a 

comparable figure, had a somewhat lower boiler 

efficiency than run-of-mine Pocahontas coal, 

on which comparative tests were made. Furthermore, it formed a large amount of dense clinker 

on the furnace grates, which made it unsuitable 

for Navy use. 

In cleaning the Bering River sample the ash 

content of the dry coal was reduced from 14. 06 

percent as received to 5. 42 percent. This involved a loss of 49 percent of the fuel as mined. 

Prospective mining conditions 

The following geologic factors were listed by 

Martin ( 1908, pp. 92-93) as affecting the cost of 

mining in this region: topographic position, steep 

dips and complicated structure, variability in 

thickness and possible lack of persistence of 

coal beds, occurrence of explosive gas and 

large amounts of underground water, and the 

friable character of the coal. His comments on 

these factors, supplemented by observations of 

later workers, are summarized in the following 

paragraphs. 

Topographic position of the coal 

Martin (1908, p. 92) pointed out that the region 

is one of considerable relief, that many of the 

coal beds crop out in the bottoms of valleys, and 

that all the beds,. if persistent for a sufficient 

distance, could be reached by tunnels at the 

level of the valley floors. He concluded that shaft 

or slope mining would not be necessary for :many 

years, or until all the coal above the general 

drainage level had been exhausted. 

In discussing proposed developments on Trout 

and Clear Creeks Storrs (1910, pp. Z~3~-2334) 

stated: 

- 7 -
"The ultimate development of the Cunningham 

lands will undoubtedly call for several crosscut 

tunnels, such as proposed by Mr. W. L. Hawkins 

in his report on this property and shown on plate 

IV, from near Sta. 9 on Clear Creek; the others 

probably being one on Trout Creek, one to the 

southeast from some point on Clear Creek south 

of Sta. 299, and two from the Clear Creek Valley, 

one to the northwest and one to the southeast from 

near Sta. 276. At the present time [November 

1907] however, sufficient data as tv the field is 

not available to justify the commencement of any 

of ~ese tunnels with assurance of their being at 

the proper locations. 11 

Storrs further recommended that test slopes 

be sunk from the out-crops of certain prominent 

seams on the west side of Clear Creek valley 

to prove the dip and continuity of the coal before 

the crosscut tunnels were started. Fisher and 

Calvert ( 1914, pp. 40-41) stated that coal seams 

of the upper group that crop out on Moore and 

Barrett Creeks could possibly be reached by a 

water-level tunnel from Clear Creek, but that 

beds of the lower group, e:Xposed on the lower 

courses of Moore and Barrett Creeks and along 

Clear Creek, dip so steeply that the greater 

part of their coal tonnage is below water level. 

Attitude of the coal 

The relations of folding and faulting to mining 

operations were discussed to some extent in this 

report under the heading of "Structure." Martin 

(1908, p. 93) stated that in certain areas of the 

field faults and overturned folds would probably 

prevent the successful mining of the coal, particularly in the structurally complex eastern part 

of the field. Fisher and Calvert gave the faulted 

and disturbed condition of the coal beds as one of 

the objectionable features of the coal in the Clear 

Creek basin (1914, p. 41), mentioned complex 

structure as adversely affecting coal exposures 

at two localities on the east side of Trout Creek 

(1914, p. 48), and concluded that the coal 

examined in the valleys of Carbon Creek and its 

tributaries, Ocean and Leeper Creeks, is in a 

zone of too complex structure to warrant development on a large scale {1914, p. 45). They 

also mentioned (1914, p. 45) two areas where 

conditions seemed to warrant further prospecting. One of these described as a possibly 

undisturbed area that lies in a fault block on the 

east side of Kushtaka Ridge, and the other as an 

apparently unfaulted area on the northwest side 

of Carbon Creek, which is underlain by the upper 

part of the Kushtaka formation and should therefore contain coal. According to Evans (1920, 

pp. C, 70), however, development work on the 

north side of Carbon Creek was not too encouraging, but work on the south side of Carbon Creek 

revealed at least one coal bed that showed promise of being exceptionally persistent, and gave 

reason for believing that a small mine could be 

developed. 

Considerable care should be taken in this region 

in interpreting the attitude of bedding from distant 

views or aerial photographs. Beds exposed along 

the strike may appear to have a uniform monoclinal dip, but when exposed across the strike 

may be found to be compressed into tight overturned folds. 

Persistence of the coal 

Coal exposures in the Bering River field consist 

for the most part of isolated natural outcrops and 

prospect openings along the main stream courses, 

the intervening areas are covered with soil, moss, 

and other vegetation. Few coal beds have been 

traced more than short distances, so that little 

is known of the maximum extent of individual coal 

beds. Martin ( 1908, p. 68) mentioned one anthracite seam on the east side of Carbon Mountain 

that was reportedly traced for 2 miles. A seam 

on the west side of Carbon Mountain, which he 

described as "apparently very persistent," was 

measured at two points about a third of a mile 

apart and was tentatively correlated with the abovementioned seam on the east side of the mountain, 

about half a mile distant. Fisher and Calvert 

(1914, p. 47) reported that an 8-foot seam on the 

west side of Trout Creek was traced for 600 feet 

along the surface, within which distance it thinned 

to 16 inches and became dirty. A 30-foot bed 

near the same locality was similarly found to thin 

to 18 feet and become softer "several hundred 

feet" to the southwest, and at about 1, 000 feet 

from the original prospect tunnel to consist of 

only 4 feet of soft dirty coal. Several other coal 

beds in the field, particularly on Trout and Clear 

Creeks, have been followed underground for 

distances ranging from a few feet to 350 feet 

Most of the tunnels terminated where the coal had1 

pinched out or had been cut off by faulting. 

A review of available reports indicates that 

change in thickness is a common feature of coal 

veins in the Bering River field. Not all the 

descriptions indicate the cause of the thickness 

change, but structural deformation, in the form 

of squeezing and faulting, and stratigraphic thinning are both represented. According to Fisher 

and Calvert (1914, p. 36) "in some places there 

is an actual thinning of the entire bed, and at 

others impure coaly shale or horsebacks reduce 

the thickness of the pure coal." 

Martin { 1908, pp. 68-74) described several 

examples of thickness change. The anthracite 

seam that was traced for 2 miles on the east 

side of Carbon Mountain was said to range in 

thickness from 9 to 25 feet, and a seam 200 

feet below, from 4 to 11 feet. A coal bed on the 

east bank of Canyon Creek 2 miles above its 

mouth was described as containing 2 feet 9 inches 

of coal at one point but being very variable in 

thickness and pinching out higher in the bluff. 

In a creek on the west side of Carbon Mountain 

opposite the mouth of Canyon Creek two coal 

seams were reported, one ranging in thickness 

from 3 to 21 inches and the other from 14 to 

24 inches. A third seam on the same creek 

ranged from 8 to 22 inches in thickness. A 

coal bed at the base of the falls on Clear Creek 

was found to thicken within a few yards from 8 

feet 2 inches to about 16 feet. A 10-foot bed 

near the west shore of Kushtaka Lake was 

de scribed only as "pinching out." 

Storrs (1910, p. 2342) found a coal seam, on 

the crest of Cunningham Ridge opposite the head 

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of Trout Creek, containing 32 feet of "very soft 

shelly coal***with two large benches of coal and 

slate mixture" that thinned to 4!feet within a 

di,stance of 60 feet to the southwest. He implied 

that this abnormal thickness change was probably 

related to a nearby faulted zone. Storrs (1910, 

p. 2344) also examined a 350-foot tunnel on the 

west side of Trout Creek and measured a maximum thickn.ess of more than 60 feet of coal, 

which he believed to be a "pocket" caused by 

faulting. 

Fisher and Calvert ( 1914, pp. 39-42) noted 

several .examples of abrupt thinning of coal seams. 

They described one bed, above the falls on Clear 

Creek, as being more than 40 feet thick at one 

point but "perceptibly thinned" a short distance to 

the south by a shaly parting. Below the falls 

and 300 feet above the creek on the west side, a 

coal seam 45 feet thick was found, but less than 

100 feet to the south it decreased to 25 feet 

"by the development of shaly members." On 

Trout Creek a coal bed opened by a 100-foot 

tunnel was found to have a "workable thickness" 

at the portal but to thin to 18 inches at the face. 

A second coal bed exposed in a 175-foot tunnel 

decreased in thickness from 5 feet at the portal 

to 3 feet at the fac~. \ 

.Preserlce of water and gas 

Martin (1908, p. 94) predicted that u~derground 

water would be encountered in large amounts in 

any mine development "owing to the abundance of 

surface water and the deep fracturing of the 

rocks," and noted that gas had been encountered 

in several of the longer tunnels. In discussing 

faults Fisher and Calvert (1914, p. 34) pointed 

out that "they act as underground channels for 

the excessive amount of water that permeates 

every part of the rock section." Although Storrs 

mentioned encountering gas at only one locality 

(1910, p. 2339), he stated in a discussion of 

proposed mine developments (1910, p. 2328} 

that "large fans and systematic ventilation will 

be required, for considerable gas has already 

been encountered very close to the outcrops." 

He also referred to probable large quantities of 

water as one of the mining problems to be faced. 

Williams (1914, p. 25) noted that larse quantities 

of methane were found in the two longest Navyexpedition tunnels. 

Physical condition of the' coal 

Aside from its inherent physical properties, 

much of the coal of the Bering River field has 

acquired additional characteristics through the 

shearing and crushing that accompany structural 

deformation. Martin (1908, p. 81) noted that 

most of the coal exposures in the eastern part of 

the field show "only a soft, weathered mass of 

coal which gives little indication of anthracite 

characte~." its classification as such being based 

on analyses and numerous float specimens of 

hard bright coal. As none of the openings in that 

part of the field extended beyond the zone of 

weathering he was unable to determine whether the 

anthracite became hard and unbroken at depth. 

He described the coal of the rest of the region, 

classed as semianthracite and semibituminous, 

as all being of a friable nature, many beds having 

been severely crushed and sheared. Storrs (1910, 

p. 2330) also found that "many of the seams show 

much crushing and shearing, and although the 

coals are hard, they are quite friable and have a 

flat, slippy, fracture." Evans (1920, p. 17) noted 

that the friable character of the coal from most of 

the beds on Carbon Creek would be a handicap 

during shipping, but added that the tendency to 

break into small sizes would be offset to some 

extent by the coking tendency of the coal which 

would cause the smaller particles to agglomerate 

into large masses instead of falling through the 

grates. 

In discussing the character of the coal with 

respect to mining conditions Williams (1914, p. 

24} stated: 

"In mining operations, judging from conditions 

thus far found, the loss of coal will be high. It 

is doubtful whether, under present mining methods, 

a recovery of over 25 percent will be possible 

from a number of the most favorable beds. It is 

believed that the coal of some beds will be found 

so soft and crushed that the coal will "flow" or 

"run" under pressure induced by the mining operations, so that it would be difficult to maintain 

pillars. It is possible that some modification of 

existinR methods of mine packing could be applied 

that would insure a high percentage of recovery; 

but such a method would necessitate the quarrying 

of rock or the excavation of gravels on the surface 

and deli very into the mine of the packing material 

and would render the cost of mining high." 

Fisher and Calvert ( 1914, pp. 36-37) described 

the coals of th~ Cunningham claims as follows: 

"They are prevailingly soft and friable, with a 

pronounced foliated structure and graphitic luster. 

In at least 90 percent of the beds the coal has been 

badly crushed and shearing planes are highly developed. A few beds appear to be moderately firm, 

but such beds are generally closely associated 

with faulting, where the pressure causing deformation has been released. The soft, friable condition of the coal is not a surface aspect due to 

weathering, as has generally been supposed, but 

is deep seated. In different parts of the field 

where development work has been carried on, the 

coals that are soft and friable at the surface do not 

increase perceptibly in hardness underground. " 

In commenting on the friability of the coal Martin (1908, p. 94) noted that if this condition persists at depth it would seriously affect the market 

value of the anthracite because of the high proportion of fine coal that would be produced in mining 

that would result from crushing during transportation. Both Martin and Storrs (1910, p. 2330) 

expressed the belief that the semibituminous coals 

would not be so seriously affected by this condition when used as steam or coking coals. However, 

impairment of the combustion qualities would not 

be the only effect of the high proportion of slack 

resulting from the crushed, friable condition of the 

coal. In loading the pulverized coal at the mine 

face more impurities from the roof and partings 

would be unavoidably mixed with the coal than 

would happen in coarser material. Williams (1914, 

p. 25) noted that in each of the four tunnels from 

which the Navylcoal sample was taken the hanging 

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wall consisted of soft, slippery shale that grades 

downward into the coal. He pointed out that such a 

roof is difficult to hold, especially in a region of 

broken strata, and expressed the belief (1914, p. 

26) that the coal would require washing because of 

impurities within the beds, the prevailing soft 

nature of the coal, and the probable admixture of 

roof material. 

The efficiency of separation by wet cleaning of 

coal begins to drop sharply below the 2-millimeter 

size, and very little separation is effected below 

the !-millimeter size. Washingofthe Bering River 

coal, consisting of a large proportion of slack, 

would therefore probably involve excessive fuel 

loss, except possibly by an expensive flotation process. 

Another effect of the high proportion of slack 

would be the retention of much of the large amount 

of extraneous moi'sture that would be expected in 

most of the coal mined in the area. This excess 

water would be particularly troublesome in winter, 

when it would require the installation either of 

expensive drying equipment at the mine, or of 

facilities for thawing or otherwise removing the 

frozen coal at the unloading point. 

A general impression of the condition of the 

coal in different parts of the field may be gained 

from the following summary of descriptions of 

individual exposures extracted from the reports 

reviewed. 

Clear Creek. --Storrs {1010, pp. 2339-2340) 

mentioned 10 coal exposures along Clear Creek, 

but referred to the condition of only 5 of them. 

Of these, three were described as hard bright 

coal, one showed the effect of crushing in the form 

of a "flat, slippy fracture", and one was "so 

faulted that no section could be taken." Fisher 

and Calvert (1914, pp. 38-39) described three 

coal outcrops along Clear Creek, all of which 

were badly broken or crushed, and two contained 

"cannon-ball" nodules of hard impure coaly 

material. 

Barrett Creek.- -On lower Barrett Creek Storrs 

(1910, p. 2340) noted five coal outcrops, which 

he described as "badly disturbed and faulted, 

none of them showing in minable shape." On a 

west fork, above the falls, he measurecl 13 beds, 

ranging in thickness from 3 to 17 feet, of which 

one was described as "shelly," two as faulted, 

one as containing "sulfur kidneys,'' and four as 

"very soft." Fisher and Calvert (1914, pp. 38-

39 ) examined what is probably the same series of 

beds, which they described as "bright and relatively clean, but, without exception, badly crushed 

into a molybdenitic structure. Shaly bodies, 

commonly known as 'horsebacks', are frequent in 

the thicker beds. " On the headwaters of the east 

branch of Barrett Creek Storrs (1910, pp. 2340-

2341) noted "very disturbed measures" in which 

all the coal examined was "soft" or faulted and 

unminable." 

Moore Creek. --Along the main course of Moore 

Creek, Storrs (1910, pp. 2341-2342) examined 

eight coal outcrops. Of the four he described, 

two were of hard bright coal, one was a coal and 

slate mixture, and one was badly faulted. On the 

eastern headwaters five seams were noted, of 

which three were badly faulted and soft, and two 

were hard and presumably undisturbed. On a 

western headwater he found four coal seams--one 

25 feet thick- -that were all of soft coal or greatly 

disturbed. 

Of four beds described by Fisher and Calvert 

(1914, p. 40) on Moore Creek, three were crushed 

or sheared and one was referred to only as "clean 

coal." In the saddle in the crest of Cunningham 

Ridge at the head of Moore Creek .they reported 

two thick beds ,oflsoft, crushed coal. 

Trout Creek. --Storrs (1910, p. 2343) examined 

eight coal exposures on thP. headwaters of Trout 

Creek. He described a 32-foot bed as "soft shelly 

coal," an 18-foot bed as containing slate and dirt 

streaks, and a third bed as a "disturbed outcrop." 

No description was given of the other five beds. 

In the main Trout Creek valley he made specific 

note of 25 coal exposures; of these 7 were 

iescribed as faulted, 2 as soft coal (presumably 

crushed), 3 as part hard and part soft (crushed?) 

coal, and 5 as hard bright coal. The condition of 

the other eight exposures was not given. 

Of nine coal beds examined on Trout Creek by 

Fisher and Calvert (1914, pp. 41-43, 46-48), 

seven were described as badly crushed and 

sheared or soft. The other two beds were hard 

and bright where first examined but where found 

to thin and become soft and ·dirty within short 

distances. 

Bear Creek. --Storrs (1910, p. 2345) described 

three coal beds on Bear Creek, of which one 

consisted of hard bright coal and two were in part 

hard and bright and in part soft and dirty. Fisher 

and Calvert (1914, p. 48) did not describe individual outcrops on Bear Creek but remarked that 

coal beds where found were badly crushed. 

Kushtaka Ridge. --Fisher and Calvert (1914, p. 

43) described one coal bed, exposed in a tunnel 

on the east slope of Kushtaka Ridge, as soft and 

crushed, and two beds as being partly hard and 

partly crushed. They also mentioned seeing 

several other coal openings in a disturbed zone, 

in which the coal was generally soft and crushed. 

Carbon Creek. --On Carbon Creek and its tributaries Fisher and Calvert ( 1914, pp. 43-44) 

described four coal outcrops, of which all appeared 

to be of good quality, but one was soft and friable 

and another was in a closely folded and faulted 

zone. 

Bering Lake. --Fisher and Calvert (1914, p. 46) 

reported that the McDonald mine, on the east 

shor·e of Bering Lake, was opened on a 6-foot bed 

of impure coal that was cut by· several minor faults. 

The mine output was estimated to contain more than 

90 percent slack coal. Two beds opened south of 

the mine were said to be soft and crushed. 

Canyon Creek. --The only available description 

of coal on Canyon Creek is that given by Fisher 

and Calvert (1914, pp. 45-46) of an 11-foot 

bed exposed in a tunnel on Canyon Creek about 

2. 7 miles above its mouth. The bed was soft and 

friable and, except for the upper 3 or 4 feet, too 

- 10 -
dirty to be minable. Other coal outcrops on 

Canyon Creek were measured by Martin but not 

described. 

Carbon Mountain. --No detailed descriptions of 

coal outcrops on Carbon Mountain are available, 

but general statements by Martin and others indicate that the coal of the eastern part of the field 

is characteristically crushed and friable. 

CONCLUSIONS 

Available information leaves little doubt that 

coal of high quality, including both coking coal 

and anthracite, is present in great aggregate 

amount in the Bering River field. As the coal 

beds are exposed only in scattered short tunnels 

and isolated outcrops, little is known of their 

over-all continuity. Examinations of hundreds of 

exposures, however, and a few attempts at 

tracing coal veins along the outcrop as well as 

underground, have revealed a tendency for the 

coal to change thickness within comparatively 

short distances, either by thinning of the beds 

or by thickening of rock partings. 

Probably overshadowing in importance the 

original extent and continuity of the various coal 

beds is the fact that in a large proportion of the 

exposures examined the coal has been greatly 

disturbed, either by complex faulting or by 

crushing and shearing resulting from structural 

deformation. Such conditions will, in many places, 

complicate if not preclude the successful mining 

of the coal, particularly where shearing of the 

coal has been accompanied by the introduction of 

impurities from the enclosing strata. 

In view of the above conditions, which seem 

typical of all parts of the field that have been 

studied, the prospects of proving a large reserve 

tonnage of economically minable coal in a single 

block are not encouraging. Smaller blocks, possibly ample to keep a small mine in operation for 

several years, may be present in several parts 

of the field, particularly on Carbon, Trout, and 

Clear Creeks. Any such block. should be 

thoroughly tested by both surface and underground 

prospecting before any large investment in surface 

plant is made. 

REFERENCES CITED 

Cooper, H. M. , and others, 1946, Analyses of 

mine, tipple, and delivered samples, in Analyses of Alaska coals: U. S. Bur. Mines Tech. 

Paper 682, pp. 19-110. 

Evans, G. W., 1920, A report on the property of 

the Bering River Coal Company, Bering River 

coal field, near Cordova, Alaska: Unpublished 

report submitted by consulting mining engineer 

to Mr. Falcon Joslin, president, Bering River 

Coal Company, September 10. 

Fisher, C. A., 1910, Report on the Cunningham 

coal property, Controller Bay region, Alaska: 

U. S. Congress, Investigation of the Department 

of the Interior and of the Bureau of Forestry. 

Hearings before Joint Committee to investigate 

Interior Department and Bureau of Forestry, 

vol. 2, pp. 1073-1092. 

Fisher C. A., and Calvert, W. R., 1914, Geology 

of the Bering River field and its relations to 

coal mining conditions, in Report on Coal in 

Alaska for use in United States Navy: 63d Cong., 

2d sess. , H. Doc. 876, pp. 29-50. 

Fisher, W. L., 1912, Alaskan coal problems: 

U. S. Bur. Mines Bull. 36. 

Kennedy, Andrew, 1910, Report on a field examination of the 33 Cunningham Alaska coal entries: 

U. S. Congress, Investigation of the Department 

of the Interior and of the Bureau of Forestry. 

Hearings before Joint Committee to investigate 

Interior Department and Bureau of Forestry, 

vol. 2, pp. 1039-1040. 

Martin, G. C. , 1908, Geology and mineral 

resources of the Controller Bay· region, Alaska: 

U. S. Geol. Survey Bull. 335. 

Navy Department, 1914, Report on coal in Alaska 

for use in United States Navy: .63d Cong. , 2d 

sess. , H. Doc. 876. 

Storrs, A. H., 1910, Report on the Cunningham 

coal lands and Bering River coal field near 

Katana, Kayak district, Alaska, November 

1907: 'u. S. Congress, Investigation of the 

Department of the Interior and of the Bureau of 

Forestry. Hearings before JointCommitteeto 

investigate Interior Department and Bureau of 

Forestry, vol. 3, pp. 2326-2345. 

Williams, R. Y., 1914, Mining conditions in the 

Bering River field, Alaska, as result of the 

field examination of the United States Navy 

Alaskan coal investigating expedition, .!!!. Report 

on Coal in Alaska_ for use in United States Navy: 

63d Cong., 2d sess. , H. Doc. 876. 

Wingate, G., 1910, Cunningham group coal claims, 

Chugach Forest, Bering River, Alaska: U. S. 

Congress, Investigation of the Department of 

the Interior and of the Bureau of Forestry. 

Hearings before Joint Committee to investigate 

Interior Department and Bureau of Forestry, 

v~l. 2, p. 1043. 

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