EC 310;

GEOLOGICAL SURVEY CIRCULAR 310

STRIPPING-COAL DEPOSITS ON 

LOWER LIGNITE CREEK 

NENANA COAL FIELD, ALASKA
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 310

STRIPPING-COAL DEPOSITS ON LOWER LIGNITE CREEK 

NENANA COAL FIELD, ALASKA

By Clyde Wahrhaftig and Joseph H. Birman

Washington, D. C., 1954

Free on application to the Geological Survey, Washington 25, D. C.
150° 148° 146°

Heoly W CREEK AREA

ft 

McKinley Pork

60° -

152° 150°

50

i i i

150 Miles 

J_____________I

Figure 1. Map of south-central Alaska, showing location of lower Lignite Creek area.

iv
STRIPPING-COAL DEPOSITS ON LOWER LIGNITE CREEK 

NENANA COAL FIELD, ALASKA

By Clyde Wahrhaftig and Joseph H. Binnan

CONTENTS

Abstract........................

Introduction ....................

Geology........................

Stratigraphy................

Birch Creek schist.....

Coal-bearing formation.

Nenana gravel.........

Terrace gravel........

Glacial erratics........

Landslides ...........

Structure ..................

Stripping-coal deposits...........

Distribution and quality 

of the coal...............

Page

1 Stripping-coal deposits Continued

2 Stripping-coal reserves......

2 Recommendations for future

2 exploration.....'..........

2 Factors affecting mining of the

2 coal..........................

4 Nature of the overburden....

4 Source of water for hydraulic

4 stripping.................

4 Disposal of debris...........

5 Landslides.................

5 Badland erosion ............

	Access to the coal field .....

5 Literature cited .................

Page

10

10

10

11

11

ILLUSTRATIONS

[Plates 1-5 in pocket]

Plate 1. Geologic map of the valley of lower Lignite Creek, Nenana coal field, Alaska.

2. -Structure-contour map on bed H, lower Lignite Creek, Nenana coal field, Alaska.

3. Areas of stripping coal in beds B and H and the basal bed on lower Lignite Creek, Nenana 

coal field, Alaska.

4. Areas of stripping coal in bed F, lower Lignite Creek, Nenana coal field, Alaska.

5. Areas of stripping coal in bed E, on lower Lignite Creek, Nenana coal field, Alaska. 

Figure 1. Map of south-central Alaska, showing location of lower Lignite Creek area..............

2. Correlated stratigraphic sections of the stripping-coal beds on lower Lignite Creek,

Nenana coal field, Alaska.........................................................

Page

iv 

3

TABLES

Table 1. Analyses of coal on lower Lignite Creek .........

2. Reserves of stripping coal on lower Lignite Creek,

Page 

7

ABSTRACT

Stripping-coal reserves in an area of about 

24 square miles extending from the Nenana River about 

6 miles up the valley of Lignite Creek are estimated 

to amount to about 95,000,000 tons. The strippingcoal reserves are located in the lower and middle 

members of the_Tertiary coal-bearing formation. 

Five continuous beds in the middle member range in 

thickness from 5 to 30 feet, and a discontinuous bed

at the base of the lower member is about 60 feet thick. 

Analyses of outcrop samples, as received at the 

laboratory, show a heating content of 7,500 8,200 Btu, 

an ash content of 6 to 14 percent, and a moisture content of 25 percent. The reserve estimate is based on 

a maximum thickness of overburden of 200 feet. Coal 

below the level of Lignite Creek or its major tributaries 

was not considered as it was assumed that stripping 

would be by hydraulic methods. Uncertainties regarding the position of the coal outcrops and the extent of
burning of the coal beds are the basis for a 

recommendation that, where possible, the stripping reserves be tested by drilling.

Overburden consists largely of weakly consolidated sandstone and includes some coarse 

gravel and a few boulders 20 feet or more in 

diameter. Water for hydraulic mining can be 

obtained from the Nenana River. Lignite Creek 

does not appear to be a dependable source. 

Disposal of debris may affect the channel of the 

Nenana River causing damage to railroads and 

structures. Landslides are common in the valley 

of Lignite Creek and will affect mining operations 

and transportation routes.

INTRODUCTION

In 1952 the Geological Survey, in an effort 

to locate and evaluate deposits of readily available 

stripping coal in Alaska, started an investigation 

of coal deposits on lower Lignite Creek in the 

Nenana coal field, where previous investigations 

had indicated that considerable deposits of stripping coal might be found.

The stripping-coal deposits on lower 

Lignite Creek lie in the southern two tiers of 

sections in T. US., R. 7 W., and in the 

northern tier of sections in T. 12 S.,, R. 7 W., 

F. B. M. The deposits are between 1 and 6 miles 

east of the Alaska Railroad at Lignite, which is 

on the opposite side of the Nenana River from 

Lignite Creek. Lignite is 108 miles by rail 

south of Fairbanks and 248 miles north of 

Anchorage (fig. 1). At present the only means 

of access to Lignite Creek is by foot or horseback.

Field investigations of the stripping coal 

were made during the period June 25 to July 15, 

1952. Food and camping equipment were cached 

at two campsites earlier in June by helicopter. 

The field work consisted of measuring all coal 

outcrops on lower Lignite Creek and plotting the 

coal outcrops, as well as other pertinent geologic 

information, on manuscript copies of topographic 

maps that were prepared by multiplex methods 

by the Topographic Division of the Geological 

Survey on a scale of 1:20,000. From this 

information a structure-contour map of a key 

coal bed was constructed, and areas where the 

coal beds were overlain by less than 200 feet 

of overburden were outlined. Attention was paid 

also to geologic factors, such as landslides, 

burning of coal beds, and water supply, that 

would affect the extraction of the coal and its 

transportation to the railroad.

GEOLOGY 

Stratigraphy

The general geology of the Lignite Creek 

area has been described by Wahrhaftig, Hickcox, 

and Freedman (1951). The reader is referred to their 

report for the detailed descriptions of the formations. 

The lithologic descriptions given in their report are 

not repeated below but are supplemented Where necessary.

Birch Creek schist

The oldest formation in the area is the Birch 

Creek schist, a highly contorted black to gray quartzsericite schist cut by numerous veins of milky quartz. 

The Birch Creek schist crops out over much of 

sees. 1 and 2, T. 12 S., R. 7 W., and sees. 35 and 

36, and the SEi sec. 34, T. US., R. 7 W. (See pi. 1.) 

It forms the core of a westward-plunging anticline 

and is in fault contact on the south with the Nenana 

gravel. On the west and north it is overlain unconformably by the coal-bearing formation.

Coal-bearing formation

The Tertiary coal-bearing formation has been 

divided by Wahrhaftig, Hickcox, and Freedman (1951, 

p. 147-152) into three members. The lower member 

crops out chiefly along the north side of Lignite Creek 

as far west as the western part of sec. 34, T. 11 S., 

R. 7 W. It contains one thin discontinuous coal bed 

near the top (fig. 2, sections 2 and 7), which is 

apparently correlative with the "F" bed of the Suntrana 

mine and is too thin to be mined by stripping.

A very thick coal bed has been observed at two 

places at the base of the lower member: in the 

Ei sec. 35, T. US., R. 7 W., and at the mouth of 

the small stream that drains most of sec. 3, T. 12 S., 

R. 7 W. (pi. 1). Clinker, apparently from the burning 

of this coal bed, forms bright-red outcrops that rest 

on schist on the south bank of Lignite Creek in sec. 35 

and on the north bank of the creek in sec. 34, T. 11 S., 

R. 7 W. This coal bed, herein referred to as the 

"basal coal bed, " is about 60 feet in total thickness on 

the west bank of Lignite Creek in the E| sec. 35 (fig. 2, 

section 6), and is at least 65 feet thick in the exposure 

at the mouth of the stream that drains sec. 3 (fig. 2, 

section 4). In sec. 35, however, it interfingers southward at the base with coarse talus breccia consisting 

of fragments of quartz and Birch Creek schist. To 

the north it is cut off by a fault that trends about 

N. 50°-60° E. and passes westward down the middle 

of Lignite Creek. For most of its length the south side 

of the fault is the downthrown side. At the east end, 

however, the north side may be the downthrown side. 

North of the faulty the lower few hundred feet of the 

coal-bearing formation is well exposed along the 

creek in the Wj sec, 35, and the coal bed south of the 

fault is not represented in the exposures on this creek, 

which consist entirely of sandstone and claystone, with 

a few bony layers. Presumably the fault was active 

during the deposition of the coal or immediately after 

its deposition, and the coal accumulated or was preserved in the downtilted portion of a small fault block.

The presence of the lower member of the coalbearing formation west of sec. 3, T. 12 S., R. 7 W., 

beneath younger rocks, is uncertain. Evidence 

gathered by the senior author from other parts of the 

coal field suggests that it may not extend west of 

sec. 3; but if it should continue westward, any coal in 

the lower member would be considerably below the 

level of Lignite Creek and could be mined only by 

underground methods.

The middle member of the coal-bearing formation 

crops out in the hills north of Lignite Creek between 

the east border of the area shown in plate 1 and the
8 FEET

EXPLANATION

Cool, partly 

covered

Bony coal

Sandstone, In 

part pebbly

Conglomerate

Talus breccia

Bony claystone Birch Creek schist

Claystone Section covered

See plate (for location 

of sections

0.3 Ml. E. OF TOWNSHIP 

LINE ON 8. BOUNDARY OF 

8EC.30.T.MS. R.6W., F.B.M 

FEET

0.8

1 0 

SCALE IN FEET

Stratigraphic measurements by Clyde Wahrhaftlg 

and C. A. Hlckcox In 1945 and by Clyde Wahrhaftlg and J. H. Blrman in 1952.

Figure 2. Correlated stratigraphic sections of the stripping-coal beds on lower Lignite Creek, Nenana coal field,

Alaska.
western part of sec. 5, T. 12 S., R. 7 W.; on the south 

side of Lignite Greek it crops out in parts of sees. 3, 

4, and 5, T. 12 S., R. 7 W. A narrow belt of steeply 

dipping beds of the middle member extends along the 

south border of sec. 2, T. 12 S., R. 7 W.

The coal beds of the middle member are generally 

thick and very persistent laterally. They can be correlated with considerable certainty from outcrop to 

outcrop along Lignite Creek, and most of the same 

beds have been recognized farther south on Healy Creek 

and to the north in the basin of California Creek, as 

well as elsewhere in the Nenana coal field. Outcrops 

of the middle member on the east bank of the Nenana 

River 2 miles north of Lignite Creek, on the west 

bank of the Nenana at Healy, and at the Diamond coal 

mine 3j miles southwest of Healy indicate that the 

middle member underlies all the area shown in plate 1 

north and west of its belt of outcrop and south of the 

great fault along the north border of sees. 9, 10, 11, 

and 12, T. 12 S., R. 7 W. South of this fault, however, it has been displaced downward to several 

thousand feet below the surface. All the stripping-coal 

reserves on lower Lignite Creek, with the exception 

of those in the thick bed at the base of the lower member, lie in the middle member.

The upper member of the coal-bearing formation 

crops out north, west, and south of the outcrop area of 

the middle member. It is in fault contact with the 

Nenana gravel'along the north border of sees. 8, 9, and 

10, T. 12 S., R. 7 W. The lithology of the upper member has been described by Wahrhaftig, Hickcox, and 

Freedman (1951, p. 149 and 151-152) and v/ill not be 

reviewed here. The upper member contains no deposits of stripping coal.

Nenana gravel

On lower Lignite Creek the coal-bearing formation 

is overlain with apparent conformity by the Nenana 

gravel. In the western part of the Nenana coal field the 

Nenana gravel rests unconformably on the coal-bear ing 

formation (Wahrhaftig, 1951, p. 182-183). Unpublished 

results of investigations to the east and north of Lignite 

Creek by the senior author have shown that, in general, 

the relationship between the two formations is an unconformity and that the apparent conformity on 

Lignite Creek and Healy Creek is an exception. The 

lithology of the Nenana gravel has been described by 

Wahrhaftig, Hickox, and Freedman (p. 152-153) and 

will not be reviewed here. The Nenana gravel crops 

out north of the belt of outcrops of the coal-bearing 

formation in sees. 25, 26, 27, 28, 29, and 30, 

T. 11 S., R. 7 W., and underlies most or' all of 

sees. 8, 9, 10, 11, and 12, T. 12 S., R. 7 W.

and the broad flats 300 to 600 feet above Lignite Creek 

which form most of the interfluves between tributaries 

to Lignite Creek from the north. Some of these flats 

are half a mile wide from east to west and 1-| miles 

long from north to south. The higher flats north of 

Lignite Creek slope toward the-creek at gradients of 

about 400 to 500 feet per mile and are mantled with a 

layer of gravel derived from hills of Nenana gravel to 

the north. This layer of gravel is commonly between 

50 and 100 feet thick but locally reaches a thickness 

of 150 feet. It is exposed at the tops of bluffs along 

the north side of Lignite Creek. The broad flat south 

of Lignite Creek is underlain by a similar layer of 

gravel, deposited by Lignite Creek and the Nenana River. 

The thickness of this gravel ranges from a few-inches 

in the eastern part of sec. 4 to 85 feet at the north 

end of the bluff along the Nenana River in sec. 5. 

The average cobble size of the gravel exposed in this 

bluff is between 3 and 6 inches, and the largest boulders observed are 4 feet in diameter. The higher 

terraces were formed during the later glacial stages 

of this region and dissected during interglacial and 

postglacial time.

The lower terraces range in height from 5 to 

50 feet above present stream grade. The lowermost 

generally consist entirely of stream gravel. The 

higher of this group (more than 10 feet high) generally 

are bedrock terraces overlain by a veneer of gravel 

3 to 10 feet thick. The stream gravel is usually 

coarse; average cobble size is from 3 to 6 inches, 

and boulders up to 3 or 4 feet in diameter are common. 

The lower terraces were formed after the maximum 

expansion of the latest great ice sheet in this region.

Glacial erratics

Gigantic boulders of granite, greenstone, and 

conglomerate are widely scattered over the area 

shown in plate 1 but are not shown on the map. They 

are sparsely scattered over the terraces and hillsidesone boulder to every acre or every few acres and 

there is commonly one every few hundred feet along 

most of the tributaries of Lignite Creek. A total of 

244 boulders larger:than 5 feet in diameter was 

counted in the active floodplain of Lignite Creek in the 

area of plate 1; the greatest concentration, around a 

sharp bend of Lignite Creek in the N£ sec. 3, T. 12 S., 

R. 7 W., is about 165 per mile. Some of these boulders are as much as 30 or 40 feet on a side. Most 

of them are granite. They, were deposited by an 

early Pleistocene glaciation on a surface now completely destroyed in this area and have been let down, 

without much lateral movement, as much as 1, 500 feet, 

as the finer grained materials beneath them were 

removed by erosion.

Terrace gravel

Extensive terraces and pediments have been cut 

by the Nenana River, Lignite Creek, and their tributaries and are mantled by gravel deposits. 'The 

terraces and pediments fall into two groups on the 

basis of height above stream grade. Those of the 

higher group are 300 to 600 feet above the present 

level of Lignite Creek and the Nenana River; this 

group includes the extensive plain at 1, 700-1,900 feet 

in altitude in sees. 4,, 5, 8, and 9, T. 12S., R. 7 W.,

Landslides

About 11 percent of the total area along lower 

Lignite Creek that is likely to be involved in the strip 

mining and transportation of coal is covered by active 

or dormant landslides. In some sections, such as 

sees. 3 and 5, T. 12 S., R. 7 W., this proportion is 

as high as 20 percent. The landslides are concentrated 

along the walls of the valley of Lignite Creek and the 

canyons of its tributaries. In many of the canyons 

landslides meeting from opposite walls have dammed
the creeks and caused them to form alluvial plains underlain by gravel and sand. Geologically, the loci of most of the 

landslides are bedding planes where ground water is 

concentrated in fine material on the top of an impervious 

layer. Such bedding planes are common at the base 

and top of coal beds, in shale beds, and at the base of 

the coal-bearing formation. The landslides may be 

caused by over steepening of banks, lateral or downward erosion by streams, headward erosion of gullies, 

burning out of coal beds, or, presumably, by unusual 

concentrations of ground water at certain horizons 

during exceptionally wet seasons. Some landslides 

and earthflows on Lignite Creek have been observed 

to move with considerable rapidity as much as several 

feet per minute on slopes as gentle as 3° or 5°. Many 

of the landslides on Lignite Creek have slopes of less 

than 10°. Most of the landslides are slumps characterized by semicircular headwall scarps and by the presence of unit blocks of considerable aerial extent near 

their heads. Earthflows and debris slides are common, 

however, particularly on frozen claystone which has 

been exposed to thawing.

Structure

The major structural features of lower 

Lignite Creek are a bifurcating, westward-plunging 

anticline and, bounding the anticline on the south, a 

steeply dipping reverse fault. (See pis. 1 and 2.) 

The anticline bifurcates westward in the middle of 

sec. 1, T. 12 S., R. 7 W. The southern branch 

trends about due west and lies just south of the township line between Tps. 11 and 12 S. Dips along the 

north flank of this branch are 5° -12° N. The westward plunge of the axis averages about 3§-°, or roughly 

300 feet per mile. The plunge of the axis ranges from 

2° W., near the east border of sec. 4, to 10° W., in 

the western part of sec. 5. Between the axis of the 

southern branch and the fault are several minor folds 

with amplitudes generally less than 50 feet. These are 

exposed in cross section on the west wall of the canyon 

in the E-£ sec. 4. They are indicated on the structure 

contour map (pi. 2) by waviness of the structure contours 

in that area. The northern branch trends about 

N. 55°-70° W. Dips range from 3°-15° N., on its 

north flank, and 7° -30° SW on its south flank. It 

plunges gradually westward but has at least one small 

dome. The syncline between the two forks of the anticline has an amplitude of 200 to 500 feet.

The fault that borders the anticline on the south 

forms the southern boundary of the area of minable 

coal on lower Lignite Creek. It is exposed in the 

valley of Gagnon Creek about 2 miles east of the east 

border of the area shown in plate 1 (Wahrhaftig, Hickcox, 

and Freedman, 1951, p. 154 and pi. 18). Here it is 

a reverse fault with a dip of 65°-75° N. At the east 

border of T. 12 S., R. 7 W., the fault brings the 

upper part of the Nenana gravel on the south against 

Birch Creek schist on the north, and its stratigraphic 

displacement is about 5, 000 feet. West of the east 

part of sec. 2, T. 12 S., R. 7 W., the coal-bearing 

formation that wraps around the nose of the anticline 

in sees. 3, 4, and 5, T. 12 S., R. 7 W., forms the 

hanging wall of the fault at the surface. The fault 

passes westward into a southward-dipping monocline, 

in which the Tertiary rocks exposed in the east bank 

of the Nenana River dip vertically for a distance of 

2, 500 feet across the strike. All the stratigraphic

units that have been recognized in the Nenana gravel 

are present in the 2, 500-foot section in this bluff, 

which includes also most of the upper member of the 

coal-bearing formation. The distance across the 

strike, however, is not great enough to accomodate 

the equivalent stratigraphic sections exposed at 

several localities within a radius of a few miles of 

this bluff. It is necessary to assume that in the monoclinal folding considerable attenuation of the section 

has taken place, reducing its thickness by approximately 

1, 000 feet. The coal-bearing formation on the south 

side of the fault and its monoclinal westward extension, 

in T. 12 S., R. 7 W., lie more than 3,000 feet below 

the surface, beyond the range of possible coal mining.

Two minor faults cut the coal-bearing formation 

along Lignite Creek. The fault that bounds the basal 

coal bed, in sec. 35, T. 11 S., R. 7 W., has already 

been described. A small fault that dips about 35° SE 

and strikes roughly N. 45° E. cuts the coal beds on the 

south bank of Lignite Creek in the Ni sec. 4, T. 12 S., 

R. 7 W. Its displacement is about 30 to 40 feet.

In this area most of the folding and faulting of 

the coal-bearing formation took place shortly after 

the Nenana gravel was deposited. However, a gentle 

eastward-trending scarp about 50 feet high coincides 

with the trace of the major fault just south of the north 

border of sees. 8 and 9 and offsets the gravel-covered 

terrace south of Lignite Creek. Its presence suggests 

that there has been activity on this fault in Pleistocene 

time, after the formation of the terrace, which is the 

outwash of a presumably early Wisconsin glaciation. 

The outwash of a late Wisconsin glaciation on the west 

side of the river is not offset, so presumably the renewal of activity on the fault occupied only a short 

time within an interglacial epoch during middle 

Wisconsin time.

STRIPPING-COAL DEPOSITS 

Distribution and quality of the coal

Six coal beds-on lower Lignite Creek are believed to contain coal that is recoverable by stripping. 

These are bed H at the top of the middle member, 

beds G, F, E, and B, and the basal coal bed in 

sees. 3, T. 12 S., R/7W., and 35, T. US., R. 7W. 

(pi. 1). With the exception of the basal coal bed, these 

are all in the middle member and can be correlated 

with beds at the Suntrana mine on Healy Creek 

(Wahrhaftig, Hickcox, and Freedman, 1951, pi. 22). 

Bed H correlates with the no. 6 bed, bed G with the 

no. 5 bed, bed F with the no. -4 bed, bed E with the 

no. 3 bed, and bed B with the no. 1 bed. Bed H 

averages about 25 feet in thickness, bed G about 5 feet, 

bed F about 28 feet, and bed E about 20 feet. Reserves 

for bed B were calculated only for the eastern part of 

the area shown in plate 1; there it averages about 

15 feet of coal with many partings. The basal bed 

contains about 60 feet of coal in the two places where 

it was measured. Coal beds B through H are separated 

by 50 to 150 feet of poorly consolidated sandstone, in 

part pebbly, with minor amounts of claystone and 

some thin coal beds. The thick coal beds have been 

traced from the mouth of Lignite Creek to Thistle Creek, 

14 miles east, and from Suntrana on the south to 

MacAdam Creek on the north, a distance of 12 miles. 

In this area their thicknesses vary uniformly from
centers of maximum thickness located near Lignite Creek, 

and the stratigraphic intervals between them vary within small limits.

Six samples of coal on lower Lignite Creek were 

collected for analysis during the course of the investigation, five from within the area of plate 1 and one 

0. 3 mile east of the east border of the area of olate 1. 

Analyses of these samples, as well as two others reported by Martin (1919, p. 8-9) are shown in table 1.

The coal is black, generally has a dull luster, 

and a dark-brown streak. The upper few feet of the 

coal beds above bed F have the appearance of a mat 

of intertwined twigs, but all beds from bed F downward, and the lower parts of beds G and H, have a 

blocky fracture. The coal has the same general appearance as coal from the same formations in the valley of 

Healy Creek, and has comparable heating qualities.

Stripping-coal reserves

Reserves of strippable coal on lower Lignite Creek 

were calculated in the following manner: a structurecontour map was first prepared on bed H, the uppermost bed, for which the greatest amount of data was 

available (pi. 2). Then, using the intervals taken from 

the stratigraphic sections (fig. 2), structure-contour 

maps of beds B, E, and F were constructed. In preparing the structure-contour map on bed F, the interval 

between beds F and H was assumed to be 150 feet; in 

preparing the structure-contour map on bed E, the 

interval between beds E and H was assumed to be 

300 feet. These intervals, although not precise, are 

believed to be as accurate as the locations of outcrops 

on the map. For each bed, the points at which the 

structure contours crossed the topographic contours of 

the same altitude were joined to give the line of outcrop 

of the bed. The points at which each structure contour 

on bed H joined the topographic contour 100 feet higher 

were joined; between the curve so made and the outcrop, 

bed H is overlain by less than 100 feet of overburden. 

Similarly the points at which contours on bed H are 

crossed by topographic contours 200 feet higher were 

joined to delimit the area in which bed H is overlain 

by 100 to 200 feet of overburden. The 200-foot overburden line, at which the thickness of overburden equals 

10 times the thickness of the coal bed, was arbitrarily 

selected as the cutoff for bed H. The areas of these 

reserves on bed H, as well as stripping reserves for 

bed B and the basal bed, are shown in plate 3.

The area between the outcrops of beds H and F 

is the area in which bed F would be overlain by less 

than 150 feet of overburden. Once bed H was mined 

out, bed F would be overlain by about 150 feet of overburden in the area formerly occupied by bed H, and 

so would be available for stripping. Within this' 

150 feet of overburden would be bed G, averaging 

5 feet thick. The area underlain by reserves of 

bed F is shown in plate 4. Similar considerations 

apply to bed E, except that only 60-90 feet of sandstone lie between beds E and F. Reserve areas in 

bed E are shown in plate 4. Reserves of bed B were 

computed in a similar manner. (See pi. 3.) No coal 

below drainage level, on Lignite Creek or its major 

tributaries or below a level from which overburden 

could be sluiced to Lignite Creek was included in the 

stripping reserves.

For the basal bed different methods of calculation were used. Most of the basal bed in sec. 35, 

T. 11 S., R. 7 W., has been removed by erosion, 

so it was assumed that an average of 10 feet remained 

beneath the area underlain by this bed. In sec. 3, 

T. 12 S., R. 7 W., a strike length of 500 feet, a 

dip length of 100 feet, and an average thickness of 

60 feet were assumed from the single outcrop of the 

basal bed.

For all the area except sees. 25 and 36, and the 

Ei sees. 26 and 35, T. 11 S., R. 7 W., the reserve 

areas were measured on the multiplex manuscript at 

a scale of 1:20, 000. For sees. 25 and 36, and the 

Ei sees. 26 and 35, T. US., R. 7 W., a planetable 

map of the coal outcrops at a scale of 1:4, 800 had 

been prepared during the course of the 1946 investigations. The topography from the multiplex manuscript was enlarged to this scale and superposed 

on the outcrop map, and the reserve areas were 

measured at a scale of 1:4, 800.

The stripping coal computed for the lower 

Lignite Creek area amounts to a little over 95 million 

short tons. Of this amount, 42 million tons lies south 

of Lignite Creek in sees. 3, 4, and 5, T. 12 S., R. 7 W.; 

33 million tons lies north of Lignite Creek in sees. 33 

and 34, T. 11 S., R. 7 W., and sees. 4 and 5, T. 12 S., 

R. 7 W.; and 20 million tons lies north of Lignite Creek 

in sees. 25, 26, 35, and 36, T. US., R. 7 W. (See 

pis. 3, 4 and 5.) The U. S. Government coal reservation in sec. 32, T. 11 S., R. 7 W., and sees. 4 and 5, 

T. 12 S., R. 7 W., contains 21 million tons of stripping coal, nearly all of which lies within 2 miles of the 

Alaska Railroad.

The coal beds on lower Lignite Creek are exposed 

at intervals of 1 to l£ miles, so that reserves calculated 

on the basis of these outcrops would normally be regarded 

as indicated reserves. However, several factors combine to make the calculation of stripping-coal reserves 

much more uncertain. It was felt that the quality of 

the field data available in the present outcrops did not 

warrant a detailed planetable survey, especially as 

the deposits would probably have to be tested by drilling in advance of mining. The multiplex manuscript 

map was, therefore, used as base. As this map has 

a contour interval of 100 feet, the positions of outcrops 

could rarely be determined with greater vertical 

accuracy than the nearest 50 or 100 feet. This large 

limit of error introduces very large uncertainties in 

the stripping reserves. For instance, if bed H were 

100 feet lower on the south side of Lignite Creek than 

is shown on plate 2, very little stripping coal would 

exist south of the creek. If it were 100 feet higher, 

the amount of stripping coal south of the creek would 

be much greater, although the amount in bed H would 

be less. No allowance was made in the computed 

reserves for these uncertainties.

Another factor that makes the calculation of 

stripping reserves uncertain is the burning of coal 

beds. The coal of the coal-bearing formation has been 

burning at one time or another since early in the period 

of deposition of the Nenana gravel, for fragments of 

burned shale can be found in the lower part of the 

Nenana gravel (Wahrhaftig, 1951, p. 178). The coal 

has been burning throughout much of Quaternary time 

and is on fire at two places on lower Lignite Creek 

today. Presumably the fires are the result of natural
Table 1. Analyses of coal on lower Lignite Creek

Bed

Basal

Basal

B

Sample 

no. 1

D-91188

D-9H90

D-91189

D-91191

D-91192

D-91193

26367

OfrffiQ txjyoy

Location

T\n*r cjeio c^

Tvrt? 1 Qd/^ c^ __ _ _

West bank Lignite Creek

in E^- sec. 35.

South bank Lignite Creek

at west border sec. 36.

South edge SW-jj- sec. 30,

T. 11 S., R. 6 W.

P.B.M.

WE1 -1 TOW 1 c^r* R _-_ - _____

NW1 NW 1 C^P "^R _ ________ -

Thickness 

sampled 

(in feet)

9.9

7.4

6

0 

.ti

15.4

8.5

20.1

Condition2

A.tt.

B

C

A.tt.

B

C

A

B

C

A

B

C

A

B

C

A

B

C

B

C

A.tt.

B

C

Moisture

o^T r\ 

tX) .0

27.4

27-6

26.1

26.8

21.9

25.30

23.83

Volatile 

matter

35-5

47.9

55-3

34-5

47-5

53-4

35.0

48.3

52.4

35-0

47.4

55.3

31.8

43.5

54-3

37.6

48.1

56.1

-*& nft yo . uo

48.30

52.51

35-55

46.67

55-19

Fixed 

carbon

28.6

38.8

44.7

30.1

41.4

46.6

31.6

43.7

47-6

28.4

38.4

44.7

2S.9

36.7

45-7

29.4

37-7

43.9

32.64

43.69

47.49

28.87

37-90

44.81

Ash

9.9

13.0

8.0

ll.l

i- O 5-o

8.0

10.5

14.2

14.5

19.8

ll.l

14.2

5

r\Q 

 9o

8.01

n n T'C 11.75

15-43

Sulfur

0.2

.2

 3

.2

 3

.3

.1

.2

.2

.2

.3

 3

.2

.3

 3

.2

.3

.3

o£ 

,cK>

 35

.38

.41

.54

.64

B

7

10

11

7

10

11

7

10

11

7

10

12

6

9

11

8

10

12

8 

10

11

7 

1 

9

10

1Samples D-91188 toD-91193 analysed by Roy F. Abernethy, chemist, U. S. Bureau of Mines, Pittsburgh, Penn. Samples 26367 and 26369 quoted from G. C. Martin

2Condition: A, as received; B, moisture free; C, moisture and ash free.
causes: lightning, forest fires, or spontaneous combustion. Probably 60 percent of the outcrops of the 

coal beds in this area have been burned, and it is 

likely that burning" is a major factor in the erosion of 

the coal beds, with very little coal being transported 

downstream.

Little is known of the extent of the burning, although some idea of the probable extent may be gathered from experience at the Suntrana mine on 

Healy Creek, where coal on the no. 3 bed was burned 

50 to 100 feet back from the outcrop (C. E. Garret, 

personal communication, 1944). The outcrops of 

beds E, F, and H appear to be largely burned out on 

the south side of Lignite Creek. However, exposures 

of coal in gullies less than 50 feet deep, on the south 

wall of the valley of Lignite Creek, are nearly always 

unburned, and exposures in the headwalls of landslides 

are usually unburned. It is thought likely, therefore, 

that the extent of burned coal is, at most, 50 to 100 feet 

back from the outcrop and probably averages much less 

than 50 feet. In computing reserves no allowance was 

made for possible loss of coal through burning.

Tlhe stripping-coal reserves on lower Lignite Creek 

are shown on table 2. Reserves are computed for each 

bed in each 640-acre section, except that on-the north 

side of Lignite Creek reserves in the N|Ni sec. 4, 

T. 12 S., R. 7 W., and in sec. 33, T. 11 S., R. 7 W., 

were computed as a unit, as were those in sees. 26 and 

35, T. US., R. 7W., and in sees. 25 and 36, T. US., 

R. 7 W., inasmuch as coal could not be mined in either 

section of these pairs without affecting the reserves in 

the other. Sec. 5, and the SWi and s|NWi sec. 4, 

T. 12 S., R. 7W. and sec. 32, T. US., R. 7 W., 

form a Government reservation (Martin, 1919, pi. 1). 

Consequently, the reserves in sec. 4 on the south side 

of Lignite Creek are broken into reserves in the west 

half, which lie in the Government reservation, and 

reserves in the east half, which lie outside the 

reservation.

Recommendations for future exploration

The main uncertainty about the stripping coal 

on the south side of Lignite Creek is the depth 

to the coal beds, and whether bed H lies just 

below the surface of the broad terrace south of 

the creek or has been removed by erosion. The 

presence of stripping coal in this bench could be 

proved by drilling. Because no water for core 

drilling is readily available on this plain, it is 

recommended that a power auger be used to test 

the coal. Two or three holes could be drilled 

in sec. 4, T. 12 S., R. 7 W., where bed H is 

covered by less than 100 feet of overburden. 

(See pi. 3.) If bed H is encountered a short 

distance below the surface or if the lithology of 

the sandstone indicates that bed H has been removed from this area (Wahrhaftig, Hickcox, and 

Freedman, p. 149-150), additional holes should 

be drilled 500 to 1,000 feet south of the first 

holes, to locate the outcrop of bed H. Once the 

outcrop has been determined, holes can be drilled 

farther south to determine the limits of stripping 

coal. A 100-foot hole drilled from the top of 

the bench in the E^SWi sec. 3, T. 12 S., 

R. 7 W., would probably test reserves of coal in 

beds E and F (pis. 4 and 5).

After the extent of stripping-coal reserves, particularly of bed H, has been determined, drilling of holes at 

selected locations along Lignite Creek could be used to 

check the accuracy of the strati graphic measurements; 

because on these would depend the accuracy of estimates 

of reserves of the lower beds, presumably out of reach of

Ta"ble 2. Reserves of stripping coal on lower Lignite 

Creek

Bed

Thickness 

overburden 

(in feet)

Thickness 

coal 

(in feet)

Area 

(acres)

Reserves 

(in millions 

of tons)

Sec. 3

H

G

F

F

E

E

A

Totalless than 100

about 100 I

less than 150

about 100 1

less than 50

about 50 l

less than 50 «

22

1).

30

30

19

19

60

32

10

67

5

70

80

2

1.1

.06

3.1

.2

2.1

2A

Q .1~~r\£i y '

Ei sec. k

E

E

G

F

F

E

E 

Tntal -

less than 100

100 to 200

about 100

less than 150

about 150 1

less than 50

about 50 l

22

22

k

30

30

17

17

53

k&

IQit

37

101).

22

136

1.8

1.6

.6

1.7

^.9

.6

.... ik*8n

and

H

H

G

F

F

E

E

less than 100

100 to 200

about 100 1

less than 150

about 150 l

less than 50

about 50 1

22

22

k

30

30

17

17

16

85

98

^

98

21

101).

0.55

2.9

.6

1.6

^.5

 55

2.8

Se'c. 5> part south of Lignite Creek

H

H

G

F

F

E

E 

Total--

less than 100

100 to 200

about 100 l

less than 150

about 150 1

less than 50

about 50 1

22

22

k

30

30

16

16

16

29

26

26

26

26

11

0.55

1.0

.2

1.2

1.2

.6

. __ _ <=,.<-«

Sec. 5j part north of Lignite Creek and Sec. 32

H

H

G

F

F

E

Total-.

less than 100

100 to 200

about 100 1

less than 150

about 150 1

less than 50

22

22

k

30

30

16

18

18

22

22

6

10

0.6

.6

.1

1.0

.3

.2

.___ 9 Rn

Sec. 33, and

E

E

G

F

F

E

E 

Total--

less than 100

100 to 200

about 100 I

less than 150

about 150 1

less than 50

about 50 1

22

22

k

30

30

16

16

32

^3

56

61

56

1^0

100

1.1

1.5

.35

2.8

2.6

1.0

2-2

 - 11 .RR

See footnotes at end of table.
Table 2. Reserves of stripping coal on lower Lignite 

Creek Continued

Bed

Thickness 

overburden 

(in feet)

Thickness 

coal 

(in feet)

Area 

(acres)

Reserves 

(in millions 

of tons)

Sec.

H

H

G

F

F

E

E

Totalless than 100

100 to 200

about 501

less than 150

about 1501

less than 50

about 50 ]

22

22

5

50

JO

20

20

^5

58

50

95

50

1*8

13J*

1.5

5.0

.1*

i*.i*

2.3

1.5

---- 18.70

sec. 35 and W^ sec. 26

H

H

G

F

F

E

E

Totalless than 100

100 to 200

about 50 1

less than 150

about 1501

less than 50

about 50 1

25

25

6

28

28

25

25

22

11

11*

2^

11*

21

50

0.9

.1*

.1

1.0

.8

.8

1.2

 5.2

sec. 35 and E-j sec. 26

H

H

G

F

F

E

B

Basal

Totalless than 100

100 to 200

about 50

less than 100

100 to 200

less than 100

less than 150

 

25

25

7

28

28

25

15

10

11*

11

51

15

51

5^

2k

15

0.6

a '?

.1*

.7

2 1.5

21.5

2 .6

.25

 6.05

Sec. and sec. 25

H

H

G

F

F

E

B 

Total100 to 200

less than 100

about 50

less than 100

100 to 200

less than 100

less than 150

28

28

7

25

25

25

15

27

25

37

20

57

52

22

1.5

1.2 2 .5

.9 21.6

22.5

-T&

Grand 

_________- - - total- 95.36

1 Overburden after next overlying thick bed has been mined.

2 Includes reserves beneath overlying beds, available when overlying 

beds have been removed.

the power auger on the plain to the south. Vertical holes 

drilled where each of the coal beds crosses Lignite Creek 

would determine the approximate distance to the next bed 

below. Churn or core drilling could be used for these 

holes, as water from Lignite Creek would be available.

The chief uncertainty regarding stripping coal 

on the north side of Lignite Creek west'of sec. 34, 

T. US., R. 7 W., is the extent to which the coal 

has burned. The area underlain by stripping coal, 

shown in plates 3, 4, and 5 is a steep hillside; the 

coal dips gently into the hillside, and it would be impracticable to test this coal by drilling. Deep trenching far in advance of development also would be impracticable. A possible method of testing would be to 

sink test slopes from the outcrops of the burned coal 

beds to determine the distance to which burning has

penetrated the bluff. Such slopes would require extensive timbering, because the broken and slumped 

ground above the burned coal beds' is very heavy. 

Probably the most practical way of testing in advance 

of mining would be to hydraulic narrow strips down the 

slope, spaced a quarter to half a mile apart, using 

equipment already installed for mining coal on the 

south side of the creek. Much of the coal in sees. 34, 

35, and 26, T. 11 S., R. 7 W., would also have to be 

tested for burning along steep slopes. However, the 

presence and condition of coal beneath the high flats 

in section 34 could be tested by power-auger drilling. 

Exposures in sees. 36 and 25, T. 11 S., R. 7 W., 

already indicate that strippable coal, sufficient to 

justify mining operations, exists in these sections.

FACTORS AFFECTING MINING OF THE COAL 

Nature of the overburden

The overburden of the coal beds, and particularly 

the strata between the coal beds, consists largely of 

poorly consolidated sandstone and claystone with pebbly 

layers. Most of this material is perennially frozen. 

Experience at the Usibelli, Suntrana, and Cripple Creek 

mines on Healy Creek shows that this material can 

be removed easily and profitably by hydraulicking if 

it is allowed to thaw between periods in which water 

is played on the sandstone (A. Shallit, personal 

communication). Overlying the coal measures are 

terrace gravels ranging in thickness from a few inches 

to 150 feet. Those on the south side of Lignite Creek 

are thinner than those on the north side; over most of 

the potential stripping area they probably average less 

than 15 feet in thickness. However, they are very 

coarse and would probably have to be removed by 

bulldozing. The thick gravels on the north side of 

Lignite Creek are derived mostly from Nenana gravel 

north of the coal-bearing area. Some of this material 

is fine enough to be removed by hydraulicking, but 

some of it also would have to be removed by bulldozing. 

If planning and foresight are used in the entire mining 

operation, the gravel removed by bulldozing could be 

stockpiled and used later as road-metal and ballast 

beneath railroads, roadways, and structures.

The giant glacial boulders that are common in 

this area will probably have to be blasted before they 

can be removed by bulldozer. Those close to Lignite 

Creek, however, may prove valuable as a local source 

of riprap.

Source of water for hydraulic stripping

The two possible sources of water are Lignite 

Creek and the Nenana River. All other streams in the 

area have too low a normal flow to be considered likely 

sources for the quantity of water that would be needed. 

Two rough measurements were made of the flow of 

Lignite Creek. Cross sections were measured by 

determining depth to bottom at measured intervals 

across both ends of selected straight courses. The 

duration of travel time of chips dropped on the water 

at the upper end of each course was then determined, 

and the average of five trips was used for each measurement. Bottom roughness was considerable; boulders 

were exposed above water surface in many places on 

the courses. To allow for this extreme bottom
roughness, the average velocity of the stream was 

assumed to be half the surface velocity. The first 

measurement was made at the east boundary of sec. 4, 

T. 12 S., R. 7 W., on July 5, 1952, 1| days after a 

heavy rain that lasted half a day. The flow of water 

was about 50 cubic feet per second. The second 

measurement was made just above the mouth of 

Popovitch Creek (in the E£ sec. 36, T. 11 S., R. 7 W.) 

on July 10, after a week of dry weather. The measured 

flow was about 20 cubic feet per second. Although these 

results are only approximate, they were taken during 

a period of high water on Lignite Creek, when snow 

was still melting near the headwaters, and probably 

indicate the maximum dependable water. From these 

measurements it does not appear that Lignite Creek 

would be a very dependable source of large quantities 

of water for hydraulicking.

The Nenana River offers a much more dependable 

source of water, as its normal flow is far greater than 

the requirements of hydraulic mining on Lignite Creek. 

A suitable site for a pumping station would be the low 

terrace near the southwest corner of sec. 5, T. 12 S., 

R. 7 W. The lift from this site to the top of the 

terrace in sec. 5, would be about 500 feet. From 

there it could be piped to stripping operations in 

sees. 3, 4, and 5, T. 12 S., R. 7 W., and sees. 33 

and 34, T. 11 S., R. 7 W.

Disposal of debris

The hydraulicked debris could be moved by 

sluices to Lignite Creek, and delivered by that stream 

to the Nenana River. In order to prevent the debris 

from silting up the channel of Lignite Creek, the stream 

will probably have to be deepened and confined between 

retaining walls. Under such a regime it should be able 

to handle most of the pediment gravels on the north 

side of Lignite Creek.

The effect of considerable amounts of debris on 

the regime of the Nenana River is hard to predict. 

Assuming an annual production of the Lignite Creek 

strip mines of 500,000 tons per year and an average 

ratio of overburden to coal of about 7:1, approximately 

80 to 90 million cubic feet of debris would be washed 

down Lignite Creek each year. This represents the 

removal of approximately 3^ feet from 1 square mile. 

Investigations now in progress indicate that the average 

rate of lowering of badlands in the Nenana coal field 

is about 1 inch per year, and that, throughout the 

Pleistocene, approximately half of the erosion of the 

Lignite Creek basin has been by badland erosion, the 

remainder being by other processes, such as lateral 

corrasion and landslides. Badlands in the Lignite Creek 

basin total 1^ square miles in area and contribute 

roughly 0.1 foot of material from that area per year. 

Thus the total amount of debris that is moved down 

Lignite Creek each year, if average conditions during the Pleistocene are assumed to prevail at the 

present time, is about 0. 2 foot from 1^ square miles, 

which is roughly equivalent to the removal of 0. 3 foot 

from 1 square mile. The delivery of more than 

10 times this amount of debris by hydraulic mining 

could have a serious effect on the regime of the 

Nenana River, possibly causing silting of the bed and 

channel changes on the alluvial fan of the river between Rex and Nenana. Such channel changes might 

seriously affect the Alaska Railroad, the Clear airport,

and the town of Nenana and its dock facilities. The effect 

of excessive debris delivered to the Nenana River 

through strip mining on Healy and Lignite Creeks and 

their tributaries can be appraised more accurately 

when sediment studies now being made of \ the Nenana 

River by the Geological Survey are completed.

Landslides

The extensive landslides along lower Lignite Creek 

have been described in an earlier section of this report. They are distributed along the walls of the 

canyons of Lignite Creek and its tributaries and cover 

approximately 11 percent of the area that is likely to 

be involved in strip mining (pi. 1). Landslides will 

affect coal mining on Lignite Creek in many ways. 

Where landslides have affected the coal beds they have 

probably rendered the upper beds unfit for mining 

increasing the thickness of overburden above lower 

coal beds. This Overburden, however, is already 

broken and is probably thawed and would very likely 

be moved easily by hydraulicking. The danger of 

landslides greatly restricts the area in which roads, 

railroads, and other installations may be built. This 

aspect of the landslide problem is considered in the 

following section on access to the coal field. The 

hydraulic method of stripping coal will probably increase the danger of. landsliding. Two kinds of 

landslide are possible: rock and debris falls from 

sandstone cliffs, and slumps along bedding planes. 

The first kind will be a natural and unavoidable consequence of the hydraulicking methods and could be 

deliberately induced to speed stripping; if desired, 

it can be kept to a minimum by keeping slopes in 

sandstone less than 45°. The second kind, slumps 

along bedding planes, could involve areas as large as 

40 acres or more. In order to reduce the danger of 

these slumps, the strip-mining operation should be 

planned so that all bedding planes on which sliding 

could take place would dip into the pit face. 

Lignite Creek flows along the axis of an anticline, 

and the beds for the most part dip away from 

the creek. Thus, it should be possible to keep 

bedding planes dipping into the pit face while 

strip mining is going on. The only places where 

the attitude of the beds is favorable to slumping 

on a large scale at present are in the SWi sec. 3, 

T. 12 S., R. 7 W., and the SW| sec. 34, 

T. 11 S., R. 7 W. As would be expected, these 

areas are already the sites of some of the most 

extensive landslides.

Badland erosion

Once the strip mines are abandoned, they 

will become the sites of extensive badlands, 

unless measures are taken to reforest them. 

The badlands will supply excessive amounts of 

debris to Lignite Creek and the Nenana River, 

and will also cause the erosion of valuable coal 

reserves. The coal beds, if left exposed, would 

be susceptible to burning. It is recommended 

that, as soon as strip mining in a given area 

has reached the limits of economic feasibility, 

the exposed edges of the coal beds be covered 

with a mixture of sand and clay and the hillsides graded and planted to forest or other suitable vegetation.

10
Access to the coal field

The shortest and most practical rail or road route 

to connect the coal field on lower Lignite Creek with 

the Alaska Railroad would extend from a point on the 

railroad about half a mile south of Lignite, cross the 

Nenana River at a point just north of Lignite Creek, 

and follow Lignite Creek to the coal deposits. Using 

this route, the coal deposits closest to the railroad 

would have a haulage of 1 to 1-J miles, and those in 

sees. 25 and 36, T. 11 S., R. 7 W., would have a 

haulage of 5| to 6 miles.

A road or railroad along Lignite Creek could be 

laid on the low gravel terraces which border the creek 

on one or both sides. It should be located so as to 

avoid, as much as possible, landslides and the danger 

of landslides. Several of the tributaries on the north 

side of Lignite Creek drain extensive badland areas 

and are subject to mudflows of the type that occur on 

Suntrana Creek at Suntrana. Mudflows are especially 

likely to occur on the creek in the Wi sec. 33, on the 

large creek that flows through sec. 34, on the creek 

in the west part of sec. 35, and on Popovitch Creek.

A broad low terrace on the north bank of 

Lignite Creek provides an excellent foundation 

for road or railroad from the crossing of the 

Nenana River eastward to the point where bed H 

crosses the creek. Opposite this stretch the 

south bank of the creek is an extensive landslide, 

the upper part of which is still active. In spite 

of the danger of mudflows from the tributary in 

section 33, the north bank of Lignite Creek is 

the best side for a route as far east as the 

middle of section 4. Landslides are common on 

the south bank and much of the south bank not

now sliding is kept from doing so only because it is 

perennially frozen, a condition that is not likely to continue after road excavations. Eastward from the middle 

of section 4 landslides are common on the north bank of 

Lignite Creek. A terrace 5 to 10 feet high on the south 

side of the creek provides a good route for a road. In 

the W^ sec. 3, a large landslide has moved northward 

over part of this terrace (pi. 1) but appears to have 

stopped moving, at least temporarily. The strip of 

terrace between the toe of the landslide and the creek 

is about 100 feet wide. Eastward from section 3 conditions affecting roadbuilding are about equal on both 

sides of the creek. The south bank is subject to rapid 

creep of fragments of Birch Creek schist and the north 

bank to mudflows and landslides in the Tertiary rocks.

As strip mining progresses, the natural difficulties affecting roadbuilding on this creek will be 

eliminated,- for the landslides will be hydraulicked 

away. For this reason it may be desirable to develop 

the coal deposits of this creek progressively from the 

mouth of the creek eastward and to extend the road or 

railroad only as far as mining has eliminated the 

landslides and other troublesome factors.

LITERATURE CITED

Martin, G. C., 1919, The Nenana coal field, Aliska:

U. S. Geol. Survey Bull. 664, 54 p. 

Wahrhaftig, Clyde, Hickcox, C. A., and Freedrian,

Jacob, 1951, Coal deposits on Healy and Ligni

Creeks, Nenana coal field, Alaska: U. S. Geol. 

Survey Bull. 963-E, p. 141-165.

Wahrhaftig, Clyde, 1951, Geology and coal depo 

the western part of the Nenana coal field, Alas 

U. S. Geol. Survey Bull. 963-E, p. 169-186.

its of 

ka:

11 IHT.-DUP. SBC., WASH., D.C. 5m, 45
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY CIRCULAR 310 PLATE 1

149" 00' R.7 W. 148*55' I48C 50'

U. S. "GOVERNMENT PRESERVATION

EXPLANATION

Deposits of sand and gravel on river

flood plains or In recently built alluDeposlts of gravel mantling terraces

and pediments along the Nenana River,

Lignite Creek, and their tributaries

UNCONFORMITY

63 C 55'

I49C 00'

Base from U. S. Geological Survey maps 

of Healy D-4 (1952) and Healy D-5 

quadrangles, Alaska

R.7 W. I48C 55'

2 MILES

' ' -I I I

I 4 8° 50'

Geology by Clyde Wahrhaf tig, J. H. 

Birman, and C.A. Hickcox. 

Surveyed in 1945 and 1952

5OOO IO.OOO FEET

CONTOUR INTERVAL 100 FEET

DOTTED LINES REPRESENT HALF-INTERVAL CONTOURS 

Datum is mean sea level

Nenana gravel

Coarse brown poorly consolidated con' 

glomerate with scattered sand lenses

APPARENT CONFORMITY

Interbedded buff-colored arkoelc sandstone, In part pebbly clay stone, and thin

coal beds. Granite, volcanic rocks, greenstone, and conglomerate common as pebbles

Middle member

Interbedded salt- and-pepper sandstone,

thick coal beds, and claystone.

chert, quartzlte, and argllllte make up

 Interbedded sandstone,

claystone. and coal. Coal beds lenticular

and discontinuous.

weathering claystone at top

UNCONFORMITY

rch Creek schist

Greenish-gray to black quartz-serlclte

Landslides

Contact 

(Dashed where position approximate)

Indefinite contact

Fault

(Dashed where approximately located; 

dotted where concealed by alluvium. 

U, upthrown side; D, downthrown side)

Anticline

(Showing trace of axial plane and direction of plunge of axis

Dashed where approximately located; 

dotted where concealed)

Syncline

(Showing trace of axial plane and direction of plunge of axis

Dashed where approximately located; 

dotted where concealed)

Strike and dip of beds

90 

Strike of vertical beds

Strike and dip af overturned beds

Horizontal beds

Position of measured section .(See fig. 2)

APPROXIMATE MEAN 

DECLINATION 1951

GEOLOGIC MAP OF THE VALLEY OF LOWER LIGNITE CREEK, NENANA COAL FIELD, ALASKA
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

CIRCULAR 310 PLATE 2

149° 00' R.7 W. 148° 55' 148*

U. S. "GOVERNMENTS RESERVATION

63° 55*

14 9° 00'

Base from U S. Geological Survey maps 

of Healy D-4 (1952) ond Healy D-5 

quadrangles, Alaska

CONTOUR INTERVAL 100 FEET

DOTTED LINES REPRESENT HALF-1NTERVAL CONTOURS 

Datum Is mean sea level

APPROXIMATE MEAN 

DECLINATION I9SI

EXPLANATION

Structure contour on top of Bed H 

(Dashed where position uncertain)

(Contour interval IOO feet. Datum 

is mean sea level.)

Fault

(U, upthrown s/efg/ D, downthrown side.)

Trace of outcrop of BedH 

(Solid where exposed or where 

clinker indicates position; dashed where concealed by soil and 

vegetation; dotted where concealed by terrace gravel)

STRUCTURE-CONTOUR MAP OF BED H, LOWER LIGNITE CREEK, NENANA COAL FIELD, ALASKA
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

CIRCULAR 310 PLATE 3

R.7 W.

MmwmmM

R. 7 W. r 1'°

9OOO

^

10,000 FEET

EXPLANATION

Areas of stripping coal in bed H, 

overlain by less than 100 feet 

of overburden

Areas of stripping coal in bedH, 

overlain by 100-200 feet of 

overburden

Areas of stripping coal in bed B, 

overlain by less than 150 feet 

of overburden

Areas of stripping coal in bed B, 

which will be overlain by 150 

feet of overburden after bed 

E has been mined

Areas of stripping coal in the 

basal bed

Outcrop of bed H, showing 

thickness of measured section

^- is.e'

Outcrop of bed B, showing 

thickness of measured section

Exposure of basal bed, showing thickness

xxxxxx

Clinker observed along line of 

outcrop of bed H

APPROXIMATE MEAN 

DECLINATION 1991

AREAS OF STRIPPING COAL IN BEDS H AND B AND THE BASAL BED ON LOWER LIGNITE CREEK, NENANA COAL FIELD, ALASKA
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

CIRCULAR 310 PLATE 4

R.7 W.

U. S. Government R»«»rvotlon

EXPLANATION

Areas of stripping coal in bed F, 

overlain by less than 150 feet 

of overburden

Areas of stripping coal in bed F, 

which will be overlain by about 

150 feet of overburden after 

bed H has been mined

Outcrop of bed F, showing 

thickness of measured section 

(Solid where exposed; dashed 

where Inferred)

Clinker observed along line 

of outcrop of bed F

APPROXIMATE MEAN 

DECLINATION 1951

AREAS OF STRIPPING COAL IN BED F ON LOWER LIGNITE CREEK, NENANA COAL FIELD, ALASKA
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

CIRCULAR 310 PLATE 5

R.7 W.

EXPLANATION

Areas of stripping coal in bed E, 

overlain by less than 100 feet 

of overburden

Areas of stripping coal in bedE, 

which will be overlain by 50- 

100 feet of overburden after 

bed F has been mined

Outcrop of bed E, showing 

thickness of measured section 

(Solid where exposed; dashed 

where inferred)

Clinker observed along line 

of outcrop of bed E

APPROXIMATE MEAN 

DECLINATION I9SI

AREAS OF STRIPPING COAL IN BED E ON LOWER LIGNITE CREEK, NENANA COAL FIELD, ALASKA