B08_ATT_6_Geological_Survey_Professional_Paper_305I_Fish_Creek.pdf

Core Test, Sentinel Hill

Area, and Test Well

Fish Creek Area, Alaska

EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4

AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53

PART 5, SUBSURFACE GEOLOGY AND ENGINEERING DATA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 305-1

Prepared and published at the request oj and in cooperation with the U. S. Department oj the Navy, Office oj Naval Petroleum and Oil Shale Reserves

Core Test, Sentinel Hill I

I Area and Test Well t I r

I

! Fish Creek Area, Alaska By FLORENCE M. ROBINSON and FLORENCE RUCKER COLLINS

EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4

AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53

PART 5, SUBSURFACE GEOLOGY AND ENGINEERING DATA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 305-1

Prepared and published at the request 0; and in cooperation with the U. S. Department of the Navy, Office of Naval Petroleum and Oil Shale Reserves

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1959

UNITED STATES DEPARTMENT OF THE INTERIOR

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY

Thomas B. Nolan, Director

The U. S. Geological Survey Library has cataloged this publication as follows:

Robinson, Florence Marie, 1921- Core test, Sentinel Hill area, and test well, Fish Creek area, Alaska, by Florence M. Robinson and Florence Rucker Collins. Washington, U. S. Govt. Print. Off., 1959.

iii, 485-522 p. mus., maps, diagrs. (2 in pocket) tables. 31 cm.

(U. S. Geological Survey. Professional paper 305-1. Exploration of Naval Petroleum Reserve No.4 and adjacent areas, northern Alaska, 1944-53, pt. 5, Subsurface geology and engineering data)

In cooperation with the U. S. Dept. of the Navy, Office of Naval Petroleum and Oil Shale Reserves.

(Omtinued on next card)

Robinson, Florence Marie, 1921- (Card 2)

Bibliography: p. 520.

Core test ... 1959.

1. Borings-Alaska. 2. Petroleum-Alaska. 3. Geology-Alaska Arctic Coastal Plain. I. Coll:ins, Florence Rucker, joint author. n.

Title. (Series: U. S. Geological Survey. Professional paper 305-1.

Series: U. S. Geological Survey. Exploration of Naval Petroleum Reserve No.4 and adjacent areas, northern Alaska, 1944-53, pt. 5)

622.3382

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price $1 (paper cover)

CONTENTS

Abstract __________________________________________ _ Introduction ______________________________________ _

Sentinel Hill core test 1, by Florence M. Robinson _____ _ Stra~graphy-----------------------------------

Upper Cretaceous-Colville group ___________ _ Prince Creek formation, Kogosukruk tongue_ Schrader Bluff formation, Sentinel Hill member ____________________________ _

Description of cores and cuttings ________________ _ Core analyses- ________________________________ _ Oil and gas ___________________________________ _ Logistics ______________________________________ _ Drilling operations _____________________________ _

Fish Creek test well 1, by Florence R. Collins _________ _ Structure _____________________________________ _ Stratigraphy __________________________________ _

Gubik formation ___________________________ _ Schrader Bluff formation ___________________ _ Prince Creek formation, Tuluvak tongue ______ _

Page

Fish Creek test well 1, by Florence R. Collins-Con.

Seabee formation __________________________ _ Topagoruk formation _______________________ _

Description of cores and cuttings ________________ _ Core analyses _________________________________ _ Oil and gas ___________________________________ _

Oil and gas shows __________________________ _ Formation tests ___________________________ _ Oil, gas, and water analyses- ________________ _

Logistics ______________________________________ _

Drilling operations _____________________________ _ Drilling notes _____________________________ _ Drill and core bits _________________________ _ Drilling mud ______________________________ _ Hole deviation ________________ - - __________ _ Electric-log and velocity surveys---- _________ _

Literature cited ____________________________________ _ Index ____________________________________________ _

ILLUSTRATIONS

[plates 31 and 32 are In pocket]

PLATE 31. Graphic log of Sentinel Hill core test 1.

32. Graphic log of Fish Creek test well 1.

Page

Page

33. Sentinel Hill core test L ____________________________________________________ - __ - - - - - - _ - - - - - - - ___ Faces 486

34. A, Oil seep near Fish Creek test well 1; B, Section of core from Fish Creek test well L _________________ Faces 487

FIGURE 39. Index map of northern Alaska showing test wells and oil fields____________________________________________ 485

40. Map showing location of Sentinel Hill core test 1 and structure-contour lines, in the surrounding area, drawn on phantom seismic horizon "A," equivalent to sandstones in the Cretaceous________________________________ 487

41. Columnar section, Sentinel Hill core test L____________________________________________________________ 488

42. Relative abundance of heavy minerals in Sentinel Hill core test 1 and Fish Creek test well L _ _ ______________ 499

43. Observed gravity in the vicinity of Fish Creek test well L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 502:

fiX

EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4 AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53

CORE TEST, SENTINEL HILL AREA, AND TEST WELL, FISH CREEK AREA, ALASKA

By FLORENCE M. ROBINSON and FLORENCE R. COLLINS

ABSTRACT

Sentinel Hill COre test 1 and Fish Creek test well 1 were drilled in 1947 and 1949, respectively, as part of the petroleum exploration of Naval Petroleum Reserve No.4, northern Alaska, carried on by the U. S. Navy from 1944 to 1953. Fish Creek test well 1 is near an oil seep in the northeastern corner of the Reserve, which is in the Arctic coastal plain province; and Sentinel Hill is about 50 miles to the south. Both holes were drilled into the youngest Cretaceous (the uppermost divisions of the Late Cretaceous Colville group) formations found in northern Alaska, and Fish Creek test well 1 penetrated several older Cretaceous formations, as well. The strata are composed primarily of clay shale, with some sandstone and siltstone;

most of the section is marine. Tuffaceous beds and bentonite are abundant in the upper part of the sequence. The 7,020-foot test well at Fish Creek recovered a small amount of heavy black oil, but the core test, a much shallower hole, had no oil or gas shows.

168'

EXPLANATION

Gas well

Abandoned well

70' Ory hole

68'

1 SOUTH BARROW TEST WELL 1

2 SOUTH BARROW TEST WELL 2

3 SOUTH BARROW TEST WELL 3

.4 SOUTH BARROW TEST WELL .4

5 AVAK TEST WELL 1

e NORTH SIMPSON TEST WELL!

164' 160'

C C '1'

It

B ROO

7 SIMPSON TEST WELL 1

8 TOPAGORUK TEST WELL t

9 EAST TOPAGORUK TEST WELL 1

10 FISH CREEK TEST WELL 1

11 KAOLAK TEST WELL. 1

12 MEADE TEST WEL.L t

100 , INTRODUCTION

A program of petroleum exploration was conducted in Naval Petroleum Reserve No.4, northern Alaska, by the U. S. Navy, between 1944 and 1953. Among the holes drilled to help evaluate petroleum possibilities were Fish Creek test well 1 and Sentinel Hill core test 1, both of which penetrated Cretaceous rocks near the eastern edge of the Reserve. The test well, 7,020 feet deep, is on the Arctic coastal plain near the Arctic Ocean (see fig. 39), and the comparatively shallow core test is 50 miles to the south, near the southern boundary of the coastal plain. Fish Creek test well 1, near an oil seep, recovered a little heavy black oil;

Sentinel Hill core test 1, on the flank of the Sentinel Hill anticline, was a dry hole.

156' 152'

0 C E A

......... '" ··;~;IO~ ..... ••• ··c ~ ., ......... Vi 1<

13 OUMALlKTESTWElL 1

14 EAST OUMALIK TEST WELL 1

15 SQUARELAKETESTWEll'1

16 TITALUK TEST WELL 1

17 WOLF CREEK TEST WEll 1

18 WOLF CREEK TEST WELL 2

r R 0 . ~'

19 WOLF CREEK TEST WEll 8

20 GUBIK TEST WELL. 1

21 GUBIK TEST WELL 2

22 KNIFEBLADE TEST WELL 1

23 KNIFEBLADE TEST WELLS 2 AND 2.\

24 GRANDSTAND TEST WELL 1

25 UMIAT TEST WELLS 1-11

FIGURE 39.-Index map of northern Alaska showing location of test wells and oil fields.

486 EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

Detailed geologic, engineering, and logistic data ob tained from drilling these two tests are presented in this report, and much of it is summarized on graphic logs. The .report has been compiled from information supplied, under contract, to the Navy by Arctic Con tractors, United Geophysical Co., Inc., and the Schlum berger Well Surveying Corp., and by the U. S.

Geological Survey, the U. S. Bureau of Mines, and the National Bureau of Standards as cooperating Gov ernment agencies. Geologists of the Geological Survey described the cores and ditch samples and determined porosity and permeability in the Survey's laboratory in Fairbanks, Alaska; Paul D. Krynine also made porosity and permeability studies. Invertebrate mega fossils were identified by George Gryc and C. Wythe Cook, and plant fossils were studied by Roland Brown.

Microfaunal studies were made by Harlan R. Berg quist. The stratigraphic distribution of fossils in the test wells of northern Alaska will be presented by him in another chapter of this series. The heavy-mineral data is part of a regional study of the heavy-mineral zones by Robert H. Morris. The help of many other engineers, geophysicists, and geologists connected with the above organizations is gratefully acknowledged.

SENTINEL HILL CORE TEST 1

By FLoRENCE M. ROBINSON

Location: Lat 69°36'57" N., long 151 °27'11" W.

Elevation above sea level: Kelly bushing, 209 feet; ground, about 200 feet.

Spudded: January 26, 1947.

Completed: March 23, 1947; dry and abandoned.

Total Depth: 1,180 feet.

Sentinel Hill core test 1 was located on the west side of the Colville River 24 miles northeast of Umiat (see fig. 40) ; the core test is 12 miles due north of Gubik test well 1 which is shown on figure 39. The site chosen was on a mud and gravel bar a few feet above water level and at the base of 350-foot bluffs. This bar is probably covered with water during the breakup in late spring and early summer.

Sentinel Hill, a topographic feature 18 miles north of the core test and near the mouth of the Kogosukruk River, was named by F. C. Schrader and W. J. Peters, of the U. S. Geological Survey, on their traverse down the Colville River in 1901 (Schrader and Peters, 1904).

The term "Sentinel Hill area" was first used in a report made in 1945 to the U. S. Navy (unpublished) by one of their reconnaissance geologic field parties led by Lts.

J. A. Rogers and A. P. McConnel, Jr. The area covered by this party was mostly northwest of the site of the core test and along the Kogosukruk and Kikiak rorak Rivers. Toward the end of the season, however, they made a short study along about 10 miles of the Colville River. They recognized a broad, low anti clinal fold with several crests which they presumed ex tended from the Kogosukruk River to the Colville River. (See fig. 40.)

In 1945 and 1946 the U. S. Geological Survey in con junction with the U. S. Navy made a survey of the Reserve with an airborne magnetometer. A magnetic high which was called West Sentinel Hill was dis covered north-northwest of Umiat, but this was cen tered about 30 miles from the Sentinel Hill core test site. (See fig. 8, Payne and others, 1951, sheet 2.) A gravity maximum mapped by United Geophysical Co., Inc., coincides with the magnetic high. (See fig. 9, Payne and others, 1951, sheet 2.)

Sentinel Hill core test was drilled early in 1947 by Arctic Contractors. Later, in the summer of 1947, a U. S. Geological Survey field party under K. Stefansson studied the surface geology on the Colville River north of Umiat and on the Kogosukruk River. In 1950 a re flection seismograph tie-line run between the Fish Creek area and Umiat by United Geophysical Co., Inc., showed a reversal in this vicinity and helped to define the Sen tinel Hill anticline. Some seismic detail work was done in the area in 1951. The contour lines on figure 40 show possible closure on the anticline 13 miles northwest of the core test.

In 1954 W. P. Brosge, of the U. S. Geological Survey compiled the field and photogeologic data and deter mined the position of the anticlinal and synclinal axes shown on figure 40. The Kogosukruk tongue of the Prince Creek formation (see section on stratigraphy) of Late Cretaceous age crops out in the area (W. P.

Brosge, written communication).

The purpose of the core test was "* * * to ascertain the nature of the shallow subsurface formations on the Sentinel Hill anticline and test shallow oil possibilities" (written communication, Arctic Contractors, March 1953). Stratigraphically, the test provided valuable information but the present structural data indicate that the core test is actually far out on the flank of the anticline and in a relatively low area between two of the axial flexures. No gas or oil was found.

STRATIGRAPHY

UPPER CRETACEOUS-COLVILLE GROUP

The rocks penetrated by Sentinel Hill core test 1 are interbeds of the nonmarine Kogosukruk tongue of the Prince Creek formation and of the marine Sentinel Hill member of the Schrader Bluff formation. (See pI. 31.)

The tongue and the member are the age equivalents of the uppermost part of the Colville group of Late Cre taceous age. The type sections of the Schrader Bluff

1'IWFE,,:';ll':-;AL PAPER 30.:J PLATE :1:>

.. , ·f

SE'XTI,EL III LL .. OIlE TE~T ) tOo.

GEnLOGICAL ~rRYEY

A. OIL SEEP NEAR FISll CREEK TEST WELL 1

Dark oil-impregnated sand rim~ the depreRsioll, which is partl) filletl with water on which black ViSCOIiF oil is floating. Snow4"overf'd clumps of grass and mOIS surround the seep. Septemher 17l 1947.

11. ~F.CTIO" (I'" CUIIE FHlHI F1~"

CIIEEJ..: TE:'T WELL I

I )i~torlerl herlflin~ ill ,I ('Orf' from fJ.,n I ft·('t.

as,1 "'- I .5 1\ b. ~ ~I ) / / /' ~ 1/- ---.......ji/;;{{I ""II)!" 13.

152G SO' 40' 151-3)'

Base map compiled by U. S, Geological Survey Structure contour by United Geophysical Co" 1951.

from trimetrogon oeriol photographs 4 Miles Structural axes mapped by Us. J,A. Rogers and

, ' A.P. McConnell, Jr., U.S. Navy. 1945 and by K, Anlicllne, approximalely lacaled

E X P LAN A T ION Stefansson,1947; Revised by W,P, BIOsge, 1954

+ ----04000---? ____ 4-

Syncline, approximately located Seismic structure-contour lines, approximately located. queried where inferred. Contour interval 100 feet; datum is mean sea level

Dry hole

]\'J(lURE 40.-MRP showin~ location of Sentinel Hill core test 1 and structure-contour lines, in the surronnding area, drawn on phantom seismic horizon "A," equivalent to sandstones In the Cretaceous, Nanushuk group. Letters A through Fl indicate the flexures originRlly recognized by the Navy geologic field party In 194'5.

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C':l t':J p:j

Ul

H:>-

I i i

I

I I I, 488 EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

and Prince Creek formations were described by Gryc, Patton, and Payne (1951). Originally, Sentinel Hill core test 1 was designated as the type section of the Sentinel Hill member, but C. L. Whittington (1956) re defined the member and described a new type locality on the Colville River about 10 miles south of the core test.

The thicknesses of these formations in Sentinel Hill core test 1 are indicated in figure 41. The

FIGURE 41.-Columnar section, Sentinel Hill core test 1.

interfingering of the beds is more complex than this simple chart indicates. However, the Kogosukruk tongue as described below is predominantly nonmarine and the Sentinel Hill member is predominantly marine.

The formations are differentiated largely on a correla tion by William P. Brosge (written communication) with the outcrop and on the presence of macrofossils and microfossils as indicators of marine beds. Coal is an important factor in recognizing the nonmarine sections.

PRINCE CREEK FORMATION, KOGOSUKRUK TONGUE

The beds of the Kogosukruk tongue from 9 to 469 feet and from 840 to 949 feet make up approximately one-half of the total sequence drilled in the core test.

The Kogosukruk tongue is mostly clay shale or clay stone which ranges from light-gray and light-olive gray to dark-gray. Claystone, medium-hard and with irregular fracture, is more common than the slightly softer bentonitic and carbonaceous clay shale which breaks easily parallel to the bedding. Some of the claystone is silty and some is moderately to very cal careous. In places the claystone grades to brownish clay ironstone.

Only about 25 percent of the Kogosukruk tongue as found in this test is sandstone and siltstone. The sand stone is light gray and ranges from medium soft with an argillaceous matrix to hard with a calcareous matrix.

The grain size ranges from fine to medium, and the grains are composed of about 50 percent of clear quartz, with some white quartz. The remainder of the grains are rock fragments, white mica, black carbonaceous particles, volcanic glass shards, and chert. They are cemented by argillaceous, bentonitic, or in places cal careous or sideritic material. A more detailed descrip tion of one sandstone sample from 345 feet by P. D.

Krynine may be found on p. 498. At 882 feet the sandstone contains a layer of rounded gray and black chert granules and pebbles as large as one-half an inch in diameter.

The siltstone is similar to the sandstone. At some depths it is soft and has good shaly cleavage, and at others it is massive, hard, and calcareous. Both the siltstone and the sandstone contain plant fragments.

The average effective porosity ofthe sandstone is 24 per cent, and ranges from 9.2 to 31.1 percent; the air perme ability ranges from 5.2 to 348 millidarcys. There were no shows of oil or gas in these sandstones or siltstones.

One lO-inch bed of limestone is present at 176 feet, and this is pale to dark yellowish brown, very hard, and dense, and has conchoidal fracture, and it may be very sideritic. Clay ironstone lenses and nodules are fairly common, particularly in the upper part of the tongue.

Ten percent of the formation is lignite, coal, or black carbonaceous shale. The lignite is rather soft, dull, and brownish and grayish black, and the coal is medium hard, dull to shiny, black, and brittle and has blocky fracture. Plant fragments and carbonaceous particles are present throughout the tongue.

Bentonite is finely disseminated in the clays and matrix of the siltstone and sandstone as well as in individual beds that are up to 2 feet thick. It is white, very light gray, light yellowish, and gray or brownish gray, and is hard when dry, fractures irregularly, and contains rare biotite plates, glass shards, or carbona ceous particles. The bentonite and the clay shale and sandstone containing it swell into an unctuous mass when moistened with water.

The diversified nature of the Kogosukruk tongue of the Prince Creek formation is characterized by thin beds with much variation from one type of rock to an other, the abundance of coal and carbonaceous plant material, and the absence of marine fossils.

SCHRADER BLUFF FORMATION, SENTINEL HILL MEMBER

In this core test the Sentinel Hill member of the Schrader Bluff formation is found between 469 and 840 feet and from 949 to 1,180 feet, total depth. Unlike the Kogosukruk tongue of the Prince Creek formation, it is just slightly more than half clay shale and claystone.

In this member, clay shale is a little more common than claystone. This argillaceous rock is medium light

CORE TEST, SENTINEL HILL AREA, AND TEST WELL, FISH CREEK AREA, ALASKA 489

gray-or rarely light olive gray where sideritic or dark gray where carbonaceous. In general it is medium hard and has fair to good cleavage along bedding planes. Most of it is noncalcareous, but it is very cal careous or sideritic in a few places.

Sandstone and siltstone make up about 45 percent of the Sentinel Hill member drilled here. These clastic units together are massive, as much as 100 feet thick, and are light gray or very light gray. Except where calcareous and hard, the sandstone and siltstone are rather soft and friable. The grain size ranges from silt to medium sand. The grains, which are angular to subangular, are composed of 70-85 percent of white and clear quartz with carbonaceous particles, muscovite and biotite, rock fragments, sideritic particles, and pyrite in an argillaceous or bentonitic matrix.

The composition of the grains in the siltstone is the same as in the sandstone, but the siltstone tends to be a little harder and more calcareous than the sandstone in the upper part of the member. The siltstone near 1,060 feet is light colored and has a very bentonitic matrix.

The effective porosity of 28 sandstone samples tested ranges from 15.2 to 29 percent (see table on p. 498) and averages 22.6 percent. The air permeability in the same samples ranges from less than 10 to 290 millidarcys.

The porosity and the permeability in the upper part of the formation are consistently higher than in the lower.

These rocks would probably make poor reservoirs, how ever, because they contain so many clay minerals that the potential hydration is high.

Coal is not common in the Sentinel Hill member al though beds of carbonaceous clay shale as much as 5 feet thick are found. Carbonaceous plant remains are found in both the clay shale and the sandstone but are par ticularly uncommon in the lowest part of the member.

Bentonite is about as abundant as in the Kogosukruk tongue. It is found in beds ranging in thickness from 1 inch to 5 feet; it is white, very light gray, or greenish gray and is rather hard, has subconchoidal fracture, and contains tiny biotite plates.

Plant fragments in the core from 822-826 feet are, according to Roland W. Brown, chiefly dicotyledons but not further identifiable. George Gryc identified M ytilu8 sp., a marine pelecypod, in a sample at 603 feet.

One gastropod, the fresh-water genus Lymnaea? sp., at 524Y2 feet was identified by C. Wythe Cook. At several depths in the Sentinel Hill member there are numerous nacreous pelecypod shells which are too frag mentary to identify. The formation is primarily marine, however, as indicated by the presence of a marine microfauna typical of the Colville group of Late Cretaceous age. E oeponidella 8trombode8 Tappan

466355-59-2 is characteristic of the Sentinel Hill member (Tappan, 1951, p. 6).

DESCRIPTION OF CORES AND CUTTINGS

The core recovery from Sentinel Hill core test was very good. The cores were originally described by William N. Lockwood, of the U. S. Geological Survey, in 1947 and were redescribed by the author in 1954 to conform in style with the other descriptions in this pro fessional paper series. All samples were described dry;

colors were determined with the aid of the National Research Council Rock Color Chart (Goddard and others, 1948). The term "trace" as used here is defined as less than 3 percent and usually represents less than 1 percent. Clay ironstone is a sideritic, dense, and rather hard mudstone that effervesces generally very slowly in cold dilute hydrochloric acid.

The latitude and longitude of the core test are based on preliminary topographic surveys and are subject to correction. All depths were measured from the kelly bushing. The height of the kelly bushing above sea level is estimated.

Lithologic description

[Where no core number Is listed, description Is based on cutting samples]

Core Depth (feet) Remarks

0- 9 Kelly bushing to ground level.

9- 19 Clay shale, dark-gray, carbonaceous;

trace medium-light-gray clay shale;

trace coal.

19- 29 Clay shale, 90 percent medium-dark-gray, 10 percent medium-light-gray; trace coal.

29- 39 Clay shale, 80 percent medium-dark-gray, 20 percent medium-light-gray.

39- 49 Clay shale, 90 percent medium-gray- to medium-dark-gray; 10 percent white bentonite.

49- 59 Clay shale, 60 percent, medium-gray to medium-dark-gray; 40 percent pale yellowish-brown slightly calcareous clay ironstone.

59- 69 Clay shale, 50 percent medium-dark-gray, 20 percent medium-gray; 30 percent pale-yellowish-brown clay ironstone.

69- 79 Clay shale, 80 percent medium-dark-gray, 10 percent medium-gray; 10 percent yellowish-brown clay ironstone.

79- 89 Clay shale, 90 percent medium-light-gray, 10 percent dark-gray; trace clay iron stone.

89- 99 Clay shale, 80 percent medium-gray and medium-dark-gray; 20 percent pale yellowish-brown clay ironstone.

99-109 Clay shale, 50 percent medium-dark-gray, 20 percent medium-gray; 30 percent clay ironstone.

Core

EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

Lithologic de8cription-Continued

Depth:(feet) Remarks

109-119 Recovered 8 ft.

2 ft 4 in., clay shal~, medium-light-gray, medium-hard, noncalcareous, slightly micaceous; fair cleavage; very rare carbonaceous fragments; beds lie flat.

10 in., clay shale, medium-dark-gray;

contains numerous very thin laminae (one-sixteenth inch) of brittle coal.

4 in., coal, black, dull to shiny; vertical fracture planes coated with brownish layer.

4 ft, claystone, medium-light-gray, slightly silty, noncalcareous, medium hard; irregular fracture; rare carbo naceous fragments; contains light gray bentonitic layers in top foot.

6 in., clay shale, carbonaceous; low grade coal.

119-129 Recovered 10 ft.

1 ft 5 in., clay shale, light-gray, very soft, bentonitic; a few chips of coal.

2 in., clay shale, very carbonaceous;

medium-hard brittle low-grade coal.

3 ft, claystone and clay shale, light gray, slightly silty, noncalcareous;

abundant medium-dark-gray carbo naceous partings; bedding irregular but beds lie approximately flat.

1 ft, clay shale, medium-dark-gray, carbonaceous; I-in. coal bed.

2 ft 5 in., claystone and clay shale, light-gray, bentonitic, medium-soft;

carbonaceous plant fragments.

2 ft, siltstone, light-gray, very argill aceous and micaceous, bentonitic, medium-hard; carbonaceous plant fragments present.

129-139 Recovered 8 ft.

7 in., clay shale, medium-light-gray, very soft; streaks of coal broken by drill.

3 ft 5 in., interbedded clay shale and siltstone, light- to medium-light gray, medium-hard, non calcareous, bentonitic, thin-bedded; fair cleav age; scattered carbonaceous plant fragments.

4 ft, clay shale, medium-gray, medium hard; fair cleavage; a few silty part ings and laminae; some crossbedding.

139-149 Recovered 6 ft.

1 ft 8 in., clay shale, soft; broken by drill.

1 ft 8 in., clay shale, light-gray, non calcareous, bentonitic, medium-hard;

fair cleavage.

5 in., low-grade coal, black, dull, brittle;

blocky fracture.

Core

Lithologic de8cription-Continued

Depth (feet) Remarks

2 ft 3 in., clay shale as above in this core, quite silty, non calcareous,' ben tonitic; grades in places to siltstone.

149-159 Recovered 10 ft.

4 ft 9 in., sandstone, light-gray, very fine-grained, medium-soft; grains sub angular; 50 percent clear with a little white quartz; 40 percent white mica;

remainder is mostly carbonaceous flecks and light-brown rock particles;

argillaceous-bentonitic matrix. Con tains about a foot of hard yellowish gray very calcareous sandstone ill middle. Calcareous rock contains numerous dark-brown and black plant fragments; no oil or gas shows.

5 ft 3 in., siltstone, light-gray, noncal careous, very argillaceous, medium hard; fair cleavage; grades in streaks to medium-light-gray clay shale;

beds lie flat.

159-169 Recovered 10 ft.

Siltstone as above; upper 5 ft of recov ery moderately to very calcareous;

lower half essentially noncalcareous.

169-179 Recovered 8 ft.

6 ft 7 in., siltstone, light-gray to light olive-gray micaceous, very argilla ceous; medium-soft to medium-hard;

sandy partings; has brownish blotches (sideritic material ?).

10 in., limestone (and some clay iron- .

stone), pale- to dark-yellowish brown, very hard, dense; conchoidal fracture.

7 in., siltstone as above; good cleavage.

179-189 Recovered 10 ft.

Clay shale, light-gray, light-olive-gray, and yellowish-brown, very calcar eous, medium-hard; good to excellent cleavage parallels bedding; numerous silty and sandy laminae; carbona ceous partings ; dip 4°.

189-199 Recovered 7 ft.

4 ft 8 in., Interbedded light-gray silt stone 60 percent; sandstone 20 per cent; and grayish-yellow clay shale 20 percent, medium soft, very cal careous. Sandstone is very fine to fine grained, contains clear quartz, a large amount of yellow calcite grains, carbonaceous particles, mica, and argillaceous material. Numer ous dark-gray carbonaceous partings.

Dip 4°.

2 ft 4 in., Sandstone, light-gray, hard;

composition as above; very cal careous matrix; very "dirty."

CORE TEST, SENTINEL HILL AREA, AND TEST WELL, FISH CREEK AREA, ALASKA 491

Lithologic desoriptio_Continued

Depth (feet) Remarks

199-209 Recovered 8 ft.

2 ft 5 in., claystone, medium-light- to light-olive-gray, medium-hard grades down into unit below.

10 in., clay ironstone, pale-yellowish brown, very hard, dense; effervesces slightly with dilute HCl.

4 ft 9 in., clay shale and claystone, medium-light-gray, medium-soft; ben tonitic in upper foot; poor to fair cleavage; hard clay ironstone nodule 3 in. thick in middle of interval. Just below this is 4 in. of medium-dark gray carbonaceous shale. Whole in terval is non calcareous.

209-219 Recovered 10 ft.

2 ft 5 in., bentonite, very light-gray, argillaceous, soft but brittle.

8 in., carbonaceous clay shale, medium dark-gray; contains very thin layers of low-grade coal.

6 ft. 11 in., clay shale and claystone, medium-light-gray, medium-hard;

poor to good cleavage; rare silty and carbonaceous streaks; noncalcareous;

dip 3°.

219-229 Recovered 9 ft.

6 in., bentonite, white to very light gray; hard when dry; conchoidal frac ture.

5 in., lignite, grayish-black, hard, brit tle, bedded; dip 2°.

6 ft 4 in., claystone, light- to medium light-gray; slightly to moderately cal careous, medium-hard; irregular frac ture; slightly silty in places; contains vary rare coaly fragments.

1 ft 9 in., clay shale, medium-dark-gray, carbonaceous; contains layers up to an inch thick of lignite and dull black coal having a blocky fracture.

229-239 Recovered 10 ft.

1 ft 7 in., clay shale as immediately above; carbonaceous but with no coal or lignite.

1 ft, claystone, very light-gray, very bentonitic, medium-soft; contains scattered black carbonaceous par ticles; grades into unit below.

4 ft 8 in., siltstone, light-gray, very micaceous, noncalcareouB, slightly bentonitic, medium-hard; grades into unit below.

2 ft 9 in., sandstone, light-gray, very fine-grained, non calcareous, medium soft; grains angular to subangular;

75 percent white and clear quartz;

remainder is mostly white mica and carbonaceous particles; argillaceous matrix.

Core

Lithologic de8oriptia-Continued

Depth (feet) Remarks

239-249 Recovered 8 ft.

4 ft 6 in., sandstone as above, silty, non calcareous, soft and friable; irregular fracture.

2 ft, clay shale and claystone, medium olive-gray, medium-soft; fair to poor cleavage; contains brownish plant material and streaks of grayish black lignite; non calcareous to moderately calcareous toward bottom.

1 ft 6 in., clay shale and claystone, light olive-gray, moderately calcareous;

lacks plant material; irregular frac ture; dip 2°.

249-259 Recovered 10 ft.

Claystone, light-olive and yellowish gray to light-gray, medium-hard;

irregular fracture; rare carbonaceous particles; about 4 in. of dark gray brittle lignitic clay at 243 ft. Cal careous in yellowish upper 3 ft; non calcareous in lower part.

259-269 Recovered 10 ft.

3 ft 2 in., claystone, medium-light-gray, noncalcareous, medium-hard; irregu lar fracture; rare silty laminae.

1 ft 4 in., carbonaceous clay shale and lignite, medium-dark to dark-gray, medium-hard; rare shiny coal string ers, ~-in. layer of very light-gray bentonite in middle. Beds lie flat.

3 ft 6 in., claystone as in first part of core; very uniform of texture and color.

4 in., lignite and carbonaceous shale, grayish-black.

1 ft 8 in., claystone as above but con tains 4 in. of soft friable noncalcare ous fine-grained light-gray sandstone, coaly plant remains and carbona ceous partings.

269-279 Recovered 10 ft.

Claystone, medium-light- to medium gray, non calcareous medium-hard;

following are variations: At 272~ ft is 6 in. of dark-gray lignitic brittle clay shale, bentonitic at upper end;

at 276 ft is about a foot of light-gray soft bentonitic streaks; at 277 ft is 2

in. of carbonaceous clay shale.

279-289 Recovered 7 ft 6 in.

3 ft, claystone as above, 4 in. of dull· black lignite at 280 ft.

4 ft 6 in., siltstone, light-gray, very argillaceous, finely micaceous, non calcareous, slightly bentonitic, me· dium-soft to soft and friable; grades into claystone toward base. One inch layer of carbonaceous shale 3 in.

from base.

492 EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

Lithologic description-Continued

Depth (feet) Remarks

289-299 Recovered 10 ft.

7 ft, claystone, light-gray, very silty, noncalcareous, medium-hard; grades to siltstone in places, dip 1 0.

2 ft 6 in., lignite and carbonaceous clay shale, dark-gray to grayish-black, medium-soft, brittle.

6 in., claystone, light-olive-gray, slight ly calcareous or sideritic, hard.

299-309 Recovered 10 ft.

Interbedded clay shale (or claystone) and siltstone with all gradations, light, to medium-light-gray, medium soft; rare thin streaks of calcareous (sideritic?) brownish clay shale; rare very fine-grained sandstone laminae;

4 in. of hard calcareous sandstone at 302~ ft.

309-319 Recovered 9 ft.

2 ft 10 in., claystone and clay shale, light-brownish-gray, non calcareous, medium-soft; contains much macer ated plant material.

8 in., carbonaceous shale and lignite, dark-brown ish- to dark-gray.

5 ft 6 in., interbedded claystone and siltstone, non calcareous; medium soft, about equal proportions as in core above; rare black carbonaceous particles.

319-329 Recovered 8 ft 6 in.

2 ft, claystone, light- to medium-light gray, non calcareous, medium-soft.

1 ft 2 in., clay shale, medium-dark gray, carbonaceous; streaks of lignite and coal.

2 ft 8 in., clay shale, medium-light gray, bentonitic, soft; conchoidal fracture.

2 ft 8 in., clay shale, medium-light gray, non calcareous, medium-soft;

rare carbonaceous plant fragments.

329-339 Recovered 10 ft.

2 ft 4 in., interbedded claystone and siltstone, light- to medium-light-gray;

grades into unit below.

7 ft 8 in., sandstone, light-gray, very fine- to fine-grained noncalcareous, medium-soft; irregular fracture;

grains angular to subangular and made up of clear quartz with some white quartz, also chert, white mica, black carbonaceous particles, vol canic glass shards, rock fragments, and rare minerals; essentially noncal careous; matrix is bentonitic and ar gillaceous; no oil or gas shows.

'Fora detailed description ofa sample from 345 Ct by P. D. Krynlne see p. 498

Core

Lithologic description-Continued

Depth (Ceet) Remarks

339-349 Recovered 10 ft.

Sandstone,! as above, friable, fine- to medium-grained; rare calcareous grains; bentonitic matrix; rare black carbonaceous coaly plant fragments;

no shows.

349-359 Recovered 10 ft.

SandstonE', as immediately above.

359-369 Recovered 10 ft.

5 ft, sandstone, as above.

1 ft 2 in., clay sbale, medium-dark gray, carbonaceous; a few thin lami nae of lignite.

4 in., clay ironstone, dark-yellowish orange; effervesces slightly with di lute HCl; contains dark-brown plant fragments.

1 ft 4 in., claystone, light-gray, ben-tonitic.

6 in., clay shale, and lignite as above.

6 in., clay shale, light-gray, bentonitic.

1 ft 2 in., claystone, medium-light-gray, slightly silty, noncalcareous, hard; dip 3°.

369-379 Rp-oovE'red 9 ft.

4 ft 6 in., claystone, as immediately above.

11 in., clay shale, medium-dark-gray, carbonaceous.

7 in., bentonite, white, hard; irregular fracture; contains volcanic glass shards, rare biotite plates.

3 ft, clay shale, medium-light- to me dium-dark-gray; varying amounts of carbonaceous material; some lignite;

2 in. of brittle dull black coal at 377 ft, also thin streaks of bentonite.

379-389 Recovered 9 ft.

Claystone and clay shale, light- to me dium-dark-grf!.y; some spots have yellowish cast. Four inches of dark gray-lignite and carbonaceous shale at 382 ft. Lowest third quite car bonaceous, with a few very thin lam inae of lignite. One inch of very light-gray bentonitic shale at 381 and 385 ft. N oncalcareous to slightly calcareous.

389-399 Recovered 10 ft.

Claystone, medium-hard; about half is light olive gray and is slightly to moderately calcareous; other half is medium gray and nOn calcareous but is carbonaceous with a little lignite at 393 and 398 ft. Irregular frac ture. Light gray bentonite layer at 392~ ft.

CORE TEST, SENTINEL HILL AREA, AND TEST WELL, FISH CREEK AREA, ALASKA 493

Lithologic description-Continued

Depth (feet) Remarks

399-409 Recovered 10 ft.

Claystone, light- to medium-light-gray;

silty beds; light-oolored bentonitic laminae at 406 and 408 ft. Carbo naceous laminae and 1 in. of lignite at 404 and 407 ft. 1 in. Slightly to moderately oalcareous in silty streaks;

non calcareous elsewhere.

409-419 Recovered 8 ft.

1 ft, claystone as above.

6 ft, claystone, light-olive-gray to moderate-yellowish-brown, silty, moderately to very calcareous, hard;

irregular fracture; carbonaceous part ings.

1 ft, claystone as in core 30, slightly carbonaceous.

419-429 Recovered 10 ft.

4 ft 6 in., olaystone, light-olive-gray, moderately calcareous, medium-hard;

irregular fracture; contains numerous black carbonaceous plant fragments and particles.

5 ft 6 in., olaystone, light-gray; as above but with fewer plant fragments and noncalcareous.

429-439 Recovered 10 ft.

Claystone, mostly of type in upper interval of above oore, and about 20 percent medium-ligbt-gray clay shale, one-half inch of carbonaceous shale at 434 ft; slightly to moderately calcareous; quite silty toward base.

439-449 Recovered 9 ft.

1 ft 10 in., sandstone, light-gray, fine grained, soft and friable, very "dirty"; about 50 percent mioaceous material, 40 percent quartz; re mainder is carbonaceous material and yellowish calcareous grains, argillaceous and slightly bentonitic matrix, grains angular to suban gular.

1 ft 1 in., claystone, light-olive-gray, moderately calcareous, medium-hard.

4 in., lignite, grayish-black; dip 4°.

5 ft 9 in., claystone, light-olive-gray, moderately calcareous, medium-hard.

449-459 Recovered 10 ft.

5 ft, siltstone, light-olive-gray, moder ately calcareous, medium-hard, mas sive; sandy near base.

3 ft 9 in., sandstone, light-olive-gray, medium-grained, hard, massive; an gular to subangular grains made up of 70 percent white and clear quartz, 10 percent calcite, 10 peroent mica;

Core

LithoZogic description-Continued

Depth (feet) Remarks remainder carbonaceous particles and other minerals. Lower 1% ft is very hard, yellowish gray, and very cal careous.

1 ft, claystone, medium-gray, hard.

3 in., carbonaceous clay shale and lignite, dark-gray.

459-469 Recovered 7 ft 6 in.

1 ft 4 in., clay shale, medium-dark gray, carbonaceous, and low-grade, dull to shiny black ooal.

1 ft, clay shale, light-gray, bentonitic, soft.

5 ft 2 in., claystone, medium-gray, slightly silty, non calcareous, medium hard contains carbonaceous partings.

469-479 Recovered 8 ft.

4 ft 6 in., sandstone, medium-light gray, very fine-grained, silty, non calcareous soft and friable; contains numerous carbonaceous partings and particles; dip 4°, no gas or oil shows.

3 ft 6 in., claystone, medium-gray and light-olive-gray; 3 in. of very light gray bentonite in middle and 3 in. at bottom.

479-489 Recovered 10 ft: Microfossils present.

8 ft 6 in., interbedded siltstone and clay shale, light-olive-gray, moderately calcareous, medium hard; poor cleav age; contains numerous carbonaceous plant fragments.

1 ft 6 in., clay shale, medium-light-gray, noncalcareous; fair cleavage, subcon choidal fracture; shell fragments.

489-499 Reoovered 9 ft.

4 in., clay shale as above.

7 in., clay shale, medium-dark-gray, carbonaceous; 1 in. shiny black coal.

6 ft 9 in., claystone, light-olive-gray, silty, medium-hard, noncalcareous to moderately calcareous; b.entonitic in top few inches.

1 ft 4 in., clay shale, medium-light- to medium-dark-gray, carbonaceous; fair cleavage; 1 in. of grayish-black lignite

499-509 Recovered 10 ft.

Interbedded clay shale (and claystone)

60 percent and siltstone 40 percent, light- to medium-light-gray, medium hard; fair to poor cleavage; rare thin laminae of very fine sandstone, also rare laminae (up to one-half inch thick) of moderate yellowish-brown clay ironstone; noncalcareous in clay shale to moderately calcareous in silt stone; dip 3°.

494 EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

LithoZogic ae8cription-ContInued

Core .1_ Depth (feet) Remarks

509-519 Recovered 8 ft: Microfossils present.

1 ft, claystone as above, with clay iron stone laminae.

5 ft 8 in., clay shale, medium-light- to medium-gray, noncalcareous medium hard; fair cleavage; bentonitic and crumbly in places.

1 ft 4 in., clay shale, medium-gray to medium-dark-gray, carbonaceous;

plant remains.

519-529 Recovered 10 ft.

2 ft, claystone, light-olive-gray, moder ately calcareous; grades into unit below.

8 ft, siltstone, light-olive-gray, very ar gillaceous moderately calcareous, me dium-soft. A gastropod, Lymnaea?

sp., found at 524)4 ft.

529-539 Recovered 9 ft.

1 ft, claystone (and clay ironstone (?», light-olive-gray, very calcareous, hard.

8 ft, interbedded clay shale and clay stone 70 percent, and siltstone 30 per cent, light- to medium-light-gray, some with olive cast; hardness varia ble; siltstone generally softer than clay shale; fair to poor cleavage; 3 in.

of medium-grained sandstone streaked with very thin coal beds at 534 ft.

Sandstone also contains very small white gastropod and pelecypod frag ments; scattered plant fragments in claystone. Siltstone moderately cal careous. Claystone noncalcareous.

539-549 Recovered 9 ft: Microfossils present.

3 ft, clay shale, medium-light-gray, slightly to moderately calcareous, medium-hard; fair cleavage; contains carbonaceous plant impressions and ostracodes.

5 ft, sandstone, light-gray, medium soft and friable; lowest 1 ft very hard, fine to medium grained; grains angular to subangular and made up of about 60 percent white and clear quartz, 20 percent yellowish calcare-

. ous grains, 10 percent black carbona ceous particles, and remainder is white mica, other minerals, and rock fragments; argillaceous matrix except for lowest 1 ft which is very calcare ous; no oil or gas shows.

1 ft, clay shale, light-gray, as in upper part of this core.

549-559 Recovered 10 ft.

Claystone and clay shale, light-gray, slightly calcareous; very rare silty laminae.

Core

LithoZogic de8cription-ContInued

Depth (feet) Remarks

559-569 Recovered 10 ft: Microfossils present.

Clay shale, light- to medium-light-gray, slightly to noncalcareous; some parts have olive cast; small white mollusk fragment at 559 ft; dip 0°_3°.

569-579 Recovered 10 ft: Microfossils present.

Clay shale, as above; noncalcareous;

fair to good cleavage; very rare pyrite.

nodules with brownish halo; 1 white pelecypod fragment at 569)4 ft;

brownish hard clay ironstone nodule at 576)4 ft; 1 in. of white bentonite at bottom.

579-589 Recovered 9 ft: Microfossils present.

Clay shale and claystone, light- to medium-light-gray, medium-soft; fair cleavage; 1 in. of light-olive-gray clay ironstone at top; non calcareous except for ironstone and some silty streaks; bentonitic. White pelecy pod shell fragment at 584 ft; carbona ceous partings and Bome silty beds in middle; beds lie essentially flat.

589-599 Recovered 8 ft: Microfossils present.

4 ft 7 in., clay shale and claystone, light- to medium-light-gray; olive cast in part; fair to poor cleavage;

becomes silty toward base; dip 2°.

1 ft 6 in., interbedded sandstone and siltstone, light-gray, moderately cal careous, medium-soft; sandstone is fine to medium grained; numerous thin clay laminae.

1 ft 11 in., clay shale as in first part of core; bentonitic at top.

599-609 Recovered 10 ft: Microfossils present.

5 ft 6 in., clay shale, medium-light-gray, medium-hard; poor to excellent cleav age; silty in upper foot; contains rare tiny black plant fragments, small pyrite nodules with brownish halo, numerous white pelecypod remains, Mytilu8 sp.; 1 in. of white bentonite at about 608 ft; dip lW.

4 ft 6 in., bentonite, white and very light-gray, rather hard, interbedded with some light-gray clay shale;

breaks parallel bedding; subconchoi dal fracture; contains little biotite particles, carbonaceous partings.

609-619 Recovered 8 ft: Microfossils present.

11 in., bentonite, light-gray, inter bedded with clay shale as above.

7 ft 1 in., clay shale, medium-light to medium-gray, non calcareous, med ium-hard; poor to excellent cleavage;

5 in. of lignite or low-grade grayish black coal; blocky fracture at about 614 ft; becomes siltier toward base.

CORE TEST, SENTINAL HILL AREA, AND TEST WELL, FISH CREEK AREA, ALASKA 495

Lithologic description-Continued

Depth (feet) Remarks

619-629 Recovered 10 ft.

1 ft, bentonite (?), core infiltrated by drilling mud.

9 ft, sandstone, light-gray, fine- to medium-grained, non calcareous or very slightly calcareous, rather soft and friable; grains angular to sub angular, 85 percent white and clear quartz; remainder is carbonaceous particles, various micas, rock frag ments, yellowish clayey particles, argillaceous matrix; porous; carbon aceous laminae and partings; no oil or gas shows.

629-639 Recovered 10 ft.

Sandstone, as above, medium-grained, non calcareous or very. slightly cal careous; no shows.

639-649 Recovered 10 ft.

Sandstone as above, meruum-grained;

no shows.

649-659 Recovered 10 ft.

Sandstone as above; medium grained at top grading to very fine at bottom.

A little harder (medium soft) than cores above; no shows.

659-669 Recovered 10 ft.

Sandstone as above, very fine- to fine grained, noncalcareous; bentonite in matrix, no shows.

669-679 Recovered 9 ft.

Sandstone, as above, fine-grained, mas sive; carbonaceous partings absent except for one 5-in. interval with abundant partings at 674 ft; very calcareous and hard in the lower 4 ft;

no shows.

679-689 Recovered 10 ft.

Sandstone as above, fine- to medium grained, calcareous and hard in first 9 in.; grades into siltstone in bottom 3 in.; 1 brownish sideritic lens at 683 ft; no shows.

689-699 Recovered 10 ft.

Siltstone, light-gray, very argillaceous, non calcareous, medium-soft; fair cleavage; interbedded clay laminae;

irregular bedding.

699-709 Recovered 10 ft: Microfossils present.

3 ft, clay shale, medium-tight-gray, silty, noncalcareous; poor cleavage.

7 ft, siltstolle, light-gray, very argil laceous, noncalcareous, medium-hard.

709-719 Recovered 10 ft: Microfossils present.

Siltstone, as above; hard rare medium light-gray clay shale interbeds; also scattered thin very fine-grained sand stone beds; non calcareous.

Core

Lithologic description-Continued

Depth (feet) Remarks

719-729 Recovered 7 ft 6 in.: Microfossils present.

Siltstone, light-gray, very argillaceous, noncalcareous, medium-soft to me dium-hard; contains numerous white pelecypod shell fragments.

729-739 Recovered 10 ft: Microfossils present.

Interbedded siltstone and clay shale;

about equal proprtions of each, light to medium-light-gray, noncalcareous;

bentonite streaks at 736 and 737 feet.

739-749 Recovered 9 ft 6 in.: Microfossils present.

Interbedded siltstone 70 percent, clay stone 20 percent, and very fille grained sandstone 10 percent, light to medium-light-gray, noncalcareous;

white pelecypod remains at 741 ft and 746 ft.

749-759 Recovered 4 ft 6 in.

1 ft 8 in., siltstone, light-gray, hard, massive; streaks of very fine-grained sandstone.

2 ft 10 in., clay shale and claystone, medium-light-gray, hard; poor to fair cleavage; pyrite nodules with brown ish halos; scattered pyritized plant remains; trace of siderite in two places in shale; noncalcareous; beds essen tially lie fiat.

759-769 Recovered 10 ft: Microfossils present.

5 ft, sandstone, light-gray, very fine- to fine-grained, medium-soft and slightly friable; grains are subangular to angular quartz, mica, carbonaceous particles, rare calcite grains, and rock fragments in white bentonitic matrix.

Sandstone has numerous intercala tions of clay, numerous carbonaceous partings; becomes silty toward base;

rare pelecypod remains; no oil and gas shows.

5 ft, clay shale, medium-light-gray, medium-hard; fair cleavage; silty in upper foot; 4 in. of very light-gray bentonite at 764 ft, and 2 in. at 764~ ft; 2-in. light-olive-gray iron stone nodule at 768 ft; pyrite nodules and pyritic plant remains.

769-779 Recovered 8 ft.

6 in., clay shale, m~dium-dark-gray, carbonaceous.

7 ft, interbedded siltstone 60 percent, and claystone, light- and medium light-gray, hard; slightly sandy streaks, siltstone is slightly cal careous.

6 in., bentonite, very light-gray.

EXPLORATION OF NAVAL PETROLEUM RESERVE NO.4, ALASKA, 1944-53

Lithologic de8cription-{'Jontinued

Depth (feet) Remarks

779-789 Recovered 10 ft.

9 ft, clay shale, medium-light- to me dium-dark-gray, partly carbonaceous and bentonitic, medium-soft; abun dant black carbonaceous and pyritic plant impressions; very rare white pelecypod remains; pyrite nodules with alteration halos.

1 ft, siltstone, light-gray, sandy; car bonaceous partings; very bentonitic matrix.

789-799 Recovered 10 ft: Microfossils present.

5 ft, siltstone and sandstone, light-gray, medium-soft; sandstone very fine grained; numerous tiny pelecypod shells; bentonitic matrix; scattered black carbonaceous laminae; thin interbeds of clay shale; noncalcareous.

5 ft, carbonaceous clay shale, medium gray to medium-dark-gray, medium hard; black plant remains; 3 in. of very light-gray bentonite at 795 ft;

very thin almost varvelike bentonite laminae in lowest foot; non calcareous ;

beds lie approximately fiat.

799-809 Recovered 10 ft: Microfossils present.

S ft, clay shale, medium-dark- to dark gray, carbonaceous, medium-hard;

good cleavage; 1 in. of greenish-gray bentonite at 801~ ft; 2 in. of light gray bentonite at 803 ft.

1 ft 6 in., clay shale, medium-gray;

carbonaceous plant fragments.

3 ft 6 in., siltstone, medium-light-gray, irregularly bedded; clay intercala tions; rare bands of coaly plant material.

809-819 Recovered 10 ft.

4 ft, interbedded clay shale 70 percent, and sandy siltstone 30 percent, light to medium-light-gray, medium-soft;

gradations of color, carbonaceous partings; siltstone is bentonitic.

6 ft, clay shale, medium-light-gray, medium-hard; fair cleavage; scat tered black plant fragments; rare small pelecypod remains; 3-in. of very light-gray bentonite at base.

819-829 Recovered 10 ft: Microfossils abundant.

Clay shale,…