Geology of the Killik-Etivluk Rivers Region, Alaska

EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4 AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53 PART 3, AREAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 303-F

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

Geology of the Killik-Etivluk Rivers Region, Alaska

By ROBERT M. CHAPMAN, ROBERT L. DETTERMAN, and MARVIN D. MANGUS

EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4 AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53 PART 3, AREAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 303-F

Prepared and published at the request of and in cooper­ ation with the U.S. Department of the Navy, Office of Naval Petroleum and Oil Shale Reserves This report is based onfieldwork by Robert M. Chapman, Robert L. Detterman, Marvin D. Mangus, Robert S. Bickel, G. Donald Eberlein, Charles A. Kirschner, Arthur H. Lachenbruch, Milton C. Lachenbruch, Charles D. Reynolds, Karl Stefansson, Robert F. Thurrell, Lawrence A. W^amer, and James Zumberge

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS

Pag_ Page Abstract. ______325 Stratigraphy Continued Introduction. ______325 Quaternary system...______-______--__---____ 382 Location and size of area. ______325 Glacial deposits..______382 Previous work.. ______-_._-__-___ 325 Anaktuvuk glaciation.______383 Early exploration.______325 Itkillik glaciation______.____ 384 Geological investigations..______325 Echooka glaciation.______385 Recent investigations______326 Acknowledgments_ _ - ______328 Fluviatile deposits______-__-__----_-_- 385 Geography....._--_-_-__-_--__-_---_-_---_-_------_ 328 High-level terrace deposits_-_____-__-____ 385 Relief and drainage. _-_--_--______-____--____ 328 Alluvium. ____---___----_------_-- 386 Accessibility- ______331 Lacustrine deposits_-_-_--__.____-___------386 Climate.-__------_-_------_-----_----_-- 332 Eolian deposits______._-__-__-____---___ 387 Place names______332 Igneous rocks.._--______-______--____--_--_------388 Animals and plants ______333 Occurrence and distribution,______388 Population and archeology___-____-_-_--_--_---_- 333 Petrology--_----_------_- 389 Permafrost... -___-_--_-_--_____-__-___--______-_--_ 334 Stratigraphy ______334 Structure._------__-_--_------_--- 389 Devonian system ______334 Brooks Range province.______389 Upper Devonian limestone.______334 Southern foothills section_--_____-__----_-_-_---_- 390 Hunt Fork shale.-_-_-_-__-_--__-____-_-__-_ 336 Northern foothills section..______-_-__--__-- 391 Kanayut conglomerate.__-___-__-_-_--_-____ 337 Oolamnagavik River structural high-. ___...___ 391 Mississippian system.______340 Kurupa anticline.______392 Kayak shale.-__-_-__-______-_____-______340 Aupuk and Killik Bend anticlines.______392 Lisburne group..______341 Wachsmuth limestone.____-__-______--____-_ 345 Geologic history______-_-___------393 Alapah limestone.______346 Economic geology______-____--___--_---- 394 Carboniferous and Permian systems.______347 Petroleum possibilities.______394 Siksikpuk formation.______347 Paleozoic rocks.______-___--_--- 395 Unnamed Carboniferous and Permian unit..... 348 Triassic and Lower Cretaceous rocks ______395 Triassic system..______348 Lower and Upper Cretaceous rocks ______396 Shublik formation.______348 Jurassic system-___-______350 Nanushuk group....___.___-____---__--- 396 Tiglukpuk formation.______350 Colville group-______-__-_--_- 397 Cretaceous system______.______352 Structure ______.______---_--_---_- 398 Okpikruak formation..______352 Gas seeps.______-__-_------399 Fortress Mountain formation______353 Coal. _-_--_--_--_--_-_---_------_--- 399 Torok formation.______357 Colville River______-___--_--_----_------400 Nanushuk group______360 Kurupa River.______-___--_---- 401 Tuktu formation______361 Oolamnagavik River______-____-_-_-- 401 Chandler formation ______369 Killik River______------_-_------401 Killik tongue_-.______370 Phosphate-bearing rocks.______-__------_ 401 Niakogon tongue-_--_____-____.____ 378 Ninuluk formation.______381 Selected Bibliography.______---_-__--_------403 Colville group______382 Index. ______.______-__---__---- - 405 m IV CONTENTS ILLUSTRATIONS [Plates are in separate volume]

PLATE 43. Geologic map. 44. Columnar sections of the Paleozoic formations. 45. Columnar section of the early Mesozoic formations. 46. Columnar sections of the Fortress Mountain formation. 47. Columnar sections of the Torok formation. 48. Correlated columnar sections of the Nanushuk group. 49. Glacial map. Page FIGURE 54. Index map of the Killik-Etivluk Rivers region.______._____.._.______-______-______-__--._.-_ 326 55. Index map showing areas studied..._-______-____--_-_-_--______----__-_-____-_----___-- 327 56. View of Killik River pass_.______329 57. View of Howard Pass.------..-..______330 58. Vertical and horizontal views of drained lake______335 59. View of overturned fold in Lisburne group______-_____-_____.._-___--_--_-__-__--__-- 343 60. View of Lisburne Ridge.______344 61. View of Smith Mountain.______354 62. Diagrammatic sections of the Nanushuk and Colville groups__.-______362 63. View of glacial lake deposit on Killik River______---__-___-___-___---_----_--_------_---__- 386 64. View of sand dunes on Killik River.______-______--_--___------__--_-__ 387 65. Geographic occurrence of coal and phosphate____.______--______-______-___-_-_-__---__---__--__-- 400

TABLES

Page TABLE 1. Gradients of some streams in Killik-Etivluk Rivers region_.___-_-_-_-_---_-_--__-_.--_.---_------331 2. Weather data for Killik-Etivluk Rivers region for period May 15 to September 1, 1946, 1949, 1950, and 1953____ 333 3. Fossils of Kayak shale_------___--___.__..___.__..___..__._...__..-___.____--___----_-_.------342 4. Fossils of Lisburne group______.______.______._.__.._..______-____------_--- 346 5. Microfossil check list for Paleozoic and early Mesozoic formations.--______-_-_----_-_-_------349 6. Fossils of Shublik formation. ______-_ 350 7. Fossils of Torok formation.______360 8. Fossils of Tuktu formation..,._.______._.______.______._.______._.__ 367 9. Microfossil chart for the Nanushuk group.______.____.______-_-_-.___---_----_- 368 10. Plant fossils from Killik tongue______378 11. Porosity-permeability of selected samples___--___-_-____-__..--__--______--___-_-_-_-__-_-_------397 12. Analyses of gas from Aupuk and North Colville seeps____-__--__--.___--_---__--__------399 13. Analysis of samples of coal from the Killik-Etivluk Rivers region______---_--_------402 14. Yields of carbonization products by Fischer low-temperature carbonization assay at 500 °C, as received coal basis ______402 15. Chemical and physical properties of gas by Fischer low-temperature carbonization assay at 500°C______403 16. Analysis of field samples showing percent P205 and equivalent uranium..__..___.__..._..___-.-__-.-..--.--- 403 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4 AND ADJACENT AREAS, NORTHERN ALASKA, 1944-53 GEOLOGY OF THE KILLIK-ETIVLUK RIVERS REGION, ALASKA

By ROBERT M. CHAPMAN, ROBERT L. DETTERMAN, and MARVIN D. MANGUS

ABSTRACT

The Killik-Etivluk Rivers region is an area of about 5,800 rocks of the Chandler formation of late Early Cretaceous to square miles in the central part of the Brooks Range and Arctic early Late Cretaceous age. foothills provinces of northern Alaska. About 1,500 square Phosphate-bearing rocks occur in the Lisburne group of miles along the western side of the region is in Naval Petroleum Mississippian age and the Shublik formation of Triassic age Reserve No. 4. in the Brooks Range and the southern foothills. The shale Bedded sedimentary rocks at least 36,000 feet thick are ex­ generally contains less than 5 percent PgOs. posed in the region. The rocks are dominantly of marine origin and range in age from early Late Devonian to early INTRODUCTION Late Cretaceous; they have been divided into 17 formations. LOCATION AND SIZE OF AREA Paleozoic sedimentary rocks, exposed only in the Brooks Range and the southern foothills section of the Arctic foothills province, The Killik-Etivluk Rivers region is in the southern consist of slate, shale, quartzite, quartzitic conglomerate, chert, central part of northern Alaska. It lies north of the and limestone. The source area for the Paleozoic rocks was crest of the Brooks Range, south of the Colville River, apparently to the north; deposition was continuous from Late Devonian to Late Mississippian. Rocks of Pennsylvanian and between the Killik River and the western limit age are absent and Permian rocks overlie the Mississippian. of the Etivluk River drainage (fig. 54). This area A southerly source area is indicated for the Mesozoic sedimentary covers about 5,800 square miles; about 1,500 square rocks in the foothills; these rocks are primarily shale, siltstone, miles along its western side is in Naval Petroleum sandstone, and conglomerate. Deposition of the Mesozoic Reserve No. 4. sedimentary rocks was not continuous. The oldest Mesozoic PREVIOUS WORK rocks are early Middle Triassic and the youngest are early Late Cretaceous. Sedimentary rocks of Tertiary age are not EARLY EXPLORATION present in the Killik-Etivluk Rivers region. The only recorded exploration in this area previous The bedded rocks are deformed by a system of west-striking to 1924 was that of Ensign W. L. Howard, U.S. Navy, folds and faults. Large overturned folds, thrust faults, and in 1886 (Stoney, 1900, p. 66-71). Howard, accom­ reverse faults are characteristic of the Brooks Range. Folds in the southern foothills section of the Arctic foothills province panied by Eskimos, traveled by dogsled from the are small, tight, and steeply plunging; numerous small high- Brooks Range pass which now bears his name, down angle faults cut the bedded rocks in the southern foothills the Etivluk River to the Colville River and thence section. Large open folds are characteristic of the northern northward to Barrow. Schrader (1904, p. 31) reported foothills section, with only minor faults present. that a party of prospectors in the summer of 1903 Mafic intrusive rocks in the form of small sills and plugs are present in the Brooks Range and southern foothills section. crossed through a pass in the Brooks Range at the These mafic rocks are primarily dolerite and gabbro that may head of the Killik River, traversed this river to its be intruded along thrust faults. confluence with the Colville River, and went about Surficial deposits of glacio-fluvatile, lacustrine, and eolian 50 miles up the Colville from the mouth of the origin cover about 30 percent of the region. Part of the region Killik. Apparently members of this party provided was glaciated at least three times by alpine valley galciers that are tentatively assigned a pre-Wisconsin to Wisconsin age. Schrader with a sketch map of the Colville River and A glacial lake about 25 miles long was formed in the Killik River tributaries, which he incorporated in his published valley; the drained lakebed is now a sand dune area. maps (Schrader, 1904, pis. 2, 3). Both exploratory Two small gas seeps in the Colville River valley near the journeys provided valuable geographic information but mouth of Aupuk Creek are the only surface indication of possible only a few geological observations. petroleum and gas acculumation in the northern foothills. Some oil shale occurs in rocks of Triassic age near the Oolamnagavik GEOLOGICAL INVESTIGATIONS River and Imnaitchiak Creek in the southern foothills section of the Arctic foothills province. In 1924 the first systematic geological studies of Subbituminous to bituminous coal in beds a few inches to this region were made by Smith and Mertie (1930). 3 feet thick are common in the northern part of the region in From a camp in the Brooks Range near the head of 325 326 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

150 MILES

FIOURE 54. Index map showing location of the Killik-Etivluk Rivers region, Alaska, in relation to Naval Petroleum Reserve No. 4. the Killik River, Smith descended the Killik, went charge of Lt. W. H. Phillippi, traversed the Colville up the Colville River to the Etivluk River and as­ River between the Oolamnagavik River and Aupuk cended this river 20 miles before turning back to con­ Creek in 1945. In the same year Warner and Kirschner tinue northward on the Awuna River. Mertie, starting traveled by boat from lat 68°23' N. to the Colville from the same camp, spent more time on the Killik River and mapped the geology along the Killik River. and tributaries and then went downstream on the In the 1946 field season, Chapman and Thurrell made Colville River. geological traverses along the Oolamnagavik River In 1925 Gerald FitzGerald, topographic engineer, from about lat 68°30' N. to the mouth, along the and W. R. Smith, geologist, went down the Colville Kurupa River from lat 68°38' N., to its mouth, and River to the Etivluk River and up the Etivluk to its along the Colville River between the Kurupa and head; they crossed the Brooks Range through Howard Killik Rivers. This party also traveled by boat. Pass (Smith and Mertie, 1930, p. 19-21). The geology along the Colville River between the Both expeditions were made as part of the investi­ Etivluk and Kurupa Rivers was mapped in August gations by the Geological Survey of petroleum possi­ 1947 by Thurrell. In the later part of August 1948 bilities in Naval Petroleum Reserve No. 4, which was Stefansson, Detterman, Mangus, and W. W. Patton, Jr., established by executive order in February 1923. made a brief examination of the geology in the vicinity of Kurupa Lake. The fieldwork ended with the onset RECENT INVESTIGATIONS of snowy weather. No recorded geological work was done in the Killik- In 1949 a party including Mangus, Detterman, Etivluk Rivers region between 1925 and 1945. In M. C. Lachenbruch, and A. H. Lachenbruch made a the spring of 1945, the Geological Survey, in coopera­ geological traverse along the Etivluk River from the tion with the Navy Department's petroleum investiga­ headwaters at Howard Pass to the mouth; the party tions in Naval Petroleum Reserve No. 4 and adjacent traveled most of this distance by boat. This traverse areas, began a program of geologic mapping in northern also included the lower 20 miles of the Nigu River; Alaska that included nearly all the Killik-Etivluk it was extended about 10 miles south of Howard Pass Rivers region (fig. 55). A Navy geological party, in to include Flora Creek and other headwater tributaries THE KILLIK-ETIVLUK RIVERS REGION 327

.157 156° 155' 154°

69°-

10 10 20 30 MILES

FIGURE 55. Index map showing relation of field mapping (shaded) to photogeologic mapping in the Killik-Etivluk Rivers region, Alaska.

east of the Aniuk River. Later in the season the party of the river, along the Colville River between Aupuk studied the geology of the area adjacent to the upper Creek and the Killik River, and also along the lower Killik River between the mouth of Easter Creek and 4 miles of the Oolamnagavik River. Bickel reexamined lat 68°23' N. the area adjacent to the Etivluk River between the In 1950 Chapman, Eberlein, and Reynolds mapped mouth of the East Fork of the Etivluk River and the the geology in the area of the upper Oolamnagavik Colville River. With the exception of this 1953 work and the Kurupa Rivers and the East Fork of the Etivluk and the study of the Aupuk anticline in 1950, the field- River, and continued a traverse northward along Kucher work can best be classed as "detailed reconnaissance." Creek to the Colville River. During August 1950, In many parts of this area, detailed mapping was Eberlein and Reynolds restudied and mapped the impractical, owing to lack of outcrops and (or) lack Aupuk anticline along the Colville River between of time, although detailed data were collected in places Kucher Creek and the Oolamnagavik River; this where exposures were expecially good. The work of party traveled overland by weasels (small tracked parties traveling by boat was in general limited to the cargo-carrying vehicles designed for military use in area that could be reached in a day's round trip on World War II). foot from camps established on the rivers. During the 1953 field season Detterman and Bickel Since completion of the fieldwork, the compilation of traveling by boat, made detailed reexaminations along field data has been supplemented by study and inter­ the Killik River between lat 68°27/ N. and the mouth pretation of the excellent vertical aerial photographs 328 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 taken by the U.S. Navy, which give complete coverage ozoic and early Mesozoic sedimentary rocks was written of the mapped area. by Mangus and Chapman and that of the Cretaceous ACKNOWLEDGMENTS and Quarternary by Detterman. The igneous rocks are discussed by Mangus. The sections on structure A project of the magnitude and duration of this were written by Mangus, Chapman, and Detterman study, in such a remote and uninhabited area, could following the same general divisions that are used in not have been completed without the assistance and the discussion of the stratigraphy. Economic geology cooperation of many people. The authors wish par­ was written by Chapman, with the following exceptions: ticularly to acknowledge the geologic work of L. A. coal by Detterman; phosphate by Mangus and Warner and C. E. Kirschner and that done in 1950 Chapman. by G. D. Eberlein and C. D. Reynolds; their work GEOGRAPHY has been incorporated in this paper. BELIEF AND DRAINAGE It is a pleasure to commend the unfailing coopera­ tion, ability, and congenial companionship, even under The Killik-Etivluk Rivers region includes parts of occasional extremely adverse physical conditions, of two well-defined physiographic provinces, the Brooks the following personnel who assisted the geologists of Range and the Arctic foothills (Payne, 1951), the latter the various parties: being subdivided into southern and northern sections. 1945. Ome Daiber, camphand; Elder Lebert, cook. The Brooks Range province, which includes approxi­ 1946. Edward G. Sable and Arthur H. Lachenbruch, mately the southern one-third of this region, includes geologic field assistants; Delmar L. Isaacson, also the western part of the rugged Endicott Mountains cook. that reach a maximum altitude of 7,400 feet near the 1947. James H. Zumberge, geologic field assistant. Killik River, and the Howard Hills at the head of 1948-1949, Elder Lebert, cook. the Etivluk River, which have a maximum altitude of 1950, W. Douglas Carter and William L. D'Olier, Jr., about 4,900 feet. The average relief in the part geologic field assistants; Richard D. Olson, cook; between the Killik and Kurupa Rivers is approximately Max H. Davis, Arctic Contractors' weasel 3,400 feet; between the Kurupa and Etivluk Rivers mechanic. it is about 2,200 feet. Although the topography is Much of this area would have been inaccessible quite rugged, there are very few prominent landmarks without the air transportation handled, often under in the mapped region. hazardous conditions, by the pilots of Wien Alaska The southern foothills section of the Arctic foothills Airlines, Alaska Airlines, and Transocean Airlines. province includes prominent west-trending ridges, Naval and Arctic Contractors' personnel provided in­ groups of hills, isolated hills of various sizes, and some valuable assistance many times during the work. broad featureless tundra-covered areas. The maxi­ The work of three of the field parties were facilitated mum altitude within this section is along the southern by caches of food, weasel fuel, aircraft gasoline, and boundary where several hills rise to between 3,500 some equipment that were placed at predetermined and 4,000 feet. In the northern part of this section, localities along their route of travel before the work Smith Mountain near the Etivluk River and a group began. Edward J. Webber in 1946, M. D. Mangus of hills between the Oolamnagavik and Killik Rivers in 1949, and A. Samuel Keller and Irvin L. Tailleur are approximately 3,200 feet in altitude and are out­ in 1950, all ably supported by "bush" pilots, success­ standing landmarks. The average relief within this fully completed these hazardous airborne operations. section is approximately 900 feet. The assistance, helpful comments, and contributory Several excellent pa'sses through the Brooks Range field work in adjacent areas by personnel of the Geo­ in the Killik-Etivluk Rivers region are broad and open, logical Survey, including paleontologists, H. R. Berg- and are less than 3,400 feet in altitude; foot and weasel quist, A. L. Bowsher, J. T. Dutro, Jr., B. H. Kummel travel is entirely feasible. The valleys are so free from and R. W. Imlay, whose fossil identifications added obstacles such as steep grades, incised valleys, and much in the age determinations of the mapped units, morainal boulders that one can use tracked vehicles are gratefully acknowledged. very easily in an east-west direction between the This report was compiled jointly by the three authors, Noatak-Etivluk Rivers area and the Killik-John Rivers with each author responsible for individual sections. divide, a distance of over 100 airline miles. Besides The introduction was written by Robert M. Chapman, facilitating movement from one drainage system to with the following exception: Climate by Robert L. another on the ground, the passes also provide excellent Detterman. The section on permaforst was written routes for single-engine aircraft in traveling through by Marvin D. Mangus. The stratigraphy of the Pale­ the mountains in overcast weather. THE KILLIK-ETIVLUK RIVERS REGION 329

in the Killik River drainage, Easter Creek affords The Etivluk River affords the lowest and easiest several tundra-covered passes into the south-flowing pass through the Brooks Range in the mapped area (fig. drainage system of the John River-Hunt Fork and the 57). This pass was used by the Geological Survey Alatna-Kutuk Rivers drainage. At the headwaters expedition of 1925 (Smith and Mertie, 1930, p. 19-21) of April Creek, several excellent passes into the Alatna and by Ensign Howard in 1886 (Stoney, 1900). drainage are present. The one at the head of the east Approximately the north one-fourth of the mapped fork was used by the Geological Survey expedition of area lies within the northern foothills section of the 1924 (Smith and Mertie, 1930, p. 10-15). The valley Arctic foothills province. It includes a generally of the upper Killik River where it bends 90° and changes featureless belt along the southern boundary of this course from northwest to northeast is open to the Alatna section, succeeded northward by a gentle escarpment and Nigu Rivers drainages (fig. 56). Along the course and then by broad, relatively low, rolling ridges that of the Nigu River and its tributaries, passes can be trend west. There are no outstanding topographic found almost anywhere from the Nigu and Etivluk landmarks, and the maximum altitude does not exceed Rivers into the Noatak River. The upper courses of 2,000 feet. The average relief is approximately these rivers flow in broad, open glaciated valleys. 300 feet.

FIGUEE 56. Oblique view of the Killik River pass through the Brooks Range. Photograph by U.S. Navy. 679606 O 63 2 330 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

FIGURE 57. Oblique view of the Howard Pass area showing route through the Brooks Range. Photograph by U.S. Navy.

The Killik, Oolamnagavik, Kurupa, and Etivluk one main meandering channel is developed. The aver­ Rivers and their tributaries, all north-flowing rivers age depth of water is probably about 3 feet; the channels that head in the Endicott Mountains and in the highest and valley floors are laden with glacio-fluvial and re­ foothills, carry nearly all the drainage from this area worked glacial material that has been carried northward into the east-flowing Colville River, which is the by the present streams. Most of the tributary streams largest river in northern Alaska. The only independent are small, not braided, and some are intermittent. The smaller streams of consequence are Kucher and Aupuk Killik River is not braided, and in the northern 20 Creeks, and they head in the foothills and flow into miles of its course within this section, has a moderately the Colville River. In the extreme southwestern part steep gradient in a boulder-laden channel that cuts of the mapped region, the drainage is southwesterly through glacial debris and moraines to form a series into the Aniuk River on the south side of the Brooks of "whitewater" rapids that are somewhat hazardous Range. The only other drainages that differ markedly to navigate. The current in these rapids probably from the northerly pattern are the upper valleys of flows at 9 to 12 miles per hour. The Nigu River in the Nigu and Killik Rivers, which trend west and the southern foothills section is similar to this stretch east respectively, and of Easter and April Creeks, of the Killik River. In general the interstream areas which trend west. are well drained, and the ground is wet but not swampy; The larger valleys within the Brooks Range province however, some parts are swampy enough to seriously have been sculptured by valley glaciers, and some, nota­ hamper cross-country foot travel. bly the Killik, Kurupa, and Nigu, have a typical In the northern foothills section only the Etivluk and broad-floored, U-shaped cross section. Glacial and Killik Rivers are conspicuously braided, although all alluvial debris, composed of material ranging from the main streams have formed wide gravel-laden silt to boulders, is abundant. The courses of the main valley floors in which their present meandering channel streams are braided and generally shallow with low and a few distributaries are slightly incised. The Col­ to moderate gradients, except in the extreme head­ ville River is primarily confined to one channel that waters where they issue from steep narrow .mountain is 300 to 800 feet wide and is estimated to average 10 valleys. The interstream areas are well drained, many feet in depth. Most of the interstream areas are well of them are rocky and precipitous, and they are usually drained, although some of the low and featureless areas dry once the melt water has drained off. remain swampy throughout the summer. In the southern foothills section most of the rivers, The flow of water and the breakup of ice in the streams except the Killik and Nigu, have braided channels in usually begins between May 14 and 25. Ice disappears at least part of their courses, although in most places from the lakes between June 1 and July 15, depending THE KILLIK-ETTVLTJK RIVERS REGION 331 upon the altitude, run-in of melt water, exposure to static pressure from beneath, and heaves and cracks direct sun, and depths of the lakes. The volume of enough to allow the water to come to the surface and water in all the streams fluctuates considerably during overflow. The overflowing water freezes quickly, and the summer season. Usually the highest water stage the action is soon repeated. During this procedure the for the rivers occurs within 3 to 7 days after the breakup ice deposit builds up in thickness from several feet to starts, and many small tributary gullies and washes as much as 15 feet, and also enlarges laterally and carry water only at this time. Normal and low-water lineally. Some of the fields have an area of several stages following the complete melting of the snow square miles. On a cold ( 20° to 40°F) clear day, cover are changed appreciably only by periods of late a large cloud of ice fog, caused by the difference in snowfall in the uplands followed by rain, or by two temperature between the running water and the air, or more days of persistent rainfall; heavy downpours hovers over the ice. or cloudbursts are extremely rare. The tundra has The aufeis fields in this region are seasonal, and the a vast capacity to hold rainfall and release it slowly. size depends upon the amount of water overflow and The occasional high-water stages during the summer the winter temperature. Most of the fields disappear occur abruptly and with great force when once started, by late June, but some last well into August. and they subside .usually within 2 days unless more Lakes of several types are present, but not abundant, rain falls. In August 1946 the Colville River near within this area. Most of the lakes within the Brooks the Kurupa River rose 2 to 3 feet within 10 hours, Range province and in the southern part of the southern as a result of rains in the Brooks Range and southern­ foothills section are the result of glacial scouring and most foothills. A number of torrential flood-stages (or) damming by glacial debris. A few small lakes are were observed in the course of fieldwork, but none present on gravel terraces and in upland interstream quite equaled the maximum stage during spring areas. Numerous small lakes and several large ones breakup. occur in the valley bottoms along the Killik, Nigu, The gradients of the streams in the Killik-Etivluk and Etivluk Rivers in the mountains and southern Rivers region were established from altitudes measured foothills, but there are only a few small lakes along the by altimeter. These altitudes are only approximate, smaller streams. Many of the lakes are shallow, but the control probably was sufficient to establish probably not exceeding 10 to 12 feet in depth. Notable relative gradients (table 1). exceptions, both in size and in depth, are Kurupa and Cascade Lakes, which probably are at least 50 feet deep. TABLE 1. Gradients of some streams in Killik-Etivluk Rivers region Some thermokarst lakes are present in the silt over­ lying the gravel terraces in the northern foothills part Average Approx­ Average gradient of this region. Some lakes, formed in abandoned Stream imate gradient to length (ft per morainal channels and other valley bottom depressions, occur (miles) mile) front (ft per mile) along the Colville River and several of the other larger streams. Killik River... -______-..-_ ...... 126 23 ACCESSIBILITY 44 AA AA 36 34 M 34 6 6 The Killik-Etivluk Rivers region can best be entered 72 39 68 72 36 100 by air, although it can be reached by arduous overland 40 35 90 32 30 49 travel, as was done in the early days, through mountain 76 23 01 68 10 17 passes at the heads of the Killik and Etivluk Rivers. 72 4 There are no settlements, camps, roads, or airfields in the area. Umiat, the only established camp and Aufeis fields, also known as "river glaciers," "ice airfield in this part of Alaska, is on the Colville River fields," and "flood ice," and generally called "glaciers" about 60 airline miles northeast of the mouth of the by the natives, build up throughout the winter season Killik River. Barrow is about 175 miles north- on many of the rivers and their larger tributaries. At northwest. least 12 significant accumulations of aufeis have been In the winter season it is possible to land small, ski- observed on the Killik, Oolamnagavik, Kurupa, Etivluk, equipped aircraft within easy reach of most of the area. and East Fork of the Etivluk Rivers. They form in, Large lakes provide safe landing areas for twin-engine and probably tend to enlarge, wide low-gradient parts ski-wheel-equipped aircraft. In the summer, lakes and of the flood plains, and they seem to recur annually numerous stretches of the larger rivers will accommo­ in the same locations. These ice deposits are formed date pontoon-equipped aircraft, and, except during by overflow water, which runs all winter. After the floodwater stages, gravel bars suitable for wheel first ice freezes over the river, it is broken by hydro­ landings can be found along the largest rivers. 332 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

In connection with the work in this area, wheel The Killik-Etivluk Rivers region includes at least landings by large single-engine aircraft were made on two distinct meteorological provinces; the Brooks Range smooth gravel bars on the south side of the Colville and the adjacent foothills is one province, and the River just downstream from the mouth of the Kurupa northern part of the southern foothills and the northern River, immediately upstream from the mouth of the foothills section is another. In May and June there Oolamnagavik River, and at the mouths of the Killik are more clear warm days in and near the mountains and Etivluk Rivers. Pontoon and ski landings were than farther north; conversely, there are more storms made on the large lakes along the Killik River at lat during July and August. Table 2 does not take into 68°30' N., on Kurupa Lake, the lakes immediately consideration the meteorological provinces, but is an north of Smith Mountain, Howard Pass Lakes, Lake average of the records for the entire region. The Betty, and Etivluk Lake. Several miles southwest weather observations were taken at the various camp of the mouth of the Etivluk River an airstrip large locations and the camps were moved frequently; thus enough to accommodate twin-engine aircraft was con­ it was impractical to compute records for a specific structed in 1952, but it has not been maintained. province. Gravel-bar landing strips, which were used success­ A brief analysis of table 2 will give a general idea of fully by small aircraft, were cleared and leveled by the the conditions under which the geologic investigations field party in 1950 at lat 68°30' N. and lat 68°40' N. were made. The sky was clear only 5 percent of the along the Oolamnagavik River. With little work and time and overcast 54 percent of the time. The mean equipment, landing strips could be made at many places temperature was 49°, with a maximum of 88° and a within this area except in the extremely mountainous minimum of 15°. Precipitation, generally in the form terrain. Due allowance must be made for altitude, of rain or drizzle, occurred on an average of 41 days out performance of various types of aircraft, and especially of every field season; although some snow fell in every the skill of the pilot, in evaluating the usability of month, it was more common in May and August. An many of the natural landing areas. The area, while average of one thunderstorm occurred each year, gener­ not easy to traverse, presents no problems not found ally accompanied by severe squalls and hail. Storms in other parts of northern Alaska. Shallow-draft, usually move in from the southwest, not uncommonly 18-foot folding canvas boats have been used success­ with a rising barometric trend. Precipitation generally fully on the Killik River below Easter Creek, on the does not fall in large quantities, although as is common Oolamnagavik River north of lat 68°30/ N., on the in semiarid regions, the amount may vary consider­ Kurupa River north of lat 68°40' N., on the East Fork ably within a short period of time. The prevailing of the Etivluk River north of lat 68°40/ N., on the wind directions are north to northeast with a shift to Nigu River north of lat 68° 12' N., and on the Etivluk south and southwest during June and July. River north of lat 68°20/ N. Larger boats can be used on the Colville River. Weasels are very useful PLACE NAMES for cross-country travel, and all but the most moun­ The names used in this study for physiographic tainous terrain can be negotiated easily by them. In features and geologic structural features in the region both weasel and boat travel, the skill and experience of have been derived from three sources: from names the the operator determine the limits of safe use. early explorers gave to a few of the more conspicuous CLIMATE features, from names both the early and the recent geologists who worked in the region gave to unnamed Meteorological records were kept by the authors features, and, insofar as known and practical, from during the 1946, 1949, 1950, and 1953 field seasons. native names that have been used by Eskimos who Table 2 summarizes the weather conditions during the were familiar with the region. In addition to names field season from May through August; the table was established by the explorers and geologists, many of compiled from observations taken at 3-hour intervals the Eskimo names were obtained and some corrections from 9 a.m. to 9 p.m. in 1949 and 1953. The observa­ were made by the personnel of the Topographic Divi­ tions for the years 1946 and 1950 were taken at irregular sion of the Geological Survey in 1956 during the course intervals and were not used in determining the monthly of their fieldwork in this region. Most of the names, mean values or the 2-year mean values. A total of 1,268 observations was used. The temperature was with authority for their usage and for some their read from an unprotected thermometer, and both the meaning are on file with the Board of Geographic Names wind velocity and precipitation were estimated; how­ of the Geological Survey; names not in this file can be ever, the values given are probably low rather than documented in the older publications listed in the high. bibliography of this paper. THE KILLIK-ETIVLUK RIVEKS REGION 333

TABLE 2. Weather data for Killik-Etivluk Rivers region for period May 15 to September 1, 1946, 1949, 1950, and 1953 [No records for May 1950; no wind velocity records for 1946 and 1950. Figures shown for maximum wind velocity are single highest observed for month, except for monthly and 2-year means]

Weather and Wind Sky condition Obstruction to Precipi­ Temperature (percent of time) visibility tation (°F) (percent of time) Direction Velocity (percent of time) (mph)

Month and year s 3 8 1 I Thunderstorms !d d 1 I S *-» s 2 I 1 a S § 3 a 1 IS 1 S t» 8P $ 1 1 1 I 1 S 1 0 02 B O 1 1 $ f* t> ! 0 % fc W I 02 £ fc % % i % %

Mayl946.. -..-.-...... _. .._ 0 28 50 22 20 22 0 40 45 0.1 3 0 0 60 30 0 0 0 0 0 10 28 39 17 May 1949...... 8 6 20 66 16 28 6 0 60 .6 8 0 4 40 24 4 2 16 0 0 10 10 35 38 76 15 May 1953. __ ...... __ . __ . __ ..... 0 0 10 90 0 30 1 12 43 .3 7 0 10 1 66 0 0 0 14 3 6 7 25 34 51 25 Mean.. ______4 3 15 78 8 29 3 6 52 .45 8 0 7 21 45 2 1 8 7 1 8 8 30 36 June 1946 ______10 20 55 15 40 0 50 4 70 .5 15 1 15 24 0 2 2 15 12 16 14 49 80 21 June 1949. ______3 10 40 47 13 17 15 9 70 1.0 15 1 2 29 8 2 3 16 20 2 18 11 60 45 83 24 June 1950. ______9 14 30 47 30 0 28 5 80 .4 19 0 43 6 6 3 8 4 8 16 6 44 67 27 June 1953.. __ . __ .... _ ..... __ ... __ . ... 4 25 24 47 35 1 18 9 83 1.2 15 1 8 15 30 1 1 6 8 17 14 9 40 51 70 35 Mean ______. _ ... 4 17 32 47 24 9 16 9 76 1.1 15 1 5 22 19 1 2 11 14 10 16 10 50 48 July 1946-...... 8 42 30 20 44 0 37 13 60 .4 11 3 9 30 21 3 3 3 5 5 21 54 80 31 Julyl949-__. _ ...... 19 30 33 18 59 0 4 1 98 .1 5 0 4 24 17 12 2 23 13 1 4 11 40 57 88 31 July 1950-...... 20 24 16 40 53 0 43 47 80 .2 16 1 40 15 4 2 2 6 3 12 14 48 78 30 July 1953...... 2 23 25 50 35 3 22 13 79 .8 10 0 8 16 22 6 2 7 14 13 12 9 45 53 79 37 Mean.. ______...... 11 26 29 34 47 1 13 7 88 .45 8 0 6 20 20 9 2 15 13 7 8 10 41 55 August 1946. .... _ .... 0 29 18 53 25 20 65 7 57 .8 19 0 11 7 4 7 0 4 25 35 7 45 73 29 August 1949...... 2 14 31 53 20 1 20 2 97 .4 13 0 10 18 1 0 5 42 24 0 0 8 40 61 80 31 August 1950 _ . _____ . . 11 21 24 44 32 0 35 27 80 .4 11 0 50 0 9 7 8 2 7 17 0 47 72 29 August 1953...... 0 4 33 63 13 0 25 20 76 .4 7 0 15 10 35 0 1 6 26 7 0 6 25 54 72 30 Mean _ . _ .... _ . 1 9 32 58 16 1 23 11 86 .4 10 12 14 18 0 3 24 25 4 0 7 32 58 2-year mean _ ...... 5 14 27 54 24 10 28 16 75 2.4 41 1 8 19 26 3 2 14 15 5 8 9 60 49

ANIMALS AND PLANTS POPULATION AND ARCHEOLOGY The animal and plant life within this area is similar As previously stated there are no settlements within to that in most other parts of northern Alaska. Caribou the Killik-Etivluk Rivers region. Umiat, a camplike are abundant, moose and grizzly bear are common, base of no established permanency, and Barrow are and mountain sheep are common but confine themselves the closest points from which supply and transporta­ to rugged mountainous terrain. Foxes, wolves, weasels, tion into this area could be effected. A seminomadic ground squirrels, marmots, and wolverines are common. group of Eskimos now reside at Anaktuvuk Pass in Ducks, geese, and small birds are abundant. Grayling the Brooks Range about 63 miles east of the southeast can be found in most streams and lakes, whitefish and corner of this area. Apparently this group, the only lake trout are common in Kurupa and Etivluk lakes, remaining inland Eskimos in Alaska, has made hunting and pike were found in valley-floor lakes along the Killik trips into the area in recent years. Evidence of old River. The density of mosquito population certainly camp sites, of caribou, mountain sheep, and moose equals, if not exceeds, that of any other area in Alaska. skulls, and of rifle cartridges shows that the area has Gnats are also numerous, and were especially abundant been traversed by Eskimo hunting parties at various in 1949 and 1950. times in the past. Many species of small plants are ubiquitous, and the Flint chippings were found at a number of sites on plants rarely exceed 12 inches in height, except adjacent prominent hilltops and bluffs along the upper Oolam­ to streams. Some small alders are present on slopes nagavik River. Apparently Eskimos used these places at low altitudes, and willows ranging from 2 to 15 as lookout points during caribou hunts, and passed feet in height are common on the gravel bars along the their time by making flint implements while awaiting larger streams. A few poplar trees, not more than 2 wandering bands of caribou. Similar flint chips are to 3 feet in height, were noted in sheltered gullies along not uncommon in the sand dunes along the Killik the Etivluk and Oolamnagavik Rivers at about lat River between the mountain front and the group of 68°30' N., and some as much as 15 feet high occur large lakes. The age of the flint chips is undetermined. along the Killik River at lat 68°40' N. Old camp or village sites, also of unknown age, were 334 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 discovered at Nigu Lake and in the vicinity of Howard Reiser, who examined it, but, owing to lack of time and Pass. These sites were found in the normal course of bad weather conditions, could not make a detailed geologic fieldwork, and probably many more could be investigation. located if an intensive search were made by archeolo- STRATIGRAPHY gists. In 1886, Howard (Stoney, 1900, p. 66-71) found a The rocks exposed in and underlying the Killik- group of Eskimos camped at a place called Etivolopar, Etivluk Rivers region are, with the exception of a few believed to have been at the mouth of the East Fork mafic intrusive bodies, predominantly sedimentary and of the Etivluk River. It is not clear whether this was a include a few metasedimentary units (pi. 43). The temporary camp or an established village. In 1950, sedimentary rocks range in age from early Late Devon­ W. P. Brosge and H. N. Reiser found several old ian through Quaternary, and probably all ages except village sites at Etivluk Lake. It is possible that this Pennsylvanian and Tertiary are represented. The was the village Howard (Stoney, 1900, pi. 1) called section has been divided into 17 formations, which con­ Issheyak, which was on the divide between the Noatak stitute a thickness of at least 36,000 feet. Shale, and Colville River drainages. A small group of sandstone, and silts tone are the most abundant rock Eskimos, who had lived with the Anaktuvuk Pass group types; conglomerate, limestone, quartzite, and slate are since 1949, were living along the Killik River near the much less common; and coal, ironstone, gravel, sand, lakes at the mountain front in 1945. Apparently they and clay form a small percentage of the total section. had resided in this vicinity for several years, but prob­ Many of the formations cannot be exactly delimited ably were not there in 1924, as Smith and Mertie (1930) in either vertical or lateral extent, owing to the similar­ made no mention of them. ity of lithology, to many gradational contacts, to the general scarcity of fossil remains, and to the lack of PERMAFROST exposures in many large sections of the region. The Perennially frozen ground, or permafrost, underlies structural complexity, especially in the southern foot­ the entire mapped region. In the tundra- or vegetation- hills section, increases the problems of stratigraphic covered areas the ground below the top 6 to 12 inches correlation. remains frozen during the entire year, but in the more DEVONIAN SYSTEM porous and permeable gravel bars and ancient gravel Devonian rocks, the oldest known in the mapped deposits, the ground thaws to a depth of several feet area, are believed to have deen deposited in a marine by late August. In the upper Killik valley, in several environment. They have been divided into three inactive dune sand deposits, the sand was thawed to a distinct mappable rock units: the Upper Devonian depth of 16 inches in 1949. limestone, the Hunt Fork shale, and the Kanayut Excellent examples of a drained lakebed, of ice conglomerate. wedges, and of polygonal ground were examined in in 1946 in the area just south of camp C-July 21-46 UPPER DEVONIAN LIMESTONE on the Kurupa River. The bed of a lake, drained so Between the Nigu and Etivluk Rivers and approxi­ recently that little to no vegetation had taken root in mately 4,000 feet due east of camp M-June 11-49, an it or on its alluvial outwash fan, is about 5 miles south Upper Devonian limestone crops out in an isolated of this camp and on a gravel terrace (40 to 50 ft higher exposure consisting of three small mounds and several than the river level) on the west side of the Kurupa associated rubble traces. The actual size of this out­ River (fig. 58). The drainage channel apparently crop has been exaggerated on plate 43 in order to show developed along an ice wedge, which on melting formed it as a cartographic unit. a small gully; the channel was subsequently enlarged The rock in this exposure is a thick-bedded fine to by headward erosion, and it ultimately provided a coarse crystalline limestone that is very light yellowish path for rapid outlet of the lake water. Older drained gray to light olive gray and well fractured. It weathers lakebeds that are overgrown with vegetation are also light gray to white, with a rough tripolitic surface. shown in figure 58. This outcrop of limestone is probably part of a fault A circular topographic feature, approximately 400 block. feet in outside diameter, is located on the east side of The age of this unit, as determined by J. T. Dutro, Etivluk Lake. It consists of two concentric ridges, Jr., (written communication) from a collection of each about 50 feet wide and 6 feet high, that are sep­ invertebrate fossils, is late Middle or early Late De­ arated by a trough 50 feet wide. The soil is sand and vonian. Dutro stated: fine gravel of glacial origin. This "ring" structure was The fauna consists of: rugose coral, undet.; Atrypa sp.; Spina- interpreted as a permafrost phenomena by Brosge and trypa sp.; Scutellum cf. S. tullium (Hall); and ostracodes (pos- THE KILLIK-ETIVLTJK RIVERS REGION 335

FIGURE 58. Vertical view (above) of drained lake on the high-level terrace on the west bank of the Kurupa River; photograph by U. S. Navy. Horizontal view (below) of drained lake on west bank of Kurupa River, showing floor of lakebed; photograph by R. M. Chapman. 336 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 sibly Bairdia). This assemblage is either late Middle Devonian beds are dark gray green and have a conchoidal fracture. (upper Givetian) or early Upper Devonian (Frasnian) in age. They are more abundant near the top of the section The Scutellum is similar to the Tully form and would seem to indicate a late Middle Devonian age. Similar species, however, and grade upward into sandstone and quartzite. have been reported from the Frasnian of Germany and Australia, Type section of Hunt Fork shale and the genus ranges through Chemung time. The fauna is probably the same age as that reported from the Kiligwa and [Measured by W. W. Patton, Jr., June 1951] Nimiuktuk River valleys farther west where about the same Kanayut conglomerate. time interval is represented by brachiopod and coral assemblages. Hunt Fork shale: Feet These rocks probably are equivalent in age to a part Clay shale, silty shale, and siltstone. Shale is dark of the thick sequence of limestone and dolomite that gray to black, with interbeds of yellow-red- is exposed in the Kugururok valley approximately 120 weathering siltstone; grades upward into inter- miles to the west (J.T. Dutro, Jr., oral communication). bedded shale and light-gray fine- to medium- grained medium- to massive-bedded sandstone. _ 1, 000 This sequence of carbonate rocks is well exposed on Clay shale and siltstone. Shale gray; weathers Mount Bastille, which is in the Kugururok valley at dark yellow red. Unit makes nonresistant zone approximately lat 68°28/ N., and long 160°55/ W. of bright-red soil. Siltstone thin bedded, dark gray green; weathers dark yellow red______245 HUNT FORK SHALE Slate and siltstone. Slate dark gray to black; A thick sequence of shale, locally metamorphosed weathers black. Clay slate at top becomes silty to slate, that lies beneath the Kanayut conglomerate slate near bottom. Minor interbedded siltstone and above Middle Devonian metasediments of the is greenish gray, thin bedded, hard; weathers dark yellow red______690 central Brooks Range, is here named the Hunt Fork Silty shale and siltstone. Shale silty, gray to shale. The rocks were originally described as Devo­ greenish gray, with a few dark-gray silty con­ nian (Smith and Mertie, 1930, p. 139-151). cretions as much as 4 in. in diameter; weathers The Hunt Fork shale is very thick and forms a well- dark yellow red. Locally the cleavage is stronger than the bedding. Minor interbeds of dark-gray defined stratigraphic unit in the central Brooks Range; yellow-weathering siltstone______450 it has been mapped as a continuous belt from the south Silty shale, siltstone, and sandstone. Shale and end of Chandler Lake to the Aniuk River. Over this siltstone are dark gray and weather dark yellow distance of about 120 miles, the unit ranges in width red. In upper part of interval minor amounts of from 5 to 20 miles. The belt of outcrop is typically interbedded gray-green thin-bedded, very fine grained sandstone that weathers dark yellow a relatively low, conspicuously trenchlike valley be­ red. Cleavage well developed locally in the tween the more rugged and resistent rocks to the north shale _ _ -- _ - --- 800+ and south. The formation commonly forms prominent low hogback ridges in these east-trending valleys. Total_____-____-__..-__. 3, 185+ The Hunt Fork shale is not entirely exposed at any Section ends in gravel and tundra. one locality; the greatest thickness was measured in Occurrence. The Hunt Fork shale in the mapped June 1951 by Patton, at the type locality 25 miles east area is very similar to that of the type locality and is of the Killik River at lat 68°18' N. and long 153°20' W., well exposed in the southern part of the mapped area; along Fire Creek, an east-flowing tributary of the the best exposures are along the upper Killik River at Okokmilaga River. its confluence with Easter Creek. This southern At the type locality the rocks dip 6° to 15° S., and outcrop belt is approximately 16 miles wide and forms approximately 3,200 feet of shale, slate, siltstone, and a conspicuous system of east-trending valleys. Aerial sandstone was measured; the lower contact was not photographs indicate that the belt narrows considerably seen, but the upper part is gradational into the over­ to the west and ends 8 miles east of Etivluk Lake. lying Kanayut conglomerate. Approximately 2 miles north of Etivluk Lake, the The Hunt Fork is predominantly shale, locally Hunt Fork shale crops out in a narrow belt of low metamorphosed to slate, with minor amounts of inter- relief about 1 mile wide. It is parallel to the upper bedded hard sandstone and siltstone. The shale is Nigu valley for approximately 10 miles; then it strikes gray brown to dark gray and weathers a mottled dark west to the Etivluk River where it is covered by Quater­ yellow red. In general where slate is present, the nary deposits; it is not exposed west of the Etivluk cleavage is well developed and original bedding has River. been obliterated; some dark bands which are thought Topographically the formation in the upper Killik to be old bedding planes cross cleavage and can be Valley forms striking sharp hogback ridges with a followed short distances. The slate is dark gray green relief of 1,000 to 1,500 feet. Where the shale and slate to black and weathers dark yellow red. The siltstone ridges are capped by a minor amount of the inter- THE KILLIK-ETIVLUK RIVERS REGION 337 calated and more resistant siltstone and the overlying us as USGS quartzite formations, the ridges have ragged serrate Paleozoic Area Location quadrangle Fossil crests and form some of the highest peaks in the central loc. map Brooks Range. 14075 Killik River 2 miles north Kiliik River Spirifer"! sp. valley. of Easter 1:250,000; Character and thickness. In the upper Killik area Creek, east 1:63,360, Palaeaneilo"! sp. side of A-2. Eunemia"! cf. E.t the shale is gray brown to dark gray and weathers a river. speciosum White- aves. mottled brown on the lower slopes of the mountains, 14076 do...... do ..... Killik River Camarotoechia sp. subquad- Punclospirifer? sp. but above 4,000 feet or near the crests it is dark gray rangle A-2. Schizodus sp. Nuculana sp. to black. The slate is soft and foliated, with smooth Palaeoneilo'? sp. Gastropod, gen. and shiny cleavage faces; at most localities the bedding has sp. indet. Bradfordocerast sp. been obliterated. The intercalated siltstone is thin to 14077 do. ..do...... do...... Bradfordoceras? sp. medium bedded, dark gray, and very hard; it breaks Pelecypod, gen. and and sp. indet. with conchoidal fracture and weathers dark gray 14078 . .do __do _do Do. Eunemiat cf. El specio­ brown. sum Whiteaves. Cephalopod, gen. One striking feature of the shale and slate is the rela­ indet. 14079 . . . .do...... do...... do Nuculana sp. tive abundance of anastomosing quartz veins, and in many places the ridge slopes are white with milky KANAYCT CONGLOMERATE quartz regolith. Pyrite and marcasite crystals are common in the quartz with small amounts of chlorite Occurrence. The Kanayut conglomerate crops out and galena. Small calcareous lenses are also associated in the southern part of the mapped area within the with the shale. Brooks Range province, in an east-trending belt about 19 miles wide. This belt is almost entirely Kanayut Toward the top of the section the shale gives way conglomerate, except in several localities where the con­ to siltstone and fine-grained sandstone. The sand­ tinuity is broken by small outcrops of Hunt Fork shale. stone contains both invertebrate and vertebrate fossils. Topographically this formation consists of massive, The Hunt Fork shale that occurs in the upper Etivluk high, rugged mountains that are the backbone of the Valley 5 miles south of camp M-May 28-49 is hard and Brooks Range in the Killik-Etivluk Rivers region. The indurated, and erodes to form long low narrow well- general relief of these mountains is about 3,500 feet, and rounded ridges; the more arenaceous and silty beds form some peaks reach an altitude of 7,400 feet. prominent little mounds and small breaks in slope. The type locality of the Kanayut conglomerate is The shale is greenish brown and nonfossiliferous, and about 80 miles east of the upper Killik River near weathers a gray bronze. Fucoidal markings are present Shainin Lake in the central Brooks Range (Bowsher along the bedding planes. and Dutro, 1957). The section in the Killik-Etivluk In the upper Killik Valley where the largest exposures region is similar in lithology and thickness to the type of Hunt Fork shale occur, the rocks were not measured, section. but the formation is probably at least 3,500 to 5,000 Character and thickness. The Kanayut conglomerate feet thick. The upper contact between the Hunt is well exposed in the vicinity of camp M-Aug. 7-49. Fork and younger beds is gradational. Here the lower part of the formation is about 1,200 to Structurally the Hunt Fork formation is in a belt of 1,500 feet thick and is composed of intercalated thin complex folds and faults. Most of the incompetent and crossbedded dark-green to black shale siltstone and shale and slate is tightly folded and crushed and has a platy sandstone that weather dark-red brown. The regional south dip. The cleavage in general has a contact with the underlying Hunt Fork shale appears south dip; thus, both the south-dipping bedding and the to be gradational. This lower zone grades upward into cleavage form continuous dip slopes. Because of the a coarser clastic section of medium-bedded to massive uniformity of the formation, it is difficult to determine hard light-gray-green quartzite and sandstone with the magnitude of thrusting. Observations made along interbedded lenticular to massive-bedded quartzitic the upper Etivluk Valley indicate that the Hunt Fork conglomerates 15 to 30 feet thick. Small limonitic shale forms the core of a west-plunging anticline. specks, probably weathered pyrite crystals, are scattered Age and correlation. A few marine brachiopods, throughout the sandstone and quartzite, and in places pelecypods, gastropods, and fish teeth were found in are abundant enough to cause the rock to weather a the upper part of the formation. The age of these red brown. The coarser clastic section is approximately fossils was designated as Late Devonian by Dutro. 3,400 to 3,700 feet thick, and is characterized by moun­ Below are listed the fossils found. tain faces marked by steplike ledges. The ledges are

679606 O 63- 338 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

formed by massive layers of quartzite and quartzite Kanayut conglomerate Continued Feet conglomerate, between which the interbedded slate, 6. Quartzite and conglomerate, massive-bedded, shale, or siltstone has been eroded. medium-gray-green, medium-grained. Con­ glomerate pebbles are colored chert. In The conglomerate beds are composed predominantly some lenses the matrix and pebbles are chert of colored chert pebbles, but in many places the pebbles of the same color; these lenses are maroon are mostly black chert and white quartz. The pebbles and olive green. Chert pebbles are well are commonly subangular to round, and a few are angu­ rounded and }i to 1 in. in diameter. Quartz­ ite has some limonitic specks scattered lar. The general size range is from % to 1 inch in diam­ throughout ______925 eter. Some of the conglomerate beds are maroon or 5. Quartzite, medium- to massive-bedded, light olive green, and in these beds the pebbles and matrix are gray-green. Some small scattered lenses of of the same material and color. Generally these con­ conglomerate. Very clean subrounded spicuously colored conglomerates are small localized grains, with limonitic staining______360 4. Conglomerate, massive-bedded, medium-gray- lenses in the massive light-gray-green quartzitic con­ green. Conglomerate has quartzite matrix, glomerates. with minor amounts of light-gray-green Intercalated beds of maroon and green micaceous quartzite. Intercalated with the quartzite hackly-fractured shale, mudstone, siltstone, and sand­ are indurated thin-bedded maroon shale, siltstone, and sandstone containing pyrite stone form a very small part of the section. They concretions.______920 occur in beds ranging from 2 to 15 feet in thickness. 3. Quartzite and conglomerate, medium- to mas­ Pyrite nodules % inch to 3 inches in diameter are fairly sive-bedded, light-gray-green. Some inter­ common in the shale and siltstone. calated thin- to medium-bedded red sand­ stone and siltstone______400 Only nondiagnostic plant remains and coal were 2. Quartzite and sandstone, medium- to massive- found in the Kanayut conglomerate, in thin- to medium- bedded, light-gray to green, fine- to coarse­ bedded clean light-gray crossbedded sandstone. The grained; very crossbedded-______425 coal seams range from % inch to 2 inches in thickness, 1. Quartzite and quartzitic conglomerate, me­ and from 6 inches to 4 feet in length. This formation dium- to massive-bedded, light-gray-green. Some intercalated thin-bedded micaceous is predominantly of nonmarine origin. red sandstone, siltstone, and shale. Con­ glomerate pebbles subround to round, made Section of the Kanayut conglomerate measured in the mountains of colored chert, % to 1 in. in diameter..__ 920 on the east side of Killik River near camp M-Aug. 5-49 (pi. 44, column 5) Total.._._._.___._-.._...-_--_----- 4, 940 + Feet Kanayut conglomerate (section incomplete): Other good and accessible exposures of the Kanayut 10. Sandstone, thin- to medium-bedded, light- conglomerate were examined 5 miles south of Kurupa gray, fine-grained; speckled with limonitic Lake, at Outwash Creek 6 miles south of camp E-July specks; grains well rounded; weathers red 11-50, and 5 miles south of camp E-July 16-50 on brown ______220+ both sides of Ivotuk Creek. The Kanayut conglom­ 9. Quartzite, massive-bedded; medium-gray- green pebble conglomerate. Pebbles com­ erate at these localities is very similar in lithology to posed of colored chert and milky quartz; the rocks measured in the upper Killik valley, and in­ well rounded, % to % in. in diameter. Unit cludes siliceous sandstone, quartzite, highly colored weathers red brown..______80 chert-granule and grit conglomerate, pebble conglom­ 8. Siltstone, thin- to medium-bedded, maroon erate, interbedded shale, and well-indurated siltstone. and olive-green, hard, micaceous; inter- bedded with silty shale______40 The sandstone is thin to medium bedded, light gray, 7. Conglomerate, massive-bedded, gray-green; with light-red phases, fine to very fine grained, and matrix a medium-grained quartzite; pebbles well indurated to quartzitic. The conglomerate is well rounded, % to 1 in. in diameter, and massive bedded, with light-gray-green matrix; the composed of colored chert. In places the matrix is a maroon quartzite made of fine pebbles are red, green, gray, and black chert and milky chert. Intercalated with the quartzite and quartz, subangular to subround, and are between % conglomerate are thin beds of shale and silt- and % inch in diameter. The shale is medium gray, stone. Approximately 70 percent conglom­ erate, 25 percent quartzite, 5 percent shale light to dark red, and green, sandy and micaceous in and siltstone______.______650 part, fissile, moderately to well indurated. THE KILLIK-ETIVLUK RIVERS REGION 339

In the vicinity of Etivluk Lake the Kanayut con­ Section of Kanayut conglomerate (pi. 44> column 1) Feet glomerate was examined by Brosge and Reiser in 1950. Kanayut conglomerate (section incomplete): At this location the Kanayut conglomerate is almost 12. Sandstone, thin-bedded, light-gray; rusty- entirely sandstone, quartzite, and shale with very minor weathering. Very clean sandstone with amounts of grit and pebble conglomerate. The rocks limonitic specks throughout; some plant are mainly medium-bedded light-gray medium- to fossils and ripple marks__-___-_-_.______125 + coarse-grained angular quartz sandstone, and quartzite. 11. Sandstone, thin- to medium-bedded, white to light-gray, very hard; weathers red brown The sandstone contains some black chert grains and and has limonitic specks throughout; limo­ small lenses (1 to 6 in.) of dark-red medium-grained nitic specks appear to be weathered pyrite sandstone, and very sparse, scattered beds of typical cubes; intercalated with dark-gray hard conglomerate. The pebbles of the conglomerate are shale ______--______----______-_-_-_-- 240 10. Conglomerate, massive-bedded, light-gray- colored chert, milky quartz, and ironstone. Inter- green, lenticular, with quartzitic matrix; bedded with the sandstone and quartzite are thin beds well-rounded colored chert and milky quartz of black, green, and red shale. Plant fossils were pebbles % to % in. in diameter______80 found throughout the section but are nondiagnostic. 9. Quartzite, medium-bedded, light-gray-green, medium-grained; weathers red brown; a few The Kanayut conglomerate in the vicinity of Etivluk intercalated pebble-conglomerate lenses. Lake appears to be comformable and gradational with Pebbles are well rounded, gray, black, and the underlying Hunt Fork shale. A thickness of 9,000 white quartz, % to % in. in daimeter. Inter­ feet was estimated by using field dips, altitudes estab­ calated with the quartzite are maroon silt- lished by barometer, and horizontal distances computed stone and shale ______250 from aerial photographs. This measurement may be 8. Conglomerate, massive-bedded, light-gray- green; weathers red brown. Pebbles are in error by 1,000± feet because of the gradation into well rounded, black, gray, and white quartz, the Hunt Fork shale. % to % in. in diameter. The matrix is me­ dium- to coarse-grained gray-green quart­ Section of Kanayut conglomerate in the mountains west of Etivluk zite______-___-___---_--_--_------120 Lake at camp B-Aug. 10-50 7. Quartzite, medium- to massive-bedded, light- [Estimated by W. P. Brosg6 and H. N. Reiser] gray-green; weathers whitish gray. Quartz­ Feet ite is sparsely specked with limonite and is Quartzite and quartz sandstone, thick-bedded, light-gray intercalated with maroon siltstone and sand­ (80 percent); thin-bedded platy sandstone (10 percent); stone; 95 percent quartzite, 5 percent silt- and black clay shale (10 percent) ______4, 400 stone and sandstone.._____--______-_---- 720 Sandstone, thick-bedded, light-gray, fine- to medium- 6. Siltstone, thin- to medium-bedded, maroon and grained (40 percent); thin-bedded light-gray platy olive-green; intercalated with red and green medium-grained sandstone (40 percent); black to red micaceous shale. Some pyritic concretions clay shale (20 percent). Some scattered lenticular in the siltstone. 60 percent siltstone, 40 beds of quartzitic grit to pebble conglomerate. ___-.-. 4, 600 percent shale____,______-___-___-_-__.._- 120 Other good exposures of the Kanayut conglomerate 5. Quartzitic conglomerate, medium-bedded, light gray-green; weathers red brown. Quartzite are present from 2 miles south of camp M-May 28-49, is very clean and has limonitic specks on along the Etivluk River, to several miles north of fresh fractured surfaces. The conglomerate camp M-July 24^9 in Howard Pass (pi. 44, column occurs as lenses in the quartzite; the pebbles 1). Here the formation consists of considerably less are well rounded, gray, black, and white conglomerate than in the Killik and Kurupa River chert, and are % to 1 in. in diameter._____ 600 4. Quartzite, thin- to medium-bedded, light-gray- valleys. The typical lithology is massive-bedded green; weathers dark red brown; medium coarse- to medium-grained light-gray-green quartzite grained; crossbedded with ripple marks; and quartzitic conglomerate. The conglomerate peb­ intercalated with hard silty micaceous ma­ bles range in size from % to 1 inch in diameter, and are roon and olive-green shale and siltstone-___ 240 composed of subangular to subround quartz and colored 3. Quartzite, medium-bedded, light-gray-green, dark-red-brown weathering. Pebble con­ chert, the majority being black chert and milky quartz. glomerate occurs as lenses in the quartzite. Interbedded with the massive quartzite and conglo­ Conglomerate pebbles are well rounded, merate are thin-bedded light-gray rusty-weathering white, gray, and black chert. % to % in. in diameter. Between the beds of quartzite platy medium- to coarse-grained sandstone, and maroon are thin beds of hard indurated shale._____ 450 and olive-green micaceous shale, mudstone, siltstone, 2. Sandstone, thin-bedded, light-gray; weathers and sandstone. The thickness of the Kanayut south light red brown; very crossbedded, with limonitic specks throughout the mass. of camp M-May 28-49 was estimated to be more Intercalated with the sandstone is medium- than 5,000 feet. gray-brown shale.______--______------160 340 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Kanayut conglomerate Continued Feet and the overlying and underlying formations. It 1. Quartzite, medium-bedded to massive, light- probably ranges in thickness from 850 to 1,020 feet in gray-green; weathers dark red brown; medium grained. Conglomerate occurs as the mapped region. small lenses in the quartzite. The pebbles Occurrence. The Kayak shale crops out in two map- are white, gray, and black chert (% to 1 in. in pable belts in this region. The smaller belt, which is diameter), and are well rounded. The quartz­ approximately 18 miles long and 0.5 to 2 miles wide, is ite beds are intercalated with thin beds of in the southwest corner of the mapped area in the gray-brown hard shale ______560 vicinity of Howard Pass. The larger northern belt lies 3,665 in the northern part of the Brooks Range, trends west­ ward across the entire Killik-Etivluk region, and ranges Field studies indicate that the Kanayut conglomerate from 0.25 to 3 miles in width. Topographically the in the southern part of the mapped area is less conglom­ Kayak shale is characterized by saddles and by breaks eratic than to the north. This southward transition in slope between the shale and the more resistant from conglomerate to sandstone and quartzite indicates underlying and overlying formations. The Kayak shale a northerly source area for the Kanayut conglomerate. is a relatively incompetent unit, and has been greatly The Kanayut conglomerate, although more com­ deformed and sheared by folding and faulting. Over­ petent than the underlying rocks, forms a series of over­ turned and recumbent folds caused by thrusting from turned and appressed folds with a regional south dip. the south are common. Field evidence indicates that the entire northern front Character and thickness. The Kayak shale at Howard of the Kanayut conglomerate belt is a broken over­ Pass near camp M-July 24-49 is very similar to the turned anticline whose south limb has been thrust north­ type locality. In the Howard Pass area the rocks ward over the younger rocks. Associated with the consist of clay shale, arenaceous fossiliferous limestone, thrusting are high-angle reverse, block, normal, and and platy sandstone. Most of the sandstone is near transverse faults. the base of the section, and it grades upward into black Age and correlation. The Kanayut conglomerate in clay shale. Near the top of the section, the clay shale the Killik-Etivluk Rivers region lacks any diagnostic is calcareous and grades into thin-bedded highly fos­ fossil evidence that would establish its age. The lower siliferous, arenaceous rusty weathering fine to coarsely gradational contact with the Hunt Fork shale of Late crystalline limestone. Devonian age and the similarities between the section in this area and the Kanayut conglomerate in the Section of Kayak shale at Howard Pass (pi. 44: column 1) Shainin Lake area as described by Bowsher and Dutro Feel Kayak shale (section incomplete): (1957) indicate that this formation is Late Devonian in 6. Shale, black, clayey; weathers rusty. Near top of age. section is thin platy arenaceous limestone-___ 60 MISSISSIPPIAN SYSTEM 5. Covered; probably shale; thickness estimated.___ 480 4. Sandstone, massive, light-gray-brown; weathers In the Killik-Etivluk Rivers region, the Mississippian red brown; hard, fine-grained______50 system is represented by the marine Kayak shale and 3. Shale, thin-bedded, black; weathers black. Inter- the Lisburne group, the later being made up of the bedded with sandstone and siltstone which are Wachsmuth and Alapah limestones (Bowsher and thin bedded, gray brown, hard, siliceous, and crossbedded. ______125 Dutro, 1957). The aggregate thickness of these for­ 2. Shale, fissile, black; weathers brown; very hard; mations in this region is approximately 2,800 to 3,500 contains Yv to 1-in. ironstone concretions ___ 75 feet. The exposures of Kayak shale are confined to the 1. Sandstone, thin-bedded, medium-gray-brown; Brooks Range province, and the Lisburne group is weathers dark red brown; crossbedded, hard- exposed in the Brooks Range and in isolated mountains breaks into flat plates; contains a few invertebrate fossils ______--_--__-_------70 and ridges in the southern foothills section. 860+ KAYAK SHALE The type locality of the Kayak shale is about 90 In the Killik valley near camp M-Aug. 23-49, good miles east of the Killik River in the central Brooks exposures of the Kayak shale occur in the northern belt. Range at the confluence of Alapah and Kayak Creeks, Here the rocks are very similar to those of the type 4 miles south of Shainin Lake (Bowsher and Dutro, locality, and a complete section was measured. The 1957). The Kayak shale in the Killik-Etivluk region is contact with the older rocks is a thrust fault, and the a- readily identifiable formation, owing to its topographic contact with the overlying rocks appears to be con­ expression and to the contrast in lithology between it formable. THE KILLIK-ETIVLTJK RIVERS REGION; 341

Section of Kayak shale in the Killik valley (pi. 44, column 5) exposures are lithologically similar to the Kayak sec­ Wachsmuth limestone. Feel tions previously discussed. Kayak shale: Age and correlation. The Kayak shale is Early 5. Limestone, thin-bedded, medium-gray, rusty- Mississippian in age (Bowsher and Dutro, 1957). In weathering, very arenaceous, medium- to this region, as in the type locality near Shainin Lake, coarse-crystalline, very fossiliferous (USGS the upper part of the formation contains fossils in Paleozoic loc. 14087). This limestone may be the top of the Kayak formation or it may be abundance. Megafauna collections, including corals, basal Wachsmuth limestone formation. _____ 30 bryozoans, crinoid debris, brachipods, pelecypods, and 4. Shale, thin-bedded, black, dark-gray-black ostracodes, are given in table 3. These collections, weathering; soft with some small ironstone indicative of Early Mississippian age, were identified concretions /zl to 1 in. in diameter. Soft clay- by Dutro. ball concretions and thin-bedded limestone are USBURNE GROUP sparsely scattered through the shale. ______65 3. Limestone, thin-bedded, medium-gray; weathers The type locality of the Lisburne limestone is at the bright red brown; medium crystalline, arena­ head of the Anaktuvuk River, near Anaktuvuk Pass, ceous, fossiliferous, and platy______75 in the central Brooks Range (Schrader, 1904, p. 71-72). 2. Shale, thin-bedded, black, rusty-weathering, fis­ Bowsher and Dutro (1957) raised this formation to the sile; with flat fossiliferous limestone nodules, 1 to 8 in. in length, which weather a light buff Lisburne group, which is divided into two formations, gray. Shale is intercalated with thin-bedded the Wachsmuth limestone (Early Mississippian) and dark-gray fine-grained sandstone and siltstone Alapah limestone (Late Mississippian). The type local­ (95 percent shale, 5 percent standstone and ities of the Wachsmuth and the Alapah limestones are siltstone)______700 in the Shainin Lake area, central Brooks Range, 1. Sandstone, thin-bedded, medium-gray-brown, fine-grained. Intercalated with the sandstone is Alaska. hard black red-weathering fissile shale_-______150 The Lisburne group was mapped as one unit at most localities in the Killik-Etivluk Rivers region in the Total.... 1,020 fieldwork done prior to 1951. Since then much faunal Kanayut conglomerate. and stratigraphic work has been done on the Lisburne group, and, as a result, it has been possible to rework The Kayak shale was examined in detail at five the earlier field data and separate the Lisburne group localities between Kurupa Lake and Outuk Creek. into two formations at some localities (pi. 43). There At all localities it is similar to the Kayak shale of the was not sufficient faunal or lithologic data to differen­ type locality. It is predominantly silty shale, dark- tiate the formations at other localities shown as Lisburne gray to black, highly micaceous in part, well indurated, group undifferentiated (pi. 43), or else these localities platy to fissile, with interbedded thin siltstone and were not examined in the field and mapping was done sandy layers and ironstone concretions; 14 samples of from aerial photographs. shale were barren of microfossils. The remainder of The Lisburne group crops out in five main west- the section contains minor amounts of dark-gray to trending belts and in several scattered outliers along black unfossiliferous clay shale, very fine grained sand­ fault zones in the Killik-Etivluk Rivers region. These stone, and reddish-brown coquina and hydroclastic belts of outcrop are discussed in order from south to limestone. A reddish-brown weathering is conspicuous north. in parts of the section. The southernmost belt is in the vicinity of Howard Section from Outuk Creek about 3 miles southwest of camp E-July Pass and camp M-July 24-49, and north of Flora Creek. 16-50 (pi. 44, column 3) It comprises a group of low well-rounded ridges on the Kayak shale, (section incomplete): Feet south flank of the belt of mountains that begins about 2. Clay shale, thin-bedded, black, hackly-fracturing, 7 miles east of camp M-July 24-49 and extends west- noncalcareous; with minor amounts of intercal­ northwest across Howard Pass and thence beyond the ated thin-bedded medium gray-brown hard western limit of this region to form part of the Howard siliceous siltstone____--_-_-____-_-_-__-_-___ 750 1. Sandstone, thin-bedded, light gray-brown; Hills. This belt is approximately 1 mile wide, and has weathers red brown; with intercalated siltstone, a discontinuous length of about 15 miles in the mapped which is thin bedded, very hard, and siliceous._ 100 area. The second, or next northerly, belt, which is approxi­ Total. 850 mately along lat 68°21' N., and parallel to the front Good exposures of the Kayak shale were found in the of the Brooks Range, is made up of sharp rugged ridges northern belt on the Etivluk River, along Fay Creek, with relief ranging from 1,000 to 2,600 feet. These and several miles east of camp M-May 28-^19. These resistant ridges, which are cut by the Killik River 342 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

TABLE 3. Fossils of Kayak shale [Identified by J. T. Dutro, Jr. Field samples 50 ARe 128,158, Kurupa Lake; 50 ARe 196, 207, Kutchiakruak Creek; 50 ARe 224, 232, Itovuk Creek; 49 AMg 89,49 ADt 108,114,116, Howard Pass; 49 ALa 156,49 ADt 19, Fay Creek; 49 AMg 104,118, Killik River]

Field sample (US OS Paleozoic locality)

ARe128e50 ARe224a50 ARe224c50 AMg10449 AMg11849 Fossil (12322) si ARe15850 (12324) ARe19650 (12326) ARe20750 (12327) (12329) (12330) ARe23250 (12331) AMg8949 (14080) ADt10849 (14081) ADt11449 (14082) ALa15649 (14083) (14084) ADt1949 (14085) ADt11649 (14086) (14087)

Crinoid debris ______X X X X X X X X X Platycrinid columnals ...... X Rugose coral, undet...... X X X Fenestrate bryozoan, undet ___ - X X X X X X X Leptaena of. L. analoga (Phillips). X X X X ? Avonia? sp ______. X X Camarotoechia afl. C. chouteauen- *i* Weller ~ X X sp...... X X ? X X X X X X Spiriter afl. S. tornacensis de X X X X X X X X X afl. S. minnewankensis Shimer. X sp. -.._.._.....______. X X X X X Cleiothyrodinasv- - .-. ------X X ? X X X X Schizodus sp...... Pelecypod, undet ____ ...... X X X X X Platyceras sp. ___ ...... X X X Ostracodes, undet ______.. X X X X X X X Fish teeth, undet ...... X

(fig. 59), Imnaitchiak Creek, and the upper Kurupa of about 0.75 and 2.25 square miles. The third and River and tributaries, form a nearly continuous out­ smallest fault block crops out 3 miles southwest of camp crop belt extending from Kaishak Hill on the east side M-June 11-49 and about 2.5 miles west of the Etivluk of the Killik River to a point about 34 miles west at River. the head of Nogak Creek. At the head of Nogak Creek The fourth belt of Lisburne group rocks forms a the Lisburne group is faulted out and is overlain by west-trending, discontinuous series of prominent rugged the older Kayak shale and Kanayut conglomerate. limestone ridges, approximately along lat 68°30' to The Lisburne group apparently is not exposed along 68°35' N., that coincide with a major west-trending the trend of this belt between the head of Nogak Creek fault or fault zone. The belt extends from the East and the Nigu River. The area between Ivotuk Creek Fork of the Etivluk River to the western boundary of and the Nigu River has been examined only on aerial the mapped region. Between the East Fork of the photographs; so it is possible that some small isolated Etivluk River and the western side of the Iteriak Creek fault blocks of the Lisburne group are present in the valley, a distance of about 13 miles, these ridges are area but have not been recognized. On the east side approximately 0.5 to 0.75 mile wide, and their strike is of the Nigu River valley, the Lisburne group reappears askew to the general trend of the belt. The Lisburne in small well-rounded scattered hills and isolated stream group does not crop out near Outwash Creek, but the cutbanks, and from this point the Lisburne extends probable western extension of this belt is in a series of westward along lat 68°21' N., across the Etivluk River outcrops that form low, well-rounded ridges which be­ near Fay Creek. The width of this outcrop belt is gin 2.5 miles west of Outwash Creek and trend north­ 1.5 to 3 miles near the Killik River; farther west it is westward across the Etivluk River (near camp M-June generally narrow but varies in width from narrow rubble 14-49) to form Puvakrat Ridge. traces to as much as 1 mile. The fifth and farthest north belt in which the Lis­ The third belt of the Lisburne group is rather indis­ burne group is exposed lies approximately along lat tinct and is composed of three small thrust blocks 68°36' N. The major outcrops are on Lisburne Ridge, approximately along lat 68°27' N. Between Iteriak a narrow northwest-trending hogback, rounded in part, and Outwash Creeks the two large fault blocks form that coincides with a major fault. This ridge, which prominent sharp hogbacks that have outcrop areas has a relief of 600 to 1,000 feet, begins about 2 miles FIGURE 59. Oblique view of overturned fold in the limestone of the Lisburne group, showing phosphate locality in the Alapah limestone. ("Rs) Triassic Shublik formation; (Pns) Permian unnamed unitin Nuka- Ridge area and the Siksikpuk formation; (MIa) Mississippian Lisburne group, Alapah limestone; (Mlw) Wachsmuth limestone. Photograph by U.S. Navy.

OO 344 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 THE KILLIK-ETIVLUK RIVERS REGION, 345 west of the Etivluk Kiver and 4 miles north of camp Wachsmuth limestone Continued Feet M-June 14-49 and extends northwest into the Ipnavik 1. Limestone, thin- to medium-bedded, dark-gray to black, weathers light gray, hydroclastic; has a River drainage. The width of the Lisburne group out­ strong fetid odor when fractured. Throughout crop across the strike is approximately 0.5 mile. Four the limestone are dark-gray to black chert nod­ small and inconspicuous outcrops of the Lisburne group ules. Approximately 5 per cent of unit is chert-. 400 occur in this belt near the Oolamnagavik River and ----.------.------.-. 1, 115 Pingaluligit Mountain, about 45 to 55 miles east of the Kayak shale. Etivluk River. These exposures, with the exception of The Wachsmuth limestone examined in the Howard the one in a bluff on the Oolamnagavik River, are on Pass area is lithologically similar to the limestone on knobs or low mounds that are largely covered with the Killik River. Here the basal part of the Wachs­ frost-heaved rubble and show very little rock in place. muth is a thin-bedded platy arenaceous rusty-weather­ WACHSMTJTH LIMESTONE ing, very fossiliferous limestone. The lower contact The lower part of the Lisburne group, the Wachs- appears to be conformable with the Kayak shale. muth limestone, was examined at six localities in the These particular limestones are lithologically similar to Killik-Etivluk Rivers region: Killik River near camp the lower formation (unnamed) of the Lisburne group M-Aug. 23-49, near the head of Imnaitchiak Creek, mapped by E. G. Sable and Mangus on the Upper Kurupa Lake near camp E-July 1-50, Howard Pass Utukok-Kokolik Rivers divide in 1950. The upper near camp M-July 24-49, Fay Creek west of camp part is massive and marmarized by mafic intrusives in M-May 28-49, and on Lisburne Ridge. contact with the limestone. Character and thickness. The Wachsmuth limestone, Composite section of the Wachsmuth limestone at Howard in general, is thin to thick bedded, fine to coarsely Pass (pi. 44, column 1) crystalline, hydroclastic in part, arenaceous in part, Wachsmuth limestone: (section incomplete) : Feet dolomitic in part, dark gray on fresh surfaces, light to 5. Marble, medium-bedded to massive, light-gray; medium gray on weathered surfaces, tripolitic, and weathers white and very smooth; in contact fossiliferous; it commonly has a fetid odor when freshly with gabbro______-__-______------__ 85 broken. Dark-gray to black nodular or thin irregu­ 4. Limestone, medium-bedded to massive, medium- gray, weathers light gray; tripolitic and rough on larly bedded chert is common throughout the limestone, weathered surfaces; some of the beds are dolo- but forms a minor part of the section. A few thin mitic. ___--__-__-_-_-_----_------280 units of dark-gray limy silty shale and dark-gray 3. Limestone, thin- to medium-bedded, dark-gray to medium-grained calcareous sandstone are interbedded black; weathers light gray and very smooth on and are uncommon. The contact of the Wachsmuth surface; very fine grained; has fetid odor_ --__. 160 2. Limestone, thin-bedded, medium-crystalline, me­ limestone with the underlying Kayak shale appears to dium-gray; weathers light gray and in flat platy be comformable. slabs with rough surfaces; crinoidal. Near the A complete section of the Wachsmuth limestone was middle of this unit is 50 feet of silty dark-gray not found at any of the six localities. Partial sections, limy shale__---_------200 ranging from 985 to 1,115 feet, were measured; the 1. Limestone, thin-bedded, medium-gray; weathers rusty red and in platy pieces; arenaceous, fossilif­ writers believe that the Wachsmuth is between 1,200 erous; intercalated thin-bedded medium- and 1,500 feet thick in this region. grained dark-gray rusty calcareous sandstone ._ 250 Composite section of the Wachsmuth limestone near the Killik Total---.-.------975 River, southwest of camp M-August 23-49 (pi. 44, column 5) Kayak shale. Wachsmuth limestone (section incomplete): feet West of camp M-May 28-49, on Fay Creek, only 5. Limestone, massive-bedded, medium-gray; weath­ the lower part of the Wachsmuth limestone crops out. ers light gray; hydroclastic and coarsely crystal­ line; upon fresh fracture gives off a strong fetid It consists of thin- to medium-bedded dark-gray fer­ odor; contains no chert; some beds are dolomitic- 115 ruginous-weathering arenaceous fossiliferous fine- to 4. Limestone, massive-bedded, light-gray, weathers medium-grained limestone. white gray; coarsely crystalline; upon fresh The northernmost exposure of the Wachsmuth that fracture gives off fetid odor; contains nodular was examined is on Lisburne Ridge. Here the lime­ dark-gray chert.-----__-_____-______-____ 200 3. Limestone, medium- to massive-bedded, medium- stone is medium bedded, finely crystalline and dolo­ to dark-gray, weathers light gray, coarsely crys­ mitic, with numerous bands and nodules of chert. talline; gives off strong fetid odor when frac­ Because the rock is silicified, weathered surfaces are tured; fossiliferous; nodular dark-gray to black very sharp and rough. A strong fetid odor is given chert inclusions.______150 2. Limestone, medium- to massive-bedded, dark- off when the rock is freshly fractured. The limestone gray; weathers light gray; fine grained; inter­ is light medium gray and the associated chert is dark calated with ropey bedded dark-gray chert _ _ _ _ 250 blue gray to black.

679606 O 63 4 346 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 Age and correlation. The Wachsmuth limestone in and Dutro, 1957). Thefossil collections from this region this region is similar in thickness, lithology, and fauna consist mainly of corals, bryozoans, and brachiopods; they to that in the type locality near Shainin Lake (Bowsher were identified as early Mississippian by Dutro (table 4). TABLE 4. Fossils of Lisburne group [Identified by J. T. Dutro, Jr. Field samples 50 ACh 41F, 46 ATh 8,46 ACh 10f, Imnaitchiak .Creek; 49 AMg 115,49 ADt 131, 49 ADt 132, Killlk Rjver; 50 ARe 170b, 50 AE 16,12,21, Kurupa Lake; 49 AMg 5,1H miles east of Camp M-May 28-49; 49 AMg 11, % mile northeast of Camp M-May 28-49; 49 ALa 10,161, Fay Creek]

Alapah limestone Wachsmuth limestone

Field sample (USGS Paleozoic locality) Field sample (USGS Paleozoic locality)

ACb41F50(12340) Fossil ATb(12348)468 46AChlOf(12350) Fossil URel70b(12325) AMg(14093)49115 49ADt(14094)131 49ADt(14095)132 d a. ALa(14091)4910 C- *H 10 2 s 2 S bo be « w W S 4 <1 s<1 <1 S s S S 9 $ §

Rugose corals, indet X X X "Zaphrentis" konincki X X X (s. 1.) Milne Ed­ wards and Haine. Lithostrotionld coral, un­ X X det. Bryozoan, undet ...... X X Chonetes sp ______X X X "Productus" sp _____ X X Spirifer cf. S. subaequa- X lis Hall, Buxtonia? sp ______X X afl. S. missouriensis. X Overtonia"! sp...... X X Swallow, Krotoviaf sp...... X afl. tenuicostatus Hall X X Linoproductus afl. L. lyelli sp.. - X X X X Verneuil) X Morefieldella'f sp...... X X Athyris cf . A. lamellosa X Rhynchonellid brachio- X (Leveille) pod, undet s Spirifer afl. S. adonis Bell, "X X sp...... X X X X X Punctospirifer afl. P. X subtexta (White) Brachythyris? sp...... X X Athyrisf sp ...... X X X Eumetriasp...... X Dielasma sp...... X X X Gastropod, n. gen., n. sp.. X X Ostracodes, undet ...... X Fish teeth, undet ...... X

ALAPAH I/IMESTONE bedded chert. A fetid odor is characteristic of most The upper part of the Lisburne group, the Alapah of the limestone. Dark-gray to black clay shale and limestone, was examined and mapped at several locali­ limy shale make up a minor part of the section. ties in this region. Good exposures of Alapah lime­ Section of the Alapah limestone just south of Kurupa Lake (pi. stone were examined along the Killik valley in the 44> column 4) vicinity of camp M-Aug. 23-49, at Kurupa Lake in Alapah limestone (section incomplete) : the area of camp E-July 1-50, and on the Etivluk Fault. Feet River west of camp M-June 14-49. The most exten­ 16. Limestone, medium- to massive-bedded, medium- sive exposures are along the northern front of the Brooks gray, cherty; interbedded medium-gray re- crystallized coarsely crystalline limestone.-... 50 Range where the Alapah is in contact with the Wachs­ 15. Shale, dark-gray, calcareous, with abundant muth limestone. Many small fault blocks, in exposures white mica; intercalated with dark-gray shaly ranging in size from 30 square feet to several square miles, limestone.. -______-_.__-_---_ 50 occur as far as 15 miles north of the main outcrop belt. 14. Limestone, medium-bedded, dark-gray, crinoidal. 7 13. Shale and limestone, interbedded; limestone is Character and thickness. Near the Killik River the dark gray, crinoidal, coarsely crystalline; shale Alapah limestone is composed, in descending order, of is black. ______15 dark-gray calcareous shale, medium-bedded dark-gray 12. Limestone, medium-bedded, dark-gray, crinoidal. 15 to black limestone, shaly limestone, and fine- to 11. Limestone, medium-bedded, black; interbedded medium-grained black nodular cherty limestone. The with black sandy limestone and shale. Abun­ dant bryozoa, crinoid columnals, and brachio- contact with the Wachsmuth limestone is tentatively 15 placed at the base of the black nodular cherty limestone. 10. Limestone, thin-bedded, medium-gray, blocky; The Alapah limestone at Kurupa Lake is predomi­ weathers buff to light gray; crinoidal and bio- clastic, becoming shaly upward. _._.____._-_ 135 nantly light to medium gray massive fossiliferous 9. Limestone, light-gray, coarsely crystalline; inter­ limestone, cherty limestone commonly with hydro- calated with medium-bedded medium-gray clastic and crinoidal facies, and medium-gray to black chert.-...... ----. _ ...... __ . 80 THE KILLIK-ETIVLIIK RIVERS REGION 347

Alapah limestone Continued feet tered localities in the northernmost part of the Brooks 8. Chert, thin-bedded, black; interbedded with Range and the southern part of the southern foothills black siliceous shale and black fine-grained tripolitic limestone. ______50 section. The structure is complex and the exposures 7. Limestone, medium - bedded, medium - gray, are not expecially good in most of this part of the blocky, cherty, grading into light-gray crys­ region. These factors, in addition to the lithologic talline dolomitic limestone with interbedded similarity between these formations and the Triassic chert. The limestone has black specks which and Jurassic formations, make detailed differentiation are probably organic..______25 6. Chert, thin-bedded, black; grades into light- of the Carboniferous and Permian rocks very diffucult. , gray coarsely crystalline limestone and dolomite _ _ _ 100 The type locality of the Siksikpuk formation is in 5. Limestone, medium-bedded, dark-gray to black, the southern foothills section along the headwaters of with bands of black chert. Limestone has the Siksikpuk River about 50 miles east of the Killik bituminous material init.______35 River (Patton, 1957). The type locality of the un­ 4. Limestone, medium- to massive-bedded, light- gray, medium-crystalline, crinoidal, bioclastic. 200 named Permian and Carboniferous unit is in the area 3. Shale, dark-gray, silty______15 of Nuka Ridge along the headwaters of the Nuka 2. Limestone, massive-bedded, medium-gray to River about 85 miles west of the Etivluk River (I. L. gray-black, with dark-gray chert that has a Tailleur, oral communication). ropey anastomosing structure. In places the chert is 3 feet thick______40 The Siksikpuk formation and (or) the unnamed 1. Limestone, massive - bedded, medium - gray, Carboniferous and Permian unit crop out in two general cherty, blocky, crystalline. Unit has pod- areas within the Killik-Etivluk Rivers region. One shaped chert nodules and is interbedded with area is just east of Howard Pass where two west- medium-bedded black chert______25 trending belts of these formations have been mapped; Total______857 one about 3 miles north of Flora Creek on the west Rest of section covered. side of Isikut Mountain, and the other about 4 miles The Alapah limestone exposed near the Etivluk south of Flora Creek and on the north side of likhkluk River east of camp M-May 28-49 and northwest of Mountain. The exposures in these belts are on small camp M-Jime 14-49 is quite different in lithology from ridges and mounds, flanked by more prominent rugged the rocks previously described. At these localities the ridges and hills formed by the more resistant rocks Alapah consists predominantly of thin- to medium- of the Lisburne group and the overlying TriaSsic Shub- bedded light- to dark-gray moderately fossiliferous lik formation. The second area of these formations chert; the chert is interbedded with thin-bedded light- is a west-trending irregular belt between lat 68°20' N. gray medium-crystalline crinoidal limestone. The and 68°35' N. Within this belt many small isolated change in facies from predominantly limestone to exposures, most of which are too small to show on predominantly chert appears to occur in the area be­ plate 43, occur as mounds or rubble-covered hills tween Iteriak Creek and the Etivluk River. surrounded by tundra. In this belt many larger areas The true thickness of the Alapah limestone was not are mapped as Carboniferous, Permian, Triassic, and determined because of complex structure and the lack Jurassic rocks undifferentiated; within these areas the of time for detailed work. A minimum of 857 feet was rocks of these ages are generally poorly exposed and measured, and the total thickness is estimated to be structurally complex, and are similar in lithology; it about 1,200 to 1,400 feet. is difficult or impossible to delimit the formations The maximum thickness for the entire Lisburne accurately. The areas of undifferentiated rocks include group in the mapped region is estimated to be 2,000 small and large rounded hills, low sharp hogbacks, and to 2,500 feet. small bluffs and creek-bank exposures of rock. In Age and correlation. The Alapah limestone in this general this belt ranges from 1 to 10 miles in width. region, except in the two localities near the Etivluk SIKSIKPUK: FORMATION River, is similar to that in the type section near Shainin Character and thickness. The Siksikpuk formation Lake (Bowsher and Dutro, 1957). The fossil col­ consists mainly of thin-bedded red, green, yellow, and lections, including corals, brachiopods, and gastropods, black chert, siliceous siltstone, and shale. Very fine from this region were identified as Late Mississippian grained limestone, calcilutite, and calcareous cannon- by Dutro (table 4). ball concretions are interbedded with the shale and CARBONIFEROUS AND PERMIAN SYSTEMS chert. A partial section of the Siksikpuk formation was In the Killik-Etivluk Rivers region the Carbonif­ measured along the east bank of the Nigu River, at erous and Permian systems are represented by the Nigu Bluff, 4 miles south of the confluence of the Etivluk Siksikpuk formation and an unnamed Carboniferous and Nigu Rivers (pi. 44, column 2). Here some of the and Permian unit. These rocks are exposed at scat­ section apparently is missing as a result of thrust 348 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 faulting. The rocks are typical interbedded red, green, camp E-July 16-50 on Ivotuk Creek consists of sand­ yellow, and gray chert, siliceous siltstone, and shale. A stone made up of white and clear coarse subangular to detail description of the section at Nigu Bluff is given below. subround quartz grams with calcareous cement. Section of Siksikpuk formation at Nigu Bluff Age and correlation. No fossils were found in this Mafic igneous sill. Feet formation in the mapped region. The age and correla­ Siksikpuk formation (section incomplete): 5. Chert, thin-bedded, yellow, maroon, and green, tion where established by analogy with the formation fine-grained, porcellainous; in contact with sill in the Nuka Ridge area. and heavily mineralized with pyrite cubes and TRIASSIC SYSTEM pyrite concretions.______60 SHUKLIK FORMATION 4. Claystone, thin-bedded, yellow-ochre, appears to be bentonitic.--_-____-_-___-__-___---___-._ 2 The Triassic system in the Killik-Etivluk Rivers 3. Shale, thin-bedded, dark-gray to black, contains region is represented by the Shublik formation. The fine-grained dark-gray limestone, and cannon- type locality of the Shublik formation is on Shublik ball concretions 1 to 8 in. in diameter. Thin- Island in the Canning River, about 200 miles northeast bedded light-gray hard calcilutite, having con- of the KiUik River (Leffingwell, 1919, p. 115-119). choidal fracture, is interbedded with the shale_ _ 200 2. Chert, thin-bedded, buff and green; has a jasperoid The Shublik formation at the type locality is described appearance; malachite-green coating covers as Upper Triassic, but in the Killik-Etivluk region this weathered surfaces and bedding planes----...- 100 formation includes both Mid die and Upper Triassic rocks. 1. Shale, thin-bedded, phyllitic, black and green; Occurrence. The Shublik formation is exposed many grades laterally into thin-bedded chert with carbonate veins. Minor amounts of maroon places in the southern foothills section and at several chert and shale_------80 localities in the Brooks Range. In general, two areas Total....______442 of outcrops can be outlined: one in the vicinity of Age and correlation. The megafauna described by Howard Pass, and the other a west-trending belt in the Patton (1957) from the type section of the Siksikpuk southern part of the southern foothills section. In the formation was not found in the Killik-Etivluk Rivers Howard Pass area, there are two west-trending belts of region. Of 17 samples from the colored shale that outcrop: one along Rough Mountain Creek, 4 miles were processed for microfossils, seven were barren. south of Flora Creek, and another about 2 miles north A red-stained microfauna, including conodonts, radio- of Flora and Fauna Creeks. These belts are about 0.5 larians, and the arenaceous Foraminifera Glomospirella mile in width; the southern one is about 4 miles long sp., Ammobaculites? sp., and Involutina? sp., was and the northern one is approximately 13 miles in identified from these samples (table 5) by Bergquist, length. The west-trending belt of Shublik in the and on the basis of this fauna and the similarity of southern foothills is in the structurally complex area lithology between the rocks in this region and in the adjacent to the northern front of the Brooks Range, and type section, the age of the Siksikpuk formation in this is approximately 11 to 17 miles in width. Within this region has been established. The total thickness of belt the Shublik formation is so complicated by faulting of the formation has not been determined, but it is and folding that it is practically impossible to map all probably at least 500 feet. the exposures separately; thus, areas of outcrops in UNNAMED CARBONIFEROUS AND PERMIAN UNIT which rocks of Shublik and other formations are com­ Character and thickness. The unnamed Carbon­ plexly intermixed have been mapped as undifferentiated iferous and Permian unit is lithologically similar to Siksikpuk and Shublik, Shublik and Tiglukpuk, and Permian rocks in the area of Nuka Ridge in the head­ Shublik, Tiglukpuk and Okpikruak formations. waters of the Nuka River, a north-flowing tributary Character and thickness. The southernmost belt of of the Colville River, about 85 miles west of the Etivluk Shublik formation at Howard Pass is metamorphosed River (I. L. Tailleur, oral communication). Inasmuch to some extent by a large intrusive, but consists of dark as the outcrops of this formation are poor and rare clay shale, black, yellow, and green chert, and thin- in the mapped region, little information could be bedded very fine grained light-gray buff-weathering obtained on the lithology, thickness, and fauna. Monotis sp.-bearing limestone. The northern belt of A small isolated outcrop of the unnamed Carbonif­ this formation in the Howard Pass area consists of erous and Permian unit was found 1.3 miles south of unctuous claystone with pencil fracture, of calcilutite, camp C-June 16-50 and 0.3 mile west of Imnaitchiak and of thin-bedded cherty dark-gray limestones con­ Creek. The rocks are medium-bedded pale-yellow to taining Monotis sp. light-gray clear-quartz granule to small pebble con­ The Shublik formation within the large belt in the glomerate, in part calcareous; fine- to medium-grained southern foothills is lithologically similar to that for­ limy sandstone; and some finely crystalline limestone. mation in the Howard Pass area. It consists of thin- to An exposure of this formation immediately east of thick-bedded light-gray to light-tan sublithographic, THE KILLIK-ETIVLUK KIVERS REGION 349

Table 5 .-MicrofossiI check list for Paleozoic and early Mesozoic formations

[R indicates 1 to 12 specimens; C, 13 to 25 specimens; and A, over 25 specimens. Fossils listed stratipraphical)y but not to scale. Fossils identified by H. R. Bergquist and II. N. TappanJ

Lower Cretaceous Jurassic Triassic Permian

Fossil Torok formation Okpikruak Tiglukpuk Shublik Siksikpuk formation formation formation formation Fortress Mountain formation (unfossi 1 i ferous

R C R R R ^S$5Sgg8fJifSs| JsSi&SSjSj m B. vitta Nauss R R immR B. anomalocoelia Tappan mmR Jaculella elliptica (Deecke) R 1 R A R A Involut ina 7 sp. i m m m I. rotalaria (Loeblich and R Tappan PI R A R R Glomospire 1 la sp. m IIP! Hap lophragmoides R R topagorukens is Tappan 1 iiii A R Aamobaculitesl sp. ill Pi Gaudryina kelleri Tappan R

G. tailleuri Tappan R « Trochaamina eilete Tappan ifR mR Lenticulina sp. mR Marginulina gatesi Tappan mR mR M. planiuscula (Reuss) R R (1 11 ttanushuke lla umiatensis R R R R Tappan El i! i! m Gavelinella awunensis Tappan inR mR Eurycheilostoma robinsonae R Tappan m Pallaimorphina ruckerae R R R R Tappan P PHI PI Gyroidina loetterlei Tappan mmwmR R R Dictyomitra sp. R R if R R R Lithocampe sp. m m m Radioiaria unidentified mR mmC R mR R Conodonts unidentified IP! partly silty fossiliferous limestone that sporadically Killik River, the Shublik formation lies beneath the contains small amounts of phosphate pebbles, medium- Alapah limestone in fault relationship, and the follow­ greenish-gray to black bedded chert, yellow to greenish ing incomplete composite section was measured (pi. 45, chert, and medium-gray to black silty and clay shale column 1). that is in part fossiliferous. Float and pebbles of Composite section of Shublik formation at Killik River brownish to black oil shale are not uncommon, but oil Alapah limestone. shale has been found in place only near Imnaitchiak Fault. pe«t Creek about 1.5 miles south of camp C-May 28-46. Shublik formation (section incomplete): 6. Chert, thin-bedded, black, hackly.______35 The oil shale cannot be positively assigned to the 5. Limestone, thin-bedded, black, silty; has small Shublik formation, but the geologic relationship here phosphatic nodules % to 1 in. in diameter which and elsewhere strongly indicate this age. A few thin- weather with a bluish-white bloom. Halobia to medium-bedded fine- to medium-grained micaceous sp. and Monotis sp. present--__-_-_-_-_-_-___ 25 graywacke sandstone beds possibly also should be in 4. Chert, thin-bedded, olive-green to black; weathers eluded in the unit. rusty. Near top a light-gray, buff- or cream- weathering extremely fossiliferous calcilutite Several miles west of camp M-Aug. 23-49 on the contains Monotis sp__-_------40 350 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Shublik formation Continued Feet limestone, cherty limestone, chert, and silty clay shale. 3. Chert, thin-bedded, black; weathers rusty brown; It was not possible to determine the precise strati- hackly-fracturing; thin inter beds of silty black shale-______45 graphic position of the fossiliferous horizons within the 2. Chert, thin-bedded, dark-gray to black; fossilif- Triassic section. Monotis subdrcularis Gabb and erous containing Posidonia sp.; intercalated Halobia sp., pelecypods of Late Triassic age, are the black silty shale and siltstone; limestone nodules most common fossils, but a few others are present. 0.5 to 2 feet in diameter______60 Several fossils, which are of early Middle Triassic 1. Limestone and chert, thin-bedded, cream to buff; the yellow silty chert appears to be porcellainous (Anisian) age, were found west of camp M-Aug. 23-49 and is inter bedded with shale that has a bright on the Killik River. A list of the megafossils, identified yellow bloom______20 by Kummel and Imlay, is given in table 6. Total.______225 Fourteen samples from the mapped region were ex­ Age and correlation. In the Killik-Etivluk Rivers amined for microfossils. All samples were barren. region the geologists in the field were unable to arrive JURASSIC SYSTEM at incontrovertible distinctions between the abundant TIQLUKPTTK FORMATION chert sequences of Permian through Jurassic ages, all The Jurassic Tiglukpuk formation is present in the of which probably are represented. Wide ranges of Killik-Etivluk Rivers region, but is poorly exposed and color and other physical characteristics were observed not well delimited either stratigraphically or areally. within single chert outcrops, and, in addition to the The type locality for this formation is about 50 miles normal expectable lithological variation, the variations east of the Killik River at approximately lat 68°22/ N., seem to be in part related to degree of fracturing and along the east side of Tiglukpuk Creek, a tributary of weathering, to type of exposure (stream cut versus hill­ the Siksikpuk River. (Patton, 1956a.) top), and to associated rocks that might contribute Occurrence. Rocks that are mapped as Tiglukpuk surface-staining material. At a few localities, unfossil- formation form several ridges in the southern part of iferous chert interbedded or associated with fossilifer- the southern foothills section between the Killik and ous rocks of the Shublik formation establishes a Triassic Kurupa Rivers. Elsewhere in the southern foothills, age for those sequences. the Tiglukpuk formation probably is present in the Fossiliferous beds are common in the Shublik forma­ structurally complex belt between the front of the tion and many are coquinoid. Megafossils occur in the Brooks Range and lat 68°40/ N. Within this belt the

TABLE 6. Fossils of Shublik formation [Identifications by Bernard Kummel and R. W. Imlay. Field samples 49 AMg 29F, 49 ADt 23F, Etivluk River; 49 AMg 88F, Howard Pass; 50 AE 7, Akmalik Creek; 50 AE 53, 56, Kutchiakruak Creek; 50 AE 82, Ivotuk Creek; 50 ARe 35, 36, 50 ACh 37F, Travelair Creek; 50 ARe 50, 50 ACh 43F, 44F, 51F, Imnaitchiak Creek; 49 AMg 116F, 49 ALac 118F, Killik River]

Field sample (USGS Mesozoic locality)

AMg(21829)4929F AMg88F(21831)49 AMg116F(24503)49 ALacllSF49(24504) ADt23F(21832)49 ARe(23181)50173 ACh32F(23182)50 ACh(23183)37F50 ACh43F(23184)50 (23185)ACh44F50 ACh51F(23186)50 ACh82F(23187)50 Fossil AE(23174)750 AE(23175)5053 AE(23176)5056 AE5082(23177) ARe(23178)5035 (23179)ARe5036 ARe(23180)50

Spiriferina yukonenris X Smith. Terebratulid brachiopod X indet. Daonetta cf. L. dubia Gabb. X cf.D. moussoni Merian. X Dimyodonf sp...... X X Entomonotis subdrcularis X Oabb. Pseudomonotis subdrcularis X X X X X X X Gabb. aff. E. subdrcularis Gabb ...... X Halobia cf. H. cordillerana Smith...... X X X X ornatissima Smith...-, X cf. H. superba Mojsi- sovics...... X X Macroden"? sp ...... X Myophona"? sp ...... X X X Posidonia? stella Gabb ..... X X X Fish bone indet.-...... X THE KELLIK-ETTVLTJK RIVERS REGION 351

Tiglukpuk formation rocks were not mapped separately purplish blue that suggests manganese staining. No because the similarity of lithology between them and mega- or microfossils were found in these rocks. the Shublik, Okpikruak, and Fortress Mountain for­ Although no fossils were found, the large hill about 1.5 mations, and the complexity of the folds and faults miles southwest of camp C-June 16-50 on Imnaitchiak made identification uncertain. In the complex areas Creek is interpreted as being formed by the Tiglukpuk where isolated small outcrops of Tiglukpuk formation formation. A section, composed of a 15-foot conglomer­ have been identified or where some rocks of this for­ ate unit overlain by an estimated 530 feet of sandstone mation are reasonably inferred to be present, the Juras­ and conglomeratic sandstone with both top and bottom sic is included in five undifferentiated mapped units covered, is present in this hill. (pi. 43). The 1,040-foot section that is exposed along the creek The more resistant units of the Tiglukpuk formation, between Cascade and Kurupa Lakes (pi. 45, section 2) in part, help to form large elongate whaleback ridges may be wholly or in part Tiglukpuk formation. As in the Imnaitchiak Creek-Kurupa Rivers area. The exposed, 520 feet of chert overlies the clastic sequence, less resistant shale units weather readily and form poor but field observations indicate that this entire section is outcrops and low rubble-covered slopes. overturned and thus the chert is older and could be part Character and thickness. The Tiglukpuk exposures of the Shublik formation. No fossils were found in this mapped on plate 43 consist of: olive-green and greenish- section. gray graywacke-type sandstone of varying grain size; An exposure of possible Tiglukpuk .formation was granule-pebble-cobble conglomerate and conglomeratic examined on Puvakrat Ridge about a mile west of Camp sandstone; siltstone; silty shale; medium-gray to M-June 14-49 on the Etivluk River. It is mapped as greenish-gray clay shale; light- to medium-gray Buchia Tiglukpuk, Okpikruak, and Fortress Mountain forma­ (Aucella) concentrica limestone coquina; and gray, tions undifferentiated. The rock is a graywacke sand­ greenish-gray, and bluish-gray chert. Shell detritus stone and conglomerate and may be 500 to 700 feet and cream-colored dull porcelaneous chert grains are thick. The conglomerate is crossbedded, poorly ce­ common in the sandstone. The sandstone and conglom­ mented, and in part covered by a weathered mantle of erate occur in massive beds 10 feet thick or more, and pebbles and boulders on the ridge top and in the some form resistant rubble-covered ridges with poor gullies. The pebbles and boulders range from % inch to outcrops. The pebbles and cobbles in the conglomerate 28 inches in diameter and consist of mafic igneous rocks, include chiefly light- to medium-gray chert, milky and limestone of the Lisburne group, limestone and chert glassy quartz, and black chert, with minor amounts of from the Shublik formation, and colored chert, gray­ unusually well rounded granite, basalt-gabbro, Monotis wacke, and shale. Much of the formation is gray green sp.-bearing light-gray limestone, greenish-gray Juras­ and weathers rusty red brown. sic (?) sandstone (locally common), green chert, light- No reliable thickness estimates can be given for the tan-gray mudstone, limestone from the Lisburne group Tiglukpuk formation in this region. Contacts with the with coral fragments, and altered mafic igneous rocks. under- and overlying formations were not seen, and In general the largest cobbles are 6 inches in diameter, nowhere was more than a partial section observed. It but the average is 2 to 3 inches, and some boulders 3 is likely that the thickness varies considerably, and in feet in diameter were found. Most of the constituents parts of the Killik-Etivluk Rivers region the formation are rounded to well rounded, and angular pebbles are may be absent. It is postulated that the Tiglukpuk is not common. The clastic rocks weather yellow red to 1,500 feet thick in the Killik-Oolamnagavik Rivers area. dark red brown. A limestone coquina, containing Age and correlation. The megafauna collections from abundant fragmentary shell remains that could not be the Tiglukpuk formation in the mapped region are positively identified but that may be Buchia (Aucella) from the few exposures of a reddish-brown weathered concentrica, of Jurassic age, was found in two isolated limestone coquina. The preservation of the shells is outcrops, one a mile and the other 2 miles north of camp so poor that none could be positively identified. Ac­ C-June 16-50 on Imnaitchiak Creek. cording to J. B. Reeside, Jr., and R. W. Imlay (written A small exposure of 75 to 100 feet of fissile paper-thin communication, 1950) "the common form is guessed soft noncalcareous clay or silty shale in beds 1 to 3 feet to be Posidonia stella Gabb." They suggested that thick that includes concretions and fragments of steel- this coquina may represent the Buchia (Aucetta) blue to gray siltstone and very fine grained sandstone concentrica zone that has been described by Patton and that probably is Tiglukpuk formation, lies about (1956a). Lithologically the coquina is similar to that 1.25 miles west of Camp C-June 22-50. The shale included in the Tiglukpuk formation by Patton (1956a). varies from dark yellowish red to greenish yellow and Thirteen microfossil samples were collected from beds dark gray, and in part is weathered to steel blue and of the Tiglukpuk formation and Tiglukpuk and Okpi- 352 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 kruak formations undifferentiated. One sample, 50 the Okpikruak forms long high rubble-covered whale- ARe 173, from 2.25 miles northwest of camp E-July back ridges that have 500 to 1,000 feet of relief. 8-50, on the Kurupa River, contained the character­ Character and thickness. The Okpikruak formation istic Jurassic microfossils Bathysiphon anomelocoelia in the large syncline south of Lake Betty and between Tappan, Haplophragmoides topagorukensis Tappan, Kutchaurak Creek and the Etivluk River is composed Glomospirella sp., and Gaudryina kelleri Tappan. The of a sequence of alternating graywacke sandstone, other samples were either barren or contained long- pebble conglomerate, siltstone, and shale. The sand­ ranging nondiagnostic Foraminifera (H. R. Bergquist, stone and conglomerate is dark olive green and weathers written communication). dark red brown. The pebbles in the conglomerate are The Tiglukpuk formation insofar as known in this subangular to subrounded and are mostly black, gray, region is similar to that in the region east of the Killik yellow, and white chert, with some siltstone and sand­ River described by Patton (1956a), and it is exposed in stone pebbles. In places Buchia (Aucella) crassicolis the same geologic and geographic belt. There is no Keyserling is abundant, and in other beds only shell apparent correlation in thickness, overall lithology, or fragments occur with interbedded black clay shale fauna between the Tiglukpuk formation in this region, containing limy concretions % to 2 inches in diameter. and in Topagoruk test well 1 (Collins, 1958). The Some half- to 5-inch well-rounded chunks of leathery Jurassic section in this well is about 2,000 feet thick, black oil shale were found as float in some of the gray­ and a section thickness of 1,450 to 1,800 feet has been wacke sandstone and conglomerate rubble along one of measured (Patton, 1956a) in outcrops in the region the ridges on the west side of the Etivluk River several 50 to 75 miles east of the Killik River. Thus, little miles west of camp M-June 6-19. The oil shale change in thickness but significant changes in lithology appeared to be pebbles and cobbles derived from the and fauna in a northward direction are indicated. conglomerate by residual weathering. CRETACEOUS SYSTEM In the vicinity of Kurupa River the Okpikruak The Lower Cretaceous rocks in the Killik-Etivluk formation is: medium-bedded medium- to fine-grained Rivers region are represented by the Okpikruak, Torok, micaceous greenish-gray graywacke-type sandstone, with and Fortress Mountain formations and by part of the some calcareous beds, ironstone concretions, and a few Nanushuk group. The rocks are chiefly shale, sand­ carbonaceous plant remains, worm trails, and well- stone, siltstone, and conglomerate, and in aggregate developed flow casts in the sandy beds; and medium- have a section thickness of many thousand feet. bedded dark gray-green, graywacke-type grit and pebble Topographically prominent ridges and lowlands are conglomerate. The pebbles are bluish-gray, black, formed by these formations. green, and yellow chert, subangular to subround, and OKPIKRUAK FORMATION % to % inch in diameter. Some shell fragments occur Occurrence. The type locality of the Okpikruak for­ in the conglomerate. Exposures of the formation in mation is about 12 miles east of the Killik River on a this area show a patterned repetition of these lithologic small tributary of the Okpikruak River at approximately types that suggests cyclical deposition. lat 68°34'30" N. and long 153°39' W. (Gryc, Patton, The contact between the Okpikruak formation and and Payne, 1951, p. 159-160). The Okpikruak forma­ the underlying rocks was not seen in this region, and tion in the Killik-Etivluk Rivers region crops out in the it can only be assumed that the Okpikruak overlies southern half of the southern foothills section, and in Jurassic rocks with little or no angular discordance. general is poorly exposed. The outcrops form three At some localities in northern Alaska, the Okpikruak roughly defined and discontinuous west-trending belts. overlies the Jurassic Tiglukpuk formation with angular The southernmost belt includes a series of isolated discordance (Patton, 1956a, p. 218). synclines adjacent to the north front of the Brooks The thickness of the Okpikruak formation in the Range and between the Kurupa River andTukuto Killik-Etivluk Rivers region is estimated, on the basis Creek. The middle belt, which is 4 to 8 miles in width, of meager evidence, to be approximately 1,700 feet. lies approximately between lat 68°30' N. and 68°35' At the type locality the formation is about 2,400 feet N., and includes a structurally complex zone in which thick (Gryc, Patton, and Payne, 1951, p. 159). these rocks, for, the most part, are mapped as the Age and correlation. The Okpikruak formation in Shublik, Tiglukpuk and Okpikruak formations, undif­ the mapped region was correlated with the Okpikruak ferentiated. The northernmost belt in which the in other regions in northern Alaska on the basis of Okpikruak occurs lies approximately between lat 68°34' lithologic similarity and a few fossil collections. Mega- N., and 68°41' N., and within this belt the rocks have fossils are not common in the Okpikruak formation in been mapped as Tiglukpuk, Okpikruak and Fortress the Killik-Etivluk Rivers region, and Buchia (Aucella) Mountain formations undifferentiated. In general, crassicolis Keyserling and a questionable B. (Aacetta) THE KILLIK-ETIVLUK RIVERS REGION 353 crassa Pavlow were identified by Reeside and Imlay pebble-cobble conglomerate; thick units of clay shale from the few collections made. A meager microfauna and siltstone are interbedded with the sandstone and was obtained from a few samples collected for this conglomerate. The overall ratio of these coarse purpose (pi. 45). elastics to shale is about 60 to 40 percent. FORTRESS MOUNTAIN FORMATION The formation as exposed in the Killik-Etivluk Occurrence. The type section of Fortress Mountain Rivers region is not exactly the same as that described formation is a composite of sections exposed along the from the type locality (Patton, 1956b); however, gross Kiruktagiak River and on Castle Mountain, approxi­ lithologic features are the same, and the rocks can be mately 30 miles east of the Killik River at lat 68°34/ N. correlated with the Fortress Mountain formation. The name is taken from Fortress Mountain, which is The stratigraphic sections (pi. 46) are divided into three about 6 miles west of the type section localities (Patton, units for the purpose of correlation: upper shale and 1956b, p. 219). The Fortress Mountain formation siltstone, about 1,870 feet thick; conglomerate and crops out in the mapped region only in a narrow west- sandstone, about 1,300 to 1,680 feet thick; and lower trending belt between lat 68°40' N. and 68°45' N., in shale and siltstone unit about 2,800 feet thick. These the northern half of the southern foothills section. three units are not a formal breakdown of the formation This belt is characterized by low rounded mountains to be used in mapping, but are shown on plate 46 and ridges formed by coarse clastic rocks. Smith merely as an aid in correlating the incomplete sections Mountain (fig. 61) lies at the western end and Pingalu- exposed in the mapped region. These units are not ligit Mountain at the eastern end of this area, which is differentiated on the geologic map (pi. 43). a part of the major west-trending zone of Fortress The sandstone is generally fine to coarse grained, Mountain rocks that extends across the greater part of with many angular fragments of chert, medium bedded northern Alaska; the ridges and peaks in this belt are to massive, dark gray to green, crossbedded, and com­ in general the highest topographic features north of the monly calcareous. The conglomerate occurs in massive Brooks Range, crossbedded units as much as 50 feet thick, as well as A zone of low rounded hills mapped as Fortress in thin lenticular podlike beds in the sandstone. The Mountain and Torok formations undifferentiated lies massive beds are characteristic of the upper part of the immediately north of the topographically prominent formation. Subordinate amounts of plant debris are Fortress Mountain belt, and gives way northward to a found in the coarse clastic sequence. The dominant featureless lowland area underlain by the Torok forma­ conglomerate constituents are colored chert, with tion. There are relatively few outcrops in the area of minor amounts of white quartz, limestone, and mafic low hills, and the geology consequently is poorly known. igneous rocks, and are generally angular to subround. Just south of the area of Fortress Mountain formation The size of the constituents ranges from about 0.5 is another west-trending zone of rocks that are mapped inch to as much as 24 inches, but the average size is as Fortress Mountain, Okpikruak and Tiglukpuk for­ about 1 inch to 7 inches. Although well sorted by mations undifferentiated. In general, this belt of size within individual beds, the fragments are larger undifferentiated rocks which ranges from 1 to 8 miles in the upper part of the formation. Limestone and in width, is characterized by few and poor outcrops and mafic igneous rock fragments are generally restricted by low rounded topography similar to that underlain to the upper part of the conglomerate and sandstone unit. by the Torok formation. Within this area a few higher The shale is generally dark gray to black, fissile, ridges near Outwash, Nogak, and Iteriak Creeks are soft, and commonly calcareous; it is dominantly clay differentiated as Fortress Mountain formation. shale, but silty shale and beds of siltstone are present. A considerable part of the area included in the above- Locally the shale is well indurated and may have a mentioned three zones is covered by tundra, terrace hackly fracture; this is largely influenced by local gravel deposits, and valley-fill alluvium. The ridges deformation. Mudflow marks and swirl-bedding fea­ and outcrops are discontinuous, the lithology of the tures are common in siltstone and sandstone that is Fortress Mountain, Okpikruak, and Torok formations interbedded with the shale; these sandstone beds may is in part similar, faunal remains are rare in all three also show graded bedding. Ironstone and marcasite formations, and apparently the structure is complex; concretions are minor constituents of the shale sections. therefore, it was not possible to delimit accurately, The Fortress Mountain formation identified in the or in detail, the extent of the Fortress Mountain Killik-Etivluk Rivers region is apparently somewhat formation. thinner than the 10,000-foot section that is exposed at Character and thickness. The Fortress Mountain the type locality (Patton, 1956b). A complete section formation is composed dominantly of thick units of of the formation was not found in the mapped area, dirty graywacke-type gray to green sandstone and but a composite of the measured sections indicates that 679606 O 63 5 354 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 THE KILLIK-ETIVLUK RIVERS REGION 355 about 6,000 feet of the formation is present. A section Fortress Mountain formation Continued Feet about 5,920 feet thick was computed from outcrops Lower shale and siltstone Continued I. Sandstone, etc. Continued along the west bank of the East Fork of the Etivluk shale and siltstone. Shale dark gray green, River near camp E-July 25-50. An unconformity was moderately indurated. Unit mostly rubble mapped at the base of a conglomeratic unit; it is be­ covered; computed thickness approxi­ lieved that this unconformity is a local feature and that mately______1,000 it does not greatly alter the thickness of the formation. TotaL--______.______2, 680 Columnar sections of the Fortress Mountain for­ Columnar section 2 from the East Fork of the mation are shown on plate 46. The sections were Etivluk River was measured in a series of more or less measured in a number of discontinuous cutbank ex­ continuous cutbanks along the west side of the river posures along the major north-flowing streams, on near camp E-July 25-50. The section is in south- Smith Mountain, and on the high ridges of Pingaluligit dipping strata; the dip increases toward the north from Mountain, between the Killik and Oolamnagavik 18° S. to 70° S. A local unconformity or possible Rivers. The sections are arranged in order from west fault is present at the base of the conglomeratic section. to east. Where the field data are not complete enough This section contains the most completely exposed to warrant detailed sections, generalized sections were sequence of known Fortress Mountain formation in compiled. the mapped region. The Smith Mountain section (pi. 46, column 1) Section of Fortress Mountain formation on the East Fork of the was measured during a traverse up the east side of the Etivluk River peak 5 miles N. 35° W. from camp M-June 17-49. Fortress Mountain formation (section incomplete): The side of the peak is rubble covered and only the Upper shale and siltstone unit: more resistant sandstone and conglomerate beds are 12. Clay shale, dark-gray to black, fissile, soft; Feet in beds 2 to 3 in. thick; nodular-weathered. well exposed as ledges; the section is generalized, but Interbedded siltstone, silty shale, and is of value because it is typical of the coarse clastic sandstone; sandstone gray green, thin part of the formation in the western part of the mapped bedded (% to 4 in.), very fine to fine region. The total thickness may be in error by 10 to grained, calcareous; contains mud-ball con­ 15 percent. cretions locally and constitutes about 5 percent of the unit. In part rubble covered; Generalized section of Fortress Mountain formation on Smith computed thickness approximately. _ _ _ 1, 870 Mountain Conglomerate and sandstone unit: Fortress Mountain formation (section incomplete): II. Sandstone and clay shale with inter bedded Conglomerate and sandstone unit: Feet siltstone and silty shale; sandstone, in 4. Conglomerate, conglomeratic sandstone, sand­ beds as much as 3 ft thick, dark greenish stone, siltstone, and shale. Conglomerate gray to light olive gray, very fine to fine and conglomeratic sandstone medium bed­ grained, calcareous. Flow casts present ded to massive; pebbles and cobbles (J4 to on under side of beds; worm trails, fucoidal 7 in. in length) dominantly colored chert marks. Forty percent of unit is sand­ with few limestone and mafic igneous peb­ stone, 35 percent siltstone and silty shale, bles; abundantly crossbedded, poorly ce­ 25 percent clay shale. In part rubble cov­ mented green sandstone matrix. Sand­ ered ; computed thickness approximately _ _ 420 stone thin to medium bedded, fine to 10. Sandstone, pebble-cobble conglomeratic; medium grained, dark green. Siltstone dominantly cobbles at base and pebbles at and shale constitute about 20 percent of top; pebbles subround to round. Consists unit. In part rubble covered; computed of colored chert, few limestone and plu- thickness approximately______640 tonic igneous cobbles near base; beds 5 to 3. Sandstone and shale. Sandstone thin to 10 ft thick, with light-green poorly ce­ medium bedded, medium grained, dark mented sandstone matrix; interbedded green; contains angular rock fragments; sandstone of same type, in beds 3 to 8 ft poorly sorted. ______210 thick; some siltstone and shale.______320 2. Similar to unit 4; conglomeratic constituents 9. Covered; computed thickness approximately. 100 dominantly of grit to pebble size; no lime­ 8. Sandstone and silty shale. Sandstone, mas­ stone or igneous rock fragments; mostly sive, medium-grained, light-green; com­ rubble covered; computed thickness ap­ posed of chert debris. Shale dark green, proximately. ______830 friable.______------60 Lower shale and siltstone unit: 7. Conglomerate and sandstone. Conglom­ 1. Sandstone, siltstone, and shale; sandstone erate in massive beds (20 to 30 ft thick), thin to medium bedded, fine to medium composed of colored chert, dominantly grained; dark-greenish brown; few angular gray and green, few plutonic rock types; chert pebbles and shale inclusions. Unit well rounded. Sandstone fine grained, about 40 percent sandstone, 60 percent light-green. ______-___--_---_-_ 106 356 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Fortress Mountain formation Continued Fortress Mountain formation Continued Conglomerate and sandstone unit Continued Feet Conglomerate and sandstone unit Continued feet 6. Sandstone and clay shale______100 7. Clay shale and graywacke sandstone inter­ 5. Conglomerate; cobbles at base, pebbles at bedded with siltstone; shale more abund­ top; consists dominantly of light and dark ant in upper part and graywacke in lower gray, black, green, and red chert; few part. In part rubble covered; computed limestone and quartz cobbles; local fer­ thickness approximately______670 ruginous bands______---_-______160 6. Covered; computed thickness approximately. 350 4. Sandstone, massive, fine-grained, ferru­ 5. Graywacke sandstone thin- to medium- ginous. ______-___-__-----_--___ 5 bedded, fine- to medium-grained; light- 3. Conglomerate, similar to unit 5; contains greenish-yellow; thin interbedded clay local lenses of sandstone.______25 shale and siltstone______20 2. Sandstone with few chert pebbles, coal 4. Clay shale and siltstone float in covered in­ fragments.______4 terval; computed thickness approximately__ 450 Local uncomformity. 3. Clay shale and siltstone.______140 Lower shale and siltstone unit: 2. Clay shale and siltstone float in covered 1. Clay shale, black, fissile, soft, with inter- interval; computed thickness approxi­ bedded sandstone; light gray, thin bedded mately ______510 to massive, fine grained; chert and quartz 1. Clay shale and siltstone in beds 4 to 12 in. grains in silty matrix; unit about 80 per­ thick...----....------.------.----- 125 cent shale and 20 percent sandstone____. 2, 760 Total______3, 050 Total____._____..______5, 930 The Heather Creek section (pi. 46, column 4) was Tfre Kurupa River section (pi. 46 column 3) was measured in a series of discontinuous outcrops on the measured on the east bank of a small tributary of the east bank of the creek between the anticlinal axis and Kurupa River S. 45° E. from camp C-July 16-46. the thrust fault at lat 68°40' N. to 68°41' N.; the strata The column consists of strata that have been correlated dip 30° to 60° S. The exposed beds were measured and with the conglomerate and sandstone unit and the the stratigraphic thickness of the covered parts was lower shale and siltstone unit. computed; this may be in error by 15 percent. Section of Fortress Mountain formation on tributary of the Kurupa Section of Fortress Mountain formation on Heather Creek River Fortress Mountain formation (section incomplete): Fortress Mountain formation (section incomplete): Upper shale and siltstone unit: Feet Conglomerate and sandstone unit: peet 15. Clay shale, medium-dark-gray, fissile, soft 16. Graywacke conglomerate, black chert noncalcareous; in beds 1 to 12 in. thick; pebbles, and fine-grained graywacke_ ... 15 interbedded with clay shale are silty shale, 15. Graywacke sandstone, greenish-yellow, and siltstone, and graywacke, all light yellow, few black chert pebbles; very fine to fine poorly indurated, micaceous, carbonaceous, grained; interbedded shale and siltstone in beds 1 to 5 in. thick; some pyrite and in beds 6 to 10 in. thick. Unit mostly chalcopyrite vemlets ______------___-- 100 rubble covered, computed thickness ap­ Conglomerate and sandstone unit: proximately. ______130 14. Covered; computed thickness approximately. 825 14. Graywacke sandstone, pale-greenish-yellow, 13. Graywacke, conglomeratic, beds 3- to 8-in. thin-bedded, very fine to fine grained____ 15 thick; fine to coarse grained; dull-greenish- 13. Interbedded graywacke sandstone, siltstone, yellow; granule-pebble conglomerate, and shale; rubble; computed thickness dominantly subround black chert approximately______65 granules______------_-- 40 12. Conglomerate, pebble-granule; dominantly 12. Covered; computed thickness approximately- 250 black chert. Irregularly bedded gray­ 11. Sandstone, thin-bedded (4 to 5 in.), light- wacke sandstone with some crossbedding; yellow-green, fine to very fine grained; con­ fine-grained, well-cemented; few clay tains a few chert pebbles and granules; pellets and plant fragments.______25 carbonaceous; some interbedded calcar­ Lower shale and siltstone unit: eous siltstone. Unit partly rubble cov­ 11. Sandstone, greenish-yellow, fine-grained, and ered; computed thickness approximately._ 220 shale; rubble; computed thickness approxi­ Lower shale and siltstone unit: mately______170 10. Covered; computed thickness approximately. 250 10. Clay shale with interbedded siltstone and 9. Siltstone, highly weathered.______10 very fine grained graywacke sandstone; 8. Covered; computed thick ness approximately. 310 one 8-ft bed of fine-grained light-greenish- 7. Silty shale; weathers rust brown ______45 yellow graywacke near center of unit_ _ _ _ 225 6. Covered; computed thickness approximately. 250 9. Covered; computed thickness approximately. 110 5. Graywacke, thin-bedded, medium-grained; 8. Clay shale and siltstone with 4-ft medium- light-greenish-yellow; some interbedded gray thin-bedded medium-grained gray­ clay shale.______20 wacke______30 4. Covered; computed thickness approximately- 780 THE KILLIK-ETIVLUK RIVERS REGION 357 Fortress Mountain formation Continued Alaska were sampled more extensively for microfossils Lower shale and siltstone unit Continued feet than were the sections from the mapped region; the 3. Graywacke, thin-bedded, very fine grained; microfauna from the other sections indicate that medium-gray; interbedded siltstone and clay shale; undulatory bedding; nodular although some of the species are long ranging there are weathering- ______30 also some species restricted to the Fortress Mountain 2. Covered; computed thickness approxi­ and Torok formations. Gaudryina tailleuri, which mately.- _---__-____-____-_---_____--_ 175 is found in the lower part of the Torok formation as 1. Siltstone, sandy, greenish-gray, andsilty shale. 20 as well as in the Fortress Mountain, is particularly Total..______3,325 diagnostic and directly supports the correlation based The columnar section from the East Fork of the on the ammonites Colvillia and Beudanticeras. The Oolamnagavik River (pi. 46, column 5) was computed Fortress Mountain formation appears structurally to from rubble traces and outcrops on Pingaluligit Moun­ be in part equivalent to the Torok formation and tain 3 to 5 miles north of camp C-May 29-50. These perhaps in part to the Tuktu formation of the Nanushuk prominent ridges are part of a complexly folded syn­ group. clinal structure and the rocks are from high in the TOBOK FORMATION Fortress Mountain sequence. Occurrence. The Torok formation is exposed in a northwest-trending belt in the northern part of the Generalized section of Fortress Mountain formation on Pingaluligit southern foothills section of the Arctic foothills Mountain province. This belt is characterized by low, gently Fortress Mountain formation (section incomplete): feet Conglomerate and sandstone unit: Dominantly gray- rolling topography with isolated ridges of sandstone wacke sandstone with subordinate interbedded and conglomerate rising above the lowlands underlain conglomerate, conglomeratic graywacke, silty shale, by shale; it is from 4 to 16 miles wide in the Killik- and siltstone. Graywacke light greenish yellow, thin- Etivluk Rivers region. The Tuktu escarpment rises bedded (1 to 3 in.), fine grained; subangular black abruptly from the lowland and generally forms the chert granules and pebbles. Conglomerate pebble- cobble (80 percent pebbles), 85 percent black northern limit of exposures of the Torok formation, chert, 10 percent colored chert, 5 percent gray­ which is at lat 68°48' N., along the Killik River; in the wacke. Siltstone and shale swirl-bedded with Etivluk River area it is at lat 68°59' N. High ridges ropey mudflow marks and mud cracks. Unit and mountains formed by the coarse elastics of the mostly rubble; computed thickness approximately. 1, OOP Fortress Mountain formation lie south of the lowlands; .Total______.____ 1,000 between the ridges of definite Fortress Mountain and Age and correlation. No megafossils were obtained the lowland of Torok is an area, 1 to 4 miles wide, of from strata of the Fortress Mountain formation in the undifferentiated Torok and Fortress Mountain forma­ mapped region. The formation is locally fossiliferous tions. The zone of undifferentiated strata has topo­ in other parts of northern Alaska, and the age of the graphic and lithologic features common to both forma­ beds as determined by those megafossils is early Albian tions, but the rocks in the discontinuous outcrops (late Early Cretaceous). Tmlay (1961, p. 58) identified cannot be correlated definitely with either formation. and described the fossils. The diagnostic species in­ Discontinuous outcrops of the formation are exposed clude the ammonites Colvillia crassicostata Imlay, C. along all the major north-flowing streams in the mapped kenti Imlay, Beudanticeras (Grantziceras) aff. (Whit- area and on many of the smaller streams. The outcrops eaves), and the pelecypods Aucellina dowlingi Mc- are generally confined to the stream banks that are Learn, Thracia kissoumi McLearn; Pleuromya kelleri being actively eroded; the soft, incompetent shale does Imlay, Placunopsis nuka Imlay, and Inoceramus cf. not form good outcrops hi the interstream areas. The /. altifluminus McLearn. Part of the Fortress Moun­ outcrops are commonly overlain by terrace gravel tain formation is correlated with the lower part of the that slumps down onto the bedrock and further compli­ Torok formation by means of the ammonites Colvillia cates the measuring of a continuous stratigraphic and Beudanticeras, which are found in both formations. sequence. The coarser beds of the formation can be A considerable part of the Fortress Mountain forma­ traced into the interstream areas where they form low tion is shale: however, only 72 microfossil samples were rubble-covered ridges. collected and 46 of these were barren. The few fossils The Torok formation is best exposed along the west from these samples are shown in table 5; they were bank of the Etivluk River and the east bank of Kucher .identified by Bergquist (written communication), who Creek. The strata there are commonly folded into reported: "* * * the fossils have little value for identi­ small, steeply plunging anticlines and synclines on the fying the sections from which they came as most are flanks of larger structures. The beds may be offset by long ranging and nondiagnostic". Some sections of small, high-angle faults, and drag folds are common; Fortress Mountain formation in other parts of northern the beds dip steeply, generally about 25° to 50°. 358 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

A section of Torok formation about 45 feet thick is equivalent to 3,200 feet was computed by assuming exposed in the center of the Kurupa anticline on the that the strike and dip remain constant across the Kurupa River; this was not mapped on plate 43 because covered interval. Below the covered interval is 425 the outcrop is too small to show at the mapping scale. feet of calcareous siltstone, silty shale, and sandstone; Character and thickness. A calcareous dark-gray to thus, a computed thickness of 6, 725 feet of Torok black clay shale is the dominant rock type of the Torok formation lies between the Tuktu formation contact formation in the mapped region. Siltstone and silty and the axis of the first anticline south of the contact. shale in units 3 to 12 inches thick are commonly inter- Three incomplete sections (A, B, and C) of the Torok bedded with the clay shale; the clay shale varies from formation were measured from exposures on the west soft and crumbly to well-indurated and hackly frac­ bank of the Etivluk River; they cannot be correlated tured, depending mainly on the amount of local de­ with each other nor with the Kucher Creek section. formation. Marcasite concretions, as much as 6 inches This fact may indicate that the Etivluk sections are in diameter, are a common feature of the clay shale additional lithologic units or merely that they represent sections. Pyrite is found in the shale as crystals, but a facies change. Section C is about 90 percent gray­ it rarely occurs as concretions. wacke sandstone, with some black chert pebbles which The silts tone is generally thin bedded and may be is similar to the graywacke sandstone section at the laminated, dark gray with a greenish tinge to light gray, type locality (Detterman, Bickel, Gryc, 1963, p. 235). and calcareous. Many of the siltstone beds show mud- The Torok formation in the Killik-Etivluk Rivers flow marks and swirl-bedding features that could have region is probably on the order of 7,000 to 10,000 feet been formed by turbidity currents. Ironstone and thick. The upper contact with the Tuktu formation is marcasite concretions are present in the siltstone, as gradational, and some beds that are mapped as Tuktu well as mud-ball concretions; plant fragments and formation in the Chandler River region may be mapped megafossils are common locally in relatively narrow as Torok in the Killik-Etivluk Rivers region. In zones within the formation. general, the beds are more complexly folded and more Graywacke sandstone and conglomeratic sandstone steeply dipping in the Torok formation than in the are important, although subordinate constituents of Tuktu formation, but there is no conclusive evidence the formation; they probably form about 30 percent of of an unconformity between the two formations in the the exposed rocks. The sandstone is generally shaly mapped region. to thin bedded, very fine to fine grained, dark gray to Sections of the Torok formation were measured along green, and predominantly calcareous. In most out­ the Etivluk River and Kucher Creek. They cannot crops the sandstone is in beds % to 3 inches thick be definitely correlated, and probably do not represent and is associated with siltstone; column 1 C (pi. 47) the complete Torok sequence in the Killik-Etivluk on the lower Etivluk River is an exception, about 90 Rivers region. The sections from the lower Etivluk percent of the exposed rock is graywacke sandstone. River are shown (pi. 47) in order from south to north; The conglomeratic constituents are mostly well-rounded the details within each column are in stratigraphic black chert pebbles % to 3 inches in diameter. A few succession, but the overall stratigraphic relationship intraformational shale and siltstone pebbles are present between the columns is not known. also. The formation was insufficiently exposed elsewhere A few thin lenticular beds of bony coal and calcareous to measure sections. siltstone concretions in the Kucher Creek section consti­ Sections of Torok formation on the lower Etivluk River tute the only other rock types in the Torok formation. Section A (incomplete), 1 mile upstream from junction The exposed sections of the Torok formation can be with East Fork: Feet correlated only on gross lithologic features; conse­ 8. Silty shale, medium-gray; medium-green highly quently, it is impossible to determine the total thickness argillaceous siltstone; medium-green, very fine of rocks present. The section at Kucher Creek is the to fine-grained friable sandstone in 1- to 6-in. beds. 80 most nearly complete; it is on the north flank of an 7. Clay shale, dark-gray, thin-bedded, with some interbedded silty shale ______---_------120 anticline and the upper 3,100 feet, including the grada- 6. Sandstone, thin-bedded, fine- to medium-grained, tional contact with the Tuktu formation is exposed. medium-green, highly argillaceous, slightly cal­ The section as exposed is clay shale, silty shale, silt- careous, with a few black chert pebbles }£ to 3 stone, and sandstone; it has considerably more sand­ in. in diameter; abundant wood fragments along stone, siltstone, and silty shale than does the type bedding planes; few mud-ball concretions---.- 60 5. Siltstone, silty shale, and sandstone ______15 section of the Torok formation from the Chandler 4. Sandstone, thin-bedded, medium-green, very fine River about 32 miles east of the Killik River (Detter- grained.______--_--_------20 man,Bickel, and Gryc, 1963, p. 235). A covered interval 3. Silty shale with interbedded siltstone ______40 THE KILLIK-ETIVLUK RIVERS REGION 359

Section A Continued Feet Torok formation Continued 2. Sandstone, shaly to thin-bedded, medium-green, 17. Silty shale, dark-gray, slightly calcareous, nod- Feet very fine grained, highly argillaceous______15 ular, fractured; some interbedded calcareous 1. Clay shale, dark-gray, with some inter bedded thin-bedded sandstone and siltstone ______370 silty shale-.------.------____------230 16. Covered; computed thickness approximately____ 85 Total______580 15. Silty shale with some interbedded sandstone % to 2 in. thick____-_-_____-__.____-_.____ 210 Section B (incomplete), \% miles north of section A: 14. Covered; computed thickness approximately.-.. 160 5. Clay shale, dark-gray.______200 13. Siltstone with subordinate silty shale and sand­ 4. Clay shale with interbedded silty shale, siltstone, stone; sandstone thin-bedded (% in.), dark- and sandstone; shale in beds 1 to 6 in. thick; gray, very fine grained, calcareous______110 siltstone and sandstone beds 1 to 3 in. thick; 12. Silty clay shale, siltstone, and subordinate very sandstone, medium to light gray, very fine to fine grained yellow-brown sandstone; few fine grained; marcasite concretions as much as lenticular beds of bony coal as much as 4 in. 6 in. in diameter associated with siltstone beds. thick. ______240 Fossils from the unit include the ammonites 11. Covered; computed thickness approximately__ 250 Cleoniceras tailleuri Imlay and Puzosiat sp. and 10. Siltstone, dirty, calcareous, with subordinate the pelecypod Inoceramus sp_____.______200 calcareous sandstone; abundant plant fragments- 30 3. Clay shale, silty shale, and siltstone; dominantly 9. Covered; computed thickness approximately____ 30 clays hale; marcasite concretions in siltstone beds; Siltstone and silty shale; unit grayish black, rubble; computed thickness approximately. _ _ _ _ 420 weathered to dark gray, friable. Local sand­ 2. Sandstone, thin-bedded, very fine to medium- stone units 5 to 6 ft thick, thin bedded, very grained, medium-gray to green, graywacke- fine grained, light olive gray, weathered to type; some interbedded shale and siltstone; moderate yellow brown. Few small ironstone megafossils include the ammonite Subarcthop- concretions. Sandstone more abundant in lites bickeli Imlay and pelecypod Inoceramus upper part. Fossil fragment from middle of unit- 180 cf. /. anglicus Woods ______80 7. Siltstone, silty shale, and sandstone; rubble; 1. Clay shale; units 10 in. thick interbedded with computed thickness approximately ______140 siltstone units 4 to 6 in. thick; a few thin beds Covered; computed thickness approximately.--. 595 of sandstone and silty shale______180 5. Siltstone with subordinate amount of interbedded Total.-.-.-____-_-_--____.__._ 1,080 sandstone % to 2% in. thick; very fine to fine Section C (incomplete), 3 miles north of section B: grained; mudflow marks common. ______420 8. Clay shale, dark-gray, with a few thin layers of 4. Covered, computed thickness approximately. _ _ _ 3, 200 siltstone and silty shale interbedded; rubble; 3. Siltstone with some interbedded silty shale. ____ 65 computed thickness approximately ______70 2. Sandstone, thin-bedded (2 to 3 in.) very fine to 7. Sandstone, graywacke-type, thin-bedded (2 in. to fine-grained; medium-dark-gray, weathers to 1 ft), laminated; swirl bedding common; very dark yellow brown.______20 fine grained, medium-yellow-red, with some 1. Silty shale, calcareous, with interbedded dark- interbedded siltstone and shale______425 gray calcareous siltstone; concretions of cal­ 6. Covered; computed thickness approximately..... 120 careous siltstone ______-__--__----,_-_ 340 5. Sandstone with silty shale interbedded; similar to unit 7______...______25 Total._____-.____-__-____ 6, 715 4. Covered; computed thickness approximately_-___ 390 3. Sandstone, with few black chert pebbles______- 8 Age and correlation. The age of the Torok formation 2. Sandstone, thin-bedded, fine- to medium-grained, has been determined from megafossils as early to middle dark-green ______77 Albian. The fossils were identified by Imlay (1961, 1. Clay shale; rubble; computed thickness approxi­ p. 31). He divided the Torok formation into three mately_---_--_-______.____20 parts: a lower part that is correlated with the lower part Total__..____...... ______1, 135 of the Fortress Mountain formation by means of the Section of Torok formation on Kucher Creek ammonites Colvillia and Beudanticeras; a middle part that contains Subarcthoplites, which occurs in Alberta Tuktu formation. Torok formation (incomplete): Feet in the Clearwater formation and in the upper third of 21. Sandstone, siltstone, and silty shale; sandstone the Loon River formation, and is near the boundary of massive, medium to dark gray, very fine to the lower and middle Albian in Europe; an upper part fine grained, calcareous; more abundant in that contains Gastroplites and Cleoniceras, which is upper part of unit______90 found also in the Tuktu and Grandstand formations, 20. Covered; computed thickness approximately.... 40 and is correlated with the middile Albian in Europe. 19. Sandstone, siltstone, and silty shale; sandstone shaly to thin bedded (}i to 3 in.); greenish Four collections of megafossils were obtained from gray, very fine grained, moderately calcareous, rocks of the Torok formation in the Killik-Etivluk crosslaminated. Mudflow marks on siltstone. 60 Rivers region; they are listed in table 7. The two most 18. Covered; computed thickness approximately__ 80 important collections are from field samples 53 AB1 360 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

TABLE 7. Fossils of the Torok formation [Identifications by R. W. Imlay]

Fossil

USGS cf.Inoceramus Inoceramussp. Isognomon?sp. Subarcthoplites Field sample Mesozoio Stratigraphic position Column Area anglicusI. Imlaybickeli Puzosialsp. Wormboring Elytrumof locality (pi. 47) Cleoniceras tailleuri Fishskeleton Wood juv. Imlay juv. beetle

53 AB1 80...... 25811 X 53AB1 94-.....- . 24639 do-. . . 1 ... -do...... X X 53AB1 100- 24640 do.. . . . do...... X X 50 AE 107. 23173

94 and 53 AB1 100 (USGS Mesozoic Iocs. 24639 and The nature of the contact between the Torok and 24640) (pi. 47, col. 1, sec. B). The ammonite Cleoni­ Tuktu formations cannot be precisely determined from ceras tailleuri Imlay was obtained from 24640, and exposures in the Killik-Etivluk Rivers region. Beds Subarcthoplites bickeli Imlay from 24639; a stratigraphic observed near the contact on the Kurupa River and interval of at least 600 feet is indicated between the two Kucher Creek indicate that the contact is conformable fossil horizons. The stratigraphic interval between the and gradational; however, the northernmost exposure occurrence of Cleoniceras tailleuri Imlay and the top of the Torok formation on the Etivluk River dips 58° of the Torok formation cannot be determined exactly, S. and the southernmost beds of the Tuktu formation but is probably about 2,000 to 3,000 feet. Imlay 4 miles north dip 5° N. In the Chandler River (1961, p. 9) assigned the Cleoniceras in 24640 with the region (Detterman, Bickel, and Gryc, 1963) just east early Albian. of the region under discussion, the contact is locally The Subarcthoplites and Cleoniceras zones, which unconformable, with the degree of angularity ranging represent the middle and upper parts of the Torok from 3° to 20°. formation, are present on the Etivluk River. Fossils NANTJSH.UK GROUP representing the lower zone of Imlay have not been Sedimentary rocks of the Nanushuk group, as found. redefined by Detterman (1956, p. 233-244), are exposed The microfossils collected from the Torok formation in the northern part of the Killik-Etivluk Rivers do not give a clear indication of the age of the beds as region. The Tuktu and Chandler formations are map­ most of the genera are long ranging and nondiagnostic. ped, including the two named tongues of the Chandler Fifty-eight samples were obtained, of which 32 were formations, the Killik and Niakogon. The marine barren. The microfossils are shown in table 5; they Ninuluk formation was not mapped west of the Killik were identified by Bergquist, who reported (written River; however, the Niakogon tongue includes a few communication): "A few poorly preserved micro- microfossil-bearing beds that may be interbedded fossils were found in samples from the Torok formation. thin layers of the Ninuluk formation. These have little value for identifying the section The rocks of the Nanushuk group in the Killik- from which they came, however, as most species are Etivluk Rivers region were mapped as two formations. long ranging and nondiagnostic. One sample (47 AZ The marine beds were mapped as Tuktu formation and 600, Kurupa River) from the upper part of the Torok the nonmarine beds as Chandler formation. The formation has identifiable material: abundant speci­ Tuktu is the lowest unit of the Nanshuk group, but in mens of Haplophragmoides topagorukensis Tappan and this region it differs from the type section on the Chan­ two specimens of Verneuilinoides borealis Tappan; dler River (Detterman, 1956, p. 233-235), in that marine however, this meager fauna only indicates that the tongues in the overlying Chandler formation are sample came from somewhere within the Verneuili­ included in the Tuktu. These marine tongues were mapped as Tuktu because the lithologic character of noides borealis faunal zone (Bergquist, 1958, p. 199). the exposed rocks is more closely related to the Tuktu The presence of specimens of Eurycheilostoma robin- than to the marine Grandstand formation of the sonae Tappan in sample 53 AB1 87 (Etivluk River) Chandler River region (Detterman, 1956, p. 235-237). is unique if this sample is from the lower part of the The lower contact of the Tuktu formation has been Torok formation, because this is the only one in more placed at the base of the first massive sandstone unit than 400 samples in which the species occurred. I in a dominantly marine clastic section. The contact suggest that this may be the upper part of the Torok." with the dark-gray shale and siltstone of the underlying THE KILLIK-ETIVLUK RIVERS REGION 361

Torok formation is gradational and probably trangresses the west and the Chandler River region to the east are time laterally. The upper contact with the overlying shown on figure 62. Chandler formation is at the base of the first nonmarine TUKTU FORMATION coal-bearing beds; this contact is marked also by a Occurrence. The Tuktu formation is exposed in a change in character of the sandstone from a dominantly narrow northwest-trending belt along the southern edge gray green color to a yellow-red-weathering salt-and- of the northern foothills section, and forms a prominent pepper sandstone and conglomerate with a marked south-facing escarpment. This belt is about 70 miles increase in white quartz as a constituent mineral. The long and 0.5 to 1 mile wide. The escarpment is not as contact between the Tuktu and Chandler is generally outstanding in the Killik-Etivluk Rivers region as it is sharp and distinct, but it is not a time line; in fact, the in the Chandler River region, but it is a readily identi­ contact undoubtedly transgresses time boundaries in a fiable topographic feature with relief of 500 to 1,000 feet. northward direction and perhaps to a lesser extent in a The beds that crop out in the escarpment dip north 5° direction normal to the strike. to 20°. The southernmost exposures of the Nanushuk group A second belt of Tuktu formation is exposed along are in the northwest-trending Tuktu escarpment, which, Kurupa anticline, particularly where the anticline is is a continuation of the escarpment that crosses the breached by the Killik, Oolamnagavik, Kurupa, and Chandler Kiver region (Detterman, Bickel, Gryc, 1963, Colville Rivers. The beds in the anticline are folded p. 237) and forms the southern boundary of the more complexly than in the escarpment and are offset northern foothills section of the Arctic foothills prov­ locally by axial thrust faults and small oblique slip ince. The escarpment crosses the Killik River at lat faults. The faulting was most severe in the eastern 68°47' N., and is west-trending as far as Heather Creek; part of the area between the Killik and Oolamnagavik it crosses the Kurupa River at lat 68°50/ N., and then Rivers. The best exposures of the formation in the swings abruptly toward the northwest to form the Killik-Etivluk Rivers region are along this anticline. north bank of Kucher Creek and finally crosses to the The Tuktu intertongues with the overlying Killik north bank of the Colville River opposite the mouth of tongue of the Chandler formation in the northwestern the Etivluk River, at lat 68°59' N. Rocks of the Nanu­ part of the area. This intertonguing relation was shuk group are not present south of the escarpment, observed only on the north flank of Kurupa anticline either because of erosion or nondeposition, mostly the from about 7 miles east of the Kurupa River to the latter as the group has not been identified south of the western boundary of the mapped area. This unit was escarpment in any area. Rocks that differ in lithologic mapped as undifferentiated lower part of Killik tongue character but that may be in part time equivalents of and Tuktu formation, because the tongues are generally the Nanushuk group are present south of the escarp­ too small to show at the scale used on plate 43. The ment in the Torok and Fortress Mountain formations. same relation probably exists on the south flank of the In all, rocks covering about 900 square miles have been anticline and in the exposures along the escarpment, but mapped as Nanushuk group. has not been positively established. The lithologic character of the group in the mapped The upper part of the formation is exposed in the region is very similar to that of the rocks at the type complexly folded and faulted area at Killik Bend, where localities in the Chandler River region (Detterman, the beds have been brought to the surface by a low-angle 1956, p. 233-244); individual beds can be traced from underthrust fault on the south flank of the overturned one region to the other, and, in general, there is close Killik Bend anticline. correlation between these regions. The rocks include Character and thickness. The Tuktu formation in the subgraywacke sandstone, sandstone, conglomerate, Killik-Etivluk Rivers region is dominantly a marine siltstone, claystone, silty shale, and clay shale. Coal, clastic unit similar in gross aspect to the type section on limestone, ironstone (as concretions and beds), and the Chandler River (Detterman, 1956, p. 233-235), but bentonite (in the Niakogon tongue) are intercalated it does contain some beds with littoral characteristics with clastic rocks. and in general has more coarse clastic material than the The group is about 4,450 feet thick along the Killik beds at the type locality. River; it becomes thicker toward the northwest with a The rocks are argillaceous dark-green to medium- maximum of about 6,260 feet along the Colville River gray shaly to massive, very fine to medium-grained downstream from the mouth of the Etivluk River. sandstone, light-yellow-red conglomeratic sandstone, The greatest thickening is between the Kurupa River and gray-green siltstone and silty shale. Subordinate and the western boundary of the mapped area. The constituents include clay shale, ironstone and sandstone relations of the stratigraphic units in the Killik-Etivluk concretions, lenticular beds and concretions of lime­ Rivers region to those in the Utukok-Corwin area to stone, and a few thin seams of coal.

679606 O 63 6 'ON aAnasaa naa^oaxaa TVAVN: THE KILLIK-ETIVLUK EIVERS REGION 363

Conglomeratic sandstone is locally an important siltstone forms about 30 to 40 percent of the exposed constituent of the stratigraphic sequence, whereas in rocks. Ironstone concretions as much as 3 inches in the Chandler River region there is only a small amount diameter are found commonly with the silty shale; of conglomerate in the Tuktu formation. The con­ surface weathering of the concretions has produced a glomeratic sandstone is most abundant along the ferruginous stain on the enclosing rocks. Oolamnagavik River, and probably indicates that the The Tuktu formation is thicker in the western part area was structurally high at the tune the rocks were of the Killik-Etivluk Rivers region than it is at the type deposited and was closer to the shore line. Colored locality (Detterman, 1956, p. 233-235). Two com­ chert is the primary constituent of the conglomerate; plete sections of the formation were measured; the subordinate constituents include white quartz and Colville River section (pi. 48, column 1) is 2,269 feet intraformational sandstone and shale pebbles. The thick and the Kurupa River section is 1,376 feet thick. conglomerate in the Tuktu formation does not have the The other sections are incomplete, owing to faulting or abundant white quartz that is characteristic of the poor exposures. nonmarine Chandler formation, nor does it have the The thicker section west of the Oolamnagavik River iron-stained appearance of the conglomerate of the is due largely to a general thickening of the Nanushuk Chandler formation. Thus the conglomerate of the group in the northwestern part of the area. Some of two formations can be readily differentiated. the additional thickness may be a result of mapping The conglomeratic sandstone is commonly fossilif- beds at the base as Tuktu formation that were mapped erous. The fossils may be derived from reworking of as Torok formation farther east. The additional older beds; however, most of the fossils are casts, so it thickness of Tuktu may also represent in part a north­ is impossible to tell whether they have been abraded west facies change from nonmarine to marine strata. by wave action. The conglomeratic sandstone is The greater thickness of Tuktu in the western part present in all outcrops in the escarpment area. The of the Killik-Etivluk Rivers region and the gradual formation becomes more shaly toward the north and change in lithologic character from that of the type the conglomerate is missing. The littoral facies seem­ section seems to indicate that this stratigraphic se­ ingly indicates that the escarpment occupies about the quence is approaching what Sable (1956, p. 2637-2641) same position as the shore line did during the time the defined as the Kukpowruk formation of the Nanushuk rocks were being deposited. group in the western part of northern Alaska. The sandstone is a subgraywacke and is predomi­ Following are the measured sections of the Tuktu nantly very fine to fine grained, thin to shaly bedded, formation. They are described in the same succession and medium gray to greenish yellow and green; it is as on plate 48. The Colville River section (pi. 48, commonly calcareous and contains much argillaceous column 1) was measured along both banks of the river material. Individual beds can be traced across the near the mouth of the Etivluk River. The Tuktu region in the escarpment, and they show considerable escarpment is on the north side of the Colville River variations in lithologic characteristics, from a marginal- opposite the mouth of the Etivluk River, and most of marine facies on the Oolamnagavik River to marine the section was measured at that locality. The section facies on Kucher Creek and the Colville River. Mud- is on the south flank of the Oolamnagavik syncline and ball concretions and clay galls are common features in the strata dip 5° to 10° N.; this is the thickest section the sandstone. Carbonaceous laminae are present in of the Tuktu formation measured in outcrops in north­ the marginal facies, and a few petrified logs occur in the ern Alaska. The exposed parts of the formation were Kurupa River section (pi. 48, column 2). Some of the taped and the stratigraphic thickness for the cover parts sandstone is crossbedded but few ripple marks were was computed; the total thickness is 2,269 feet. noted. The crossbedding is confined primarily to the thin- to shaly-bedded sandstone and is most com­ Section of Tuktu formation along the Colville River, near the mouth mon in the area between the Kurupa and Colville of the Etivluk River Rivers. A 150-foot unit of fine-grained thin- to me­ Upper part, Killik tongue. dium-bedded friable dark-green sandstone present in the Tuktu formation: Feet 53. Sandstone, thin- to medium-bedded; medium Killik River section cannot be traced westward across grained at base and fine grained at top; green, the region as a single unit. ripple marked, fossiliferous (field sample 47 Clay shale and silty shale combined form less than AZ 546-547)____-___.______-__------60 50 percent of the exposed rocks. In general, the shale 52. Silty shale___.______115 51. Sandstone, thin-bedded, medium-gray, fine­ sequence is not as thick as it is east of the Killik River grained, carbonaceous; minor amount of inter- (Detterman, Bickel, and Gryc, 1963). Silty shale is bedded siltstone; beds 6 in. thick______12 more abundant than clay shale and combined with 50. Silty shale______.___.______90 364 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Tuktu formation Continued Feet Tuktu formation Continued Feet 49. Sandstone, medium-bedded, gray, very fine 23. Sandstone, thin to medium-bedded, light-green, grained, hard, with ironstone concretions 2 to 3 fine to medium-grained; weathers light yellow in. in diameter.______1 red; rubble; computed thickness approxi­ 48. Silty shale____.______10 mately ______20 47. Sandstone, thin-bedded to massive, medium- 22. Covered; computed thickness approximately..-- 25 gray, fine-grained, carbonaceous; ironstone 21. Sandstone, thin-bedded, light-gray, fine-grained; concretions 3 in. to 1 ft in diameter; some rubble; computed thickness approximately. __ 10 interbedded siltstone in upper part of unit__ 25 20. Covered; computed thickness appro ximately..-- 105 46. Silty shale______100 19. Sandstone, thin-bedded, light-green to medium- 45. Sandstone, massive, dark-green, fine-grained; gray, fine-grained; rubble; computed thickness lenticular beds of pebble conglomerate; worm approximately. ______-___-----___---______30 tracks and pelecypod casts (field sample 47 18. Covered; computed thickness approximately..-- 110 ATh 40F)______-_-______-_-_.______5 17. Sandstone, thin-bedded to massive, very fine 44. Sandstone, thin-bedded, dark-green, fine-grained. 15 to fine-grained, light-green to medium-gray. 43. Sandstone, massive, light-green, fine-grained; A few thin layers of /i-in.l black chert pebbles interbedded, swirl-bedded siltstone______10 and laminated siltstone pebbles in lower part 42. Sandstone, thin-bedded, dark-green, platy, fine­ of unit; very calcareous in upper 25 feet; grained ______10 mud-ball concretions common throughout. 41. Sandstone, massive, medium-gray, fine-grained, A few poorly preserved pelecypod casts and highly calcareous______10 worm trails in lower part. In part rubble; 40. Silty shale, sandy, with limestone lenses 1 to 4 ft computed thickness approximately. ______140 thick.--__*_--______---____-______25 16. Siltstone and silty shale; rubble; computed 39. Sandstone, massive, medium-gray, very fine thickness approximately ______30 grained, with interbedded silty shale units 1 ft thick. ______15 15. Sandstone, thin-bedded to shaly-bedded, very 38. Siltstone and silty shale, medium-dark-green; fine grained; light-gray, few fossil worm casts crossbedding in siltstone______25 present; rubble; computed thickness approxi- 37. Limestone, lenticular, medium-gray____-______5 mately______20 36. Silty shale______-_--_..----_--_-----_-______25 14. Siltstone and silty shale rubble; computed 35. Sandstone, highly calcareous____--__.__._.____ 5 thickness approximately ______60 34. Silty shale._.__._----._------___-___._____ 10 13. Sandstone, thin bedded, very fine grained, 33. Sandstone, highly calcareous___-___---______3 light-gray, weathered to yellow gray; ledge forming; carbonaceous laminae, few fossil Lower part, Killik tongue (see page 372). worm casts. In part rubble; computed thick­ Tuktu formation: ness. ______20 32. Siltstone and silty shale rubble; computed 12. Sandstone, siltstone, and silty shale rubble; thickness approximately_____----._--______80 computed thickness approximately ______140 31. Sandstone, massive, light-yellow-red, fine-grained, 11. Sandstone, thin-bedded (1 to 3 in.), fine-grained. 3 with lenticular beds of pebble conglomerate 1 10. Siltstone and silty clay shale ______10 to 5 in. thick; poorly preserved pelecypods 9. Sandstone, massive, fine-grained, dull-green__ _ _ _ 2 (field sample 47 ATh 39F)____----___--_____ 40 3 30. Sandstone, thin-bedded, green, fine-grained_-___ 40 8. Clay shale, dark-blue-gray ______7. Sandstone, thin-bedded to massive, fine-grained; 29. Silty shale, greenish-gray, with numerous small dull-green, layered mudstone concretions as ironstone concretions ______60 much as 1 in. in diameter; carbonaceous Lower part, Killik tongue (see page 373). 15 Tuktu formation: 6. Siltstone, silty shale, and clay shale rubble; 28. Siltstone and silty shale with numerous, small computed thickness approximately ______40 ironstone concretions------_-_-_____-______25 5. Sandstone, thin-bedded, fine-grained, with oc­ 27. Conglomeratic sandstone, medium-green-gray, casional blue chert pebbles as much as 2 thin to medium-bedded, fine to coarse-grained, in. in diameter, and ironstone concretions J_ with concretions of pebble conglomerate as to 3 in. in diameter; abundant carbonaceous much as 24 in. in diameter containing plant laminae. ______20 and pelecypod fossils (field samples 47 ATh 4. Silty shale and clay shale, dark-gray to black, 27f, 47 ATh 37f; USGS Mesozoic loc. 24638) _ 25 with a few interbedded siltstone and very 26. Siltstone rubble; computed thickness approxi­ fine grained sandstone layers. Lenticular beds mately. ______35 of dense hard medium-gray sandstone scat­ 25. Graywacke sandstone, thin-bedded, medium- tered throughout unit in addition to the layered gray, very fine grained, silty; rubble; computed sandstone ______120 thickness approximately.______40 3. Covered interval containing rubble of sandstone, Lower part, Killik tongue (see page 373). siltstone, silty shale, and clay shale. Com­ Tuktu formation: puted thickness approximately.. ______140 24. Covered; computed thickness approximately__ 120 2. Clay shale and silty shale. ______40 THE KILLIK-ETIVLUK RIVERS REGION 365

Tuktu formation Continued Feet Tuktu formation Continued Feet 1. Sandstone, thin to medium bedded, fine grained; 17. Interbedded sandstone, siltstone, and silty shale; light-gray to buff, weathers orange brown; thin-bedded, very fine grained, crossbedded, calcareous in part, ripple marks of oscillation ripple-marked; clay-gall conglomerate, scat­ type; worm trails common. In part rubble; tered pelecypods (field sample 46 ACh 130f). computed thickness approximately ______125 Rubble; computed thickness approximately._ 255 Total______2, 269 16. Covered; computed thickness approximately____ 205 Torok formation. 15. Sandstone, shaly bedded, very fine to fine-grained, light-yellow-red, crossbedded; few chert and The Kurupa River section (pi. 48, column 2) was white quartz pebbles Y& to % in. in diameter; measured in a series of bluffs on the east bank of the petrified logs 6 to 10 in. in diameter_-_-____ 5 Kurupa River just north of the mouth of Heather 14. Graywacke sandstone, medium-bedded, fine- to Creek; in strata on the north flank of Kurupa anticline, medium-grained, greenish-yellow, with numer­ the dip decreases from 45° N. near the anticlinal axis ous elliptical graywacke concretions 1 to 4 in. to 22° N. at the contact with the Killik tongue of the in diameter; crossbedded; few lenticular 4- to 6-in. beds of black chert-grit conglomerate. __ 20 Chandler formation. The section is moderately well 13. Carbonaceous shale______2 exposed. This section of the formation is 5 miles north 12. Covered; computed thickness approximately____ 130 of the escarpment and may not be exactly an equivalent 11. Conglomeratic sandstone, thin- to medium- of the escarpment facies. bedded, fine- to coarse-grained, light-yellow Section of Tuktu formation on the Kurupa River to green-yellow, crossbedded; fair induration. Conglomeratic constituents include chert and Lower part, Killik tongue. shale fragments, grit to pebble size.______24 Tuktu formation: Ft 10. Graywacke, fine-grained, interbedded with fissile 24. Graywacke sandstone, shaly-bedded, light- silty shale; abundant carbonaceous laminae; green to yellow-green, very fine to fine­ Soft ------11 grained, cross-bedded, iron-stained; few 9. Coal, low-grade bituminous-______1 layers of siltstone interbedded; coarse­ grained sandstone concretions with 8. Sandstone, medium-bedded to massive; green to occasional chert and quartz pebbles light-yellow-green, sandstone concretions as and gastropods; pelecypods common much as 3 ft in diameter._-______--_-_ 25 in upper 10 feet of unit (USGS Meso- 7. Sandstone, conglomeratic, and sandstone, silt- zoic loc. 20399)-_------__- 95 0 stone, silty shale, and clay shale. Conglom­ Lower part, Killik tongue (see page 375). eratic constituents are black and green chert Tuktu formation: pebbles; rubble; computed thickness approxi­ 23. Graywacke sandstone, shaly-bedded, very mately. .------240 fine grained, light greenish yellow, 6. Silty shale, medium-gray.-______20 carbonized plant fragments; moderately 5. Sandstone, thin- to medium-bedded, fine-grained, indurated; numerous ironstone nodules; light-gray, crossbedded, ripple-marked; clay a few layers of medium-gray silty shale galls; fossiliferous (USGS Mesozoic loc. 20412) _ 80 interbedded; fossil horizon 5 ft above 4. Sandstone, medium-bedded, very fine grained, base (USGS Mesozoic loc. 20398 and laminated; fissile in part; crossbedded ___-_ 10 field sample 47 AZ-605f)------_---_- 20 3. Sandstone, similar to unit 5.__------35 22. Shale, carbonaceous, coaly_-..__------1 2. Sandstone, siltstone, and silty shale rubble in 21. Graywacke sandstone conglomeratic, mas­ covered interval; computed thickness approxi­ sive, fine- to coarse-grained, dark- mately .- __-----_-_---_------_----_--- 40 greenish-yellow, spheroidal weathered; 1. Sandstone, medium-bedded to massive, very fine numerous fine-grained oval sandstone to fine-grained, greenish-yellow, iron-stained, concretions 2 to 8 in. long; occasional crossbedded- ______-_____---_------_--- 25 chert and quartz pebbles.______25 20. Limestone, pale-yellow, iron-stained, car­ TotaL 1,376 bonaceous. ______9 Torok formation. 19. Graywacke sandstone, fine- to medium- grained, dark-green, soft, friable, cross- The Oolamnagavik River section (pi. 48, column 3) bedded______6 was measured along the west bank of the Oolamnagavik Total. 148 River, where the river cuts through the Tuktu escarp­ Lower part, Killik tongue (see page 375). Tuktu formation: Feet ment. The formation crops out in two bluffs on the 18. Subgraywacke sandstone, thin- to medium- south limb of the Oolamnagavik syncline. The dip of bedded, very fine to fine-grained, light- the strata decreases toward the north from 14° to 5° N. greenish-yellow, well-indurated, crossbedded; ironstone concretions; with interbedded silty The section is incomplete because the lower contact carbonaceous shale in upper 35 ft of section. _ 100 with the Torok formation is not exposed. 366 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Section of Tuktu formation along the Oolamnagavik River Tuktu formation Continued Feet 2. Sandstone, shaly to medium-bedded, very fine Lower part, Killik tongue. grained, pale-greenish-yellow, crossbedded; Tuktu formation: Feet weathered light gray; bedding undulatory; 23. Sandstone, shaly-bedded to massive, light-yellow- oscillation ripple marks______40 green, very fine grained; shaly to thin-bedded * Sandstone similar to unit 2, with a minor in lower part, massive in upper part; carbona- amount of silty shale interbedded; mostly ceous, crossbedded; some ironstaining; cal- rubble; computed thickness approximately..-.__50 careous in shaly part; contains a few chert Total._.______903 pebbles, with a few interbedded layers of silt- The Colville River section at Killik Bend (pi. 48, stone and silty shale_.______85 , , N , ,, ,, , , » ,, 22. Covered interval; computed thickness approxi- Column 4> was measured On the south bank of the mately ______18 Colville River in the first bluff downstream from the 21. Sandstone, irregular bedding; greenish-yellow; mouth of the Oolamnagavik River. The formation very fine to fine grained, calcareous, with few was brought to the surface by a low-angle underthrust black chert granules; fossiliferous (USGS fault on the south flank of the overturned thrust-faulted Mesozic loc. 20395) ______6 T^.1V i -r. i i- T i j.i_ i or. j? ± 20. Sandstone, shaly-bedded, light greenish-yellow, Kllllk Bend antichne ; °^ the uPPer 13° feet are ex~ very fine grained, crossbedded; platy with few posed. The strata dip 30° S. The exposed rock is a chert pebbles }i to 3/i in. in diameter; worm dark-green medium-grained sandstone similar to the trails, scattered pelecypods (USGS Mesozoic sandstone 150 feet below the top of the Killik River loc. 20394)______30 section; consequently the contact with the Killik 19. Covered interval; computed thickness approxi- , , il j. ^ matel 220 tongue may be a fault contact. 18. Sandstone, conglomeratic; primarily chert peb- Section of part of the Tuktu formation at Killik Bend, Colville bles % in. in diameter; few white quartz River pebbles------___--__--__-___--___-______20 Lower part, Killik tongue. 17. Sandstone rubble in covered interval; computed Tuktu formation: Fed thickness approximately. ______175 2. Sandstone, massive, dark-green, fine to medium- 16. Sandstone, thin-bedded to massive, conglomera- grained; weathers red brown; highly fractured tic, light greenish-yellow, fine-grained, soft friable______-_-_--__--- 90 crossbedded, calcareous, with few subround l. Sandstone, medium-bedded, greenish-gray, fine- black and green chert pebbles; ridge-forming grained, laminated; a few layers of silty shale unit; scattered pelecypods (46A Ch 66f)______36 interbedded; pelecypods (U.S.G.S. Mesozoic 15. Covered interval; computed thickness approxi- locality 20406)______-___---_--____40 mately______.______25 Total...... ______130 14. Sandstone, conglomeratic, medium-bedded to Fault massive, light yellow-red, highly iron stained, crossbedded; intraformational sandstone and The Killik River section (pi. 48, column 5) was tabular and roller-shaped shale pebbles_____- 18 measured in the first bluff south of the axis of the 13. Ironstone, sandy ______2 Kurupa anticline, on the east bank of the Killik River. 12. Sandstone, conglomeratic medium-bedded, me- At tmg locality the formation is exposed in a series of dium-gray to green fine to medium.grained; w ffg . which ^ strata are f ^ d . ^ numerous subround chert pebbles with long axis parallel .. . . . , . . , n . f ,, ,. to bedding. ______10 small east-plunging drag folds on the flanks ot the anti- 11. Covered interval; computed thickness approxi- cline. The strata are cut by high-angle reverse faults mately ______15 that are generally parallel to the bedding planes; maxi- 10. Sandstone, shaly-bedded, dark-greenish-yellow, mum displacement probably does not exceed 200 feet, fine-grained, soft; white salt efflorescence; A n , n

abundant and diversified in the part of the formation formation. Imlay (1961) identified three genera: below the lowest nonmarine beds of the Chandler for­ Paragastroplites, Cleoniceras (Neosaynella?), and Cleo- mation. The tongues of Tuktu hi the Chandler for­ niceras (Grytia). Gastropods and echinoderms from mation are locally fossiliferous, but in general the fossil three collections, and an imprint of a squid in one col­ record is meager. lection from the Colville River were identified. Most of the pelecypods, including the diagnostic The fossils identified by Imlay from the Tuktu species Inoceramus anglicus Woods, occur throughout formation are shown in table 8. Some fossil localities the formation hi more or less well-defined horizons; are shown on plate 43 that are not hi eluded in table 8, other species such as Dicranodonta dowlingi McLearn because the material from the unlisted collections had are restricted to the part of the formation below the not been identified at the time of this writing. Con­ lowest nonmarine beds of the Chandler. Other im­ cerning the age and possible correlation of the mega- portant species include Inoceramus cf. /. cadottensis fauna, R. W. Imlay (written communication) stated: McLearn, Entolium utukokensis Imlay, Thracia stelcki "A distinct assemblage of mega- and microfauna ap­ McLearn, Tancredia kurupana Imlay, and Arctiea'? pears in the upper third of the Torok formation, is sp. A tube of a new species of worm of the genus abundant in the Tuktu formation, persists in reduced Ditrupa was identified by Imlay (1961, p. 39-40); it is numbers in the Grandstand formation, and then termi­ characteristic of the Tuktu and is found throughout. nates rapidly. This assemblage can be divided into a Ammonites were found in seven collections from the lower zone characterized by the ammonite Paragastrop- TABLE 8. Fossils of the Tuktu formation {Identifleations by R. W. Imlay. Field samples 46 ATh 106, 4fi ACh 115,124,120,137, Kurupa River; 46 ACh 184, 46 ATh 80, 211, 209, 219, 222,229.J230, 53 ABl 9,108, CoMUe River; ATh 55, 60, 67, 46 ACh 57, 60, 67, 68, Oolamnagavik River; 45 AWa 72, 45 AKr 82, 53 ABl 9,13,14, 48, Killik River]

Stratigraphic position, in feet, from top

50 50- Upper 110 120 140 100-200 Upper 300 530 700 740 900 Lower 100 100 200 I 5 Field sample (USQS Mesozoic locality) Fossil t- to ^j" o> o § 03 o>

Th16A(55 Th16A(211 16ATh209( 16ATh(222 (16ATh229 Th219(16A (16ATh80 (16ATh60 >n Th(16A67 Th16A106 s & 16ATh230 o> Bl(53A21 S M Bl(53A14 Ch46A57 Ch46A124 1 Kr45A82a Ch46A139 Bl10853A Ch46A137 16ACh68 03 Dt53A48 fl i O 3 £ 8 3 o <1

Table 9 .-MicrofossiI chart [R indicates 1 to 12 specimens; C, 13 to 2 5 specimens; and A, over

Upper Cretaceous Lower Cretaceous Nanushuk group Fossil Ninuluk formation Chandler formation and Niakogon tongue of Chandler formation Upper part of Killik tongue Number and interval of samples 1 1 1 1 2 m1 HIII nil1125 m m m n m i 11 Bathy siphon brosgei Tappan B. vitta Nauss mR Saccanmina lathrami Tappan mR mR Reophax minuta Tappan Involutina rotalaria (Loeblich and Tappan ) Glomospira gaultina (Berthelin) Haplophragmoides topagorukensis Tappan Ammobaculites fragmentarius Cushman A. wenonahae Tappan

Siphotextularia? rayi Tappan

Verneuilinoides borealis Tappan (Anger indium ina manitobensis (Wickenden) Gaudryina canadensis Cushman R i G. irenensis Stelck and Wall

Gaadryinella irregularis Tappan

Hiliamnina awunensis Tappan

M. manitobensis Wickenden

Psamminopelta bows he ri Tappan

Spirolocalina ophionea Loeblich R R R and Tappan ! H 1 Trochammina rutherfordi Stelck and Wall Lenticulina erecta (Perner) THE KILLIK-ETIVLUK RIVERS REGION 369

While no direct age correlations were attempted from formation. The Killik tongue is the most widespread the small microfauna of the Tuktu formation in the and persistent unit of the Chandler; it forms the cap Killik-Etivluk Rivers region, it is significant that the rock for the Tuktu escarpment and is the main ridge- fossils are part of the Verneuilinoides borealis faunal forming unit in the northern foothills section. The zone (Bergquist, 1958, p. 199), for most of the fossils formation is present in broad, open folds throughout from this faunal zone are from beds of Albian age. most of the region; it is faulted locally along Kurupa, CHANDLER FORMATION Killik Bend, and Aupuk anticlines, but in general the ^The Chandler formation as mapped in the Killik- statigraphic displacement is only a few hundred feet. Etivluk Rivers region is the same unit as redefined by The two tongues of the Chandler formation are in Detterman (1956, p. 237^241); it consists of two contact in the Killik-Etivluk Rivers region, except tongues, Killik and Niakogon, the Killik being the along the Killik River, where a 40-foot section of lower and thicker. The type localities for both tongues marine Ninuluk formation separates the tongues. In are on the east bank of the Killik River (pi. 43), 5 to 12 the Chandler River region, just east of the area under miles downstream from the mouth of the Okpikruak discussion, a section of Ninuluk formation varying River. in thickness from 40 to several hundred feet is always Most of the exposed rocks of the Nanushuk group in found between the two tongues (Detterman, Bickel, and the Killik-Etivluk Rivers region are in the Chandler Gryc, 1963). The almost complete absence of Ninuluk

for the Nanushuk group 25 specimens. Fossils identified by H. R. Berquist and H. N. Tappanj

Lower Cretaceous Nanushuk' group

Chandler formation Tuktu formation

- . Lower part of Killik tongue and. Tuktu formation

I 1 1 3 3 '321 3113515239 646 1 1 1 2 3 1 2 1 1 4 1 2 1 M M m M il till MmmmRmmm liSlHlfelllisSl lHH ^ {f! PI! P R R R R R il PH 11 il

A R R R R R R R R R il 1 ill 1 11 11 IHI 1 mR R R R R H ii 1 R

R R R R R CA C 11 1 1 il ill R R mR mR m m R R R il 11 ' 1 mR mR A A A A A ARCRCRA ARC R , ~R A R R R AR R ii m m m m mammwm IIP .1.E1P1H11H 1 c R R R R R " PI 1

R R R R R R R R R . C R 1 PI '1 11 1 il JiH If! ill c R R "T; A R R C m . mm m 11 I 1 R R il m mC 11A R illR R A ' iR mmR A mR mR R C R R C .R A* il I -111 Iil ' . m mR R R R C -1 11 11 HI

, 400 .- . 800 1200 SCALE 370 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 formation in the Killik-Etivluk region is due to a south- yellow red, and has a characteristic rust-brown- westward facies change from marine to nonmarine weathered surface. Lenticular beds of pebble con­ strata. The two tongues, although in contact, are glomerate are present locally in the lower part. The distinct mappable units and are described separately. pebbles are about 40 percent white quartz; this is the first occurrence of white quartz as a major conglomer­ KILLIK TONGUE atic constituent, in the stratigraphic sequence of the Occurrence. The Killik tongue of the Chandler Cretaceous of northern Alaska. The remainder of the formation is the lower and thicker of the two tongues pebbles are predominantly black, gray, and green chert, of the formation; it is 2,815 feet thick at the type with minor hematite nodules and limestone pebbles. locality along the east bank of the Killik River between In addition to the sandstone and conglomerate, other lat 68°51 / N. and 68°55/ N. Westward from the type constituents of the lower part of the Killik tongue locality the tongue becomes thicker; it is 3,318 feet include gray to brown micaceous carbonaceous silt- thick along the Oolamnagavik River, 3,760 feet thick stone, sandy silty shale, and coal. Ferruginous nodules along the Kurupa River, and 3,450 feet thick along the commonly containing plant fossils are found in the Colville River. siltstone and silty shale beds. The ironstone beds The beds interfinger with the Tuktu formation in also contain abundant plant remains. the northwestern part of the region. Rocks represent­ The thickest section of the lower part of the Killik ing three marine transgressions, two of which extended tongue is at the mouth of the Oolamnagavik River, as far east as the Kurupa River, were mapped along the where about 1,600 feet was measured or inferred; Colville River. Marine rocks are present in addition the upper 670 feet is poorly exposed, but the remainder to the ones mapped, but the stratigraphic intervals are is well exposed in a bluff at Killik Bend on the south too small to be shown at the scale used on plate 43. bank of the Colville River just downstream from the The Killik tongue by definition is a nonmarine and mouth of the Oolamnagavik. Well-indurated ridge- marginal unit, so it should be borne in mind that ma­ forming sandstone is present, but sandstone is subordi­ rine strata are included with the tongue only as a map­ nate to siltstone and silty shale along the Oolamnagavik ping convenience. River. The sandstone is predominantly thin to medium The best exposures of the Killik tongue are in a belt bedded, fine grained, and dark yellow red to salt and 5 to 8 miles wide just north of the Tuktu escarpment pepper; it has a characteristic rust-brown-weathered where the strata are folded into the Kurupa anticline surface. Coal is more abundant than at the type and Oolamnagavik syncline. In general, the strata locality; 15 beds were measured, the thickest of which dip gently from 5° to 15°; the beds are faulted locally is 6.5 feet. The siltstone and silty shale are quite and may dip as much as 30°. The anticline is more carbonaceous and contain abundant plant fossils and complex structurally than is the syncline; several low- ironstone concretions. A few conglomeratic pebbles angle axial thrust faults offset the beds and small and lenticular beds of pebble conglomerate are present oblique slip faults are present mear the anticlinal axis in the sandstone. The section exposed just north of both east and west of the Kurupa River. The northern the Tuktu escarpment on the Oolamnagavik River has belt of Killik tongue is one of low relief, generally less abundant conglomerate beds, but very little con­ than 200 feet, and is partly obscured by a gravel glomerate is present in the section at the mouth of terrace. The beds dip less than 20° for the most the river, 13 miles north of the escarpment. part, except in the structurally complex zone at Killik West of the Oolamnagavik River the lower part of Bend, where the Killik Bend anticline is overturned the Killik tongue becomes thinner and the upper part and offset by numerous west-trending high-angle re­ becomes thicker, owing partly to a facies change. verse faults and a low-angle underthrust fault with The sequence becomes more marginal-marine with an associated drag folding. increase in the siltstone and silty shale content at the The Killik tongue can be divided into an upper and expense of the sandstone. The latter is dominantly a lower part which are lithologically distinct. The thin to medium bedded, very fine to fine grained, and two units were mapped throughout the Killik-Etivluk medium gray to light yellow red. Ironstone concretions Rivers region and are described individually. are abundant and one limestone bed is present in the At the type locality the lower part of the Killik Colville River section. Pebble-granule conglomerate tongue is 1,095 feet thick. Well-indurated ridge- is a fairly common constituent of the tongue along the forming sandstone constitutes the bulk of the exposed Colville and Kurupa Rivers; it generally occurs as section. The sandstone is predominantly medium lenticular beds, but may form concretions and nodules bedded to massive and fine to coarse grained; it ranges associated with a coarse-grained salt-and-pepper in color from salt-and-pepper to various shades of sandstone. THE KILLIK-ETIVLUK RIVERS REGION 371

The upper part of the Killik tongue is 1,720 feet thick measured in the escarpment, and the upper part was at the type locality along the Killik River. This part measured along the Colville Kiver 5 miles upstream of the tongue is not as well exposed as is the lower part, from the mouth of the Awuna River. The section was but is characterized by massive ledge-forming conglom­ measured by Thurrell and Zumberge in 1947. erate. White quartz constitutes about 40 percent of the conglomerate. Most of the pebbles are slightly oblong, well rounded, % to 1% inches in length, with a few Section of Killik tongue along the Colvilte River, between the Etivluk , . rra T on£* Awuna Rivers cobbles as much as 4 niches in length. The sandstone Niakogon tongue is thinner bedded, finer grained, and more argillaceous Upper part, Killik tongue: peet than in the lower part. Siltstone and silty shale are 80. Coal______6 common; both are carbonaceous and micaceous. 79. Covered; computed thickness approximately.... 20 Coal float was noted, but is not abundant. Plant fossils 78- Sandstone, thin- to medium-bedded, medium- are moderately abundant, particularly in the ironstone 77 r gray'very fine,grHa d' crossbedded------W .. J JC J 77. Covered; computed thickness appro ximately____ 80 "ecls. 76. Sandstone, conglomeratic, massive with an oc- The conglomerate bed that forms the contact between casional thin bed; light- to medium-gray; fine the upper and lower parts of the Killik tongue can be to medium grained; weathers to light yellow traced from the Killik River to the western boundary of Ted> wood fragments common. Conglomer- the mapped area, as can some of the other conglom- atic constituents primarily subrounded white , i , , . rm , , i quartz pebbles H m. in diameter.. -____--__.._ 15 erate beds 01 the type section. The conglomerate beds 75 Coal ______1 in the upper part of the Killik tongue are more persistent 74. Covered interval; computed thickness approxi- laterally than are those of the lower part. mately ______100 The upper part of the Killik tongue is similar to the 73 - Sandstone, massive, medium-gray, fine-grained, lower part in that it becomes more marginal toward t^cf^^ ******* ^ ^^ * *° * ' 20 the western part of the area where it intertongues 72 SatyC shale","ironstone"concretions,"and""coal with the Tuktu formation. The siltstone and silty rubble; computed thickness appro ximately____ 50 shale content increase in the western part of the area, 71. Siltstone-______10 and several black carbonaceous limestone beds were 70- Coal ------3 noted on both the Kurupa and Colville Rivers. The 69' ^ * * ; computed thickness approxi- siltstone and silty shale are similar to that in the lower 68 part of the tongue, and the sandstone is dominantly crossbedded-______10 medium bedded, medium grained, salt-and-pepper to 67. Covered interval; computed thickness approxi- light yellow red. Some of the sandstone is crossbedded mately ______--_------_--_ 10 and ripple marked. 66' Sandstone> medium-gray, very fine grained, and , . ... micaceoussiltstone__-___--__-----_------15 I he thickest measured section is on the Kurupa 65 (^j l River, where the upper part of the tongue is 2,474 feet 64. Sandstone with interbeds of siltstone; similar to thick; it is 2,176 feet thick along the Colville down- unit66______- -- 30 stream from the mouth of the Etivluk River. At the 63- Coal ------1 i ,, i ,. ji rri i i j j.- i~ -A J.J. 62. Siltstone with thin-bedded very fine grained latter location the Tuktu formation reaches its °greatest sandstone, , interbeds,. , , , ironstone. , beds,, , and , con-nrtT1 thickness in the mapped area; consequently, the total cretions_.______-___------_ 25 thickness of the Killik tongue and Tuktu formation is 61. Coal______------_-- 2 greatest in the western part of the area. The westward 60. Siltstone. ______-____-____-__------_----- 10 component of thickening of the Killik and Tuktu 59. Silty shale and coal rubble; computed thickness ^ sequence is about 25 feet per mile, or about 1,500 feet 58 aS^^^d^''^^^^^^7'^ between the Killik and Etivluk Rivers. This increase grained,silty,micaceous______10 in the stratigraphic sequence may indicate a deepening 57. Covered interval; computed thickness approxi- of the depositional basin northwest of the mapped mately ______--_------20 area 56. Sandstone, medium-dark-gray, very fine grained; / ^ -r. weathers yellow red; calcareous; abundant Ihe Colville River section (pi. 48, column 1) was fossilwood______---__------_ 5 measured along both banks of the Colville River 55. Siltstone, silty shale, sandstone, and coal rubble; between the Etivluk and Awuna Rivers, where the computed thickness approximately ______60 Colville cuts across the Tuktu escarpment. The best 54> Coal ------2 , . . . , , «. ,. -, i ,, 53. Covered interval; computed thickness approxi- outcrops are in a series of river blunts formed by the ,, _____ 15 big meanders in the Colville River near the mouth of 52. Sandstone^""massive,~~ medium-gray, fine- to Kucher Creek. The lower part of the tongue was medium-grained______.___--_----_----- 30 372 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Upper part, Killik tongue Continued Feet Upper part, Killik tongue Continued Feet 51. Silty shale rubble; computed thickness approxi­ 18. Silty shale and coal rubble; computed thickness mately. ______30 approximately ______25 50. Sandstone, shaly-bedded, light-gray, very fine 17. Sandstone rubble; computed thickness approxi- grained, silty; mud-ball concretions______20 mately_---__._ _.______10 49. Covered interval; computed thickness approxi­ 16. Covered interval; computed thickness approxi­ mately ______20 mately ______100 48. Coal______-__---__-___-____-______1 15. Sandstone, massive, medium-gray to dark-green, 47. Siltstone, micaceous, and very fine grained sand­ fine-grained, carbonaceous. ______70 stone.--..- _-___-____-_-______-_-__--__ 30 14. Covered interval; computed thickness approxi- 46. Sandstone, thin to medium-bedded, medium-gray mately.. ______40 to green, fine to coarse-grained; weathers 13. Sandstone, thin to medium-bedded, gray, fine- yellow red; crossbedded; plant fossils__._____ 50 to medium-grained, crossbedded; contains 45. Silty shale with three 5-ft interbeds of massive minute specks of ferruginous material, lenses fine-grained sandstone----______-______50 and beds of calcareous ironstone, and abundant 44. Sandstone, massive, very fine grained, with fossil plant fragments______8 interbeds of siltstone and ironstone; cross- 12. Covered interval; computed thickness approxi­ bedded ______-__- _ 30 mately ______20 43. Coal______1 11. Sandstone, massive, light-gray, fine-grained; 42. Covered interval; computed thickness approxi­ weathers rust brown; hard, nonporous; rubble, mately. ______10 computed thickness approximately. ______7 41. Sandstone, medium-gray, fine-grained; oscilla­ 10. Covered interval; computed thickness approxi­ tion ripple marks with wave length of 1 in., mately ______40 amplitude of % in______3 9. Sandstone, medium-bedded, gray, fine- to 40. Silty shale.__. ______.-__.______'. 10 medium-grained; weathers orange brown; 39. Sandstone, dark-gray, massive, medium-grained, crossbedded, ferruginous. In part rubble; calcareous, carbonaceous.---__-______5 computed thickness approximately ______15 38. Silty shale. ______15 8. Covered interval; computed thickness approxi­ 37. CoaL______-___-__-___-_.___ 3 mately ______25 36. Sandstone, medium-bedded, medium-gray, very 7. Sandstone, conglomeratic massive, gray, medium- fine grained, crossbedded______-___--___ __ 15 to coarse-grained, carbonaceous; contains 35. Covered interval; computed thickness approxi­ fossil wood; conglomeratic constituents are mately. ______20 subangular black chert pebbles scattered 34. Coal rubble; computed thickness approximately. 2 throughout unit______-__-______--__------20 33. Covered interval; computed thickness approxi­ 6. Covered interval; computed thickness approxi­ mately. ______20 mately ______25 32. Sandstone rubble; computed thickness approxi­ 5. Sandstone, conglomeratic, medium-bedded to mately. ______10 massive, greenish-gray, fine-grained; weathers 31. Silty shale and coal rubble; computed thickness brownish black. Lenticular beds % to 1 in. approximately.. - -______10 thick of .subangular to subround chert and 30. Sandstone rubble; computed thickness approxi­ white quartz pebbles; predominatly black mately ______1 ______10 40 29. Silty shale and coal rubble; computed thickness ;4. Covered interval; computed thickness approxi­ approximately. . ______10 mately______!______190 28. Sandstone and siltstone rubble; computed thick­ 3. Sandstone, medium-bedded, , light-gray, fine­ ness approximately.. '-.-______^____ 10 grained; weathers light tan; porous, cross-bed­ 27. Silty shale rubble; computed thickness approxi­ 40 mately ______-______^_____-______10 ded; ironstone concretions____-______26. Sandstone and siltstone rubble; computed thick­ 2. Covered interval; computed thickness approxi­ 210 ness 'approximately. ______20 mately. ______^______25. Covered interval; computed thickness approxi­ 1. Sandstone, conglomeratic, massive, greenish-gray, mately _-______-__-_____--l____ 20 coarse-grained; fossil wood fragments. Con­ 24. Sandstone, massive, medium-gray, medium- glomeratic constituents are primarily black grained, moderately porous, crossbedded____ 15 chert pebbles with a few white quartz pebbles. 100 23. Covered interval; computed thickness approxi­ mately ______30 2,-176 22. Clay shale______10 21. Sandstone, massive, medium-gray, fine- to Tuktu formation (see page 364). medium-grained; weathers yellow red; cal­ Lower part, Killik tongue: careous; abundant fossil wood and mud-ball 35. Silty shale and coal rubble; computed thickness concretions. ______-._____-______-^_ 75 approximately ______'______^____ 50 20. Coal and ironstone rubble; computed thickness 34. Sandstone, - thin- to medium-bedded, medium- 15 gray, very fine grained; weathers to dark yel­ 19. Ironstone, limy- 5 low red; silty--,______^______20 THE KILLIK-ETIVLUK RIVERS REGION 373

Lower part, Killik tongue Continued Feet Lower part, Killik tongue Continued Feet 33. Siltstone and silty shale; siltstone units 2 to 4 3. Sandstone, massive, very fine grained, silty, hard, feet thick, silty shale units 5 to 8 feet thick; highly calcareous; rubble; computed thickness calcareous.-_---__--___-___-______25 approximately.______25 32. Coal______2 2. Sandstone, siltstone, silty shale, and ironstone 31. Siltstone and silty shale with limestone and iron­ concretions; rubble; computed thickness stone concretions.-. __-____-____-----______35 approximately ______135 30. Sandstone, massive, medium-gray, very fine 1. Sandstone, massive, medium-gray to light-yellow- grained; weathers dark yellow red______3 red, fine-grained; carbonaceous material and 29. Silty shale______10 plant fossils.______100 28. Coal_-_--__-__-_____-______2 27. Clay shale____--_-__--__--______2 Total------1,274 26. Coal___-----______3 Tuktu formation. 25. Silty shale__-_--______.______10 24. Sandstone, massive, medium-gray, very fine The Kurupa River section (pi. 48, column 2) was grained.______5 measured on the east bank of the Kurupa River between 23. Siltstone and silty shale with numerous small lat 68°54' N. and 68°57' N. near Heather Creek. The ironstone concretions; rubble; computed thick­ ness approximately. ______170 section is exposed in a series of discontinuous ledges 22. Sandstone, thin-bedded, dark-green, fine-grained; and cutbanks on the north flank of Kurupa anticline silty shale and coal interbedded with sand­ where the strata dip 7° to 20° N. The exposed part of stone; rubble; computed thickness approxi­ the section was measured. The computed strati- mately______50 graphic thickness for the covered intervals should be 21. Conglomerate, massive, pebble-granule; primarily rounded chert with little white quartz; sand­ accurate to within 10 percent. The section was stone matrix.. ______40 measured by Chapman and Thurrell in 1946; it was 20. Limestone, black, carbonaceous.______1 reexamined in 1947 by Thurrell and Zumberge, and in 19. Silty shale, green, carbonaceous, with sandstone 1950 by Eberlein and Reynolds. interbeds ^ to 2 in. thick; fine grained. ______20 18. Sandstone, thin-bedded, light- to medium-gray, Section of the Killik tongue along the Kurupa River fine-grained, ripple-marked; worm trails; few Niakogon tongue. siltstone interbeds.__--__----______10 Upper part, Killik tongue: 17. Siltstone and silty shale with limestone concre­ Ft In tions; fossil tree trunks standing upright in 66 Sandstone, siltstone, silty shale, clay section; mostly rubble; computed thickness shale, coal, and ironstone; rubble in approximately. _ _-----_-_--______130 covered interval; computed thickness approximately ______------_- 110 16. Sandstone, very fine grained, silty, crossbedded. 10 65. Sandstone, thin-bedded, light-yellow-red; 15. Coal______6 very fine grained, interbedded siltstone 14. Silty shale______15 and ironstone; numerous plant fossils__ 27 13. Coal..______2 64. Sandstone, claystone, clay shale, silty 12. Silty shale______40 shale, coal, and ironstone; rubble; com­ 11. Sandstone, -conglomeratic, thin-bedded to mas­ puted thickness approximately.______40 sive, gray, fine to medium-grained; few silt- 63. Sandstone, thin- to medium-bedded, pale- stone interbeds. Conglomeratic constituents yellow-red, medium- to coarse-grained; include angular to subangular pebbles of black ironstone beds and concretions.-.----- 15 chert and white quartz______60 62. Siltstone, silty shale, clay shale, coal and Tuktu formation (see page 364). ironstone; rubble; computed thickness Lower part, Killik tongue: approximately ______-_------50 10. Coal...______6 61. Siltstone and claystone with a few thin 9. Claystone...______1 layers of sandstone and ironstone inter- 8. Sandstone, medium-bedded, medium-gray, coarse­ bedded...._._..-.--.------10 grained, very hard, crossbedded; limestone con­ 60. Sandstone, thin-bedded, medium-gray, cretions. ______15 very fine grained; weathers yellow red; 7. Coal____.______3 crossbedded-______----__----- 8 6. Silty shale, black; bony layers. ______8 59. Covered interval; computed thickness Tuktu formation (see page 364). approximately ______------180 Lower part, Killik tongue: 58. Sandstone, medium-bedded, medium- to 5. Subgraywacke sandstone and siltstone, massive, coarse-grained, salt-and-pepper, weath­ medium-gray, very fine grained; rubble; com ers moderate yellow red; abundant puted thickness approximately.______20 wood fossils and coaly lenses ______40 4. Subgraywacke sandstone, siltstone, silty shale, 57 Sandstone, siltstone, and silty shale rub­ and coal rubble; numerous ironstone concre­ ble in covered area; computed thickness tions; computed thickness approximately._,_. 240 approximately _._,_.______--.__.-,- 75 374 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Upper part, Killik tongue Continued Ft In Upper part, Killik tongue Continued ft In 56. Sandstone, conglomeratic, massive, me­ 25. Conglomerate, massive Continued dium-grained, with lenticular beds of white quartz; matrix is medium- chert- and quartz-pebble conglomerate grained salt and pepper sandstone; 3 ft thick______30 0 abundant wood fossils______6 0 55. Conglomerate, massive, pebble-size, chert 24. Sandstone, medium-grained______6 0 and quartz.______8 0 23. Coal, soft, chunky______6 0 54. Sandstone, medium-bedded, medium- to 22. Sandstone and siltstone, with several thin coarse-grained; few pebbles.______6 6 beds of bone and ironstone.______10 0 53. Limestone, pale-yellow-brown______3 21. Covered; computed thickness approxi- 52. Claystone______.______3 mately______-___.______65 0 51. Sandstone, thin- to medium-bedded, 20. Sandstone, thin-bedded, medium-gray, medium-gray, fine-to coarse-grained. __ 4 0 fine- to medium-grained, crossbedded; 50. Sandstone, thin-bedded, pale-yellow, very beds and concretions of ironstone___ _ 10 0 finegrained______15 0 19. Clay shale, fire clay, and coal; rubble; 49. Siltstone and claystone______8 0 computed thickness approximately-__. 10 0 48. Conglomerate; local unconformity be­ 18. Sandstone, thin-bedded, very fine grained; tween this and overlying unit ______3 0 grades into siltstone-______10 0 47. Covered; computed thickness approxi- 17. Sandstone, siltstone, silty shale, and coal mately______85 0 rubble; computed thickness approxi­ 46. Conglomerate, massive, pebble-cobble; mately______215 0 predominantly Yz to 1 in. long with few 16. Coal and underclay, rubble; computed cobbles as much as 4 in. long. Chert thickness approximately -.--______5 0 and quartz in about equal proportions. 25 0 15. Sandstone, thin-bedded, light-gray, fine­ 45. Sandstone, thin- to medium-bedded, me­ grained, crossbedded, with considerable dium- to coarse-grained ______5 0 slickensided calcite; ironstone beds.___ 10 0 44. Siltstone, coal, and ironstone rubble in 14. Sandstone, siltstone, silty shale, ironstone covered interval; computed thickness beds, and several coal beds; rubble; approximately. ______125 0 computed thickness approximately.___ 70 0 43. Coal______-_-______. 1 0 13. Sandstone, thin-bedded, light-gray, fine- 42. Clay shale and fire clay with thin coal to medium-grained, crossbedded, with seams______6 0 scattered ironstone beds______20 0 41. Sandstone, thin-bedded, pale-yellow-red, 12. Coal and siltstone rubble; computed fine-grained, ironstone concretions_____ 4 0 thickness approximately______150 0 40. Covered interval; computed thickness ap­ 11. Sandstone, medium-grained, interbedded proximately. ______50 0 with siltstone and ironstone; abundant 39. Siltstone______5 0 carbonaceous material______20 0 38. Sandstone, pale-yellow-red, fine- to me­ 10. Sandstone, siltstone, silty shale, and coal dium-grained, crossbedded; ironstone rubble; computed thickness approxi­ concretions..______20 0 mately______240 0 37. Siltstone and limestone rubble in covered 9. Coal, chunky.______.. 3 0 interval; computed thickness approxi­ 8. Sandstone, thin- to medium-bedded, light- mately______30 0 yellow-gray, medium- to coarse-grained; 36. Claystone______._____ 2 0 weathers moderate yellow red; lami­ 35. Covered; computed thickness approxi­ nated, crossbedded; with slickensided mately______10 0 calcite and abundant plant fossils. _ ___ 30 0 34. Sandstone, thin-bedded, pale-yellow-red, 7. Sandstone, siltstone, silty shale, coal, and fine- to medium-grained, crossbedded; ironstone rubble; computed thickness wood fossils and ironstone concretion _ _ 8 0 approximately.--.------240 0 33. Sandstone, siltstone, and ironstone, inter- bedded______4 0 6. Sandstone, conglomeratic, medium- 32. Asphalt rock, or petroliferous black lime­ bedded, medium-yellow-red, fine- to me­ stone ______2 dium-grained; lenticular beds of pebble 31. Coal______2 0 conglomerate; numerous plant fossils__ 10 0 30. Siltstone and clay shale.____-_-_-_.___- 2 0 5. Conglomerate; pebbles and cobbles of 29. Clay shale with bony partings.______6 0 chert and white quartz ______-__-- 3 0 28. Siltstone.______.._____... 3 0 4. Sandstone, conglomeratic, fine- to coarse­ 27. Limestone, pale-yellow, massive; abund­ grained; lenticular pebble-conglomerate ant plant fossils..______2 0 beds; numerous plant fossils______--_ 15 0 26. Covered; computed thickness approxi­ 3. Sandstone, pale-yellow-red, fine-grained, mately______--_-_-----_-__ 70 0 crossbedded-.______-_------15 0 25. Conglomerate, massive; pebbles }i to >_ in. 2. Sandstone, siltstone, silty shale, and coal; in diameter; 80 percent subround, black rubble; computed thickness approxi- and green chert, and 20 percent rounded mately...______200 0 THE KILLIK-ETIVLTTK RIVERS REGION 375

Upper part, Killik tongue Continued In Tuktu formation (see page 365). Ft In 1. Sandstone, conglomeratic, medium- Lower part, Killik tongue: bedded, light-gray, fine- to coarse­ 3. Covered; computed thickness approxi­ grained, with lenticular beds of pebble- mately.______185 0 conglomerate; consists of white quartz, 2. Sandstone, thin to medium-bedded, pale- black and green chert, and less than yellow to greenish-yellow, fine-grained, 5 percent gray quartzite __ __.___-__ 20 carbonaceous, with few medium-gray silty shale interbeds.______15 0 Total..______....__..___._..___ 2,484 1. Sandstone, conglomeratic, massive, pale- greenish-yellow, very fine to fine­ Lower part, Killik tongue: grained, with few widely scattered 19. Siltstone, silty shale, and coal rubble; com­ black chert and white quartz pebbles puted thickness approximately__.__ 140 % to % in. in diameter; numerous clay 18. Sandstone, irregularly bedded, medium- galls and carbonized plant fragments..._ 50 0 gray salt-and-pepper, very fine grained; weathers light yellow red; crossbedded, Total. 1,286 ripple-marked______10 Tuktu formation. 17. Sandstone, siltstone, silty shale, and coal. Sandstone fine grained, dull yellow red The Oolamnagavik River section (pi. 48, column 3) to gray salt-and-pepper, crossbedded, was measured on the excarpment on the northwest ironstained; slickensided calcite. Mostly bank of the river by Chapman and Thurrell in 1946. rubble; computed thickness approxi­ The section is on the south flank of the Oolamnagavik mately______220 syncline in strata that dip 5° to 8° N. Only the lower 16. Sandstone, subgraywacke; interbedded with soft fissile silty iron-stained shale and 243 feet was measured. siltstone; carbonaceous layers in silt- Section of part of the Killik tongue on the Oolamnagavik River stone ; ironstone concretions______20 Feet 15. Covered; computed thickness approxi­ Lower part, Killik, tongue: mately______150 4. Sandstone, conglomeratic, thin to medium- 14. Sandstone, massive, light to moderate- bedded, pale-yellow-red, fine to coarse-grained; yellow-red, very fine to fine-grained, some beds fissile; crossbedded. Pebble con­ well-indurated. ______10 glomerate in beds 4 to 6 in. thick is 60 percent 13. Siltstone, silty shale, coal and bone, and black chert, 30 percent white quartz, 10 per­ 18 ironstone concretions; rubble; computed cent colored chert and light-gray quartzite____ thickness approximately.______55 3. Sandstone, shaly-bedded, pale-yellow; weathers red brown; occasional pebble-conglomerate 12. Sandstone, subgraywacke, and siltstone; layer; chert and white quartz______95 irregular beds 1 to 3 ft thick; medium- 2. Sandstone, light-gray, siltstone, and silty shale gray; ironstone nodules--____--_---__ 10 80 11. Coal, low-grade, bone, and coaly shale. ___ 4 rubble; computed thickness approximately _ 10. Siltstone and silty shale, medium-gray, 1. Sandstone, shaly-bedded, light-gray, very fine to fine-grained, with an occasional pebble _ 50 carbonaceous, iron-stained; siltstone concretions in the shale.______10 9. Sandstone, siltstone, and silty shale rub­ __-____-___------243 ble in covered interval; computed Tuktu formation. thickness approximately___._____-__ 40 The section from the lower Oolamnagavik River and Tutktu formation (see page 365). Lower part, Killik tongue: Killik Bend of the Colville River (pi. 48, column 4) 8. Covered; computed thickness approxi­ was measured by Chapman and Thurrell in 1946, and mately______270 by Detterman and Bickel in 1953. The lower part of 7. Clay shale rubble; computed thickness the tongue is well exposed along the Colville River approximately ______10 in beds that dip 22° to 25° S. The upper part of the 6. Sandstone, conglomeratic medium-bed­ tongue is represented by a series of discontinuous ded to massive, pale-yellow-gray, fine- to very fine-grained; weathers moderate ledges and rubble traces along the Oolamnagavik yellow red, with lenticular conglomer­ River in strata that dip 10° to 16° S. ate beds 6 to 8 in. thick of subangular Section of the Killik tongue on the Oolamnagavik River and at to subrounded black, gray, and green Killik Bend, Colville River chert % to % in. in diameter; some rounded white quartz pebbles. A few Niakogon tongue. Upper part, Killik tongue: Feet sandstone concretions and one 6-in. 17. Sandstone, thin- to medium-bedded, dark-yellow- fissile shale bed in center of unit- _____ 60 red, fine-grained, argillaceous; interbedded with 5. Carbonaceous shale___--______--_-_ 1 micaceous carbonaceous siltstone, silty shale, 4. Covered; computed thickness approxi- coal, and ironstone. Rubble; computed thick­ mately..______25 ness approximately- ____-_-_-____------_--_ 25 376 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Upper part, Killik tongue Continued Feet Lower part, Killik tongue Continued Ft in 16. Covered interval; computed thickness approxi­ 92. Covered interval; computed thickness mately______110 approximately-__-__-_-_-______-__-- 25 0 15. Sandstone, medium-bedded, light-gray, fine- to 91. Sandstone, medium- to heavy-bedded, medium-grained, crossbedded; abundant plant dark-gray to yellow-red, fine-grained, and fern fossils; 6-in. ironstone bed at base - 10 carbonaceous-______15 0 14. Clay shale, coal, siltstone, and ironstone rubble; 90. Silty shale, dark-gray, fissile, carbonaceous- 4 0 computed thickness approximately-______30 89. Siltstone and sandstone, dark-gray, very 13. Sandstone, thin- to medium-bedded, light-gray fine-grained ______-_____-_-_-- 5 0 to yellow-red, fine- to medium-grained; inter- 88. Covered; computed thickness approxi- bedded with siltstone, silty shale, coal, and mately___-_-__----_-_-_---_-____--- 5 0 ironstone both as beds and concretions; exposed 87. Sandstone, heavy-bedded, dark-yellow- as a series of rubble traces; computed thickness red, fine-grained______-______- 29 0 approximately ______590 86. Siltstone and silty shale, carbonaceous.-- 7 0 12. Sandstone, massive, fine-grained, dark-yellow- 85. Covered; computed thickness approxi- red, argillaceous; abundant plant fossils._____ 8 mately______--__-_---_---__--_- 10 0 11. Covered interval; computed thickness approxi­ 84. Coal______1 0 mately. ______140 83. Sandstone. _ -_ - - 2 0 10. Sandstone, thin-bedded to massive, dark-yellow- 82. Coal------6 red, fine- to medium-grained, argillaceous, car­ 81. Siltstone, silty shale, and fine-grained bonaceous; several layers of siltstone and silty dark-yellow-red carbonaceous sand- shale containing ironstone nodules interbedded- 20 stone______-__-----__----- 15 0 9. Sandstone, siltstone, silty shale, and ironstone 80. Covered; coal rubble; computed thickness rubble in covered interval; computed thickness approximately.---______------_--- 20 0 approximately. ______380 79. Silty shale, coal stringers. _ - _- 6 0 8. Sandstone, thin-bedded, fine-grained, salt-and- 78. Sandstone, heavy-bedded, dark-yellow- pepper______5 red, fine- to medium-grained______12 0 7. Conglomerate, massive; pebble and cobbles l/i to 77. Covered; computed thickness approxi­ 3 in. in length, average about 1 in.; 50 percent mately_ _ _ - --- 5 0 white quartz, 40 percent black chert, 10 per­ 76. Siltstone and sandstone, dark-yellow-red cent colored chert and elliptical hematite with greenish cast, fine-grained; car­ nodules with flat axis parallel to bedding; one bonaceous, argillaceous. ______5 0 petrified log 10 feet long______50 75. Covered; computed thickness approxi- 6. Sandstone, thin-bedded, fine-grained, salt-and- mately...... -_------_------5 0 pepper, conglomeratic; siltstone and silty 74. Sandstone, siltstone, and silty shale; iron­ shale interbedded ______15 stone concretions.-______19 0 5. Sandstone, medium-bedded to massive, salt- 73. Siltstone, sandy______-_.___------11 0 and-pepper, coarse-grained, conglomeratic. ___ 10 72. Covered; computed thickness approxi- 4. Sandstone, siltstone, silty shale, ironstone, few mately___-_-___---__---_------5 0 chert and quartz pebbles, mostly rubble; com­ 71. Sandstone, dark-yellow-red very fine puted thickness approximately.______180 grained, silty__---_-___------5 0 3. Sandstone, shaly to thin-bedded, fine- to medium- 70. Covered; computed thickness approxi­ grained; weathers dark yellow red; interbedded mately. ______-__ -___ - - 3 0 lenticular siltstone and silty shale, and iron­ 69. Siltstone and silty shale.______5 0 stone; few thin coal seams; in part rubble; 68. Siltstone, carbonaceous______5 0 computed thickness approximately ______55 67. Covered; computed thickness approxi­ 2. Sandstone and siltstone rubble in covered interval; mately.-______-_------8 0 computed thickness approximately ______65 66. Coal. -__ - - - 1 8 65. Silty shale..------6 0 1. Sandstone, conglomeratic, medium-bedded, salt- and-pepper, medium-grained; rubble; com­ 64. Coal------2 4 puted thickness approximately.______20 63. Siltstone, dark-yellow-red, silty shale, and sandstone; medium bedded, fine Total______.______1,713 grained; weathers rust brown to maroon.__--_---__-_--__------9 0 Lower part, Killik tongue: Ft in 62. Covered; computed thickness approxi 96. Covered interval; computed thickness mately______.-__.------4 0 approximately ______665 0 61. Sandstone, heavy bedded, dark-gray with 95. Sandstone, shaly-bedded, medium-gray greenish cast; fine grained------10 0 fine-grained, crossbedded_---_-----___ 5 0 60. Siltstone, dark-yellow-red; silty shale, 94. Sandstone, conglomeratic, massive, me­ and fine-grained sandstone.______---- 22 0 dium- to coarse-grained with lenticular 59. Covered; computed thickness approxi­ conglomerate beds of chert and quartz mately. ------7 0 pebbles______10 0 58. Sandstone, medium bedded, dark-gray 93. Silty shale-______-____-____.______10 0 with greenish cast, fine grained, silty __ 13 0 THE KILLIK-ETIVLUK RIVERS REGION 377

Lower part, Killik tongue Continued ft in Lower part, Killik tongue Continued Ft in 57. Silty shale..______1 0 13. Coal _ _._.__.__..______1 2 56. Sandstone._--___-___--____-_____-____ 2 0 12. Siltstone and silty shale, sandstone lenses. 50 0 55. Covered; computed thickness approxi- 11. Covered; computed thickness approxi­ mately ___ - _ -_ -- 6 0 mately __ ------_-_ 20 0 54. Sandstone, medium-bedded dark-yellow- 10. Siltstone and silty shale______-_____ 6 0 red-- _-_--__--__-______--_ 15 0 9. Covered; computed thickness approxi- 53. Coal__-__--___-__---_-______- 4 mately -_ _- --_-____ _ - 6 0 52. Silty shale and siltstone______25 0 8. Silty shale, siltstone, and dark-gray sand- 51. CoaL-.------_------_--_----_-_--_ 1 10 stone, weathers brown______20 0 50. Siltstone, silty shale, and massive, dark-gray 7. Silty shale.______15 0 to yellow-red, fine-grained, argillaceous 6. Covered; computed thickness approxi- sandstone.---_------._-__ 40 0 mately--______10 0 49. Siltstone with ironstone concretions------40 5 Siltstone ______30 0 48. Siltyshale _ 4 0 4] Coal_.._.^."^___""....".___."___.^ 6 6 . ' o,?a ------o 3 Sandstone, massive medium-green, fine- 46. Si tstone and silty shale _____ 5 0 grained; plant fragments._..______.. 9 0 45. Silty shale, ferruginous, fissile. ______5 0 2Cl 1 2 44. Sandstone, massive, dark-yellow-red, fine- ' . ------erained 7 0 Siltstone and silty shale, carbonaceous___ 8 0 43. Covered; computed thickness approxi- mately_.______.______6 0 Total.___.._._____.______1,605 7 42. Sandstone,_____-__-_-_--______-__ 1 0 Tuktu formation 41. Covered; computed thickness approxi- T^n M mately ____-___-___-- 5 0 * ne tyPe section ot the Killik tongue (pi. 48, column 40. Sandstone, massive, rusty-brown, fine- 5) was measured along the east bank of the Killik River grained...._-______.______8 0 between lat 68°52' N. and 68°55' N. The section is 39. Covered; computed thickness approxi- exposed in a series of discontinuous ledges and cutbanks QO o m.ff y ------on fae north flank of Kurupa anticline in strata that 38. Sandstone, massive, dark-yellow-red, fine- ^ . grained-.-. 10 0 "ip 13 to 15 N. Quaternary terrace deposits cover 37. Silty shale, ferruginous______l 0 parts of the section. The exposed parts of the section 36. Coal __-___---_-__-_--__-_--_------3 8 were measured. As horizontal and vertical control are 35. Sandstone, shaly-bedded, fine-grained - 2 0 good) the compute(j thickness for the covered intervals ' .,, ------should be accurate to within 10 percent. Details of 33. Siltstone and sandstone---__-_-_---_--- 16 0 ^ 32. Silty shale______- --_ 2 0 tne section are described in Detterman, Bickel, and 31. Coal-_------_------1 0 Gryc (1963, p. 249). 30. Siltstone, thin to heavy bedded, salt-and- Age and correlation The age of the nonmarine- pepper to dark-yellow-red, silty shale, , , , . ,, -r^-n-i - ± -U j ± and sandstone; fine grained .. 23 0 marginal strata of the Killik tongue cannot be deter- 29. Coal___--_------2 0 mined precisely from fauna; however, it can be ascer- 28. Siltstone and sandstone------28 0 tained indirectly from fossils in the underlying Tuktu 27. Silty shale _ _-____-__ __- __ 2 0 formation, and in the overlying Ninuluk formation. 26. Sandstone, massive, salt-and-pepper to One collection of invertebrate fossils was obtained from dark-yellow-red, fine-grained; weathers ,, -i^-n-i - mi. i j -j i-fi j i. brown; clean, ripple marked. 30 0 the Kllllk tonSue- The P^ecypods were identified by 25. Covered, coal float; computed thickness Imlay as Unw sp., a long-ranging, brackish- to fresh- approximately -__-___.______-__-__ 2 0 water pelecypod of no value for correlation. 24. Siltstone, silty shale, and sandstone ._- 23 0 Fossils from beds of the Tuktu are correlated by 23. Covered, silty shale, and coal float; com- T , /,nm\ -..u ^.u -JJT AIU- e T^ ^.u puted thickness approximately-- 12 0 Imla^ (1961 ) Wlth the middle Albian °f Eur°P6 ' theS6 22. Sandstone, siltstone, and silty shale -_ 20 0 include the following diagnostic forms: Inoceramus 2i. Silty shale______--_-____-_--______- 6 0 anglicus Woods, Panope? elongatissima (McLearn), En- 20. Covered; computed thickness approxi- tolium utukokensis Imlay, Tancredia kurupana Imlay, mately.______6 0 and the ammonite Cleoniceras (Neosaynellat) whitting- 19. Sandstone and siltstone-______5 0 tonj inJay. The Cleoniceras sp. may indicate an early 18. Silty shale and siltstone- _ -.__ 12 0 middle Albian age, but the preponderance of fauna! C°mpUted thickness approxi- 18 Q evidence indicates a middle Albian age. In the Killik 16. SastormassVv;; d^rk-yellow-redrnne- R area the marine Ninuluk formation conformably grained, hard; weathers brown_._-__-_ 11 0 overlies the Killik tongue. The Ninuluk contains 15. Siltstone and silty shale_-______5 0 Inoceramus dunveganensis McLearn. This fossil is 14. Sandstone, silty shale, and siltstone _-_ 35 0 present also in the Dun vegan formation of Canada, 378 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

and is no older than Cenomanian. Thus, the Killik and is part of the Verneuilinoides borealis faunal zone." tongue is at least as old as middle Albian and no younger Thus, the microfossils indicate an Albian age for the than Cenomanian; the possibility of its being equivalent beds. All microfossil samples are listed in table 9. hi part to the late Albian can neither be proved or Rocks that are in part equivalent to the Killik tongue disproved. of the Chandler formation in the Killik-Etivluk Rivers Plant fossils are moderately abundant in the beds of region were mapped by C. L. Whittington (oral com­ both the upper and lower parts of the Killik tongue, munication) as Corwin formation (Sable, 1956, p. 2641- particularly in the ironstone beds. Collections from 2643), hi the adjacent area to the north and west. The 10 field samples made from beds in the tongue are shown Corwin formation at the type locality is about 10,000 in table 10; seven were identified by R. W. Brown, three feet thicker than the Chandler formation in the Killik- by F. H. Knowlton, and one by Stewart Lowther. Etivluk Rivers region; however, the Chandler formation The plant fossils are tentatively considered to be Late does become thicker toward the west at a rate of about Cretaceous in age. 25 feet per mile. Lithologically the two formations Forty-four microfossil samples were collected from are very similar, the dominant rock types being shale, shale in the Killik tongue, 30 from the upper part and siltstone, sandstone, conglomerate, and coal. 14 from the lower part; all samples are barren. Thirty- four samples were collected from the marine Tuktu NIAKOGON TONGUE formation that is intertongued with strata of the Killik; Occurrence. The Niakogon tongue is present only in 29 of these samples are fossiliferous. The fossils were the northern part of the Killik-Etivluk Rivers region; identified by H. R. Bergquist, who reported (written it does not crop out south of lat 68°55' N. The tongue communication): "The combined fauna has 20 species is exposed on both flanks of the Awuna syncline, with the best exposures being between the Oolamnagavik TABLE 10. Plant fossils from Killik tongue and Kurupa Rivers. In general the tongue is covered [Identifications: a, R. W. Brown; b, F. H. Knowlton (Smith and Mertie, 1930, p. by terrace gravels between the Killik and Oolamnagavik 222-223); c, Stewart Lowther (unpublished Ph. D. thesis, Michigan Univ.). Field samples 53 ABl 18, 53 ADt 40, 53, 56, Killik River; others, Colville River] and along the Kurupa and Colville Rivers. The type section for the Niakogon tongue is on the Stratigraphic position (from top) east bank of the Killik River, 10 miles upstream from Upper 950 1750 Lower the confluence with the Colville River. The tongue is ft ft about 652 feet thick at the type locality, but is incom­ Field sample (USQS Mesozoic locality) plete because the upper contact with the Seabee forma­ Fossil tion was not seen; however, this sequence of 652 feet is

andAS(7445)372436 probably near the maximum thickness for the unit. The Niakogon- is the upper tongue of the nonmarine AS2429(7742) AS(7744)2432 ADt5356i ADt53i Chandler formation, and is, at least in part, the age ABl1853 ADt4053 ADt5379 ABl5324 ABl5325 equivalent of the marine Ninuluk formation. In addi­ tion to the section at the type locality, two other sec­ tions of the tongue were measured: a 510-foot section Cephalotaxopsis heterophylla on the east bank of the Kurupa River, and a 525-foot intermedia Hollick.... poorly exposed section along the south bank of the b b Cladophlebis Colville River, opposite the mouth of the Awuna River. septentrionalis HolMck...... a a At the type locality the Niakogon tongue overlies a b Coniopteris 40-foot section of marine Ninuluk formation. The con­ burejensis (Zalessky) tact is conformable and well defined; the rusty-weather­ c Ginkgo concima ing yellow-red sandstone, with abundant interbedded b Podozamites coal and bentonite, changes abruptly to a greenish-gray lanceolatus (Lindley and marine fossiliferous sandstone and conglomerate. The Hutton) b a b Ninuluk formation was not mapped west of the Killik Pterophyllumt b River; either it is absent owing to a rapid facies change Sequoia fastigiata TTaar b from marine to nonmarine strata in a westerly direc­ b b tion, or else it was not recognized in the poor exposure a Coniferous wood a on west side of river. The Niakogon is in contact with

i Plate 48, column 5. the Killik tongue throughout the rest of the region. THE KILLIK-ETIVLUK RIVERS REGION 379 The contact between the two tongues is gradational group. On the other hand, the beds may have been and their gross lithologic features are similar; however, eroded before deposition of the Seabee formation, for they can be differentiated, mainly owing to a greater there is a well-developed unconformity between the two amount of bentonite and limonitic material in the stratigraphic units. Much of the Niakogon tongue is Niakogon tongue. overlain by terrace deposits and may have been eroded The Seabee formation overlies the Niakogon tongue prior to the deposition of these terrace deposits. along the Awuna syncline, between the Oolamnagavik The Colville River section (pi 48, column 1) was and Kurupa Rivers. The contact between the two units measured on the south bank of the Colville, about 1}_ is unconformable. The unconformity is well exposed miles upstream from the mouth of the Awuna River. on the east side of a small tributary of the Colville River, The section is on the south flank of the Awuna syncline at lat 68°58' N., long 154°16' W. At this locality, beds in strata that dip 3° N. The upper 90 feet of the in­ of the Seabee formation truncate nearly the complete ferred 525-foot section crops out in one bluff; the com­ Niakogon sequence; elsewhere, the unconformity is not puted thickness may be in error by as much as 15 as well defined. percent. Character and thickness. The nonmarine Niakogon tongue is dominantly a salt-and-pepper to yellow-red, Section of Niakogon tongue along the Colville River, miles highly iron stained conglomeratic sandstone at the upstream from the mouth of the Awuna River Terrace deposits. type locality. The sandstone is fine to coarse grained, Unconformity. thin bedded to massive, and generally well indurated. Feet The conglomeratic constituents are 90 percent chert Niakogon tongue (section incomplete) : and 10 percent white quartz pebbles. The limonitic 5. Clay shale, bentonitic, sandy ______15 4. Sandstone, medium-bedded, medium-gray, fine­ material is mainly concentrated hi the upper part of grained, very friable, bentonitic ______20 the section. Clay and silty shale constitutes about 40 3. Sandstone, thin-bedded, medium-gray, fine­ percent of the section; subordinate constituents in­ grained, bentonitic; contains abundant fossil clude coal, bentonite, siltstone, and ironstone con­ wood and leaves of deciduous trees. ______15 cretions. Plant fossils are common throughout. 2. Siltstone, silty shale, coal, and ironstone concre­ tions; rubble; computed thickness approxi­ The Kurupa River section, 40 miles west of the type mately. ______40 locality, exhibits a slightly different facies of the 1. Covered; computed thickness. ______435 Niakogon tongue. The lower 300 feet of the 510-foot section is dominantly shale with interbedded siltstone TotaL..__-____. 525 and fine- to medium-grained pale-yellow-red sandstone. Upper part, Killik tongue. A few pebbles of chert and white quartz are present in The Kurupa River section (pi. 48, column 2) is the basal sandstone unit; these are the only pebbles in exposed on the east bank of the river, 4 to 6 miles the Kurupa River section. Several limestone beds downstream from the mouth of Heather Creek. The and numerous thin coal and fire clay beds are present beds are exposed in a series of river bluffs on the south in this part of the sequence. flank of the east-plunging Awuna syncline in strata The upper part of the Kurupa River section is that dip 5°, or less, to the north; this is the most predominantly sandstone, thin bedded to massive, complete exposure of the Niakogon tongue in the fine grained, and light yellow red to greenish yellow. Killik-Etivluk Rivers region. The conglomerate present hi the Killik River is missing from this section. Subordinate constituents include Section of Niakogon tongue on the Kurupa River coal, bentonite, ironstone concretions, and a black Terrace deposits. Unconformity. massive limestone or calcilutite. Niakogon tongue (section incomplete): Ft In The Colville River section is inferred to be 525 feet 50. Clay shale and coal rubble; computed thick; it is poorly exposed and only the upper 90 feet thickness approximately ______18 0 crops out hi a cut on the south bank opposite the 49. Sandstone, thin-bedded, pale-yellow, very fine grained; a few thin layers of silt- mouth of the Awuna River. The sequence is com­ stone inter bedded-______5 posed of nearly equal parts of sandstone, siltstone, 48. Sandstone, thin- to medium-bedded, pale- and shale, all of which are bentonitic and poorly con­ yellow, fine-grained; weathers yellow solidated. The sandstone is thin to medium bedded, red; small ironstone concretions.------25 fine grained, and medium gray. Fossil leaves of 47. Limestone, massive; black, weathers yel­ low red. Clay shale, silty shale, silt- deciduous trees are common in the sandstone. stone, and ironstone concretions. The tongue does not appear to thicken in a westerly Rubble. Computed thickness approx­ direction as do some of the older units of the Nanushuk imately _---__-_-_-_-_------_--- 40 380 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4. ALASKA, 1944-53

Niakogon tongue Continued Ft in Niakogon tongue Continued Ft In 46. Sandstone, thin-bedded, pale-green-yel­ 8. Coal-__ __----_----_------_ 8 low, very fine grained, friable, cross- 7. Siltstone------3 0 bedded ; ironstone lenses-_--____-____- 25 0 6. Clay shale with numerous coal beds 3 to 45. Sandstone, massive, pale-yellow-red, very 6 in. thick------25 fine grained_-______,______2 6 5. Siltstone------25 44. Sandstone, shaly-bedded, very fine 4. Siltstone and silty shale rubble in covered grained, very friable, carbonaceous _ _ _ _ 1 3 interval; computed thickness approxi­ 43. Clay shale and coal rubble; computed mately.------40 thickness approximately ______10 0 3. Sandstone, medium-bedded, pale-yellow, 42. Siltstone, laminated, micaceous; beds 1 medium-grained; crossbedded; few chert to 2 in. thick, interbedded with clay- and quartz pebbles.------8 stone; few ironstone concretions and plant fragments.-______10 0 2. Claystone------4 41. Sandstone, massive, pale-greenish-yellow, 1. CoaL __-_------_------_ very fine grained, friable______8 0 40. Siltstone and claystone similar to unit 42, Total..-.--.---__------_-_-_--. 509 10 with 10 in. of bentonitic clay______17 0 Upper part, Killik tongue. 39. Coal______1 0 38. Covered; computed thickness approxi- The type section of the Niakogon tongue (pi. 48, mately______10 0 column 5) was measured on the northeast bank of the 37. Sandstone, thin-bedded to massive, light- Killik River between camps D-June 25-53 and W- yellow-red, very fine to fine-grained, carbonaceous, crossbedded; fossil tree July 12-45. The section is on the south flank of the trunk 2 ft in diameter.______25 0 east-plunging Killik Bend anticline in strata that dip 36. Sandstone, Siltstone, and silty shale rub­ 4° to 5° S. The upper contact was not seen, but the ble; computed thickness approximately _ 25 0 652 feet measured probably represents nearly the total 35. Sandstone, thin-bedded, light-yellow-red, thickness for the tongue. Error in compilation should fine-grained, friable, carbonaceous, crossbedded-______20 0 be less than 10 percent and probably is no greater than 34. Sandstone, massive, light-gray to salt- 5 percent. The detailed description of the section is and-pepper, coarse-grained, weathers given in Detterman, Bickel, and Gryc (1963). moderate yellow red; abundant wood Age and correlation. The nonmarine Niakogon fragments. ______3 0 33. Coal, shaly______-____---__-_-__-__ 6 tongue is barren of megafossils; however, it overlies a 32. Fire clay______8 40-foot section of fossiliferous Ninuluk formation at 31. Siltstone with ironstone concretions____ 10 0 the type locality. Pelecypods from the 40-foot section 30. Coal, shaly______-_-_-__-_. 8 include the diagnostic Inoceramus dunveganensis Mc- 29. Fire clay______.__ 6 Learn and Arctical cf. A. dowlingi McLearn of Ceno- 28. Siltstone---______-____-_-______- 5 0 27. Siltstone, silty shale, and coal rubble; manian age. The fossils were identified by Imlay. computed thickness approximately___- 30 0 The Seabee formation of late Turonian age overlies 26. Siltstone with ironstone concretions 1 to 3 the tongue. Thus, the age of the Niakogon is Late in. in diameter.______6 0 Cretaceous, no older than Cenomanian, and no younger 25. Limestone, massive, pale-yellow-gray____ 1 2 than Turonian. 24. Claystone______3 0 23. Sandstone, medium-bedded, light-yellow- Eight microfossil samples were collected from shale red, medium-grained, crossbedded_ _ _ _ 3 0 beds in this tongue; six are barren. The fossils in the 22. Siltstone, ______5 0 other two samples were identified by H. R. Bergquist, 21. Clay shale and coal rubble; computed who reported (written communication): "A few thickness approximately______35 0 20. Siltstone-______5 0 specimens of Saccammina lathrami Tappan occur in 19. CoaL-_----______--_----____--__ 6 2 of the 8 samples collected from this nonmarine 18. Claystone---______-_-----____- 8 0 tongue. This Foraminifera, however, is a long-ranging, 17. Siltstone, massive, crossbedded. ______1 0 simple arenaceous species of brackish-water environ­ 16. Claystone and ironstone, carbonaceous.- 11 0 ment, and has no significance other than [that it offers] 15. Siltstone, silty shale, and coal, rubble; a suggestion that minor encroachment of lagoonal areas computed thickness approximately __._ 25 0 onto a lowland occurred during Niakogon time, or that 14. Coal.___._.-______.______--.-- 1 10 the area where the samples came from may have been 13. Fire clay______-______-____-______8 adjacent to the mouth of an ancient stream". 12. CoaL______-____----__--_--_-_--_-_-_ 6 11. Limestone------6 The microfossils are of no value in establishing the 10. Clayshale___-____------__--_------2 3 age of the beds, .because the species found occurs in 9. Siltstone------1 0 beds as old as the Fortress Mountain formation and THE KILLIK-ETIVLUK RIVERS REGION 381 as young as the uppermost beds in the Cretaceous Ninuluk formation Continued Feet sequence. 2. Silty shale, clay shale, siltstone, thin-bedded Plant fossils are abundantly preserved in beds of the sandstone; ironstone bed near top; in part rubble; computed thickness approximately. _ _ _ 20 Niakogon tongue; unfortunately only one collection 1. Sandstone, conglomeratic, and pebble conglomer­ was made. This collection was from the upper part ate with 85 percent dark chert, 5 percent white of the type section and was made by Mertie in 1924. quartz, 5 percent green and gray chert, 5 per­ The plants were identified by F. H. Knowlton as cent broken shell material and shale fragments; sandstone hard, greenish gray; abundant fossils. follows (Smith and Mertie, 1930, p. 222): Ginkgo sp. (USGS Mesozoic loc. 24629) _.___.____.__... 10 fragment; Podozamites cf. P. lanceolatus or P. latipinnis; Sequoia cf. S. smidtii Heer; Sequoia cf. S. angusta Total_____. 40 Heer; Pterospermites sp., probably new. Knowlton Upper part, Killik tongue. stated: "In seeking to determine the age of this ma­ terial it is necessary to throw out all but the dicotyledon. Age and correlation. Three megafossil collections According to our present knowledge the dicotyledon were obtained from beds on the east side of the Killik did not appear until middle or later Cretaceous time. River. Two species of pelecypods were identified by Therefore this is presumably not older than middle Imlay from these collections; they were Inoceramus Cretaceous, though it might be later in the Cretaceous". dunveganensis McLearn and Arctical cf. A. dowlingi NINULUK FORMATION McLearn. These mollusks are also found in the mega- Occurrence. The 40-foot section of the Ninuluk fauna in the Chandler River region, which, based on a formation mentioned above is on the east bank of the similarity of species, is correlated with the Dun vegan Killik River, near camp D-June 29-53. The formation formation of British Columbia and Alberta (R. W. may be present on the west bank of the river, although Imlay, written communication); the Dun vegan for­ it has not been found there; it thins rapidly in a south­ mation is of Cenomanian age. westerly direction (Detterman, Bickel, and Gryc, 1963) As the diagnostic fauni is found in the basal beds, it and is believed to be absent in the remainder of the is reasonable to assume that no part of the formation Killik-Etivluk region. The formation is, at least hi is older than Cenomanian; elsewhere hi the Chandler part, the time equivalent of the Niakogon tongue with River region the Ninuluk is unconformably overlain by which it is intertongued. The southwesterly facies the Seabee formation (Detterman, Bickel, and Gryc, change is from marine to nonmarine strata, and the 1963). The Seabee contains a megafauna indicative nonmarine beds are part of the Niakogon tongue. of an early Turonian age. Therefore, the Ninuluk Character and thickness. The formation is composed is entirely of Cenomanian age, but it cannot be deter­ dominantly of sandstone and shale in about equal parts. mined from present field evidence whether the entire The sandstone is medium bedded to massive, fine to stage is present. medium grained, and greenish gray. The basal bed is Fifteen microfossil samples were collected from the conglomeratic with 85 percent of the pebbles being shale beds of the formation; seven are fossiliferous. dark chert, 5 percent green and gray chert, 5 percent The fossils were identified by Bergquist and are listed white quartz, and 5 percent broken shell material and in table 9. Concerning these fossils Bergquist wrote shale fragments. Subordinate constituents include (written communication): "Samples from this formation siltstone and ironstone. The beds are of marine were all collected along the Killik River. Seven of the origin and can be differentiated from the overlying Niakogon tongue; the contact is conformable and well 15 samples collected are fossiliferous, but only one defined, but is not as sharp as it is farther east in the sample is typical of the fossiliferous beds of the for­ Chandler River region (Detterman, Bickel, and Gryc mation, as it has abundant specimens of two species 1963), where the Ninuluk attains its maximum of Foraminfera, Gaudryina irenensis Stelck and Wall and thickness. Trochammina rulherfordi Stelck and Wall. Most of The following section (pi. 48, column 5) of Ninuluk the specimens are flattened but fairly well preserved. formation was measured at camp D-June 29-53, on Another sample has abundant specimens of T. ruther- the east bank of the Killik River. The beds are on the fordi but only a few specimens of 0. irenensis and a north flank of the Awuna syncline and dip 5° S. few fragments of Bathysiphon brosgei Tappan. The Section of Ninuluk formation on the Killik River other samples from the Ninuluk yielded only a few Niakogon tongue. poorly preserved and crushed specimens of Trocham­ Ninuluk formation: Feet 3. Sandstone, medium-bedded to massive, fine- to mina? sp., 0. irenensisf, and Saccammina lathrami medium-grained. ______-__-____.._-_-- 10 Tappan." 382 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

COLVILLE GROUP Quaternary deposits are fluvial and (or) glacial; those Sedimentary rocks of the Colville group probably are of lucustrine and eolian origin are of subordinate size. present along the axial trace of the doubly plunging In some localities deposits of different origin merge so Awuna syncline, between the Oolamnagavik River and intricately as to make their identification virtually Aupuk Creek. The rocks are in an east-trending belt impossible; however, in most of the region it was 10 miles long and 5 miles wide. This particular part of possible to separate the deposits and map them accord­ the Killik-Etivluk Rivers region has not been explored ing to origin. The following four classifications, in order by a field party; the rocks shown as the Colville group of abundance, were used in mapping the Quaternary: were mapped entirely from aerial photographs, and fluviatile deposits, subdivided into high-level terraces while their identity cannot be positively proved, there and alluvium; glacial deposits; lacustrine deposits; and is good reason to believe they belong to the Colville eolian deposits. group. Rocks of the Seabee and Prince Creek forma­ Various thicknesses of unconsolidated deposits mantle tions are known to be present in a structural low along the underlying bedrock. The terrace deposits generally the Awuna syncline just east of the Killik River about 20 to 30 feet thick, but may reach 50 feet in (Detterman, Bickel, and Gryc, 1963), 20 miles east of some places. Although the thickness of alluvium is the inferred occurrence in the Killik-Etivluk region. unknown hi this region, it is probably similar to that As seen on the photographs, an unconformable relation in the Chandler River region where it is known to be exists between beds of the Niakogon tongue and the 110 feet thick at one locality (Detterman, Bickel, and younger rocks, and is particularly evident along the Gryc, 1963). The deposits of glacial origin are several east bank of a small tributary of the Colville River, at hundred feet thick in isolated localities, but in general lat 68°57' N., long 154°16' W. The only known, uncon­ are only a few tens of feet thick. The river has cut formity in that part of the stratigraphic sequence is lake deposits in the Killik River valley at the mountain between the Nanushuk and Colville groups; conse­ front to a depth of at least 80 feet. Sand dunes on quently, the strata overlying the unconformity must top of the lake deposits are as much as 30 feet high. be Colville group. Further evidence for mapping the Colville group at GLACIAL DEPOSITS this locality is obtained from the topographic expression Glaciers formed during the Pleistocene probably of the rocks. The Seabee formation is dominantly a covered about 1,700 square miles of the Killik-Etivluk shale unit in which small streams are deeply entrenched. Rivers region (pi. 49). Well-defined morainal deposits The basal bed of the Tuluvak tongue of the Prince Creek formed by these glaciers cover about 500 square miles; formation is a conglomerate that forms mesas above the an additional 200 square miles along the Etivluk and shale lowlands (Detterman, Bickel, and Gryc, 1963); Nigu Rivers are mapped as undifferentiated glacial both conditions are present in the belt in the Awuna and terrace deposits (pi. 43). The remaining 1,000 syncline. square miles is mapped as bedrock and terrace deposits The limits of the Seabee and Prince Creek formations (pi. 43), but erratics and small patches of possible in the Awuna syncline, between the Oolamnagavik drift indicate that this area or part of this area probably River and Aupuk Creek, coincide with the extreme was glaciated at least once. western boundary of the Colville group south of the In general, glaciation was not as severe in the mapped Colville River. Although the lithologic character of region as it was east of the Killik River, owing partly the two formations hi the Killik-Etivluk Rivers region to the lower altitude of the mountains in the accumu­ is unknown, it can be reasonably assumed that the lation area. The well-defined glacial deposits present rocks are similar to those exposed in the Chandler today are in large part the product of alpine glaciers River region. The Seabee formation is undoubtedly a that probably coalesced locally to form piedmont lobes. shale sequence with a maximum thickness not in excess The older, poorly defined deposits that cover most of of 400 feet. The exposed Tuluvak tongue of the Prince the glaciated parts of the region probably were deposi­ Creek formation is believed to be about 100 feet thick ted by a larger mass of ice; this mass of ice apparently in the Killik-Etivluk region. Only the basal conglomer­ covered most of the mountainous parts of the region, ate is present as cap rock on the hills near the synclinal with the exception of the higher peaks. axis. The well-defined glacial deposits are primarily con­ QUATERNARY SYSTEM fined to the Killik River drainage, because of a large Some of the most extensive deposits in the Killik- and rugged accumulation area. Several small glaciers Etivluk Rivers region are the Quaternary, including are present today hi cirques near the head of Easter those now in the process of formation. About one-third and April Creeks; cirques at the head of the Kurupa of the area was mapped as Quaternary. Most of the River also contain small masses of ice. THE KILLIK-ETIVLUK RIVERS REGION 383 The glaciated parts of the Killik-Etivluk Rivers tok stage (pre-Wisconsin) of glaciation (Detterman, region and the glacial deposits are shown on plate 48. 1953, p. 11) may be present, but cannot be positively The plate does not show fluviatile deposits formed by identified. Deposits of Alapah Mountain (late Wis­ streams issuing from the glaciers, but does show the consin) and Fan Mountain (Recent) (Detterman, glacial lakes, Killik and Kurupa, and the active sand Bowsher and Dutro, 1958, p. 54-57) may be present dune areas in the Killik River valley. Plate 43 also also in the mountain valleys near the headwaters of shows glacial deposits, but, because it is primarily the major rivers. designed to show the bedrock geology of the region, From the limited glacial studies made in northern the only glacial material that is shown is in areas where Alaska it is impossible to correlate positively the ad­ it completely obscures the bedrock. vances with the major episodes in the United States. In order to show the source areas for some of the Little is known concerning the weathering character­ deposits that are present in the Killik-Etivluk region istics produced by semiarid Arctic climate as compared and to present a more complete glacial history of the to morainal weathering in more moderate climates. region, the glacial map includes some areas that are However, on the basis of a tentative correlation with not shown on plate 43. The areas of sculpturing and glaciations in southern Alaska that have been dated erratics shown on plate 48 are above the level of definite by carbon-14 analysis, Karlstrom (1957, p. 73-74) glacial moraine; the upper contact is the level to which dated the Anaktuvuk stage as Nebraskan, the Itkillik the valley was filled with ice. The glaciers formed as Illinoian and Sangamon, and the Echooka as Wis­ typical U-shaped valleys with hanging tributaries, consin. truncated spurs, and scour marks on the bedrock. The authors believe the Itkillik glaciation should The broad valleys and low rounded hills show fewer be correlated with the early Wisconsin rather than with signs of sculpturing, but erratics are common to abun­ the Illinoian because physical characteristics of de­ dant and give conclusive proof that the parts of the, posits of the Echooka and Itkillik advances are very region in which they occur were covered by ice at similar; both are relatively fresh and only slightly least once. altered by weathering. Deposits of the Anaktuvuk The part of the mountains mapped as being ice-free glaciation are highly weathered and obviously much was above the general level of the glaciers; however, it older. The Anaktuvuk glaciation probably should be does show evidence of glacial sculpturing in the form of correlated as pre-Wisconsin rather than with any cirques, cols, aretes, and faceted spires. Many of the specific episode, for the only evidence for correlation tributary streams leading into the major river valleys are physical characteristics of the deposits. undoubtedly contained small glaciers at one time or another, but the amount of sculpturing is minor as ANAKTUVUK GLACIATION compared to that in the main valleys and these tribu­ Morainal deposits and till of the Anaktuvuk glacia­ taries have been included, in part, with the ice-free tion are present on the Killik River, just upstream areas. from the junction with the Okpikruak River, and along The direction of movement of ice is self evident for the Etivluk and Nigu Rivers from Howard Pass area the most part. Near the passes between the present- to within about 18 miles of the Colville River. The day north and south drainage, the direction is some­ morainal character of the deposits along the Etivluk what more conjectural, particularly in the Howard Pass and Nigu Rivers is considerably altered by terrace area where some evidence indicates that the ice came deposits that, at least in part, postdate the Anaktuvuk from the Noatak River drainage to the south of the glaciation. In addition to the areas mentioned, the mapped area. area between the Killik and Etivluk Rivers from the The mass of debris dropped by the glaciers in the north front of the Brooks Range almost to the latitude of mapped region has diverted some streams into new the Tuktu escarpment probably was covered with ice of channels and changed the direction of flow of others. the Anaktuvuk glaciation. The evidence for this postula- The exact channels of former streams can only be tion is the erratic boulders of rock types that are tentatively identified, but the wide stream valleys now present only within the mountains and the low rounded occupied by small modern streams show evidence that hills of debris that appear to be weathered hummocky some of the streams were formerly much larger. The till. A few of these erratics are scattered throughout changes in stream direction are plotted on plate 48. this area, but the main concentration is in the present Evidence for three stages of glaciation, Anaktuvuk stream valleys where possibly they have been moved (pre-Wisconsin), and Itkillik and Echooka (early from farther south by the streams. Wisconsin) (Detterman, 1953, p. 11-12), is present The till of the Anaktuvuk glaciation is extremely in the Killik-Etivluk Rivers region. The Sagavanirk- weathered, lateral and end moraines are not identi- 384 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 fiable, the drainage is well-integrated, and most of the ITKILLIK GLACIATION kettle lakes are filled. The amount of surficial modi­ Till of the Itkillik glaciation is present along the fication of the till, the presence of a weathered rind on Killik River where it extends for a distance of 30 miles the erratics, and the partial covering of the till by north of the Brooks Range, and at the headwaters of the terrace deposits all indicate that the Anaktuvuk glaeia- Kurupa and Oolamnagavik Rivers. The till forms a tion represents an extremely old period of glociation. small lobe that extends about 10 miles north of Kurupa Till of the Anaktuvuk glaciation extends farther Lake. This stage of glaciation has not been positively north than any of the moraines of more recent advances; identified in the Etivluk River drainage, but some of the northermost limit is about 35 miles from the north the valley scupturing and erratics along the Etivluk and front of the Brooks Range and about 70 to 80 miles Nigu Rivers may have been caused by Itkillik glaciation. from the crest of the Brooks Range. Thus, the Anaktu­ The till sheet and moraines of this glaciation are vuk glaciation was apparently more extensive than any more extensive along the Killik River than they are in of the subsequent glaciations and may have formed the Kurupa-Oolamnagavik Rivers area, because of the an ice sheet over most of the area between the Killik larger accumulation area tributary to the Killik River. and Etivluk Rivers. An ice sheet of sufficient thickness Moraines occur along the valley walls of the Killik to cover the area in front of the mountains to the lati­ River as much as 1,200 feet above the present river. tude of the Tuktu escarpment would probably require The ice was apparently thicker than 1,200 feet, for a greater thickness of ice than is indicated by the upper the upper limit of valley sculpturing at the mountain limit of valley sculpturing in the mountains. Most front is about 1,800 to 2,000 feet above the present of the criques, cols, aretes, and spires probably were river level at altitudes of 3,800 to 4,000 feet. The depth formed by more recent glaciations, or at least were of ice in the accumulation area near the headwaters of considerably modified by them. the Killik River, as determined by valley sculpturing, The accumulation area required to supply the amount was about 1,200 to 1,400 feet, with the upper limit of ice necessary to form an ice sheet of this magnitude of sculpturing at an altitude of about 5, 200 feet. A would be greater than the area available at the head­ gradient of about 23 feet per mile on the upper surface waters of the present north-flowing rivers. Numerous of the ice is indicated for the Killik River glacier. erratics of granite are present in the Howard Pass area. Till of the Itkillik glaciation is relatively fresh. The Smith and Mertie (1930, p. 245) believed they were end moraine consists of an arcuate zone of slightly derived from the granite in the Noatak River area, modified knob-and-kettle topography in which lakes 30 miles south of Howard Pass, and had been trans­ are present, undrained depressions are abundant, and ported by glaciers to the Howard Pass area. The drainage is poorly integrated. Six arcuate recessional higher mountains in the Noatak River area could have moraines 1 to 3 miles apart are present behind the end been part of the accumulation area for an ice sheet as moraine in the Killik valley. The time lapse between extensive as would be required to cover the area north the formation of the end and the recessional moraines of the Brooks Range. was relatively short, because there is no apparent difference in the amount of weathering or surficial The lack of till of the Itkillik glaciation in the Etiv­ modification. Lateral moraines are well developed luk River area can be considered, for several reasons, along the valley walls at about 700 to 900 feet above the as added proof that the main source for the Anaktuvuk river, and scattered glacial debris is found as much as glaciation was in the higher mountains of the Noatak 1,200 feet above the river. Lateral moraines for each River area. The mountains near the headwaters of of the successive stages of recessional moraine occur at the Killik River are about 2,500 feet higher than the slightly lower elevations. ones near Howard Pass, and the greatest mass of Itkillik The southernmost recessional moraine, at camp D, till is along the Killik River, whereas the Etivluk June 8-53, dammed the river and formed a large glacial River is apparently free of Itkillik till; therefore, the lake that extended up the valley as far as Easter Creek. logical conclusion seems to be that the lower mountains Ground moraine occurs in this part of the valley along of the Howard Pass area could not have supplied the the margins of the lake deposit. The knob-and-kettle amount of ice necessary for the Anaktuvuk glaciation topography is only slightly modified and has many lakes if they could not supply enough ice for a less extensive on the moraine. Numerous lakes that are vestigial Itkillik glaciation. One other reason for the more remnantsof the glacial lake are present on the lake depo sit. extensive Anatkuvuk glaciation along the Etivluk Ice-marginal stream channels are present on both River is the broad Howard Pass that would give access east and west walls of the Killik valley. Those on the to glaciers from the south; the passes at the headwaters east side are perhaps better defined and more persistent of the Killik and Nigu Rivers are more restricted. than the ones on the west side, and are cut to a depth of THE KILLIK-ETIVLTJK RIVERS REGION 385 80 to 90 feet through solid bedrock in numerous places. the largest deposits of Echooka till but does not contain The ice marginal channels occur only in the area of any identifiable till of the Itkillik glaciation. recessional moraines, and probably were formed by the Evidence of minor glacial advances that postdate increased melt water during the general retreat of the the Echooka glaciation probably can be found near the valley glacier. These channels are 300 to 500 feet cirques and in the small valleys near the headwaters of above the present river level. the Killik and Nigu Rivers; no fieldwork has been done The Itkillik moraines in the Kurupa Lake area are in that part of the region. Small rock moraines a short relatively fresh and only slightly altered, but still not as distance in front of the cirque glaciers near the head­ fresh as the Itkillik stage in the Killik River valley. waters of the Kurupa River probably represent minor These morainal remnants may be older than the Itkillik advances that occurred within the last several hundred glaciation, perhaps as old as the Sagavanirktok glacia- years. tion. As present field evidence is inconclusive, the till is FLUVTATILE DEPOSITS correlated as Itkillik glaciation, with the possibility The most extensive surficial deposits are of fluviatile that it may be as old as the Sagavanirktok. origin and include material that is definitely glacio- ECHOOKA GLACIATION fluviatile and possible some deposits that are of glacial The Echooka glaciation was a relatively minor ad­ origin, but the latter are so weathered that positive identi­ vance of Alpine-valley glacier type that was confined to fication is impossible with present field information. the major river valleys and did not reach the north front The deposits are divided into high-level terrace of the Brooks Range. The main glacial deposits are deposits and alluvium. Those mapped as Quaternary confined to the valleys of the Nigu and Killik Rivers terrace gravels or high-level terraces are about 250 feet and of Easter and April Creeks, tributaries of the Killik above the present stream level. A system of low-level River. Several small glaciers also occupied parts of the terraces, as much as 30 feet above the streams, is present Kurupa River valley and its tributaries, notably Out- on most of the rivers; for the purpose of this report these wash Creek. The till in the Kurupa River system is low terrace deposits are included with the alluvium. the farthest north deposit of the Echooka glaciation in the mapped area, but the actual distance from its HIGH-LEVEL TERRACE DEPOSITS source area is much less than that of the deposits along High-level terrace gravels cover an area of about the Killik and Nigu Rivers. 1,150 square miles, and are present along all the major The deposits of this glaciation are relatively thin, streams in the Killik-Etivluk Rivers region. The main probably not more than 100 feet thick at the maximum concentration of terrace gravel is in the western part of and generally not more than 50 feet thick. The source the region, along the Etivluk River and its tributaries, areas were apparently in the higher mountains at the and along the Colville River in the northern part of the headwaters of the Killik, Nigu and Kurupa Rivers, and area. A similar, but less extensive deposit is present the ice probably did not reach the upper limit of valley along the lower 40 miles of the Killik River. Some of sculpturing, so the glaciers of the Echooka glaciation the deposit along the upper part of the Etivluk River is probably did not greatly alter the valley form as estab­ of glacial origin, as attested by numerous lakes and by lished by earlier glacial advances. the uneven topography apparently of weathered mo­ raine. The deposits mapped as undifferentiated terrace Moraines and till of the Echooka glaciation are fresh and glacial deposits extend from Howard Pass to near and show little surficial modification due to weathering. the junction of the East Fork with the Etivluk River. The knob-and-kettle topography is only slightly altered; the drainage is poorly integrated, and undrained In general, the terrace deposits between the Killik depressions and lakes are numerous. The end moraines and Etivluk Rivers can be divided into two belts that are not well developed and are missing in many places were probably deposited contemporaneously. The where the present rivers have washed out the till. southern and more extensive belt lies between the north front of the Brooks Range and the Tuktu escarpment; The difference in the amount of surficial weathering it is particularly well developed in the lowlands under­ of the moraine is in general much less between the lain by shale of the Torok formation adjacent to the Echooka and Itkillik glaciations than it is between the Tuktu escarpment. The northern belt is best developed Itkillik and Anaktuvuk glaciations. The similarity of along the Colville River, and is present along all streams the Echooka to the Itkillik may suggest that the Echo- oka was another recessional phase of the Itkillik glacia­ for a distance of 5 to 10 miles south of the Colville River. tion similar to the six recessional moraines mapped on The areas covered by terrace gravels are almost uni­ the Killik River. The evidence to refute this assump­ formly regions of low relief. Lakes commonly dot the tion may be in the Nigu River valley, which contains surface, and streams are entrenched in the gravel or 386 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 have cut through it to expose bedrock. The gravel rivers; on some of the smaller streams near the moun­ unconformably overlies rocks that are Mississippian to tains, the active zone may include 50 percent of the Cretaceous in age. flood plain. Oxbow lakes, cutoff meanders, abandoned The terraces are composed dominantly of well- channel scars, and low terraces are common features of rounded slightly roller-shaped cobbles 4 to 12 inches in the inactive fossil flood-plain zone. The Killik River length, with a considerable amount of smaller rock has five distinct terrace levels, each level being about fragments. Pebbles and silt are locally abundant, but 5 feet higher than the preceding. Some of the levels in general are not important constituents of the terrace are being destroyed by lateral erosion at the present time. deposits. Gray quartzite, white quartz, and colored The alluvial deposits consist of debris from all rock chert constitute the bulk of the deposits; also included types found along the stream. Most rock fragments are limonitic quartzite, graywacke, and quartz-pebble are waterworn and well rounded except for the material conglomerate. Limestone, where present, is extremely recently added from cutbank exposures of bedrock. weathered. The deposits are light to medium gray Most of the rock fragments range in size from 2 to 8 with a buff to rusty-brown weathered zone. inches, with silt and small pebbles forming lenticular The terrace gravels were probably formed contem­ deposits in lagoons and along the downstream end poraneously with glaciation of the region during of bars. Large glacial erratics of conglomeratic quartz­ Pleistocene time. The earlier, more extensive glacial ite are common on the Killik River, wherever the advances probably account for most of the glacio- river cuts one of the arcuate recessional moraines. fluviatile deposits. Some of the gravel may be The top of the low terraces in the stream valleys prob­ remnants of a veneer on a pediment surface that predates ably marks the maximum postglacial aggradation of the Pleistocene; it was probably formed in late the streams, and the numerous levels either are the Tertiary time. The field information on surficial result of minor adjustments during the present stage deposits is not sufficiently detailed to allow determina­ of degradation or were formed when the river cut tion of the extent of any possible pediment surface. through the successive recessional moraines upstream The pediment, if present, would be confined to the from the low terraces and released large quantities of southern belt of terrace deposits. debris and water. The terrace along the Etivluk River appears to LACUSTRINE DEPOSITS overlie, in part, the glacial till of the Anaktuvuk A glacial lake, approximately 29 miles long, once glaciation; both the till and the terrace are weathered, occupied the Killik River valley between the junction but the relation suggests that the terrace may in part of Easter Creek with the Killik River and camp D- postdate the Anaktuvuk glaciation and that it was June 8-53. Numerous vestigial ponds and lakes from formed as an outwash plain. 100 feet to iyz miles in width are present in the area The high-level gravel terrace deposits are about today as remnants of the former lake. The lake was 150-250 feet above the streams throughout most of the apparently dammed by the southernmost recessional region, and their gradient is similar to that of the moraine that crosses the valley at camp D June 8 53. present streams. Near the mountain front the stream This recessional moraine was formed during the retreat gradient is greater than that of the terrace, and the of the Itkillik glaciation. difference in elevation between the two becomes less. The glacial lake area today is one of sand, silt, muck, In Howard Pass the Etivluk River is entrenched in the and peat through which the Killik is cutting a wide terrace. On the other hand, outwash gravel forming the terrace on the west side of the Killik River lies about 500-700 feet above the present river. The Killik valley was extensively glaciated during the Itkillik glaciation, and the valley was scoured to a greater depth than were the other river valleys. Till of the Echooka stage of glaciation did not reach the mountain front; consequently, outwash from this stage of glaciation probably did not affect the formation of the high-level terrace. ALLUVIUM Those deposits mapped as Quaternary alluvium include all material on the flood plains of the modern streams. The active zone generally occupies less than FIGURE 63. Horizontal view of Killik River cutbank in glacial lake deposit on the 10 percent of the total flood-plain area on the larger upper Killik River. Photograph by R. L. Detterman. THE KILLIK-ETIVLUK RIVERS REGION 387

channel. The river has cut about 80 feet through The peat does not have the strong organic odor this deposit (figs. 63 and 64) at a point 1% miles south common to most peat deposits; in fact, it is quite dry of camp D-June 2-53. The exposed section consists and burns readily. The layers contain fragments of of alternating layers of silt and peat that have the ap­ wood that appear to be willow or alder and other pearance of varves. The layers range in thickness species of plants similar to those growing in the region from % to 3 inches, but any given pair of silt and peat today. layers are generally of about equal thickness. The ECHLIAN DEPOSITS amount of time that elapsed during the formation of The Killik River is wide and sluggish where it one of these pairs cannot definitely be stated from present meanders through the glacial lake deposit; during most field information; it is quite possible, however, that of the year it carries very little water. The meandering a set represents a yearly cycle of sedimentation. course of the river exposes a maximum of the lake de­ The peat layers are commonly oxidized to an orange posit to wind action. The silt is blown away and leaves red as the result of weathering. The silt is light the sand to form dunes. The sand dunes give the gray to buff, and at the base of the exposed section general appearance of a miniature desert. The dunes there is a loosely consolidated sand that appears to occupy the same general area as the glacial lake; the be admixed with gray rock flour. most numerous and the largest are in the area between

FIGUEE 64. Vertical view of sand dune area on glacial lakebed in upper Killik River area. Photograph by U.S. Navy. 388 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Aniakvik and Akmalik Creeks near the north front of structures as flow phenomena, vesicle or amygdule elon­ the Brooks Range. The prevailing winds are from the gation and alinement, and variolitic and related struc­ south and most of the cutbanks have "blow cuts" that tures were not observed either in hand specimen or slope up toward the north; however, a few of the "blow thin section. cuts" slope in the opposite direction. The largest igneous mass in the mapped region is The dunes are 10 to 30 feet high and strongly cross- along Flora and Fauna Creeks and several miles south bedded. The sand grains are commonly "frosted," of camp M-July 24-49 at Howard Pass. It has been and larger rock fragments show the effects of wind mapped for a distance of 18 miles and is from 2 to 5 scour and faceting. Dead and dry stumps of willow miles across. Neither the western nor eastern boun­ groves that were killed by the sand are partly exposed daries of the body were mapped. The mass probably on many of the dunes. Some of the dunes have a was intruded along a major fault zone. The rocks were thin vegetation cover, but the ones closest to the river previously mapped as lavas (Smith and Mertie, 1930, are being actively eroded and generally are barren. p. 258-263), but in the 1949 fieldwork no evidence to Nearly all the "blow outs" are formed on south- support this origin was found. The petrographic prop­ facing river bluffs, and the active part is generally less erties of these rocks are similar to those of sills and than 1,000 feet long and 150 feet wide. Many were dikes in the rest of the mapped region. Megascopic formerly larger, and the fact that the down-wind ends study shows the rocks to be gabbros and basalts and to are covered with a thin layer of vegetation at present range in color from dark green to black. They are fine and are no longer active may indicate a more arid or to medium grained, weather dark red brown, and effer­ colder condition in the late Pleistocene. vesce with hydrochloric acid. The effervescence is Much of the glacial lake deposit in the Killik valley probably due to the alteration of the feldspars rather consists of silt of a buff color that is similar to loess than to carbonate from associated rocks. deposits. The thermokarst lakes on the surface of Metamorphism has taken place to a minor extent the terrace and the poorly integrated streams indicate along the contacts of the igneous body with the Wachs- that the high-level terrace, particularly along the muth limestone and the Siksikpuk and Shublik forma­ Colville River, is probably covered by loess similar to tions. Along the northern contact with the Wachsmuth the deposit in the Chandler River region (Detterman, limestone, the limestone is marmarized for 25 to 30 feet. Bickel, and Gryc, 1963). The southern belt of terrace Along the southern contact of the igneous rocks and deposits does not have the numerous thermokarst Siksikpuk and Shublik formations the shale has been lakes, but one drained lake on the west bank of the metamorphosed to slate with well-developed north- Kurupa River (fig. 58), at lat 68°46' N., long 155°14' dipping cleavage. W., exposed 15 feet of silt and muck in the outlet A second large igneous mass in the mapped region is drainage channel, which had been cut only a few years at the head of Fay Creek and 5 miles west of camp previous to the time of examination. The deposit M-May 28-49 and the Etivluk River. This body is had all the characteristics of a loess deposit. approximately 6 square miles in area and is thought to The gravel terrace in the Howard Pass area is be intruded along large thrust faults. In many places covered by a silt deposit that may be in part of wind­ limestone of the Kayak and Wachsmuth formations blown and in part of fluvial origin. The Pass does not has been assimilated by the gabbro and basalt, and in appear to have been glaciated during the Itkillik and the field it was extremely difficult to distinguish the Echooka glaciations, but considerable melt water must limestone from the replacing igneous rocks because in have been diverted through the pass during that time. many instances features such as bedding and sedimen­ tary texture of the limestone have been preserved in the IGNEOUS ROCKS igneous rocks. OCCURRENCE AND DISTRIBUTION The third large igneous body forms Kikiktat Moun­ Three large areas and many scattered small outcrops tain 2 miles south of camp C-June 22-50 and between of finely crystalline igneous rocks of the basalt-gabbro the Killik River and Immaitchiak Creek. It is appar­ clan are present in the Killik-Etivluk Rivers region. ently in conformable contact with a sequence of gray- These igneous bodies lie within rocks of Kayak through wacke and conglomerate of the Tiglukpuk formation. Tiglukpuk formations. They are believed to be sills, The upper contact was not seen. No mineralized but possibly some are plugs. zones in the adjacent rock were seen. In talus blocks, Field evidence indicated a concordant relation of the all gradations of alteration between true crystalline igneous bodies to the enclosing rock. The possibility igneous rock and slightly altered graywacke are found. that some of the bodies formed as flows was considered, The remaining igneous rocks occur as numerous but no conclusive evidence was seen. Such marginal small sills or plugs in the southern foothills section. THE KILLIK-ETIVLUK RIVERS REGION, 389

These smaller bodies are usually more resistant than myrmekite. Calcite, celadonite, delessitic chlorite, and various the surrounding country rock and form sharp hogbacks zeolites have been identified as amygdule fillings. Although and hillocks. In some places the contact between the rhombic pyroxene, olivine, and pyrogenic amphibole may be expected to occur in rocks of this type, these minerals were not igneous and sedimentary rocks was exposed. There is present in any of the thin sections studied. little metamorphism of the enclosing rocks near the As suggested above, the dolerite has been subject to alteration contact, except for a charred baked appearance with which in some rocks has effected the complete replacement of locally colors such as black, red, and orange in the almost all original mineral constituents. In extreme examples weathered rock near the contact. The greatest thick­ the rock consists of carbonate (usually calcite) pseudomorphs after plagioclase which are set in a groundmass consisting almost ness of the contact zone was 20 feet, but in most places entirely of several species of chlorite. Other feldspar alteration it was less than 10 feet. products include prehnite, white mica, several zeolites, and ag­ gregates of clinozoisite and albite (saussurite). It is of interest PETROLOGY to note, however, that in the thin sections studied plagioclase has Eberlein, who made the petrographic study of the generally survived the alteration better than pyroxene, and the igneous rocks reported: development of zeolites and saussurite through the breakdown of the feldspar does not appear to be common. In hand specimen these mafic igneous rocks are typically Under the microscope, augite generally shows some degree of equigranular, medium to fine grained, and compact. Their alteration to acicular actinolite of the uralite variety, with as­ color ranges from dusky yellow green to dark greenish gray. sociated disseminated magnetite. Where alteration has been These features make it difficult to distinguish some of these rocks more or less complete, the pyroxene may be changed to chlorite in the field from medium- to fine-grained graywacke-type sedi­ (commonly penninite) and various serpentine minerals. Chlorite mentary rocks with which they are in contact. An igneous also occurs locally in interstitial areas between relatively fresh origin of most of these rocks is shown, however, by a well-de­ plagioclase and augite. In these places it probably has formed veloped igneous texture (often diabasic) and the local presence either as a primary mineral or through the breakdown of glass. of amygdules. Ilmenite, if originally present, may disappear entirely during A suite of 16 thin sections, prepared from representative alteration and be represented by clusters of magnetite grains specimens collected from igneous rocks in the Imnaitchiak Creek and sphene. Under less drastic alteration, ilmenite alters to and Etivluk Rivers areas, were studied by means of the petro­ leucoxene. graphic microscope. The following general comments pertain The above assemblages and relationships suggest that altera­ to the petrology of the igneous rocks as a whole and are based tion is principally related to deuteric or paulopost processes. It on information obtained from this thin-section study and on the should be pointed out that with the development of good ophitic megascopic study of these and other specimens both in the texture, these igneous rocks are perhaps better termed diabase. laboratory and in the field. Transitions to gabbro occur and are manifest by an increase in Most of these rocks are dolerite or microgabbro. Plagioclase grain size, the development of coarse ophitic texture, and a and clinopyroxene are the dominant pyrogenic minerals. Al­ strong tendency for the clinopyroxene to exhibit 'striations' though some of the rocks are ideally fresh, most are altered to a parallel to (100) (diallage structure) and (001) (salite structure). greater or lesser degree. Such transitions appear to be local, however, and for the most The texture of the dolerite is variable. Normally it is micro- part are restricted to small areas within the larger dolerite bodies. ophitic, due to the partial or complete enclosure of unoriented All these types are perhaps best considered under the general idiomorphic plagioclase microlites by typically anhedral clino­ term of dolerite or microgabbro. pyroxene or its alteration products. The texture of some of the With the introduction of subordinate amounts of late quartz, specimens is similar to the groundmass texture of some basalts there are also local transitions to rocks with quartz dolerite in which small grains of pyroxene are crowded between lathlike affinites. The quartz may be interstitial or intergrown with plagioclase crystals, to the exclusion of any glass or its alteration plagioclase (myrmekite). The occurrence of quartz in these products. rocks may reflect a magma somewhat oversaturated with respect Mineralogically the dolerite is simple, although the propor­ to silica (tholeiitic), but it is more likely related to the assimila­ tions of constituent minerals apparently vary considerably. tion of silica by dolerite during intrusion into chert, cherty silt- The common feldspar is andesine, but a range in plagioclase stone, and other more or less siliceous sedimentary rocks. composition from oligoclase (An-s?) to labradorite (An6o) has been observed among the thin sections studied. Feldspar zoning STRUCTURE generally is not well developed. Where present, it is almost all The major geologic structural features of the Killik- of the progressive type. In most of the specimens plagioclase Etivluk Rivers region are grouped into three structural is more abundant than clinopyroxene and in some is present belts, which roughly coincide with the physiographic almost to the exclusion of the pyrobole. provinces of the region, as follows: the Brooks Range Although augite is the common pyrogenic ferromagnesian mineral, it locally is a titaniferous variety (titanaugite). The province and the southern and the northern sections augite is frequently schillerized parallel to (001), and some of it of the Arctic foothills province. Although the struc­ shows a distinctive herringbone structure owing to additional ture of the area is relatively complex, a major pattern twinning on (100). Among the several species of accessory opaque of east-trending fold axes and large fault systems is minerals that may be present are magnetite, ilmenite, and titan- apparent. magnetite. Ilmenite, often in the form of characteristic skeletal BROOKS RANGE PROVINCE crystals, is common in coarser grained dolerite and may be re­ constituted as sphene and (or) leucoxene. Quartz, if present, is The structure of the Brooks Range province is char­ interstitial and may be intergrown with plagioclase in the form of acterized by large thrust faults and overturned folds. 390 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

The outstanding structural features in this province body that was intruded possibly along one of the are two major thrust faults that extend for miles along fault zones lies near the center of this area. The mafic the northern front of the mountains (pi. 43). Imbri­ body is in contact with Mississippian and Triassic cate thrust faults are also apparent, as are large over­ rocks along its northern border, and with Permian and turned and recumbent folds in the Kanayut and Hunt Triassic rocks along the southern edge. Although the Fork formations in the south-central part of the mapped upper Mississippian, Permian, and Triassic rocks are area. The prevailing dip of the rocks is south, but pro­ highly faulted north of Flora and Fauna Creeks, the gressively younger rocks are exposed to the north owing Devonian and Lower Mississippian appear to dip to these thrust faults and overturned folds. beneath the younger rocks there. The longest thrust fault occurs along the northern At the northern edge of this area the Kanayut forma­ edge of the Kanayut conglomerate and extends the tion in Kavaksurak, Kivliktort, and Isikut Mountains entire length an airline distance of about 78 miles appears to be part of an isoclinal anticline overturned of the mapped region. This thrust is believed to have to the north. The Hunt Fork shale is present in the occurred in the axial zone of an overturned anticline center of this anticline on the east side of the Etivluk whose south limb was thrust northward onto the River, but, owing either to west plunge or to stretch younger rocks in the north limb. Between Kutchiak- faulting, is absent on the west side of the Etivluk ruak River and Outwash Creek, the Kanayut and River. Kayak formations appear to have overridden the SOUTHERN FOOTHILLS SECTION younger rocks for 1 to 3 miles. The structure of the southern section of the Arctic The other conspicuous thrust fault is along the north foothills province is characterized by isoclinal folds, front of the main Lisburne group belt at the mountain isolated infolded synclines of Okpikruak and Fortress front. This fault extends from east of the Killik River Mountain formations, thrust faults, and high-angle westward to Kutchiakruak River, a distance of more reverse faults. In this section the rocks are more than 30 miles. The Lisburne group is deformed into crushed and shattered by folding and faulting than a large overturned anticline, with the south limb thrust those in the Brooks Range province; many areas are so over the north limb at a high angle. A transverse fault complex structurally that it is impossible to differentiate sharply offsets the Lisburne belt at Kurupa Lake. the formations. Associated with these complexly Several other transverse faults are present west of folded and faulted areas are many small mafic intrusions Kurupa Lake; the largest offset along these faults has (15 square feet to 2 square miles). been mapped 6 miles west of Kurupa Lake on a fork In the southern foothills section there are three of Kurupa River. Here the easterly fault block is major thrust faults that bring Paleozoic rocks as old as thickened as a result of imbricate thrust faults. The Late Devonian to the surface. These three faults are westerly fault block is narrow, and just west of Kutchi­ believed to have formed within overturned anticlines akruak River it is cut off where the Kayak shale has whose south limbs were thrust over the north limbs been thrust over it. From this point westward to the onto younger rocks. Nigu River, the thrust fault lies along the northern The southernmost thrust fault begins east of Ivotuk edge of the belt of Kayak shale. Between the Nigu Creek (about 1 % miles east of camp E-July 20-50) and River and Fay Creek, near camp M-May 28-49, on the extends 20 miles west to the Nigu River. Along this Etivluk River, the faulting is more complex; the Lis­ same fault between Ivotuk and Kutchaurak Creek, the burne group is again present only in a few scattered Lisburne group is thrust over Mesozoic rocks. Between mounds and hillocks. Outwash Creek and the Nigu River, the Lisburne is In the upper Killik, Kurupa, and Kutchiakruak thought to be absent at the surface and the Siksikpuk Rivers valleys the Paleozoic rocks have been deformed formation to be thrust over undifferentiated Paleozoic into large appressed overturned and recumbent folds and Mesozoic and Lower Cretaceous rocks. From the broken by stretch and imbricate thrust faults. In Nigu River to the west side of Etivluk River near general, these fault planes dip 20° to 60° S. and are 1 Tukuto Creek camp M-June 11-49, the thrust is to 15 miles in length. inferred along several isolated outcrops of Devonian, Near Howard Pass, in the southwestern part of the Mississippian, Permian, and mafic igneous rocks, mapped region, rocks ranging in age from Devonian which crop out through a gravel mantle. Mafic through Triassic are exposed in an area characterized intrusive bodies occur at several localities along this by considerable faulting and a regional south dip. thrust fault and probably came in along this zone of Along the southern edge of this area the Devonian weakness. rocks are thrust over Mississippian and Permian rocks The second thrust fault is approximately 25 miles and most of the Mississippian is absent. A large mafic long and extends from Iteriak Creek at lat 68°31' N. THE KILLIK-ETIVLUK RIVERS REGION 391 and long 155°50' W. slightly northwest to camp M- NORTHERN FOOTHILLS SECTION June 14-49, and five miles west of the Etivluk River The northern foothills section of the Arctic Foothills into Puvakrat Ridge. From Iteriak Creek west to province is hi general an area of simple folds in rocks about lat 68°33' N., long 155°10' W., undifferentiated of the Nanushuk and Colville groups. The southern Permian and Triassic rocks are thrust onto Triassic boundary of the northern foothills section coincides and Jurassic rocks. From this location to the western with the Tuktu escarpment, which rises abruptly above extremity of the fault, the Lisburne group is in thrust the lowland to the south that is underlain by Torok fault contact with Mesozoic rocks. formation. The third and northernmost fault occurs along the Five major structural features are present in the north front of Lisburne Ridge, 4 miles northwest of northern foothills section: the Oolamnagavik and Etivluk River camp M- June 14-49. This fault Awuna synclines and the Kurupa, Aupuk, and Killik extends for 7 miles to the west boundary of the mapped Bend anticlines. The two synclines are broad, open region. Here the Lisburne group is thrust over Meso­ folds that are uncomplicated by faults or drag folds. zoic rocks. Several north-trending transverse faults The Aupuk and Killik Bend anticlines are believed to cut Lisburne Ridge and displace the limestone. The be parts of the same structure, but this cannot be largest transverse fault is about 5 miles west of the proved. The Kurupa anticline is a major structure Etivluk River. that extends both east and west beyond the boundaries A thrust fault, inferred largely by interpretation from of the mapped region. The anticlines are asymmetri­ aerial photographs, extends westward along lat 68°41' N., cal, the north flank being the steeper. Low-angle from the Oolamnagavik River area to the Etivluk axial thrust faults, high-angle reverse faults, and River. This fault and associated complex, tightly oblique slip faults are present locally in the anticlines. folded structural features are within a belt of shale, Drag folding is commonly associated with the faulting sandstone, and conglomerate of the Fortress Mountain and folding. Killik Bend anticline is locally overturned formation. Another fault, which may account for the to the north in the Killik Bend area. The folds are isolated exposure of Triassic rocks near the confluence parts of regional structural features that are 72 to 200 of Travelair Creek and the Oolamnagavik River, is miles in length; they extend beyond both the east and interpreted to lie between the East Fork of the Oolam­ west boundaries of the mapped area. nagavik River and the Kurupa River, and about 3 miles The strike of the folds is about N. 80° W. between south of the previously mentioned fault. the Killik and the Kurupa Rivers; between the Kurupa A number of isolated synclines in rocks of Fortress River and the west boundary of the mapped area the Mountain and Okpikruak formations lie between the strike is about N. 60° W. The Tuktu escarpment is north front of the Brooks Range and the belt of Fortress roughly parallel to these axial trends. Mountain formation along lat 68°41' N. These Northward deflections of the axial trends from their synclines are all west trending, and suggest a major regional strike form an undulatory pattern and are west-trending synclinorium within this belt. present on all five features in such a manner as to sug­ The structure of the low featureless belt of Torok gest deep transverse regional structures. One such formation, including the Torok and Fortress Mountain feature is indicated by the northward swing of the axes formations undifferentiated, between the belt of Fortress between the Killik and Oolamnagavik Rivers; the strike Mountain formation and the Tuktu escarpment is of the transverse trend is approximately N. 25° E. poorly known because the uniform nonresistant thick Another northward swing of the axes occurs between shale sequence affords little topographic expression the Oolamnagavik and Kurupa Rivers; the strike of and few good outcrops. Stream bank outcrops along this transverse trend is about N. 50° W. Minor cross the Oolamnagavik River and Heather Creek show some faulting of the anticlines observed in surface outcrops small complex folds and minor faults. Most of the is probably a result of stress set up along these trans­ beds in the southern part of this belt dip southward, verse trends. A pair of small oblique slip faults on the and a few widely scattered outcrops in the northern Kurupa anticline 6 to 8 miles west of the Kurupa River part close to the Tuktu escarpment show north-dipping show this feature. beds. On the basis of this meager evidence, a west- trending anticline in the Torok formation between the OOI^AMNAGAVTK RIVER STRUCTURAL, HIGH Oolamnagavik and Kurupa Rivers may be inferred. A north-trending structural high just east of the Along Kucher Creek exposures of the Torok formation Oolamnagavik River is reflected in the folds of the are more extensive; an anticline about 2 miles south of southern foothills section of the Arctic Foothills the Tuktu escarpment and a syncline 2 to 4 miles province and the Brooks Range province, as well as in farther south have been mapped. the five folds of the northern foothills section. In 392 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

both the southern foothills and the Brooks Range, the A high-angle normal fault, in part delineated by rocks exposed across this line of culmination are older photo-interpretation, cuts the anticlinal axial trace than those adjacent to it; detailed information is not near Heather Creek; it is 6 miles long, and the maximum available on most of the folds, but they probably are displacement is at the west end. Throw is probably doubly plunging. The anticlines in the northern about 600 to 800 feet. An axial thrust fault is indi­ foothills are definitely doubly plunging. cated between Quandary Creek and the Killik River. The age of the Oolamnagavik River structural high Throw cannot be determined because the bedding cannot be determined from present field evidence; it traces are not well enough exposed. A structurally probably started to form in pre-Nanushuk time and complex zone is exposed near the axial plane on the may predate the deposition of the Fortress Mountain east bank of the Killik River in beds of the Tuktu and formation, because all post-Okpikruak sediments have Chandler formations. Three small high-angle reverse a greater proportion of coarse-grained clastic rocks faults occur south of the axial plane, and three north near the line of culmination. A change in lithologic of the axial plane. Small east-plunging drag folds, character is not readily apparent in pre-Okpikruak some of which are overturned to the south, are as­ formation rocks overlying the high. Uplift along the sociated with the faults. The lateral extent of these high continued at least through Nanushuk time, for folds and faults cannot be determined, but they may be these rocks are exposed in doubly plunging folds. part of the same complex zone that is mapped on the east bank of the Oolamnagavik River, for some faulting KURUPA ANTICLINE is evident between the two rivers. A pair of oblique The Kurupa anticline is a major feature about 64 slip faults cut the axial plane in the area 6 to 8 miles miles long and 8 to 9 miles wide; it extends beyond west of the Kurupa River. These faults are about 2 both the eastern and western boundaries of the mapped miles long and converge toward the south to form a area where the beds flatten out and merge with mono- triangular fault block. Movement of the block was clinally north-dipping strata. Three reversals of plunge toward the north. The east fault strikes east and the occur in the mapped area, with a structural high near west fault strikes N. 12° W. Horizontal displacement the point where the axis crosses the north-trending line along these oblique slip faults probably does not ex­ of culmination along the Oolamnagavik River; a ceed 200 feet. The small west-plunging anticline secondary high is present near the Killik River, and and syncline near the western fault may be the result another near the Kurupa River. The anticline has of compression during faulting. Two other oblique closure on the three structural highs, but sufficient data faults cut the anticlinal axial trace; one is 4 miles west for structure contouring is lacking and thus the exact of the Oolamnagavik River, and the other is 7 miles amount of closure is unknown. The maximum closure west of the Killik River. They are less than 2 miles is probably no greater than 1,000 feet. The economic long and strike N. 45° W.; the east sides of both have possibilities of any closure are materially affected by moved north. The displacement along them is minor. the breaching of reservoir beds by the rivers. The strata are breached into the Tuktu formation on all ATJPTJK AND KTLLTK BEND ANTICLINES structural highs, and not more than 400 feet of the The Aupuk and Killik Bend anticlines are parts of a Tuktu remains. These beds of the Tuktu formation major anticlinal trend that extends at least 200 miles are dominantly a graywacke sandstone facies with inter- across northern Alaska. This anticlinal trend is one bedded siltstone, shale, and lenticular conglomerate; of the major structural features of the northern foot­ they may be potential reservoir rocks. The Tuktu hills section, and may be associated with a deep-seated formation is underlain by at least 4,000 to 6,000 feet fault or zone of persistent uplift. of shale of the Torok formation that would be of little The Aupuk and Killik Bend anticlines are mapped value as reservoir rock, although some sandy facies on plate 43 as two features, although the writers believe may be present locally. that they are probably parts of one anticline. The The Kurupa anticline is an asymmetrical structure; easternmost outcrops exposing the axial plane of the the beds on the north flank have dips 10° to 20° steeper Aupuk anticline and the westernmost outcrops showing than those on the south flank. The maximum ob­ the axial plane of the Killik Bend anticline are on the served dip of strata near the axis is 45°; in general the south bank of the Colville River 3 miles upstream and dip is much less than that, the average in the axial zone 4 miles downstream, respectively, from the mouth of being 20° to 25°. Structural relief between Kurupa Aupuk Creek. Outcrop observations or any other anticline and Awuna syncline is about 4,500 feet, but evidence that would delimit the position of the axial probably does not exceed 400 feet between the anticline plane in this 7-mile interval are indefinite. The and Oolamnagavik syncline. attitude of the bedding can be measured in one bluff, THE KILLIK-ETIVLUK RIVERS REGION 393 at camp D-July 4-53, in this interval; the dip is low, tact between the upper and lower parts of the Killik generally less than 10°, and the strike is northwest. tongue northward from a point on the Kurupa River Crossbedding in the rocks somewhat complicates the 2 miles south of the Colville River. The contact is at picture, but 7 of the 9 dip-and-strike readings taken in the base of a conglomerate bed that is fairly well defined the vicinity of this bluff indicate the presence of a and persistent. The beds at the surface over the high northwest-trending axial plane between the ends of would be about 500 feet above the Tuktu-Chandler the two anticlines. The remainder of the area on the formations contact; a total of 1,400 to 1,500 feet of south side of the Colville River in the 7-mile interval Tuktu and Chandler formations underlies the high. is covered by surficial deposits and tundra that effec­ A longitudinal fault was mapped 1,000 feet north of tively conceal any evidence that might give a clue to the anticlinal axis near the gas seeps, 2 miles upstream the structure. from the mouth of Aupuk Creek. A shear zone with Dip and strike readings taken on strata in two bluffs anomalous dips is exposed in a bluff on the Colville on the north side of the Colville River 2 miles upstream River 2 miles downstream from camp C-August 14-46. from camp D-July 4-53 indicate that the axial plane This shear zone may be a westward extension of the of the Aupuk anticline extends across the Colville fault; if it is, the fault would cut the axial trace of the River in a northeasterly direction and does not join Aupuk anticline west of the eastern high. The amount the Killik Bend anticline. These dips and strikes, of movement along the fault cannot be determined however, may be a reflection of the east-trending fault from available field evidence. The two gas seeps are that is just north of the trace of the axial plane in the apparently in the fault zone and on the high. The vicinity of the Aupuk gas seeps, rather than of the axial presence of the gas may be interpreted as evidence that plane. the anticline has closure on the eastern high. One objective of the 1950 Geological Survey field Intense folding and faulting was apparently con­ party in the Killik-Etivluk Rivers region was to make a fined to the Killik Bend area for the Killik Bend anti­ structure-contour map of the Aupuk anticline. The cline is structurally more complex than other anticlines map was not made because not enough data was in the northern foothills section of the mapped region. obtained, owing to the paucity of bedrock exposures It is overturned to the north, and a thrust fault, nu­ along the Colville River and small tributaries and to merous high-angle reverse faults, and drag folds are the surficial mantle of tundra and Quaternary terrace localized in the axial zone. The faulted zone is con­ gravels that conceals any bedding traces in the area fined to an area about 1 mile wide, and the greatest adjacent to the Colville valley. displacement is near the axial trace. The exact amount The Aupuk anticline is believed by the authors, on of throw cannot be determined, but it is probably no the basis of limited outcrop data, to have two small more than 200 feet, and generally less than that on the structural highs, one about 1 mile west of the Kurupa north and south sides of the disturbed zone. Most of River and the other on the Colville River 5 miles the faults and folds are confined to beds of the Tuktu upstream from the mouth of Aupuk Creek. West formation and to the basal 400 feet of the Killik tongue plunge of the western high cannot be proved; the beds of the Chandler formation. may be closed against the faults known to be present East of the complex zone at Killik Bend the anticline about 1 mile north of camp T-Aug. 23-47 on the plunges east, and west of Killik Bend it plunges slightly Colville River, but the amount of closure is unknown. west. The east plunge is about 90 feet per mile, and It is estimated that approximately 2,000 feet of the west plunge is perhap's as much as 30 feet per mile. Chandler and Tuktu formations underlies the western The structural high coincides with the complex zone, high; the estimate is based upon projection of the and approximately 700 to 800 feet of Tuktu formation stratigraphic sequence as measured along the Kurupa is present at the crest. River on the north flank of Kurupa anticline, and does GEOLOGIC HISTORY not take into account the normal northward gradation The geology of the Killik-Etivluk Rivers region is to shale or any thinning of the stratigraphic units. insufficiently known to provide the basis for a detailed The south flank of the Aupuk anticline, at the western analysis of its history, but some of the broader phases high, may have about 3,000 feet of structural relief. of the sequence and nature of the events in this region The eastern high is also poorly defined and closure can be summarized. Many of the statements in the cannot be proved. The Aupuk anticline apparently has following eight paragraphs, however, are subject to an overall west plunge between the eastern and western reevaluation; they should serve only as guides for highs; consequently the eastern high is about 500 to future investigations. 600 feet lower stratigraphically than the western high. During Paleozoic time the probable source area for This difference was determined by projecting the con­ the sediments was to the north. Deposition was 394 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 probably almost continuous from Late Devonian the present Brooks Range, flanked by a west-trending through Mississippian time. The Upper Devonian geosyncline in the present sourthern foothills province limestone and the Hunt Fork shale are believed to have area, is suggested. The Okpikruak rocks were deposited been deposited in a marine environment. The contact in the geosyncline during this time, and in places may between these formations was not seen. The Hunt rest with disconformity on Jurassic rocks but in other Fork shale is apparently gradational into the overlying places may lie on Triassic or Permian rocks. The Kanayut formation which is predominantly a non- environment fluctuated between shallow marine and marine quartzitic sandstone and conglomerate sequence. littoral. The Kayak shale is a marine unit that overlies the Marine shale, graywacke sandstone, and conglom­ Kanayut conglomerate. The contact may be grada­ erate, locally in excess of 10,000 feet thick, were de­ tional, although it is suggested (Bowsher and Dutro, posited in the geosyncline during Early and Middle 1957) that in the Shainin Lake area about 100 miles Albian time; these rocks are divided into the Fortress east of the Killik River, the contact is disconformable. Mountain, Torok, and Tuktu formations. This thick The Kayak shale appears to be conformable with the marine sequence was deposited on a differentially overlying marine limestone of the Lisburne group, eroded surface, for the Fortress Mountain formation although it has not been established whether the unconformably overlies rocks of Permian (?) to Early contact in this region is disconformable or gradational. Cretaceous age. The clastic and bioclastic nature of the rocks in the small The region has been generally emergent since the northernmost exposures of the Lisburne group in this deposition of the Tuktu formation in middle Albian region perhaps indicate that these rocks were derived time. Minor transgressions and regressions of the sea from a northern source area and that deposition took occurred during this time of general emergence, but the place in a sea that may have deepened southward. rocks are dominantly nonmarine-marginal in character No rocks of Pennsylvanian age have been identified and consist of about 4,000 feet of conglomerate, sand­ in this region, and the hiatus may represent a time of stone, coal, siltstone, and shale. quiescence and nondeposition or of some uplift and A period of igneous activity, probably in late or post- erosion. The events in Permian time in this region are Okpikruak time, formed sills, plugs, and perhaps some poorly understood, and the distribution of the rocks flows of basalt. are not known. Apparently deposition here during Two periods of folding followed the intense Late Permian time was in a marine environment. Jurassic and Early Cretaceous orogeny. The first An unconformity is present between the upper period of folding, which was probably more severe Paleozoic rocks and the Triassic rocks. Apparently the than the second, occurred at the end of Cenomanian next significant deposition took place in Middle or time; rocks of middle to late Turonian age unconform­ Late Triassic time, and the meager evidence available ably overlie the Cenomanian strata. The folded late gives little information on events during the time Cretaceous beds indicate that the last period of folding between the Permian and Middle Triassic. Presumably to affect the region probably took place during Tertiary there was no significant orogeny at this time, as there time. The present Brooks Range and many of the is no known angular relation between the Siksikpuk structural features in the foothills section probably and Shublik formations in this region. It was likely a date from the Tertiary orogeny; however, only minor time of relative quiet in a marine or littoral environ­ folding took place in the northern part of the region at ment, and it was during this time that at least part of this time. The uplift along the positive or transverse the phosphatic deposits were formed. The abundantly high that strikes northward in the Oolamnagavik area fossiliferous Triassic limestone, chert, and shale, and probably began no later than pre-Fortress Mountain also some beds of oil shale were deposited in a time; it continued through Cretaceous or Tertiary time. quiescent marine environment. Little can be deduced ECONOMIC GEOLOGY from this region about events during Jurassic time. Probably orogenic movement began in a source area to PETROLEUM POSSIBILITIES the south, and some sandy and pebble-cobble con­ No oil seepages have been reported within the Killik- glomerate as well as fine clastic material were deposited, Etivluk Rivers region; however, two seepages, believed probably in a rapidly shifting shallow marine and to be of natural gas, are present in valley-floor lakes littoral environment. adjacent to the Colville River and about \% miles west The events in Late Jurassic and Early Cretaceous of the mouth of Aupuk Creek. Oil shale, probably time in this region are not easily determined. It seems part of the Triassic Shublik formation, occurs in the clear that orogenic activity continued at least through southern foothills section, but the thickness of the beds Okpikruak time; a mountain area in or just south of and their areal extent are unknown. Owing to faults, THE KILLIK-ETIVLUK RIVERS REGION 395

complex structure, and apparent paucity of favorable the mountain front is suggested. The absence of lime­ reservoir beds, this area in general does not appear to stone or of any identifiable Mississippian strata above offer attractive possibilities for petroleum exploration. the Middle Devonian chert conglomerate sequence in No seismic work or drilling has been done in this region, Topagoruk test well 1 and the presence of a marked and little information can be gathered from the rela­ angular unconformity between this sequence and red tively poor and isolated outcrops of bedrock. Thus, beds of Permian(?) age (Collins, 1958) further compli­ interpretations of subsurface structure and stratigraphy cate the problem of the northward extent of the Lis­ are conjectural, and subsurface exploration will be burne group. Conceivably the Lisburne group might required before an adequate evaluation of the petroleum offer good petroleum reservoir possibilities within the possibilities of this region can be made. foothills province of the mapped region, but, until some indication of its depth, lateral extent, lithology, and PALEOZOIC ROCKS structure can be obtained, it would be a nebulous The Hunt Fork shale, Kanayut conglomerate, and drilling target. Kayak shale formations are exposed within the Brooks The unnamed Carboniferous and Permian formation Range province in the mapped region, and in the out­ and the Siksikpuk formation of Permian age are present crops appear to be unfavorable petroleum reservoir in the southern foothills section and in the mountains rocks; they are essentially nonporous and impermeable near Howard Pass. Some limestone and clean, moder­ sandstone and conglomerate that are in part metamor­ ately porous quartz sandstone and conglomerate, all of phosed to quartzite, slate, and slaty shale. The which might have reservoir potential, are included in lithologic character of these formations at depth and these formations, but much of the section is chert, northward from the mountain front in this region is siltstone, and shale. In the mapped region, these for­ unknown. If, as has been postulated, the source area mations are exposed only in the southern part of the for these sediments was to the north near the present southern foothills section, and their structure and Arctic coast, some change in lithology is to be expected; lithology farther north are unknown. The only ob­ however, chert conglomerate, shale, and claystone of servations of Permian rocks north of the outcrop belt Middle (or Lower?) Devonian age was encountered at a are those from Topagoruk test well 1, where a Permian depth of 10,040 to 10,503 feet in Topagoruk test well 1 sequence has been identified between 9,380 and 10,040 (Collins, 1958), approximately 160 miles north of the feet. The rocks in this interval are siliceous or cal­ mountain front. This conglomerate sequence from the careous sandstone (in part dolomitic), siltstone, con­ well is similar in age and lithology to the Kanayut con­ glomerate, and claystone, with some shale (Collins, glomerate in this region, and is the only proven occur­ 1958). Thus, a northward change to a more clastic rence of Devonian rocks north of the Brooks Range, and less cherty Permian section between the southern for none of the other wells were drilled deep enough to foothills and Topagoruk test well 1 is indicated. A penetrate Devonian rocks and none are known to crop sandstone bed at 9,420 feet in the well has a porosity of out. No section that can be correlated with the Kayak 6.61 to 6.9 percent and is impermeable to air (Collins, shale was recognized in Topagoruk test well 1. 1958, p. 282). Presumably most of the foothills prov­ Where exposed in the Brooks Range province, these ince in the mapped region is underlain, generally at Paleozoic formations are structurally complex, although considerable depth, by the Permian formations, and at depth in the Foothills province the complexity may some potential reservoir beds may be included. decrease northward from the mountains; furthermore, TRIASSIC AND LOWER CRETACEOUS ROCKS they are probably below a depth of at least 10,000 feet The Triassic Shublik formation, the Jurassic Tigluk- in the northern foothills section of this region. Pre­ puk formation, and the Lower Cretaceous Okpikruak sumably the Kanayut conglomerate, at least, underlies formation, which crop out in the southern foothills all the Foothills province in the mapped region. section of this region, are not well defined. The The Lisburne group was not studied in detail in the complex structures formed by these rocks, the abundant Killik-Etivluk Rivers region, but within the Brooks and poorly delimited faults, and the generally poor Range it appears to be structurally and lithologically reservoir characteristics of the chert, shale, siltstone, unfavorable for petroleum accumulation. Only a few dense limestone, and some tightly cemented sandstone thin zones of the limestone exposed near Kurupa Lake and nonporous graywacke units, make these formations show any visible porosity. The Lisburne group in its in their outcrop area unfavorable for petroleum accumu­ northernmost exposures on the East Fork of the Etivluk lation. On the basis of present knowledge of these and the Oolamnagavik Rivers is more dolomitic, formations elsewhere in the foothills province of vuggy, and clastic than it is in the mountains, and the northern Alaska, they show little, if any, evidence of petro­ possibility that the porosity increases northward from leum potential. Three samples of sandstone that were 396 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

collected on the east side of Imnaitchiak Creek between three samples were collected for testing. Two from camps C-June 16-50 and C-June 22-50 have a maxi­ Smith Mountain have 0.8 and 3.4 percent porosity and mum of 2.85 percent porosity and are impermeable. are virtually impermeable. One from along the Kurupa Oil shale occurs in the southern foothills section of the River about 27 miles south of its mouth has 7.8 percent Killik-Etivluk region, but it does not appear to be porosity, which is probably about the maxiumum in this abundant and has been found chiefly as float. Howard region. The subsurface extent and lithologic character (Stoney, 1900, p. 69) noted that the Eskimos gathered of the Fortress Mountain formation north of its surface pieces of this float for fuel near the upper Etivluk outcrops is unknown; the coarse elastics may have River; the field party in 1949 found leathery oil shale shale equivalents. pebbles along ridges formed by the Okpikruak forma­ The Torok formation is predominantly shale, with tion west of camp M-June 6-49. Pebbles and cobbles minor amounts of siltstone, graywacke sandstone, and of oil shale are also known to occur in conglomerate of conglomeratic sandstone. None of the coarser clastic the Okpikruak formation in the upper Utukok and Kuna beds are known to have visible porosity. Rivers area 100 miles to the west of the Etivluk River. Only general correlations between the Lower Creta­ Oil shale has been found in place with Triassic rocks ceous formations in the Killik-Etivluk Rivers region and in the Kiruktagiak-Okpikruak Rivers area 20 to 30 those in Topagoruk test well 1 have been suggested miles east of the Killik River. A weathered and (Gryc and others, 1956, p. 214). Much more sandstone largely vegetation-covered conglomerate of the Okpi­ and conglomerate is present in the outcrops of these kruak formation may be the source of some of the oil- formations than is found in their time equivalents in shale float in the Killik-Etivluk region. In view, the Topagoruk well. Facies changes from sandstone however, of the relatively poor outcrops in much of to shale and pinch-outs of sandstone and conglomerate this region and of the known Triassic oil shale near beds in a northerly direction, forming potential strati- Imnaitchiak Creek and farther east, it is reasonable graphic traps, may be inferred. The only known to assume that more oil shale than is apparent is present indication of petroleum in this sequence of rocks in in the Shublik formation in the mapped region. either of the above-mentioned regions is a slightly oil The Tiglukpuk formation is poorly exposed in the stained sandstone at 5,960 to 5,987 feet in the well. mapped region, and an evaluation of the reservoir This sandstone is impermeable, and a formation test potential of this formation is necessarily indefinite. showed no oil or gas (Collins, 1958, p. 269). Beds of graywacke-type sandstone, conglomeratic sandstone, and conglomerate, many of which are 10 LOWER AND UPPER CRETACEOUS ROCKS feet or more thick, and limestone coquina are included NANUSHUK GROUP in the Tiglukpuk formation. The depth to this forma­ The Tuktu formation includes sandstone, siltstone, tion, its thickness, lithologic character, and distribution silty shale, conglomerate, and clay shale, listed in ap­ in the subsurface in the mapped region are unknown. proximate order of abundance, and is dominantly In outcrop, the coarser clastic units mentioned above marine. In general the porosity of the sandstone and showed little visible porosity. In Topagoruk test well conglomerate, as determined visually, is low. Labora­ 1, a section of Jurassic rocks consisting mainly of marine tory determinations on 25 samples show an average of clay shale with a minor amount of siltstone and glauco- 8.67 percent porosity and a range from 2.05 to 15.9 nite sandstone are present at a depth of 6,600 to 8,640 percent; nine samples were found to be impermeable. feet (Collins, 1958). A representative porosity-sampling program was not The Okpikruak formation includes some beds of attempted many of the 25 samples were selected micaceous graywacke-type sandstone, grit, and pebble because of their visible porosity, and these porosity and conglomerate. In the outcrops these clastic rocks permeability values are nearly a maximum; thus the showed little visible porosity, and two samples collected Tuktu formation does not give promise of good reservoir from either the Tiglukpuk or the Okpikruak formation beds. Winnowed phases of this formation would have show 2.09 and 1.23 percent porosity. Nothing is more favorable porosity and permeability, but the known of the subsurface character or extent of this location of such rocks is difficult to predict. formation in the mapped region. Possible changes in thickness and facies of the Tuktu The Fortress Mountain formation of Early Creta­ formation should be considered in evaluating its petro­ ceous age includes a large proportion of graywacke-type leum possibilities. The amount of sandstone and sandstone and conglomerate in addition to siltstone and conglomerate apparently decreases to the north in this shale. All the coarse clastic rocks are poorly sorted area, perhaps owing to actual thinning of the formation and "dirty," and show little or no visible porosity. or, more likely, to a facies change from coarse clastic to Because of the generally poor visible porosity, only silty and clayey rocks. Lacking knowledge of sub- THE KILLIK-ETIVLUK RIVERS REGION 397 surface control, this change cannot be evaluated of 11.10 percent, and range from 4.5 to 20.6 percent. quantitatively. All the samples that were collected along the lower The unit of Tuktu formation and lower part of the Kurupa River (table 11) have higher than average Killik tongue undifferentiated, is limited, as far as porosity. Two of these samples that have 12.4 and known, to the northwestern part of the mapped region 15.69 percent porosity show respectively 4.6 and 27.0 and is exposed only in the Kurupa anticline and in the millidarcys permeability. westernmost part of the Oolamnagavik syncline. It The Niakogon tongue of Late Cretaceous age is a is a mapping unit made up of marine sequences similar dominantly nonmarine unit composed of sandstone, in type to those of the Tuktu formation, and of se­ conglomerate, siltstone, and shale. Within this area quences of chiefly nonmarine siltstone, shale, sandstone, it is limited to the Awuna syncline, and this structural and conglomerate of the lower part of the Killik tongue. setting precludes it from consideration as a petroleum The subsurface extent and thickness of this unit is prospect. Seven samples from three widely separated unknown, but presumably it is present in the western localities have an average porosity of 10.06 percent and part of the Aupuk anticline within about 1,000 feet of range from 5.44 and 14.6 percent. the surface. Some of the sandstone in this unit has The Ninuluk formation of Late Cretaceous age is fair porosity; four samples that were tested average chiefly a marine formation containing siltstone, silty 13.5 percent and range from 9.4 to 19.2 percent. Per­ and clayey shale, sandstone in part conglomeratic, and meability was not determined. If proper structural a minor amount of bentonite. It has been identified conditions were determined to exist in the western only along the Killik River in the Awuna syncline, and part of the Aupuk anticline, this unit would be worthy on the north side of the Colville River northeast of the of subsurface exploration. mouth of the Killik River in the Killik Bend anticline. The lower part of the Killik tongue of Early Cre­ Within this area this unit is apparently not in a favor­ taceous age is chiefly a nonmarine unit that intertongues able structural position to form a petroleum reservoir. with the Tuktu formation in the northwestern part Some of the sandstone beds may have fair porosity. of this region. Siltstone, silty and clayey shale, sand­ The only sample tested, which is from the Killik Bend stone, conglomeratic sandstone, conglomerate, and coal, anticline, has 13.2 percent porosity. in approximate order of abundance, are included. The COLVILLE GROUP coarser clastic rocks are a dirty graywacke type that The Seabee and Prince Creek formations of Late have generally low porosity, although some fairly Cretaceous age were not examined in the field in this porous rocks are present. The 38 samples tested have area. Their presence in the Awuna syncline between average porosity of 8.04 percent, and range form 1.54 Aupuk Creek and Oolamnagavik River was interpreted to 21.0 percent. from aerial photographs. Owing to their structural The lower part of the Killik tongue is exposed positions, they have no apparent petroleum potential. throughout the length of the Kurupa and Killik Bend anticlines and is nearly or entirely breached. In the TABLE 11. Porosity-permeability of selected samples Aupuk anticline, as far as known, only this tongue is Poros­ exposed in the axial zone, and probably a minimum Field sample Formation ity Permeability Location (per­ (millidarcy) thickness of 500 feet is present on the crest of the cent) anticline. Thus, structurally as well as lithologically, 50 ARe 73..... Siksikpuk, 2.85 Imperme­ Imnaitchiak Creek. the petroleum possibilities of this formation are quite Shubiik and able. Tiglukpuk. limited. 50 ARe 88.. Siksikpuk, Shub­ 2.09 ..... do. . . Do. lik, Tiglukpuk, The upper part of the Killik tongue is a dominantly and Okpikrauk. 50 ARe 95.. -...do ...... 1.23 ..... do...... Do. nonmarine unit, and its lithologic characteristics and 3.4 ..do Etivluk River, Smith tain. Mtn. stratigraphic relationships are very similar to those of 49 ALac 5 .....do ...... 8 ... ..do . .... Do. 46 ACh99_...... do...... 7.8 Kurupa River, middle the lower part. This unit occurs in the center of the 45 AWa 56 Tuktu--- 7.7 Killik River, lower. 45 AKr 72...... do ...... 6.0 Do. Oolamnagavik syncline between the Kurupa and 46 ACh53-._- ... ..do ...... 12.2 Oolamnagavik River, lower. Oolamnagavik Rivers, and in the Awuna syncline. It 46ACh60--.- .....do. 8.3 Do. 46ACh67--_- -do ...... 9.0 Do. has been completely eroded from the anticlines in the 46ACh81_.._ ..do ...... 3.1 Do. 46 AChlll... do...... 11.0 Kurupa River, lower. mapped region, unless possibly it is present in the 46AChl25-._ . do 14.4 Do. 46 ACh 131..- ..do ...... - 10.6 Do. axial zone of the extreme western end of the Aupuk 46 ACh 188.. . do...... 7.1 Colville River, Killik Bend. anticline; it therefore appears to have no significance 46 ATh 115-.- do ...... 8.8 Kurupa River, lower. 46 ATh 120.. _ ... ..do...... 7.2 Do. in this region as a petroleum reservoir. 46 ATh 215.. . do ...... - 3.2 Colville-Oolamnagavik Rivers. Seventeen rock samples from the upper part of the 47 ATh 17.. . . do ...... 13.5 N. Colville-Etivluk Rivers. Killik tongue that were tested have an average porosity 47 ATh 23...... do...... 14.8 Do. 398 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

TABLE 11. Porosity-permeability of selected samples Con. TABLE 11. Porosity-permeability of selected samples Con.

Poros­ Poros­ Field sample Formation ity Permeability Location Field sample Formation ity Permeability Location (per­ (millidarcy) (per­ (millidarcy) cent) cent)

47 ATh28...... do ...... 10.9 S. Colville-Etivluk 47 AZ565-...... 14.6 Rivers. tongue. Rivers. 47ATh28a._. -do...... 11.3 Do. 47ATb56--..- 11.6 Do. 50 AE 126..... do 2.05 50AE-123...... do...... 5.44 able. able. 50AE127 .....do ...... 3.71 ..... do...... Do. 50 AE 128a...... do 8.16 do Do. 50AE128b... do ______9.54 do Do. 50 AE 128c.... do 8.20 _ do ..... Do. 50 AE 129...... do...... 7.62 .....do Do. STRUCTURE 50 AE 131...... do ...... 2.56 ..... do _____ Do. 47ATh35.... 11.5 part of the Kucher Creek. The anticlines, synclines, faults, and associated Killik tongue, undifferenti- structural and stratigraphic traps within the Killik- ated. 47 ATh37-..- .....do ...... 9.4 Do. Etivluk Rivers region afford a number of conditions 47 ATh38.___ ..... do...... 14.2 Do. 47 AZ 612a...... do...... 19.2 that could be favorable for petroleum accumulation. 45 AWa 57 . 6.8 Killik tongue. The present knowledge of the structure and the struc- 45 AWa70.... 7.2 Do. 45 AKr 84 ...... do ...... 9.2 Do. tural-stratigraphic features within this region is inade­ 45 AKr 85 ... ..do ...... 10.6 Do. 46ACh71...... do...... 5.3 quate to make more than a general evaluation of their lower. 46ACh77...... do ...... 3.8 Do. effect on oil accumulation. 46AChl48...... do ...... 9.3 Rivers. The structural and topographic setting of the Brooks 46 AChl51...... do ...... 6.5 Do. 46AChl59... ..do 15.0 Range province are unfavorable for oil accumulation Creek. 46AChl69.._ .....do ...... 6.2 Do. of any consequence, and would be inhospitable for 46AChl76...... do ...... 6.5 Creek. most types of exploration. The structure within this 46AThllOa.. do 8.6 46AThll4.._ ..... do .. 21.0 Do. province is complex. The intensity of deformation and 46AThl53...... do ...... 4.7 Do. 46AThl55...... do ..... - 4.1 the resulting partial metamorphism of the formations Rivers. 46AThl69.__ .....do...... 5.3 appear to be incompatible with oil accumulation. Creek. 46AThl87... do 6.2 Do. The structure of the southern foothills section, on 46AThl97...... do ...... 9.9 Colville River, Killik Bend. the basis of present knowledge, appears to be generally 46ATh221.._ .....do...... 12.6 Rivers. unfavorable for petroleum accumulation. Most of the 46 ATh232...... do...... 11.3 Do. 47ATh29..._ .....do...... 14.7 Colville-Etivluk anticlines in the southern half of the province are River. 47 AZ 607. _ ...... do ..... 14.9 sharply folded and of unknown linear extent. Faults, 47 AZ 613...... do ...... 19.5 Do. 47 AZ614. 10.0 Do. a number of which appear to be major thrusts, are 47 AZ 615...... do ...... 20.3 Do. 50 AE 113...... do ...... 4.4S Imperme­ Do. numerous and important features in this province, and able. 50 AE 114...... do ... 6.44 do Do. may, together with the folds, produce fault traps and 50 AE 132a ...... do ...... 4.25 do . Do. 50AE-132b ... ..do ...... 1.94 do Do. fractures that would hold oil. In the northern half of 50AE-134a...... do ...... 4.93 . .do Do. 50AE134b...... do ...... 4.61 .do Do. this province, folding and faulting presumably were 50 AE 137 ...... do ...... 6.98 - do Rivers. less intense; in the outcrop belt of the Fortress Mountain 50AE144 .....do .... . 1.86 ..... do ... - Creek. and Torok formations, anticlines of apparently greater 50 AE 151 ..... do 3.62 .....do Do. 50 ARe 269...... do- ...... 1.54 ... ..do Colville- Kurupa linear continuity were mapped. Geophysical explora­ Rivers. 50ARe288 - .....do...... 1.74 . -do ... Do. tion might reveal the nature of the Paleozoic and older 50 ARe 295 ..... do ...... 3.55 ..... do Do. 47 AZ-617 ..... do ...... 19.3 Mesozoic rocks in this part of the province. 47 AZ 557..... 9.6 Killik tongue. Creek. 46ACh92_.._ 7.8 Structural and stratigraphic traps in the pre-Torok lower. 46AThl35...... do ...... 20.6 formations are unknown, but the possibility that they 47ATh53...... do ...... 7.7 Rivers. exist in both the southern and northern foothills sec­ 47ATh61...... do ...... 8.4 Do. 47ATh62_.._ .....do...... 13.5 Do. tions should not be overlooked. Facies changes and 47ATh62a___ ..... do ...... 7.9 Do. 47ATh64_._...... do ...... 10.0 Do. unconformities northward from the mountain front are 47ATh66...... do ...... - 11.0 Do. 47 ATh67-.._ .....do...... 4.5 Do. indicated by comparison of sections from the outcrop 47ATh67a... .. do ...... 4.9 Do. 46AThl23.._ .....do ...... 10.3 area and in Topagoruk test well 1. Structural and 47 AZ 618...... do...... 15.3 Do. 47 AZ 618a ...... do ...... 12.9 Do. stratigraphic traps might be expected also along the 50 AE 118...... do ...... 12.4 4.6.... Do. 50 AE 135 .....do ...... 15.69 27 W. Kurupa River, flank of the north-trending high near the Oolamnagavik lower 50 AE 142...... do ...... 13.91 >! . .. Colvill. River-Aupuk River. The same possibilities exist in the pre-Torok Creee. 45 AWa 95.... 13.2 Colvilk Killik Rivers. formation rocks in the northern foothills section, except 45 AWa 75 . 7.4 Killik- River, lower. 45 AWa 78 __ do ...... 9.7 Do. that there these older formations will be at considerable 45 AKr 90a .....do...... 11.2 Do. 46AChl46...... do .... 10.5 Kurupa River, lower. depth. Three major anticlines, the Kurupa, the Aupuk THE KILLIK-ETIVLUK RIVERS REGION 399 and the Killik Bend, have potential for petroleum 1947 when the lake was frozen. When visited in accumulation. Facies changes are known to occur in August 1950 by Eberlein and Reynolds, the seep ap­ the Tuktu and younger formations in this section so parently was more active, and the area of seepage stratigraphic traps are also likely to occur. included approximately 300 square feet of lake surface. The Tuktu formation is not entirely unfavorable Bubbles rose continuously at five spots and were rising structurally for petroleum potential. The Tuktu un­ at a rate of one every 2 or 3 seconds in two other spots. doubtedly underlies all the northern foothills section No trace of oil was observed at the surface or around the in this region, and is exposed in the Kurupa anticline lake. and in the Killik Bend anticline. The top of the In May 1947 Thurrell reported a gas seep, here called Tuktu is believed to be within about 500 feet of the the North Colville seep, in the east end of a small surface in the Aupuk anticline. lake near the north edge of the Colville River valley Part of the Tuktu formation at the Oolamnagavik floor and about 4.8 miles northwest of the mouth of River and between the Oolamnagavik and Killik Rivers, Aupuk Creek (pi. 43). The lake was frozen at the time and most of the Tuktu at the Kurupa River is breached of his visit, and a small area of open water led to the over structural highs on the Kurupa anticline, so most discovery. Gas bubbles were observed to rise intermit­ of this fold is unfavorable for exploration of post- tently, and a sample was collected. The field party in Torok formation rocks. Further work might delimit 1950 attempted to locate this seep, but could not find it. closure near the western end of the Kurupa anticline Bubbles rose occasionally to the surfaces of several between the Awuna and Colville Rivers. The Killik lakes in the vicinity, but no obvious seepage was noted. Bend anticline shows doubtful possibilities for petroleum in the post-Torok formation rocks, owing to the fact TABLE 12. Analyses of gas from Aupuk and North Colville seeps that the Tuktu formation is both faulted and partly Analyses by Fred L. Mohler, National Bureau of Standards. Samples from Aupuk seep analyzed 1946; A, on dry basis, but including air, owing to air leak In type of breached in the high at Killik Bend and the mouth container used; B, on a dry, air-free basis. Sample from North Colville seep of the Oolamnagavik River. analyzed 1947] The Aupuk anticline may offer exploration possibili­ Aupuk seep North Analysis factor Colville ties, but subsurface data are needed to evaluate it seep properly. Outcrop control is poor and discontinuous, A B but a west-trending structural high of undetermined i 95. (4) i 98. (8) 889.1 .06 s.07 closure is interpreted to lie about 3% miles west of the 3.3 .7 8.7 OyxTerpri .7 .7 mouth of Aupuk Creek. A west-trending fault, which .1 .06 .2 has undetermined but apparently small displacement, .4 .4 1.3 lies just north of and parallel to the axial trace in the Total------99.96 100.03 100.0 986.7 889 high. Another high, centering about 1 mile west of Soeciflc Rravitv .5622 .609 the mouth of the Kurupa River, has apparent eastern 1 Figures in parentheses questionable. closure. The western extension is believed to trend into 2 Methane obtained from difference. Total hydrocarbon heavier than methane probably less than 0.005 percent. an anticlinal zone that includes longitudinal and trans­ 8 Hydrocarbons heavier than ethane are less than 0.1 mole percent. verse faults; field data are insufficient to prove or dis­ prove closure to the west. The source of this gas is undetermined; however, it GAS SEEPS may be significant that the seeps are on the interpreted Two gas seeps in small valley-floor lakes adjacent to structural high and are very closely alined with the the Colville River northwest of the mouth of Aupuk fault that nearly coincides with the axial trace of the Creek (pi. 43) are known. They are near the crest and Aupuk anticline. Analyses of the three gas samples east end of the Aupuk anticline. (table 12) are similar. The presence of a small amount The Aupuk seep, which is the more active, is 1.7 of ethane in the Aupuk seep samples and the persist­ miles northwest of the mouth of Aupuk Creek and in ence of the seep over a period of at least 5 years are the eastern end of a small meander-scar lake at the indicative of a bedrock reservoir source. Conversely, base of a low bluff on the south side of the Colville the North Colville seep may be marsh gas that finds River valley. It was originally mapped by a U.S. Navy release under a lake where permafrost and seasonal frost geological party in 1945 and was examined and sampled are absent. in August 1946 by Chapman and Thurrell. At the COAL tune of the 1946 investigation, gas bubbles rose to the The coal-bearing strata in the Killik-Etivluk Rivers lake surface at the rate of about one per second at 20 region are confined mainly to the Chandler formation or more spots within an area of 150 square feet. It hi the northern foothills section (fig. 65). The beds was reexamined and resampled by Thurrell in May are more abundant, of greater thickness, and of better 400 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

156° 155° 154°

EXPLANATION

Phosphate

Coal beds 3 or more feet thick

Location of phosphate sample

68°

10 10 20 30 MILES

FIGURE 65. Geographic occurrence of coal- and phosphate-bearing strata in the Killik-Etivluk Rivers region, Alaska. quality in the lower part of the Killik tongue than in crops, and their lateral extent is unknown except at one the upper part of the Killik tongue or in the Niakogon point in Killik Bend. At this locality on the south side tongue. Most of the coal is of bituminous rank; of the Colville River, 1 mile downstream from the mouth however, it may vary from subbituminous to bitumi­ of the Oolamnagavik River, many coal beds were nous. Beds sampled for analysis are principally of measured (pi. 48, column 4); the same section is exposed bituminous rank. Beds 3 feet or more in thickness are where the river swings south again about 1% miles noted on figure 9; they are concentrated at two locali­ farther east. The same coal beds were measured in ties on the Colville River, one between Kucher Creek both cutbanks, and it can be reasonably assumed that and the Awuna River, and the other at Killik Bend. the beds are continuous between the two points. Many beds ranging from 1 foot to 3 feet in thickness Thus, a fair estimate of the coal for this small area also were measured at these localities. (approximately 2 square miles) can be obtained by computing the reserve for a strip-mine operation in COLVTLJjE RIVER which the maximum overburden to be removed would Coal is present in nearly all outcrops of the Chandler not exceed 100 feet (20 feet of gravel and 80 feet of formation along the Colville River between the Etivluk bedrock). About 796,000 tons could be mined from and Killik Rivers. The best beds are in the lower beds 2% or more feet thick. In removing the over­ part of the Killik tongue. The dips are generally less burden to reach these beds, other coal beds of less than than 20°, although some beds dip as much as 65°. the 2^-foot thickness would be encountered. The Although samples were collected from only a few beds total recoverable coal for this locality would then be along the Colville River, the analyses probably are just over 1,000,000 tons; this figure probably represents typical and give a fair indication of the quality of coal only a small fraction of the coal reserves along the present. The beds were seen only in river bluff out­ Colville River between the Etivluk and Killik Rivers. THE KILLIK-ETIVLUK RIVERS REGION 401

The coal from the Killik Bend area is of slightly are altered to a bright brick red and cream white, and higher quality than the other two samples from the clinkers and slag are abundant in the interval formerly Colville River area; it is from beds that are more occupied by the coal bed. deformed than the beds from which the other two The coal samples were obtained from surface expo­ samples were taken, and the higher quality probably sures and were not protected in sealed cans. Conse­ is a result of more intense folding of the beds. quently, the moisture content of the sample as received

KTJRTJPA RIVER by the Bureau of Mines was undoubtedly lower than Coal is present in most of the outcrops of nonmarine that of the coal in the bed. Other chemical and physi­ Cretaceous strata along the Kurupa River, north of the cal properties probably were changed somewhat by Tuktu escarpment. Rocks of the lower part of the exposure to air, so that the data listed in table 13 should Killik tongue are better exposed than those of the upper be considered only as approximate. part of Killik tongue and the Niakogon tongue; conse­ The carbonization products for all coal samples were quently, most of the samples are from the lower part of determined by the Fischer low-temperature carboniza­ the Killik tongue. The coal is found in beds that dip 5° tion assay and are included in table 14. The chemical to 20°, and they occupy approximately the same strati- and physical properties of the gases obtained from the graphic position as the beds along the Colville River. coal are shown in table 15. The lateral extent of the beds is unknown. In general PHOSPHATE-BEARING ROCKS the beds are overlain by shale, and so would be more suited to strip mining than underground mining because Phosphate-bearing rocks of various grades occur in the shale is not strong enough to stand without con­ the Lisburne group of Mississippian age and the siderable timbering. Shublik formation of Triassic age in the Brooks Range and southern foothills section of northern Alaska. OCWLAMNAGAVTK RIVER They are confined chiefly to the black chert-shale The nonmarine sequence of rocks on the Oolamnaga- part of the Alapah limestone (Patton, 1959). vik River includes numerous beds of coal similar to In the Killik-Etivluk Rivers region some phosphate- those on the Colville and the Kurupa Rivers; the coal bearing rocks occur in the Lisburne group, the un­ is not as well exposed and for the most part is found as named Permian formation, and the Shublik formation. float associated with rubble traces. Two of the samples Very little work was done on identifying or collecting collected from the Oolamnagavik River area were such rock in this mapped region; an intensive search analyzed. would be necessary to evaluate the quality and extent KTTjTjTK: RIVER of phosphate-bearing rocks. Five samples were col­ Coal is present along the Killik River from about 3 lected at random; the results of analyses of these sam­ miles above the junction of the Okpikruak River to the ples are given in table 16. In addition, some visual Colville River. Coal beds without bone or partings determinations of phosphate were made in the field. are locally as much as 4 feet thick. One sample from The low P2O5 content of the five samples tested, the the Killik River collected by Mertie was analyzed by complex structure and poor outcrops of the possibly the Bureau of Mines (Smith and Mertie, 1930, p. 314). phosphate-bearing rocks, and the relative inaccessa- Field sample 24AMt65 is from the type section of the bility of the region appear to preclude it for commercial Niakogon tongue on the east bank of the river 1 mile development of phosphate. east of camp D-June 29-53. The strata dip 4° to 5° S. Four samples from the Alapah limestone show less Coal beds are more numerous in strata of the Killik than 5 percent P2O5. These are from limestone, cal­ tongue, but none of the samples were analyzed. careous silty shale, black sooty siliceous siltstone, and Beds of burned coal are present along both banks of chert sections. One sample collected from the unnamed the Colville River between Aupuk Creek and the Oola­ Permian formation along the Nigu River is a calcareous mnagavik River and along the right bank of the Killik mudstone from a contact zone between igneous rock River about 2 miles upstream from the mouth. The and a green shale-chert section; it yielded 5 percent largest outcrop of burned coal is on the right bank of P2O5. Phosphate, occurring as flat pebbles or nodules the Colville about \% miles above the Oolamnagavik 0.5 to 2 inches in diameter and in beds 2 to 4 inches River. The rocks surrounding the burned coal beds thick, was identified visually in the Shublik formation. 402 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Table 13. -Analyses of samples of coal from the Killik-Etivluk Rivers region, Alaska

Analyses by H. M. Cooper, Pittsburgh Laboratory, U.S. Bureau of Mines. Sample-condition: A, as received; B, moi sture free; C, moisture and ash free (the "as received" probably represents an air-dried condition because samples were not preserved in air-tight containers) I Number , Sample Heat Laboratory Occurrence Condi­ Constituents in percent value Fischer Coal Field Stratigraphic Area Description tion Moisture Volatile Fixed Ash Sulfur (Btu) assay Sample unit matter carbon

45909 69396 46ATh69A Killik tongue Cblamnagavik River 2- foot bed in 30 feet of A 2.3 43.7 40.2 13.8 0.4 11,400 lower part 68°53'N. , 154 11' W. fine- gfained sandstone B 44.7 41.2 14.1 .4 11,600 and siltstone C 52.0 48.0 -.4 13,570 45910 69397 46A1M05 ...... d0------Kurupa River 3- foot bed overlying A 4.3 33.0 45.7 17.0 .5 10,580 68'51'N., 155° 15' W. massive sa] t- ancUpepper B 34.5 47.8 17.7 .5 11,060 sandstone C 41.9 58.1 .6 13,440

45911 69398 46AThll3 ------do------..----. -do------2- foot bed in sandstone, A 6.6 34.8 54.3 4.3 .4 11,410 68°52'N. , 155°18'W. siltstone, and shale B 37.3 58.1 4.6 .4 12,220 C 39.1 60. o .5 12,800

45912 69399 46ATM51 Killik tongue ...... -do------3- foot bed in sandstone, A 3.1 24.6 42.5 29.8 .3 8,920 upper part 69°02'30"N., siltstone, and conglomerate B 25.4 43.9 30.7 .3 9,200 155° 04' 30" W. C 36.7 63.3 .4 13,290 45914 69401 46ACh82 Killik tongue Oolamnagavik River Float from bed of Uncertain A 2.4 35.2 41.6 20.8 .5 11,030 lower part 68°50'N., 154° 14' W. thickness in sandstone B 36.0 42.7 21.3 .5 11,300 and conglomerate C 45.8 54.2 .6 14.350

45915 69402 46ACH152 --.--. do------Colville River 2- foot bed in sandstone A 3.3 31.2 45.9 19.6 .3 10,430 69°04'30"N., and claystone B 32.3 47.4 20.3 .3 10,780 155" 04' W. C 40.5 59.5 .4 13,530 45916 69403 46ACH170 ...... do------.--.. --do------2^- foot bed in shale A 2.7 33.1 46.3 17.9 .4 11,060 69° 04' 30" N. and siltstone B 34.0 47.6 18.4 .4 11,370 154° 33' W. C 41.6 58.4 .5 13,930

45917 69404 46ACH183 -----.do------_-_----do------2- foot bed in sandstone, A 2.3 35.4 51.9 10.4 .5 12,600 69°00'N., 154° 00' W. siltstone, and shale. B 36.2 53.2 10.6 .5 12,890 Numerous other coal beds C 40.5 59.5 .5 14,420 % to 3 feet thick A6848 24AMt65 1 Niakogon tongue Killik River 3- foot bed in sandstone, A 16.4 29.9 41.9 11.8 .3 8,450 68°52'N., 153°29'W. siltstone, and shale B 35.7 50.2 14.1 .3 10,110 C 41.6 58.4 .4 11,770 Smith and Mertie, 1930, p. 314.

TABLE 14. Yields of carbonization products by Fischer low-temperature carbonization assay at 500°C, as received coal basis [Analysis by W, H. Ode, U.S. Bur. of Mines. Gas yield: percent, by difference, HjS-free, scrubbed for ligbt oil; cubic feet, HzS-free, scrubbed for light oil (saturated at 60°F and under pressure equivalent to 30 inches of mercury)]

Yield (percent by weight of coal) Yield (per ton of coal) Field sample Laboratory No. Carbonized Tar Light Water Hydrogen Gas Gas (cu­ Tar (gal­ Light oil residue oil sulflde bic feet) lons) (gallons)

46 ATh 69A...... 45909...... 73.2 11.2 0.72 6.9 0.01 8.0 2,710 26.8 2.27 46 ATh 105...... 45910- 75.6 7.0 .51 10.3 .09 6.5 2,270 16.8 1.61 46 ATh 113...... 45911... _ _. 70.7 4.0 .41 14.1 .07 10.7 3,030 9.6 1.29 46 ATh 151...... 45912. 85.6 4.0 .27 7.3 .06 2.8 1,200 9.6 0.85 46 ACh 82...... 45914---. . _____ ...... 76.2 11.7 .73 7.1 .11 4.2 1,850 28.0 2.30 46 ACh 152...... 45915. 79.5 6.3 .45 9.0 .07 4.7 1,810 15.1 1.42 46 ACh 170...... 45916 78.7 8.6 .52 7.9 .08 4.2 1,870 20.6 1.64 46 ACh 183...... 45917. _____ . ______75.8 10.7 .73 7.0 .09 5.7 2,110 25.6 2.30 THE KILLIK-ETIVLUK RIVERS REGION 403

TABLE 15. Chemical and physical properties of gas by Fischer low-temperature carbonization assay at 500° C. [Analysis by W. H. Ode, U.S. Bur. Mines. Gross heating value: HjS-free, scrubbed for light oil (saturated with water vapor at 60°F and under a pressure equivalent to 30 inches of mercury)]

Composition, dry (percent by volume) HsSin Gross heating value gas Field sample Laboratory No. before Carbon Illumi- Hydro­ Carbon Methane Ethane Nitrogen removal Btu per Btu per dioxide nants gen monoxide cuft Ib of coal

46 ATh 69A ___ 45909 ...... 31.2 3.3 15.5 6.1 28.9 12.3 2.7 0.1 653 880 46 ATh 105-...... 45910 28.3 3.3 8.1 13.3 31.2 13.0 2.8 .9 686 780 46 ATh 113 45911 45.9 2.2 7.7 12.9 20.7 8.1 2.5 .5 467 770 46 ATh 151...... 45912 28.3 3.5 8.8 11.7 35.6 12.1 4.5 1.0 717 430 46 ACh 82...... - 45914.. 12.9 4.8 8.7 9.3 44.8 15.8 3.7 1.3 897 830 46 ACh 152...... 45915 .. 24.1 3.9 8.1 12.4 36.0 13.0 2.5 .8 746 680 46 ACh 170...... - 45916 17.0 4.0 9.8 9.4 42.0 14.2 3.6 .9 826 770 46 ACh 183.... _ . 45917 13.9 4.2 9.8 8.5 46.0 14.4 3.2 1.0 870 920

TABLE 16. Analysis of field samples showing percent P^O?, and equivalent uranium

Field sample Formation Location PjOj eU

North latitude West longitude Percent Assayer Percent Assayer

49 ADt 41...... Unnamed Permian formation. 68°29.5'_ ----- 156°28' . . ------5 0.004 J. Matzko. 49 ADt 134...... 68°23' .4 .004 Do. 49 ALa 8...... do 68°20.5'-.- . ... - <5 .005 Do. 50 ACh 53... ___ ...... do. ... . 68°32' ______-- <5 do ... - - .001 Do. 50 ACh 55 ...... do...... 68°32'_ 154°31. 5'-...... <1.4 .005 Do.

SELECTED BIBLIOGRAPHY Karlstrom, T. N. V., 1957, Tentative correlation of Alaska glacial sequence: Science, v. 125, no. 3237, p. 73-75. Bergquist, H. R., 1958, Micropaleontologic study of the Umiat Leffingwell, E. de K., 1919, The Canning River region, northern field, northern Alaska, in Collins, F. R., Test wells, Umiat Alaska: U.S. Geol. Survey Prof. Paper 109, 251 p. area, Alaska: U.S. Geol. Survey Prof. Paper 305-B, p. 199- Patton, W. W., Jr., 1956a, New formation of Jurassic age, in 204. Gryc, George, and others, Mesozoic sequence in Colville Bowsher, A. L., and Dutro, J. T., Jr., 1957, The Paleozoic River region, northern Alaska: Am. Assoc. Petroleum section in the Shainin Lake area, central Brooks Range, Geologists Bull., v. 40. no. 2, p. 213-218. Alaska: U.S. Geol. Survey Prof. Paper 303-A, 39 p. 1956b, New and redefined formations of early Cretaceous Collins, F. R., 1958, Test wells, Topagoruk area, Alaska: U.S. age, in Gryc, George, and others, Mesozoic sequence in Geol. Survey Prof. Paper" 305-D, p. 265-316. Colville River region, northern Alaska: Am. Assoc. Petro­ Detterman, R. L., 1953, Sagavanirktok-Anaktuvuk region, leum Geologists Bull., v. 40, no. 2, p. 219-223. northern Alaska, in Pe"we, T. L., and others, Multiple 1957, A new upper Paleozoic formation, central Brooks glaciation in Alaska: U.S. Geol. Survey Circ. 289, p. 11-12. Range, Alaska: U.S. Geol. Survey Prof. Paper 303-B, 1956, New and redefined nomenclature of Nanushuk p. 41-43. group, in Gryc, George, and others, Mesozoic sequence 1959, Phosphate deposits of northern Alaska: U.S. Geol. in Colville River region, northern Alaska: Am. Assoc. Survey Prof. Paper 302-A, p. 1-17. Petroleum Geologists Bull., v. 40, no. 2, p. 233-244. Payne, T. G., and others, 1951, Geology of the Arctic Slope of Detterman, R. L., Bowsher, A. L., and Dutro, J. T., Jr., 1958, Alaska: U.S. Geol. Survey Oil and Gas Inv. Map OM Glaciation on the Arctic Slope of the Brooks Range, north­ 126, 3 sheets. ern Alaska: Arctic, Arctic Inst. North America, v. 11, no. 1, Robinson, F. M., 1958, Test well, Grandstand area, Alaska: p. 43-61. U.S. Geol. Survey Prof. Paper 305-E, p. 317-336. Detterman, R. L., Bickel, R. S., and Gryc, George, 1963, Geology Sable, E. G., 1956, New and redefined Cretaceous formations of the Chandler River region, Alaska: U.S. Geol. Survey in western part of northern Alaska: Am. Assoc. Petroleum Prof. Paper 303-E, p. 223-324. Geologists Bull., v. 49, no. 11, p. 2635-2643. Gryc, George, Patton, W. W., Jr., and Payne, T. G., 1951, Schrader, F. C., 1904, A reconnaissance in northern Alaska: Present Cretaceous stratigraphic nomenclature of northern U.S. Geol. Survey Prof. Paper 20, 139 p., pi. 2 and 3. Alaska: Washington Acad. Sci. Jour., v. 41, no. 5, p. 159- Selvig, W. A., and Ode, W. H., 1935, Determination of gas, 167. coke, and byproducts of coal. Evaluation of laboratory Gryc, George, and others, 1956, Mesozoic sequence in Colville assay tests: Industrial and Engineering Chemistry, ana­ River region, northern Alaska: Am. Assoc. Petroleum lytical ed., v. 7, p. 88-93. Geologists Bull., v. 40, no. 2, p. 209-254. Smith, P. S., 1913, The Noatak-Kobuk region, Alaska: U.S. Imlay, R. W., 1961, Characteristic Lower Cretaceous mega- Geol. Survey Bull. 536, p. 69-75. fossils of northern Alaska: U.S. Geol. Survey Prof. Paper Smith, P. S., and Mertie, J. B., Jr., 1930, Geology and mineral 335, 74 p., 20 pi. resources of northwestern Alaska: U.S. Geol. Survey Bull. Imlay, R. W., and Reeside, J. B., Jr., 1954, Correlation of the 815, 353 p. Cretaceous formations of Greenland and Alaska: Geol. Soc. Stoney, G. M., 1900, Naval explorations in Alaska: U.S. Naval America Bull., v. 65, p. 223-246. Institute, Annapolis, Maryland, p. 66-77, pi. 1.

INDEX

Page F Page Page Chlorite, Hunt Fork shale...... -__-_--__--.___ 337 Faults, Alapah limestone.------346 Accessibility...... 328,331 Chonetessp...... 342,346 Chandler formation ______...... _ 369 Acknowledgments...... ______328 Cladophlebis septentrionalis...... 378 Fortress Mountain formation _ ___ . 356 Aerial photography ... _._...... 327 sp___....._...._.. -...... 378 Hunt Forkshale-. ------337 Alapah limestone, contact with Shublik forma­ e, Hunt Fork shale______337 Kanayut conglomerate..------340 tion.. -_ __.- _ 349 Cleiothyrodina sp.______342 Kayak shale ------340 description.....______346 Cleoniceras (Grycia) sablei...... 367 Killiktongue ------370 Alluvium .-..-..------__----._-.--._--_.-- 386 (Neosaynella) whittingtoni...... 367,377 Lisburne group ------341,342 Ammobaculites fragmentarius...... __.. 368 tailleuri...... 359,360 Shublik formation------.. 348 wenonahae...... 368 sp..-...... 377 Siksikpuk formation ------348 sp..-.-...... 348,349 Climate.. 332 Torok formation... ------357 Ammonites______357 Coal, description of deposits....______. 399 Tuktu formation.-. ------361,363,366 Anaktuvuk glaciation..______383 Kanayut conglomerate.------_ 338 Fenestrate bryozoan , undetermined _____ .- 342 Animals...._._. ..-.-.-.-..-._...... 333 Killik tongue . . 370,371,376,377,400 Fieldwork---.------326 Arcestes sp...... 350 Nanushuk group._____.______.__ 360 Fish remains ------342,346,350,360 Archeology_..-.------.. . .._.---... 333 Niakogon tongue.------_...... _ 379,380 Fluviatile deposits.------_-___- 385 Arctica dowlingi...... 380,381 Torok formation______358 Folds, Chandler formation ------369 sp__ .-. - . - 367 Tuktu formation....---.-._...... _ 361 Hunt Forkshale.------337 Astarte sp ._._... ..__...... 367 Colville group, description___.______382 Kanayut conglomerate.------340 Athyris lamellosa...... 346 petroleum possibilities______397 Kayak shale------340 sp...... 346 Colville Eiverarea, coal______...____ 400 Shublik formation------348 Atractite ssp. indet_...______350 Colville River section, Killik tongue_ ____ 371 Torok formation. ------357 Atrypa sp._ . ___ 334 Niakogon tongue._...._____.._.._ 379 Tuktu formation. ------361 Aucettina dowlingi...... 357 Tuktu formation._...... _...... 363 Foraminifera------348,352 Aupuk anticline, description...__....._...- 392 Colville River section at Killik Bend, Tuktu Fortress Mountain formation, description.---- 353 petroleum possibilities______399 formation__ ._____-.._ 366 petroleum possibilities ______------396 Aupuk seep...... _..... ___ 399 Colvitlia crassicostata...... 357 Fossils, Alapahlimestone. ------346 Avonia sp.__ .. -..-. . 342 kenti ...... 357 Fortress Mountain formation _._-____.._ 35 7 Coniopteris burejensis...... 378 Hunt Fork shale ------337 B Conodonts--..__...____._..._...... 348,349 Kayak shale ------340,342 Bairdia. -...... 336 Corals.__.._...... ___....._._.___ 346 Killiktongue------377,378 Bathysiphon anomalocoelia...... 349,352 Cretaceous rocks, petroleum possibilities...... 395 limestone, Upper Devonian ____. - - 334 brosgei...... 349,368,381 Cretaceous system, stratigraphy____ _ 352 Niakogon tongue.------380 vUta...... 349,3t>8 Crinoid debris. - 342,367 Ninuluk formation... ------381 Beetle elytrum____.______360 Cymbophora sp______. 367 Okpikruak formation... ------352 Bentonite, Nanushuk group..______361 Paleozoic and Mesozoic formations. ------349 Niakogon tongue..._ . ___ 379 D Shublik formation .. 348,349,350 Bergquist, H. R., fossil identification__ 368,378,380 Siksikpuk formation...----.------348 quoted...... - . ..-.. ._.. .-- 360 Daonella dubia...... -...... 350 Tiglukpuk formation..------351,352 Beudanticeras (Grant ziceras)...... 357 moussoni------350 Torok formation- 359,360 Brachiopods...... _._....__._.... 337,346 Devonian system, stratigraphy_ __ . - 334 Tuktu formation. ------363,367 Brachythyris sp...... _.._... 346 Dicranodonta dowlingi...... ------367 Wachsmuth limestone ------346 Bradfordoceras sp... . __._ 337 sp... -. . -- - 367 G Bryozoans______342,346 Dictyodostussp.-,------346 Brittle star...... -.- ...... 367 Galena, Hunt Forkshale------337 Dictyomitra sp ------349 Gas seeps _ ------393, 399 Brooks Eange province, structure.. ______389 Dielasma sp.. _ 346 Brown, E. W., fossil identification______378 Qastropliteasp ------367 Dimyodonsp.------______350 Buchia (Aucella) concentrica.... 351 Gastropods..------337,346,365,366 (Attcella) crassa...... 352 Ditrupa cornu...... __ - - 367 Gaudryina conodenaw ------368 (Aucella) crassicolis...... 352 Drainage.------328 irenensis ... ------368,381 Buxtonia sp..... ____ .._.. 346 Dutro, J. T., Jr., fossil identification-.--- 334,342,346 MZm ------349 quoted.. . - - 334 tailleuri...- ...... 349,357 C OaudryineUairregularis. ------368 Gavelinella awunensis. ------349 E Camaratoechia chouteauensis...... 342 Geography . ___ ------328 sp...... 337 Geologic history------393 Eberlein, G. D., quoted - - 389 Geologic investigations-.------325 Caninoid coral, undetermined_.______. 342 Echooka glaciation-__._ _ -- 385 Carboniferous and Permian systems, strati­ Ginkgo concima. ------378 graphy... ______.. 347 Economic geology 394 sp. 381 Carboniferous and Permian unit, unnamed. Entoliumutukokensis.------____ _-_ 367,377 Glacial deposits, description. 382 See Unnamed Carboniferous and Entomonotis subdrcularis...... 350 Glaciation... ------383 Permian unit. Eolian deposits.-.------387 Glomospira gaultina. ------368 Cephalopods..______._ 337 Etivluk Lake section, Kanayut conglomerate-. 339 GlomtapirettaST?.. ------348,349,352 Cephalotazopsis heteraphylla...... 378 Grniiomyamatonabbei.. ------367 Etivluk River section, Fortress Mountain for­ Gyroidinaloetterlei. ------349 intermedia...... 378 mation ___ ------355 sp._ ___...... _.______..-_....._.__- 378 Torok formation 358 Chalcopyrite veinlets, Fortress Mountain for­ mation._...... _.______.. 356 Eumetria sp. ~ _ 346 Halobia cordillerana------350 Chandler formation, coal. ______399 Eunemia speciosum...... 337 ornatissima..------35° contact with Tuktu formation______361 Eurycheilostoma robinsonae. .. 349,360 superba..------350 description_....______.______369 Exploration, early. 325 sp ------349'350 405 406 INDEX

Page Page Page Haplophragmoides topagorukensis.... . _ 349,352,360,368 Llm'estone, Upper Devonian, description__.. 334 Okpikruak formation, description..._____ 352 Heather Creek section, Fortress Mountain for­ Linoproductus lyelli...... ______346 petroleum possibilities ______395 mation._.__ 356 Lisburne group, description..______341 Oolamnagavik River area, coal...-______401 Hematite nodules, Killik tongue______370 petroleum possibilities___..______.. 395 Oolamnagavik River section, Killik, tongue . 375 Howard Pass section, Kanayut conglomerate._- 339 phosphate______...______.. 401 Tuktu formation. ______366 Kayak shale ______340 Lisburne limestone. See Lisburne group. Oolamnagavik River structural high.______391 Wachsmuth limestone ______345 Lithocampe sp___.__.______349 Oolamnaga\ik syncline, Killik tongue, rela­ Hunt Fork shale, contact with Kanayut con- Lithology, Alapah limestone ______346,347 tions ______370 glomerate ------339 alluvium,______386 Ostracodes______334,342 description__.______336 Colville group____.______382 Outuk Creek section, Kayak shale-._____. 341 petroleum possibilities.-______395 Fortress Mountain formation______353 Overtonia sp...______346 Hunt Forkshale...... -...... 336,337 Oxytoma camsetti...... ______367 Kanayut conglomerate...______337,338 Kayak shale______340 Igneous rocks, description. . ______388 Killik tongue...... -.-...... 370 Imlay, R. W., fossil identification-.. 350,357,360,367, limestone, Upper Devonian....____. 334 380,381 Nanushuk group. ______361 Palaeaneilo sp...---___.______337 Paleozoic formations, fossils.--______349 quoted-...... - ______367 Niakogon tongue._____..______378 petroleum possibilities-______395 Inoceramus attifluminus....._ __.__--.-_---.--___ 357 Ninuluk formation._.--...... -._...... 381 Palliamorphina ruckerae...... ______349 anglicus...... ______359,360,367,377 Okpikruak formation_.__...___..-. 352 cadottensis. ______367 Shublik formation..-.....--..-...--..--.- 348,349 Panope elongatissima__-______367,377 dun veganensis...... 377,380,381 Siksikpuk formation______347 sp.______367 sp_ - _ 359,360 terrace deposits______.'__ __ 386 Paragastroplites flexicostatus... ______367 spiekeri...... 367 Intrusive rocks, Shublik formation....__..____ 348 Tiglukpuk formation...__....-...-....-- 351 Peat.... 387 Wachsmuth limestone. ------345 Torok formation______358 Pecten n. sp.______350 Involutina rotalaria... _..._ 349,368 Tuktu formation...-_.-...--.-----.__. 361 Pelecypods 337,342,357,364,366,367 sp------..--__-..- _-_-__.___._._____.. 348,349 unnamed Carboniferous and Permian unit.. 348 Permafrost.__._...... ______..__ 334 Isognomon sp 360 Wachsmuth limestone...______. 345 Permian system. See Carboniferous and Itkillikglaciation..._____-----.-_-_-___---_.__-_ 384 Lithostrotionid coral, undetermined______346 Permian systems. Location...... - .-.-....--..._.. 325 Petroleum possibilities -.______._ 394 Lowthor, Stewert, fossil identification_____ 378 Petrology, igneous rocks______388,389 Lutina sp....______367 Jurassic system, stratigraphy..______350 Phosphate-bearing rocks___...______401 Jaculella elliptica ______349 M Phosphate pebbles, Shublik formation_____ 349 Physiographic provinces______328 K Macrodon sp______350 Pingaluligit Mountain section, Fortress Moun­ Marcasite, concretions, Torok formation___ 358,359 tain formation...------357 Kanayut conglomerate, description.. _____...... 337 crystals, Hunt Fork shale...... 337 Pinna hagi... 367 petroleum possibilities______395 Marginulina gatesi ..... ______349 Place names-_.__------__.._-._____ 332 Kayak shale, contact with Wachsmuth lime­ planiuscula______..__..______349 Placunopsis nuka...... ______357 stone _- - - 345 Marmarization, Wachsmuth limestone... ___ 345 description.______340 Plants 333 Mesozoic formations, fossils ______- 349 Plant fossils.- 370,373,374,376,377,379,381 Killik Bend anticline, Chandler formation, Metamorphism, Hunt Fork shale.---_____ 336 relations_---.--_.--_---..______-_ 369 Plaut remains ...... _ 338,352,353,365 igneous rooks______-______388 Platycerassp----...... _ 342,346 description.__...__ 392 Shublik formation-. _.______348 Platycrinid columnals______342 Killik tongue, relation_._-____-_._-_-----_ 370 Miliammina awunensis. _ __ _- 368 petroleum possibilities__._.__--._-______._ 399 Pleuromya kelleri...... 357 manitobensis...... ______-_. 368 sikanni __ 367 Tuktu formation exposures. ______.___..._ 361,3 66 Mineralogy, igneous rocks..- -______._ 389 Killik Bend area, coal. ______._ 401 sp.. __ 367 Misslssippian system, stratigraphy. ______340 Podozamites lanceolatus..... --_ 378,381 Killik Bend section, Killik tongue_._.-______-_ 375 Modiolus archisikanni...... -..______. 367 Killik River area, coal...... __...... _ 401 latipinnis...... __. 381 sp -______.______367 Polygonal ground ..___ . 334 Killik River section, Kanayut conglomerate... - 338 Monotis svbcircularis______350 Ninuluk formation.-.--_---_.______--_ 381 Population. __ 333 sp. . . 348,349,350,351 Porosity-permeability..__.. _...- 396 Shublik formation__._.______..______-_ 349 Moorefieldella sp______.__. . 346 Wachsmuth limestone____-_-______._._._ 345 Posidonia tteUa . . 350,351 Myopheria sp.. ______350 sp..____.____._.__... ____ 350 Killik tongue, coal.____ 400 Mytilarca sp ...... 342 contact with Niakogon tongue__------379 Previous work______. 325 description..__.-..______. _ 370 N Prince Creek formation, petroleum possibilities. 397 petroleum possibilities -______._.___-_ 397 See also Colville group. Killik valley section, Kayak shale..____.__ . _. _ 341 Nanushuk group, description....______360 Productella sp...._._ .. - 342 Knowlton, H. F., fossil identification...... 378,381 petroleum possibilities______396 Productus sp 342,346 Krotovia sp.__..-__._._._____._._.______346 Nanusliukella umiatensis__ ._.______349 Psamminopelta bowsheri..... 368 Kucher Creek section, Torok formation..._... 359 Naticoid gastropods..______- 367 Pseudomonotis subcircularis.-.. _ 350 Kummel, Bernard, fossil identification...... 350 Niakogon tongue, coal..______400 Pterophyttum sp______.. . 378 Kurupa anticline, Chandler formation, relations. 369 contact wi th Ninuluk formation ______381 Pterospermites sp... 381 description..______... 392 description-.. 378 Punctospirifer subtexta.. - 346 Killik tongue, relation....__._...... 370 petroleum possibilities.______397 sp-. ... 337,342,346 petroleum possibilities______398 Nigu Bluff section, Siksikpuk formation.___ 348 Puzosia sp 359,360 Tuktu formation, exposures..______361,366 Nilssonia sp.___..._.._..... ___. 378 Pyrite, crystals, Hunt Fork shale.--______337 Kurupa Lake section, Alapah limestone. ____ 346 Ninuluk formation, contact with Niakogon crystals, Siksikpuk formation _ 348 Kurupa River section, Fortress Mountain for­ tongue___..______378 Torok formation-___-___ 358 mation.______356 description.. 381 nodules, Kanayut conglomerate--... - 338 Killik tongre ______._._..... 373 petroleum possibilities-______397 veinlets. Fortress Mountain formation _ 356 Niakogon tongue______379 relation to Chandler formation...______369 Tuktu formation.. ______.. 365 North Colville seep...-_ _ 399 Q Northern foothills section______.. __ 391 Nuculana sp -.____ 337 Quartz, Hunt Fork shale.-- - . 337 Lacustrine deposits______386 O Killik tongue _-__ - 370 Lenticulina erecta...... 368 Nanushuk group.-..__ 360 sp...... 349 Oil shale, Okpikruak formation...... 352 Tuktu formation- ______363 Leptaena analoga...... 342 Shublik formation.. 349 Quaternary system, stratigraphy. 382 INDEX 407

R Page Page Page Radiolarians.______348,349 Stratigrrphic section, Alapah limestone Con. Torok formation, description.-.______357 Recent investigations ____ 326 Shublik formation_.______._____ 349 petroleum possibilities______396 Relief...____.____-__ -_____. 328 Siksikpuk formation-.. ______.__ 348 Torymfera sp______342 Reophaxminuta.-...... ____ 368 Tuktu formation..__-______.. 363 Transportation._.______. _._ 328 Rhynchonellid brachiopod, undetermined___ 346 Wachsmuth limestone______.. 345 Triassic rocks, petroleum possibilities. - - ____ 395 Rugosa coral, undetermined____. __ 334,342,346 Stratigraphy. .._____-_____....__. 334 stratigraphy..__ . . . 348 Structure, Alapah limestone______346 Trigonocallista sp.______.. __ __ 367 Carboniferous and Permian systems.--... 347 Trochammina eilete...... 349 Saccammina lathrami.. .____ 368,380 Chandler formation..-.______369 rutherfordi...... 368,381 Sand dunes ____ 387 Colville group___.______... 382 sp.______.. . _ . 381 Schizodus sp_____ -______337,342 description..._ . __. 389 Tuktu escarpment, location...______361 Schuchertella sp______342 Fortress Mountain formation.-..._____ 356 Tuktu formation, contact with Torok formation. Scutellum tullium...... _____ 334 Hunt Fork shale...-______337 358,360 Seabee formation, contact with Niakogon igneous rocks._ __-__.__ .. 388 description.-._. . . 361 tongue______379 Kanayut conglomerate.- .... . 340 petroleum possibilities. ______396,399 petroleum possibilities-______._ 397 Kayak shale-_- 340 relation to Killik tongue ...______370,371 See also Colville group. Killik tongue______- 370 Tumion sp______..__-. 378 Sequoia angusta....._ __. 381 Lisburne group______341,342 fastigiata...... ______378 Okpikruak formation______352 U smidtii 381 petroleum accumulation.______398 Unio sp______377 Shublik formation, description...... _____ 348 Shublik formation.._____.___.__ 348 Unnamed Carboniferous and Permian unit, petroleum possibilities______395 Tiglukpuk formation.- .._.....__... 35C description.-----. - . 348 phosphate______-______401 Torok formation ______357 petroleum possibilities..______395 Siksikpuk formation, description. ______347 Tuktu formation. ______-______361 Uvigerinammina manitobensis...... 368 petroleum possibilities______395 Subarcthophtes bickeli...... 359,360 Siphotextularia rayi..- . ____ 368 Syringothyris sp...______342,346 Valley sculpturing __ 383,384 Size of area. ____.______325 Veins, quartz, Hunt Fork shale.- - - 337 Smith Mountain section, Fortress Mountain Veniella sp..._..__ ... 367 formation ______355 Tancredia kurupana... 367,377 Verneuilinoides borealis...... 360,368,378 Solecurtus chapmani...... 367 Terebratulid brachiopod ______350 Solemya sp..____ . ._____ 342 Terrace deposits, high-level... 385 W Southern foothills section, structure... ____ 390 Thracia kissoumi...... 357 Wachsmuth limestone, description..... 345 Spinatrypa sp...______334 stelcki.-....-... 367 Weathering, Anaktuvuk glacial deposits 383 sp....._._____-______367 Spinfer adonis...... 346 Fortress Mountain formation 356 minnewankensis.---...... 342 Tiglukpuk formation, contact with Okpikruak glacial deposits. __ 383 missouriensis...-...... 346 formation--______352 Hunt Fork shale. 336,337 platynotus.. ______342 description.... 35C igneous rocks.__ 388 striatiformis...... 342 petroleum possibilities..______395 Kanayut conglomerate... 337,339 subaeguahs...... __.___. 346 Topography, Carboniferous and Permian sys­ Kayak shale--- _ - 340 tenuicostatus...... 346 tems....______347 Killik tongue 370 tornicensis...... 342 Colville group______382 limestone, Upper Devonian - 334 yukonensis...... 350 Cretaceous system .. ______352 Okpikruak formation.-__ 352 sp.._____..._....______337,342,346 Fortress Mountain formation______353 Siksikpuk formation _____ 348 SpirolocvMna ophionea.. .. 368 general-______328 Tiglukpuk formation. . 350 Squid imprint______. 367 Hunt Fork shale -______.__ 336 Torok formation - _ - 357 Stratigraphic section, Alapah limestone____ 346 Itkillik glaciation - . 384 Wachsmuth limestone._ 345 Fortress Mountain formation______355 Kanayut conglomerate..______337 Wood fragments-_ - 358 Hunt Fork shale-..-.______336 Kayak shale. ______340 Wood, petrified 363,365 Kanayut conglomerate...______338,339 Lisburne group ______.. 341,342 Worm, boring.. 360,367 Kayak shale.. __. ....___... 340,341 Killik tongue ..._._.__ 370 trails. - -_ 352,355,364,366 Killik tongue.____.____.___ . 371 Okpikruak formation______-_____ 352 Niakogon tongue. ______379 Tiglukpuk formation... . . 351 Z NInuluk formation. ______381 Torok formation ______.__ . 357 Zaphrentis konincki...... 346 o