Geology of the Shaviovik and Sagavanirktok 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-D

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

Geology of the Shaviovik and Sagavanirktok Rivers Region, Alaska By A. SAMUEL KELLER, ROBERT H. MORRIS, and ROBERT L. DETTERMAN

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

GEOLOGICAL SURVEY PROFESSIONAL PAPER 303-D

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

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary

GEOLOGICAL SURVEY Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS

Page Page Abstract______..______169 Stratigraphy Continued Introduction. ______170 Cretaceous system. ______195 Accessibility and terrane______170 Lower Cretaceous series. ______195 Climate....______171 Okpikruak formation. _ __ 195 Previous work______171 Fortress Mountain and Torok formations . 198 Present investigation____-______-_.___ 171 Lower Cretaceous and Upper Cretaceous series. 200 Acknowledgments______172 Nanushuk group. ______. 200 Physiography ______172 Tuktu formation ______202 Topography______172 Chandler formation (Killik tongue) ... 202 Drainage...______173 Ninuluk formation..--- ______203 Glacial history______.___ 174 Ignek formation. -.-.--___ _-______--__ 203 Sagavanirktok glaciation______174 Lower member______-______203 Itkillik glaciation.__-______174 Upper member______-______- 206 Echooka glaciation______175 Tertiary system______207 Undifferentiated glacial deposits.____.__-_____ 175 Sagavanirktok formation ______207 Stratigraphy.______175 Tertiary and Quaternary systems ______209 Mississippian system______177 Surficial deposits __ _ _-___-----___--_--___- 209 Lisburne group______177 Igneous rocks ______209 Permian and Triassic systems.______177 210 Sadlerochit formation.______177 Folds and faults 210 Identification of fossils.______182 210 Correlation. ___-___-______-_-_-_---___ 187 Anticlines____. 211 Triassic system___-______-_-_._-___ 187 Subsurface structure. 213 Shublik formation.___-_-.______. 187 Historical geology ___. 213 Jurassic system______191 Petroleum ______216 Kingak shale______-______-______--___ 191 References.---.--- ___. 217 Tiglukpuk formation-----__-_____--_---_---_ 193 Index.______219

ILLUSTRATIONS

[Plates in pocketj PLATE 21. Geologic map of the Shaviovik and Sagavanirktok Rivers region, Alaska. 22. Map showing distribution of glacial gravel and correlation of glacial ice advances. 23. Correlated stratigraphic sections. 24. Structure contour maps of west end of Shaviovik River area. 25. Seismic reflection profiles of west end of Shaviovik anticline. 26. Seismic reflection profiles of west end of Shaviovik anticline. Page FIGURE 26. Index map of northern Alaska--_-____---_-_-_----_------_------_------. 170 27. Correlation of stratigraphic units. ______-___-__-__-__----_----_------_---. 176 28. Generalized fence diagram of Sadlerochit formation___-_-_-_-_-___------_------. 179 29. Diagram showing suggested correlation and depositional relations of Jurassic rocks.______191 30. Diagram showing suggested correlations and depositional relations of various stratigraphic units of mesozoic age. 200 31. Diagrammatic sketch of intertonguing marine and nonmarine units of Nanushuk group ______201 32. Map showing distribution of major anticlinal unitS--__-_--______-_--_----_---_------_------212

TABLES

TABLE 1. Weather data in Sagavanirktok River area, Alaska: 9:00 a.m.-9:00 p.m., May 24-August 24, 1951 - 171 in

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

GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION, ALASKA

By A. SAMUEL KELLER, EGBERT H. MORRIS, and EGBERT L. DETTERMAN ABSTRACT An uninhabited 3,200-square-mile glaciated area on the This coarse clastic sequence grades northward to a shale and north slope of the Brooks Range in Arctic Alaska was in­ siltstone rock unit characterized by Aucella sp. In the north­ vestigated in 1951 and 1952 as part of the exploration of eastern part of the area the Okpikruak formation contains Naval Petroleum Reserve No. 4 and adjacent areas. The a basal winnowed sand unit, the Kemik sandstone member. purposes of the investigations were to correlate the rocks of The Fortress Mountain formation, a sequence of unknown Mesozoic and late Paleozoic age in the Arctic Foothills prov­ thickness composed of conglomerate, shale, siltstone, and ince from the Itkillik River east to the Canning River, and sandstone of graywacke type, crops out in the southwestern to determine the petroleum possibilities of that area. part of the area where it overlies older rocks with erosional Rocks of Mississippian to Tertiary age are present, with unconformity. It probably is correlative in part with, and all systems represented except the Pennsylvanian. The rocks in part older than, the Torok formation, a sparsely fossil­ that crop out include the Mississippian Lisburne group, the iferous shale sequence of unknown thickness. Permian and Triassic Sadlerochit formation, the Triassic The Nanushuk group comprises three formations, the Tuktu, Shublik formation, the Jurassic Kingak and Tiglukpuk forma­ Chandler, and Ninuluk. The contacts between them pre­ tions, the Cretaceous Okpikruak, Fortress Mountain, Torok, sumably are gradational, and the rocks of this group reflect Tuktu, Chandler, Ninuluk, and Ignek formations, and the oscillations of the seas between Albian and Cenomanian time. Tertiary Sagavanirktok formation. The Triassic and older The Tuktu is at least 800 feet thick and is composed of marine rocks probably had a northerly source; the younger rocks, fossiliferous sandstone, siltstone, and shale; the Chandler is a southerly source. The sedimentary record indicates that about 2,500 feet thick and is characterized by near-shore and there may have been eight separate transgressions and re­ nonmarine sandstone, conglomerate, shale, and coal. Several gressions of the sea in the area since Permian time. hundred feet of marine sandstone of the Ninuluk formation The Lisburne group is a gray crystalline fossiliferous lime­ remains in the mapped area. The Nanushuk group crops out stone that forms the north front of the Brooks Range. The only in the western part of the area. To the east it has been sequence is at least 2,900 feet thick locally. correlated with the lower part of the Ignek formation. The Sadlerochit formation has been divided into two mem­ The Ignek formation has been divided into two informal bers, the Echooka and the Ivishak. The Echooka ranges in units, a lower member believed to be correlative at least in thickness from 300 to 600 feet, contains Permian fossils, and part with the Nanushuk group, and an upper member of is typically more sandy and conglomeratic in the northern Late Cretaceous age. In its outcrop belt, the lower member part of its outcrop belt. The Ivishak, which is also more unconformably overlies the Okpikruak and Kingak formations coarsely clastic to the north, ranges in thickness from about and ranges in thickness from 2,590 feet to 1,000 feet. It 1,000 to 2,000 feet and contains ammonoids of Early Triassic locally contains fossiliferous sandstone but for the most part age. The Sadlerochit formation is overlain with no apparent comprises deltaic and lagoonal deposits of carbonaceous and angularity by the Shublik formation which is composed prin­ ferruginous sandstone, siltstone, and coaly lenses. Separated cipally of 200 to 300 feet of limy shale and limestone con­ from the lower member presumably by an erosional uncon­ taining Monotis sp. and Halo'bia sp. formity, the upper member is at least 4,000 feet thick and Two formations, one of Late Jurassic age and one of Early, contains in its lower part, in addition to the rock types found Middle, and Late Jurassic age, have been mapped. The in the younger member, bedded tuffs and bentonite. former, the Tiglukpuk, a coarsely clastic unit of variable Tertiary rocks crop out only in the northeastern part of thickness crops out along the southwestern part of the area. the mapped area and presumably overlie the upper member To the east and north, it intertongues with the upper part of the Ignek formation unconformably. These rocks, the of the Kingak shale, a fossiliferous sequence locally 5,000 Sagavanirktok formation, consist of more than 2,000 feet of feet thick. near-shore and nonmarine porous and permeable sandstone The facies of the older Cretaceous rocks, the Okpikruak, and conglomerate, shale, and coal. Fortress Mountain, and Torok formations, reflect the same Only one intrusive mass is known in the area, a small maflc general depositional trends as the Jurassic rocks. The Ok­ sill in the Mississippian limestone beds; its exact age is pikruak formation in its southern outcrop belt comprises a unknown. variable thickness of rhythmically alternating beds of sand­ Major deformation of the rocks in the area occurred during stone of graywacke type, conglomerate, siltstone, and shale. a Late Jurassic and Early Cretaceous orogeny and during 169 170 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 the Tertiary. Structurally the northeastern part of the from the Toolik to the Canning River. Studies were mapped area is less complex than the southwestern, but both cpnfined to a relatively narrow strip which ranges in parts are characterized to some degree by high-angle reverse width from 10 miles in the southwestern part of the faults, minor thrust faults, and eastward-trending normally asymmetric anticlines with steeper north flanks. The moun­ mapped area to 30 miles in the northeastern part (fig. tain front is a series of en echelon folds in rocks of Paleozoic 26). The investigations were made during the sum­ age. These folds plunge east and west beneath younger mers of 1951 and 1952 as part of the work conducted Mesozoic sedimentary rocks. The largest structure in the by the U.S. Geological Survey from 1945 to 1953 in foothills part of the area is Shaviovik anticline, which is cooperation with the U.S. Department of the Navy, about 15 miles long and probably has about 1,100 feet of closure. Office of Naval Petroleum and Oil Shale Reserves, in The rock units which contain potential petroleum reservoir its exploration of Naval Petroleum Reserve No. 4 and beds are the Lisburne group, the Sadlerochit and Shublik contiguous areas. formations, the Kemik sandstone member of the Okpikruak formation, the Tuktu, Chandler and Ninuluk formations, the ACCESSIBILITY AND TERRANE lower and upper members of the Ignek formation, and the Sagavanirktok formation. Of these formations the Tuktu, The mapped area (pi. 21) is an uninhabited, for the Chandler, Ninuluk, and Sagavanirktok are not present at most part treeless, tundra-covered, permafrost region depth where conditions are favorable for drilling. Excluding readily accessible only by plane. Willows grow ex­ structural considerations, all the other formations could be tested in the northeastern part of the mapped area; else­ tensively along the major water courses and small where, only the three oldest. Although the authors do not rule groves of poplar trees are present locally along the out the possibility of producing oil southwest of the Echooka Shaviovik and Sagavanirktok River tributaries. All River, they believe that the stratigraphy and geologic struc­ major rivers in the area are navigable by boat from ture east of that drainage are more favorable. early June until late October. None of the streams INTRODUCTION have impassable rapids, although the incised Saga­ The Shaviovik and Sagavanirktok Rivers region is vanirktok River is difficult to navigate where it flows on the north slope of the Brooks Range in Arctic through an end moraine a short distance upstream Alaska. The 3,200-square-mile area is bounded on the from its junction with the Ribdon River. Navigation southeast by the Brooks Range and extends northeast of the smaller streams depends largely on local river

50 50 100 150 MILES FIGCEH 26. Index map of northern Alaska showing Naval Petroleum Reserve No. 4 and area of report. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 171 conditions at a given time. During the spring break­ The strongest and prevailing winds are from the up, water in the Shaviovik Kiver and in tributary northwest. Ground fog is common to the stream streams such as Gilead Creek, Lupine, Echooka, and valleys during the breakup of the river ice and occurs Kavik Kivers is sufficient to permit use of small craft, more rarely during the summer months. During the but after the flood waters subside these tributary 1951 working season 17 days were lost owing to in­ streams are intermittent. clement weather; during the 1952 field season, 19 days.

CLIMATE PREVIOUS WORK The summer weather of the north slope of the The first published report on the area is by Leffing- Brooks Range is affected by local geographic condi­ well (1919), who investigated the Canning River re­ tions, and the weather records kept at Umiat, the gion during the years 1906-15. Leffingwell estab­ closest source of year-round data, are not entirely ap­ lished the nomenclature for some of the Paleozoic and plicable to the area mapped. From approximately Mesozoic rocks on the north slope of the eastern part May 20 until July 20, the sun remains above the of the Brooks Range, and the authors have retained horizon, and the long days coupled with generally fair these names in modified form. weather afford good working conditions for about 3 Parts of the area were studied later by the U.S. months. The length of the working season is de­ Geological Survey in connection with exploration by pendent partly on snow conditions in the early spring the Office of Naval Petroleum and Oil Shale Reserves. and late summer. As a rule, enough snow has melted In 1946 George Gryc and Ernest H. Lathram studied by the last week in May to permit operations, and it the rocks on the upper Sagavanirktok River, and dur­ is generally the last week in August or the first week ing the same year Gryc investigated outcrops on the in September before the snow and cold hamper ac­ upper part of the Ivishak River. In 1947 Gryc and tivities. Marvin D. Mangus made reconnaissance and semi- Table 1 is a chart of weather data compiled by the detailed studies of the sedimentary rocks along parts authors for the period May 24, 1951, to August 24, of the Shaviovik drainage and Canning River. In 1951, for the Sagavanirktok River area. Records were 1950 Gryc, Ralph W. Imlay, and Alien N. Kover re- kept only during a daily 12-hour period. Tempera­ studied the outcrops on the Canning River. tures were recorded from thermometers not afforded the protection of a standard instrument shelter, so PRESENT INVESTIGATION these readings are probably high. The amount of The present studies were made during the field precipitation and the force of the wind were estimated. seasons of 1951 and 1952 as an adjunct to the work As indicated by the table, the best weather may be done between 1946 and 1950. The primary objective expected in May and June, the worst in July and in the investigation of the Shaviovik and Sagavanirk­ August. Snow may fall during any month; rain is tok Rivers region was to map the rocks of the Meso­ predominant during the summer. Thunderstorms, al­ zoic and late Paleozoic age in the Arctic Foothills though not usually common in Arctic regions, occur province from the Itkillik River east to the Canning in June and July and are often accompanied by hail. River. A secondary objective was to define the cause

TABLE 1. Weather data in Sagavanirktok River area, Alaska, 9:00 a. m.-9:00 p. m., May 24 Aug. 24) 1951

Sky condition: O» clear sky; (D, less than 50 percent cloud cover; (D, more than 50 Ceiling: 20, ceiling less than 2,000 ft; +20, ceiling more than 2,000 ft but less than percent but less than 100 percent cloud cover; ®, 100 percent cloud cover. 10,000 ft; unl., ceiling more than 10,000 ft. Precipitation (amount estimated): 8, snow; R-L. rain or drizzle.

Precipitation Wind Sky condition Ceiling Temperature (percentage of (percentage of Obser­ observations) observations) Occur­ Velocity Direction Month vations rence (mph) (percentage of observations) Amount (inches) O CD (ID e -20 +20 unl. S R-L Avg. Maxi­ Mini­ Avg. Maxi­ Calm N. NE. E. SE. 8. SW. W. NW. mum mum mum

41 49 15 19 18 15 5 80 5 0 Tr. 46 68 22 5.8 18 24 7 24 0 2 0 2 5 34 139 14 28 32 28 19 31 50 4 14 1.0 53 92 32 8.5 30 5 13 25 2 4 2 15 17 17 July.. -.___-_ 143 4 19 31 46 18 46 36 0 25 1.9 62 92 38 5.0 15 25 20 6 1 3 7 8 6 23 114 2 15 37 45 25 46 28 4 18 .6 54 90 32 8.2 30 13 23 4 0 11 16 13 4 17 Total.. __ .. 437 3.5 _ _. Average ...... 17 19 30 34 19 32 48 3 14 ...... 54 ...... 6.9 ...... 17 16 15 1 5 6 10 8 23 172 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 of the pronounced northeasterly swing in the trend ACKNOWLEDGMENTS of the Brooks Eange front and to determine the struc­ The authors are indebted to Ealph W. Imlay, John tural implications of this swing. The objectives also B. Eeeside, Jr., Eoland W. Brown, Bernhard Kum- included isolating areas for more detailed geologic mel, J. Steele Williams, Mackenzie Gordon, Jr., Helen studies, and contour mapping of structures that could Duncan, and Harlan E. Bergquist, whose paleontologic be drilled for oil. studies of fossils contributed to an understanding of The 1951 field party consisted of 6 men: A. S. the geology of the area. They also thank Marvin D. Keller, party chief; E. L. Detterman, geologist; I. W. Mangus and Frank Cernich for their assistance in Marine and D. E. Eeed, field assistants; L. G. Barbin, caching and managing supplies for the field season, cook and field assistant; and T. F. Derrington, me­ and the pilots of Alaska Air Lines and Transocean chanic. Work began on the Echooka Eiver on May Air Lines who often flew in hazardous weather to 24, 1951, and the season ended on the Toolik Eiver supply the geologic parties. on August 24, 1951. The 1952 field party also con­ sisted of 6 men: A. S. Keller, party chief; E. H. PHYSIOGRAPHY Morris, geologist; John Downs and H. G. Eichards, field assistants; L. G. Barbin, cook and field assistant; TOPOGRAPHY and T. F. Derrington, mechanic. Because of deep Northern Alaska has been subdivided into three snow, work began on the Echooka Eiver relatively physiographic provinces (Payne and others, 1951): late, on June 9, 1952. Early snow ended the investi­ the Brooks Eange province, a belt of mountains that gations on August 22, 1952, on the Shaviovik Eiver. trend east across northern Alaska; the Arctic Foot­ Because of the remoteness of the area, exploratory hills province, a belt of hills that lie north of the methods were somewhat different from those gener­ Brooks Eange province; and the Arctic Coastal Plain ally employed. In April and early May of each year, province, an area of low relief with numerous lakes eight food caches were placed at predesignated loca­ and bogs. The area mapped lies for the most part tions. In addition to the food, which was sealed in within the Arctic Foothills province, although the 55-gallon drums, blazo, kerosene, gasoline, and motor northern part of the Brooks Eange is its southeast oil were distributed along the proposed route of and east boundary. travel. Three amphibious tracked vehicles (weasels), From the southwest edge of the mapped area the to be used by the party for its movements during the mountain front trends northeast to Kemik Creek. summer, were driven to the initial field station, Kod- From Kemik Creek it trends almost due east to the noc Lake, prior to the breakup of the ice in the major Canning Eiver and there, on the east side, heads due rivers. The geologic party was flown to the initial north. Along the entire front, the range is charac­ field station by ski-equipped Norseman plane. Fifteen terized by a series of en echelon plunging anticlines field camps were established during each year. At which control its configuration. The mountain peaks the close of the 1951 field season the weasels were are higher than 6,000 feet and relief ranges from 2,000 driven to Umiat, and at the end of the 1952 field to 3,000 feet. The crest lines are formed by inter­ season they were cached for future use at a large lake secting cirques, aretes, horns, and irregular ridges. Typically the range is composed of rocks of Paleozoic on the divide between the Kadleroshilik and Saga-o vanirktok Eivers. age except in one area between the Eibdon and Saga- The area was mapped at a scale of 1:20,000 on vanirktok Eivers where coarse clastic rocks of Meso- vertical aerial photographs made by the Navy; the zoic age form the mountain front. data were transferred to 1:96,000-scale planimetric Within the mountain area the typically broad and maps compiled from trimetrogon photographs. Areal U-shaped river valleys are filled with alluvium that maps were then reduced to a scale of 1:125,000. The extends from the edges of the rivers to the valley authors also used 1:20,000-scale vertical aerial pho­ slopes and there merges with alluvial fan and cone tographs as horizontal control for structure-contour deposits. Along the larger rivers that supported maps. Altitudes were determined by altimeter tra­ glaciers, hanging valleys are common; scour marks verse and referred to approximate sea level datum. on the main valley slopes indicate the path and upper The use of the vertical photographs facilitated map­ limit of the ice advance. ping, and permitted the mapping of larger areas than The change from mountains to foothills generally would otherwise be possible in the limited time avail­ is abrupt in most of the mapped area because of the able during the normal field season. difference in resistance to weathering of the rocks of GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 173 Paleozoic age that, for the most part, form the moun­ is so different that the entire aspect of the river is tains, and the rocks of Mesozoic and Cenozoic age that changed. Between the channels in the larger braided form the foothills. North of the mountain front, ex­ areas many smooth gravel bars as much as 500 feet cept locally for mesas, cuestas, and hogbacks underlain long are exposed during low water, and these serve by resistant sandstone, siltstone, and conglomerate, the as excellent landing fields for small wheeled aircraft. landform consists of gentle slopes, low terraces, and Ice fields are present on many of the larger braided lowlands covered with glacial debris. Some of the areas; the smaller fields disappear each year, but rem­ mesas are higher than 3,000 feet with as much as nants of some of the larger ones persist throughout 2,000 feet of relief, but elsewhere the hills rarely are the summer and become incorporated in the ice of higher than 2,500 feet and in the northeastern part the season following. The largest of these fields are of the mapped area relief is less than 1,000 feet. In on the Canning, Echooka, Ivishak, and Ribdon Rivers. the lowlands, moraines, till, and outwash gravel cap At the junction of the Saviukviayak and Ivishak the landf orms, and glacial lakes dot the area. Both in Rivers the ice field is about 12 miles long, and the ice the mountains and in the lowlands, Quaternary gravels 15 to 20 feet thick. fill the main river valleys, but terraces are more ex­ The gradients of the rivers are controlled by bed­ tensive in the lowlands and locally as many as three rock structure, differences in resistance of the rocks, levels are distinguishable. On many of the rivers and glacial deposits. The longitudinal profiles, which the lowest terrace level is characterized by oxbow generally are steep in the valley heads, flatten and lakes, cutoff meanders, and abandoned channel scars. remain relatively smooth through the mountains; from Much of the area is marked with polygonal ground, the foothills northward through the coastal plain pingos, mud slumps, and other permafrost features. there is a gradual decrease in gradient. Now that the glacial gravels have been redistributed, rivers such as DRAINAGE the Canning and the Ivishak flow more nearly at grade The mapped area is drained by three major river than do the unglaciated or postglacial streams. systems, the Canning, the Shaviovik, and the Saga- Most of the lakes in the area are glacial in origin; vanirktok. Of these, the Sagavanirktok and its tribu­ many are shallow or filled or partly encroached by taries drain about one half of the area. These rivers tundra. The largest lakes, whose beds were probably head in relict cirques, snow fields, and small glaciers scoured by ice during a part of the Pleistocene, are of the Brooks Range; they flow northward and empty Elusive Lake and Rodnoc Lake. The latter is on the into the Arctic Ocean. Glacial scour marks which are east side of the Echooka River and is about 3,400 feet present only part way up the valley slopes, indicate long and 2,000 feet wide. The former is on the west that the larger rivers predate the Pleistocene and that side of Ribdon River and is about 2 miles long and their courses were probably carved in a late Tertiary 4,000 feet wide. The depths of the two lakes are not surface. The main river channels follow antecedent known, but both are large enough for float planes to courses, although locally their tributaries are struc­ land. Other lakes that can be used for float-plane turally controlled. During the Pleistocene the river landings are on the west side of the Ivishak River north valleys probably were enlarged and straightened; after of the junction with the Saviukviayak River, and on recession of the ice, moraine and outwash deposits the west side of the Sagavanirktok River in the south­ covered the valley floors with various thicknesses of west part of the mapped area. These, however, are gravel. This reworked gravel veneer forms the floor too small to support landings by float planes other on which some of the rivers flow, although in many than the smaller types. of the stream beds the gravel layer is thin and the At the west end of the Shublik Mountains on the water flows directly on bedrock. All the streams in east side of the Canning River, springs of meteoric the mapped area can be waded during normal runoff, origin flow from orifices in the talus-covered hillsides but fording localities on the larger Canning and about 400 feet above the river level. As nearly as can Sagavanirktok Rivers are limited mostly to the area be ascertained, the water flows from an aquifer either close to the mountain front. On many of the rivers in the lower part of the Sadlerochit formation or at the flood-plain areas are locally wider than 4,000 feet, the contact of this formation with the Lisburne group. and these areas are crossed by many small streams Leffingwell (1919, p. 59) reported that during June of which interconnect to form a braided pattern. Peri­ one year the temperature of the water at Shublik odically during flood stages new channels are formed, Springs was 43° F, and that the springs flow year and when the water recedes the new braided pattern round.

544909 61- 174 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 GLACIAL HISTORY spread out as a piedmont lobe and spilled over the low divide between the Echooka Eiver and Gilead Four Quaternary glacial advances on the north slope Creek. The terminal moraines are locally preserved of the Brooks Kange have been differentiated. These as a belt of low ridges which trend across the valley are, from oldest to youngest: the Anaktuvuk, Saga- flat of the river. The east and west lateral moraines vanirktok, Itkillik, and Echooka glaciations (Detter- are less well preserved. Many of the kettle lakes in man, 1953, p. 11-12). Only the three youngest ad­ the end-moraine zone have been filled or drained, and vances have been recognized in the mapped area, and most of the lake outlets have been integrated with they have been tentatively assigned a pre-Wisconsin, present streams. Over some of the area, moraines of early Wisconsin, and late Wisconsin age by Pewe and this advance are partly covered by outwash of more others (1953, p. 13). The distribution of the gravels recent glacial advances. of these advances is shown on plate 22. On the west side of the Ivishak Eiver, the lateral The individual glaciers apparently originated in moraine of the Sagavanirktok glaciation is moderately valley heads in the Philip Smith Mountains, increased well preserved and the low hummocky ridges can be in size, moved downstream, and eventually merged to traced almost continuously for 10 miles. The end form major trunk valley glaciers. During the maxi­ moraine is poorly preserved, and the typical knob and mum development of the glaciers the highest moun­ kettle topography of the end moraine zone has been tains remained above the ice. Tributary glaciers much eroded. A tributary stream of the Ivishak Eiver eroding headward locally cut passes between major flows along the outer limit of the lateral moraine; stream valleys which subsequently became diversion together with its tributaries it has dissected the channels through whicji ice from one valley system morainal ridges. merged with that of the adjacent system. The ice Till of the Sagavanirktok advance also extends al­ spread out in broad lobes as the glaciers moved from most unbroken from the east side of the Lupine Eiver the confining mountain valleys to the open foothills, to the west side of the Sagavanirktok Eiver. The and the lowlands between some of the major streams present distribution of the gravel defines a piedmont were covered as ice lobes coalesced. The end result of lobe formed by the coalescing Lupine Kiver, Eibdon the glaciation is a fretted mountain region character­ Eiver, and Sagavanirktok Eiver valley glaciers. Lakes, ized by aretes, cols, and cirques. Valleys were gravel mounds, low hummocky hills, and swamps straightened, scoured, and broadened, and gravel was typify the ground-moraine area. The lakes have been deposited extensively in the Arctic foothills province. reduced in size by encroaching tundra and are in­ The individual glacial features of the region were tegrated with the drainage pattern. Within this pied­ interpreted mostly from a study of vertical aerial mont lobe discontinuous lateral moraines are developed photographs and, to a lesser extent, from observations best on the west side of the Sagavanirktok Eiver val­ made by the authors while in the area. The most important of the various criteria used for differen­ ley from a point opposite its junction with the Lupine tiating and correlating the three ice advances are: the Eiver to west of the Eibdon Eiver junction. End superposition and configuration of the moraines, the moraines have been partly reworked and incorporated extent of tundra encroachment on glacial lakes, the in the outwash gravels. relative degree to which streams have been integrated ITKHJOIK GLACIATION in the various morainal areas, and the topographic The Itkillik ice advance was named by Detterman expression of knob and kettle topography in the end- moraine zones. (1953, p. 11) for the river approximately 20 miles west of the Sagavanirktok. The general features of this SAGAVANTRKTOK GLACIATION glaciation in the Sagavanirktok and Shaviovik Eivers Detterman (1953, p. 11) stated that the "Sagavanirk- region are described by Detterman in his report on tok glaciation is named for morainal remnants that the Sagavanirktok-Anaktuvuk Eivers region. He cover an area of 230 square miles along the Saga- stated that: vanirktok Eiver, 60 miles east of the Anaktuvuk." * * * Till of the Itkillik glaciation covers approximately Till of this advance extends about 18 miles north of 1,000 square miles, and the drift forms fan-shaped deposits the mountain front on the Echooka and Ivishak Eivers at the mouths of major valleys. The greatest extent of this and about 30 miles north of the mountain front on the glaciation was about 20 miles north of the maximum advance Sagavanirktok Eiver. of the next glaciation. Over much of the area the till forms a mantle, 30 to 50 feet thick, over bedrock. A few well- On the Echooka Eiver, the ice from the Sagavanirk­ developed moraines are as much as 200 feet thick. Terminal tok advance upon emerging from the mountains, and lateral moraines are easily recognized, as well as the knob GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 175 and kettle topography. Glacial features have been less modi­ walls and which is breached only in the central part. fied by weathering than have the earlier * * * Sagavanirktok Upstream from the end moraine, the lateral and deposits. Numerous kettle lakes, a few tens of feet to half a mile in length, occur on the moraines. Relatively few have ground moraines are well defined, as are kame terraces been filled or drained. Lakes up to several miles in length along the scoured valley walls. are enclosed behind the moraines in many of the stream val­ UNTUFFEBENTIATKD GLACIAL DEPOSITS leys at the front of the range. Till of the Itkillik glaciation is thickest in isolated Glacial deposits in two areas, the east sides of the belts on the Echooka and Ivishak Rivers and in an Ivishak and the Canning Rivers, were mapped as un- almost continuous piedmont lobe which extends from differentiated units (pi. 22). In the former area the the east side of the Ribdon River to the west edge of deposits are sparse and there are few criteria for cor­ the mapped area. In all localities, the generally un- relation. The gravel, however, may represent till of dissected ground- and end-moraine areas are charac­ both the Sagavanirktok and Itkillik glaciations. terized by numerous kettle and moraine-dammed The moraine along the Canning River valley appears lakes, some of which are partly encroached by tundra. to represent only one major advance. The glacial On the Echooka River, both the east and the west features are more similar to those of the earlier Saga­ lateral moraines are well-defined belts of moderately vanirktok than to those of the Itkillik glaciation. high ridges. The upper limit of the west lateral mo­ Lacking enough criteria for correlation, however, the raine does not quite reach the crest of the Echooka authors mapped the deposits as an undifferentiated River-Gilead Creek divide, nor does the east lateral belt. moraine reach the crest of the Echooka-Shaviovik di­ The glacier, till from which covers the Canning vide. On the west side of the Ivishak River, till of River valley, was supplied by numerous tributaries in the Itkillik glaciation constitutes a belt about 2 miles the mountain headlands. On emerging from the wide, which extends approximately 15 miles north of mountains, it spread out westward to the Canning- the mountain front. An almost continuous series of Kavik Rivers divide and eastward into tributary val­ generally undissected gravel ridges and knobs forms leys. Owing to preglacial topography, most moraine the lateral and end moraines. In the southwestern deposits are on the west valley slope of the Canning part of the mapped area a piedmont lobe was formed River. The west lateral moraine is well preserved in during this glaciation by coalescing valley glaciers a series of linear ridges and benches extending about which emerged from the mountains along Ribdon 25 miles north of the mountain front. West of the River, Accomplishment Creek, and the Sagavanirktok junction of Cache Creek and the Canning River, the River. This glacial belt is well denned by the mo­ moraine is about 2,000 feet above the river level. The raines which, controlled by the preglacial topography, uppermost lateral ridges, which are composed of silt- curve downstream from the mountain front. Erratics, to cobble-size particles with erratics as much as 4 feet probably dating from the Itkillik glaciation, are pres­ in diameter, are superimposed on a pediment(?) ent on both the east and the west side of the Saga­ gravel surface. A moderately well denned end mo­ vanirktok River at altitudes greater than 3,000 feet. raine forms an arc from the crest of the Canning- Kavik divide down to the valley floor and crosses the ECHOOKA GLACIATION Canning River about 8 miles north of the junction of The Echooka glaciation was named by Detterman Ignek Creek. Kettle lakes in the moraine areas have (1953, p. 12) for the Echooka River, the most easterly been partly filled by encroaching swamp; most have tributary of the Sagavanirktok River, and is the last been integrated with the drainage pattern. recognizable major ice advance in the region. Till of this advance does not quite extend to the north front STRATIGRAPHY of the Brooks Range on tributary streams of the Geologic studies in the Shaviovik and Sagavanirk­ Shaviovik and Sagavanirktok Rivers; in all localities tok Rivers region included examination of the Mis- it represents deposits of independent valley glaciers. sissippian Lisburne group, the Permian and Triassic The glacial features of the Echooka advance are Sadlerochit formation, the Triassic Shublik formation, most conspicuous on the east side of Ribdon River and the Jurassic Tiglukpuk and Kingak formations, the on Accomplishment Creek. In the former area, end Cretaceous Okpikruak, Fortress Mountain, Torok, moraines enclose Elusive Lake. In the latter, knob Tuktu, Chandler, Ninuluk, and Ignek formations, and and kettle topography in the end-moraine zone is the Tertiary Sagavanirktok formation (fig. 27). Owing relatively fresh. The end moraine is a prominent to the limited time available for the field studies, the gravel ridge which curves downstream from the valley rock units were examined only in semidetailed fash- 176 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

IVISHAK RIVER TO AGE EUROPEAN STAGE ELUSIVE LAKE AREA CANNING RIVER

QUATERNARY

? n Pliocene TERTIARY Miocene Sagavanirktok formation Oligocene Missing Eocene Paleocene T 7 Danian Missing

Campanian Upper Ignek formation, Santonian upper member Coniacian Turonian Cenomanian ? Ninuluk formation , Ignek formation, CRETACEOUS ' Chandler formation' (Killik tongue) lower71 member i Albian Tuktu formation Torok formation Fortress Mountain formation Lower Aptian Missing Barremian Missing Neocomian Hauterivian Valanginian Okpikruak formation r 1 Okpikruak formation Berriasian i Kimmeridgian

Argovian Upper Oxfordian J Divesian Tiglukpuk formation JURASSIC Kingak shale 1 ^ -i Callovian ' Bathonian Middle Bajocian Toarcian o Missing Lower Pliensbachian O 1 Sinemurian Hettangian Missing Rhaetian Upper Norian CJ Shublik formation Shublik formation Karnian Ladinian & Middle Missing Missing 1 Anisian Lower Scythian Upper Sadlerochit formation § Sadlerochit formation (Ivishak member) O£ UJ (Echooka member) CL. Lower T T

Stephanian =i o |IANPENNSYLVANIAN 'H o Westphalian <3 Missing Missing

CL CL ^ Namurian

MISSISSIPP LowerCarboniferous Vise'an Lisburne group Lisburne group

FIGURE 27. Correlation of stratlgraphlc units In the Shaviovlk and Sagavanirktok Rivers region, Alaska. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 177 ion; the Lisburne group was studied briefly. The gen­ blue-gray thin-bedded variety. Chert lenses and eralized measured sections of the rock units are nodules are common throughout the unit. The entire correlated on plate 23. sequence of rocks in the Lisburne group has a strong organic odor and is generally abundantly f ossilif erous. MISSISSIPPIAN SYSTEM No complete sections of the Mississippian rocks were UESBTJBNE GROUP measured by the authors. In the south-central part of the area on Flood Creek, the upper 2,900 feet of History and age. The Mississippian rocks were the group is preserved along the north limb of an originally named the Lisburne formation by Schrader anticline, but its base is not exposed. The lower part (1904, p. 62) "to designate the limestone, with some of the section is composed of fine- to medium-crystal­ shale, occurring next above the Stuver series at the line limestone, in beds as much as 15 feet thick, and head of Anaktuvuk Eiver." Schader (p. 62-63) thinner interbeds of dark-gray limestone. Higher in stated that the name was "taken from Cape Lisburne, the section the rocks are less massively bedded, more where apparently the same formation, consisting of coarsely crystalline, and darker in color. An 80-foot limestone and shale, occurs." Smith and Mertie (1930, unit of tan crinoidal limestone is near the middle of p. 168-169) used the name Lisburne limestone for the the section. Fossils are relatively scarce and include formation and noted that in general it "crops out in crinoid stems, brachiopods of productid and Spirifer one or more belts, from 1 to 20 miles in width, extend­ type, and corals. ing from the Arctic Ocean in a general easterly direc­ tion to the Anaktuvuk Eiver and thence into the Can­ PERMIAN AND TBIASSIC SYSTEMS ning Eiver region and eastward to the international boundary." Bowsher and Dutro (195T) raised the SADLEROCHIT FORMATION Lisburne to group status and divided the group into History. The Sadlerochit formation was first two formations, the Wachsmuth limestone (the lower mapped by Leffingwell in the general area of the Sad­ part) and the Alapah limestone (the upper part). In lerochit Mountains. He (1919, p. 113) applied the the earlier work of Schader (1904, p. 62) the rocks name "Sadlerochit sandstone" to a sequence of rocks were considered to be Devonian in age. George H. "consisting of about 300 feet of light sandstone or Girty's critical study of the earlier collections and his dark quartzite * * * [which] overlies the Lisburne examination of the fossils collected in the Cape Lis­ limestone with conformable contact and underlies the burne locality by Collier (1906) resulted in the as­ Shublik formation with unknown contact but with signment of a Mississippian age for the rocks of this parallel bedding." It is not entirely clear where the group. type locality of the Sadlerochit sandstone was in­ The Lisburne was studied only briefly by the au­ tended, but presumably Leffingwell had in mind the thors, and therefore no breakdown of the group into south side of the Sadlerochit Mountains. The rock formations was attempted. unit was originally assigned a Pennsylvanian age Distribution and lithology. The resistant limestone (Leffingwell, 1919, p. 114-115), but with additional of the Lisburne group forms the north front of the work G. H. Girty became convinced that it was "more Brooks Eange and is the major rock unit constituting properly to be regarded as belonging to the Permian." the folded and faulted mountain system. Owing to (Smith, 1939, p. 32). its occurrence in mountainous peaks and its distinctive The rocks which lie stratigraphically between the light-gray color, this rock unit is the one most easily Lisburne group and the Shublik formation in the recognized in the Shaviovik and Sagavanirktok Eivers Canning Eiver area and elsewhere in the area mapped region. Over most of the area the Lisburne group by the authors include siltstone, shale, limestone, and underlies the younger Sadlerochit formation discon- chert, in addition to sandstone. It is more consistent formably, although locally the older rocks abut the with present terminology, therefore, to designate the younger in high-angle reverse-fault relationship; the unit the Sadlerochit formation rather than the Sad­ contact of the group with older rocks is not exposed in the mapped area. lerochit sandstone. The succession defined above is In general, the Mississippian rocks consist of crys­ thicker than Leffingwell's measurement of 300 feet; talline and hydroclastic limestone which locally is it includes rocks of two ages: Permian, in the lower oolitic and lithographic. The limestone is normally part, and Early Triassic, in the upper. Moreover, the thin bedded, although more massive in the lower part two age units differ in lithologic characteristics. It of the unit. The massively bedded limestone is gen­ appears that Leffingwell mapped the same rock se­ erally lighter in color than the somewhat siliceous quence as did the authors, but his description of the 178 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 formation, thickness, and fossil suites applies in gen­ spicules and detrital grains widely spaced in a ground- eral only to the lower part. mass of silica. The only nonopaque accessory mineral The authors divided the formation into two mem­ is olive-green tourmaline; small irregular grains of bers which are here named the Echooka member of magnetite and leucoxene are scattered throughout the Permian age and the Ivishak member of Early Trias- rock. The siltstone is. composed predominantly of sic age. The type locality for the former is on the subangular quartz grains, which constitute as much as upper part of Kemik Creek (see p. 181); the type 80 percent of the rock in some samples, and chert frag­ locality for the latter is on Flood Creek (see p. 182). ments. The quartz grains have serrate edges showing The Ivishak member rests on the Echooka member some replacement by silica cement, have a subquadrille with no apparent angularity and underlies the Shu- fracture pattern, are well sorted, and average 0.15 mm blik formation disconformably. Because of the recon­ in size. The tourmaline grains are rounded. Minute naissance nature of the field studies, the members are specks of limonite are scattered throughout the rock shown only locally on the geologic map; on other illus­ or are present as stringers filling fracture veins. trations the formation is mapped as an undifferen- In the area of Flood Creek (section A, fig. 28) the tiated unit. Echooka member consists of blue-gray limy brown- Distribution. The Sadlerochit formation is well ex­ weathering siltstone, gray limy shale, and blue-gray posed and is one of the most persistent units within the limestone. Fossils are more abundant at this locality mapped area. It crops out in a belt 1 to 3 miles wide but constitute the same suite that is found in the sec­ extending in a northeasterly direction along the north tions to the northeast. No sections of the member front of the Brooks Eange. Typically the rocks are were measured in any detail southwest of Flood Creek. the flanking beds of the east- and west-plunging en However, the rocks of the Sadlerochit formation that echelon anticlines which form the mountain front, and immediately overlie the Lisburne group southwest of generally are exposed best in cutbanks on the smaller Flood Creek are more like the rocks of the Flood streams. In the areas between major streams, where Creek section than they are like those of the sections anticlines in the Mississippian limestone have been farther northeast. The general facies trends shown dissected, the resistant brown-weathering rocks of the on figure 28 indicate that the Echooka member was Echooka member form north-dipping triangular- deposited from a northerly or northeasterly source. shaped wedges on the limbs of the structures and Ivishak member. The Ivishak member ranges in locally are present as erosional remnants on the crests. thickness from about 1,000 to 2,000 feet. Near Eagle In similar fashion, the resistant brown-weathering Creek (section Z>, fig. 28) the rock unit contains more rocks of the upper part of the Ivishak member typi­ sandstone than elsewhere in the area. Excepting this cally form discontinuous cuestas which trace a sinuous and minor variations, the rocks of the member are course parallel to the belt of north-dipping sedimen­ nearly the same at one locality as they are at another. tary rocks of the Eange front; and locally they are The member typically consists of two parts: a lower preserved also as mesas in the axial parts of the syn- nonresistant shale and minor siltstone unit and an clines. upper resistant siltstone, shale, and sandstone unit. Echooka member. In the mapped area the Echooka Limy disk-shaped concretions ranging in diameter member ranges in thickness from about 300 to about from several inches to several feet are present locally 600 feet. Whether this range is due to thinning during in the lower part of the Ivishak member and contain deposition or to erosion is not readily determinable on Early Triassic ammonites and pelecypods. The fossils the basis of the available data. The member varies in are somewhat more abundant in the sections near the facies from one part of the area to another; these Ivishak Eiver but were found in most sections changes are shown in part on figure 28. In the north­ throughout the mapped area. The upper part of the ern Canning Eiver area (section Z>, fig. 28), it is Ivishak member consists of an alternation of dense typically sandy to conglomeratic and locally contains siliceous laminated siltstone, shaly siltstone, and minor fossiliferous limestone. From the Canning to the sandstone. The siltstone weathers brown and is lo­ Echooka Eiver it characteristically consists of mas­ cally massive with blocky fracture, although more sively bedded dense cherty siltstone that is dark blue commonly it is thin bedded; when seen in isolated gray and locally limonite spotted. Subvitreous gray- exposures it cannot always be distinguished from some green to black chert and light-gray quartzite are inter- of the massive siltstone of the Echooka member. The bedded with the siltstone, and fossiliferous limestone similarity between the siltstone of the two members lenses are present locally. Examined in thin section is also apparent in thin sections. For example, a the chert is composed of randomly oriented sponge sample collected from the upper part of the Ivishak GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 179

59°45/

69

69°00'l- FIGURE 28. Generalized fence diagram of the Sadlerochit formation. member is composed of about 82 percent subangular The incomplete Canning Eiver section (section 20) quartz grains, 13 percent chert fragments, and small was measured along an incised stream approximately amounts of plagioclase, calcite, and leucoxene. The 1% miles east of the Canning River at lat 69°26' N., similarity between the siltstone of the two members and long 146° 02' W. The section is confined on either and the general facies trends shown on figure 28 indi­ side by high-angle reverse faults, and the strata are cate that the source area for both members was the overturned in many places. One fault juxtaposes same. limestone of Mississippian age with the rocks of the Measured sections. Seven stratigraphic sections of Echooka member and the other fault juxtaposes the the Sadlerochit formation were measured in semi- upper beds of the measured section with contorted detailed fashion in the mapped area, and these are rocks of the Ivishak member. Details of this section illustrated on plate 23. .Locations of the sections are and those that follow are listed in descending strati- shown on plate 21. graphic succession. 180 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Sadlerochit formation, section 20 Ivishak member Continued nite-stained siltstone concretions present in the Feet Contorted strata of the Ivishak member. shale and contain ammonites and pelecypods Thrust fault. (field sample 52 AKe 23; see p. 187) ______100 Ivishak member: Feet Unit consists of limonite-stained hackly-fracturing Alternating finely laminated, locally crossbedded shaly siltstone and of dark-gray finely laminated dark-gray siltstone and hackly-fracturing shaly pyritic siltstone lenses and beds that weather to siltstone; siltstone weathers rust brown _____ 236 metallic hues. Ammonite 38 ft above base of Partly exposed section similar to above ______206 unit (field sample 52 AKe 22) ______150 Alternating beds of siltstone and rust-weathering Echooka member: shaly siltstone; siltstone bedded from a few Covered interval; chert float _ __ _ 50 inches to 2 ft thick, locally cherty; some layers Massively bedded dense blue-gray brown-weathering finely laminated and crossbedded ______191 cherty siltstone and chert. Poorly preserved bryo- Rust-weathering shaly siltstone and very fine platy zoans and brachiopods present in cherty limestone micaceous siltstone ______138 about 80 ft above base ______250 Covered interval ______76 Disconformity. Bust-weathering black shaly siltstone with hackly fracture and large concretions containing poorly Total measured thickness of Sadlerochit forma­ preserved ammonite impressions ______232 tion ______1,122 Echooka member: Lisburne group. Massively bedded blue-gray rust-weathering siltstone and blue-gray chert ______83 The Pogopuk Creek section (section 16) is exposed Fault. along an incised valley at lat 69°23' N., and long 146°38' W., where the strata, dipping from 35° to Total measured thickness of Sadlerochit forma­ 60° N., form the north flank of an east-plunging anti­ tion ______1,162 Lisburne group. cline. The contact between the Ivishak member of the Sadlerochit formation and the Shublik formation The Kavik River section (section 18) is exposed in is well exposed along the creek, and no angular dis­ cutbanks at lat 69°21' N., and long 146°25' W. The cordance is apparent between the two units. The con­ rocks of the measured section form the north flank tact between the Echooka member and the Lisburne of an east-plunging anticline and dip 45° N. At the group is covered. The measured section is thicker top of the measured section a high-angle reverse fault than the sections farther east, and the formation con­ juxtaposes the 45° north-dipping strata with con­ tains a greater amount of chert in the lower member. torted strata of the Ivishak member. At the base of the section the Echooka member rests disconformably Sadlerochit formation, section 16 on the Lisburne group. The measured section at this Shublik formation. locality does not represent a total thickness for the Ivishak member: Feet formation, owing to a high-angle reverse fault at the Dense siltstone interbedded with light- to medium- top. However, this section has been correlated with gray sandstone; siltstone locally micaceous; minor dark-gray hackly-fracturing shaly silt- its unfaulted counterpart on the south flank of the stone ______520 anticline, where the formation in its entirety is ap­ Alternating well-indurated siltstone and shaly proximately 1,500 feet thick. siltstone and 1- to 3-ft beds of light- to medium- gray, brown-weathering sandstone; some of the Sadlerochit formation, section 18 sandstone crossbedded and ripple marked; lo­ cally siltstone and shale beds micaceous and Contorted strata of the Ivishak member. carbonaceous _ _ _ _ _ 128 High-angle reverse fault. Ivishak member: Feet Less resistant unit of thin-bedded dense siltstone Alternating siliceous thin to massively bedded dark- and of hackly-fracturing shaly siltstone; silt- gray limonite-stained siltstone and hackly-frac­ stone weathers brown. Ammonite on bedding turing dark-gray shaly siltstone ______182 plane at base of unit ______335 Covered interval______87 Covered interval ______700± Alternating beds of dark-gray finely laminated silt- Echooka member: stone, locally cherty, from x/_ to 2 in. thick and Silicified dark-gray limonite-stained siltstone in brown-weathering shaly siltstone ______215 beds as much as 3 ft thick 12 Covered interval ______61 Covered interval ______120 Similar to third unit above; siltstone more massive Dense blue-gray limestone grading laterally into with blocky fracture ______27 olive-gray chert in beds 1 to 2 ft thick; chert Hackly-fracturing brown-weathering shaly siltstone contains abundant small pyrite crystals. Fos­ and thin beds of dense siltstone; spheroidal limo- sils present in the limestone ___ _ 47 GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 181

Echooka member Continued Echooka member: Feet Dark-gray to blue-gray chert and silicified brown- Feet Massive limonite-stained cherty and quartzitic weathering limestone ______17 siltstone and limonite-stained hackly-fracturing Dark-blue-gray chert in beds as much as 4 ft thick shaly siltstone ______130 and silicified dark-blue limestone ______46 Thin-bedded brown-weathering shaly siltstone, Covered interval ______20 and dense medium-gray siltstone 100 Contact (?) arbitrarily placed at base of covered in­ Quartzite, varicolored chert, cherty dark-gray terval. massively bedded siltstone, and light-gray thinly bedded siltstone. Fossils are present in brown- Total measured thickness of Sadlerochit for­ weathering limestone beds approximately 50 ft mation ______1,945 above the base of the section. (USGS Paleozoic Lisburne group. Iocs. 15806 and 15826) ______230

The Juniper Creek section (section 15) is exposed Total measured thickness of Sadlerochit for­ along a deeply incised tributary of Juniper Creek at mation ______1,810± lat 69°22' N., and long 146°48' W. Only the basal Lisburne group. 564 feet of the formation is well exposed and these The Gilead Creek section (section 9) was measured strata are overturned to the north. in cutbanks on both sides of a small tributary of Sadlerochit formation, section 15 Gilead Creek at lat 69° 16' N. and long 147°29' W. Echooka member: Feet Strata of the measured section dip 32° N. and are Brown-weathering cherty and silicified siltstone and overlain by contorted beds of the Ivishak member. blue-gray chert in beds as much as 4 ft thick; Only the basal 896 feet of the formation was measured. quartz veins as much as 1 ft thick ______339 Limonite-stained cherty and silicified siltstone con­ Sadlerochit formation, section 9 taining abundant horn corals, spirifer-type brachio- pods, and bryozoans (USGS Paleozoic loc. 15820) __ 17 Ivishak member: Feet Massively bedded siliceous siltstone and dark-gray Interbedded shaly siltstone and siltstone; lower part of unit comprises proportionately equal chert ______72 Cherty limestone containing abundant brachiopods amounts of shaly siltstone and siltstone; upper (USGS Paleozoic loc. 15819)______4 part almost 100 percent siltstone; siltstone dense, Massively bedded siliceous siltstone and dark-gray cherty, and dark-gray with blue- and brown- iron-stained chert ______132 weathered surfaces; locally limonite-stained; limy siltstone concretions present in the shale 251 Total measured thickness of Echooka member_ 564 Interval largely covered; few thin beds of dense Lisburne group. cherty brown-weathering siltstone 90 Dense dark-gray thinly bedded brown-weathering Section 12 was measured along Kemik Creek be­ siltstone and hackly-fracturing dark-gray shaly tween lat 69°22' N. and lat 69°23' N. The lowest 460 siltstone ______82 feet of the rock unit is the type section of the Echooka Fissile dark-gray brown-weathering shaly siltstone; some disseminated pyrite ______80 member. These strata are exposed on the east side Echooka member: of the creek and dip 24° N. on the flank of an east- Hard massively bedded gray siltstone with metallic- plunging anticline. In the type section fossils are blue- and brown-weathered surfaces ______181 poorly preserved. The collections listed are from cor­ Less massive blue-gray siltstone _ 30 relative horizons on the Shaviovik River approxi­ Dense massive cherty brown-weathering siltstone in beds as much as 5 ft. thick; cleavage at right mately 3% miles west of the type section. angles to bedding; limonite nodules, pyrite, and Sadlerochit formation, section 12 quartz stringers locally present in the unit. Bryozoans, horn corals, and pelecypod fragments Shublik formation. present in lenses in the lowest beds of the section 182 Contact not exposed. Ivishak member: Feet Total measured thickness of Sadlerochit forma­ Poorly exposed platy hackly-fracturing shaly silt- tion ______896 stone and light-gray thinly bedded siltstone Lisburne group. with metallic-blue-weathered surfaces______400± Cuesta-forming unit of alternating light-gray silt- The thickest section of the formation was measured stone in beds as much as 6 inches thick, platy along the east side of Flood Creek between lat 69° 02' limonite-stained medium-gray finely laminated 40" N. and lat 69°03'20" N. where the strata dip siltstone, quartzite, and hackly-fracturing shaly siltstone ______430 from 40° to 54° N. Neither the upper nor lower con­ Poorly exposed tan-weathering platy siltstone and tacts of the formation are well exposed at this locality, shaly siltstone ____. ______520± but both can be mapped with relative accuracy. The 544909 61 3 182 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Echooka member of this section (section 7) is com­ Localities where fossils were collected from the Echooka member posed predominantly of limestone and shale in con­ USGS Field North West trast with the resistant siltstone and chert which make Paleozoic sample latitude longitude Description locality up the member in the sections farther northeast. The 15808 51 AKe 94... 69°04'30" 147°47' upper 2,110 feet of the measured rock unit is the type of formation on Ivishak River. section of the Ivishak member. 15814 51 AKe 104.. tion (section 7, pis. 21, 23). 15815 51 AKe 106- 69° 148°02' Sadlerochit formation, section 7 from lower contact to 400 ft above base of member on Savlukviayak River. Ivishak member: Feet 15816 51 AKe 123.. 68°51 148°04' on Lupine River. Dense cherty siltstone and hackly-fracturing dark- 15817 51 AKe 162.. 68°40'30" 148°20/ base of member near small gray shaly siltstone; siltstone has light- to dark- tributary of Ribdon River. gray interiors and is locally limonite stained on 15806 51 ADt 8 69°22' 147°11' member on Shaviovik River; weathered surfaces; in beds from % to 6 in. correlated with a horizon in section 7, plate 23. thick; finely laminated and locally crossbedded 620 15807 _ 51 ADt 69... 69°17'30" 147°22' Cuesta-forming unit comprising alternating beds of on west side of Echooka River. hackly-fracturing cherty siltstone and shaly silt- 15810 51 ADt 117- 69°04'30" 147°47'30" on small tributary on west stone 'and of sandy siltstone; siltstone, medium- side of Ivishak River. gray with yellow- and brown-weathered surfaces 520 15811 51 ADt 126- 68°57' 148°07'30" tributary of Saviukviayak More shaly than overlying cuesta-forming unit but River. 15812 51 ADt 146 68°48'30" 148°17' retains the general characteristics; siltstone 15813 51 ADt 147- 68°50/ 148°17' River. dense, cherty, finely laminated, and iron stained; 1 Limestone immediately above shale dark gray ______400 52AKelA__ I 69°22'30" 147°14' contact of member with Lis­ 15818 52 AKe 1A-. burne group on Shaviovik Predominantly medium-gray brown-weathering River. 15819 |52 AKe 8 . hackly-fracturing shaly siltstone and dense thin- Creek section (section 15, pis. bedded siliceous siltstone; limy red-brown concre­ 21, 23). 15820 52 AKe 9 . tions as much as several feet in diameter in section (section 15, pis. 21, 23) . 15821.. _ .. 52 AKe 19 69°20'30" 146°26' random distribution throughout the shale. Nodules about 100 feet above base of contain abundant ammonites and pelecypods (field member. 15823 52 AKe 21 69°20'30" 146°26' sample 51 AKe 104A) ; many of the fossils in above base of member. 15824 52 AKe 31... 69°30'30" 146° varying stages of pyritization ______570 ern tributary of Cache Creek. 15825...... 52 AKe 38 ... 69°31' 146°13' Echooka member: Springs. Upper part of unit consists of 50 ft of massive dense 15826...... 52 AMo 5. 69°22'30" 147°15' Silicified siltstone on Shaviovik River; correlated with a cherty brown-weathering siltstone; remainder of horizon in section 7, plate 23. 15827 52AMo6... 69°22' 146°58' unit consists of interbedded massive limy blue- member on Fin Creek. gray siltstone, light brown-weathering limestone, 15828 52 AMo 30.. 16, pis. 21, 23). and dark-gray to silvery limy and nonlimy shale; 15829 52 AMo 37- 69°30'30" 145°57' member on small northern limestone hydroclastic and locally coquinoid, is tributary of Cache Creek. present both as lenses and beds (USGS Paleozoic 15830 52 AMo 39. _ 69°30'30" 145°57' the base. loc. 15814) ______465 15831 52 AMo 40. . 69°30'30" 145°57' 50 ft above the base. 15832. __ . 52 AMo 41.. } 69°30'30" 145°57' Total measured thickness of Sadlerochit forma­ 15833 ... 52 AMo 42. _ 15834 52 AMo 43.. 69°30'30" 145°57' Same as 15829; about 261 ft tion ______2,575 above the base. Lisburne group.

IDENTIFICATION OF FOSSILS Seven reports on the identifications of fossils were Echooka, member. The fossils of the Echooka mem­ submitted to the authors between 1952 and 1954: one in November 1952 covering Mr. Gordon's examinations ber which were collected by the authors were examined and 6 in February 1954 covering Miss Duncan's and by James Steele Williams, Helen Duncan, and Mac­ Mr. Williams' identifications. The following ma­ kenzie Gordon, Jr. Mr. Gordon examined the ceph- terial is quoted from Mr. Williams' memoranda, ex­ alopods; Miss Duncan, the bryozoans and corals; all cept where otherwise noted: other fossil material was examined by Mr. Williams. Their assignment of a Permian age for the fossil col­ "Previously fossils from beds in the Sadlerochit had been examined and reported on by Girty. The Sadlerochit material lections whose localities are listed below is based in that Girty had was poor. The fossils were obviously more part on a comparison of these forms with Sadlerochit closely related to species from the Arctic Island regions of fauna identified as Permian by Girty, and in part North America and from northern Europe and Asia than they were to species from farther south in North America. upon the presence of forms in these collections char­ Girty had no adequate suites of typical specimens of these acteristic of the Permian in other parts of the world. Arctic species for comparative purposes. Much of the im- GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 183 portant literature was in the Russian language. Because of Paleozoic_ these conditions, Girty identified almost none of the species. locality Field sample Instead, he considered most of them probably to be new a form from the Sadlerochit for­ species, but he did attempt to give as much of an idea as mation thought by Girty to be he could of their general appearance by citing the name of a related to Productus timanicus of species to which they were in some degree related. He indi­ Stuckenburg. The ornamenta­ cated possible relationships by 'aff.' references. Girty had tion on our specimen is un­ also designated fossils from Permian beds in other parts of fortunately not well shown. Also Alaska by the same method. present are several other inde­ "In examining the specimens collected during the present terminate productoid forms and a investigation of the Shaviovik-Sagavanirktok area, I had to brachial valve of a brachiopod contend with many of the same difficulties that attended whose external characters re­ Girty's earlier work. In terms of what is required nowadays semble those of some Camero- for identifications of genera and species, the material is poor, phorias (Stenocismas) illustrated commonly being molds or incomplete specimens, which ordi­ by Tschernyshew from the late narily lack ornamentation. This one would expect because of Paleozoic (Upper Carboniferous the unfavorable lithology and the distortion to which the or Permian) of Russia." A rocks were subjected. The material for comparison is meager poorly preserved bryozoan was to nonexistent; the literature is scattered and in many lan­ designated as a "stenoporoid guages, some of which are imperfectly known to the writer. bryozoan genus indeterminate" As a consequence it was decided to identify the species as by Helen Duncan who examined nearly as possible with the material studied in Girty. This, it. Duncan later reported that "a it was felt, would provide a substantial basis for correlation diagnostic Permian coral, Calo- within Alaska. Girty's material was available for direct phyllum [=Polycoelia of authors] comparison. Identification with species from other parts of occurs in this assemblage." the world could come later, when good material for com­ 15815... 51 AKe 106..__ "This is a small collection, but it parison became available. Then more reliable correlation does contain a fragment of a productoid shell and that is suffi­ with foreign deposits can be made. Both the Geological Sur­ cient to restrict it to Permian or vey and the U.S. National Museum are making efforts to older age. The fragment does increase the number of topotype and authentic specimens of not appear to have been re­ Arctic Permian species in their collections. Studies now in worked. Also in the collection progress on better material from more accessible and less are indeterminate remains of rugged and isolated parts of Alaska may in the future provide several other shells. Fragmen­ the keys for more secure and informative identifications of tary horn corals in this collection the Permian species of the Alaskan Naval Petroleum Reserve have been referred to Helen and for correlations with Permian deposits of other countries." Duncan. She says that the ma­ terial is too poorly preserved for usas Paleozoic certain identification but reports locality Field sample that one specimen has an axial 15808... 51 AKe 94. _ "This collection contains remains of structure and other features sug­ several productoid shells and also gestive of Verbeekiella, a Permian remains of other brachiopods that genus." are undeterminate as to family 15816.. 51 AKe 123._ "This collection consists of a single but that suggest spiriferoids. Two specimen of a spiriferoid brachio­ of the productoids are closely re­ pod that resembles in general lated to the form referred to by shape a form identified from the Girty as Productus n. sp. aff. P. Sadlerochit by Girty as one septentrionalis Tschernyshew related to Spirifer rectangulus [Marginifera septentrionalis of Kutorga. It cannot, however, authors] from Permian rocks in be definitely identified." Alaska. The affinities of the 15817. . 51 AKe 162__ Gordon reported brachiopods, pe- other productoid are not clear. lecypods, and gastropods of too * * * fragmental a nature for iden­ 15814 51 AKe 104--- "This collection contains several tification. specimens of a species identical 15806._ 5lADt8. "The principal fossils in this collec­ with or closely related to the form tion comprise a number of from Alaska, designated by Girty productoid forms. One is the as Productus n. sp. afif. P. septen­ form identified by Girty in the trionalis Tschernyshew [Margin­ early 1900's as Productus n. sp. ifera typica septentrionalis and M. aff. P. septentrionalis (Tscherny­ septentrionalis of authors] and shew) (Marginifera typica septen­ other productoid forms, one of trionalis and M. septentrionalis which resembles in size and shape of authors). Another productid 184 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

U8G8 US6S Paleozoic Paleozoic locality Field sample locality Field sample resembles to a degree in form a "the typical raised spiral lirations species identified by Girty as of this characteristic Permian being closely related to P. multi- genus." Williams added that sir iatus Meek. The ornamenta­ the "other forms represented in tion is not preserved and the it are mainly remains of brachio­ likeness of the form to P. multi- pods and include a specimen that striatus is only moderately close. is probably a Meekella or a closely Still another of the productid related form. Another resembles type of shells seems to be closely a Derbyia in form and ornamen­ related in shape to a form identi­ tation, two others are produc­ fied by Tschernyshew as P. toids, one especially resembling mammatus Keyserling. All the a form in the Alaskan Permian forms mentioned by name above and several fragmentary indeter­ have been identified from beds minate remains of spiriferoid classified as Permian in Alaska, forms. Bryozoa in the collection and I believe that the presence were referred to by Miss Duncan of these forms with the absence as stenoporoid bryozoans, inde­ of contradictory forms gives terminate. This collection could substantial evidence on which not be younger than Permian and to base a Permian age assignment. its general aspect strongly sug­ 15807. . 51 ADt 69. "The collection * * * contains gests that it is Permian in age." indeterminate remains of a coral 15812... 51 ADt 146__ Gordon identified indeterminate and of bryozoans, and brachiopods gastropods and gastrioceratid largely represented by molds. cephalopod, genus undetermined. Among the brachiopods are molds 15813___ 51 ADt 147__ "This collection contains many of productoids and pieces of fragmentary productoid shells of molds of other brachiopods, and also parts of molds of pro­ which pieces are indeterminate. ductoid shells. A single gastro­ One of the productoid fragments pod in the collection has been is a piece of the lateral slope of a examined by Ellis Yochelson form whose surface ornamenta­ who describes it as an indetermi­ tion suggests that it is a nate straparollid gastropod. Waagenoconcha. A mold of the 15818... 52AKelA.... "This collection contains markings pedicle valve of a productoid that are probably from crinoid suggests a new species known columnals and brachiopods of from the Permian. Another several types including two or brachiopod is probably a chonetid, three genera of productoid forms. whereas remains of other brachio­ One of the productoids is either pods are indeterminate." Miss closely related to or actually the Duncan examined the remains species identified by Girty as of a coral which she described Productus n. sp. aff. P. septen- as a crushed mold of a horn coral, trionalis (Tschernyshew); another indeterminate. The bryozoans productoid is indeterminate as to she speaks of as "many molds of genus. Among other brachio­ ramose Bryozoa, indeterminate, pods is a large chonetid, similar and a Fenestella? sp. indet., an in form to a manuscript species impression. The aspect of this of Girty from the Permian of faunule is strongly Permian." Alaska. Also present are frag­ 15810.. 51 ADt 117_ _ "This collection consists mainly of ments of other brachiopods. many incomplete molds and * * * fragments of molds of productoid 15819... 52 AKe 8. "Collection contains remains of brachiopods. Some slabs are brachiopods, pieces of fibrous almost coquinas of remains of hinge structure of a pelecypod, such shells. None can be identi­ and possibly remains of other fied. One mold resembles the organisms, all indeterminate. form that has previously been * * * identified in Alaskan collections 15820... 52 AKe 9. "This collection * * * has cross as Productus multistriatus Meek sections and other remains of in general shape but there is not brachiopods, pieces of the fibrous enough of it to make a positive hinge structure of pelecypods and identification. * * *" indeterminate remains of pecti- 15811 51 ADt 126____ Gordon reported a Pseudogastrioce- noid pelecypods. Among the ras sp. in this collection, bearing brachiopods are incomplete re- GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 185 usas uses Paleozoic Paleozoic locality Field sample locality Field sample mains of a specimen that is defi­ horn coral, this collection con­ nitely a Chonetes and parts of sists largely of molds of fenes- specimens representing probably trate bryozoans * * * the only two species of Productus genus I can certainly identify is * * *" Miss Duncan added that Fenestella. Some of the forms "this collection contains a good with stout branches and coarse many specimens or parts of spec­ meshwork undoubtedly belong imens of stenoporoid bryozoans. to other genera, but structures I am fairly certain some of them needed to place them are not are Stenopora in the strict sense. preserved. There are also molds No comparable material has been and a few fragments of some described from North America. goniocladiid bryozoan and indi­ * * * Stenopora is especially cations of branching forms. characteristic of the Permian, * * *!' and is one of the most diagnostic 15862... 52 AMo 5. "This collection contains several forms found in the Permian of productoids, at least two speci­ eastern Australia." mens of which are of the same 15821... 52 AKe 19. This collection contains "many in­ size and shape as the species complete remains of fossils, in­ referred to by Girty as related cluding a portion of a trilobite to Productus (or Marginifera) n. pygidium and a brachiopod that sp. aff. P. septentrionalis (Tsch- is not preserved well enough to ernyshew). Other brachiopods determine definitely its generic of Permian aspect are also repre­ affiliation. It is either a chonetid sented, as are indeterminate or a productoid. * * * pectinoid pelecypods. A stein- 15823... 52 AKe 21. "This collection contains several kern of an indeterminate gas­ specimens of a brachiopod that tropod was examined by Mr. resembles very much in shape Yochelson. * * * and proportions a form referred 15827__. 52 AMo 6. "This collection contains fibrous to by Girty as Productus (or remains of the hinge-structure Marginifera) n. sp. aff. P. aagardi of pelecypods, two or three Toula (Anidanthus and Pseudo- productoids, one of which re­ marginifera aagardi of authors) sembles a species from the from the Permian of Alaska. Permian of Alaska thought by * * * Girty to be closely related to 15824... 52 AKe 31. "This collection contains remains Productus aagardi of Toula. In of spiriferoid and productoid addition there are several shells brachiopods. Included among of a species that I tentatively the spiriferoids are forms repre­ have placed in Rhynchopora. senting the species identified by 15828_ 52 AMo 30. _ "This collection consists of remains Girty as Spiriferella aff. S. of brachiopods but there are also arctica Houghton. One of the several pieces of fibrous struc­ productoids is the form from the tures that are probably the re­ Permian of Alaska referred to by mains of the hinge-structures of Girty as Productus (or Margini­ pelecypods, possibly of Myalinas. fera) n. sp. aff. P. aagardi Toula. Among the brachiopods are re­ * * * mains of several spiriferoids, at 15825... 52 AKe 38. "This is a large collection contain­ least one of which represents the ing a piece of a horn coral, several form thought by Girty to be re­ genera of Bryozoa, brachiopods lated to Spiriferella arctica of and remains of a pelecypod. * * * Houghton. One mold seems to Among the brachiopods are several be of a productoid that is not specimens belonging to Phricodo- complete enough for generic thyris (Squamularia of authors) or determination. There are also to a closely related genus, a few several specimens that I am remains of the form identified tentatively referring to Rhyncho­ by Girty as Spiriferella aff. S. pora. The aspect of this faunule arctica Houghton, and indeter­ is Permian. minate pieces of productoid 15829... 52 AMo 37. _ "This collection contains a fauna shells. The age is Permian." whose affinities I am not able to Miss Duncan added that in definitely determine. Several "addition to an indeterminable incomplete specimens of 'Spirifer- fragment from the calyx of a ina' s. 1., remains or probably 186 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

USOS USGS Paleozoic Paleozoic locality Field sample locality Field sample two species of Chonetes. A piece were sawed were found to contain of fenestrate bryozoan and pos­ abundant bryozoan debris de­ sibly fragments of other genera rived mainly from fenestrate of brachiopods comprise it. The types fenestellids and probable 'Spiriferinas' and the species of goniocladiids none of which are Chonetes are not distinctive spe­ generically identifiable, but in cies as regards Permian vs. general rather characteristic of Carboniferous age. Some frag­ the Permian." ments of brachiopods suggest 15833 52AMo42._ "Collection 42 * * * contains sev­ the form known in Alaska as eral productoid forms, and some Spiriferella artica Houghton but spiriferoid forms of brachiopods. the fragments are very small and None is completely preserved. the suggestion cannot be counted Productoid forms include por­ upon to indicate the correct tions of forms that may .be identity of the brachiopods. Buxtonias, Waagenoconchas and 15830... 52*AMo39--._ "This collection contains several dictyoclostids, and a form that specimens that actually are or is most certainly a Linoproductus. are closely related to the form One of the spiriferoids resembles identified in Alaskan collections in general shape and in all ex­ by Girty as Productus (Mar- ternal features preserved, the ginifera) n. sp. aff. P. septentrio- form from the Alaskan Permian nalis (Tschernyshew). Also sev­ said by Girty to be related to eral incomplete specimens of the Spiriferella arctica Houghton. form Girty thought was related Some of the other spiriferoids to Spiriferella arctica Houghton. are large and have the general Other incomplete molds of bra­ proportions of some of the Missis- chiopods and poorly preserved sippian spirifers. * * * bryozoans are present * * * 15834 52AMo43__._ "* * * Jack Smedley * * * ex­ The age is Permian. amined this specimen and he 15831 52AMo40_-__ "This collection contains remains believes it to be an Aviculopecten or molds of indeterminate bra­ of a sort related to A. girtyi chiopods that probably repre­ Newell, which species is known sent spiriferoid and productoid from the Permian of the main­ genera and one specimen that land of the United States." is probably a Rhynchopora. * * *" Miss Duncan stated that "bry­ Ivishak member. The fossil collections from the ozoans in this lot are mostly Ivishak member were examined by Bernhard Kummel, broken into very small frag­ and those fossils that can be readily identified he as­ ments. Both fenestrate and signed to the early part of the Scythian stage (Early ramose forms are present. * * * I think that Fenestella, Polypora, Triassic). and some sort of goniocladiid are Localities where fossils were collected from the Ivishak member present. The ramose forms are not identifiable. A small slab was usas Field North West apparently collected for the im­ Mesozoic sample latitude longitude Description pression of a fairly large piece locality of frond, which I think represents 51 AKe 87 69°08'30" 147°48' Limy concretions in lower part Fenestella', however, I cannot be of member in small cutbank on an eastern tributary of sure about the identification. Ivishak River. 51 AKe 104A_ The general aspect of the bryo­ pis. 21, 23). zoans is Permian rather than 52 AKe 22 Kavik River section (section 18, pis. 21, 23). older." 52 AKe 23 Do. 15832... 52AMo41__ "Collection 41 has crinoid col- 52AM031-. 51 ADt 106- 69°09' ilrll' Limy concretions in complexly umnals, remains of productoid faulted zone on Kashivi Creek. and other brachiopods, and two 23595.... 51 ADt 108.. 69°09'30" 147°43'30" Limy concretions in faulted zone on Kashivi Creek. horn corals. * * *" Miss Dun- 52 AKe 7 69°22'20" 146°44'30" The upper cuesta-forming beds can added that the "coral in this of member between Cobble Creek and Juniper Creek. lot suggests Euryphyllum, a genus 51 ADt 91 69°16'30" 147°34' Probably the upper cuesta- forming beds of member on known from the Permian of Qilead Creek. Australia. Pieces of rock that GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 187

USGS Kummel reported (written communication, April Mesozoic 1954) as follows on the identification of fossils from the locality Field sample 23595 51 ADt 108- Otoceras boreale Spath Ivishak member: The 0. boreale Spath * * * is the U8G8 most interesting and diagnostic Mesozoic specimen in all of this material. locality Field sample This specimen is, as far as can ______51 AKe 87__. Ophiceras (Lytophiceras) cf. 0. com­ be told from the crushed speci­ mune Spath men, identical to the East Green­ ? Discophiceras sp. indet. land 0. boreale described by Ammonoids indet. Spath. All species of Otoceras These specimens are comparable to are very similar. Otoceras is di­ ophiceratids from East Green­ agnostic of the lowest Scythian land. Their preservation leaves and is known only from the much to be desired, and the two Himalayas, East Greenland, and identifiable specimens are juve­ possibly Djulfa in Armenia. niles. They are probably of older 52 AKe 7- Ammonoids indet. (Proptychites?). age than the material of 52 AKe 51 ADt 91. ? Glyptophiceras sp. indet. 23, but younger than 51 ADt 108. [See listings below.] CORRELATION 51 AKe 104A. Ammonites and pelecypods. 52 AKe 22___. Ammonoids indet. The Sadlerochit formation has not been definitely 52 AKe 23_. Ophiceras cf. 0. greenlandicum correlated with other Triassic and Permian rocks of Spath northern Alaska. Southwest of the area mapped by Proptychites cf. P. rosenkrantzei the authors, Patton (1957) mapped a Permian(?) Spath Claraia stachei Bittner rock unit (the Siksikpuk formation) of 250 to 300 All the identifiable specimens * * * feet of red, green, gray, and black shale, siltstone, and show strong affinities to the East chert, the basal part of which is characterized by a Greenland Scythian faunas de­ brachiopod, gastropod, and horn coral fauna. Al­ scribed by Spath 1930, 1935. The Proptychitids occur in a though the features of the Siksikpuk formation are younger horizon than the Oph­ not similar to those of the Echooka member of the iceratids in the East Greenland Sadlerochit formation, it is quite possible that the two fauna. * * * The specimens of units are in part equivalent. these lots are of a slightly Early Triassic fossils have not been reported pre­ younger horizon than that of 51 ADt 108 [see USGS mesozoic viously in Alaska, and to the knowledge of the authors loc. 23595 below], * * * that is, no rock units equivalent to the Ivishak member of the they are late Octoceratan or Sadlerochit formation are present west of the Saga- early Gyronitan. vanirktok River. 52AMo31_--_ * * * indeterminate ammonoids (Proptychites) and Gervillea sp. TRIASSIC SYSTEM The ammonoids * * * are too SHTJBLJK FORMATION poorly preserved for identifica­ tion, but there is enough avail­ History. The Shublik formation was first described able to say they are Triassic and by Leffingwell in his report on the Canning River re­ probably Proptychitids. gion, in which he stated (1919, p. 115-116): 51 ADt 106____ Ophiceras cf. 0. tibeticum Griesbach 0. tibeticum Griesbach is a conspic­ The Shublik formation, which consists of about 500 feet of uous member of the earliest dark limestone, shale, and sandstone, overlies the * * * Sad­ Scythian beds in the Himalayas. lerochit sandstone and underlies the * * * Kingak shale. The identification of the Alaskan Neither the upper nor the lower contact has been found, but specimens with the Himalayan the dip of the three formations seems to be the same. As a species has been done to empha­ rule the Shublik is easily separated from the next older rocks size its gross morphological fea­ * * * but the younger Kingak shales are so similar to those tures. Identity with any of the of the Shublik formation that the determination of the di­ Greenland species described by viding line between these formations must rest on paleon- Spath is difficult to establish be­ tologic evidence. cause of faulty preservation and Leffingwell (p. 116) named Shublik Island "at the lack of extensive topotype col­ lections. southwest corner of the Shublik Mountains, where the 188 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 formation was first discovered" as the type locality, Tiglukpuk, Okpikruak, or Fortress Mountain forma­ but he pointed out that the "locality * * * is not favor­ tions. able for study, for the exposures are complicated and Lithology. The thickness of the Shublik formation scattered." For a typical section he listed one at is relatively uniform within the entire mapped area; "Camp 263 Creek", which is probably a tributary of it ranges from about 200 to 300 feet. The rocks are the Sadlerochit River on the south side of the Sad- typical of those deposited in the lagoonal environ­ lerochit Mountains. Leffingwell's section (1919, p. ments or in waters of restricted circulation; except for 116) is given below: local variations facies change very little from one part of the mapped area to another. All the rocks of the Triassic section at Camp 263 Greek formation have a strong fetid odor on fresh fracture Feet 1. Unexposed, probably soft shales ______800 surfaces. 2. Scattered exposures of dark limestone, some shaly The lower part of the formation consists of phos- beds ______80 phatic siltstone, shale, and very fine grained sandstone. 3. Unexposed, probably soft rocks ______140 The shale is characteristically black, owing to the high 4. Dark calcareous sandstone, conglomeratic(?) ____ 30 carbon content, limy, and clayey to silty; it contains 5. Unexposed, probably soft rocks ______300 abundant dark-gray nodules which are coated with a 1,350 white salt. The phosphate-bearing siltstone is most extensive in the eastern half of the mapped area and The authors believe that Leffingwell's unit 4 is the the fine grained sandstone on the east of Kemik Creek. base of the Shublik formation in the Canning River The phosphatic siltstone, in thin sections, is composed area and that his unit 5 is part of the Sadlerochit for­ of 56 percent quartz, 14 percent phosphate, 29 percent mation. In general his units 2, 3, and 4 constitute the calcite, and 1 percent plagioclase. The quartz grains total Shublik formation from the Canning to the are angular, are in a lime matrix, and are partly re­ Itkillik River. placed by calcite. Phosphate is present as small Distribution. Rocks of Late Triassic age have been oolites and amorphous dark-brown pellets and has reported from many localities along the north slope accumulated about and enclosed the quartz grains. of the Brooks Range from the Okpilak River to Cape The limy matrix has recrystallized to calcite in the Lisburne. In the mapped area, the rocks of the form of isolated rhombs or large irregular masses. Shublik formation crop out in a belt, generally less The upper part of the Shublik formation consists of than 2,000 feet wide, which can be traced along the clayey to silty shale with interbeds of dark-gray lime­ Range front from the Canning River to Elusive Lake. stone. The uppermost beds form a unit composed The Triassic rocks are present also about 2 miles west predominantly of limestone which weathers buff. The of the Sagavanirktok River in a breached and faulted limestone ranges from sandy to cherty and is charac­ anticlinorium. The present surface underlain by Tri­ terized by an abundant fauna of Late Triassic age. assic rocks is typically one of low relief, and the for­ Phosphatic siltstone is present locally at the contact mation is generally exposed in small cutbanks along of the Shublik with the Kingak shale, megascopically the streams. Only locally are the rocks sufficiently it appears similar to the phosphatic siltstone in the resistant to form rubble traces in the interstream lower part of the formation. areas, and these persist only short distances along the Measured sections. Four sections of the Shublik for­ strike. The formation is easily identified by its char­ mation were measured in the mapped area, and these acteristic black shale, its abundant Late Triassic fossil are correlated on plate 23. The locations of the sec­ suite, and its buff-weathering limestone. It is espe­ tions are shown on plate 21. Most of the sections are cially important as a marker unit, inasmuch as it poorly exposed and only the one on Kavik River (sec­ represents the only predominantly calcareous unit be­ tion 18) is suitable for detailed study. Section 18 was tween the Lisburne group and the marine formations measured in the cutbanks along the east side of the of the Nanushuk group. The unit overlies the Sad­ river at lat 69°21'30" N., long 146°25' W. In this lerochit formation without angular discordance; it is locality the Triassic rocks outline the configuration of overlain disconformably by the Kingak shale and, de­ a major east-plunging anticline and syncline; the pending on the amount of post-Tiglukpuk and post- strata of the measured section dip northward 60° and Okpikruak erosion, may be overlain locally by the form the south flank of the east-plunging syncline. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 189

Feet The structure of the section is relatively uncompli­ Phosphatic siltstone grading into clay and shaly cated except in the upper part where the strata are siltstone ______27 isoclinally folded. The lower contact of the rock unit with the Sadlerochit formation is well exposed and Total measured thickness of Shublik formation__ 279± no angular discordance is present between the for­ Sadlerochit formation. mations. The limy shale and limestone of the Shu- Section 9a was measured in a cutbank along a small blik formation is readily distinguishable from the tributary of Gilead Creek at lat 69°16' N., and long overlying shaly siltstone of the Kingak shale at this 14T°32'30" W. Only the basal 180 feet of the forma­ locality, but the contact between the two is not ex­ tion is exposed at this locality, and the contact with posed. the Sadlerochit formation is covered. This section ShubliJc formation, section 18 contains more siltstone than the sections farther east; Kingak shale. it does not contain the phosphatic siltstone beds that Con tact (?), placed arbitrarily at the top of the phos- characterize the eastern sections. phatic siltstone. Shublik formation: Feet ShulliJc formation, section 9a Feet Interbedded black buff-weathering hydroclastic lime­ Interbedded calcareous siltstone and silty to clayey stone, limy black shale, and medium-gray fossili- shale. Entire section is very dark blue gray to almost ferous phosphatic siltstone (USGS Mesozoic Iocs. black. Most of the siltstone beds are 1 to 4 ft thick 24048, 24047, and 24046; see p. 190) ______58 with the shale interbeds 6 to 8 in. thick. Shale con­ Interbedded black limy shale and black limestone stitutes about 30 percent of the section. The siltstone (USGS Mesozoic loc. 24045) ______27 has hackly fracture with quartz veins in the fracture Interbedded massive medium-gray nodular lime­ zones. Buff-weathering limestone in beds 3 ft thick stone, locally hydroclastic, and black nodular is present at the top of the unit. Mud lumps are clay shale (USGS Mesozoic loc. 24044) _____ 25 abundant throughout the section, and fossils are Interbedded medium-gray dense limestone, earthy present about 10 ft from the top (USGS Mesozoic limestone, and black limy clay shale______30 loc. 23591) ______180 Medium-gray dense limestone and black limy shale 11 Sadlerochit formation. Predominantly black earthy limy clay shale, minor dense hydroclastic limestone. Fossils 30 ft above Section 6 was measured in cutbanks along a small base of unit (USGS Mesozoic loc. 24043) ; fossils eastern tributary of the Saviukviayak where the 20 ft above base of unit (USGS Mesozoic loc. northeast-striking strata dip about 30° N. Neither 24042) ______62 the upper nor the lower contact of the formation is Massive medium-gray phosphatic siltstone _____ 17 well exposed although it is possible to map both with Total measured thickness of Shublik formation. 230 relative accuracy. The upper limestone beds of the Sadlerochit formation. section are more cherty than their counterparts in the Section 14 was measured along the west side of other 3 sections. Cobble Creek, a small western tributary of the Kavik Shublik formation, section 6 Eiver. Only the lower part of the section is well ex­ Kingak shale. posed and the east-striking strata dip approximately Shublik formation: Feet 45° N. The lower contact is marked by a 1-foot zone Section predominantly black calcareous fissile and platy clay shale, silty shale, and mudstone; upper that weathers red; the upper contact is not exposed part of section consists of buff-weathering silty but has been arbitrarily placed at the top of the and cherty fossil-bearing limestone (USGS Meso­ phosphatic siltstone. zoic loc. 23589) ______300± Sadlerochit formation. ShufiliJc formation, section 14 Age. The fossils collected by the authors in the Kingak shale. Shaviovik and Sagavanirktok Eivers region were ex­ Shublik formation: Feet Unit largely obscured; upper part phosphatic fossil- amined by Bernhard Kummel and John B. Eeeside, bearing silty limestone and siltstone (fossils are Jr., and their analyses of the fossil lots were submitted the same as those of USGS Mesozoic Iocs. 24048, to the authors in the form of written communications 24047, and 24046) ; exposures of black limy shale 200± at various times during 1952. In the section that fol­ Thin-bedded black fissile shale and white-weathering lows, the fossil lots, or the individual fossils marked limestone ______30 Black shaly siltstone and dense phosphatic slightly with an asterisk were identified by Eeeside; other calcareous siltstone ______22 fossils were identified by Kummel. 544909 61- 190 EXPLORATION OP NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Fossils and localities at which they were collected from the Shublik formation

USGS Field North West Mesozoic sample latitude longitude Fossil Description of locality locality

23586... ____ 51 AKe 12 69°23'15" 147°07'30" Ammonite indet. (fragment) Monotls sp. 23587 51 AKe 55 69°11'50" 147°43' "Rhynchonetta" sp. Monotis subcircularii (Qabb) Gastropod Indet. *23688 51 AKe 79 69°09'50" 147°46'30" Lima'1 sp. 23589. - 51 AKe 111.. * Cardiomorphal sp. *Margarites1 of J. P. Smith Hoplotropites cf. H. mofflti Smith 23590... - 51 AKe 126- 68°53' 148°08'30" *Halobia cf. H. corditterana Smith Lupine River. *Trachycerast sp. Tropites stantom Smith Halobia sp. indet. *Juvavites1 sp. Sirenites sp. mdet. 23691. 51 ADt 80... Halobia cf. H. dilatata Kittl _ .... . _____ .. OQKQO 51 ADt 83 _ 69°16'20" 147°33' Lima? n. sp. 23593 __ - 51 ADt 84 69°16'10" 147°34'30" *Posidonia cf. P. jacksoni Smith * Trachyceras (Protrachycerast) sp. *Clionites1sp. Tropites stantoni Smith Sirenites cf.

The fossil lots of the Shublik formation have been Karnian in aspect. Any meaning read into this association at assigned a Late Triassic age by Reeside and Kummel. this time would be inadvisable on the data available * * * Halobia ranges from the Karnian into the Norian. Monotis In a written communication to the authors on Decem­ subcircularis is Norian in age. Halobia has its biggest de­ ber 5, 1952, Kummel stated that: velopment in the Karnian, but it is important to remember The faunal assemblage of these lots [lots 24042 to 24048, that it also occurs in Norian strata. inclusive] * * * suggests a Karnian age. Most of the species In the same memorandum, Kummel further stated are identical with or very similar to species from Karnian that: beds of central and southern Alaska. The brachiopods and Lots 24071, 24072, and 24074 contain essentially the same pelecypods are likewise similar to forms from the Karnian fauna. The pelecypods, gastropods, and brachiopods are the of Bear Island. same as those from the Karnian fauna of the Nation River, The identification of Monotis subcircularis in lot 24047 is Alaska. * * * These faunas are likewise similar to the fauna made with much question. The specimens are incomplete but of Bear Island described by Rohm (1903). The pelecypods what can be observed strongly suggests this nomenclature. of lot 24073 were only tentatively placed in Area inflata Oberg Monotis subcircularis is generally considered a good Norian which was originally described from Anisian beds of Spitz- guide fossil but the whole assemblage reported on here is bergen. They by no means suggest an Anisian age, however. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 191 In a written communication, April 7, 1952, Kummel formation of Jurassic(?) [now Cretaceous] age." noted that lots "23586, 23589, 23590, and 23593 are Leflmgwell further describes the formation as in­ Karnian in age. The fossils present are related to cluding nearly black thin-bedded friable shale and species found in the Chitistone limestone of the Nizina fossilisferous and nonfossiliferous "concretions both in Valley and to forms reported from the numerous spheroidal form and in beds half a foot thick." Karnian localities in Alaska including those of the Leflmgwell called this rock unit the Kingak shale, and Firth and Canning Rivers, northern Alaska." the authors apply this name to all strata between the Triassic and Cretaceous systems in the area east of JUEASSIC SYSTEM Lupine River. As Leflmgwell indicated, the Kingak Two Jurassic formations were mapped in the Shavi- locally underlies the Ignek formation, and although ovik and Sagavanirktok Rivers region: (a) the Tig- he assigned the Ignek a Jurassic (?) age, it is now lukpuk formation, a shale and coarse clastic rock unit known to belong to the Cretaceous system (p. 205-207). which is believed to be entirely Late Jurassic in age, Distribution. The Kingak shale crops out along and (b) the Kingak shale, a Lower, Middle, and Up­ the front of the mountain range between the Canning per Jurassic rock unit composed predominantly of River and the Lupine River in a belt ranging from shale. The suggested correlation and depositional re­ 3 to 10 miles in width; it is infolded with Permian lations of the Jurassic rocks are shown in figure 29. and Triassic rocks within the mountains near the The two formations intertongue in the general area of Kavik River. .The formation overlies the Shublik the Lupine River but ^he change in f acies is not as formation with no apparent angularity; it underlies abrupt as the areal map might indicate. The Jurassic the Cretaceous Okpikruak formation disconformably, rocks in the Lupine River area reflect a transition and, depending on the amount of post-Okpikruak between the two formations and were separated at erosion, locally unconformably underlies the Creta­ this locality for convenience. ceous Ignek formation. The area underlain by the Kingak is typically one of low relief; exposures of KINGAK SHALE the formation are relatively few and are confined gen­ History. The name Kingak was assigned by Lef- erally to cutbanks along north-flowing streams. Lo­ fmgwell (1919, p. 119) to the rocks at the type locality cally, rubble traces of ironstone and shale are present "Kingak Cliff, near Camp 263, at the southeast end on the hillsides in the interstream areas, but these of Sadlerochit Mountains." He described the forma­ exposures of the Kingak shale are so spotty that they tion as consisting "of about 4,000 feet of black shales, are of little help in defining the rock unit. Over much * * * [which overlie] the Shublik formation of Tri- of the area it is difficult to differentiate the rocks of assic age and probably * * * [underlie] the Ignek the Kingak from those of the Okpikruak formation,

S.46°W. fc N.46° E.

I Tiglukpuk Aucella rugosa formation Aucella concentrica Upper Jurassic rocks Amoeboceras (Prwnodoceras) Pseudocadoceras grewingki 8 Cosmoceras castor Aucella sp. (coquina) Aucella rugosa Aucella mosquensis Aucella concentrica Amaltkeus (Pseudoamaltheus)

Middle Jurassic rocks may be present between the Saviukviayak River and the Lupine River

10 0 10 20 MILES Vertical scale exaggerated FIGURE 29. Diagram showing suggested correlation and depositional relations of Jurassic rocks from the Canning River to Elusive Lake. 192 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 and in such localities these units have not been dif­ to Kashivi Creek are similar to those described above, ferentiated. but the reddish-brown-weathering beds of crinoid Lithology. No detailed sections of the Kingak for­ stems and the upper glauconitic sandstone are missing mation were measured by the authors, and for sim­ or not exposed. The thickness of the Jurassic rocks plification the rocks are discussed in three general lo­ was not measured by the authors in this locality, calities: (a) from the Canning River to Kemik but locally in the interstream area between Kashivi Creek, (b) from Kemik Creek to Kashivi Creek, and Creek and Gilead Creek it appears that less than 1,500 (c) from Kashivi Creek to the Lupine Eiver. feet of the Kingak is present. It further appears that The thickness of the Kingak shale from the Can­ in this interstream area the upper rocks of the Kingak ning Eiver to Kemik Creek is indefinitely known. shale were eroded during an interval between the Gryc (oral communication) believed that as much as deposition of either the Kingak and Okpikruak for­ 5,000 feet of Jurassic rocks may be present in the mations or the Okpikruak and Ignek formations. cutbanks on the west side of the Canning River oppo­ Only a few exposures of the Kingak shale are pres­ site the mouth of Cache Creek; in these cutbanks ent from Kashivi Creek to the Lupine Eiver, and these neither the upper nor the lower contact of the forma­ are in cutbanks close to exposures of Triassic rocks. tion is present. The authors believe that on Kemik Four hundred feet of Jurassic strata overlie the Creek, the only locality where the contacts of the for­ Shublik formation on the west fork of the Ivishak mation can be mapped relatively accurately, the Juras­ River; these rocks consist predominantly of shaly sic rocks are no more than 3,000 feet thick. From the siltstone with interbeds and«massive lenses of very Canning River to Kemik Creek the Kingak pre­ hard and dense siliceous siltstone. Pyrite cubes are dominantly consists of black pyritic clay shale and common, and the section weathers rust brown. Fossils shaly siltstone. The shaly siltstone is locally iron of Late Jurassic age (USGS Mesozoic loc. 22745) were stained and the clay shale is coated with a white salt. collected from this section. On the Lupine Eiver Black dense siliceous locally fossiliferous siltstone and where the same type of rocks is exposed, fossils of rust-weathering ironstone are present as beds and Early Jurassic age (USGS Mesozoic loc. 22747) were lenses in the shale. Beds that weather reddish brown collected from beds immediately above the Shublik and contain crinoid stems (USGS Mesozoic Iocs. 24011 formation contact. and 24012; see p. 193) are present near the base of Age. Leffingwell (1919, p. 119-20) assigned an the formation; these beds form rubble which can be Early Jurassic age to the rocks of the Kingak shale traced for short distances in the interstream areas. in the Canning Eiver region, basing the age on the On the Canning Eiver, limy concretions containing identifications assigned to his fossil lots by T. W. carbonized wood, pelecypods, and ammonites (USGS Stanton and Frank Springer. On the basis of the Mesozoic loc. 24035) are present in the shale in the fossils collected by the authors and identified by Ralph middle part of the formation; in this same locality, W. Imlay, it now appears that in addition to rocks of the upper shale beds of the formation contain abun­ Early Jurassic age, the formation also includes rocks dant fossils (USGS Mesozoic Iocs. 24013 and 24014). of Middle and Late Jurassic age. The fossils col­ A glauconitic green friable sandstone with black chert lected by the authors, their localities, and Mr. Imlay's pebbles is present locally near the contact between the identifications are given in the following table.1 Kingak shale and the younger rocks near the Canning Eiver. 1 The name Aucella has been ruled invalid in favor of BucMa by the International Commission on Zoological Nomenclature (Opinion The rocks of the Kingak shale from Kemik Creek 492). This decision was received too late to make modifications herein. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 193

Fossils and localities at which they were collected from the Kingak shale

USOS Meso- Field sample North West Fossil Description of locality zoic locality latitude longitude

22739...... 51 ADt22... 69°23'40" 147°14' east side of Shaviovik River. 22745...... 51 ADt 134.. 69° 148°04'30" bank on east side of Saviukviayak River. 22747...... 51 ADt 144.. 68° 148°12' Lytoceras cf. L. fimbriatum (Sowerby) west side of Lupine River. 22748...... 51 ADt 145.. 68° 148°12' Do. 22759...... 51 AKe 48... 69°14'30" 147°42'30" 22760...... 51 AKe 54... 69°15'30" 147°40' 22763- - 51 AKe 98 ... 69°03' 147°57' kviayak River. 22764...... 51 AKe 113.. 69° 148°04'30" Inoceramus sp. 24011... . 52 AMo4... 69°23'30" 147°03' 24012...... 52AM036-. 69°22'15" 146°25' Plicatula sp. Oxytomal sp. 24013...... 52AMo48._ ' 69°32'30" 146°23' Lima sp. on west side of Canning River. Phylloceras sp. 24014-...... 52AM050-- 69°33' 146°23' Do. Belemnite indet. Amoeboceras (Prionodocera^t) sp. 24028...... 52 AKe 14... 69°24'45" 146°38' 24029...-. .. 52 AKe 15 69°25'10" 146°37'30" Do. 24033 52 AKe 37... 69°27' 146°13'30" Inoceramus sp. River. 24035 ...... 52 AKe 46..- 69°34' 146°23' Pseudolioceras whiteavesi (White). Belemnite indet. Inoceramus sp. Camptonectes sp. Ozytoma sp.

In a written communication to the authors on Janu­ Imlay's identifications indicate that from Kemik ary 28, 1952, Imlay stated that: Creek to the Canning River, rocks of Early Jurassic The Lower Jurassic is definitely represented by lot 22747 age (USGS Mesozoic Iocs. 24011 and 24012) overlie as shown by the presence of Amaltheus which has only been the Shublik formation; that on the Saviukviayak found in the upper part of the Pliensbachian. The Lytoceras Eiver, rocks of Callovian age (early Late Jurassic) has the peculiar, delicate ribbing that is present in L. fimbria­ are present 160 feet above the Shublik formation tum (Sowerby), a species that ranges through the middle (USGS Mesozoic loc. 22745); and that on the Lupine part of the Lower Jurassic in Europe. The Callovian is represented by lot 22745 which contains Eiver, rocks of Pliensbachian age (Early Jurassic) Pseudocadoceras grewingTci (Pompeckj). The species in the immediately overlie the Shublik formation (USGS Cook Inlet area, Alaska, ranges through the middle third and Mesozoic loc. 22747). The authors consider it un­ lower part of the upper third of the Chinitna formation. It is likely that rocks of Early Jurassic age and Middle most common in the middle third which I consider equivalent Jurassic age can be represented in the 160-foot inter­ to the upper part of the Sigaloceras calloviense zone and the entire Cosmoceras jason zone of Europe. The genus ranges val beneath the rocks bearing the fossils of Callovian to the top of the Chinitna formation whose upper third is age on the Saviukviayak Eiver; this and Imlay's age correlated with the Erymnoceras coronatum zone. In Europe assignments, indicate that the Kingak shale in the the genus ranges from the Sigaloceras calloviense zone to the mapped area may be characterized by overlap rela­ Erymnoceras coronatum zone * * *. tionships or unconformities (fig. 29). The upper Oxfordian is probably represented by lot 22759 which contains Aucella concentrica (Sowerby). * * * TIGLTTKPTJK FORMATION In later correspondence, October 1952, Imlay as­ History. The Tiglukpuk formation was named by signed an Early Jurassic age to USGS Mesozoic Iocs. Patton (1956a) for the section "along a series of cut- 24011 and 24012 which "contain the same species of banks on the east side of Tiglukpuk Creek between lat Pentacrinus as occurs at Black Island on the Can­ 68°22' N. and lat 68°22'30" N." Patton stated that: ning Eiver and which are there placed in the Lower Shale, siltstone, and graywacke are the principal components Jurassic on the basis of stratigraphic position"; an of the Tiglukpuk formation. The graywacke is typically a early Bajocian age (early Middle Jurassic) to USGS greenish-gray, slightly calcareous, highly argillaceous, poorly Mesozoic loc. 24035; a Callovian age (early Late sorted sandstone or conglomerate with low porosity and perme­ Jurassic) to USGS Mesozoic loc. 24033; and a late ability. It occurs as poorly stratified lenticular masses in gray silt and clay shale along with a wide variety of silty calcareous, Oxfordian-early Kimmeridgian age (Late Jurassic) to cherty, and ferruginous nodules and concretions. Diverse rock USGS Mesozoic loc. 24014. types are found in the lower half of the formation in subordinate 194 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 amounts. These include bedded chert, siliceous black shale, Shublik formation with little or no angular dis­ variegated shale and siltstone, and a coquinoid limestone com­ cordance. posed largely of compacted specimens of Aucella. Lithology. The Tiglukpuk formation is composed The type section of the formation on Tiglukpuk of a marine unit of shaly siltstone, shale, siltstone, Creek, about 75 miles west of the Sagavanirktok River, conglomerate, and graywacke which interfinger north­ was listed by Patton as follows: ward with the shale of the Kingak. The predominant Stratigraphic rock type is a medium-gray hackly-fracturing shale Approxi- interval measured mate thick- from base of sec­ with blue metallic luster, although black silicified shale tion, in feet Fault. is not uncommon. About 30 percent of the formation Sandstone, siltstone, and shale. Green­ is composed of siltstone and graywacke that are gen­ ish-gray fine-grained graywacke sand­ erally highly argillaceous, noncalcareous, light gray stone in lenticular masses 5 to 40 ft to green, and low in porosity and permeability. The thick, locally calcareous. Interbeds siltstone and sandstone are present as beds and massive of dark-gray shaly siltstone and medium dark-gray siltstone. Minor lenses which pinch out laterally in short distances in calcareous siltstone lenses that weather the shale. The sandstone beds are more abundant in moderate red_.______350 1, 100-1, 450 the upper part of the formation and locally are cross- Predominantly sandstone, siltstone, and bedded and coated with prismatic calcite and siderite. shale as above. Shale locally hackly. Minor lenticular masses of greenish Cherty, ferruginous, silty, and limy concretions and bedded chert and cherty siltstone as nodules are common throughout the rock unit. Con­ much as 20 ft thick in minor amounts. 650 450-1, 100 glomerate is rare and is present only in the lower part Chert and siltstone, greenish to grayish; of the formation near Elusive Lake. Pebbles are sub- glassy bedded chert, greenish to round to angular and black chert constitutes 80 per­ brownish cherty siltstone, and grayish- orange-weathering dark-gray highly cent of the detritus. Locally interbedded with the calcareous siltstone______200 250-450 conglomerate is coquinoid limestone, black silty lime­ Shale and sandstone. Chiefly dark- stone, and botryoidal siltstone concretions that emit a gray shaly siltstone, locally hackly. fetid odor on fresh fracture surfaces. The coquinoid Greenish-gray lenticular masses as limestone is present as beds from a few inches to sev­ much as 30 ft thick of very fine grained graywacke sandstone in subordinate eral feet thick, is composed almost entirely of com­ amounts. Minor dark greenish-gray pressed Aucella sp., and weathers reddish brown. The siltstone. Several coquinoid limestone rock is blue gray on a fresh surface and has incipient lenses as much as 5 ft thick composed cleavage. This lithof acies does not occur east or north chiefly of Aucella sp. Several lenses of greenish chert as much as 10 ft thick. of the Lupine River, and it is best developed in the A few 2- to 6-in. layers of graywacke- lower part of the formation west of Elusive Lake. granule conglomerate. Cherty silt- Locally, however, it is present higher in the formation stone concretions that weather gun- between the Lupine and the Ribdon Rivers. metal blue. Cannonball concretions Measured sections. No complete section of the of siltstone as much as 8 in. in diam­ eter. ______250 0-250 Tiglukpuk formation was measured by the authors. Shublik formation. The Tiglukpuk formation on the Lupine River is known to be at least 1,800 feet thick, but the upper Distribution. The rocks of the Tiglukpuk forma­ part of the formation is not exposed in this locality. tion are present in the foothills from the Lupine West of Elusive Lake it is unlikely that more than River to the western boundary of the mapped area 500 feet of the rock unit could be present between the and as Patton points out, have "been recognized and confining beds of the Okpiruak and Shublik forma­ mapped * * * [as far west as] the Nuka River." From tions; several miles northwest of Elusive Lake the the Ribdon River to the western boundary of the formation is missing entirely. The variation in the mapped area, the folded and faulted strata of the for­ thickness of the formation is probably due mostly to mation crop out in an anticlinorium whose south post-Tiglukpuk erosion but may be due in part to flank is composed of resistant rocks of the Fortress overlap of the Late Jurassic rocks in a southwest Mountain formation and whose north flank consists direction. of rocks of the Fortress Mountain and Torok forma­ Section 5 (pis. 21, 23) was measured in outcrops tions. In the mapped area the Tiglukpuk formation along the Lupine River and one of its small eastern is overlain with probable angularity by the Okpikruak tributaries. The upper beds and the contact of the and Fortress Mountain formations; it overlies the formation with the Shublik formation are covered. GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 195

The rocks of this section are actually transitional be­ Black reddish brown-weathering hackly-fracturing Feet tween those of the Kingak and the Tiglukpuk forma­ sandy shale; massive siltstone lenses and beds; 2-in. beds of black limestone ______200± tions, but they are more like the Tiglukpuk than like the Kingak at the respective type localities. Total measured thickness of Tiglukpuk forma­ tion ______1,800± Tiglukpuk formation, section 5 Shublik formation. Unexposed. Feet Age. The fossils collected from the Tiglukpuk for­ Black clay shale with blue metallic luster and hackly- mation by the authors were identified and assigned a fracturing sandy to shaly siltstone; large dense silt- Late Jurassic age by Ralph W. Imlay. In the only stone nodules and concretions; sandstone and sandy controlled section of the formation measured in the siltstone lenses coated with siderite, pyrite, and mapped area the lowest 200 feet are unfossiliferous. prismatic calcite; fossils are present in the shale beds (USGS Mesozoic loc. 22768) ______1,200± Nevertheless, the authors consider it unlikely that Black brown-weathering fissile locally sandy shale; rocks older than Late Jurassic are represented in the pyrite stringers; spheroidal siderite-coated siltstone Tiglukpuk formation from the Lupine River to the nodules and concretions (USGS Mesozoic Iocs. 22766 western boundary of the mapped area. The fossili- and 22769) ______400± ferous localities and Imlay's identifications are:

Fossils and localities at which they were collected from the Tiglukpuk formation

USGS Meso­ Field sample North West Fossil Description of locality zoic locality latitude longitude

22766...... 51 AKe 135- 68°51' 148°17'30" rugosa (Fiseher) ft above base of formation. mosquensis (von Buch) 22768...... 51 AKe 153- 68°51'50" 148°18'30" above base of formation. 22769 . 51 AKe 154- 68°51' 148°18' mosquensis (von Buch) ft above base of formation. rugosa (Fiseher) Ammonite fragment 22746 51 ADt 136- 68°52' 148°06' 22749 . 51 ADt 149- 68°49'30" 148°21' west of Lupine River. 22750 51 ADt 151- 68°49'45" 148°22' Lupine River. 22751 51 ADt 152.. 68°50' 148°20'30" mosquensis (von Buch)

In a written communication in January 1952 Imlay CRETACEOUS SYSTEM stated: LOWER CRETACEOUS SERIES Many of the Jurassic fossil collections that were made * * * OKPIKRTIAK FORMATION are of middle to upper Kimmeridgian or lowermost Port- landian age on the basis of several species of Aucella includ­ History. The Okpikruak formation was named by ing rare A. concentrica (Sowerby) and abundant A. rugosa Gryc, Patton, and Payne (1951, p. 159) for the rocks (Fiseher) and A. mosquensis (von Buch). The Russian typified by the section along the Okpikruak River. geologists have shown that Aucella concentrica ranges through They stated: the upper Oxfordian and Kimmeridgian, and A. rugosa and A. mosquensis range through the middle and upper Kim­ * * * The type section lies in the middle of a major syn- meridgian into the lowermost Portlandian (Pavlow, 1907: cline and is exposed on a small tributary of the Okpikruak Soc. Imp. Nat. Moscow, mem. v. 17, table opposite p. 84) not River at about lat 68°34'30" N. and long 153°38' W. The higher than the zone of Zaraiskites albani (See Arkell, 1946: formation crops out in the southern part of the Arctic foot­ G.S.A. Bull. v. 57, p. 24-26; Spath, 1936: Medd. om. Gronland, hills province from the Itkillik River west to the Kukpowruk Bd. 99, no. 3, p. 167). A. mosquensis in Europe is not known River. In the Arctic foothills province, as far as known, it below the zone of Subplanites wheatleyensis. I doubt whether rests on Jurassic or Triassic rocks with little or no angular the Portlandian is represented in the collections from northern discordance. At its type locality it is about 2,400 feet thick Alaska. At least lots 22766 and 22769 which contain A. con­ * * *. It is predominantly fine-grained greenish-gray sand­ centrica in association with A. mosquensis and A. rugosa rep­ stone of the graywacke type, dark clay, and silt shale with resent some part of the middle or upper Kimmeridgian. The minor amounts of conglomerate near the base. On the Sik- other lots (22768, 22746, 22749, 22750 and 22751) containing sikpuk River, where part of the formation is well exposed, only A. mosquensis and A. rugosa could not be younger than it is 1,850 feet thick. Here it is characterized by a rhythmic basal Portlandian if the ranges of these species are the same alternation of fine-grained sandstone, silt shale, and clay as in Europe. shale. This alternation is not well developed in the forma- 196 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 tion along the Okpikruak River, although there is a sugges­ The total thickness of the Okpikruak formation east tion of it. of the Lupine River is not known, but presumably it Distribution. In the area mapped the Okpikruak varies from one place to another depending upon the formation crops out discontinuously in the foothills amount of post-Okpikruak erosion. On the east side from the Canning River to the Sagavanirktok River. of Kemik Creek between lat 69°24' N. and lat 69°25' In part of this area, a considerable thickness of the N., a composite incomplete section (section 11) 720 formation has been eroded, and locally younger for­ feet thick was measured in two cutbanks. In the mations rest uncomformably on Jurassic rocks. southernmost cutbank, the measured strata form the From the general vicinity of the Lupine River east gently south-dipping flank of a west-plunging syn- to the Canning River, the nonresistant rocks of the cline, and the upper beds of the formation have been Okpikruak formation are exposed in scattered out­ eroded. In the other cutbank, the measured strata crops in much the same fashion as those of the Kingak dip 20° to 64° S. on the upthrown block of a reverse shale. The two formations are not always dis­ fault; the upper beds of the formation have been tinguishable one from the other and locally they have faulted out. In the southern cutbank, the Kemik been mapped as undifferentiated. From the Lupine sandstone member overlies the Kingak shale with no to the Canning Rivers the Okpikruak formation is apparent angular discordance. differentiated from the underlying Kingak shale by the presence of fossils and the rhythmic alternation Okpikruak formation, section 11 Unexposed. Feet of shale and siltstone. From the Echooka River to Principally nodular clay and platy shaly siltstone coated the Kavik River, the contact between the two forma­ with a white or yellow salt; siltstone beds in rhythmic tions is locally discernible, for in this part of the alternation with the shale; light-brown to gray nod­ mapped area 220 feet of sandstone, which the authors ules and concretions of dense silicified fossiliferous tentatively assign to the Okpikruak formation, over­ limy siltstone and noncalcareous ironstone (USGS Mesozoic loc. 22757; see p. 197); fossils are partly lies the Jurassic shale. This sandstone unit of Early pryitized ______500 Cretaceous age (p. 198), here named the Kemik sand­ Kemik sandstone member: stone member, forms faulted rubble ridges in the Quartzose fine- to medium-grained sugary-textured interstream areas and apparently pinches out both light-gray sandstone; the rocks are slightly argil­ to the west and east. laceous, noncalcareous, and well indurated; the sandstone (examined in thin section) is com­ West of Elusive Lake, the rocks of the Okpikruak posed of 75 percent subangular grains of quartz, formation form resistant mesas, and here the sand­ 23 percent chert and rock fragments, 2 percent stone and conglomerate that constitute part of the phosphate, and a trace of limonite, leucoxene, rock unit are not always distinguishable from those and chlorite; the base of the member consists of of the overlying Fortress Mountain formation. How­ several thin layers of rusty-weathering quartz- grit conglomerate; USGS Mesozoic Iocs. 24008 ever, the rhythmic alternation that characterizes the and 24009 ______220 formation from the Lupine to the Canning Rivers also typifies the Okpikruak sections west of Elusive Total measured thickness of Okpukruak forma­ Lake, and is lacking in the Fortress Mountain sections. tion ______720 Lithology. From the Lupine to the Canning Rivers Kingak shale. the Okpikruak formation principally consists of dark West of Elusive Lake the rocks of the Okpikruak nodular and earthy clay shale and shaly siltstone formation are more coarsely clastic than those which coated with a white or yellow powdery salt. Light- crop out east and north of the Lupine River; the for­ brown to gray dense siltstone and ironstone are pres­ mation comprises alternating beds of dense siltstone ent as lenses in the alternating beds in the shale. The and sandstone of graywacke type, and to a lesser dense siltstone and ironstone lenses are pyritized; the degree, shaly siltstone and conglomerate. The sand­ siltstone lenses are commonly fossiliferous and their stone, in sharp contrast with the Kemik sandstone surfaces weather rust brown. The only sandstone unit member, is a typical graywacke which (in thin sec­ in the Okpikruak formation between the Lupine and tion) is composed of angular grains of quartz (10 the Canning Rivers is at the base, between the Echooka percent), chert, schist, and igneous fragments (33 and the Kavik Rivers; the type section of this, the percent), microcline and andesine (12 percent), a Kemik sandstone member, is on Kemik Creek (section trace of titanite and leucoxene, and a matrix of seri- 11, pi. 23). cite, chlorite, silt, and clay (45 percent). GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 197 Two sections of the Okpikruak formation were 68°40'50" N. The measured strata form the steeply measured west of Elusive Lake: section 3, which in­ south dipping north flank of a west-plunging syn- cludes about 1,500 feet of the lower part of the for­ cline. The contact of the formation with the over­ mation, and section 2 which constitutes the upper 884 lying Fortress Mountain formation was not seen and feet of the formation. The two sections cannot be the lower part of the formation is unexposed owing correlated and the total thickness of the formation to a high-angle reverse fault. The unfossiliferous west of Elusive Lake is not known. section comprises alternating beds of dirty graywacke- At Elusive Lake (section 3) the Okpikruak forma­ type sandstone, siltstone, and shaly siltstone. The tion overlies the lower part of the Tiglukpuk forma­ sandstone is, for the most part, fine grained, argil­ tion; the upper beds of the formation have been laceous, noncalcareous, and dark gray; it is present eroded. The 1,500-foot section is exposed as a scarp in beds 1 inch to 15 feet thick. Nonpersistent con­ facing the west side of Elusive Lake near lat 68°41' N., glomerate lenses with black and green angular chert between long 148°27' W. and 148°29' W. The section granules and pebbles are present in the upper beds. comprises alternating beds of dense medium-gray The siltstone and shaly siltstone constitute approxi­ siliceous siltstone and fine- to medium-grained gray mately 50 percent of the total measured section. The to green graywacke. The siltstone beds are several siltstone is dark gray, hackly fracturing, and locally inches to a foot thick and the sandstone beds are 2 to fissile; it contains minor pyrite nodules and limy con­ 4 feet thick. Shaly siltstone constitutes about 20 per­ cretions. cent of the section. The base of the section contains Age. The fossils collected from the Okpikruak for­ siderite- and calcite-coated rusty-weathering nonlimy mation were examined and identified by Ralph W. siltstone concretions and nodules; the rocks in the Imlay (written communication). He assigned the lower part of the formation are slaty. The section is fossils, except those too fragmental for precise deter­ unfossiliferous. mination and those of long-ranging habit, to the Section 2 is exposed in cutbanks along Section lower part of the Neocomian stage of the Early Cre­ Creek, a small incised tributary of the Sagavanirktok taceous. The fossiliferous localities and Imlay's iden­ Kiver drainage system, between lat 68°40'20" N. and tifications are listed below.

Fossils and localities at which they were collected from the Okpikruak formation

USGS Meso- Field sample North West Fossil Description of locality zoic locality latitude longitude

22738.-.. 51 ADt 18 69°24'30" 147°15' okensis Pavlow River. Belemnite fragment 22740.. 51 ADt 33 69°26' 147°12' Limy lenses and concretions in cutbank on east side of Kemik Creek in beds believed to be correlative with 500-ft thick shale section overlying Kemik sandstone member of type section. 22741...... 51 ADt 49... Do. 22742...... 51 ADt 50... Do. 22744...... 51 ADt 94... 69°15'15" 147°49' 22757 51 AKe 23 69°25'30" 147°12' subokensis Pavlow lies Kemik sandstone member in cutbank along Kemik Creek. 22761...... 51 AKe 76... 69°11'20" 147°45'30" ern tributary of Kashivi Creek. 22762...... 51 AKe 77 fourth mile north of cutbank of USGS Mesozoic loc. 22761. 22765.. 51 AKe 128.. 68°56' 148°15'30" subokensis Pavlow River. 22767.- 51 AKe 139.. 68°54'15" 148°19' River. 24008...... 52 AMo8 _ 69°25' Plicatula sp. Creek. Rhynchonellid brachiopod 24009...... 52AMo2... Do. 24010...... 52 AMo 3 ... 69°24'30" 147°15' 24026...... 52 AKe 2.... 69°27'10" 146°56' of small tributary of Fin Creek. 24030...... 52 AKe 16...... do...... tary of Juniper Creek in beds underlying Ignek formation. 24031...... 52 AKe 33... 69°31'15" 146°24' subokensis Pavlow Canning River in beds underlying upper member of Ignek Camptonectes sp. formation. Belemnite indet. 198 EXPLORATION OP NAVAL PETROLEUM EESERVE NO. 4, ALASKA, 1944-53

Stratigraphic Imlay, on the basis of comparison of its Aucella Approxi- interval measured mate thick- from base of sec- faunules with those in Russia and Siberia, considered ness, in feet tion, infect (written communication, 1956) that the Okpikruak Conglomerate and sandstone Con. formation, in the Shaviovik and Sagavanirktok Elvers stone, mafic igneous rock, and pink region, represents only the Berriasian and Valan- gneissoid granite. Dark greenish- ginian stages. gray fine- to coarse-grained lenticular thick-bedded graywacke sandstone. _ 500 9, 680-10, 180 The Berriasian is represented in USGS Mesozoic Sandstone and conglomerate. Dark- Iocs. 22757, 22762, 22765, 22738, 24031 by Aucella green fine- to medium-grained medi­ okensis Pavlow, A. subokensis Pavlow, the lower um-bedded to massive sandstone. Valangian in USGS Mesozoic Iocs. 22742, 22744, Medium-green massive pebble con­ 22761 by A. sublaevis Keyserling, and the middle to glomerate. Pebbles similar to above but no gneissoid granite. Minor upper Valanginian in USGS Mesozoic loc. 22767 by interbeds of dark-gray silt shale and A. crassicollis Keyserling. siltstone. Section partly covered- __ 490 9, 190-9, 680 Imlay (written communication, 1955) believed that Shale, sandstone, and siltstone. Dark- the fossils in USGS Mesozoic Iocs. 24008 and 24009, gray clay and silt shale. Interbedded which were collected from the Kemik sandstone mem­ medium-green very fine grained thin- to medium-bedded sandstone. Dark- ber, are nondiagnostic as to age. Inasmuch as these gray to green siltstone. Section lots contain the only fossils collected from the Kemik partly covered. ______600 8, 590-9, 190 sandstone member, its age is not precisely known. Shale, dark-gray clay and silt shale. The sandstone unit overlies strata of Jurassic age and Calcareous siltstone concretions. Sec­ tion poorly exposed- ______1, 260 7, 330-8, 590 underlies strata bearing fossils which Imlay assigned Conglomerate and sandstone. Green, to the Cretaceous (Berriasian, USGS Mesozoic loc. yellow-red weathering, massive, len­ 22757). Although it lacks definitive criteria, the au­ ticular chert-pebble conglomerate. thors believe that the sandstone member more logically Medium-green fine- to coarse-grained sandstone with scattered chert peb­ belongs to the Cretaceous system than to the Jurassic. bles. Minor interbeds of dark-gray shale and siltstone. Section partly FORTRESS MOUNTAIN AND TOROK FORMATIONS 310 7, 020-7, 330 Shale, siltstone, and sandstone. Dark- The Fortress Mountain and Torok formations are gray clay and silt shale with calcare­ considered jointly in this report. The relationships ous, ferruginous, and siliceous silt- between the two formations are not known definitely. stone concretions. Dark-gray to In early work (Gryc, Patton, and Payne, 1951, p. green very fine to fine-grained me­ dium-bedded sandstone. Section 160), the two formations were considered one map- poorly exposed- ______1, 720 5, 300-7, 020 pable unit, the Torok formation; however, Patton Sandstone and conglomerate. Me­ (1956b) later recognized the need for two formation dium- to dark-green very fine to names for these rocks and revised the earlier nomen­ fine-grained medium-bedded to mas­ sive sandstone with scattered chert clature. pebbles. Lenses 6 in. to 5 ft thick History and type sections. The Fortress mountain of green chert-pebble conglomerate. formation was named by Patton (1956b), "from the Minor interbeds of dark-gray shale 880 4, 420-5, 300 exposures on Fortress Mountain (lat 68°34/30// N., and dark-gray to green siltstone- __ Shale, siltstone, and sandstone. Dark- long 152°58' W. * * *) where it is typically exposed gray clay and silt shale. Dark-gray and where it was first studied in detail." For a type siltstone. Medium-green to gray section, Patton (p. 219) reported "a composite of several very fine grained medium-bedded partial sections exposed nearby along the Kiruktagiak to massive calcareous sandstone. River and on Castle Mountain. * * *" Patton's type Section partly covered. ______950 3, 470-4, 420 section is given below. Shale, dark-gray clay and silt shale with numerous calcareous, siliceous, Stratigraphic Approxi- interval measured and ferruginous siltstone concretions. mate thick- from base of sec- ness, in feet tion.infeet Minor interbeds of dark siltstone and Top of Castle Mountain. light-green to gray, very fine grained, Conglomerate and sandstone. Dark thin- to medium-bedded calcareous greenish-gray very thick bedded peb­ sandstone. Section partly covered. 1, 050 2, 420-3, 470 ble and cobble graywacke conglome­ Shale, siltstone, sandstone, and con­ rate that weathers moderate yellowish glomerate. Dark-gray clay and silt brown. Pebbles and cobbles are 60 per­ shale and dark-gray siltstone. Me­ cent chert and the rest limestone, sand- dium dark-green, very fine to coarse- GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 199

Stratigraphic Approxi- interval measured Distribution. The Fortress Mountain formation mate thick- from base of sec- ness, in feet tion, in feet crops out in the southern part of the Foothills prov­ Shale, siltstone, sandstone, and con­ ince from the Eibdon Eiver to the western edge of glomerate Continued the mapped area, thence (Patton, 1956b) "west beyond grained, thin- to medium-bedded the Kukpowruk Eiver." It does not crop out and sandstone with occasional chert gran­ probably is not present north of lat 68°55' N. West ule or pebble. Dark-green thin- to medium-bedded lenticular chert-gran­ of Elusive Lake, the formation forms mesas and bluffs ule and pebble conglomerate. Sec­ which rise in bold relief above the surrounding coun­ tion partly covered--______--_.___ 410 2, 010-2, 420 try. Its strata, depending upon the amount of post- Sandstone and conglomerate. Me­ Tiglukpuk and post-Okpikruak erosion, locally overlie dium-green fine- to coarse-grained the Okpikruark formation, the Tiglukpuk formation, medium-bedded to massive sand­ stone. Inoceramus sp. Green len­ and, at one locality about a mile northwest of Elusive ticular chert-granule and pebble Lake, the Shublik formation. The contact of the conglomerate. Minor interbeds of Fortress Mountain formation with younger rocks is dark clay shale and silt shale.-___ 270 1, 740-2, 010 not exposed in the mapped area; which formation Shale, sandstone, and siltstone. Dark- directly overlies the rock unit is not known. gray clayey shale with numerous sep- tarian calcareous siltstone concre­ The Torok formation crops out only in a few iso­ tions. Seventy-five ft of medium- lated cutbanks in a low gravel-covered outcrop belt green to gray thin- to medium-bedded that extends from the Ivishak Eiver to the west side very fine grained sandstone and dark- of the Sagavanirktok Eiver. The formation does not gray siltstone near middle of section. Section partly covered ______570 1, 170-1, 740 crop out east of the Ivishak Eiver and probably was Shale, sandstone, and siltstone. Dark- not deposited there. The formation's outcrop belt lies gray clay and silt shale with a few to the north of the outcrop belt of the Fortress Moun­ septate calcareous siltstone concre­ tain formation; west of Eibdon Eiver the strata of tions. Light-green thin-bedded very the two are separated by a reverse fault. The contact fine grained sandstone and gray silt- stone. Section partly covered______650 520-1, 170 of the Torok formation with the overlying Tuktu Shale, dark-gray clay shale with lenses formation of the Nanushuk group was not seen by of gray silty limestone and septate the authors, but the strata of the two formations are calcareous siltstone concretions. probably conformable. As the contact of the Torok Section partly covered.______520 0-520 formation and older rocks is not exposed in the Tiglukpuk formation. mapped area, which formation directly underlies it The Torok formation, as originally defined by Gryc, is not definitely known. The authors believe, how­ Patton, and Payne (1951, p. 160), included the rocks ever, that east of the Eibdon Eiver it is underlain by later defined by Patton (1956b) as the Fortress Moun­ the Okpikruak formation. tain formation (this report, p. 198); in addition it also The exact relation between the Fortress Mountain included a 6,000-foot section, composed mostly of shale, and Torok formations cannot be established, inasmuch along a tributary of the Chandler Eiver near Castle as the nature of the contacts between the Fortress Mountain. Patton (1956b) limited the name Torok Mountain and younger formations and between the to the rocks characterized by the 6,000-foot shale sec­ Torok and older formations are not known. Patton tion along the tributary of the Chandler Eiver. The (1956b) stated that the megafossils of the two forma­ exact location of the type section is "along the Chan­ tions, in the area west of that mapped by the authors, dler Eiver and Torok Creek between lat 68 °40' N. "are approximately of the same age, but the micro- and 68°43'45" N." faunas are [of] somewhat different [ages] * * *. The Torok formation was described by Patton as con­ [Presumably the Torok formation] is underlain by sisting of 1,500 feet of "dark-gray silt shale and clay the Okpikruak formation and perhaps by a part of shale with subordinate amounts of fine-grained gray- the Fortress Mountain formation." Although there wacke sandstone * * * [overlain] by 700 feet of dark is no definite evidence, for the purposes of this report greenish-gray graywacke sandstone locally containing the authors postulate that the Torok formation is, in thin lenses of chert-granule conglomerate * * * part, a northerly time-equivalent of the Fortress [which is in turn overlain by 3,800 feet] of dark-gray Mountain formation, and in part, younger. The clay shale with intercalated beds of dark-gray silt postulated depositional relations between the two for­ shale and greenish-gray siltstone." mations are shown diagrammatically on figure 30. 200 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

sw. NE-

20 MILES

exaggerated

FIGURE 30. Diagram showing suggested correlations and depositional relations of various stratigraphic units of Mesozoic age from the Canning River to Elusive Lake. Lithology and measured sections. The Fortress measured strata form the south limb of a west-plung­ Mountain formation is a coarse clastic unit consisting ing anticline and overlie shale of the Tiglukpuk for­ of an interbedded succession of marine sandstone, silt- mation. The upper strata of the formation have been stone, shaly siltstone and clayey shale, and conglom­ eroded. erate. The conglomerate and sandstone are both of Fortress Mountain formation, section 4 the graywacke type and the detritus consists of black Feet Dark-gray to green brown-weathering medium- to thick- and green chert, feldspar, and angular mafic igneous bedded sandstone; black chert-granule graywacke con­ rock fragments in a green mudstone matrix. The glomerate with shale inclusions 100 sandstone and conglomerate are typically low in poros­ Interbedded dark-gray to green sandstone; conglom­ ity and are impermeable. The conglomerate occurs eratic sandstone with black chert granules; shaly as large masses and discontinuous lenses. Locally the siltstone ______1,600 Graywacke sandstone, siltstone, and shaly siltstone 485 sandstone contains shale lenses and carbonized wood Interbedded graywacke conglomerate, sandstone, and fragments. The siltstone is typically gray or green siltstone ______100 and locally siliceous. The clay shale and shaly silt- Interbedded siltstone, conglomeratic sandstone, and stone are medium gray and locally contain pebbles shaly siltstone; granules are mostly black chert set of green and black chert. The formation is charac­ in a green sandstone matrix; sandstone mostly dark gray, very fine to medium grained, argillaceous and terized by a wide variety of calcareous, ferruginous, slightly calcareous, in beds as much as 4 ft thick; argillaceous, and siliceous nodules, concretions, and siltstone dark gray, dense, in beds as much as 6 ft lenses. The Fortress Mountain formation is generally thick; lenses of conglomerate 500 unfossiliferous and contains no reliable horizon mark­ Black shaly siltstone and soft clay shale with a few ers. The thickness of the entire formation in the siltstone interbeds _ _ 170 mapped area is not known, but west of Elusive Lake Total measured thickness of Fortress Mountain it exceeds 2,955 feet. formation 2,955 The Torok formation comprises interbedded medium- Tiglukpuk formation. gray platy and locally fissile shaly siltstone, and, in No sections of the Torok formation were measured, lesser amounts, finely laminated siltstone. The silt- and it is unlikely that more than several hundred feet stone beds are 2 inches to a foot thick and the rocks of the unit crops out at any one locality in the area weather light brown. Brown-weathering siltstone con­ mapped. Isolated exposures of the formation are cretions are common. The formation is essentially unfossiliferous, although locally Inoceramus sp. is present along a small western tributary of the Ivishak present. Eiver at lat 69°00'15" N., between long 148°11' W. Only one section of the Fortress Mountain forma­ and 148° 14' W.; there the Torok strata strike and dip tion was measured by the authors. This section (sec­ about the same as the overlying beds of the Nanushuk tion 4, pis. 21, 23) is exposed in a steep east-facing group. The several hundred feet of Torok formation cliff about 3 miles northwest of Elusive Lake. The that is exposed comprise fissile shaly siltstone and GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 201 brown-weathering siltstone in beds from 2 inches to Chandler, and the Ninuluk crop out in the area 1 foot thick. Large brown-weathering siltstone con­ mapped by the authors. cretions are present in the shale; one poorly preserved Type sections. ^Detterman (1956, p. 234) reported Inoceramus sp. was found. the type section of the Tuktu formation to be "at Tuktu Bluff on the north side of the Chandler River LOWER CRETACEOUS AND UPPER CRETACEOUS SERIES at the point where the river cuts the escarpment * * * lat 68°44' N., long 152°18' W." The formation is NANUSHUK GBOUP described (p. 235) as consisting of 1,030 feet of: History. The name "Nanushuk," taken from the "dirty green to greenish-gray very fine to fine-grained Nanushuk Eiver, was originally applied by Frank C. sandstone; much of the sandstone borders on siltstone. Schrader to a rock "series" along a part of the Anak- Siltstone and silt shale form a subordinate but im­ tuvik and Colville Rivers in northern Alaska. Gryc, portant part of the formation. The sandstone is com­ Patton, and Payne redefined these rocks (1951, p. 162) monly thin bedded, but in places is more massive and and assigned the name "Nanushuk" "to a group of cliff forming. It is commonly calcareous, highly ar­ rocks * * * exposed along the Nanushuk River where gillaceous, and in places micaceous. Small ironstone the river cuts across the Arctic Foothills province of nodules are commonly found throughout the forma­ northern Alaska." They further divided the group tion, particularly in the siltstone-silt shale units." into two formations: "[(a)] the Chandler (non- The type section of the Killik tongue of the Chan­ marine), which tongues into the [(b)] Umiat (ma­ dler formation was reported by Detterman (p. 237) rine) to the north." Detterman (1956) redefined the to be "along the east bank of the Killik River between group and further modified the nomenclature by di­ lat 68°52' N. and 68°55' N. and long 153°26' W." viding the rocks into four formations: "the Tuktu The formation is described (p. 238-239) as comprising formation (marine, no nonmarine equivalents) at the two parts: the lower, 1,095 feet thick, consists of base; the Grandstand and Ninuluk formations, marine; "characteristic thick-bedded, bluff-forming sandstones and the Chandler formation (nonmarine) which inter- * * * [and] grayish, micaceous, carbonaceous siltstone tongues with and grades into the two upper marine and silt shale with numerous thick coal seams * * *; formations." Detterman subdivided the Chandler for­ [the upper, 1,720 feet thick,] is characterized by * * * mation into two tongues, the Killik and the Niakogon; massive white quartz conglomerate," sandstone, silt- the relationships of the rock units that he defined are stone, silt shale, and thin seams of coal." shown diagrammatically on figure 31. Of these for­ Detterman (p. 241) described the type section of mations, only the Tuktu, the Killik tongue of the the Ninuluk formation as 657 feet thick and "on the right bank of the Colville River at Ninuluk bluffs 20 S. N. miles downstream from the junction of the Killik and Colville Rivers, lat 69°08' N., long 153°18' W." The formation was further described by Detterman: S o Greenish-gray siltstone, silt shale, and dark blue-gray clay =3 Niakogon ___^^=- 5.2 "S shale constitute about 60 percent of the sequence. Coarse tongue______!^^=- i|l «l elastics account for most of the remainder. Several thick Chandlerformation sandstone units are present near the top of the formation. (nonmarine) Stringers and lenses of grit-pebble conglomerate are present 2 S't=S 0? s 1 Killik ~^^' at intervals throughout the coarser clastic units. The sand­ i tongue ^^^_^^ = EC 1 i s*s stone grades from "salt and pepper" through various shades of g i i-s- gray and yellow red. Most of them have a distinct greenish B'-^-E 3-^2' c cast. Siliceous, argillaceous, and ferruginous concretions are *1I "~t2 "^* commonly associated with siltstone and silt shale units. - _^^ : -»- 'To0 O Distribution. In the mapped area, the Tuktu for­ 1 o mation, the Killik tongue of the Chandler formation, o o i? and the Ninuluk formation have been mapped only at Marmot syncline where these rocks form a mesa which P] GUR]D 31.- Diagrammatic sketch of intertonguing marine a nd n<>n- stands in bold relief above the surrounding country. m ir ine ui lits of the Nanushuk group in the type localities, Colville Riv«;r region, Alaska. Modified from Detterman (1956). However, the Nanushuk group has been mapped also 202 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 as an undifferentiated unit at several localities be­ siliferous (USGS Mesozoic Iocs. 22753 and 22754). tween the Ivishak and the Lupine Rivers. At one of At Marmot syncline 800 feet of the Tuktu forma­ these localities, in cutbanks along the Saviukviayak tion crops out on the east side of the mesa and con­ River, the rocks are part of the Tuktu formation. At sists of interbedded siltstone, shaly siltstone, and the other localities where the Nanushuk group has not silty sandstone. This section (section 1, pi. 23) is been differentiated, probably both the Tuktu and the overlain gradatioiially by the Chandler formation; the Chandler formations are represented. The Nanushuk contact of the section with the underlying Torok for­ group has not been mapped east of about long 148° W. mation is covered. About 60 percent of the unit is The authors mapped as Ignek formation, lower mem­ composed of gray- to rust-brown-weathering siltstone ber, rocks east of long 148° W. believed, for reasons and hackly-fracturing shaly siltstone. Small ferrugin­ stated on page 205, to be equivalent in age to those ous nodules are common near the base. The sandstone of the Nanushuk group (fig. 30). is thin bedded, very fine grained, argillaceous, slightly calcareous, dark gray to green, and, in the lower part TUKTU FORMATION of the section, commonly lenticular. Locally the sand­ Lithology. The several hundred feet of the Tuktu stone is laminated and crossbedded, and worm trails formation exposed in the cutbanks along the Saviuk­ and tubes are present on the bedding planes. Fossils viayak comprise interbedded mudstone, clayey to are abundant near the base of the section (USGS shaly siltstone, and sandstone. The shaly siltstone Mesozoic loc. 22755). constitutes approximately 40 percent of the rock and Age. Only three fossil lots were collected from the is dark gray, micaceous, and carbonaceous. The sand­ Tuktu formation in the mapped area: two from the stone is dark gray with brown-weathered surfaces, cutbanks along the Saviukviayak River, and one from thin to medium bedded, very fine grained, and the lower part of the section at Marmot syncline. The highly argillaceous. The section is abundantly fos- fossils were identified by Ralph W. Imlay.

Fossils and localities at which they were collected from the Tuktu formation

USGS Meso­ Field sample North West Fossil Description of locality zoic locality latitude longitude

22753 61 ADt 112. . 68°04'45" I4s°n3' cf. I. cadottensis McLearn River. 22754...... 61 ADt 113- 68°04'46" 148°03' cf. G. kingi McLearn Inoceramus anglicus Woods 22756...... 51 ADt 178- Arcticaf sp. Plewromya

Only USGS Mesozoic loc. 22754 contains fossils on 2,500 feet thick and consists of nonmarine to near- which definite age determination may be based. These shore sandstone, conglomerate, siltstone, shale, and have been assigned to the Albian stage of the Early coal. Most of the sequence is covered and only the Cretaceous by Imlay (written communication) who resistant conglomerate and sandstone beds are well stated: exposed. The base of the section is a massively The range of Inoceramus anglicus in northwest Europe is bedded, medium-grained salt-and-pepper sandstone middle and upper Albian. It is not known below the middle with estimated fair porosity and permeability. Over­ Albian. Concerning GastropHtes, recent studies show that lying this sandstone is approximately 1,000 feet of the genus ranges throughout the middle Albian and may ex­ more thinly bedded fine-grained argillaceous rusty- tend into the upper Albian. * * * weathering sandstone, shaly siltstone, and gray-green Detterman (1956, p. 234) stated that Imlay's work crossbedded siltstone and minor coal. indicates that in the type section the characteristic The upper 1,500 feet of the measured section con­ fossils are of middle Albian age. sists of interbedded sandstone, conglomerate, siltstone, coal, and shale, of which sandstone and siltstone make CHANDLER FORMATION (KILLIK TONGUE) up the bulk of the unit. The resistant ledge-forming Lithology. The Killik tongue of the Chandler for­ conglomerate is composed of as much as 30 percent mation was recognized only at Marmot syncline where rounded white quartz grains, and black, gray, and the formation gradationally overlies the Tuktu forma­ green chert with a few pebbles of limestone of Missis- tion and gradationally underlies the Ninuluk forma­ sippian age. The sandstone is medium grained and tion. The sequence (section 1, pi. 23) is approximately fairly clean; it has a salt-and-pepper appearance and GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 203 rust-brown-weathered surfaces. The siltstone is thin sandstone; and an upper member, predominantly of bedded, medium grained, and stained with limonite. shale with lesser sandstone and siltstone beds, char­ Ironstone nodules and concretions are present through­ acterized by pyroclastics. Although the evidence is out the 1,500 feet. not conclusive, the authors believe (see p. 38) that Age. The Killik tongue of the Chandler formation the age of the lower member is Early Cretaceous, that is unfossiliferous at Marmot syncline. However, it the age of the upper member is Late Cretaceous, and gradationally overlies the Tuktu formation of middle that the two members are separated by an erosional Albian age and is probably overlain gradationally by break. Over much of the mapped area the contact the Ninuluk formation, which in the type locality between the two members is covered, and, for this (Detterman, 1956, p. 242) contains "abundant speci­ reason and because of the complexity of the folding mens of Inoceramus dunveganensis McLearn, which involving the two units along part of their contact are of late Cenomanian age." It seems logical there­ zone, they have been mapped locally as undiffer- fore that the age of the Killik tongue of the Chandler entiated. formation is middle or late Albian. The rocks mapped as Ignek formation were for­ merly mapped as the Nanushuk and Colville groups NINULUK FORMATION (Payne and others, 1951). The lower member of the Lithology. The Ninuluk formation was recognized Ignek formation is probably equivalent at least in only at Marmot syncline where about 100 feet of the part to the Nanushuk group, and the upper member formation forms the top beds. At this locality the is probably equivalent at least in part to the Colville sequence comprises thin-bedded fine-grained highly group (an Upper Cretaceous unit which crops out argillaceous green slightly calcareous sandstone, silt- west of the mapped area). However, although there stone, and shaly siltstone shale; it is unfossiliferous. are lithologic similarities in these rock units, the de­

IGNEK FORMATION scriptions of the type sections of the Nanushuk and Colville groups are not applicable to the Ignek for­ History. The Ignek formation was originally de­ mation. fined by Leffingwell (1919) in his report on the Can­ LOWER MEMBER ning River region in which he stated (p. 120): Distribution. The lower member of the Ignek for­ The Ignek formation consists of about 2,500 feet of black mation crops out in cutbanks along the west side of shales with coal or "red beds" and subordinate sandstone the Canning River north of Shublik Springs, along members. It probably overlies the Kingak shale. * * * The formation occurs at both ends of the Sadlerochit Mountains Gilead Creek, and along the west side of the Ivishak and probably along the northern front. * * * The type locality River. The strata of the lower member form the limbs is on the south side of Red Hill, in the Ignek Valley at the of the syncline between the Kavik River and Juniper west end of these mountains. Creek, of the one on the east side of Gilead Creek, Leffingwell (p. 120) listed the type section at Red and of the faulted synclinorium between Gilead Creek Hill as follows: and the Ivishak River. The lower member also is Feet exposed in cutbanks along Fin Creek, Juniper Creek, Blue-gray fine-grained sandstone ______200 Black shales, with red bed near the top; fauna of lo­ and the Kavik River, but in these localities, it could cality 3 ______1,500 not be mapped separately from the upper member. Unexposed ______400 The lower member rests unconf Qrmably on the Okpik­ Gray sandstone, weathering yellow ______100 ruak formation and, depending upon the amount of Unexposed ______400 post-Okpikruak-pre-Ignek erosion, locally overlies the Kingak shale. 2,600 Lithology. The lower member of the Ignek forma­ It is not clear what stratigraphic interval Leffing­ tion generally ranges in thickness from 2,590 feet on well intended that the Ignek formation represent. For the Ivishak River to 1,000 feet on the Canning River. the purposes of this report, the authors have retained The variance in thickness probably is due partly to the name Ignek but have redefined the formation as erosion during the time between deposition of the those strata which, from the Ivishak to the Canning lower member and of the upper member, but it may River and east, unconformably overlie the Okpikruak be due also to progressive overlap of the younger beds and Kingak formations and underlie the Sagavanirk- of the lower member on the older beds in a general tok formation. The formation consists of two parts: northeasterly direction. a lower member of siltstone, shale, and dirty to rela­ The lower member of the Ignek formation com­ tively clean subgraywacke-type locally fossiliferous prises sandstone of subgraywacke type, siltstone, shale, 204 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 and, less commonly, conglomerate. The sandstones Interbedded massive crossbedded fine-grained sand­ Feet are locally crossbedded, ripple marked, and charac­ stone, siltstone, and shaly siltstone 80 Covered interval; some rubble of rocks as above 260 terized by curly bedding or hassock structure. They Dark-gray highly micaceous carbonaceous argillaceous, range from thin-bedded carbonaceous fine-grained fine- to locally coarse-grained sandstone; iron-stained rocks to reddish-orange-weathering medium-grained siltstone and shaly siltstone 190 salt-and-pepper rocks. Most of the sandstones have Covered interval; rubble of rocks as above 760 low porosity and permeability, but some are estimated Dark-gray dirty carbonaceous micaceous sandstone; to be moderately porous and permeable. The sand­ weathers in large rectangular blocks; macerated plant remains and limonite-coated concretions 280 stones (examined in thin sections) are composed of Covered interval 70 as much as 65 percent subangular quartz grains and Massively bedded greenish-gray carbonaceous micaceous lesser amounts of chert and rock fragments, plagi- ripple-marked sandstone; limonite-coated concretions; oclase. orthoclase, leucoxene, hematite, pyrite, chlorite, minor shaly siltstone interbeds 400 and sericite. In some of the samples the grains are Covered interval; float of rocks as above 100 moderately well sorted. The siltstone in the lower Contact (arbitrarily placed). member is thin bedded and ferruginous; the shale is Total measured thickness of lower member of medium to dark gray and locally contains blue-gray Ignek formation _____ 2,590 limestone lenses. Macerated plant remains, carbona­ Okpikruak formation. ceous material, coal, and limonite nodules and con­ Approximately 1,500 feet of the lower member of cretions are locally present throughout the rocks of the Ignek formation was measured in a faulted syn­ the lower member. The sequence is not abundantly cline about 5 miles north of the mountains between fossiliferous except in the more northerly sections on the Kavik Eiver and Juniper Creek, where, on the the Canning River. north side of the syncline, the member rests on strata Measured sections. Three sections of the lower bearing fossils of Valanginian age (USGS Mesozoic member of the Ignek formation were measured: one loc. 24030; see p. 197). The section is overlain by between the Kavik River and Juniper Creek, one on a sandstone bed which is probably equivalent to one the Canning River, and one between Gilead Creek and which forms the base of the upper member of the the Ivishak River. The latter 2, sections 8 and 19, Ignek formation on the west side of the Canning are designated the standard sections of the lower mem­ Eiver. The 1,500-foot section comprises iron-stained ber and are illustrated on plate 23. The locations of fine-to-medium-grained argillaceous micaceous, locally the sections are shown on plate 21. ripple-marked sandstone, iron-stained siltstone, and Section 8 was measured on the south flank of a brown-weathering shaly siltstone. Only the sandstone syncline between Gilead Creek and the Ivishak River, is well exposed and it forms resistant ledges similar where the rocks of the lower member unconformably to those of section 8. Macerated plant remains and overlie the Okpikruak formation and the upper beds limonite nodules are present locally in the sandstone of the member have been eroded. About a mile north­ and shale of the measured section, and coal is inter- east of the locality where this section was measured, bedded in thin seams. the same sequence of rocks overlies the Kingak shale. An incomplete section (section 19) of the lower No fossils were found in the measured section. Only member of the Ignek formation was measured along the sandstone is well exposed; it crops out as resistant the west side of the Canning Eiver north of Shublik ledges in much the same manner as that of the Chan­ Springs, where the lower sandstone units of the mem­ dler formation at Marmot syncline. ber form three bluffs that project into the river flats. The strata overlie the Kingak shale; the upper beds Lower member of the Ignek formation, section 8 Feet of the lower member are not exposed. Interbedded carbonaceous micaceous moderately argil­ Lower member of the Ignek formation, section 19 laceous dark-gray very fine grained sandstone, silt- stone, and iron-stained shaly siltstone ______100 Unexposed. Feet Covered interval ______120 "Paper" shale, dark-gray to blue-gray; iron-stained and Thin-bedded ferruginous siltstone; dark-gray iron- locally coated with white or yellow powdery salt. stained shale; very fine to fine-grained micaceous car­ Ironstone and limestone concretions and nodules; mar- bonaceous argillaceous ripple-marked sandstone ___ 140 casite and pyrite nodules; carbonaceous material near Covered interval; some coal and sandstone float ____ 90 base ___ _ 280 GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 205

Feet Peet Sandstone, dark-gray, fine-grained, iron-stained; locally Clay shale, medium-gray; coated with powdery yellow contains white quartz and olive-green chert granules salt; ironstone lenses and concretions 30 and pebbles in thin layers; sandstone cleaner in upper part of unit with some large cross beds; 3-4 in. Total measured thickness of lower member of sandy ironstone concretions; fossils abundant in red- Ignek formation _____-__-______500 weathering sandstone 2 ft from top of unit (USGS Kingak shale. Mesozoic Iocs. 24018 and 24019; fossil lots of the lower member are discussed below) ______75 Age and correlation. The fossils collected from the Sandstone, medium- to dark-gray; in beds 1-3 ft thick; lower member of the Ignek formation were identified medium-grained; locally weathers reddish brown; white quartz and olive-green chert common on bed­ by Ralph W. Imlay. Of the USGS Mesozoic localities ding planes; fossils common in red-weathering beds listed below, 22752 is in beds whose stratigraphic posi­ in upper 4 ft (USGS Mesozoic Iocs. 24016, 24017, and tion in the Ignek formation is not known. Fossil lots 24020) and in base of unit (24015) ______100 Siltstone, dark-gray, hackly-fracturing, thin-bedded; from other localities were collected from beds not weathers reddish brown ______15 higher than 500 feet above the base of the formation.

Fossils and localities at which they were collected from the lower member of the Ignek formation

USGS Meso­ Field sample North West Fossil Description of locality zoic locality latitude longitude

22752...... 51 ADt 101- 69°17' 147°58'30" Red-weathering sandstone beds in cutbank along Qilead Creek. 24016 ...... 52 AMo 44A. Red-weathering sandstone beds 141-145 ft above base of section 19. Arctica? sp. Panope? kissoumi (McLearn) elongatissima (McLearn) 24017...... 52 AMo 45. . Do. Astarte sp. Dilrupa sp. 24018 52 AMo 46. . Red-weathering sandstone beds 218 ft above base of section 19. Tancredia sp. 24019-.. ... 52 AMo 47. . Do. Panope elongatissima (McLearn) 24020...... 52 AMo 53- Same as 24016. 24025 ___ . .... 52AKe4 . 69°29' 146°58' Eopectin? sp. Fin Creek. Braehiopod (aff. Mentzdiopsis) Entolium sp. 24027 52 AKe6 _ . 69°28'30" 147°03' Rust-weathering sandstone beds on hillside east of Fin Creek. Braehiopod (aff. Mentzdiopsis) Entolium sp. 24034...... 52AK644 69°34'30" 146°22'30" Red-weathering sandstone beds in cutbank along west side o Entolium sp. Canning River. Acteon sp. Arctica? sp. Worm burrows

Leffingwell originally assigned a Jurassic(?) age to Imlay stated (written communication, June 7, 1956) the Ignek formation, but believed (p. 124) it "to be that the fossils listed above include species common in younger than the Kingak shale." The authors did not the Tuktu and Grandstand formations. H. R. Berg- visit Leffingwell's type locality of the Ignek forma­ quist (written communication) identified Bathysiphon tion; however, on the west side of the Canning River sp., Ammobaculites sp., Haplophragmoides sp., and several miles north of the outlet of Shublik Springs, Pelosina sp., in samples from the lower member on rocks that he mapped as Ignek formation (section 19 the Kavik River; he stated that "the fauna is of a of this report) overlie rocks of Late Jurassic age general sort that ranges from the Torok formation (USGS Mesozoic Iocs. 24013, and 24014; see p. 193). into the Chandler formation." Between the Kavik Eiver and Juniper Creek, rocks The rocks of the lower member of the Ignek forma­ which are probably approximately equivalent in age tion crop out along the Ivishak River in close proxim­ with those of the Ignek formation on the Can­ ity to rocks bearing the typical fauna of the Tuktu ning River locally overlie rocks of Valanginian age formation (USGS Mesozoic Iocs. 22753 and 22754, p. (USGS Mesozoic loc. 24030; see p. 197); in other 202); parts of the two formations appear to be ap­ localities as far west as the Ivishak River, the Ignek proximately on strike. The Colville group, which formation locally overlies the Kingak and the Okpik- crops out west of the mapped area, is typified both in ruak formations. The age of the lower member of the the lower and upper parts by pyroclastic material Ignek formation as defined by the authors, therefore, which is missing in the lower member but is present is Early Cretaceous or younger. in the upper member of the Ignek formation. For 206 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 these reasons and because of the lithologic similarities, 34' N., consists of about 100 feet of ferruginous light- the authors believe that the lower member of the gray massively bedded, slightly to moderately argil­ Ignek formation is equivalent to the Nanushuk group. laceous, locally carbonaceous sandstone. Locally, peb­ bles of black chert are alined along the bedding UPPER MEMBER planes. Multicolored silicified tuff beds crop out on Distribution. The outcrop belt of the upper mem­ the west side of the Canning River several hundred ber typically is one of low relief; the rocks of the feet higher than the sandstone; this same facies also member crop out in isolated cutbanks. The best ex­ is present on the east side of Juniper Creek where posures are along the lower part of the Canning River about 600 feet of the member crops out along a large and in the icefield areas on the Kavik River and icefield. At this locality the base of the section con­ Juniper Creek near lat 69°30' N. The member also sists of about 40 feet of medium-gray fissile shale crops out on Fin Creek between lat 69°28' N. and with 1-foot thick interbeds of multicolored tuff. 69°30' N., on Fin Creek and on Juniper Creek where Massive calcareous concretions as much as 5 feet in the streams have breached Shaviovik anticline, and diameter are alined along the bedding planes of the probably on the lower part of Gilead Creek. The shale and give off a kerosene odor when freshly basal sandstone and beds of tuff in the lower part of broken. Overlying the lower 40 feet is approximately the member locally form rubble ridges in the inter- 200 feet of silicified tuff in beds 2 to 8 inches thick stream areas, but these persist only for short distances with thin interbeds of bentonitic shale and lenticular and are of little value in defining the unit. concretions. One of these concretions contained the The beds of the upper member overlie the lower pen of a large squid (USGS Mesozoic loc. 24112; see member with unknown attitude. Locally, the lower below). The tuffs are light gray to blue gray and member appears to have been eroded, and on the Can­ weather various hues of yellow, red, green, and ning River the upper member rests directly on rocks orange. About 360 feet of medium-gray fissile and of Berriasian age (USGS Mesozoic loc. 24031; see nodular clay shale with minor interbedded siltstone p. 197). The upper member is overlain by the Saga- overlies the silicified tuffs. vanirktok formation and in most of the area the The upper part of the upper member is exposed beds of the two strike and dip about the same. How- best in isolated cutbanks along the west side of the over, on Fin Creek and on Juniper Creek where the Canning River between lat 69°35' N. and 69°40' N". streams have breached Shaviovik anticline, the rocks This part of the member overlies, by an unknown of the upper member dip more steeply than do those thickness, beds of red ocher which are probably cor­ of the flanking Sagavanirktok formation. relative with the "red beds" of LeffingwelPs type sec­ Lithology. In all the localities where the upper tion and which probably occupy the same approximate member crops out, it is either so poorly exposed or position in the stratigraphic column as the beds of so complexly folded that its thickness cannot be accu­ tuff and bentonite on Juniper Creek. The upper part rately determined. Between Fin Creek and the Shavi­ of the upper member comprises conglomerate, fine- to ovik River the outcrop belt of the combined lower coarse-grained relatively clean salt-and-pepper sand­ and upper members of the formation is approxi­ stone, medium-gray carbonaceous coaly siltstone, and mately 4 miles wide. Comparable structural belts in shaly siltstone. Abundant coaly wood, partly silicified which thicknesses are known seem to indicate that logs, plant remains, and ironstone nodules are present, more than 4,000 feet of the upper member could not and fucoidal and mudflow markings locally charac­ be represented in this area. However, assuming an terize the sandstone and siltstone in this part of the angular discordance between the strata of the upper member. member and the Sagavanirktok formation, additional Age. A questionable Panope sp. from USGS Meso­ beds may be obscured by the depositional lap of the zoic loc. 24032, sandstone beds west of the Canning younger formation. River at lat 69°31' N". and long 146°25' W. was iden­ The upper member of the Ignek formation may be tified by Imlay (written communication). The pen divided into two parts: a lower unit characterized by of a squid that was collected from the concretion in bentonite and beds of silicified tuff and an upper unit the cutbank along Juniper Creek (USGS Mesozoic composed of conglomerate, sandstone, siltstone, and loc. 24112) at lat 69°30'05" N. was identified by John shale. The base of the lower unit, which has been B. Reeside, Jr. In a written communication (1952) identified only in the syncline between the Kavik to the authors he stated: "This specimen is the pen River and Juniper Creek and along the west side of of a large squid. I cannot distinguish it from Teuso- the Canning River between lat 69°30' N". and 69° teuthis longus Logan of the upper part of the Mo- GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 207 brara formation of Kansas and would assign it that and contains rounded pebbles and cobbles of white name and that age. The beds are * * * middle Upper quartz, green and black chert, quartzite, igneous rock, Cretaceous." and silicified tuff lithologically similar to that present In addition to this macrofauna, a microfauna of in the lower part of the upper member of the Ignek Late Cretaceous age was identified by H. R. Berg- formation. The sandstone ranges from light gray to quist (written communication) from samples col­ buff, yellow brown, pink, and red, and locally is mod­ lected in the shale beds which contained the squid- erately porous and permeable. The siltstone is medium bearing concretion on Juniper Creek. This micro- to light gray, slightly calcareous, and friable to semi- fauna includes Spongodiscus sp., Archicorys sp., and consolidated. The coal is thin bedded and of low Dictyomitm sp. rank; it has a dull to waxy luster. Except for one The evidence cited indicates that part of the upper questionable pelecypod impression, no fauna was member of the Ignek formation is Late Cretaceous in found in the formation. The siltstone and shale in- age and that the beds characterized by the squid-bear­ terbedded with the coal do contain a flora, but no ing concretion belong in the Coniacian-Santonian collections were made. The rock unit has been mapped stages. Whether all the Late Cretaceous stages are as the Sagavanirktok formation, partly because of its represented in the upper member is not known, and lithologic similarity to the rock unit described by the authors arbitrarily postulate that the member Gryc, Patton, and Payne (1951, p. 167) and partly ranges in age from Turonian to Maestrichtian (fig. 27). because it can be traced, although somewhat discon- tinuously, to the Sagavanirktok River where the TERTIARY SYSTEM Sagavanirktok formation has been noted. SAGAVANIRKTOK FORMATION Measured sections. Two sections of the Sagavanirk­ tok formation were measured in the mapped area and History. The Sagavanirktok formation was named these are shown on plate 23. The locations of the sec­ by Gryc, Patton, and Payne, who stated (1951, p. tions are shown on plate 21. 167): Section 17 was measured in the area just west of The Sagavanirktok formation crops out in the Franklin the Kavik River where an incomplete sequence about Bluffs, its type locality, along the lower part of the Saga­ 1,600 feet thick is preserved in a broad syncline. The vanirktok River and is also well exposed in the White Hills area. It consists mainly of red-bed-type, poorly consolidated basal conglomerate of the Sagavanirktok formation siltstone, sandstone, conglomerate, and lignite. No fauna overlies the Ignek formation at this locality with no has been found, but the formation does contain an early Ter­ apparent angularity, and the upper beds of the for­ tiary flora. mation have been eroded. The massive sandstone and Distribution. In the northeastern part of the conglomerate beds form resistant ledges which are mapped area the Sagavanirktok formation crops out separated by tundra-covered lowlands. The nature of in broad plunging anticlines and synclines. The more the rocks underlying the tundra has, where possible, resistant sandstone and conglomerate form ledges and been inferred from the character of the material whaleback ridges on the limbs of the structures be­ brought to the surface by frost heaving. tween the Kavik and Shaviovik Rivers. The best ex­ SagavanirJctoJc formation, section posures of the formation are in the interstream area Feet between Fin Creek and the Shaviovik River, where Coarse-grained poorly consolidated light-gray sandstone the rocks form the south flank of the Shaviovik anti­ with a few quartz and chert pebble to granule lenses; cline, and in cutbanks along Fin Creek. The forma­ sandstone weathers light yellowish brown; massive tion is overlain by flat-lying Tertiary and Quaternary crossbeds as much as 4 ft thick; few plant remains and bituminous(?) material ______50 deposits along present stream flood plains, terraces, Mostly tundra covered; small amount of light-brown and hillsides; although the evidence is not conclusive, sandy shale ______120 the authors believe that it is separated from the un­ Clean poorly consolidated light-gray coarse sandstone derlying Ignek formation by an erosional uncon­ and lenses of conglomeratic sandstone; conglomerate constituents are well-rounded white quartz, olive, formity. gray, and black chert, silicified tuff, and a few pebbles LitJiology. The Sagavanirktok formation consists of quartzite; massive crossbedding in upper part of of nonmarine to beach-type sediments consisting of unit; plant remains and thin beds of low-grade coal in poorly consolidated conglomerate, sandstone, and silt- lower part 40 stone with interbeds of shale and coal. The conglom­ Mostly tundra covered; some fine-grained sandstone and gray shale _ 290 erate crops out as lenticular masses, grades laterally Poorly consolidated buff to light-gray sandstone and con­ into crossbedded massive coarse-grained sandstone, glomerate similar to that described above ______50 208 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

Feet Low-rank coal with blocky fracture and dull to waxy Feet Tundra covered ______70 luster; coal seams as much as 2 ft thick; interbeds Poorly consolidated conglomerate and coarse light-gray of light-gray clay shale and siltstone; plant remains 20 to buff sandstone; sand grains are subround quartz Sandy light-gray shale and dark shale containing car­ and chert; the pebbles in the conglomerate are well bonaceous fragments and plant remains _ 100 rounded and comprise white quartz and minor chert Yellowish-brown medium-grained friable crossbedded and tuff ______60 sandstone; minor lenses of conglomerate containing Mostly tundra covered; some sandy shale ______230 rounded pebbles of chert, tuff, and white quartz 70 Friable coarse-grained light-gray massive sandstone, and Massive beds of sandstone and lenses and beds of con­ conglomerate containing rounded pebbles and cobbles glomerate as much as 15 ft thick; conglomerate con­ of white quartz, chert, and tuff; conglomerate ce­ tains pebbles and cobbles of rounded white quartz, mented with limonite; one poorly preserved pelecypod chert, tuff, limestone (Lisburne) and quartzite (Sad- impression on a sandstone bedding plane; sandstone lerochit?) in a limonite matrix; sandstone friable, in upper part of unit has a porosity of 14.6 percent light-gray to yellowish-brown, crossbedded; plant re­ and a permeability of 14 millidarcys ______70 mains and coaly material along bedding planes; salt- Mostly tundra covered; some fine-grained light-gray and-pepper sandstone with a porosity of 17.1 percent sandstone with a porosity of 17.75 percent and a per­ and a permeability of 420 millidarcys; 5-ft bed of meability of 10 millidarcys ______580 light-pink medium-grained sandstone near top of unit 410 Conglomerate and sandstone as described above; sand­ Tundra covered ______120 stone massive, crossbedded, almost impermeable with Yellowish-brown-weathering coarse-grained sandstone 75 a porosity of 5.53 percent ______40 Medium-gray thin-bedded shale _ __ __ 40 Interbedded friable sandstone and conglomerate _ _ 190 Total measured thickness of Sagavanirktok for­ Tundra covered; salt-and-pepper sandstone at base and mation ______1,600 sandy medium-gray shale _ __ __ 270 Ignek formation, upper member. Contact (arbitrarily placed at base of sandstone). Section 10 is a composite and includes the exposures Total measured thickness of Sagavanirktok for­ in the cutbanks along the east side of Fin Creek and mation ______2,045 the outcrops of the formation on the south flank of Ignek formation (upper member). the Shaviovik anticline between Fin Creek and the Age. No fossils were collected from the rocks Shaviovik River. The rocks dip as much as 37° N. mapped as Sagavanirktok formation; the Tertiary age in the exposures along the creek and dip from 8° to assignment is based on a correlation of this rock unit 24° S. on the south flank of the anticline. The con­ with that described by Gryc, Patton, and Payne (1951, tact of the formation with the underlying Ignek for­ p. 167). Roland W. Brown identified Metasequoia mation is not exposed at this locality, but just north occidentalis (Newberry) Chaney, Morus sp., Oinna- of the measured section in the breach of the anticline monum ficoides Hollick, Pterospermites conjunctivus along Juniper Creek the rocks of the Ignek formation Hollick, Trapa microphylla Lesquereux, and Gercisl dip more steeply than do the rocks of the overlying sp. from the beds in the lower part of the Sagavanirk­ Sagavanirktok formation, and a structural uncon­ tok formation on the Sagavanirktok River; he as­ formity is indicated between the two rock units. The signed these beds an early Tertiary age. upper beds of the younger formation have been eroded Not all evidence supports a Tertiary age assign­ at this locality. ment for the rocks mapped as Sagavanirktok forma­ SagavanirMok formation, section 10 tion, however. H. R. Bergquist (written communica­ Feet Fine- to medium-grained yellowish-brown-weathering fri­ tion) identified a microfauna from the United able sandstone ______40 Geophysical Company's seismic shotholes on the flanks Mostly tundra covered; some ferruginous shale ____ 200 of Shaviovik anticline in the beds mapped by the Medium-grained yellowish-brown-weathering friable authors as Sagavanirktok formation: sandstone ______25 Tundra covered ______45 Paleontologically speaking, I cannot see any strong evidence Friable light yellowish-gray clean sandstone with inter- to support a Tertiary age for the [rocks designated as Saga­ beds and lenses of sandy conglomerate; conglomerate vanirktok formation in the area of the Shaviovik anticline] constituents are rounded cobbles and boulders from * * *. Only specimens of Pelosina sp. and of Trochammina 6 in. to 1 ft in diameter of quartzite, white quartz, ribstonensis 1! Wickenden are of any consequence in this part tuff, and fine-grained igneous rock and limestone of of the section. Pelosinas are long ranging and those found Mississippian age ______80 in the northern Alaska Cretaceous sediments are either the Tundra covered; some sandy shale ______200 same or closely similar to [those present in these shothole Fine- to medium-grained light-gray friable clean sand­ samples] * * *. The Trochammina sp. has been questionably stone ______60 referred to T. ribstonensis because of its similarity to that Mostly tundra covered; some fine-grained yellowish- Upper Cretaceous form. A specimen of Nonionella austinana gray sandstone and sandy shale ______100 Cushman in shotpoint 3, line 3, [see pi. 24, this paper] is the GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 209 same as the species of Nonionella found in the Schrader Bluff light brown. The cobbles and boulders comprise white formation * * * of the Upper Cretaceous. The Radiolaria quartz, quartzite, and quartzitic siltstone (Sadlerochit found in S.P. 2 and 3 and in 19 and 20 of line 6 appear to formation), limestone (Lisburne group), and vari­ be the same as Upper Cretaceous Radiolaria. In short, there is nothing diagnostic of Tertiary found in these sediments ously colored chert. The deposits are coarser near the and the microfossils appear more likely to be of Late Cre­ mountains where the boulders are as large as 4 feet taceous age. in diameter, and progressively finer northward. As Despite the conflicting evidence, the authors believe no fossils were found, the assignment of age of the that those rocks between the Shaviovik and Canning deposits is based entirely on their relationship with Rivers mapped as Sagavanirktok formation are the other stratigraphic units. The gravel is younger than lithologic and age equivalents of those in the Saga­ the Sagavanirktok formation and presumably older vanirktok River area designated as Tertiary by R. W. than the overlying Pleistocene moraine and therefore Brown (see above). is probably of late Tertiary to early Quaternary age. IGNEOUS ROCKS TEBTIABY AND QXTATEBNABY SYSTEMS The only igneous rock observed in the mapped area SURFICIAL, DEPOSITS is a mafic sill which intrudes the limestone beds of an As the study of bedrock geology in the area mapped anticline between the Ivishak River and Flood Creek. was the primary objective of the field investigations, Near Flood Creek, the sill, the age of which is un­ only a minor amount of data on surficial deposits was known, is about 150 feet thick. Its border zone con­ assembled. On the areal map, the surficial deposits tains numerous limestone zenoliths as much as 1 foot were divided into two general groups: alluvium and in diameter, and pyrite has been introduced into the gravels; the latter group includes glacial, high-level host rock. terrace, and pediment gravels. These gravel deposits The border phase of the sill adjacent to its lower have been mapped mostly from study of aerial photo­ contact is (sample examined in thin section) a holo- graphs; they are shown on the areal map as an over­ crystalline fine-grained porphyritic diabase composed lay pattern under which the bedrock geology has been predominantly of andesine and chlorite. Interstices projected. The glacial gravel was discussed on p. between prismatic plagioclase laths are filled with 175, and its distribution is shown on plate 22. The chlorite and an irregular highly mottled substance that bulk of the surficial deposits west of the Echooka is tentatively identified as titanite or perovskite. The River are interpreted to be glacial in origin. East phenocrysts are composed of chlorite; some have pe­ of the Echooka River, however, the glacial deposits ripheral zones of microcrystalline chlorite which pass overlie a more or less continuous blanket of gravel into central zones of serpentine. The edges of the which caps an erosion surface of moderate relief, and phenocrysts are corroded and so indistinct that former the authors believe that these deposits resulted from crystal outlines are obliterated, but the texture of the fluviatile deposition on a late Tertiary and early serpentine appears more like that derived from py- Quaternary piedmont slope. roxine or amphibole. The plagioclase is andesine The pediment(?) gravel is almost flat lying; it rests (Ab63An37); some of the laths show albite twining, unconformably on Permian to lower Tertiary rocks others zonal growth. The plagioclase seems to have and extends almost continuously from the crest of formed early and is locally enclosed by titanite (?) or the Canning-Kavik Rivers divide, where it is overlain perovskite (?). Where chlorite is in contact with the by glacial gravel, to the divide between the Echooka plagioclase, the contact along the long dimension of River and the Shaviovik River where it is similarly the lath is abrupt; on the ends it is dentate with overlain. These deposits are present just north of chlorite replacing plagioclase. the mountain front along the Canning-Kavik Rivers The limestone xenoliths have rounded corroded divide at an altitude of 2,200 feet and near Kemik borders; they have been recrystallized to coarsely Creek at an altitude of 2,000 feet. Their most north­ crystalline calcite. In a few inclusions quartz is erly occurrence is along the east valley slope of the present also. Chlorite is the most common mineral in Kavik River at an altitude of about 1,300 feet, their contact with calcite and generally occurs in a micro- lower limit of outcrop along the slopes of the valley crystalline narrow zone surrounding the inclusion. ranges from 75 to 100 feet above the present floor. The replacement of, and penetration into, calcite along The pediment (?) gravel deposits consist of a mix- cleavage planes by chlorite has produced a comblike ture of unconsolidated sand, cobbles, and boulders; texture. they are at least 50 feet thick. The sand is light gray The central zone of the sill (sample examined in and ranges from fine to coarse grained; it weathers thin section) is an aphanitic andesite porphyry. The 210 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 rock consists of a feltlike groundmass of plagioclase Echooka River and Fin Creek, the rocks of the crystals containing corroded phenocrysts of chlorite Kingak and Okpikruak formations have been cut by and calcite. The interstices are filled with veinlets, a series of east-trending high-angle reverse faults that irregular masses, and minute crystals of magnetite. may be the surface expression of a deeper thrust. Plagioclase (andesine, Ab6oAn4o) is present as sub- This same structural condition is present in the north­ hedral laths. Chlorite has partly replaced calcite ernmost strata mapped on Gilead Creek and may also along the cleavage planes in the phenocrysts; the reflect a deeper thrust. primary minerals which have been replaced cannot be The rocks west of Elusive Lake are more contorted identified. Quartz and sericite fill some of the fracture than those in the more northerly part of the mapped veins. area; they are overturned and are characterized by STRUCTURE tight folds and high-angle reverse faults. Southeast FOLDS AND FAULTS of Elusive Lake rocks of the Lisburne group and the Sadlerochit formation locally are recumbent and have The north flank of the Brooks Range from the Can­ been thrust over younger strata. Westward this thrust ning to the Sagavanirktok River comprises a succes­ becomes a high-angle reverse fault juxtaposing Per­ sion of en echelon east- and west-plunging anticlines mian and Triassic rocks with Jurassic and Cretaceous and synclines. The anticlines are normally asym­ rocks. metric with steeper north flanks, and those in the lime­ AGE OF FOIJOING AMD FAULTING stone of Mississippian age plunge about 20° from The rocks in the Shaviovik and Sagavanirktok their structural highs in the mountains to their point River region were folded and faulted at various times of disappearance beneath the younger strata of Meso- since the deposition of the Lisburne group, and the zoic age. The synclines, at least those in the Creta­ nature of this deformation is reflected in the structural ceous and Tertiary rocks of the mapped area, are relationships between the various formations. For normally broad, open folds with gently dipping limbs, the purposes of the following discussion the mapped although locally they are cut by high-angle reverse area was divided into two parts which will be treated faults. separately: one north and east of the Lupine River, From Elusive Lake to the Canning River the struc­ the other south and west of the Lupine River. This tural features are relatively simple. The anticlines are division has been made because the Mesozoic rocks in asymmetric, locally overturned, and commonly faulted. the latter area were deformed to a greater degree and The faults are of the reverse type with the south side probably during more time intervals than were the upthrown, with hades seldom exceeding 30°, and gen­ former. During the period when the rocks in the erally with minor displacement. Transverse faults southwestern part of the mapped area were being are present locally; those of greatest displacement are folded and faulted and those in the northeastern part along the east side of the Ivishak River south of were not, the tectonic forces obviously did not die Kashivi Creek, along the Lupine River, and, possibly, out abruptly at the Lupine River, but it is in this along the Shaviovik River. On the Lupine River the general locality that the change in intensity probably transverse faults cut the strata in the structurally low occurred. area between the predominantly west-plunging struc­ Lupine River to the Canning River. North and tures on the east side of the creek and a doubly-plung­ east of the Lupine River, the Sadlerochit, Shublik, ing anticline on the west side of the creek. The most Kingak, and Okpikruak formations are structurally westerly of these faults has juxtaposed limestone of conformable, and it is unlikely that any major de­ the Lisburne group with shale and siltstone of the formation occurred from Mississippian time to the Tiglukpuk formation; the stratigraphic displacement Valanginian stage of the Early Cretaceous (fig. 27). probably exceeds 2,000 feet. Thrust faults are not The first major deformation apparently took place common in the area northeast of Elusive Lake; how­ ever, on the east side of the Ivishak Eiver the strata prior to the deposition of the Ignek formation, for of the Lisburne group have been thrust over Permian these rocks overlie the older rocks with structural un­ and Triassic rocks and two klippen of the Lisburne conformity. The next youngest stage of deforma­ group overlie the Sadlerochit formation. Between the tion is not so apparent, but the structural relationships Echooka and the Kavik Rivers, strata of the Kingak between the members of the Ignek formation suggest shale and the Kemik sandstone member of the Okpik- a time of uplift and erosion prior to the deposition ruak formation locally have been thrust over younger of the upper member. The difference in thickness of rocks. North of these thrust faults between the the lower member of the Ignek formation from one GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 211 part of the mapped area to another indicates that the ANTICLINES period between its deposition and that of the upper The alinement and direction of plunge of the en member was one of erosion. Along the west side of echelon anticlines which form the north front of the the Juniper Creek in the breached Shaviovik anticline Brooks Range (fig. 32) form an orderly pattern. the dip of the Cretaceous rocks, steeper than that of The anticlines plunge east from Kemik Creek to the the flanking Tertiary rocks, indicates that the next Kavik River and west from Kemik Creek to Elusive younger folding probably occurred between the deposi­ Lake. From the Canning to the Kavik Rivers, the tion of the upper member of the Ignek formation and plunge is west; from the west side of the Sagavanirk­ that of the Sagavanirktok formation. The latest fold­ tok River toward Elusive Lake, the plunge is east. ing in the area between the Lupine and Canning The structural highs of the northeast-trending anti­ Rivers occurred after the deposition of the Saga­ clines, including 2 in the mountains and 3 in the foot­ vanirktok formation and prior to that of the pedi- hills, aline in a northerly direction from the head­ ment(?) gravel of late Tertiary or early Quaternary waters of Kemik Creek to the axis of the Shaviovik age. Of the four possible periods of deformation, the anticline. Billings (1942, p. 49) defined "alinement" folding and faulting in post-Okpikruak and pre- as a "line of culmination." Similarly there appears Ignek time and in post-Sagavanirktok times appears to be a north-trending, structurally low area (re­ to have been strongest. ferred to as "line of depression" by Billings, p. 49) Lupine River to the Sagavanirktok River. South­ near the headwaters of Kavik River, and, although west of the Lupine Eiver the Lisburne group and the it is not as well delineated, another is present between Sadlerochit and Shublik formations appear to be the Sagavanirktok River and Elusive Lake. Assum­ structurally conformable, and it is unlikely that any ing that the lines of culmination and depression are folding or faulting occurred until Jurassic time. The not fortuitous, the most reasonable postulation to Tiglukpuk, the Okpikruak, and the Fortress Moun­ explain their presence is that the northerly alinement tain formations between the Lupine and the Saga­ is a reflection of the grain of the basement. The vanirktok Rivers all contain coarse clastic rocks and nature of the forces which produced it is not known; are typified by sandstone of graywacke type. The presumably such an alinement could have resulted exact nature of the contacts between the three forma­ from early deformation, but if so, the character of tions is not known. West of Elusive Lake, however, this earlier folding has been obscured by the deposi­ the Okpikruak locally overlies the lower part of the tion of younger rocks and by the forces which pro­ Tiglukpuk formation, and in a north-south distance duced the present east-trending structural features. of about 2 miles the Fortress Mountain formation in The southernmost of the three anticlines in the foot­ 3 fault blocks locally overlies the Okpikruak, the hills along the northerly alinement of the structural Tiglukpuk, and the Shublik formations. Even assum­ highs has steep to vertical flanks composed of the ing a foreshortening by faulting, it is unlikely that Kemik sandstone member of the Okpikruak formation. such relationships could be brought about except by The anticline is breached and exposes the Kingak deformation and erosion during the period between the shale. The anticline as delineated by the flanking deposition of the Tiglukpuk and the Okpikruak for­ beds of the Kemik sandstone member is a closed struc­ mations and the one between the deposition of the ture. However, its tight folds and the number of Okpikruak and the Fortress Mountain formations. high-angle reverse faults in the general area indicate Furthermore, as all three formations are characterized that the anticline may be the folded doubly-plunging by orogenic-type rocks, it seems possible that folding hanging wall of a reverse fault and may not continue and faulting of these rocks may have taken place at depth. during their deposition. The next northerly anticline along the line of cul­ The only other stages of folding after Albian time mination is a closed structure with average dip of noted in this part of the mapped area were those that 35° to 40° on the south flank and 45° to 50° on the deformed the rocks of the Nanushuk group. By north flank. The anticline (Kemik anticline) has a analogy, these younger rocks could have been deformed minimum of 500 feet of east plunge and is cut by a during the period between the deposition of the lower transverse fault along its west end. The proved closed and upper members of the Ignek formation, between part of the anticline, delineated by the transverse the deposition of the upper member and the Saga­ fault and the flanking beds of the Kemik sandstone vanirktok formation, during post-Sagavanirktok time, member, is about 3 miles long and half a mile wide or during all three periods. with a minimum structural relief of 500 feet. The 212 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53

680 3CX 20 MILES

FIGURE 32. Map showing distribution of major anticlinal axes In the Sbavlovlk and Sagavanirktok Rivers region, Alaska. anticlinal trend can be traced eastward beyond the feet of closure. The Sagavanirktok formation flanks flanking beds of the Kemik sandstone member for an the anticline, and the upper member of the Ignek for­ additional 2 miles. It cannot be traced west of the mation crops out in the breach. The rocks of neither Shaviovik River but may continue beneath the gravel formation are particularly well exposed, but the best cover. outcrops on the south flank of the anticline are in Shaviovik anticline. The Shaviovik anticline, the cutbanks along Fin Creek, Juniper Creek, and the most northerly of those along the line of culmination, Shaviovik River, and in the area between these is about 15 miles long and 3% miles wide with a north- streams. The rocks of the upper part of the Ignek south minimum structural relief of 2,900 feet. The formation and the lower part of the Sagavanirktok anticline has been interpreted to have about 1,100 formation also crop out on the west sides of Juniper GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 213 Creek and the Shaviovik River on the north flank of trending ridge. The altitude of this ridge at the point the anticline. In addition a rubble trace of the basal at which it is bisected by the anticlinal axis is about sandstone of the Sagavanirktok formation crops out 1,500 feet. Along Juniper Creek the base of the Saga­ about 11/2 miles west of the point where the axis of vanirktok formation reaches an altitude of 2,600 feet this structural feature crosses the Shaviovik River. (pi. 24). Assuming that the ridge is underlain by Between Juniper Creek and the Shaviovik River the the Sagavanirktok formation, there can therefore be north flank of the anticline is devoid of outcrops, but no less than 1,100 feet of east plunge and no less than locally the position of beds of the Sagavanirktok 1,100 feet of closure on the Shaviovik anticline. formation can be inferred from an alinement of darker vegetation readily visible on vertical aerial photo­ SUBSURFACE STRUCTURE graphs. Similarly, in the breach of the anticline, the Seismograph surveys were made on the west end position of beds of the Ignek formation can be in­ of the Shaviovik anticline by United Geophysical Co., ferred locally, and the placing of the axis is based Inc. A series of 12 lines were run, and the structural partly on these inferred positions. interpretation of these data, including 12 cross sec­ On the north and south flanks of the anticline, struc­ tions and 2 structural maps, were prepared by its ture contours were drawn on the base of the Saga­ seismologists. The 2 structure maps are shown on vanirktok formation (pi. 24). Where the Sagavanirk­ plate 24, the cross sections on plates 25 and 26. tok formation has been eroded from the crest of the Two phantom horizons were contoured by the seis­ anticline the position of the contours was established mologists; one represents a zone of reflectors between by projecting the dips of the contoured horizon from 8,000 and 11,000 feet, the other a zone of reflectors the flanks of the anticline to its crest. As interpreted between 12,000 and 14,000 feet. The contours of by the authors, the west end of Shaviovik anticline is the lower horizon (pi. 24) show no closure but depict an asymmetric fold with gentle south flank and what may be a nose of a north-plunging anticline. steeper north flank. The steeper dips along the north The contours of the upper horizon as interpreted by flank may be representative of a reverse fault, but the seismologists (pi. 24) show a series of low-dipping evidence for verifying this hypothesis is lacking. reverse faults and folds. Between the northern part From Juniper Creek to a point about 1^ miles west of line 6-53-144 and line 10-53-144 a faulted struc­ of the Shaviovik River, the structural feature plunges tural feature with a possible closure of as much as about 1,700 feet, and between these points there is an 700 feet is delineated. The cross-section lines (pis. interpreted minimum closure of 90 feet. Southeast 25, 26) show no continuous reflectors between the of this area of closure a transverse fault cuts the faulted structural complex at depth and the surface flanking beds. structure, and therefore the relationships between the East of Jumper Creek, the bedrock is obscured by two cannot properly be evaluated. tundra for about 9^/2 miles, and the configuration of the eastern end of Shaviovik anticline is therefore HISTORICAL GEOLOGY unknown. Furthermore, the east plunge of the Shavi­ The geologic history of the mapped area has been ovik anticline and its postulated closure is dependent interpreted from the nature of its sedimentary rocks on whether the authors' interpretation of the struc­ and their relationships, the character of its structures, ture near Kik Creek is valid. At the Kavik River, and to a large extent from the ages assigned to the an anticline, interpreted as the eastern extension of formations by the paleontologist. As the oldest rocks the Shaviovik trend, plunges west to Kik Creek; be­ in the area are Mississippian, only those events in yond, it is obscured beneath a tundra-covered north- geologic time since deposition of the Lisburne group trending ridge. In this part of the mapped area the are considered in this discussion. topographically high areas are typically underlain by The rocks that overlie the Lisburne group (Echooka the Sagavanirktok formation; the low areas, by the member of the Sadlerochit formation) have been as­ less resistant rocks of the Ignek formation. Partly signed a Permian age. There is not enough evidence for this reason, partly because of the west plunge of in the mapped area to determine whether Pennsyl- the anticline between the Kavik River and Kik Creek, vanian rocks were deposited and eroded prior to the and partly because of the apparent convergence of the deposition of the Echooka member, but the structural contacts between the Ignek and Sagavanirktok forma­ conformity between this member and the Lisburne tions east of Kik Creek, the authors believe that rocks group indicates a time of general structural stability of the Sagavanirktok formation are present along between their depositions. Following this period it the anticlinal axis beneath the tundra of the north- seems evident that in Permian and Early Triassic 214 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 time sediments were shed from a northern landmass. the Jurassic rocks also indicate, the hiatus between The Echooka member of the Sadlerochit formation is the Kingak and the Shublik formations locally repre­ more coarsely clastic in the northern part of its out­ sents only a possible short Late Triassic and Early crop belt (fig. 28) and changes southward to a more Jurassic interval; the one between the Tiglukpuk marine rock type. The Ivishak member (Early Tri- and the Shublik formations may represent all of the assic age) follows the same general trend, and the Early and Middle Jurassic epochs (fig. 27). similarity between the siltstone of this member and It is postulated, then, that the seas retreated north­ that of the Echooka (see p. 178), suggests that the two ward during the Ehaetian, Hettangian, and Sine- probably had the same source. There is insufficient murian stages but transgressed southward in the time evidence to determine whether the break between the between the Pliensbachian and Kimmeridgian stages. Echooka and the Ivishak members represents an Although there is little evidence on which to base a erosional interval. The Echooka changes in thickness conclusion, the authors believe that the part of the locally, but this change may be the result of deposi­ mapped area in which the Tiglukpuk formation crops tion rather than erosion. The structure and sedi­ out was relatively stable from Pliensbachian to Cal- mentary relationships between the two members do lovian time, and that marine deposition did not occur not indicate a very great hiatus between them. until the Oxfordian stage. An alternative is that There is no evidence that Middle Triassic rocks were Lower and Middle Jurassic rocks were deposited and deposited in the mapped area; rocks of Late Triassic eroded prior to the deposition of the Tiglukpuk for­ age overlie the Sadlerochit formation with structural mation. The first alternative necessitates only one conformity. The Late Triassic Shublik formation is period of subsidence; the second, subsidence followed typical of rocks deposited in lagoonal environments by uplift, erosion, and a second period of subsidence. or in waters of restricted circulation; it was probably Kegardless of which alternative is correct, the pres­ derived from a stable landmass of low relief. Its ence of graywacke and conglomerate in the Tiglukpuk source is not known; although there are no confirming formation indicates that it was deposited from a data, a northerly source is indicated. southern land mass which rose rapidly during the In contrast with the older rocks that at least in initial stages of an orogeny in late Middle or early part had a northern source, it seems evident that the Late Jurassic time. Jurassic and all younger rocks which crop out in the The next younger formation in the mapped area also Shaviovik and Sagavanirktok Kivers region had a had a southerly source. The Okpikruak formation, southern source. The Kingak shale, which crops out which has been assigned to the Berriasian and Valan- north of its partial time-equivalent, the Tiglukpuk ginian stages of the Early Cretaceous, is an unfossili- formation, is a thick sequence characterized by am- ferous coarse clastic graywacke sequence near Elusive monoids; it coarsens slightly in a southerly direction. Lake. In the northeastern part of the area it is com­ The Tiglukpuk formation on the other hand is com­ posed of shale, although from the Echooka River to posed mostly of coarse elastics, is characterized by Juniper Creek it contains a basal clean sandstone graywacke, and contains scattered pelecypod shells in member. Near Elusive Lake, the coarse clastic se­ the northern part of its outcrop belt and lenses of quence overlies the lower part of the Tiglukpuk for­ coquina in the southern part. In addition, more con­ mation with probable angularity (see p. 197); north­ glomerate is present in the Tiglukpuk formation in east of the Lupine Eiver the formation overlies the the southern part of its outcrop belt than in any other Kingak with apparent structural conformity. part of the mapped area in which the formation is These facts indicate that the seas regressed north­ present. ward during Portlandian time and that the Jurassic Although there is no confirming field evidence, the and older rocks in the southwestern part of the map ages assigned to the fossils in the Jurassic rocks of area were uplifted, deformed, and differentially the mapped area indicate that the younger Jurassic eroded. The deformational forces were apparently rocks overlap the older in a southerly and westerly not transmitted so severely to the northern part of direction from the Canning Kiver to Elusive Lake the mapped area, but the presence of the basal clean (fig. 29). The overlap may have been complicated sandstone in the Okpikruak formation suggests that by a pre-Late Jurassic high near the Saviukviayak the area between the Echooka Eiver and Juniper Kiver; Lower and Middle Jurassic rocks either were Creek may have been a relatively positive element not deposited over this high or were eroded prior to during this stage. During the Berriasian and Valan- Lake Jurassic sedimentation. As the ages assigned to ginian stages the seas transgressed southward and the GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 215 coarse clastic rocks of the Okpikruak formation were formations east of the Ivishak Eiver has two possible deposited near Elusive Lake; shale was deposited explanations. The first hypothesis is that east of the farther north, probably concurrently. Ivishak Eiver the area was emergent not only during There is no fossil evidence that any sedimentation the Hauterivian, Barremian, and Aptian stages but occurred in the mapped area from the close of the also during a large part of the Albian. The second Valanginian until Albian time. Concerning this hia­ hypothesis is that rocks equivalent in age to the tus, Imlay (written communication) stated: Fortress Mountain and Torok formations were de­ The unconformity between the Okpikruak and the Torok posited east of the Ivishak Eiver but were eroded formations [Torok formation and Fortress Mountain forma­ prior to the deposition of the lower member of the tions of this report] probably represents at least one-third Ignek formation. If the lower member is equivalent of Early Cretaceous time as there is no fossil evidence on in age to the Nanushuk group, as postulated by the the Arctic Slope of Alaska for the presence of the Hauterivian, authors, this second hypothesis necessitates a period Barremian, and Aptian stages of the Early Cretaceous. Part of the Aptian may be present in the lower part of the Torok of uplift and erosion which would correspond roughly formation [and (or) the Fortress Mountain formation] be­ to the time interval between the deposition of the neath the beds containing the early Albian ammonites Cleoni- Torok and the Tuktu formations. As there is no ceras and Lemuroceras. However, I doubt whether the evidence in the outcrop area of such a period of ero­ Hautervian and Barremian are present. Recently * * * I sion, the first hypothesis is the more logical. found a statement that "there is no reliable evidence at hand of post-Valanginian/pre-Aptian beds being developed any­ By middle Albian time the orogenies, reflected in where in the Arctic regions" (Maync, 1949, Medd. om Gron- the structural relationships and the type of sediments land, v. 133, no. 3, p. 242). I have * * * found it to be true. which comprise the Tiglukpuk, Okpikruak, and For­ The most northerly occurrences of Hauterivian and Bar­ tress Mountain formations apparently drew to a close. remian deposits are in the Himalaya region, central Russia The rocks of the Nanushuk group are characterized near Moscow and Simbirsk, southwest Poland, northwest Ger­ many, and Lincolnshire, England. It seems evident, there­ by subgraywackes; the structural relationships be­ fore, that there was general retreat of the Arctic Ocean from tween the formations of the group indicate that the bordering land masses during the Hauterivian and Bar­ deposition may have been continuous from Albian to remian stages and that this retreat corresponds to the un­ Cenomanian time. The group is characterized by two conformity between the Okpikruak and the Torok * * * [and marine formations, the Tuktu and the Ninuluk, sepa­ (or) the Fortress Mountain] formations in northern Alaska. rated by a nonmarine to near-shore formation, the Imlay's data and the fact that the Fortress Moun­ Chandler. It therefore is evident that the seas oscil­ tain formation probably overlies older rocks with lated during the deposition of the group. East of the angular discordance (see p. 199) indicate that dur­ Ivishak Eiver, the area which was emergent during ing the retreat of the seas in the Hauterivian, Bar­ the Hauterivian, Barremian, and Aptian stages and remian, and Aptian(?) stages the rocks in the south­ probably during part of the Albian stage, was once western part of the mapped area were uplifted, more submerged by seas which transgressed from the deformed, and differentially eroded. During Albian north, and, concurrently with the deposition of the time the Fortress Mountain formation was deposited Nanushuk group in the western part of the mapped near Elusive Lake, and if the interpretation of the area, the lower member of the Ignek formation was relationship between the Fortress Mountain and the deposited. The oscillation of the Cretaceous seas is Torok formations (fig. 30) is valid, the latter was not as well marked in these sediments, and the car­ deposited at almost the same time. The rocks of the bonaceous sandstones which characterize most of the Fortress Mountain formation are erogenic types char­ acterized by conglomerate and graywacke; the Torok rock unit appear to be typical of those deposited in is composed mostly of shale. Consequently it appears deltas and lagoons or in other waters marginal to a that the Fortress Mountain formation was deposited shoreline. from a nearby rapidly rising erogenic landmass and The erosional break that separates the lower mem­ that the Torok formation was deposited concurrently, ber from the upper member of the Ignek formation but at a greater distance north from the source area. suggests that the seas regressed northward during a Neither formation is believed to be represented east part of Turonian time and that this regression was of the Ivishak River where the lower member of the followed by a transgression with minor oscillations. Ignek formation, which has been correlated with the During this transgression the upper member was de­ Nanushuk group, unconformably overlies the Okpik­ posited in much the same environmental conditions as ruak and Kingak formations. The absence of these the lower member. The pyroclastics of the lower part 216 EXPLORATION OF NAVAL PETROLEUM RESERVE NO. 4, ALASKA, 1944-53 of the rock unit show that the depositional period was the Okpikruak formation, excluding the basal Kemik in part one of volcanic activity. sandstone member, is predominantly a fossiliferous In post-upper member time, the seas regressed north­ shale sequence of no more reservoir potential than ward and in Tertiary time the nonmarine to near- the Kingak, although these shales also could be an oil shore and beach sediments of the Sagavanirktok for­ source. The youngest formation in this class, the mation were deposited. The shoreline of the Tertiary Torok, crops out from the western edge of the mapped basin appears to have alined relatively close to the area to about the Ivishak Kiver and probably has present outcrop belt of the basal sandstone and con­ neither source nor reservoir potential. glomerate beds of the Sagavanirktok formation. The The formations of the second class have approxi­ pyroclastic material, probably derived from the lower mately the same belt of outcrop as those of the first, part of the upper member of the Ignek formation, an almost east-west distribution from the western that is present as detritus in the conglomerate beds is edge of the mapped area to about the Lupine River; evidence of their nearby source. similar orogenic-type rocks are not present north of In post-Sagavanirktok time the mapped area was about lat 68°55' N. Their lithology and structural uplifted and the rocks were deformed and differen­ relationships indicate that the Tiglukpuk, the coarse tially eroded. Since the Tertiary orogeny, the land- clastic facies of the Okpikruak, and the Fortress form has been modified further by glaciation, erosion, Mountain formations were deposited in what appears and fluviatile deposition. to have been a part of the mobile belt of the Jurassic and Cretaceous geosyncline. As is common with rocks PETROLEUM of such depositional environments, the sandstones The Shaviovik and Sagavanirktok Rivers region has which characterize these formations in this part of all the requisites of a petroleum province; source the mapped area are almost nonporous and imper­ rocks, potential reservoir rocks, and structures on meable. The chances of producing oil from any of which tests could be drilled. Structurally and strati- the three formations are probably not very good. graphically the area east of the Ivishak Kiver appears The third class of formations in the mapped area to be slightly more promising than that west of the are potentially at least, those which might produce river. petroleum. The Lisburne group crops out across the There are three general classes of formations in the mapped area and is a thick limestone sequence not mapped area: (a) those composed predominantly of unlike other Mississippian rocks which, in Canada shale with little reservoir possibility, such as the and the United States, are producers. The group Kingak, the Okpikruak in part of the mapped area, probably can be reached with a drill anywhere in the and the Torok formations; (b) those composed mostly mapped area north of its outcrop belt. The Sad- of orogenically derived sediments with nonporous and lerochit formation similarly can be drilled anywhere impermeable characteristics, such as the Tiglukpuk, north of its outcrop belt. Its members, however, are the Okpikruak in the vicinity of Elusive Lake, and the more sandy and less cherty in sections near the Can­ Fortress Mountain formations; and (c) those rock ning River, and the facies changes depicted on fig. units which, potentially at least, could contain reser­ 28 indicate a greater possibility of producing oil from voir beds, such as the Lisburne group, the Sad- the formation north of lat 69°30' N. where shoreline lerochit and Shublik formations, the Kemik sandstone facies might be encountered. member of the Okpikruak formation, the Tuktu, Unlike the Sadlerochit, the Shublik formation has Chandler and Ninuluk formations, the Ignek forma­ about the same petroleum potential in one part of tion, and the Sagavanirktok formation. the mapped area as another. It is composed for the The Kingak shale is a thick fossiliferous sequence most part of limestone and limy shale, but between which could be a source for oil, and it crops out from Kemik and Fin Creeks it also contains sandstone. the general vicinity of the Lupine Kiver north and Although it conceivably could produce oil from some east to the Canning Kiver. The upper part of the of its limestone beds, the Shublik contains potentially formation contains some sandstone in the northeastern better source than reservoir rocks. Like the two older part of its outcrop belt, but it is unlikely that the rock units, the Shublik probably can be reached with formation has reservoir potential at depth anywhere in a drill anywhere north of its outcrop belt. the mapped area. In approximately the same out­ The Kemik sandstone member of the Okpikruak crop belt (from the Lupine to the Canning River) formation, which consists of 220 feet of relatively GEOLOGY OF THE SHAVIOVIK AND SAGAVANIRKTOK RIVERS REGION 217 clean and moderately well sorted sandstone, crops out Structural conditions seem to be slightly more favor­ only between the Shaviovik and Kavik Rivers. Al­ able for petroleum production east of the Echooka though this member may underlie younger rocks north River than west. All but one of the anticlines from of its outcrop belt, it is probably not present in the the Echooka River to Elusive Lake plunge west with­ subsurface west of the Echooka or east of the Kavik out apparent closure (fig. 32). The one exception is a River. closed structure between the Lupine River and the The Nanushuk group, including the Tuktu, Chan­ Ribdon River, but this anticline is breached and the dler, and Ninuluk formations, contains marine and Lisburne group is exposed in its crestal area. Petro­ near-shore sandstones that should have fair potential leum production from the Lisburne group and from if they could be drilled where structural conditions the Sadlerochit and Shublik formations is possible are favorable. However, these rocks crop out also along the west-plunging anticlines, particularly if only in a limited area, from the Ivishak River to the there is a terracing along the anticlinal axes beneath vicinity of the Sagavanirktok River, and occur so the Mesozoic rocks. Whether there is such structural high in the stratigraphic column that they are not terracing cannot be determined without drilling or present at depth in the mapped area. geophysical investigation. West of Elusive Lake the The lower member of the Ignek formation, which is rocks are contorted and the structure is characterized the probable time equivalent of the Nanushuk group, by high-angle reverse faults. The possibility of pro­ and the upper member of the Ignek formation crop ducing oil from fault traps in the three oldest forma­ out from the Ivishak River east to the Canning, and tions cannot be dismissed, but, again, whether such both members in part contain marine or near-shore fault traps are present can be demonstrated only by sandstone. The lower member may be present in the geophysical work or by drilling. subsurface almost anywhere west of the Canning In the foothills east of the Echooka River there are River north of lat 69°30' N. beneath the rocks of the at least 3 closed anticlines whose structural highs oc­ upper member. Excluding structural considerations, cupy positions along a line of culmination which ex­ the complete sequence of the upper member could be tends northwestward for about 25 miles from the tested at any locality in the mapped area where it is locality where Kemik Creek emerges from the moun­ overlain by the Sagavanirktok formation, which, in tains (fig. 32). The southernmost of the three anti­ effect, is only the outcrop belt between the Shaviovik clines (the anticline south of Kemik anticline; see pi. and the Kavik Rivers. 21) is probably the folded hanging wall of a reverse The Sagavanirktok, although it contains more per­ fault. The next northerly anticline, the Kemik, is meable and porous members than any of the older small with closure of about 500 feet in an area 3 miles formations, crops out so far north and occurs so high long and % mile wide. The largest of the 3 anticlines, in the stratigraphic column that it is not present in the the Shaviovik, has been interpreted to have 1,100 feet subsurface of the mapped area under conditions favor­ of closure with possible dimensions of 15 miles by S1^ able for drilling. miles. However, the seismic work on the western end Of the formations that might yield petroleum, of the structure (pis. 24r-26) did not determine the therefore, excluding structural considerations, the Lis- relationship of the subsurface structure to the surface burne groups and the Sadlerochit and Shublik for­ structure. mations could be drilled anywhere in the mapped area In addition to structural traps in the mapped area, north of the outcrop belt of the Shublik formation; stratigraphic traps may also be present; their pres­ the Kemik sandstone member of the Okpikruak for­ ence cannot be predicted, however, at the present stage mation, only between the Shaviovik and Kavik Rivers of exploration. REFERENCES north of lat 69°30' 1SL; the lower member of the Ignek formation, anywhere west of the Canning River north Billings, M. P., 1942, Structural geology: Prentice-Hall Inc. Bowsher, A. L., and Dutro, J. T., Jr., 1957, The Paleozoic sec­ of lat 69°30' N.; and the upper member of the Ignek tion in the Sliainin Lake area, central Brooks Range, formation, only between the Shaviovik and Kavik northern Alaska: U.S. Geol. Survey Prof. Paper 303-A. Rivers in the outcrop belt of the Sagavanirktok for­ Collier, A. J., 1906, Geology and coal resources of the Cape mation. Excluding any other considerations, drilling Lisburne region, Alaska: U.S. Geol. Survey Bull. 278. Detterman, R. L., 1953, Sagavanirktok-Anaktuvuk region, in the northeastern part of the mapped area could test northern Alaska, in Pewe, T. L., and others, Multiple the potential of five formations; elsewhere, only three. glaciation in Alaska: U.S. Geol. Survey Cir. 289, p. 11-12. 218 EXPLORATION OF NAVAL PETROLEUM RESERVE NQ. 4, ALASKA, 1944-53 1956, New and redefined nomenclature of Nanushuk in Colville River region, northern Alaska: Am. Assoc. group, in Gryc, George, and others, Mesozoic sequence in Petroleum Geologists, v. 40, no. 2, p. 219-223. Colville River region, northern Alaska: Am. Assoc. Petro­ 1957, New late Paleozoic formation, Brooks Range, leum Geologists Bull., v. 40, no. 2, p. 233-244. Alaska: U.S. Geol. Survey Prof. Paper 303-B. Gryc, George, Patton, W. W., Jr., and Payne, T. G., 1951, Pres­ Payne, T. G., and others, 1951, Geology of the Arctic Slope of ent Cretaceous stratigraphic nomenclature of northern Alaska: U.S. Geol. Survey Oil and Gas Inv. Map OM-126. Alaska: Washington Acad. Sci. Jour., v. 41, no. 5. Pewe, T. L. and others, 1953, Multiple glaciation in Alaska: Lemngwell, E. de K., 1919, The Canning River region, northern U.S. Geol. Survey Circular 289. Alaska: U.S. Geol. Survey Prof. Paper 109. Schrader, F. C., 1904, A reconnaissance in northern Alaska: Patton, W. W., Jr., 1956a, New formation of Jurassic age, in U.S. Geol. Survey Prof. Paper 20. Gryc, George, and others, Mesozoic sequence in Colville Smith, P. S., 1939, Areal geology of Alaska: U.S. Geol. Survey River region, northern Alaska: Am. Assoc. Petroleum Prof. Paper 192. Geologists Bull., v. 40, no. 2, p. 213-219. Smith, P. S., and Mertie, J. B., Jr., 1930, Geology and mineral 1956b, New and redefined formations of Early Creta­ resources of northern Alaska: U.S. Geol. Survey Bull. ceous age, in Gryc, George, and others, Mesozoic sequence 815. INDEX

A Page E Page Accessibility______170-171 Echooka glaciation.--. . 175 Accomplishment Creek area, glacial features______175 Echooka member of Sadlerochit formation, character and distribution... 178,179 Acknowledgments.. ______172 fossils..___._...... __...... -. 182-186 Acteon...... 205 sections______.__.___ . . 179-182 Aircraft landing areas_ __.....______173 Echooka River area, moraines.. 175 Alluvium_ ____.______209 petroleum possibilities_._ 217 Amaltheus (Pseudoamaltheus)...... 193 Elusive Lake______173 Ammobaculites...... 205 Elusive Lake area, petroleum possibilities.... 217 Amoeboceras (Prionodoceras)...... 193 Entolium...... 205 Anaktuvuk River, type locality of Lisburne group______177 Eopectin...... 205 AnidanthuB...... ___..______185 Euryphyllum...... 186 Anticline, description and locality______210,211-213 Exploratory methods...... 172 structure favorable for petroleum production______217 Arcainflata...... 190 Archicorys...... 207 Faults, age,,.__ _. 210-211 Arctica...... 202,205 description and location.... 210 Astarte...... 205 Fenestella...... _____...... _.__ 184,185,186 Aucella...... 193,194,197,198 Fieldparty..-- ---..------172 concentrica...... 193,195 Fin Creek section, Sagavanirktok formation- 208 crassicolis...... 197,198 Flood Creek, type locality of Ivishak member of Sadlerochit formation. 178 mosquensis...... 195 Flood Creek section, Sadlerochit formation... 182 name ruled invalid-.__-....______192 Folds, age - - 210-211 okensis...... -...... 197,198 anticlines...... - 211-213 rugosa...... 195 description and location-.,. 210 spitiensis-...... 193 Fortress Mountain formation, distribution 199 sublaevis...... 197,198 fossils.___.______. - . 199 subokemis...... 197,198 historical geology. 215 Aeicuto...... 190 history and type section . 198-199,200 Aviculopecten...... 186 lithology..-._ ...__-___ . . _ 200 S/irtyL...... 186 petroleum possibilities...-__ ... . 216 section..______~ ... 200,pis.21,23 type locality.. 198 Fossils, Fortress Mountain formation... 199 Bathysiphon...... 205 Ignek formation... 205,206-207 Bergquist, H. R., fossil identification.______205,207,208-209 Kingak shale- 192,193 Brown, Roland W., fossil identification.._....._...___._.._.____ 208 Lisburne group 177 Buchia, name replaces Aucella-...... 192 Okpikruak formation 197,198 Sadleroschit formation...... 178,179,182-187 Sagavanirktok formation... 208-209 CalophyUum...... 183 Shublik formation... _ ___-_ _ _ 189,190,191 Camptonectes...... 193 Tiglukpuk formation. . . - 194,195 Canning River area, glacial features..._..____.______.. 175 Torok formation.._ . . 199,200,201 Canning River section, Ignek formation .______.______204-205 Tuktu formation... 202 Sadlerochit formation__.--_-.._.--...______.__ 179-180 Franklin Bluffs, type locality of Sagavanirktok formation- _ 207 Canning River to Lupine River, age of folding and faulting... 210-211 Cardiomorpha...... 190 G Cercis...... _...... _._ 208 Gastroplites...... 202 Chandler formation, age ______203 kingi...... 202 lithology..._...... _._....._..._..._.__.._.....___... 202-203 Germanonautilus brooksi...... - . . --...... 190 petroleum possibilities______216,217 Gilead Creek-Ivishak River section, Ignek formation.. . 204 Chonetes...-...... 185,186 Gilead Creek section, Sadlerochit formation 181 Cinnamonumficoides...... ___ _ 208 Shublik formation . . . 189 Claraiastachei.-...... ______..__. 187 Glacial gravel.... ------175,209 Ckoniceras...... 215 Glacial history.... - ...... - 174-175 Climate...__-______171 Olyptophkeras-. 187 Clionites...... 190 Gordon, Mackenzie, Jr., fossil identification...... 182,183,184 Cobble Creek section, Shubllk formation______189 Gradient of rivers 173 Correlation of stratigraphic units______176 Gravel deposits...... 209 Cretaceous system______195-207 Gryc, George, Fatten, W. W., Jr., and Payne, T. G., quoted .... 195-196,201,207

D Halobia...... 190 Derbyiu...... 184 cordillerana...... 190 Detterman, R. L., quoted.. ______. 174-175,201,203 dilatata...... 190 Dictyomilra...... 207 superba.....- ...-. -.---. .. -. ------190 Discopkkeras...... 187 Haplophragmoides.-...... -...... 205 Ditrupa...... 205 Historical geology.-. - . - - 213-216 Drainage...... __ .______-____.._... 173 Hoplotropites-...... -.- ...... - 190 Duncan, Helen, fossil identification...._-__ ___.. .. 182,183,184,185,186 moffUL...... 190 219 220 INDEX

I Page Page Ice fields______173 Localities at which fossils collected, Ignek formation..___._____.._ _. 205 Ignek formation, historical geology______215,216 Kingak shale...______193 history...______203 Okpikruak formation______...... _ 197 Leffingwell's type section______203 Sadlerochit formation.....__.______.______182,186 lower member, age and correlation______205-206 Shublik formation.._____.______...______.___ 190 distribution-..______203 Tiglukpuk formation.______.... 195 fossils... .._.______.______...... __... 205 Tuktu formation.. ______...... 202 lithology-- ...... __.__...._... 203-204 Lupine River section, Tiglukpuk formation...._____ 195 sections...... ___. _____.... 264-205, pis. 21,23 Lupine River to Canning River, age of folding and faulting______210-211 petroleum possibilities______216,217 Lupine River to Sagavanirktok River, age of folding and faulting 211 upper member, age.. ___...______206,20 Lytoceras...... 197 distribution....______.______206 fimbriatum...... 193 fossils______. 206-207 lithology...... ___.__...._..._.__.. 206 M Igneous rocks______209-210 Mapping methods______172 Imlay, Ralph W., fossil identification______... 192,193,195,197,198,202,205,215 Margarites...... 190 Inoceramus-...... 193,199,200,201,202,205 Marginifera...... 185,186 altifluminis...... 202 septentrionalis...... 183 anglicus...... 202 typicasepientrionalis...... 183 cadottensis ______202 Meekella-...... 184 dunveganensis...... 203 Mesozoic rocks, correlation...__.._____ 200 Investigation, present-..______171-172 Metasequoia occidentalis______208 previous.. ______171 Mississippian system______. 177 Itkillik glaciation______. ______174-175 Monotis.-...... 190 Ivishak member of Sadlerocb.it formation, character and distribution.__ 178-179 subdrcularis...... 190 fossils...... -...__-... .-.... .-...._...-...._..-.-. 186-187 Moraines.______174,175 sections . .. .____ .._.___... 179-182, pi. 21 Moms...... 208 Ivishak River area, glacial till..______175 Myalinas...... 185 Myophoria ...... 190 N Nanushuk group, Chandler formation...... _ 202-203 Juniper Creek section, Sadlerochit formation....______181 distribution.._-______.______...... _._.__._... 201,202 Jurassic rocks, correlation______191 historical geology______.______215 Jurassic system______191-195 history...... ______.__._.....____ _..-_. - 201 Juvavites...... 190 Ninuluk formation.....____.______.__._____._ - 203 petroleum possibilities.______...._ . 216,217 K Tuktu formation.. ______202 type localities______._. .. 201 Kavik River section, Sadlerochit formation______180 type sections....______- ._...__ 201 Sagavanirktok formation..______207-208 Ninuluk formation, historical geology...___------_... 215 Shublik formation______189 lithology ...... ___-_ . . 203 Kemik anticline, description and locality ______211-212 petroleum possibilities______....____ 216,217 Kemik Creek, type locality of Echooka member of Sadlerochit formation__ 178 Ninuluk bluffs, type locality, Ninuluk formation_____ . . 201 Kemik Creek area, petroleum possibilities______217 Nonionella...... 209 Kemik Creek section, Okpikruak formation....______196 austinana...... 208 Sadlerochit formation______181 O Kemik sandstone member of Okpikruak formation, type section____ 196, pi. 23 Okpikruak formation, age. ______.____ 197-198 petroleum possibilities______216,217 correlation..__ ...... _ 198 Kettle lakes...______.-______175 distribution....______..._...._.. ..._..... 196 Killik River, type locality, Chandler formation______201 fossils...... -. .-.. . . - 197,198 Killik tongue. See Chandler formation. history...... _____._..._____...... _.____... 195-196 Kingak Cliff, type locality of Kingak shale...______191 historical geology..______214 Kingak shale, age______192-193 lithology- ... . - 196-197 distribution..______191-192 petroleum possibilities..__...... _...... - _ . 216,217 fossils. ....______._ 192,193 section...... _...... _.... ._ _ 196, pis. 21,23 history..-.______191 Okpikruak River, type locality of Okpikruak formation. _ __ 195 historical geology______214 Ophiceras greenlandium...... - 187 lithology.--.______192 (Lytophiceras) commune...... 187 petroleum possibilities______216 tiheticum ...... __.__._...... 187 Kummel, Bernhard, fossil identification..______186,187,189,190,191 Ostrea (Liostrea) keilhaui...... 190 Otoceras ...... 187 _.___.__.__...... ____...... ______.....___ 187 Oxytoma...... - 193 Lakes, glacial origin.. ______173 Landing areas, aircraft______173 Leflingwell, E. de K., quoted______177,187,191,203 Panope...... 206 type section, Ignek formation______203 elongatissima...... -. . 205 Shublik formation______....____ 188 kissoumi...... 205 Lemuroceras__.______215 Parallelodon...... ______- . _ 197 Lima...... 190 Patton, W. W., Jr., quoted__.______-__ __. _ .....___._ 193-194,199 martini...... 190 type section, Fortress Mountain formation .___ 198-199 Line of culmination______211,212 Tiglukpuk formation______...__ 194 Line of depression. ______211,212 with Gryc, George, and Payne, T. G., quoted.______195-196,201,207 Linoproductus...... 186 Payne, T. G., with Gryc, George, and Patton, W. W., Jr., quoted.. 195-196,201,207 Lisburne group, character and distribution. ______177 Pecten ...... ______190 historical geology.______213 deformis..-...... 190 petroleum possibilities______216,217 (Entolium) yukonensis...... 190 INDEX 221

Page Pediment gravel..______209 Shublik formation, age....._____ 189-191 Pelosina...... 205,208 distribution...... ______._.______._..._ 188 Pentacrinns svbangularis...... 193 historical geology______.. . 214 Permian and Triassic systems. ______177-187 history...______. 187 Petroleum possibilities______216-217 lithology...... -.-.. ..-. ..-...... 188 Phillip Smith Mountains, origin of glaciers. ______174 petroleum possibilities..______. 216,217 Phricodothyris...... _._.______._____ 185 sections...______188,189, pis. 21,23 Phyttoceras...... 193 Shublik Island, type locality of Snublik formation______187 Physiographic provinces______172 Sirenites--...... ISO Physiography, drainage.-.____ ..______173 hayesi-...... 190 glacial history...______...______174-175 Smedley, Jack, fossil identification______... 186 topography______172-173 Spirifer...... 177 Pleuromya...... 202 rectangulus-...... 183 Flieatula...... 193,197 Spiriferetta arctica...... 185,186 Pogopuk Creek section, Sadlerochit formation______180-181 Spiriferina-...... 185,186 Polycoelia...... _____ 183 yukonensis-...... 190 Polypora...... 186 Spongodiscus...... 207 Posidmia arnata...... 193 Springs.______173 jacksoni...... 190 Squamularia...... 185 Precipitation...______._.__.___.___...... 171 Stenopora______.. . 185 Productus aagardi...... 185 Stratigraphy, correlation of units in region.______... 176 mammatus...... 184 Cretaceous system______... .. 195-207 multistriatus...... 184 Jurassic system______191-195 septentrionalis...... 183,184,185,186 Mississippian system______177 timanicus...... 183 Permian and Triassic systems. . 177-187 ProptychiUs...... 187 scope.______175-177 rosenkranizei...... 187 Tertiary and Quaternary systems __. 209 Pseudocadoceras grewingki...... 193 Tertiary system______207-209 Pseudogastrioceras...... 184 Triassic system______... 187-191 Pseudoliocera* whileavesi...... 193 Structure, favorable for petroleum production... 217 Pseudomargirafera aagardi...... 185 folds and faults...... __.______...... ______.. .. 210-213 Pterospermites conjunctions...... 208 subsurface______._____ . 213, pis. 24-26 Surficial deposits.__.______.___.. . - 209 Q Quaternary glacial advances______174-175 T Quaternary and Tertiary systems______209 Tancredia...... 193,205 R Temperature-______171 Radiolaria..______.__._____.___._____^...... 209 Terrace gravel_.. 209 Red Hill, type locality, Ignek formation- ______203, pi. 21 Terrane....______.___.__.___ 170-171 Reeside, John B., Jr., fossil identification______189,190,206 Tertiary and Quaternary systems.. . 209 Peineckeia stuebeli...... 193 Tertiary system______._ 207-209 Relief..-.______.______._.__.___.____ 172 Teusoteuthislongus...... ______. -- _-. .- 206 PhynchoneUa...... 190 Tiglukpuk Creek, type locality of Tiglukpuk formation....___ . 194 Phynchopora...... 185,186 Tiglukpuk formation, ag«______._ . 195 Ribdon River area, glacial features..______175 distribution-______. 194 RodnocLake.______.______173 fossils ...___...... _.-..-.- . - . - - 194,195 history...... ______.._.___ 193-194 historical geology______214 Sandlerochit formation, correlation______187 lithology.. ..-._.____..___ . . - 194 distribution-...______178 petroleum possibilities______-... 216 Echooka member______.. 178 sections.______194,195, pis. 21,23 historical geology______214 type locality.______...... ~ . - 194 history.....____.___..._____.______..._...... 177 Till...... ______._____.______.__.____.__ -__ 174,175 Ivishak member..______178 Topography______172-173 petroleum possibilities______216,217 Torok Creek, type locality of Torok formation.._ 199 sections.______179-182, pis. 21,23 Torok formation, distribution.______199 Sagavanirktok formation, age______208-209 fossils...______.______199,200,201 distribution...______207 history and type section______...... 198-199 fossUs...______.__...... _.____...... __...... _.. 208-209 petroleum possibilities______. 216 history.______207 type locality...... ______.._...... - 199 lithology....______207 Trachyceras...... 190 petroleum possibilities______216,217 (Protrachyceras)...... 190 sections... ______207-208, pis. 21,23 Trapa microphylla...... 208 Sagavanirktok glaciation. _. ______174 Triassic system______... 187-191 Sagavanirktok River to Lupine River, age of folding and faulting______211 Trochammina ribstonen&is...... 208 Saviukviayak River section, Shublik formation______189 Tropites stantoni...... -. 190 Scale of mapping.....______172 Tuktu Bluff, type locality, Tuktu formation... 201 Scope, geologic studies______175 Tuktu formation, age______202 Sections, Fortress Mountain formation______198-199,200, pis. 21,23 historical geology. . 215 Ignek formation______203,204-205, pis. 21,23 lithology .__.______...... 202 Okpikrual formation. ______196, pi 23 petroleum possibilities______216,217 Sadlerochit formation....______.______179-182,pis. 21,23 type locality______.... 201 Sagavanirktok lormation______207-208, pis. 21,23 Shublik formation..__..______...____.._.... 188,189,pis. 21,23 Type locality, Chandler formation 201 Tiglubpuk formation.______194, J95,pls. 21,23 Fortress Mountain formation..__ 198 Shaviovik anticline, description and locality______212-213, pi. 21 Ignek formation. ______203 petroleum possibilities______217 . _ . - 191 222 INDEX

Page U Page Type locality Continued USQS localities. .__.______...__.....__ 182, 183,184,185.186, Lisburne group______.______177 187,189,190,191,192,193,195,196,197,198,202,204,205,206 Nanushuk group...______201 Ninuluk formation..______201 Okpikruak formation______195 Verbeekiella...... 183 Sadlerocbit formation______177 W Echooka member______178 Waagenoconcha...... 184 Ivishak member______178 Weather data....______._._ ___ 171 Saga vanirktok formation..______207 Williams, James Steele, fossil identification.___.._.__ ...... 182-186 Shublik formation.______.___ 187 Wind...___.___.______._.__._.______171 Tiglukpuk formation.______193 Torok formation______199 Tuktu formation______.______201 Yoldia kissoumi. o