Areal Geology in the Vicinity of the Chariot Site Lisburne Peninsula Northwestern Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 395

Prepared on behalf of the U.S. Atomic Energy Commission Areal Geology in the Vicinity of the Chariot Site Lisburne Peninsula Northwestern Alaska

By RUSSELL H. CAMPBELL

GEOLOGICAL SURVEY PROFESSIONAL PAPER 395

Prepared on behalf of the U.S. Atomic Energy Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY WILLIAM T. PECORA, Director

Library of Congress catalog-card No. GS 66-262

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

Page Page Abstract. . _ __ 1 Stratigraphy Continued Introduction and acknowledgments. __. _. 1 Measured bedrock sections Continued Stratigraphy... _ . . ___ Permian and Triassic rocks west sections... 49 3 Shublik Formation (Triassic) 49 Stratigraphic and petrographic methods and Siksikpuk Formation (Permian) 51 terminology. ______. _ 5 Permian and Triassic rocks east sections. 51 Mississippian rocks . .______... 5 Shublik Formation (Triassic) . 51 Sedimentary rocks undivided ... _. .__ 5 Siksikpuk Formation (Permian) 52 Lisburne Group... 7 Jurassic or Cretaceous rocks. 53 Nasorak Formation 7 Telavirak Formation, partial section, Kogruk(?) Formation ______14 Niyiklik Creek 54 Tupik Formation. ____ .______18 Unconsolidated deposits 55 Permian and Triassic rocks ._ __ . 19 Tertiary or Quaternary deposits 55 Siksikpuk Formation (Permian)____.______._.._ 19 Ilyirak Gravel.. 55 Shublik Formation (Triassic) .__.______...... 20 Saligvik Gravel. 56 Jurassic or Cretaceous rocks.- 20 Quaternary deposits . 58 Ogotoruk Formation ... 20 Stream-terrace deposits 58 Telavirak Formation .. ._ 25 Chariot Gravel 58 Cretaceous rocks...... __ . . 27 Colluvium ...... 59 Kisimilok Formation._ _ _. 27 Lake, lagoon, and swamp deposits 59 Fortress Mountain (?) Formation . .... 28 Wind-deposited silt and sand 60 Measured bedrock sections ... 30 Flood-plain deposits 60 Mississippian rocks west sections ______30 Beach deposits of the present shoreline - 60 Lisburne Group. ______30 Geologic structure 61 Nasorak Formation. . 30 Thrust faults of> the western province 61 Sedimentary rocks undivided ______33 Folding and faulting of the eastern province 62 Mississippian rocks east sections 34 Age and origin of deformation. 63 Lisburne Group 34 Geomorphology - - 64 Tupik Formation .__ .. 34 Geologic history. - 65 Kogruk (?) Formation . _. 35 References cited . 66 Nasorak Formation._. __._ 44 Index. _.__. .-. ... _ .... . 69

ILLUSTRATIONS

Page PLATE 1. Geologic map and structure sections In pocket 2. Photomosaic of sea cliffs._.___._._.__. . .______..._.__ . In pocket FIGURE 1. Index of geologic mapping by the U.S. Geological Survey on behalf of Project Chariot _._.-..-.-.__.._._-__..-._.- ...... _.__-._..-...--_-._-__-_-_-._---._--_-----_ --- 2 2. Generalized columnar sections of strata exposed in sea cliffs. 10 3. Photographs of thin sections showing range of abundance of allochems in Nasorak biomicrites and fossiliferous micrites..._. ._ 11 4. Photographs of thin sections showing biosparite and dolomitized biomicrite from the Nasorak Formation _._...... _ . _ 12 5-12. Photographs of 5. Rhythmic interbeds of the Nasorak Formation 13 6. Even continuous beds of the Nasorak Formation 13 7. Coral head in the Nasorak Formation------. 14 8. Dolomitized fossiliferous micrite and biomicrite from the Kogruk(?) Formation .__.... __.______.______.____.______. ____ _ 15 9. Dolomitized sedimentary breccia in the Kogruk(?) Formation ...... 16 10. Intraformational breccia in the Kogruk(?) Formation 16 11. Relict current lamination in Kogruk(?) dolomite 17 12. Distinctive lenticular color mottling in Kogruk(?) dolomite 18

III IV CONTENTS

Page FIGURE 13. Generalized composite section of the Ogotoruk, Telavirak, Kisimilok, and Fortress Mountain(?) Formations ______-_-___ __ - - 21 14. Photograph of Ogotoruk Creek valley from Crowbill Point.______... _ 22 15. Photograph of phosphorite nodule in mudstone of the Ogotoruk Formation______23 16. Triangular diagrams of classification of impure sandstone 24 17-24. Photographs of 17. Bedding characteristics in the Ogotoruk Formation______25 18. Bedding characteristics in the Telavirak Formation______26 19. Bottom marks in the Telavirak Formation. . ______26 20. Bedding characteristics in the Kisimilok Formation ____ _ . 27 21. Bedding characteristics and outcrop aspect of some of the mudstone of the Kisimilok Formation ______28 22. Bedding characteristics in the Fortress Mountain(?) Formation - __ 29 23. Current ripple marks in the Fortress Mountain(?) Formation______30 24. Texture of spicular(?) chert in the Nasorak Formation ______47 25. Size distribution curves of samples of unconsolidated deposits __ 56 26-28. Photographs of 26. Bedding characteristics and structural features in the Telavirak For mation _ -- _ __ _ - __ - -_ 62 27. Fracture cleavage in the Ogotoruk Formation______.______63 28. Fracture cleavage in the Telavirak Formation^ ______63

TABLES

Page TABLE 1. Summary of sedimentary rocks and surficial deposits, Chariot site and vicinity, Alaska _____-__._.___.______.._.______.______-.____-______-__ _._ 4 2. Fossils collected from the Lisburne Group and the underlying mudstone-sandstone-limestone unit ______.___- ______8 AREAL GEOLOGY IN THE VICINITY OF THE CHARIOT SITE, LISBURNE PENINSULA, NORTHWESTERN ALASKA

By RUSSELL H. CAMPBELL

ABSTRACT uncertain origin (fluvial or marine) at high altitude, marine- Geologic mapping in support of Project Chariot covers terrace deposits at low altitude near the shoreline, lake and about 350 square miles on the southwest side of the Lisburne swamp deposits, wind-deposited silt and sand, and sand and Peninsula in northwestern Alaska. The area is bounded on gravel of the modern beach. the southwest by the Chukchi Sea and on the northeast by a roughly semicircular arc having a radius of about 15 miles INTRODUCTION AND ACKNOWLEDGMENTS from the Chariot site at the mouth of Ogotoruk Creek. In 1959 the U.S. Geological Survey was requested The exposed bedrock ranges in age from Early Mississip- by the U.S. Atomic Energy Commission to provide a pian to Cretaceous and crops out in paralled northeast- to geologic map at a scale of 1 inch to 1 mile (1:63,360) north-trending bands in which the rocks are, in general, suc cessively younger from west to east. The rocks are exclusively of the land area within a radius of 15 miles of the sedimentary and probably all marine. No angular unconfor Chariot site as a part of bioenvironmental studies in mities have been observed between bedrock units, and, al the vicinity of a proposed nuclear test excavation. though disconformities may separate several of the units, Geologic mapping in support of the bioenvironmental there is no local evidence of subaerial erosion or other indi studies program was done during the summer field cation of strongly emergent conditions between Early Mis- seasons of 1959 and 1960 and was an expansion from sissippian and Early Cretaceous times. Limestone and dolo mite beds of the Lisburne Group, locally of Mississippian the mapping done in 1958 (Kachadoorian and others, age, predominate in the western part of the area. The 1959; Sainsbury and Campbell, 1959) during pre underlying mudstone, sandstone, and limestone of Early liminary investigations of the site by the Geological Mississippian age are exposed chiefly on the extreme western Survey in support of technical site-selection studies side. The eastern half of the area is underlain by flysch by the Atomic Energy Commission. The area mapped facies mudstone and sandstone of Cretaceous and, possibly, Jurassic age. The presence of younger Cretaceous bedrock is roughly semicircular, bounded on the southwest units some distance to the north and east of the map area by the Chukchi Sea and on the northeast by the suggests that deposits as young as Late Cretaceous may have Kukpuk River. It extends along the coast for 15 been deposited and subsequently completely removed by miles in either direction from the mouth of Ogotoruk erosion. Creek: northwest as far as Kemegrak Lagoon and Although the structural relations are complex and westerly the north side of the Kemegrak Hills and southeast dips are common in the surface exposures, the gross distri bution of the units indicates a regional dip to the east or south about a mile beyond Pusigrak Lagoon. Along the east. The structure of the western half of the area is domi Kukpuk River it extends from the vicinity of Ogsa- nated by north-trending imbricate thrust faults along which chak in the northwest (downstream end) to Alolu- rocks of the Lisburne Group have been thrust eastward over krak on the southeast (upstream end) (pi. 1). The Lisburne and younger strata. The rocks of the eastern half area included is approximately 350 square miles and have been intensely folded, and broken by high-angle faults, giving a gross impression of plastic deformation. The struc includes all the Point Hope A-2 quadrangle as well tures of both halves of the area appear to be related to a as adjacent parts of the Point Hope A-l, B-l, and single major deformation of Late Cretaceous or early Ter B-2 quadrangles (fig. 1). The general location and tiary age. Both the thrusting and folding are interpreted accessibility of the area have been described by to be relatively shallow features that developed as a result Kachadoorian (1961, p. 9). of gravity gliding directed down the regional dip to the east. The Tertiary Period is represented by varied geomorphic The history of earliest exploration and geologic features that reflect a long and complex history of erosion work in the area has been described by Collier (1906, and deposition. Most of it was subaerial and fluvial, but p. 6), by Kindle (1909, p. 520-521), and by Smith marine erosion and deposition are represented by many fea and Mertie (1930, p. 4-9). Kachadoorian (1961, p. tures at low altitudes along the coast. In about half the area 6-8) has summarized the history of Geological Sur the bedrock is unconformably overlain by a thin veneer of unconsolidated deposits of Quaternary and, perhaps, late vey operations in the region on behalf of Project Tertiary age. The surficial deposits are chiefly colluvium, Chariot. The area of the geologic map (pi. 1) is in fluvial-terrace and flood-plain deposits, gravel and sand of cluded on the small-scale geologic maps of Collier 2 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

166°30' 166°00' 165°30' 165°00'

Outline of area of geologic map

FIGUBE 1. Index of geologic mapping by U.S. Geological Survey on behalf of Project Chariot.

1. Kachadoorian, Reuben, Campbell, R. H., Sainsbury, C. L., and Scholl, 2. Sainsbury, C. L., and Campbell, R. H., 1959, Geologic strip map of D. W., 1959, Geology of the Ogotoruk Creek area, northwestern part of the Kukpuk River, northwestern Alaska: U.S. Geol. Survey Alaska: U.S. Geol. Survey TEM-976, open-file report, open-file report; scale about 1:42,000. la. Plate 1, Geologic map and sections of Ogotoruk Creek area, by 3. Campbell, R. H., 1960, Preliminary geologic map and diagrammatic Reuben Kachadoorian, R. H. Campbell, C. L. Sainsbury, and D. structure sections of part of the Point Hope A-2 quadrangle, north W. Scholl; scale 1:12,000. western Alaska, in Kachadoorian, Reuben, and others, 1960, Geologic Ib. Plate 2, General bathymetry and marine geology of Ogotoruk investigations in support of Project Chariot in the vicinity of Cape Creek area, by D. W. Scholl and C. L. Sainsbury; scale about Thompson, northwestern Alaska preliminary report: U.S. Geol. 1:31,680. Survey TEI-753, pi. 2, scale 1:48,000. Ic. Plate 3, Engineering geology map of part of Ogotoruk Creek 4. Campbell, R. H., geologic mapping during summer 1960. area, by Reuben Kachadoorian and R. H. Campbell; scale 1:4,800. 5. Moore, G. W., geologic mapping during summer 1960. INTRODUCTION AND ACKNOWEDGMENT

(1906) and Smith and Mertie (1930). Data on the bedrock rubble and therefore do not yield much re rocks exposed to the west of the area of this report liable structural and stratigraphic data. Undisturbed have been taken from field notes of and discussions outcrops are generally confined to sea-cliff exposures with G. W. Moore and I. L. Tailleur, of the U.S. and stream cutbanks. Many of the unconsolidated Geological Survey, who examined those exposures in deposits display surface features that are easily dis 1960 and 1961, respectively. Tailleur (oral commun., tinguished on the vertical aerial photographs; for 1963) also provided additional information about the most of the area, the distribution of those deposits Mesozoic rocks along the Kukpuk River from his was mapped by photointerpretation controlled by examinations in 1963. J. T. Dutro, Jr., E. G. Sable, spot field examinations of reconnaissance density. and A. L. Bowsher (written commun., 1958) supplied By contrast, the photographic expression of the vari valuable information on paleontology and stratig ous bedrock units is less distinctive and may locally raphy from a brief reconnaissance of the Cape be deceptive; therefore, their mapped distribution Thompson area in 1951 and the Cape Lisburne- is, necessarily, more closely controlled by field ex Corwin Bluff area in 1953. Figure 1 lists the sources amination of the outcrops. Photointerpretation of of mapping data from which the geological map and the bedrock distribution was used only in a few sections were compiled. A summary report on the marginal areas, mostly in the southern part of the areal geology has been prepared (Campbell, 1966) drainage basin of Ilyirak Creek. In those areas for the U.S. Atomic Energy Commission volume on where the bedrock distribution was mapped by photo- bioenvironmental studies of Project Chariot, and interpretation based on field examinations of recon much of the text material and several illustrations naissance density, the unit label on the map is fol appear in both this report and the summary. lowed by a question mark. In July and August, 1958, fieldwork was done in Because the work was done as an integral part of the valley of Ogotoruk Creek by a party consisting investigations of much broader bioenvironmental of Reuben Kachadoorian, R. H. Campbell, C. L. studies and technical operations in connection with Sainsbury, and D. W. Scholl, geologists, and Currey Project Chariot, it is impossible to acknowledge by Lockett, cook and camp hand. Brief reconnaissance name all the many persons who contributed ma traverses were made along the coast in the company terially to the progress of the geologic mapping. of I. L. Tailleur, who visited the party in early July; Holmes & Narver, Inc., under contract to the U.S. in addition, Sainsbury and Campbell examined ex Atomic Energy Commission, and Geological Survey posures along the Kukpuk River for a distance of personnel, both in Fairbanks and from parties en about 20 miles between the mouth of Igilerak Creek gaged in other investigations at the Chariot site, and Alolukrak. During the summer seasons of 1959 provided helpful support without which the field- and 1960 the party engaged in areal mapping con work could not have been effectively done. I par sisted of R. H. Campbell, geologist, and D. R. Currey, ticularly wish to acknowledge the geologic work of geologic field assistant. Donald R. Currey, who served most ably as field The fieldwork was done chiefly by weasel and foot assistant for the 1959 and 1960 summer field seasons. traverse except along the sea cliffs between Crowbill Point and Cape Thompson, which were more easily STRATIGRAPHY accessible by small outboard motor boat. The field The bedrock of the map area consists entirely of mapping was done on vertical aerial photographs, in sedimentary strata, probably all deposited in marine 1958 at a scale of about 1:12,000 and in 1959 and environments. The oldest strata exposed are mud- 1960 at scales of about 1:46,000 and 1:41,000. stone, sandstone, and limestone of an unnamed unit Geology was transferred by radial planimetric plot of Early Mississippian age. These are succeeded by ter and by direct tracing (Campbell, 1961a) to topo the carbonate rocks of the Lisburne Group, locally of graphic base maps. The Point Hope A-2 quadrangle, Early and Late Mississippian age. The Lisburne 1:63,360 scale, was the only sheet published at the Group consists of three formations: the Nasorak time of the field investigations. Topography for the Formation, chiefly limestone; the Kogruk(?) For adjacent areas was available only as 1:50,000-scale mation, chiefly dolomite; and the Tupik Formation, compilation sheets. characterized by thick beds of black chert. The Lis Approximately half the area is covered by a thin burne Group is overlain by the argillite, chert, and veneer of unconsolidated deposits. In addition, shale of the Siksikpuk Formation of Permian age, nearly all the areas indicated as bedrock on the geo which is, in turn, succeeded by the shale, chert, and logic map (pi. 1) are areas of barren frost-heaved limestone of the Shublik Formation of Triassic age. AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

The Shublik is overlain by a very thick section of posits of unconsolidated gravel found at high alti monotonously similar flysch-facies mudstone and tudes may be as old as Tertiary. sandstone strata, in which four formations are rec Of the stratigraphic sections described in detail, ognized. They are, from oldest to youngest, the all but the Niyiklik Creek section of the Telavirak Ogotoruk, Telavirak, Kisimilok, and Fortress Moun Formation were measured along the magnificent sea- tain (?) Formations. The Fortress Mountain (?) is cliff exposures that extend nearly continuously from the youngest bedrock unit exposed in the map area. Crowbill Point to Cape Thompson (pi. 2). The sec The only clearly datable fossils found above the tions of Mississippian strata and the lower part of Shublik Formation are pelecypods of Cretaceous age the Imikrak Creek section of the Siksikpuk Forma within the Kisimilok Formation, but a thick non- tion were measured by mapping the sea cliffs on fossiliferous section intervenes between the top of oblique photographs at scales that were generally the Shublik and the lowest clearly Cretaceous hori between 50 and 100 feet to the inch. (The photo zon. The Jurassic Period, therefore, may be repre graphs used were taken at sea level and, insofar as sented. Table 1 gives a summary of the stratigraphy. possible, perpendicular to the shoreline. The scale The bedrock is concealed in more than half the for each was computed individually by taping or pacing a reference distance on the beach below the area by a few inches to several tens of feet of uncon- cliff.) The two sections of the Shublik Formation, solidated sedimentary deposits and vegetation. Peat, the upper part of the Imikrak Creek section of the sand, silt, and gravel occur as colluvium, windblown Siksikpuk Formation, and thex Niyiklik Creek sec deposits, lake and swamp deposits, flood-plain de tion of the Telavirak Formation were measured by posits, beach deposits, and terrace deposits at sev tape, pace, hand-level, and compass methods. Be eral levels. Most are of Quaternary age, but two de cause of the geographic continuity of most of the

TABLE 1. Summary of sedimentary rocks and surficial deposits, Chariot site and vicinity, Alaska

System Series Unit Name Character Thickness (feet)

Tertiary (?) and Unconsolidated deposits Colluvium; windblown sand and silt; fluvial 0-100 Quaternary terrace and flood-plain gravel, sand, and silt; marine gravel and sand; and peat. Lower (?) Fortress Mountain (?) Rhythmically interbedded silty mudstone and 3,000 + Cretaceous Formation sandstone, with minor conglomerate. Marine turbidites. Cretaceous Lower Cretaceous Kisimilok Formation Chiefly mudstone, with rhythmically inter- 5,000 + bedded sandstone abundant in basal zone. Buchia. Marine; turbidites common. Telavirak Formation Rhythmically interbedded sandstone and 5, 000 + (1,000?) mudstone, with minor conglomerate. Jurassic or Marine turbidites. Cretaceous Ogotoruk Formation Mudstone with interbedded siltstone and 5 f OOO±(l,000?) sandstone. Marine; turbidites abundant. Lower (?), Middle, Shublik Formation Limestone, shale, and chert. Monotis abundant 200 Triassic and Upper Triassic in some limestone beds. Marine. Permian Lower(?) Permian Siksikpuk Formation Argillite, chert, and minor shale. Marine. 400 ± -L/iBuumurmiiy ^ '. ) Tupik Formation Chert, mudstone, limestone, and minor 330 +(200?) argillite. Upper Mississippian GroupLisburne Kogruk(?) Formation Dolomite, limestone, and calcareous sedimen 3, 670 + (500?) tary breccia with minor chert. Marine fossils. Carboniferous Mississippian Nasorak Formation Chiefly rhythmically interbedded' limestone 2,200 and calcareous shale and minor interbedded Lower and Upper silty shale. Marine fossils; limestone tur Mississippian bidites (?). Sedimentary rocks Mudstone, sandstone, limestone, and minor 420 + (1,500?) undivided conglomerate. Marine and possible nonmarine. Base not exposed. STRATIGRAPHY measured sections, all of them have been grouped upper part of the sequence is well exposed in the sea together in a separate part of this report. cliffs a few hundred feet east of Cape Thompson (pi. 2A), where it is conformably overlain by the Lis STRATIGRAPHIC AND PETROGRAPHIC burne Group. Strata of the sequence are partly ex METHODS AND TERMINOLOGY posed along the back side of the beach between the The terminology used to describe the bedding Cape Thompson cliffs and Agarak Creek, in a few thickness is that recommended by Dunbar and Rod- cutbanks along Agarak Creek, in rubble exposures to gers (1957, p. 97). The color names conform insofar the west of Akoviknak Mountain, and, farther north, as possible to those of the National Research Council along the upper reaches of Nalakachak Creek. Rock-Color Chart (Goddard and others, 1948). The upper part of the unit as exposed just east of Terms designating terrigenous sedimentary-rock Cape Thompson (pi. 2A, fig. 2) consists of thin- types follow the terminology used by Williams, bedded to thin-laminated shaly fine to very fine Turner, and Gilbert (1954). The limestones and grained medium-gray sandstone and sandy siltstone dolomites have been classified according to the sys interbedded with dark-gray to medium-dark-gray tem and nomenclature proposed by Folk (1959) with silty shale and mudstone and a few interbeds of but two modifications: (1) the traditional 2.00-mm medium- to thick-bedded dark-gray limestone. The boundary was used to distinguish rudite and arenite, limestone interbeds are chiefly a medium-grained rather than the 1.00-mm boundary suggested by Folk poorly sorted biogenic calcarenite that has been (1959, p. 16); and, (2) calcite grains as much as partly dolomitized and partly silicified. The shales 0.031 mm in size that could not be determined as to and sandstones appear to be generally noncalcareous. origin whether recrystallized micrite or dust from However, a few of the sandstone beds contain dolo the abrasion of coarser allochems are commonly mite cement, and the mudstone beds are locally fos- present in minor amounts as an integral part of some siliferous. Tiny veinlets of calcite are common in matrix material and as such are included as "mi all the beds. crite" even though, in the strict sense proposed by The rocks that crop out along Agarak Creek are Folk, the term excludes material coarser than 0.004 very similar to those exposed just east of Cape mm. Thompson, and the fauna from both areas is domi The relative proportions cf calcite and dolomite nated by abundant small zaphrentoid corals. The in hand specimens and thin sections of the carbonate rocks exposed on the nearby beach, however, include rocks were determined by routine staining with more abundant thin beds of medium-gray and red Alizarine red S solution (Friedman, 1959), after dish-brown very fine grained quartz sandstone con preliminary optical and X-ray data on a pilot suite of taining scattered coalified plant fragments and, lo specimens indicated that the rocks were chiefly cally, ferruginous nodules and cement. In addition, calcite and dolomite, and that aragonite, gypsum, and the mudstone or shale interbeds are more strongly high-magnesium calcite were not present in de indurated and a sheen of disseminated very fine tectable amounts. The solution coats calcite with a grained mica has developed along a few bedding sur deep red stain, whereas dolomite remains uncolored. faces. In the exposures east of Akoviknak Mountain a MISSISSIPPIAN ROCKS few beds of coarse quartzose sandstone and a poly- Four formations of Mississippian age are shown mict fine pebble conglomerate are represented in on the geologic map (pi. 1). The lowermost is an un frost-heaved rubble. The conglomerate pebbles in named poorly exposed mudstone-sandstone-lime- clude some quartz, but they appear to be chiefly chert stone sequence, the oldest exposed within the map and fragments of other very fine grained rock. The area. It is overlain by the relatively pure limestone conglomerate is well sorted as to size and contains and dolomite beds of the Lisburne Group. The suc relatively little matrix, but locally is well cemented cession appears to represent continuous marine de with calcite and limonite(?). To the north, the poor position from Early to Late Mississippian time. outcrops along Angayukuk Creek are chiefly silty mudstone, locally shaly, with subordinate inter- SEDIMENTARY ROCKS UNDIVIDED bedded limestone. Some quartzose sandstone is pres The undivided sequence of mudstone, sandstone, ent in the rubble exposures north of Angayukuk and limestone of Early and Late Mississippian age Creek, and the outcrop in Kunuk Creek is a laminated crops out in the western part of the mapped area. The sandy siltstone. AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Farther north, along the upper reaches of both (written commun., 1963) as mostly of the genus major forks of Nalakachak Creek, the rocks are Tachylasma, associated with a few specimens of chiefly medium-gray to medium-dark-gray silty mud- probable Ufimia. Duncan (written commun., 1963) stone and claystone, generally thin bedded and lo notes that elsewhere Tachylasma is recorded only cally shaly, but in some places occurring in thick and from rocks of Permian age. This age is difficult to very thick beds. Sandy zones were not found. The reconcile with field observations indicating that the mudstones are locally fossiliferous and interbedded strata from which the fossils were thought to have with them are a few medium and thick beds of come are interbedded between Mississippian strata medium-gray fossiliferous limestone. represented by collections 60ACr-129 and 60ACr- The precise stratgraphic succession of the various 132. The fossils of 60ACr-130, however, are mostly rock types could not be established because of com silicified horn corals that were found as loose plex structure, poor exposures, and apparently rapid weathered fragments on a frost-heaved rubble sur facies changes. Only the upper 420 feet exposed in face and may be some sort of lag deposit from an the cliffs east of Cape Thompson were well estab eroded klippe of the Ibrulikorak thrust sheet rather lished stratigraphically . (See measured sections, p. than from the beds on which they lie. Alterna 33-34.) tively, if the fossils were from those beds, they The total exposed thickness of the mudstone- may represent tightly infolded or infaulted Permian sandstone-limestone unit is estimated to be on the rocks (though they do not resemble the known strata order of 2,000 feet. The base of the sequence is not of the Siksikpuk Formation elsewhere in the map exposed. The contact with the overlying Lisburne area) in the Ibrulikorak thrust sheet, of which there Group is gradational and the adjacent strata inter- could remain only a small klippe 5 or 10 feet thick. tongue. (See pi. 2A.) The mudstone-sandstone-limestone sequence cor The collections of marine fossils have been iden relates, at least in part, with the Mississippian coal- tified by J. T. Dutro, Jr., and Helen M. Duncan, of the bearing formation reported by Collier (1906, p. 18- Geological Survey, who report (written commun., 19) in exposures along the cliffs south of Cape Lis 1961) that the fauna in collections from near Cape burne. No coal beds have been found within the area Thompson is Early Mississippian in age. About 12 of plate 1, but Kindle (1909, p. 523-524) collected miles to the north, however, in the upper reaches of plant fragments from this area that were sufficiently Nalakachack Creek, fossil collections from the large and well preserved to be identified. Dutro sug mudstone-sandstone-limestone sequence (60ACr-129, gests (written commun., 1961) that the upper part of 60ACr-132, and 60ACr-132A of table 2) are re the mudstone-sandstone-limestone sequence as ex ported to be lower Upper Mississippian (Helen M. posed in the vicinity of Cape Thompson together Duncan, written commun., 1963; J. T. Dutro, Jr., with some of the lower beds of the overlying Lis written commun., 1965). This suggests that the con burne Group, is probably equivalent to the type tact between this predominantly terrigenous clastic Utukok Formation (Early Mississippian) in the unit and the relatively pure limestone of the overly western DeLong Mountains (Sable and Dutro, 1961, ing Lisburne Group may transgress time, becoming p. 591, 592) about 90 miles to the east, and that the progressively younger from south to north. It would plant-bearing sandstones of possible nonmarine indicate that something in excess of the 500 feet of origin would correlate approximately with the fossiliferous carbonate beds assigned to the Lower Noatak sandstone (Devonian and Mississippian). Mississippian part of the Lisburne Group at Cape The collections from the Nalakachak area were first Thompson has graded laterally northward into a pre thought to be f aunally equivalent to part or all of the dominantly mudstone section. This type of gradation Lower Mississippian part (basal 500 ft) of the is also suggested by Tailleur's observations (oral Nasorak Formation (Dutro and Duncan, written commun., 1965) that near Cape Dyer, to the north commun., 1962) and earlier papers (Campbell, west of the area of this report, the contact between 1965a; Campbell, 1966) reported the unit to be Early the lowest thick carbonate sequence and the underly Mississippian. The collections have subsequently ing mudstone unit lies at or very close to the bound been reported as most likely lower Upper Mississip ary between the Lower and Upper Mississippian. pian (Helen M. Duncan, written commun., 1965; J. T. Fossil collection 50ACr-130, also from the upper Dutro, Jr., written commun., 1965) so that the map reaches of Nalakachak Creek, appears to be anomal unit must now be regarded as of Early and Late ous. The fossils have been identified by Duncan Mississippian age. MISSISSIPPIAN ROCKS

LISBURNE GROUP pyrite concretions and a few pyritized fossils, the The Lisburne Group, here of Early and Late Mis- basal part of the upper member of the formation; sissippian age, is about 5,900 feet thick and consists above this the remaining part of the upper member chiefly of limestone and dolomite beds, in part cherty, is remarkably uniform in lithology and bedding char with variable but minor amounts of interbedded acteristics. The upper member is characterized by shale. The Lisburne, named by Schrader (1902, p. rhythmically interbedded thin-bedded to medium- 241), has been described in recent reports in which bedded dark-gray limestone and by thin-laminated to five recognizable subdivisions were described as Mli, very thin bedded silty calcareous shale. Shale in- M12, M13, M14, and M15 (Campbell, 1960a, pi. 3; terbeds generally decrease in both abundance and 1960b). The lower three of these units (Mli, M12, thickness progressively upward through the mem and M13) have been grouped together and named the ber. Nasorak Formation (Campbell, 1965a). The over The dark limestones of both the upper and lower lying unit (M14) is designated the Kogruk(?) For members of the Nasorak Formation are predomi mation because of its lithic similarity and partial nantly medium- to coarse-grained biomicrites. Poorly faunal equivalence to the type Kogruk Formation, sorted allochems, nearly all fossil fragments, con named by Sable and Dutro (1961) in the western stitute 20-80 percent of the rock; the remainder is a DeLong Mountains. The topmost unit of the Lis matrix of microcrystalline calcite and silt-sized detri- burne Group (M15 ) is mapped as the Tupik Forma tal calcite (fig. 3C, D). There are, however, a few tion because it is similar in lithology and strati- rare interbeds of coars'e-grained biosparite (fig. 4(7) graphic position to the type Tupik Formation in the in the upper member. Terrigenous debris is almost western DeLong Mountains (Sable and Dutro, 1961). entirely lacking. The most abundant recognizable The formation assignment was not determined for fossil fragments are crinoid columnals, undeter outcrops in a few small areas of poor exposure and mined echinoderm fragments, and fragments of complex structural relations; there, the Lisburne Bryozoa. Foraminifera were seen as sparse consti Group was mapped as undivided. tuents of a few beds. Fragments of other shelled organisms, probably chiefly brachiopods, are also NASORAK FORMATION common. Incomplete replacement by dolomite is The Nasorak Formation (Campbell, 1965a) is a common, though not prevalent (fig. 4A). Nodular limestone sequence named from typical exposures in limestone beds containing variable amounts of dark- the sea cliffs near the mouth of Nasorak Creek (pi. gray to black chert are common at some horizons. 2B), where nearly 1,800 feet of the upper part of the Dark chert is locally abundant in several zones, formation are nearly continuously exposed with rela chiefly as lenticular nodules and irregular angular tively little structural complexity. Most of the for masses in limestone beds. mation is also well exposed farther west in sea cliffs The interbedded calcareous shale is composed in the vicinity of Cape Thompson (fig. 2). (See meas chiefly of micrite, fossiliferous micrite, and bio- ured sections, p. 30-33, 44-49.) There the base is micrite, much of which apparently contains abundant exposed in conformable contact with the underlying silt-sized detrital calcite grains (fig. 3 A, B). Terri mudstone-sandstone-limestone sequence. Elsewhere, genous material is generally very rare throughout good exposures are limited chiefly to cutbanks along the formation and is represented chiefly by a small the Kukpuk and Ipewik Rivers. amount of clay (chiefly illite?) in the shale interbeds, The lower member of the Nasorak Formation con and minor amounts of very fine to fine quartz silt. sists of 165 feet of strata and is best exposed just Sand-sized terrigenous debris is almost entirely lack east of Cape Thompson. It consists of interbedded ing. dark-gray to grayish-black silt clay shale, locally cal The massive light-gray limestone of the Cape careous, and medium-gray to dark-gray cherty lime Thompson Member is chiefly a crinoid biosparite, stone. This zone is overlain by the Cape Thompson consisting almost exclusively of coarse sand- to fine Member, about 225 feet of massively outcropping pebble-sized crinoid stem fragments and columnals very thick bedded light-gray to light-olive-gray lime (fig. 45); locally it contains very minor amounts of stone. The Cape Thompson Member is resistant to very fine quartz silt and has been partly dolomitized erosion and forms the promontory of Cape Thomp and partly silicified. Bedding is expressed internally son, its type locality, for which it is herein named. It in this limestone by crinkly uneven discontinuous is succeeded by about 50 feet of very thick bedded laminae at generally regular intervals of half an inch grayish-black calcareous mudstone containing small to a foot in spacing. TABLE 2. Fossils collected from the Lisburne Group and the underlying mudstone-sandstone-limestone unit 00 [Sample locations: A. Nasorak Creek sea-cliff section; Ad, structurally disturbed part of Nasorak Creek sea-cliff section; B, Cape Thompson sea-cliff section; C, scattered localities, stratigraphic position determined by field-mapping correlations]

Lisburne Group

Nasorak Formation FormationTupik

Unnamed mudstone- Cape limestone-sandstone unil Kogruk(?) Formation Thompson Lower Upper member member member

o "" CO CO CM o os CM 5 CO CM OS S 35 OS lO CO 00 lO CO tN CO CM (N 59ACr138f-

'O -V U U O O 0 o Q Q Q Q 0 O O O PH PH PH PH PH 8984-PC PH 9058-PC 9056-PC 19055-PC PH PH PH PH 18975-PC PH PH PH PH ii -H PH PH 18968-PC -H PH 20214-PC PH 1 1 i l o 10 ci (N OS OS o (N >o 00 os A (N CO os (N 10 os os 88 S. 00 00 00 o SO » 10 OS OS os os 10 3. o OS OS os os §. os os OS OS o o OS OS OS tr 0 o os OS os b o U.S.G.S. upper Paleozoic locality Number. _ ____.._....__ 00 00 00 00 00 os os os 00 00 o 00 io os 00 00 00 os os b b 1 1 1 1 1 1 § § (N CM CM

Brachiopods: Brachiopods, indet. fragment.... __._ A p r. Avonia sp j^ Brachythyris aff. B. suborbicularis (Hall).. R n Ad H "Buxtonia" sp. ______AH Camarotoechid, indet. _ ...... Chonetes sp.__. ___.___._ .... A C aff. C. oklahomensis Snider .... Cleiothyridinal sp_ __... p AH Cleiothyridina aff. C. obmaxima (McChesney) _ . AH Composita sp ______p " Dictyoclostus" sp______A A R R Dimegelasma? sp. . ______R Echinoconchus sp _-..__ p A, A P Eumetriat sp A r. 0 Leiorynchus cf. L. carboniferum Girty. _. Q C Lingula sp ______A Linoproductust sp______. C Martinial sp______A C Orthotetid, indet_ Orthotetes'! sp___--_ n Productoid, indet. fragment., _. ______A A A R C Punctospirifer sp ______AH A C Schizophoria sp- ______AH Spiriferoid, indet fragment. A R C C Spirifer sp... _____ r. AH P AH R C S. keokuk Hall.... ______R A AH A

Corals : c c Ad A A A C R Cyathoclisia? sp_-______A A A A A A r, R A A A A A r, r, A r, A A A A A AH R R R 0 A A A' A R A r. AH R r, 0 A R R 0 AH r, Bryozoans: A r, r, A r. A A A AH r, 0 A A A r A r, AH A A AH AH r, r, VI CQ r, CQ 0 AH 0 0 Echinoderms: A r, 0 0 0 AH R AH r, r, r, r, A r, A r, Gastropods: A R r, Pelecypods: AH r, Other fossil material reported: R r, A

Foraminifera: A for petrographic study) . 10 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Agate Rock to Amaktusak Creek ^S^S^. URASSIC ETACEOUS EXPLANATION OR Ogotoruk Formation ««^ 1 I / / ' y 'r l( ^

0 DISCONFORMITY

PERMIAN Siksikpuk Formation

DISCONFCIBMITVt?! - - -. ' ' ' ==7- ':== ' ^= Mudstone, argillite, Sandstone Tupik f ')(.')(' X and shale

i 'j' i ', ,-.4 ~ /^ '/*=-' / VERTICAL SCALE FEET i- 2000 "^= r-^ =1*7 ' l-^"?" / /<==> // /=>/ / / ~/ ' /*=>'/ ~ / ^ L i L ~r- T i ^ ' 7 1 ~~7~~ / / / / - 1000 y / / Kogruk(?) - Formation - /<=> / 7s"/ - 500 / / / / LisburneGroup ~^ 1 ^T ^-T -

PPIAN / ' ;J ; != L o ' / / / -7 ^ ^ S^ MISSISS / -, ^7 : r~

/ / CO/ / / / /

7 1 ^ 1 L F^^ ;. /"g/' - / ' ;' -^ T^T^T""

Thompson Member

Lower SALIGVIK THRUST FAULT ' - _J^! ' U -E= member =^^^ -^=^^- Sedimentary rocks --=^z^iz I - undivided _ . _

______,______~ ' ' ' i J IBRULIKORAK THR

FIGURE 2. Generalized columnar sections of strata exposed in sea cliffs. CQi i "0 I

FIGURE 3. Thin sections showing general range of abundance, size, and kinds of allochems in the most common rock types of the Nasorak Formation. The dark areas on the right side of each section have been stained with Alizarine red S. A, A partly dolomitized Bryozoa-bearing laminated micrite. The chief fossil constituent is fragmental Bryozoa. Approximately 25 percent of the rock is dolomitized, chiefly as a very finely crystalline replacement of the matrix. Dolomite also occurs as thin rims around some of the fragmental fossil allochems. (This section is cut very nearly parallel to the bedding.) 59ACr-8a-l/7. B, A medium-grained crinoidal biomicrite containing only about 15 percent allochems, nearly all of which are echinoderm fragments, in a micrite matrix; shows a few late calcite veinlets. The prominent veinlike structure that crosses the section near its middle is perhaps best interpreted as the copriolite-filled path of a worm or other burrowing organism. The extremely dark nature of the matrix is due chiefly to its very fine grain size and to an excessive thickness of the thin section; it may also be partly due to a few percent of finely divided inclusions of clay and (or) carbon. A small amount of secondary silica occurs at rims around a few of the calcite fossil fragments. 59ACr-4A. C, A medium-grained crinoidal biomicrite. Relatively abundant allochems, nearly exclusively echinoderm and bryozoan debris, poorly sorted as to size, with a matrix of calcite mudstone that perhaps contains a few percent clay. The rock is virtually pure calcite, possibly containing 1 or 2 grains of medium to fine quartz silt; some of the dirty material of the matrix may be inclusions of very fine clay mineral particles. 59AO-3. D, A coarse-grained crinoidal biomicrite containing approxim ately 30 percent loosely packed fossil allochems in a micrite matrix; may contain a minor amount of clay. Both clasts and matrix are nearly pure calcite. 12 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

FIGURE 4. Thin sections showing biosparite and dolomitized biomicrite from the Nasorak Formation. The right side of each section has been stained 'with Alizarine red S. A, A partly dolomitized coarse-grained crinoidal biomicrite from the lower member of the Nasorak. Although the coarse-grained fossil allochems are closely packed, the original intergranular material was probably micrite matrix that is now nearly completely dolomitized. This is indicated by the finely crystalline size of the dolomite and a few small relict patches of micrite. The allochems are only slightly embayed and replaced; most of them remain nearly pure calcite. The late veinlets are calcite. 59ACr-118B. B, Coarse-grained crinoidal biosparite of the Cape Thompson Member. Closely packed coarse- and very coarse grained fossil allochems, with clear calcite spar overgrowths and cement; contains a negligible amount of matrix micrite. Virtually no dolomite nor terrigenous material occur in this section. 5ACr-120A. C, Coarse-grained biosparite, a rock type that occurs only rarely in the upper member of the Nasorak. The rather poorly sorted fossil allochems contain a relatively small amount of matrix micrite, and most of the intergranular space has been filled with sparry calcite cement. There is no identifiable terrigenous silt and only extremely minor amounts of replacement silica rim a few of the fossil clasts. 59ACr-9b#l. MISSISSIPPIAN ROCKS 13

Many of the dark limestone and shale beds of the upper member occur as rhythmically interbedded pairs that appear to be graded beds (fig. 5). Although there is little obvious gradation of size within the in-

FIGURE 5. Rhythmically interbedd~d limestone and shaly limestone of the FIGURE 6 Continuous evenly bedded limestone beds of medium thickness, Nasorak Formation. The upper part of the unit 18 of the section meas Nasorak Formation. Unit 16 of the section measured in the vicinity ured near the mouth of Nasorak Creek (see "Measured bedrock sec of the mouth of Nasorak Creek (see "Measured bedrock sections," p. 48). tions," p. 48). The thick-bedded zone is the basal part of unit 17. Note the contact -with the underlying unit 17 and the distinctively no Tops of beds are to the left. dular aspect of unit 17 in section and on bedding surfaces. dividual limestone beds, their basal contacts are 8 in. thick) lenticular heads of coral were observed commonly sharp and continuous, whereas their in the section (fig. 7). They probably do not indicate contacts with the overlying shale are finely inter- such shallow depth as to preclude their association tonguing and gradational. Some of the beds pinch with turbidity-current deposits. The nodular pinch and swell, a few to the extent of being nearly discon ing and swelling of some beds may be due to differ nected alined nodules. But the beds are continuous ential compaction. and, at least in gross aspect, parallel, with alternat The contact with the underlying mudstone-sand- ing pinches and swells of successive beds compensat ing each other. There are also a few zones of even-, stone-limestone sequence is gradational and probably continuous-, medium-bedded limestone that have only intertonguing. The contact with the overlying rocks minor amounts of interbedded shale (fig. 6). The designated the Kogruk(?) Formation is gradational. shale interbeds are thinly laminated and many It was arbitrarily drawn at the base of the lower laminae are well expressed by the presence of flat- most thick-bedded dolomite seen in the sea-cliff sec tion west of the mouth of Nasorak Creek. Although lying fragments of leafy bryozoan fronds. the Kogruk(?) Formation is not exposed in the sea The graded bedding, poor sorting of allochems, and cliffs west of Cape Thompson, the middle part of the continuous and parallel stratification (Haff, 1959) Nasorak is exposed in both sets of cliffs, and correla suggest that many beds of the Nasorak were de tions of stratigraphic position may be made on posited from turbidity currents. Fossils that do not nearly a bed-to-bed basis (fig. 2). The thickness show some indication of fragmentation in transport measured from the sea-cliff exposures totals about are rare; only a few small (as much as 2 ft long and 2,100 feet. Elsewhere, structural complexities and 14 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

ern DeLong Mountains (Sable and Dutro, 1961, p. 592). Apparently, then, the beds of the Nasorak Formation represent continuous deposition from Lower Mississippian at the base to Upper Mississip pian at the top. The formation is accordingly as signed an Early and Late Mississippian age; the lower member and Cape Thompson Member are in cluded in the Lower Mississippian part, and the boundary between the Lower and Upper Mississip pian lies in the lower part of the upper member.

KOGRUK(?) FORMATION The name Kogruk (?) Formation is applied to a thick dolomitic sequence (unit M14 of Campbell 1960a, b) in the Lisburne Group of this area because its stratigraphic position is similar to that of the Kogruk Formation described by Sable and Dutro (1961, p. 592) in its type area in the western DeLong Mountains. There seems to be a general similarity of bedding characteristics, rock types, and fauna, al though the rocks designated Kogruk (?) in the Lis burne Peninsula contain much more abundant dolo mite than the type Kogruk of the DeLong Mountains. The Kogruk (?) Formation is continuously and al most completely exposed along the sea cliffs west of the mouth of Nasorak Creek; probably only a few hundred feet of beds are missing because of high- FIGURE 7. Coral head (Lithostrotionetta) in upper part of Nasorak Forma angle faulting. It is also exposed in the sea cliffs of tion. Tops of beds to left. Notebook is 8 by 5 inches. Crowbill Point and is intermittently well exposed along the cutbanks of the Kukpuk River. In rubble lack of exposures prevent reliable measurements of outcrops the rocks of the Kogruk (?) Formation may thickness. be distinguished from the underlying Nasorak For Fossils are relatively abundant. The identifiable mation by their generally lighter color and the rela forms are chiefly Bryozoa (predominantly fene- tive abundance of large blocky debris. The strate), brachiopods, horn corals, lithostrotionoid Kogruk (?) may be distinguished from the younger corals, and a few endothyroid Foraminifera. The overlying units by its generally bolder topographic megafossils were examined by J. T. Dutro, Jr., and relief, lighter color, and the general absence of Helen M. Duncan, of the Geological Survey, who con close-spaced bedding traces on rubble ridges. clude (written commun., 1961) that collections from The Kogruk (?) Formation consists predominantly the upper 1,500 feet of the Nasorak Formation (table of light-gray to dark-gray very finely crystalline to 2) indicate equivalence to the lower part of the medium-crystalline dolomite, interbedded with gen Alapah Limestone (Upper Mississippian) of the cen erally minor amounts of dark-gray partly dolomitized tral and eastern Brooks Range, and those from the limestone. Most of the rocks are pure carbonate with lower approximately 500 feet indicate correlation virtually no terrigenous minerals, but a few beds of with the upper part of the Wachsmuth Limestone carbonate mudstone contain a small amount of fine (Lower Mississippian). They also conclude that quartz silt and possibly some clay. Undolomitized the basal 165 feet of the Nasorak contains fossils that calcite allochem remnants are rare in most of the correlate with those of the Utukok Formation dolomite beds, but many contain some identifiable (Lower Mississippian) of the western DeLong Moun allochem ghosts (fig. 8). Probably their original tains (Sable and Dutro, 1961, p. 591-592) and that composition is best indicated by comparison with the the fossils of the remaining 1,935 feet of the Nasorak partly dolomitized limestone interbeds. The lime are equivalent to those in part of the Kogruk Forma stone beds consist chiefly of detrital fossil fragments tion (Lower and Upper Mississippian) of the west ranging in size from fine sand to fine pebbles. In MISSISSIPPIAN ROCKS 15

FIGURE 8. Dolomitized fossiliferous micrite and biomicrite from the Kogruk(?) Formation. A, Finely crystalline biogenic dolomite. The fossil structures are cross sections of leafy bryozoan fragments. The left half of the section has been stained with Alizarine red S and virtually no calcite is present. The rock is nearly pure dolomite. This is a clear example of a completely dolomitized Bryozoa-bearing micrite showing considerable preservation of the original sedimentary fabric, now expressed as variations in the crystal size of the dolomite. 59ACr-54. B, Photomicrograph of part of the same section shown in figure 16A, showing detail. The fossil allochems have been dolomitized to medium-crystalline subhedral to euhedral dolomite, rela tively clear and free of inclusions. The matrix has been dolomitized to a finely crystalline anhedral to subhedral material containing abundant minute inclusions. 59ACr-54. C, Fine and coarsely crystalline biogenic dolomite. An excellent example of a completely dolomitized biomicrite. Medium- to coarse-grained fossil allochems (a few of which are readily identifiable as crinoid columnals) have been dolomitized to coarsely crystalline dolomite, whereas the original calcite mudstone matrix has been dolomitized to finely crystalline dolomite. The rock apparently originally contained between 20 and 25 percent fossil allochems. 59ACr-29A. 16 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

(fig. 9). This brecciated unit is bedded within the Kogruk( ?) and may be a sedimentary breccia or pos sibly a cave breccia, though it appears to be too wide spread to be entirely cave breccia. There are also several thinner zones in the upper half of the Kogruk(?) that contain intraformational breccia (fig. 10). Irregular interbedding of thin, medium, thick, and very thick beds is characteristic of the Kogruk(?) Formation. Very thick beds of crystalline dolomite, one as much as 140 feet, are relatively abundant. The bedding planes are commonly even and are both con tinuous and discontinuous. Dolomitic rocks com monly show small-scale horizontal and gently cross- stratified internal current lamination that is ex pressed in exposed rocks as color banding of very low contrast, probably a result of minute impurities (fig. 11). Striking lenticular color mottling was seen in one very thick dolomite bed (fig. 12). A total thickness of 3,670 feet was measured along the sea cliffs (pi. 2B). (See measured section, p. 35- 44.) An unknown thickness has been faulted out of the upper part by three high-angle faults, one of which forms the contact with the overlying Tupik Formation of the Lisburne Group. From detailed

FIGURE 9. Texture and clast size in dolomitized sedimentary breccia in the Kogruk(?) Formation. The clasts are dark-colored chert and lighter colored dolomite, in a matrix of medium crystalline dolomite and only minor relict (?) calcite micrite. some, the interstitial material is very finely crystal line dolomite, and dolomite locally rims and replaces irregular patches of the clasts themselves. In other beds the interstitial material consists of a matrix of microcrystalline or very finely crystalline calcite lo cally with variable amounts of very finely crystalline dolomite. Light-gray and dark-gray chert commonly forms nodules as well as continuous and discontinu ous layers in some limestone beds. The chert content varies greatly from bed to bed and also along the strike of individual beds. About 140 feet below the top of the unit is a zone of breccia about 400 feet thick composed of very small to very large fragments FIGURE 10. Intraformational breccia in unit 9 of the Kogruk(?) Forma of chert and dolomite in a microcrystalline to finely tion section measured in sea cliffs west of the mouth of Nasorak Creek. Note internal current lamination in light-colored dolomite as well as in crystalline matrix that is predominantly dolomite the large breccia fragments of dark-colored dolomite. MISSISSIPPIAN ROCKS 17

FIGURE 11. Relict current lamination in Kogruk(?) dolomite. A, Megascopic relict current lamination in dolomite. Unit 9 of the section of the Ko- gruk(?) Formation measured in sea cliffs west of the mouth of Nasorak Creek. B, Thin section of rocks shown in A. At this scale the lamination, though still visible nearly perpendicular to the long crack in the thin section, is ghostly and poorly defined. The rock is chiefly an anhedral mosaic (though a few euhedral faces occur) of coarse- to medium-crystalline dolomite. The left edge of the section has been stained with Alizarine red S, which brings out the late calcite veinlet and irregular intergranular patches of late(?) calcite spar. Apparently, an original lamination, formed by the sedimentary alternation of fine and coarser grained calcarenite or carbonate mudstone, was preserved through dolomitization, now being expressed as alternations of dolomite of different crystal size and variations in abundance of inclusions. 59ACr-67a. C, Relict current lamination in dolomitized calcilutite. Finely crystalline laminated dolomite, with lamination expressed by the variation in crystal size. From unit 20 of the section of the Kogruk(?) Formation measured in sea cliffs west of the mouth of Nasorak Creek. 59ACr-56a. 18 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

the type Kogruk of the western DeLong Mountains. The presence of Late Mississippian fossils in the Kogruk (?) and in the upper part of the underlying Nasorak Formation suggests that all the rocks as signed to the Kogruk (?) in this area are of Late Mississippian age, whereas the type Kogruk Forma tion of the western DeLong Mountains is considered to be of Early and Late Mississippian age (Sable and Dutro, 1961, p. 592).

TUPIK FORMATION The Tupik Formation (unit M15 of Campbell, 1960a, b) is the topmost formation of the Lisburne Group. The Tupik Formation was named after ex posures on Tupik Mountain in the western DeLong Mountains area (Sable and Dutro, 1961, p. 592, 593). Although complete equivalence of the type Tupik to the rocks of this area is not clearly demonstrable, the name Tupik is herein used because fossil collections indicate approximate faunal equivalence, because of general similarities in rock type, $nd because of its stratigraphic position at the top of the Lisburne Group. The Tupik Formation is best exposed in sea cliffs FIGURE 12. Distinctive lenticular color mottling of unit 16 of the Ko about 1^ miles west of the mouth of Nasorak Creek gruk (?) Formation in section measured west of the mouth of Nasorak Creek. The notebook is 8 by 5 inches. (pi. 2B). Elsewhere in the map area, it is only locally found at the top of the Lisburne Group, partly be structure sections it is estimated that probably not cause of poor exposures. Where present, the Tupik more than 500 feet of beds that should be assigned to may be distinguished from the underlying strata by the Kogruk( ?) Formation are missing at the sea-cliff its generally darker colors, more subdued topo exposures because of the faulting. The thickness graphic expression of the rubble slopes formed in it, elsewhere could not be reliably determined because and the relative abundance of black chert. It is dis of complex structure and poor exposures. tinguished from the overlying Siksikpuk Formation Fossil material consists of abundant crinoid col- by darker color and slightly greater resistance to umnals and undetermined echinoderm debris and erosion. subordinate Bryozoa, horn corals, small colonial The Tupik Formation consists chiefly of inter- corals (including lithostrotionoid corals, particularly bedded grayish-black chert, dark-gray to medium- near the base), brachiopods of several species, and at dark-gray carbonate mudstone including dark-gray least one blastoid (table 2). The fossil collections to medium-dark-gray very finely crystalline to micro- were examined by J. T. Dutro, Jr., and Helen M. crystalline limestone, and subordinate interbedded Duncan, of the Geological Survey, who report (writ greenish-black to dark-greenish-gray chert and very ten commun., 1961) that the fossils appear to cor fine to finely crystalline dolomite. The limestone beds relate with those in the upper part of the Alapah contain variable but generally small amounts of Limestone of the central Brooks Range. Several col nodular chert. The dark-gray to medium-dark-gray lections represent a Chester-type assemblage of carbonate mudstone is locally partly dolomitized; a bryozoans, brachiopods, and echinoderms. Dutro and few beds of the mudstone contain several percent of Duncan also note that the collections correlate terrigenous quartz silt, and shaly fissility is common broadly with the Gigantoproductus zone of the cen in the beds of the lower half of the section exposed. tral Brooks Range and that Gigantoproductus has Approximately the lower half of the beds exposed been found in similar rocks near Cape Lisburne. in the sea cliffs consist of thin-bedded interbedded They further suggest (written commun., 1961) that limestone and calcareous shale. Thick beds of chert the Kogruk(?) Formation and most of the underly and carbonate mudstone are more common in the ing Nasorak Formation are faunally equivalent to upper half. Most of the chert is in beds 0.1 foot to MISSISSIPPIAN ROCKS 19

2 feet thick with slightly uneven but generally con PERMIAN AND TRIASSIC ROCKS tinuous bedding surfaces. The carbonate mudstone The Siksikpuk Formation of Permian age and the and very finely crystalline dolomite beds range from Shublik Formation of Triassic age, widely recognized less than 1 inch to 3 feet in thickness, but most com along the southern foothills of the Brooks Range, are monly are 7 inches to 1 foot thick. The beds are gen readily recognizable in this area. Here the two erally continuous, parallel, and of even thickness. units are thin and commonly occur together in tightly About 330 feet of beds are exposed in the sea cliffs folded and complexly faulted relations. The resulting just east of the mouth of Imikrak Creek. (See meas distribution is complex and the units are undifferen- ured section, p. 34-35.) Where well exposed in the sea tiated in many parts of the map (pi. 1) where, be cliffs, the contacts with both the underlying cause of lithologic similarities of some of the rocks Kogruk(?) Formation and overlying Siksikpuk For of both units, the two are indistinguishable. The mation are high-angle faults. Farther inland, how rocks are best exposed in sea cliffs at Agate Rock and ever, geometric relations of the contacts with the near the mouth of Imikrak Creek (pi. 2), where sec Kogruk(?) and Siksikpuk, although poorly exposed tions were measured. The upper part of the Sik on rubble slopes, indicate accordance, and structure sikpuk Formation and all the Shublik Formation are sections suggest that the total thickness of the Tupik exposed in the sea cliffs at Agate Rock; only the basal probably does not much exceed 500 feet. The sporadic few feet (or at most a few tens of feet) of the distribution of this unit at the top of the Lisburne Siksikpuk is missing from the exposures near the may be accounted for by rapid facies changes along mouth of Imikrak Creek. The formations strike the strike, by a disconformity at the top of the Lis northward from the coast and are intermittently ex burne, or possibly by a combination of both phenom posed along that trend. Both crop out discontinu- ena. Certainly no appreciable angular unconformity ously along the east side of Crowbill Point and occurs at the top of the Lisburne Group in this area. Saligvik Ridge. They are also exposed along the Fossils are very rare, but a meager fauna was col upper and lower reaches of Ilikrak Creek and in one lected (table 2) from one carbonate mudstone bed small area along the Ipewik River about a mile north and detrital fragments are common in some of the of its junction with the Kukpuk. microcrystalline limestone beds. The fauna, consist ing of gastropods and brachiopods, was examined by SIKSIKPUK FORMATION (PERMIAN) J. T. Dutro, Jr., of the Geological Survey, who re The Siksikpuk Formation was named by Patton ports (written commun., 1961) that the age is Late (1957) from exposures in the central Brooks Range. Mississippian. Overall similarity of lithology, fauna, and stratig The absence of a fauna of Pennsylvanian age con raphic position indicates that the name is appropri tributes to the interpretation that the contact be ately used in this area. tween the Lisburne and the Siksikpuk is discon- Greenish-gray argillite is the predominant rock formable. On the other hand, no fossils have been type of the Siksikpuk Formation. It contains variable found at a higher stratigraphic position in the Tupik but generally very minor amounts of quartz silt and than about 150 feet below the top, and it is possible very fine sand. Near the base there is a zone of that the Pennsylvanian Period is represented by a black gypsiferous(?) shale. Greenish-gray chert is rather thin zone of nonfossiliferous rocks. The rela common as interbeds in the argillite at several hori tively thin, though widely distributed, sequences that zons, the most striking of which is the topmost zone represent the Permian and Triassic Periods suggest of the formation where argillite is greatly subordi the possibility that the Pennsylvanian too is repre nate to chert. Some of the argillite is calcareous in sented by a thin stratigraphic section. Although an widely ranging proportions, and a few such beds con erosion surface underlies the basal Permian rocks in tain marine fossils. Most of the chert appears to be a silicified argillite. Several red-colored zones within some parts of northern Alaska (Patton, 1957, p. 42), the argillite look like interbeds from a distance; in no strong angular discordance has been reported; detail, however, the red-green boundary is highly ir nor do the Permian rocks contain widespread de regular and cuts across bedding. The reddish bands posits of clastic material attributable to derivation appear to represent oxidized permeable zones within from the Lisburne Group. It would thus seem fairly the argillite. certain that the absence of a Pennsylvanian fauna The argillite and chert are commonly medium to does not reflect major emergence and erosion during thin bedded. The thickness of the topmost cherty that period. zone is variable, suggesting a slight disconformity at 20 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA the top of the formation; however, no angular dis orange fossiliferous limestone. Near the top, the cordance with the basal beds of the overlying Shublik most prominent rock type is thin- to medium-bedded Formation was observed and the variable thickness pale-brown fossiliferous limestone like that inter- may, alternatively, result from a facies change. The bedded in the underlying zone. The limestone zone is total thickness of beds assigned to the Siksikpuk is overlain in places by a thin zone of greenish-gray about 400 feet. argillite much like that of the underlying Siksikpuk A meager fauna was collected from two horizons Formation. About 200 feet of beds are assigned to in the lower part of the Siksikpuk Formation. The the Shublik Formation. lowermost, collection 59ACr-88f, comes from a single The limestone is characteristically a pelecypod fossiliferous limestone bed about 4 inches thick, in- coquina with a matrix of variably silicified micro- terbedded in argillite that lies beneath a zone of black crystalline calcite and perhaps some clay. It crops shale. The locality is about 250 feet east of the mouth out distinctively as thin resistant very light colored of Imikrak Creek, where the rocks are exposed in sea- ridges that are generally easily recognized on aerial cliff section. The other collection, 59ACr-89f, con photographs. sists of calcareous fossils in greenish-gray argillite The fossils appear to be exclusively pelecypods of beds from sea-cliff outcrop exposures just west of the the genera Monotis and Halobia that characterize the mouth of Imikrak Creek. Both collections have been Shublik Formation over much of northern Alaska. examined by J. T. Dutro, Jr., of the Geological Sur These fossils suggest a Late Triassic age for the vey, who provided the following lists of fossils (writ upper beds (Keller and others, 1961, p. 190). The ten commun., 1961): Shublik in the Killik-Itkillik area (Patton, 1959), Collection 59ACr-88f (18992-PC): has been assigned to the Early (?), Middle, and Late Sochkineophylluml sp. Linoproductoid brachiopod, indet. Triassic, the age designation herein retained. Martiniopsisl sp. Squamulariat sp. JURASSIC OR CRETACEOUS ROCKS Straparolhis (Euomphahis) sp. Rocks of Jurassic or Cretaceous age include the Collection 59ACr-89f (18993-PC): two lithologic units that make up the lower 10,000 Linoprodnctust sp. Cancrinella sp. feet of a very thick sequence of flysch-facies mud- Plicatiferal sp. stone and sandstone that underlies Ogotoruk Valley Martiniopsisl sp. and the ridges and valleys to the east. The lower unit, Spirigerellat sp. in which mudstone predominates with minor Straparolhis (Euomphahis) alaskensis Yochelson and amounts of interbedded sandstone, is the Ogotoruk Dutro Amphiscapha! sp. Formation. The upper unit, in which sandstone and Dutro (written commun., 1961) considers the age of mudstone are interbedded in more nearly equal these collections as "probably Early Permian." Thus, amounts, is the Telavirak Formation (fig. 13). In the Siksikpuk Formation is herein considered to be early reports on the area (Kachadoorian and others, of Early (?) Permian age. 1959, p. 19; Sainsbury and Campbell, 1959; and Campbell, 1960a, pis. 2, 3) most of these beds were SHUBLIK FORMATION (TRIASSIC) tentatively assigned to the Tiglukpuk Formation of The Shublik Formation was named by Leffingwell Jurassic (?) age. Although perhaps partly correlative (1919) from exposures in the Canning River region, with the type Tiglukpuk Formation of Patton where it was in part redefined by Keller, Morris, and (1956a) in the central Arctic Foothills province of Detterman (1961, p. 187-191). General similarities northern Alaska, the lack of f aunal evidence, distinc of lithology, fauna, and stratigraphic position indi tive marker horizons, or physical continuity on which cate that the name is appropriately applied to the stratigraphic equivalence might be determined sug rocks mapped as Shublik in this area. gests that local names for the units are more appro The Shublik Formation of this area consists of priate. The Ogotoruk and Telavirak Formations three and, locally, four lithologic zones. At the base were, therefore, named by Campbell (1965b, c). there is a zone several feet thick of black shale with (They correspond respectively with the informal a few rare interbeds of dark-gray to black cherty units KJi and KJ2 of Campbell, 1961b, p. 35.) limestone. This grades upward to a zone that con sists chiefly of thin-bedded dark-gray to black cherty OGOTORUK FORMATION limestone and interbedded black shale with a few The Ogotoruk Formation is named for exposures rare interbeds of thin-bedded pale-brown to grayish- along Ogotoruk Creek and its tributaries, its type JURASSIC OR CRETACEOUS ROCKS 21

EXPLANATION

Graded beds

UNCONFORMI TY Mudstone, siltstone, and shale containing phosphorite nodules

Conglomerate

VERTICAL SCALE FEET

DISCONFORMITY(?>

FIGURE 13. Generalized composite section of the Ogotoruk, Telavirak, Kisimilok, and Fortress Mountain (?) Formations. 22 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA locality (Campbell, 1965b). The Ogotoruk Forma to the bedding. A prominent red-weathering layer tion is the bedrock of the immediate Chariot test site occurs about 3 feet above the base. Similar claystone area, and the proposed test excavation is entirely beds (generally less intensively sheared) have been within this unit and its thin veneer of overlying un- noted at several horizons within the Ogotoruk For consolidated deposits. Its topographic expression is mation in other areas where the stratigraphic posi generally one of low relief, and, indeed, its general tion cannot be well established, but in general these extent is rather well defined by the wide, low valley zones appear to be restricted to approximately the of Ogotoruk Creek (fig. 14) and the continuation of lower 1,000 feet of the formation. Phosphorite nod that valley northward to the Kukpuk River. The ules are locally common, but sparsely distributed, in lowermost 300 feet of the Ogotoruk Formation is the dark-greenish-gray claystone and dark-gray also exposed in the low sea cliffs for about a mile east mudstone beds of several stratigraphic horizons. of Agate Rock (pi. 2) and in intermittent exposures They occur chiefly as small oblate spheroids as large extending northward from that coastal area. A thin as 1 foot in diameter and 6 inches thick (fig. 15). sliver of rocks assigned to the Ogotoruk Formation The rocks may be generally classified as arkosic or is exposed in a faulted zone cut by the Kukpuk River. feldspathic wackes, as modal analyses generally fall The rocks of the Ogotoruk Formation are chiefly near the boundary between feldspathic wackes and dark-gray mudstone interbedded with variable arkosic wackes on the triangular diagram of Wil amounts of siltstone and very fine grained to liams, Turner, and Gilbert (1954, p. 292). (See fig. medium-grained dark-gray and brown sandstone. 16A.) The sand and coarser silt grains are predomi The dark-gray mudstone, sandstone, and siltstone nately angular to subangular quartz, chert, plagio- appear to differ only in grain size and relative abund clase feldspar, and rock fragments. The grains are ance of clay matrix. The base of the formation, where poorly sorted as to size, and the intergranular space exposed just east of Agate Rock, consists of several is tightly filled with a matrix of clay and fine silt. feet of dark-greenish-gray claystone which is com Most of the fine silt appears to be finer fragments of monly highly fractured and sheared roughly parallel the same minerals and rocks as those of the coarser

Tetavirak Hills

FIGURE 14. Subdued topography of the valley of Ogotoruk Creek. The valley is cut into the relatively soft rocks of the Ogotoruk Formation (KJo), which is overlain by only a thin veneer of unconsolidated deposits. Across the valley the more resistant rocks of the Telavirak Formation (KJt) are capped by an old surface of low relief into which younger valleys have been cut. View southeastward from above Crow bill Point. JURASSIC OR CRETACEOUS ROCKS 23

i"?»- and illite in variable proportions. Common in many rocks is very finely crystalline mica (sericite?), most of which appears to be authigenic. In addition, ir regular small patches of authigenic quartz occur in the rocks, and there is also apparently some authi genic albite in the matrix material. The phosphorite nodules are chiefly microcrystalline anhedral aggre gates of grains that are too fine to resolve in thin sec tion ; they give an apatite X-ray diffraction pattern. The mudstone is in massive to thin-laminated beds. In many places thin-bedded to thin-laminated mudstone is rhythmically interbedded with thin-bedded and thin-laminated siltstone and sandstone. A few thick beds of sandstone occur at irregular intervals (fig. 17). Mudstone beds commonly have well de veloped close-spaced fracture cleavage and are lo cally slaty. The rhythmically interbedded units commonly show graded bedding, and the thinly lami nated mudstones commonly show small-scale gentle cross-lamination as well as a size gradation in the relative abundance of silt and fine sand. The base of many of the sandstone and silty sandstone beds show bottom marks which are chiefly casts of scattered small pits and irregular depressions in the underly FIGURE 15. Phosphorite nodule in mudstone of the Ogotoruk Formation. ing mudstone. Flute casts and groove casts are rare Straight edge of scale case is 2 inches long. and invariably small. Convolute bedding is found in many of the mudstones. Where exposed, the thin in detrital fragments. The quartz grains include both dividual beds appear to be relatively continuous and clear quartz some grains showing shadowy extinc parallel. These bedding characteristics, together tion and quartz with variable amounts of inclu with the poor sorting of grain sizes, suggest that sions. The chert grains are almost exclusively mi- many of the strata of the Ogotoruk Formation were crocrystalline anhedral aggregates of quartz. The deposited from turbidity currents. feldspar is exclusively plagioclase, all of which ap The Ogotoruk Formation was seen to be in normal pears to be within the albite range. For the most contact with the underlying Shublik Formation only part the plagioclase occurs as single clear grains and along the sea cliff near Agate Rock. The contact re as granular aggregates of very fine crystalline feld lations there are obscured by shearing in the basal spar ; in some grains it occurs as a felty intergrowth strata of the Ogotoruk, but locally the contact ap of feldspar microlites with chloritic(?) clay min pears to be a disconformity of very low relief. East erals. The latter suggest derivation from altered of Saligvik Ridge the main north-trending band of fine-grained mafic igneous rock, but the grain size is exposures is most commonly bounded on the west generally too small to provide definitive evidence. by rocks of the Lisburne Group which have been The rock fragments are chiefly of claystone and silt- thrust over the Ogotoruk, but in a few places the stone of the same composition as the matrix, and contact is a high-angle fault with Permian and Tri- many of them are deformed by adjacent monomin- assic strata. The contact with the overlying Tela- erallic grains as if they had been deposited in a plas virak Formation is gradational. The total thickness tic condition. A few of the rock fragments consist of of the Ogotoruk Formation is not accurately known. quartz-sericite and quartz-albite intergrowths; this Because of the complex structure, lack of exposures, suggests possible derivation from a metamorphic and lack of marker beds or key horizons, repetitions terrain. of lithologic types by stratigraphic alternation cannot The composition of the interstitial matrix of the be discriminated from structural repetition, and only sandstone appears identical to that of the mudstone. an approximation can be made. A total thickness of X-ray diffraction studies of the clays of the matrix about 5,000 feet is estimated from the structure sec indicate that the clays are almost exclusively chlorite tions (pi. 1). 24 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Quartz, chert, quartzite Quartz, chert, quartzite

10 /QuartX irj

Feldspars Unstable fine-grained Feldspars Unstable fine-grained rock fragments rock fragments .4. Ogotoruk Formation; modes of three thin sections B- Telavirak Formation; modes of two thin sections

Quartz, chert, quartzite Quartz, chert, quartzite

Feldspars Unstable fine-grained Feldspars Unstable fine-grained rock fragments rock fragments C. Kisimilok Formation; modes of two thin sections D. Fortress Mountain(?) Formation; two modes of one thin section

FIGURE 16. Classification of "impure sandstones" or "wackes," after Williams, Turner, and Gilbert (1954, p. 292), showing plots of modes of thin sections of Cretaceous and Jurassic or Cretaceous rocks. The diagrams indicate only the three major constituents of sand or coarse silt size; the presence of 10 percent or more argillaceous matrix is understood as an essential constituent. Mode 60ACr-58-I (D) was computed with detrital calcite included as matrix and closely resembles modes of sandstones from the underlying Cretaceous and Jurassic or Cretaceous formations. Mode 60ACr-58 II (D) was computed with detrital calcite included with the unstable rock fragments.

Fossils are extremely rare, and the few found were formation east of Agate Rock are nondiagnostic; but nondiagnostic as to age. The Ogotoruk, together with they conclude, from inferred correlation with the the Telavirak Formation, lies between known Upper Kingak Shale of Jurassic age (Leffingwell, 1919, p. Triassic and Lower Cretaceous strata. Dutro, Sable, 119-120), that the age is probably Jurassic and pos and Bowsher (written commun., 1958) report that sibly Early Cretaceous. The Ogotoruk Formation is microfossils found in one sample near the base of the therefore assigned a Jurassic or Cretaceous age. JURASSIC OR CRETACEOUS ROCKS 25

mudstone is probably the dominant rock type. Phos phorite nodules are prominent minor constituents in the mudstone beds of several stratigraphic horizons. A single discontinuous bed of polymict coarse pebble conglomerate, locally containing some material of cobble size, was found near the base of the Telavirak. The lithology is nearly identical to that of the rocks of the Ogotoruk Formation. The sandstone is commonly fine- to very fine grained and of f eldspathic or arkosic wacke composition (fig. 16B). The clays are chiefly chlorite and illite. A few sandstone beds contain relatively abundant coarse sand- and silt- sized fragments of coalified plant debris. The pebbles of the conglomerate bed are chiefly fine-grained graywacke, mudstone, chert, and cherty limestone, but at least one small pebble consists of a felty intergrowth of plagioclase microlites in a chloritic(?) matrix. Characteristically, the beds of the Telavirak For mation are rhythmically interbedded mudstone and siltstone or very fine grained to medium-grained sandstone (fig. 18). The sandstone beds are gener ally graded, showing a general decrease in the maxi mum grain size upward. The graded beds are com monly bounded at the base by sharp contacts with the underlying mudstone, whereas their contacts with the overlying mudstone are commonly grada- FIGURE 17. Bedding characteristics in the Ogotoruk Formation. Thick- tional and intertonguing on a very fine scale. Low- bedded sandstone and interbedded slaty mudstone. Steel tape is extended about &y2 feet. angle small-scale cross-lamination is moderately common in the sandstone beds. Nonlinear organic bottom marks are common at the base of many of the TELAVIRAK FORMATION sandstone beds; groove casts and flute casts are rare The Telavirak Formation (Campbell, 1965c) is (fig. 19). Cycles, consisting of a single sandstone named from the Telavirak Hills, which lie along the bed at the base grading to mudstone at the top, range coast at the southernmost end of a north-northeast- from 1 inch to 11/2 feet in thickness ; sandstone gen trending belt of outcrops of this map unit. This belt erally makes up from one-half to three-fourths of the is bounded on the west by Ogotoruk Valley and on the thickness of the cycle. Individual graded beds are east by the western flank of Sigrikpak Kidge. The commonly continuous and parallel through the limits topographic expression of the Telavirak is much of individual outcrops (distances of as much as 200 bolder than that of the underlying Ogotoruk Forma ft locally). However, the beds appear to change tion but is similar to adjacent parts of the overlying facies rapidly along the strike, commonly within Kisimilok Formation. Upland areas of bedrock rub distances of a mile or less. The poor sorting, parallel ble are abundant, and relatively deep narrow valleys stratification, graded bedding, convolute bedding in dissect an old upland erosion surface of low relief the laminated mudstones locally, and general ab and cut both along and across the bedrock strike sence of shallow-water phenomena suggest that these (fig. 14). Fresh outcrops of the formation are limited rocks were deposited from turbidity currents. almost exclusively to stream cutbanks and therefore are small and disconnected. Fracture cleavage in the mudstone is common in The rocks of the Telavirak Formation are very the Telavirak Formation, as it is in the underlying similar to those of the Ogotoruk Formation. The Ogotoruk Formation. In both formations the frac Telavirak is distinguished chiefly by more nearly ture cleavage that is developed in the mudstone equal proportions of sandstone and mudstone and commonly does not penetrate adjacent sandstone generally thicker bedding of the sandstone. Although beds. This is best illustrated in the rhythmically in sandstone is abundant, massive and thin-laminated terbedded sandstone and mudstone that is found in 26 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

FIGURE 19. Bottom marks in the Telavirak Formation. Straight edge of tape case is 2 inches long.

known key horizons, and the many structural com plexities. However, one partial section of at least 5,000 feet was measured along Niyiklik Creek, a north tributary of Ogotoruk Creek. The contact relation between the Telavirak and the underlying Ogotoruk Formation is gradational. The contact was drawn at the base of the lowermost thick zone of rhythmically interbedded mudstone and thick-bedded sandstone; because of facies changes at the base of this zone, the contact is probably not everywhere at precisely the same stratigraphic horizon. The contact between the Telavirak and the overlying Kisimilok Formation appears con formable in poor intermittent exposures in the east ern headwaters of Ogotoruk Creek, but north and south of that area structural discordance suggests it lies along high-angle faults. No diagnostic fossils have been found in the Tela virak Formation. Two collections of Lebenspuren were examined by P. E. Cloud, Jr., who concludes that the fossils are long-lived types. He notes (writ ten commun., 1961) the association of similar forms with flysch-facies rocks in other areas and suggests B that the fauna may represent deposition at bathyal FIGURE 18. Bedding characteristics in the Telavirak Formation. A, Rhyth or even possibly abyssal depths. Two other collec mically interbedded thin- and very thin bedded mudstone and very fine grained sandstone in nearly equal proportions. B, Thin-bedded to thinly tions of poorly preserved fragmentary fossil material laminated mudstone with subordinate rhythmically interbedded very thin were examined by David L. Jones, of the Geological bedded siltstone or very fine grained sandstone. Scale on opposite bank of stream is 6 inches long. Survey, who reports (written commun., 1961): M 1106. Field No. 60ACr-22f. Indeterminable plant and shell scraps. both formations but that is more abundant in the M 1112. Field No. 60ACy-46f. Buchiat sp. Telavirak (fig. 28). As the Telavirak Formation is overlain by strata The thickness of the Telavirak, like that of the of Early Cretaceous age and, together with the Ogo underlying Ogotoruk Formation, is not accurately toruk Formation, lies above Upper Triassic rocks, known because of the scarcity of exposures, lack of it is assigned a Jurassic or Cretaceous age. 27

CRETACEOUS ROCKS posed in low hills along the coast, to the east of the The two youngest bedrock units of the area are mouth of Kisimilok Creek. the Kisimilok Formation and the overlying unfos- Massive to thinly laminated medium-dark-gray to siliferous sequence that is questionably assigned to dark-gray mudstone is the dominant rock type of the the Fortress Mountain Formation. Fossils of Early Kisimilok Formation. A zone containing relatively Cretaceous age have been found in the Kisimilok, and abundant interbedded sandstone, possibly as much regional stratigraphic associations indicate that the as 2,000 feet thick, is prominent at the base of the Fortress Mountain (?) strata also are of Cretaceous unit. It locally contains abundant fossils. It is over age. lain by 3,000 feet or more of mudstone containing only rare thick sandstone interbeds. The sandstone- KISIMILOK FORMATION bearing facies exposed along the coast east of Kisimi The Kisimilok Formation was named for its ex lok Creek are of uncertain stratigraphic position. posures in the vicinity of Kisimilok Creek (Camp They may be nonfossiliferous facies of the basal bell, 1965d), whose drainage basin is almost entirely zone, returned to the surface by folding; or reflect within the rocks of this unit. It is exposed in rubble rapid facies changes from sandstone to mudstone suboutcrops on low hills along the coastline from a northward; or represent sandstone-bearing facies in point about a mile west of the mouth of Kisimilok a zone overlying the thick mudstone zone. Only the Creek to the east edge of the map area. The expos relative abundance of fossils, the sequence of thick ures along the coast form the base leg of the crude zones of markedly different proportions of sandstone L-shaped outcrop pattern that extends northeastward and mudstone, and a few subtle changes in bedding up the valley of Kisimilok Creek to the Kukpuk characteristics and lithology serve to distinguish this River and an unknown distance beyond. The rocks formation from the older ones beneath it. are best exposed in stream cutbanks of southeast- In detailed lithology as well as bedding charac and northwest-flowing tributaries of Kisimilok teristics, the rocks of this formation are very similar Creek and along some cutbanks of the Kukpuk River to those of the underlying Telavirak and Ogotoruk (fig. 20). The topographic expression is variable. A Formations. The sandstones are graywackes of the resistant zone containing relatively abundant sand feldspathic- or arkosic-wacke type (fig. 16C), and stone beds underlies the high north-trending Sigrik- the mudstones have about the same composition as pak Ridge, and a thick zone of softer mudstone un the matrix material of the sandstone with chlorite derlies the broad valley of Kisimilok Creek. Resistant and illite as the predominant clays. Fossils are im sandstone-bearing facies are also intermittently ex- portant distinguishing constituents where present. In the sandstones, detrital calcite sand grains form a very minor but significant accessory. A few percent of K-feldspar was noted in one of the fossiliferous basal sandstones of the Kisimilok Formation, but the bed is discontinuous and K-feldspar was not found in any of the other sandstones of this formation that were sampled and examined. The mudstones, par ticularly in the thick zone with relatively few sand stone interbeds, are commonly less silty and more argillaceous than those of the underlying formations. Phosphorite is generally less common in the mudstone of the Kisimilok Formation than in that of the underlying Telavirak and Ogotoruk Formations. In deed, one 1-inch thick lens of material that resem bled the phosphorite of the lower units was sampled and found to contain no phosphorite; it was instead about 70 percent siderite, the remainder being; fine quartz silt and clay. FIGURE 20. Bedding characteristics and river cutbank outcrop aspect in Although most of the mudstone is massive or the Kisimilok Formation on the Kukpuk River. Rhythmically interbedded sandstone and mudstone, standing nearly vertical, truncated by a stream- thinly laminated like that found in the older forma cut terrace that is overlain by a relatively thin veneer of stream-terrace tions, a significant amount of it shows a rhythmic deposits. View looking eastward to the northeast side of the river. The cutbank is about 40 feet high. interbedding of thin- to medium-bedded strata in 28 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA which grading is expressed as a minor color change Formation. Owing to the poor exposure, the possi from medium gray at the base to dark gray at the bility that this contact is an unconformity cannot be top. The color gradation represents a gradual de eliminated; however, the generally smooth curvature crease upward in the amount of fine sand and silt of the contact and the indications that both units are included in the mudstone. These mudstones com discordant with the contact suggest that it may be monly lack both bedding-plane and fracture-cleavage an eastward-dipping thrust fault. The contact be fissility and crop out with a conchoidally fractured tween the Kisimilok Formation and the underlying aspect (fig. 21). Most of the sandstone is rhythmi Telavirak Formation is apparently conformable, but cally interbedded with the mudstone in locally con for much of its length it is faulted. tinuous and parallel graded beds. As in the Ogotoruk The total thickness of the Kisimilok Formation and Telavirak Formations, the bedding characteris here could not be accurately determined because of tics and textures suggest that many of the beds were the complex structure, absence of marker horizons, deposited from turbidity currents. and poor exposures ; but probably at least 5,000 feet The contact between the Kisimilok Formation and of strata are represented, and perhaps several thou the overlying Fortress Mountain (?) Formation is sand feet more if the contact relations with the exposed only in rubble suboutcrop within the area of overlying Fortress Mountain (?) Formation are cor plate 1. On the basis of distinctive lithologic differ rectly interpreted. ences, the position and configuration of the contact Fossils, almost entirely pelecypods of the genus can be drawn fairly accurately; the map shows it as Buchia (=Aucella), are abundant locally in the a relatively smooth curve through an arc of nearly lower zone of interbedded mudstone and sandstone 90°, concave to the east. The general structural and sparsely distributed in the overlying mudstone, trends in the Kisimilok Formation locally parallel but most of the beds of the Kisimilok Formation are the contact, but in many places they appear to inter relatively barren of fossils. The collections have been sect it at an acute angle. The strikes and axes within examined by David L. Jones, of the Geological Sur the Fortress Mountain(?) Formation locally parallel vey, who reports (written commun., 1961, 1963) : the contact, particularly in areas immediately adja M 1107. Field No. 60ACr-49f Buchia, sp. indet. Not cent to it, but the dips indicate that those beds im well enough preserved for positive identifi mediately adjacent to the contact are not necessarily cation but could be B. crassicolis or B. oken- the lowermost beds of the Fortress Mountain (?) sis. Age: Neocomian. M 1108. Field No. 60ACr-53f Probably is B. sublaevis. M 1109. Field No. 60ACr-75f Bnchia, sp. indet. Could be B. okensis but too poorly preserved to be sure. M 1110. Field No. 60ACy-llf B. subokensist M 1111. Field No. 60ACy-12f Lebenspuren. Feeding marks? No age significance. M 1113. Field No. 60ACy-48f Worm tubes, snail, and indeterminable clam fragments. Jones concludes that the collections containing B. "sublaevis" are probably from early Valanginian rocks, and that the probable presence of B. subokensis suggests a Berriasian age for some of the section (written commun., 1963). On the basis of the pelecypod fauna, the Kisimilok Formation is as signed an Early Cretaceous age. A correlation with part of the Okpikruak Formation of Early Cretace ous age (Gryc and others, 1951, p. 159-160) is sug gested on the basis of the Buchia species, following the zonation of Imlay (1959, p. 165).

FORTRESS MOUNTAIN (?) FORMATION FIGURE 21. Bedding characteristics and outcrop aspect of some of the mudstone of the Kisimilok Formation. Thin- to medium-bedded clayey The Fortress Mountain Formation was defined in mudstone in which bedding is expressed chiefly as color banding (of va the Colville River region by Fatten (1956b). Several rious hues of gray). Note also the lack of distinctively resistant strata and the conchoidal fracture. Straight edge of tape case is 2 inches long. general similarities of lithology and bedding char- CRETACEOUS ROCKS 29 acteristics between the youngest bedrock formation exposed in this area and the rocks called Fortress Mountain Formation a few tens of miles to the north in the Utukok-Corwin region (Chapman and Sable, 1960, p. 71-73) suggest that the unit may be suitably designated the Fortress Mountain (?) Formation. This formation is exposed in only one relatively small region along the east edge of the mapped area. Its outcrops are mainly limited to the cutbanks of the Kukpuk River and tributary stream, although bed ding traces composed of the coarser rubble of more resistant rocks are locally common on ridge tops. The topographic expression of the formation is distinc tively less subdued than that of the thick mudstone zone of the Kisimilok Formation that underlies it in most places. Interbedded silty mudstone, siltstone, and sand stone are the dominant rock types with minor amounts of conglomerate. Thinly laminated to medium-bedded dark-gray silty mudstone predomi nates, but rhythmically interbedded thin- to thick- FIGURE 22. Bedding characteristics in the Fortress Mountain (?) Forma bedded sandstone is abundant in some zones as much tion. Rhythmically interbedded thin-bedded to laminated mudstone and somewhat subordinate sandstone. White coatings on some surfaces are as several hundred feet thick. The sequence differs calcite veinlets that formed along joints. from the underlying Kisimilok Formation in its generally more abundant sandstone content and in the greater abundance of silt and fine sand in the a general absence of shallow-water phenomena mudstones. The sandstones of this formation differ which strongly suggest deposition from turbidity from the sandstones of the Kisimilok and Telavirak currents. The internal lamination of the sandstone Formations in the character of the internal lamina commonly is cross stratified on a very small scale at tion, in the size and character of bottom marks, and low angles, and the angles commonly are distinctively to a minor degree in lithology and color. higher than those of the internal cross-lamination of The mudstone commonly is slightly but distinc the graywackes in the older formations. These rocks tively micaceous. The sandstone is graywacke of differ slightly from the turbidites of the older units the arkosic- or feldspathic-wacke type (fig. 167)), in in that current ripple marks were observed in sev many respects similar to the graywackes of the older eral localities (fig. 23), and linear sole markings rocks of the area; but it is brownish gray to medium were seen, chiefly of the variety described elsewhere dark gray, and is commonly characterized by minute by Kuenen (1957, p. 235-242) as flute casts. discontinuous uneven internal laminae of dark-gray The thickness of the Fortress Mountain (?) For mudstone. The sandstone beds differ slightly from mation is not known in this area. A combination of those of the underlying units in that detrital calcite poor exposures and complex structures prevents a sand grains form a characteristic minor accessory. reliable measurement of thickness, or even an evalua A polymict pebble conglomerate bed exposed along tion of relative stratigraphic position of zones. About the Kukpuk River contains relatively abundant chert 3,000 feet of beds are probably represented, based and altered mafic igneous rocks. Many of the sand on interpretations of structure sections (see struc stone beds contain as much as several percent of in ture sections, pi. 1). As noted above, the contact be terstitial calcite cement, and secondary calcite is tween the Fortress Mountain (?) and Kisimilok relatively abundant as thin veins and veinlets along Formations appears to be a thrust fault. No bedrock fracture surfaces, chiefly joints. formations younger than the Fortress Mountain (?) As in the underlying units, the rhythmically inter are exposed in the mapped area. A few tens of miles bedded sandstone-mudstone sequences display graded to the north, in the Utukok-Corwin region, the For bedding, poor sorting, continuous parallel stratifica tress Mountain is succeeded by the marine Torok For tion (fig. 22), load casts, convolute internal lamina mation, which is overlain by marine and nonmarine tion of mudstones, small-scale slump structures, and strata of the Nanushuk Group, in turn overlain by 30 AREAL GEOLOGY, VICINITY OP CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Thickness (feet) Unit Cumulative locally) rhythmically interbedded with variable amounts of dark-gray calcareous shale and (or) shaly micrite. In accessible (in upper part of cliff) but very similar to units 1-6 of eastern Nasorak sec tion (pi. 2B)______320+(?) 320+(?) 2. (Mlnu-f(?) of pi. 2A) Shale and (or) shaly carbonate mudstone; interbedded limestone. Dark-gray shaly micrite or calcareous shale with thin interbeds of medium-dark-gray to dark-gray biomicrite or fossiliferous micrite. May in clude some chert as one zone contains "nodular" beds close ly similar to those of unit 8 of eastern Nasorak section. Unit inaccessible in cliff. FIGURE 23. Current ripple marks in the Fortress Mountain (?) Formation. Great general resemblance to Slight asymmetry of ripples indicates current in direction shown by units 7, 8, and 9 of eastern arrow. section ______115±30 435±30+(?) 3. (Upper part of Mlnu-b, c, d, e, the nonmarine beds of the Colville Group, collectively of pi. 2A) Limestone and subordinate shaly carbonate of Early to Late Cretaceous age (Chapman and mudstone and (or) calcareous Sable, 1960). It seems reasonable to infer that at shale. Medium-gray to medi least some of them originally overlay the Fortress um-dark-gray biomicrite and Mountain (?) Formation in the Ogotoruk Creek area fossiliferous micrite, regu but that they have been removed by erosion. larly, and in many zones rhythmically, interbedded No fossils were found in the rocks of the Fortress with subordinate thin beds Mountain (?) Formation within the mapped area. and partings of calcareous The rocks appear to be lithologically equivalent to shale and (or) shaly to thin the Fortress Mountain Formation in the Utukok- laminated micrite. Calcareous Corwin area (Chapman and Sable, 1960, p. 71-73); beds locally partly dolomitized. Only basal beds accessible at they are therefore tentatively assigned a probable beach level in proper strati- Early Cretaceous age. graphic position. Although higher beds dip down to beach, strong local folding nearly MEASURED BEDROCK SECTIONS parallel to shoreline obscure position within unit. Zone MISSISSIPPIAN ROCKS WEST SECTIONS near base contains very minor [Sections measured at sea-cliff exposures at Cape Thompson and nearby, by R. H. Campbell and D. R. Currey, August 1959] interbedded shale; limestone is coarse-grained crinoid bi LISBURNE GROUP omicrite that in places shows NASORAK FORMATION "crinkly" internal lamination greatly resembling that of Erosion surface, top not exposed. unit 16 of eastern Nasorak Thickness section. Other bedding char (feet) Unit Cumulative acteristics also similar; the Upper member of the Nasorak For principal differences are that mation (Mlnu) : the rocks here contain a great 1. (Mlnu-g, h of pi. 2A) Limestone er proportion of medium- and and calcareous shale or shaly fine-grained fragmental fossil carbonate mudstone. Medium- allochems. Unit generally re gray to medium-dark-gray bi- sembles and probably corre omicrite (may be dolomitized lates with units 10-16 of MEASURED BEDROCK SECTIONS 31

Thickness Upper member of the Nasorak Formation Continued (feet) Thickness Unit Cumulative (feet) corals, in beds as much as 6 Unit Cumulative eastern Nasorak section. ft thick. May have originally 59ACr-126, 59ACr-127 are been shaly to thin internally chips taken to represent laminated, but internal lami lithology __ -___.______230 665±30+(?) nation now masked by close- 4. (Lower part of Mlnu-b, c, d, e, spaced sheared (slickensided) of pi. 2A) Limestone, chert cleavage surfaces. A few thin and shale. Dark-gray lime bends of grayish-black fossil- stone chiefly fossiliferous in bearing micrite irregularly in ternally laminated micrite terbedded with the mudstone. in part dolomitized, in part Many fossil fragments and a silicified (forming grayish- few whole brachiopods are black chert), in thin to me pyritized. Unit looks very dium (rarely thicker than 1 much like lower part of unit ft) even and uneven continu 18 of eastern Nasorak section, ous beds. Regularly, and in with which it should probably many zones rhythmically, in- be correlated. 59ACr-123f is terbedded with thin- and very a fossil collection (table 2). thin bedded calcareous shale 59ACr-123 consists of chips and (or) shaly, silty clayey taken to represent lithology . 45 910±30+(?) micrite. Many of the cherty 7. (Lower part of Mlnu-a of pi. limestone beds pinch and swell 2A) Limestone, in part cherty, in a "nodular" aspect similar and subordinate shale. Gray to beds of unit 17 of eastern ish-black fossil-bearing (rare) Nasorak section; probably ap micrite, probably containing proximately equivalent to this some silt and clay and prob unit. Echinoderm and leafy ably locally partly dolomitized, bryozoan fragments were only commonly silicified to varying fossils recognized; no fossils extent and in many places ap collected. 59ACr-125 consists propriately called chert. Chief of chips taken to represent ly in moderately continuous lithology - _-_ _ . ._____ ._-. 160 825±30+(?) relatively even surfaced beds 5. (Upper part of Mlnu-a of pi. 1-10 in. thick; irregularly in 2A) . Limestone and shale. terbedded with thin shaly Medium-dark-gray clayey (?) partly calcareous mudstone silty (?) micrite (may include beds and partings, also gray some dismicrite), locally dolo ish black. Fragments of mitized, with discontinuous brachiopods only fossils recog lenticular thin internal lami nized. 59ACr-122f is fossil nation, in continuous relative collection (table 2) of meager ly even surfaced beds material. 59ACr-122 consists commonly 4-6 in. thick. Rhyth of chips taken to represent mically interbedded with shaly lithology. Unit should be calcareous mudstone that stratigraphic equivalent of makes up about 30 percent of unit 19 of eastern Nasorak the unit in beds commonly 1-2 section . . .___ __-_ 40 950±30+(?) in. thick. No fossils recog Total thickness of partial nized, but most of the sparse section of upper member_. 950±30 allochems are probably frag- Accordant depositional contact. mental fossil material. 59ACr- Cape Thompson Member of the 124 consists of chips taken to Nasorak Formation (Mine): represent lithology. Unit sim 8. (Mine of pi. 2A) Limestone. ilar to, and probably should Medium-light-gray to light- be correlated with, upper part olive-gray (weathering to pale of unit 18 of eastern Nasorak grayish orange) very coarse section -...... _...... _.. . 40 865+30+(?) grained crinoid-bryozoan bio- 6. (Middle part of Mlnu-a of pi. micrite (in places fine rudite 2A) Mudstone and minor rather than very coarse are- limestone. Grayish-black cal nite); commonly contains 60- careous mudstone containing 80 percent fragmental fossil sparse brachiopods and horn allochems. Parts of some beds 32 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Cape Thompson Member of the Na- Thickness (feet) sorak Formation Continued Unit Cumulative Thickness medium-gray partly dolomi (feet) Unit Cumulative tized (locally as much as 30 appear to have sparry calcite percent) coarse-grained cri- cement rather than matrix noidal biomicrite in beds as micrite, but these seem very much as 6 in. thick, chiefly local and subordinate. Com near top where zone also in monly a minor amount of dol cludes a few partings of gray omite (but locally up to near ish-black calcareous shale as ly 20 percent) replaces matrix it grades into overlying pre and forms rims on fossil struc dominantly mudstone zone. tures. Crops out like one mas Lower 45 ft chiefly medium- sive bed with bedding ex gray partly dolomitized (some pressed by internal "crinkly" common, but generally less laminae, some more continu than 25 percent) coarse ous than others, at 6-in. to 1- grained crinoid biomicrite in ft intervals. Both base and top uneven lenticular beds as appear to intertongue with ad much as 1% ft thick (most jacent shaly beds; intertongu- commonly about 6 in.) with ing clearly exposed only at even internal bedding laminae. base. Unit greatly resembles Minor interbedded dark-gray unit 20 of eastern Nasorak to grayish-black shaly micrite section, it's probable strati- or calcareous mudstone. Minor graphic equivalent. 59ACr- amounts of grayish-black 120f (table 2) is a chip of chert occurs as irregular highly fossiliferous, but frag- small nodules with indistinct mental, limestone. 59ACr-120 borders within limestone beds; consists of chips taken to varies in amount from 1 to 10 represent lithology (fig. 9) 225 l,175±30+(?) percent along individual beds. The biomicrite beds of en Accordant depositional contact. tire unit commonly contain Lower member of the Nasorak For 75-85 percent fragmental fos mation (Mini): sil allochems. Dolomitization 9. (Upper part of Mini of pi. 2A) chiefly restricted to the ma Limestone (in some places trix. In a few specimens partly dolomitized), chert, and intergranular material is en mudstone. tirely medium-crystalline dolo Upper 45 ft of unit is pre mite (although most of the dominantly grayish-black dolomite is aphanitic to very shaly silty (about 30 percent fine grained), and classifica fine quartz silt), clayey (?) tion of the original material partly dolomitized (at least as either micrite or spar can 10 percent locally), ostracode- only be assumed. Spiriferoid bearing micrite or calcareous brachiopods are prominent in mudstone; in beds from thin upper part of central cherty partings as much as 5 ft thick. zone. Other brachiopods, co Irregularly interbedded sub lonial and solitary corals, and ordinate amount (about 30 gastropods also found, along percent) of medium-dark-gray with the abundant echino- partly dolomitized (about 15 derm and bryozoan frag percent) coarse- to medium- ments. 59ACr-119f is a fossil grained crinoid biomicrite in collection (table 2). 59ACr- thin to medium lenticular dis 119 consists of chips taken continuous beds. to represent lithology .___.___- 125 l,300±30+(?) Middle 35 ft is chiefly 10. (Lowermost part of Mini of pi. (about 70 percent) grayish- 2A) Mudstone and inter black to black chert (silicified bedded limestone. Dark-gray laminated fossiliferous mi fossil-bearing calcareous mud- crite) in uneven, moderately stone, gradational to and regular beds, generally 4-6 in. interlaminated with clayey thick. About 15 percent of fine-grained biomicrite (con this cherty zone consists of taining as much as 30 percent MEASURED BEDROCK SECTIONS 33

Thickness Lower member of the Nasorak For (feet) mation Continued Unit Cumulative Thickness corals, are locally abundant. (feet) Unit Cumulative Olive-gray to light-olive-gray fragmental fossil material, in (weathering light brown) which small calcareous spines very fine and fine-grained are locally abundant), in beds quartz sandstone and dark- a few inches to about 4 ft gray to grayish-black sandy thick with thin discontinuous siltstone occur as interbedded internal lamination. Irregular paper-thin laminae to beds as . ly interbedded medium-gray much as 1 in. thick. Relative to medium-dark-gray partly proportions of sandstone, silt- dolomitized (as much as 20 stone, and mudstone vary percent locally) medium- to widely. Although sandstone coarse-grained crinoid bryozo- locally makes up as much as an biomicrite in relatively con 70 percent of the rocks, the tinuous beds, mostly 6-8 in. thin laminations give beds a thick. Looks like a transition shaly aspect. The olive-gray zone between the underlying sandstones are fairly well unnamed formation, in which sorted as to size and have a terrigenous clastic material dolomite(?) intergranular ce predominates, and Lisburne ment. Dark-gray muddy mi Group, in which allochemical crite and fossiliferous micrite and orthochemical carbonate occurs chiefly as thin lenticu predominates. Dominant fos lar discontinuous interbeds as sils are echinoderm and bryo- much as 3 in. thick. These zoan fragments, but the spine- limy beds commonly contain like structures are common in several percent of very fine a thin section of one specimen. grained quartz sand, and in No fossils were collected. places contain sufficient fossil 59ACr-118 consists of chips debris to be classed as biomi taken to represent lithology - 40 l,340±30+(?) crite. A few thin lenticular Total thickness of lower beds, commonly discontinuous member -___.______165 over several tens of feet, of Total exposed thickness of both fossiliferous and nonfos- Nasorak Formation ______l,340+(?) siliferous dense mudstone and Accordant depositional contact. sandy mudstone, are better Unnamed mudstone-sandstone-lime- indurated (possibly cemented stone unit. with iron oxide) and crop out as resistant ledges, as much as SEDIMENTARY ROCKS UNDIVIDED 1 ft thick, light reddish in Base of lower member of Nasorak color against the generally Formation. darker cliff. Fossils include Conformable, gradational contact. horn corals, brachiopods, and Unnamed mudstone-sandstone-lime- fragmental echinoderm and stone sequence (Ms): bryozoan debris. 59ACr-116 1. (Most of unit Ms of pi. 2A) and 59ACr-116f (table 2) rep Mudstone and sandstone, in resentative rock chips and a large part sufficiently fissile to fossil collection from lower be called shale or sandy shale, part of unit. 59ACr-117 and and minor limestone. Sand 59ACr-117f (table 2) repre stone most common in middle sentative rock chips and a third of unit, whereas shaly fossil collection from the mud stone predominates in up sandier middle part of unit . 400±20 400±20 per and lower thirds. Dark- 2. (Lowermost, contorted part of gray terrigenous mudstone unit Ms of pi. 2A) Mudstone and shaly mudstone occurs in and limestone with minor relatively continuous beds chert. Dark-gray calcareous from very thin partings to mudstone and muddy micrite 10 ft thick; commonly con that locally contains sufficient tains a few percent dissemi fossil debris to be classed as nated calcite silt or micrite; biomicrite. Rocks similar to fossils, chiefly small horn those of lower part of over- 34 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Unit Cumulative Unnamed mudstone-sandstone-lime- Thickness stone sequence Continued (feet) Thickness though beds are gently lentic (feet) Unit Cumulative ular and many coalesce or lying unit 1, but mudstone ap wedge out over several tens pears to be more calcareous of feet of exposure, the ratio and limestone is more abun- of length to thickness is so ant and contains some dark- great that most beds appear gray chert. The rocks occur in continuous, parallel, and of thin uneven irregularly inter- even thickness. Fossils rare, bedded lenticular strata, much generally sparsely dissemi contorted by drag folding and nated fragments, but one car minor faulting related to un bonate mudstone bed yielded derlying Ibrulikorak thrust several gastropods and brach- fault. The only fossils recog iopods. 59Acr-87f is fossil nized were a few crinoid collection (table 2). 59ACr-87 columnals. 59ACr-115 con consists of chips taken to rep sists of chips taken to rep resent lithology -_ _ __ 125 155+ resent lithology. Thickness of 3. (Lower part of Mlt of pi. 2B) unit estimated. Base not ex Limestone (partly dolomitized posed ______20(?) 420 ±20 calcite mudstone) containing Total thickness of exposed variable amounts of nodular mudstone-sandstone-lime- chert, interbedded chert beds. stone unit ______420±20 Dark-gray to medium-gray in ternally laminated partly dol Ibrulikorak thrust fault, underlain omitized calcite mudstone by younger carbonate rocks of Lis- (micrite and calcite silt), burne Group. locally containing sparsely MISSISSIPPIAN ROCKS EAST SECTIONS disseminated fossil fragments, in beds from 0.01 ft (locally [Sections measured at sea-cliff exposures between Amaktusak and Imikrak Creeks, by R. H. Campbell and D. R. Currey, July and August 1959] having shaly fissility) to 2 LISBURNE GROUP ft thick, make up 60-70 per cent of unit. Black to grayish- TUPIK FORMATION black chert occurs as interbeds Siksikpuk Formation: High-angle as much as 1 ft thick and as fault contact at cliffs, but config small irregular nodules and uration farther inland indicates continuous even-to-uneven- accordant (conformable?) contact. surfaced lenses within lime stone beds. Chert irregularly Tupik Formation (Mlt): distributed; appears to be 1. (Uppermost part of Mlt of pi. most abundant (locally as 2B) Interval cut out at cliffs much as 90 percent) in middle by high-angle fault. (Basal 30 third of unit. Beds generally ft is exposed in inaccessible continuous, parallel, and even upper part of sea cliffs.) surfaced, but some shaly part Farther inland it is covered ings in upper part change and only frost heaved rubble character along the dip .into is found. Generally similar better indurated beds. The to underlying unit exposed at interbedding of thick and thin the cliffs, but more thinly beds, and of beds of different bedded -______80-f (100?) 30+ composition, is regular even 2. (Upper part of Mlt of pi. 2B) appearing rhythmic in most Chert and interbedded car of unit; some zones of irregu bonate mudstone. Grayish- lar interbedding. Sample black chert in beds 0.1 ft to 2 59ACr-77 consists of chips ft thick makes up about 50 representing the various li- percent of unit. Dark-gray to thologies - _- _ __- 175 330+ medium-dark-gray internally Base of unit not exposed. laminated "carbonate mud- Thickness of missing part of stone" of variable composition Tupik Formation, based on in beds from less than 0.1 ft to apparently normal contact re 3 ft thick irregularly inter- lations with the underlying bedded with the chert. Al- Kogruk(?) Formation farther MEASURED BEDROCK SECTIONS 35

Thickness Tupik Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative 3. (Mlk-g of pi. 2B) Dolomite, inland, is on the order of 70- dolomitic limestone, and chert. 100 ft ______(100?) Chiefly medium-gray to medi Total thickness of Tupik um-dark-gray fine to medium- Formation ...... 330+ (200?) crystalline biogenic dolomite (dolomitized biomicrite and High-angle fault contact. fossiliferous micrite); about Kogruk(?) Formation. 20 percent medium-light-gray to dark-gray chert in small KOGRUK(?) FORMATION nodules, irregular patches, and Tupik Formation: High-angle fault some possible intraclasts; and, contact at cliff exposures, but con locally, about 20 percent light- tact configuration farther inland olive-gray dolomitic limestone indicates accordant (conform (partly dolomitized, 50 per able?) contact within a few tens to cent, fossiliferous micrite). In a few hundreds of feet strati- part a dolomitized coarse in- graphically above highest Kogruk tramicrudite (or locally de (?) beds exposed in cliffs. rived sedimentary breccia with Kogruk(?) Formation (Mlk): carbonate mudstone matrix). 1. (Uppermost part of Mlk-h of pi. Beds generally about 1 ft 2B) Topmost beds not exposed thick, but range in thickness at beach level, being cut out by from 1 in. to 2 ft. Irregular fault dontact with Tupik For bedding, uneven bedding sur mation1 ; lower part visible in faces, and continuous but in inaccessible parts of sea cliff. distinct bedding surfaces Thickness of missing part of result in a massively outcrop Kogruk(?) Formation, based ping aspect. Intraclasts gen on apparently normal contact erally sparsely disseminated, relations with the Tupik but locally abundant; chiefly farther inland, on the order of irregularly fragments of car 100-300 ft. The rocks are bonate mudstone, some show probably much like those of ing internal bedding lamina underlying unit 2 ______.... 100+ 100+ tion, and angular pieces of 2. (Lower part of Mlk-h of pi. 2B) chert that appear to be de- Dolomite and minor dolomitic trital (though there is also limestone with variable abundant postdepositional amounts of chert. Chiefly chert). Although some clasts light-olive-gray to light-gray are as much as 5 cm across, dolomite and dolomitic lime most are only a few milli stone in even continuous beds. meters in diameter. Ratio of Unit mostly regularly strati dolomite to calcite ranges fied 1- to 2-f t beds; some beds from about 19:1 to about 1:1. as much as 15 ft thick in lower Recognizable ghosts of fossils part, and a few as much as include horn corals, crinoid 6 ft thick in upper part. Medi um-gray chert common both columnals, and Bryozoa. as continuous lenticular bands 59ACr-74f is a fossil collec 6-8 in. thick and as small ir- tion (table 2). 59ACr-74 and regulafc nodules and lenticular 59ACr-75 are chips taken noduleS as much as a few to represent lithologic varia inches in diameter. No fossils tions. Some tectonic breccia- or ghosts of fossils found. tion of unit tends to obscure Dolomite fine to medium crys the nature of sedimentary talline; commonly shows thin breccia locally, chiefly along internal lamination. Most intensely jointed zones that probably a dolomitized mi- show little observable dis crite, or possibly a dolomitized very fine grained calcarenite. placement. Base of unit not Sample 59ACr-76 consists of exposed; contact with under chips taken to represent lith- lying unit is a high-angle ology .-_-_ .-___ .. ._ ___.. 370 470+ fault ___.______-___. 270+ 740+ 36 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Thickness Kogruk(?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative range. Matrix commonly High-angle fault, unknown thickness lighter in color than the dolo missing. mite clasts, generally medium 4. (Mlk-f of pi. 2B) Dolomite with light gray to light gray; chief minor chert. Massively out ly fine- to medium-crystalline cropping medium-gray to dolomite with variable but olive-gray fine- to medium- minor amounts of relict(?) crystalline biogenic dolomite; calcite micrite and microspar dark-gray to light-gray chert, (?). In a few places, coarsely in nodules generally less than crystalline dolomite appears 1 ft in diameter, locally as to occur as an intergranular much as 10 percent of rock. cement; both clasts and ma Bedding characteristics and trix cut by veinlets filled with outcrop form much the same calcite and dolomite. Bedding as unit 3, but contains less characteristics of the massive chert; contains no recogniz ly outcropping unit could not able intraclasts. Breccia be distinguished. No fossils abundant in one zone on east were seen. 59ACr-71 consists side of unit, at its fault con of chips taken to represent tact with unit 5, where it may lithology. Unit bounded on all be tectonic. Ghosts of fos both sides by high-angle sils include crinoid columnals, faults; thickness shown is Bryozoa, horn corals, and minimum. As lithology is not brachiopod fragments. 59ACr- clearly repeated elsewhere in 73f (table 2) is fossil collec section, unit is believed to lie tion of the meager, poorly stratigraphically between preserved fauna. 59AO-73 units 4 and 6, probably with and 59AO-72 are chips taken not more than a few hundred of characteristic lithologic feet of beds missing ______._ - 145+ 985+ types. Unit separated from High-angle fault, unknown thickness adjacent rocks on both sides missing. by high-angle faults. Repre 6. (Upper part of Mlk-d of pi. 2B) sents a stratigraphic thickness Rocks in inaccessible part of of at least 100 ft, and as the cliff, not exposed at beach accessible parts not clearly level. Looks very similar to, repeated elsewhere in section, and probably gradational it is believed to lie strati- with, unit 7 below. From graphically between units 3 beach level, only observable and 5, probably with not more difference from unit 7 is that than a few hundred feet of the bedding surfaces of this beds missing . _ .. . ._.._ 100+ 840+ unit look more even. Top of High-angle fault, unknown thickness unit not exposed; thickness missing (probably not more than shown is therefore a mini a few hundred feet). mum. 140+ 1,125+ 5. (Mlk-e of pi. 2B) Carbonate- 7. (Lower part of Mlk-d of pi. 2B) chert breccia, probably sedi Rhythmically interbedded dol- mentary, but because unit is omitic limestone and silty bounded by high-angle faults, calcite mudstone, with about may be largely or completely 20 percent chert nodules. Me- tectonic. About 30 percent me dium-dark-gray dolomitic dium gray to medium-dark- limestone dolomitized lami gray chert aphanitic micro- nated microsparite or calcite granular quartz containing mudstone in beds averaging abundant disseminated medi 0.5 ft thick (range from 0.1 um-crystalline euhedral and to 1.0 ft) rhythmically inter- subhedral dolomite crystals; bedded with shaly partings occurs as 2-15 cm angular (generally less than 0.03 ft fragments. Medium-gray co thick) consisting chiefly of arsely crystalline to medium- medium-dark-gray silty mi crystalline dolomite occurs as crosparite. (May contain as subrounded clasts in same size much as 18 percent fine MEASURED BEDROCK SECTIONS 37

Thicknesi Kogruk(?) Formation Continued (feet) Thicknest Unit Cumulative (feet) Unit Cumulative of unit contains about 20 per quartz silt.) No fossils seen. cent dark-gray to light-gray 59AO-70 consists of chips chert in thin lenticular bands taken to represent lithology. along bedding and in irregular Base of unit not exposed, and small nodules. Upper part of contact with underlying unit unit contains a few percent is a high-angle fault. As this more chert, partly as light- lithology is not clearly re to medium-gray lenticular peated elsewhere in section, nodules as much as 2% ft unit is believed to lie strati- thick and 6 ft long, as well as graphically between units 6 3 distinctive zones, each about and 8, probably with not more 10 ft thick, of light-gray and than a few hundred feet of grayish-orange pink chert in beds missing ...... _.. __....._ 150+ 1,275 + very thin (% in. and thinner) High-angle fault, unknown thickness laminae with minor amounts missing. of interlaminated very finely 8. (Upper one-fourth of Mlk-c of crystalline dolomite. One pi. 2B) Dolomite with very prominent zone of intraforma- minor chert. White to yellow tional breccia occurs about 60 ish-gray medium-crystalline ft above base of unit (fig. 10.) dolomite with 5-10 percent Fossils are very sparse and relict medium-crystalline cal- consist of dolomitized frag- cite spar in irregular patches. mental material. 59ACr-68f Patches of finely crystalline is fossil collection (table 2). dolomite from fine-sand to 59ACr-68 and 59ACr-67 are fine-pebble size look like al- chips taken to represent lochem ghosts of unidentified lithology - .._ . ._. _ 330 1,745+ origin. Unit crops out mas 10. (Uppermost part of Mlk-b of pi. sively and looks like a single 2B) Dolomite with very minor thick bed, but some discon chert. Chiefly yellowish-gray tinuous lamination and a few but partly light-olive-gray and zones of small (less than 1 medium-gray medium-crystal in.) medium-gray chert nod line dolomite, locally showing ules express bedding. Chert some ghostly internal fine makes up only about 1 percent lamination probably chiefly of unit. No fossils seen. dolomitized micrite or very 59ACr-69 consists of chips fine grained calcarenite. Very taken to represent lithologic thick bedded with discontinu types. Top not exposed ...... 140+ 1,415 + ous faint bedding surfaces and 9. (Lower three-fourths of Mlk-c a massively outcropping as of pi. 2B) Dolomite with pect. Light- and dark-gray minor but distinctive lami chert in thin discontinuous nated chert. Light-gray to zones and bedding-oriented very light gray, medium, thin lenticular nodules make coarse, and finely crystalline up 1-5 percent of unit. No dolomite commonly showing fossils found. 59ACr-66 con ghostly internal cross-lamina sists of chips taken to repre tion probably chiefly dolo- sent lithology .. .._. ...-...__ 57 1,802 + mitized calcarenite, but 11. (In upper part of Mlk-b of pi. includes some clearly recogniz 2B) Dolomite and chert. able dolomitized fossiliferous Light-olive-gray and yellow micrite generally with less ish-gray finely crystalline than 5 percent relict(?) cal- dolomite probably chiefly cite; locally one 3-ft zone con dolomitized micrite or very tains as much as 50(?) per fine grained allomicrite with cent calcite. Irregularly relict(?) intergranular calcite bedded massive, thick, and a micrite and microspar rang few thin beds, all discontinu ing from 3 to 20 percent. Very ous over several tens of feet, fine internal lamination (lo giving unit a massive cliff- cally cross laminated) is ex forming aspect. Lower part pressed by alternating color 38 AREAL GEOLOGY, VICINITY OP CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Thickness Kogruk (?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative of crinoid columnals. 59ACr- laminae. Megascopic bedding 64 consists of chips taken to is indistinct, but distribution represent lithology ._-_._ 28 1,890+ of chert zones gives basal part 13. (In middle part of Mlk-b of pi. of unit a thin-bedded aspect 2B) Dolomite with minor with a gradation upward to chert. Light-olive-gray fine- ward more thickly bedded to medium-crystalline biogenic aspect resembling unit 10. dolomite (dolomitized biomi Dark-gray chert occurs in crite and fossiliferous micrite thin (averaging about 1 in. containing from less than 1 thick) relatively continuous percent to as much as 25 per uneven surfaced zones. In cent ghosts of fossils) with lower part of unit, chert zones generally less than 5 percent are regularly interlayered relict(?) calcite micrite and with the dolomite at intervals intergranular spar. Dark- of about 4 in. In upper half gray to grayish-black lenticu of unit, chert zones are slight lar nodules 1-3 in. thick and ly thicker but less continuous, from less than 6 in. to about and spacing between them 2 ft long abundant (as much grades upward to 1 ft. Top as 30 percent of the rocks) most beds contain only a few in some stratigraphic zones, scattered chert nodules. No where they are oriented along fossils found in unit. 59ACr- the bedding direction. Light- 65 consists of chips taken to gray to very light gray irregu represent lithology ____.___...... 60 1,862+ lar small (about 2 in. in 12. (In upper part of Mlk-b of pi. diameter) chert nodules ran 2B) Dolomite. Light-olive- domly distributed. Total chert gray to light-gray finely crys content of unit is estimated talline dolomite including to be 5-10 percent. Unit looks clearly recognizable dolomi- like one massive bed, with tized biomicrite, but chiefly bedding expressed by discon probably dolomitized lami tinuous internal laminae nated micrite with minor chiefly oriented bryozoan leafy (but locally as much as 20 fragments and discontinuous percent) relict(?) micrite and bedding plane partings spaced local intergranular calcite from 6 in. to 3 ft apart. spar; and dark-gray finely Recognizable fossils include crystalline laminated dolomite Bryozoa, crinoid columnals, probably a dolomitized mi horn coral, and an indistinct crite containing as much as form of colonial coral(?). All 5 percent carbonaceous ma- fossils consist of dolomitized terial(?) interstitial to sub- ghosts; none appeared suffi hedral dolomite. Light-colored ciently well preserved to war rocks predominate in the lower rant collection. 59ACr-63 con part of the unit in beds from sists of chips taken to repre 1 in. to 3 ft thick. The thick sent lithology -______155 2,045+ beds show indistinct internal 14. (In middle part of Mlk-b of pi. lamination; the thin beds are 2B) Dolomite. Medium-dark- internally thinly laminated gray finely crystalline to me and locally contain abundant dium-crystalline biogenic small (about 1 in.) grayish- dolomite dolomitized fossil- black chert nodules. Dark- bearing micrite and biomicrite colored rocks predominate in containing as much as 50 per upper part of unit in beds as cent ghosts of fragmental fos much as 1% ft thick, con sils in 6-in. to 1-ft-thick taining about 1 percent small irregularly bedded discontinu dark-gray and grayish-black ous unevenly surfaced beds, chert nodules. Bedding is gen predominates in several zones erally lenticular and continu from 5-20 ft thick; separated ous. Recognizable fossils are by a few continuous beds exclusively dolomitized ghosts 2-4 ft thick of light-gray MEASURED BEDROCK SECTIONS 39

Thickness Kogruk (?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative gray finely crystalline to me medium-crystalline to coarse dium-crystalline laminated ly crystalline biogenic(?) dolomite no clear cut ghosts dolomite dolomitized allomi- remain, but textures expressed crite containing as much as 30 by patches and laminae of percent allochem (fossil?) coarser crystalline dolomite ghosts. Unit is relatively in finer crystalline matrix and chert free except near top, interlaminae suggest the rocks where some light-gray dolo formed by dolomitization of mite beds contain minor laminated calcite mudstone or amounts (less than 1 percent) fine calcarenite with distinc of dark-gray to grayish-black tive lenticular color mottling chert in thin lenticular nod that apparently represents ules. Recognizable fossil ma variations in abundance of terial includes Bryozoa, cri- impurities (carbon?). The noid columnals and other lighter colored areas possibly echinoderm fragments, horn represent better "washed" corals, and brachiopod(?) current winnowed calcarenite shell fragments. 59ACr-62f is in which calcite spar cement a fossil collection (table 2). was deposited instead of in 59ACr-62 consists of chips terstitial micrite. (Mottling taken to represent lithology_... 82 2,127+ illustrated by photograph, fig. 15. (In middle part of Mlk-b of pi. 12). Unit has massively out 2B) Dolomite and subordinate cropping aspect and is very chert. Medium-light-gray to thick bedded, with individual medium-gray medium-crystal beds as much as 50 ft thick. line to finely crystalline Bedding expressed by oriented biogenic(?) dolomite dolomi mottled zones, internal lami tized coarse biomicrite or bi- nation, and a few irregularly osparite, containing about 60 spaced indistinct discontinu percent ghosts of fragmental ous bedding-plane partings. fossils in indistinct discon Light-medium-gray to light- tinuous beds from 5 in. to 3 gray chert occurs as thin ft thick. Dark-gray chert and lenticular nodules and nodular minor amounts of light-gray bands oriented along bedding chert make up about 15 per direction. A few zones may cent of unit as irregular nod contain as much as 20 percent ules arranged in relatively chert, but total with respect continuous zones within dolo to entire unit is less than 10 mite beds parallel to the bed percent. No fossils recognized. ding. Individual nodules are 59ACr-60 and 59ACr-60a are as much as 1 ft thick but chips taken to represent lith average about 2 in. Dolomi ology ______100 2,252+ tized fossil debris includes 17. (In lower part of Mlk-b of pi. chiefly crinoid columnals and 2B) Dolomite with minor other echinoderm fragments chert. Medium-gray to dark- and subordinate Bryozoa. gray medium-crystalline bio None appeared well-enough genic dolomite dolomitized preserved to warrant collec medium-grained biomicrite tion. 59ACr-61 consists of containing about 20 percent chips taken to represent ghosts of fragmental fossils lithology . -...-...... - 25 2,152 + of which leafy Bryozoa, ori Unit 16 appears gradational ented along bedding direction, with unit 15 through a transi predominate with less than tion zone that is about 16 ft 5 percent relict(?) calcite, thick. These beds are included chiefly as sparry centers of in the total thickness given for almost wholly dolomitized unit 16 below. crinoid columnals(?). Dark- 16. (In lower part of Mlk-b of pi. gray to grayish-black chert 2B) Dolomite. Light-gray, silicified biomicrite or fossili- very light gray, and medium- f erous micrite in which hollow 40 MEASURED BEDROCK SECTION

Thickness Kogruk (?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative tures that seem to be some spines (echinoderm or brachi- form of colonial coral, but opod, most likely) predomi none of the material was well- nate occurs as a few rare enough preserved to warrant irregular nodules, generally collection. 59ACr-58 consists about 1 in. in diameter. The of chips taken to represent unit is thin-bedded, regularly lithology ______-_ 110 2,409+ bedded; beds are continuous 19. (Uppermost part of Mlk-a of pi. but have minor undulating un- 2B) Dolomite. Light-olive- evenness of bedding surfaces. gray to medium-gray very Fossils include Bryozoa, cri- finely crystalline to finely noid columnals and unidenti crystalline biogenic dolomite fied echinoderm debris, horn dolomitized very fine coral, and brachiopods. grained to coarse-grained 59ACr-59f is fossil collection biomicrite, fine biomicrudite, (table 2). 59ACr-59 consists and fossiliferous micrite, con of chips taken to represent taining from 7-60 percent lithology ...... _. ...-. 47 2,299 + ghosts of fragmental fossils 18. (Lowermost part of Mlk-b of generally less than 3 percent pi. 25) Dolomite with minor relict (?) calcite micrite and chert. Medium-light-gray to intergranular spar. Medium- medium-gray, and dark-gray light-gray chert makes up a medium-crystalline dolomite, few percent of unit, chiefly in in large part biogenic most upper part, mostly as thin is probably dolomitized fine- (as much as 10 in.) irregular to coarse-grained biomicrite ly lenticular nodules in dis containing from 3 to 30 per continuous bedding-oriented cent fragmental ghosts of fos zones in and along bedding sils generally with less than surfaces. Beds range in thick 3 percent relict (?) calcite, ness from less than 1 in, to chiefly as intergranular as much as 15 ft; bedding sur patches of spar. Light-gray faces are irregularly spaced to dark-gray chert occurs (through close spacing is chiefly as small irregular nod rare), relatively but not per ules and thin discontinuous fectly even, and generally zones of nodules within dolo continuous for at least 100 ft mite beds. The light-gray to (though overall aspect is gent medium-gray dolomite that ly lenticular). Cross-joint makes up most of unit is thick spacing of about the same to very thick-bedded (some range as the bedding thickness beds as much as 20 ft thick) combines to give unit a blocky- with irregularly spaced dis surfaced massive-outcropping continuous bedding surfaces; aspect. Recognizable ghosts of has a massively outcropping fossils include only crinoid aspect. The dark-gray dolo columnals and leafy bryozoan mite is all in one zone, 10-15 fragments, none well-enough ft thick, of thinly bedded preserved to warrant collec strata near middle of unit. tion. 59ACr-57 consists of Most beds show some internal chips taken to represent lith lamination at irregularly ology . - . _.__.______-. __ 255 2,664+ spaced intervals, most notice 20. (In upper part of Mlk-a of pi. able and closely spaced in thin- 2B) Dolomite with subordi bedded central zone. Chert nate chert. Medium-light-gray makes up about 10 percent of to light-gray, and light-olive- upper thick-bedded zone, gray finely crystalline to me about 5 percent of lower dium-crystalline dolomite, in thick-bedded zone, and is very part biogenic dolomitized bi rare in central thin-bedded omicrite and laminated mi zone. Recognizable ghosts of crite with as much as 20 per fossils include a few crinoid cent ghosts of fragmental columnals and, rarely, strue- fossils generally containing MEASURED BEDROCK SECTIONS 41

Thickness Kogruk (?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative 22. (In middle part of Mlk-a of pi. less than 5 percent relict(?) 2B) Dolomite with subordi calcite micrite and intergranu- nate chert. Chiefly light-olive- lar spar. Dark-gray and me gray to light-gray, but some dium-gray chert occurs as medium-dark-gray, finely crys lenticular nodules within dolo talline biogenic dolomite mite beds and as thin long (as dolomitized fossil-bearing mi much as 20 ft) discontinuous crite, generally containing less zones along bedding planes. than 10 percent fragmental Beds are thin, mostly about 4 fossil material generally in. thick, but ranging from 2 with less than 1 percent in. to IVs ft. Bedding surfaces relict(?) calcite micrite. Me are slightly uneven, but ap dium-dark-gray to dark-gray pear relatively continuous. chert makes up about 20 per Recognizable ghosts of fossils cent of unit, chiefly as small include crinoid columnals, irregularly lenticular nodules leafy Bryozoa, colonial corals, within the dolomite beds. Beds and brachiopod fragments. are thin (commonly 1-6 in. 59ACr-56f is fossil collection thick) and have relatively (table 2); 59ACr-56 consists continuous but undulating of chips taken to represent bedding surfaces, so that beds lithology -...... _..._ _ . 120 2,784 + pinch and swell irregularly 21. (In middle part of Mlk-a of pi. along bedding; compensated 2B) Dolomitic limestone and by alternating pinches and silty fossiliferous carbonate swells in adjacent beds. Ghosts mudstone. Medium-gray part of fossils are chiefly leafy ly dolomitized (as much as 25 Bryozoa, but brachiopod frag percent locally) partly silici- ments are locally abundant. fied locally as much as 10 No fossil material collected. percent patchy aphanitic to 59ACr-54 consists of chips finely crystalline microgranu- taken to represent lithology- 25 2,895+ lar chert) fine- to very coarse 23. (In middle part of Mlk-a of pi. grained crinoid-bryozoan bio- 25) Dolomite. Light-gray to micrite, generally contains 30- very light gray medium-crys 85 percent fragmental fossil talline partly biogenic dolo material and, though micrite mite sparse recognizable matrix predominates, as much ghosts of crinoid columnals as 10 percent intergranular and ghostly internal color sparry calcite. Chiefly irregu lamination suggest original larly bedded in thick and thin rock was a fossiliferous cal- relatively continuous even carenite. A minor amount of beds. With interbedded thin- medium-gray chert occurs as bedded to thin-laminated dark- small nodules. Bedding ir gray silty (from less than 1 regular; thickness of beds percent to as much as 25 per ranges from 6 in. to 12 ft, cent quartz silt) fine-grained most commonly 2-4% ft. biomicrosparite (with 7-30 Crinoid columnals are the percent fragmental fossil ma only fossils recognized. terial), and medium-light- 59ACr-53 consists of chips gray finely crystalline biogenic taken to represent lithology. dolomite (probably the dolo Unit appears very similar to mitized equivalent of the silty the light-colored dolomite of underlying unit 24, but more biomicrosparite). Fossils in thickly bedded (massively out clude a blastoid and locally cropping) ; contains less me abundant brachiopods, as well dium-gray chert and no gray as bryozoan and echinoderm ish-black chert. The two units debris. 59ACr-55f is fossil appear gradational ... _ §8 2,978 + collection (table 2); 59ACr-55 24. (In middle part of Mlk-a of pi. consists of chips taken to %B) Dolomite with minor represent lithology ..... _. .,._ 86 2,870 + chert. Chiefly light-gray to 42 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Kogruk (?) Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative dium-crystalline limestone in light-olive-gray coarsely crys beds 5 in. to 2 ft thick with, talline dolomite faint lami very locally, about 1 percent nation suggests a dolomitized grayish-black chert as discon calcarenite in continuous tinuous lenticular zones very even beds most commonly 8 locally as much as 2 ft thick . 56 3,119+ in. to 1% ft thick. Irregularly 26. (In lower part of Mlk-a of pi. interbedded with medium-gray 2B) Dolomite, cherty dolo medium-crystalline (?) lami mite, limestone, and chert. nated dolomite dolomitized Light-gray to medium-light- micrite (most laminae are gray partly cherty largely bi- feathery current laminations) ogenic very fine to coarsely in discontinuous lenticular crystalline dolomite except beds from a few inches to 1 for some uniformly coarsely ft thick. Grayish-black chert crystalline dolomite in which and medium-gray chert occurs original textures have been in small (less than 1 ft) ir completely masked, rock ap regular nodules in a few long pears to be a dolomitized (as much as 30 ft) thin (com (mostly 80-95 percent dolo monly about 6 in. thick) lentic mite) silicified (in many ular zones. Chert totals only places with 10-20 percent about 5 percent of the rocks very finely crystalline micro- of unit. Sparse ghosts of fos granular quartz, as a porous sils include horn coral and spongy intergrowth with the brachiopod fragments, as well carbonate) very fine grained as more common bryozoan and to coarse-grained biogenic echinoderm debris. 59ACr-52f calcarenite, in part with a (table 2) is collection of micrite matrix, and in part sparse ghosts of fossils; with intergranular calcite 59ACr-52 consists of chips spar cement. Medium-gray to taken to represent lithology 85 3,063 + medium-dark-gray limestone 25. (In middle part of Mlk-a of pi. very fine to very coarse 2B) The following descrip grained crinoid-bryozoan bi- tion is from field notes,1 osparite, in places as much as probable corrections in par 10 percent dolomitized; gen entheses: Limestone (prob erally contains more than 70 ably dolomitic), dolomitic percent fragmental fossil ma limestone (very possibly a terial. Light-gray chert nearly pure dolomite with a (spongy intergrowth in the few percent relict calcite or dolomite) occurs in irregular late calcite veinlets that may patches of widely ranging not be obvious in hand speci size. Grayish-black chert oc men), and chert. A 5-ft-thick curs as irregular discontinu bed of light-brown coarsely ous zones as much as 6 in. crystalline limestone forms thick, commonly oriented base of unit. It is overlain by along bedding, but locally a zone about 20 ft thick of crosscutting bedding at low thin laminated medium-gray angles. Total chert content of dolomitic limestone in beds a unit is probably 5-10 percent. few inches to 3 ft thick, with The dolomite is chiefly in beds about 10 percent grayish- ranging in thickness from 1 black chert in discontinuous in. to 7 ft, but general aspect irregularly bordered zones dominated by beds 8-4 ft locally as much as 1 ft thick. thick. Bedding surfaces gen The topmost zone (about 20 erally appear even and con- ft thick) is medium-gray me- tinuous. Internal lamination

i No, representative chips from this unit were available; therefore, the believed upon cursory field examination; in addition, the rocks designated as flelcj designations could not be checked by staining for calcite or microscopic coarsely crystalline in the field commonly owe that crystallinity to the pres te^tural examination in the laboratory. On the basis of eompari9ons be ence of coarse-grained echinoderm debris, which, of course, consists largely tween field and laboratory designations for rocks of other units, the rocks of plates, each a single crystal. are probably a great deal more dolomitic and more finely crystalline than was MEASURED BEDROCK SECTIONS 43

Thickness Kogruk (?) Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative sists of chips taken to repre not commonly well expressed, sent lithology _ _ 47 3,541+ except in a few beds of dolo- 28. (In lower part of Mlk-a of pi. mitized Bryozoa-bearing mi- 25) Dolomite and dolomitic crite near top of unit. In gen limestone, with chert. Medium- eral, lower part of unit has a gray to medium-dark-gray more massively outcropping fine- to medium-crystalline dol aspect and is lighter in color; omite and dolomitic limestone upward gradation to some dolomitized (chiefly from what darker colored, more 20-65 percent dolomite) very ledgy aspect, most noticeable fine to very coarse grained when viewed from a distance. biosparite and biomicrosparite Fossils are rare, but those (commonly with about 60 per found include horn coral and cent fragmental fossil relicts colonial coral as well as the and ghosts). Pale-yellowish- ubiquitous fragmental echino- brown finely crystalline lami derm and bryozoan debris. nated dolomite dolomitized 59ACr-29f is a fossil collec (to more than 95 percent) cur- tion (table 2). 59AO-29 and rent(?) laminated micrite or 59ACr-28f are chips taken to very fine calcarenite. Car represent lithology _____...____._._ 375 3,494 + bonate rocks locally include a 27. (In lower part of Mlk-a of pi. few percent spongy chert that 2B) Dolomitic limestone, dolo is discernible only in micro mite, and chert. Medium-gray scopic examination. The car to medium-dark-gray partly bonate beds range in thickness dolomitized (commonly 15-50 from less than 1 in. to about percent dolomite) coarse 5 in., averaging about 4 in., grained crinoid biomicro- and are separated by bedding sparite, chiefly with 25-50 oriented zones of dark-gray to percent fragmental fossil grayish-black chert averaging material, and clayey (?) mi- about 3 in. thick but ranging crosparite. Subordinate me from 1 in. to 5 in. in remark dium-light-gray very finely ably continuous strata with crystalline biogenic dolomite only minor pinching and dolomitized clayey (?) coarse swelling. Chert makes up grained crinoid biomicro- about 30 percent of unit. A sparite and fossiliferous few dolomite beds near top of micrite, with 1-40 percent unit are thicker, as much as ghosts and calcite relicts of 2 ft thick, and contain less fragmental fossils, and com chert. The only recognized monly 60-80 percent dolomite. fossil material was crinoid col- Grayish-black chert occurs umnals and a few indistinct chiefly as relatively continu spiny or spicular structures in ous nodular zones 1-6 in. thick some of the chert. 59ACr-26 as well as small lenticular consists of chips taken to nodules, oriented along the represent lithology .... _ 83 3,624+ bedding. Chert makes up 29. (Lowermost part of Mlk-a of pi. about 10 percent of the rocks 2B) Dolomite, chert, and sub of the unit. The limestone is ordinate limestone. Medium- in beds 1 in. to 2V2 ft thick light-gray medium-crystalline and generally shows some in dolomite probably a dolo ternal lamination. Bedding mitized faintly laminated fos surfaces generally appear sil-bearing micrite, generally even and continuous. Fossil containing less than 5 percent material includes horn corals allochem ghosts interbedded particularly abundant near with medium-dark-gray but top of unit as well as otherwise similar medium- echinoderm and bryozoan crystalline dolomite and light- debris. 59ACr-27f (table 2) gray very coarse-grained is fossil collection from upper crinoid biosparite (which may 10 ft of unit. 59ACr-27 con- be partly a biomicrosparite). 44 AREAL GEOLOGY, VICINITY OP CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Kogruk (?) Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative from 5-15 percent of most of The dolomite is in thick beds, the limy beds, chiefly as ir generally 2%-7 ft thick, con regular nodules of widely taining abundant (locally as ranging size (as much as 1% much as 60 percent) thin ft in diameter, but commonly (about 2 in. thick) continuous smaller) in the limestone, with zones of grayish-black chert. which they commonly have in Grayish-black and light-medi distinct gradational borders. um-gray chert also occurs as The limestone beds range in irregular nodules. Recogniz thickness from less than 1 in. able fossil material is chiefly to about 2 ft; but thick beds crinoid columnals as relict are rare and found only in calcite in chert and as ghosts upper part of unit. More in dolomite and ghosts of generally, a gradational in Bryozoa along lamination in crease in thickness upward dolomite. 59AO-25 consists from an average of about 6 in. of chips taken to represent in the lower part to about 1 lithology ______46 3,670+ ft in upper part. The inter- Total thickness of Ko- bedded carbonate mudstone gruk(?) Formation .---..3,670+(500?) forms partings as much as 3 in. in thickness; gradual Nasorak Formation, conformable decrease in thickness and contact (actually, the basal four abundance of these partings units of the Kogruk(?) Formation from lower part of unit to together with the top unit of the top. Fossils include colonial underlying Nasorak Formation, corals and brachiopods as well appear to be a transition zone rep as echinoderm and bryozoan resenting the gradual, alternating debris. Colonial coral heads change of depositional environ locally stand out as white ments represented by the two lenses as much as 1 ft thick formations). and \Vz ft long in the lime NASORAK FORMATION stone beds (fig. 7). 59ACr-22f, 59ACf-23f, and 59ACr-24f Kogruk (?) Formation. (table 2) are fossil collections. Conformable contact. 59Acr-22, 59Acr-23, and a Upper member of the Nasorak For split from 59ACr-24f consist mation (Mlnu): of chips taken to represent 1. (Mlnu-h of pi. 25) Dolomite, lithology -______-_.. . _ .._ __ 586 586 dolomitic limestone, calcareous 2. Covered interval. Rocks prob shale, and chert. Dark-gray ably similar to unit 1 but may finely crystalline biogenic dolo be gradational to rock types mite and dolomitic limestone of unit 3 below. Possibility of dolomitized and partly dolomi- faulting cannot be completely tized crinoid-bryozoan coarse- ruled out, but no major dis to very coarse grained biomi- placement could be found crite, containing from 20-60 along probable projection of percent fragmental fossil ma the zone. Stratigraphic thick terial, and with replacement ness represented . .__._ 85 671 dolomite ranging from 20 to 3. (Upper two-thirds of Mlnu-g of 80 percent; rhythmically in- pi. 2£?) Limestone, partly terbedded with dark-gray thin dolomitic, and calcareous laminated carbonate mudstone shale, with subordinate chert, or calcareous shale partly rhythmically interbedded bi- dolomitized micrite and fos- omicrite and carbonate mud- siliferous micrite. Several beds of medium-gray partly stone or calcareous shale. dolomitized bryozoan-crinoid Medium-gray (weathers to coarse biosparite interbedded light gray and pale grayish at widely spaced irregular in orange) coarse-grained cri tervals in lower half of unit. noid-bryozoan biomicrite lo Grayish-black chert forms cally with irregular small MEASURED BEDROCK SECTIONS 45

Upper member of the Nasorak Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative 4. (Upper part of lower one-third patches and laminae where of Mlnu-g of pi. 2B) Lime intergranular material is stone, partly dolomitic, and sparry calcite cement) with calcareous shale, with sub 40-50 percent fragmental fos ordinate chert. Rhythmically sil allochems, in continuous interbedded biomicrite and but unevenly undulating beds fossiliferous clayey micrite averaging about 3 in. thick, similar to unit 3 above, but but as much as 1 ft thick. with an abrupt increase in Rhythmically interbedded proportion of thin laminated with dark-gray thin-laminated micrite and fossiliferous mi clayey micrite and fossilifer- crite to about 40 percent of ous micrite in beds commonly unit. 59ACr-2 consists of less than 1 in. thick. Both are chips taken to represent commonly partly dolomitized, lithology ______34 1,080 and may contain as much as 5. (Middle part of lower one-third 15 percent dolomite locally, of Mlnu-g of pi. 2B) Lime chiefly as dolomitized micrite stone, partly dolomitic, and matrix and as rims around calcareous shale, with sub fossil allochems. Grayish- ordinate chert. Rhythmically black chert silicified biomi- interbedded biomicrite and crite and micrite makes up laminated clayey micrite simi less than 10 percent of the lar to units 3 and 4 above, but unit, chiefly as irregular with abrupt decrease in pro zones of nodules within and portion of interbedded lami oriented with the limestone nated micrite to 5-10 percent. beds. Many paired sets of 59ACr-3 consists of chips biomicrite and fossiliferous taken to represent lithology ____ 25 1,105 micrite beds may be graded 6. (Lower part of lower one-third beds, with sharp bedding sur of Mlnu-g of pi. 2.5) Lime faces at base of calcarenite stone, partly dolomitic, and bed and a gradual decrease calcareous shale, with sub upward in maximum size and ordinate chert. Rhythmically abundance of allochems interbedded biomicrite and through an indistinct com laminated clayey micrite simi monly intertonguing contact lar to units 3-5 above, but with the overlying carbonate with about 40 percent lami mudstone, whose top is marked nated micrite interbeds. Also by a sharply defined surface different in that some fossili at base of next overlying ferous micrite is locally dolo calcarenite bed. The lami mitized to a rock containing nated micrite (carbonate mud- about 80 percent finely crys stone) commonly makes up talline dolomite with relict about 5-10 percent of unit; in calcite allochems making up most of remainder. 59ACr-4 central part of unit, where consists of chips taken to rep beds increase in thickness to resent lithology -_-____ - 64 1,169 as much as 6 in., it makes up 7. (Upper part of Mlnu-f of pi. a proportionately much great 2B) Calcareous shale and er part of unit (locally as limestone, partly dolomitic, much as 30 percent). Fossils with minor chert. Rhythmi include horn corals, colonial cally interbedded biomicrite coral, brachiopod fragments, and laminated clayey micrite, Bryozoa (including Archi locally as much as 60 percent medes), and echinoderm dolomitized to finely crystal debris. 59ACr-lf (table 2) line dolomite. Very similar to is a fossil collection. 59ACr- unit 6 above, but with abrupt 1 and 59ACr-la consist of change at contact to about 60 chips taken to represent percent laminated micrite and lithology ______375 1,046 fossiliferous micrite. 59ACr-5 46 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Unit Cumulative Upper member of the Nasorak Formation Continued Thickness Thickness (feet) (feet) Unit Cumulative medium-gray partly dolomi consists of chips taken to rep tized (ranging from 10 to 40 resent lithology _ . 26 1,195 percent replacement dolomite) 8. (Middle part of Mlnu-f of pi. laminated Bryozoa-bearing 2B) Limestone and chert. micrite, probably containing Distinctive unevenly bedded some clay, with fragmental unit. Medium-gray and dark- fossil material commonly mak gray partly dolomitized partly ing up 7-10 percent of the silicified fossil-bearing mi rock; but locally the rock is crite; and grayish-black chert a coarse crinoid biomicrite (silicified fossil-bearing mi with fragmental fossil mate crite) chiefly as irregularly rial ranging from 50 to 90 lenticular nodules in the lime percent and including a few stone, commonly having in foraminifera. The limestone distinct gradational contacts is chiefly in beds about 1 ft with the limestone. Beds ap thick or less, rhythmically pear relatively continuous and interbedded with shaly clayey average about 9 in. in thick carbonaceous micrite in beds ness, but pinch and swell from as much as 4 in. thick that about 3 in. to about 1% ft in makes up about 30 percent of thickness, giving rise to a unit. Sets consisting of a nodular aspect of the beds; limestone bed and a shaly adjacent beds appear to com interbed in many places re pensate one another. One dip- semble graded beds; such sets slope exposure shows that the commonly range in thickness nodular features are roughly from 1 to 2 ft. Recognizable circular in plan and average fossils include horn corals and about 1 ft in diameter. Chert colonial corals (most heads is commonly in the central making discrete small lenses parts of the "nodules," but within limestone beds) as well does not seem to be requisite as fragmental echinoderm and for their formation. They are leafy bryozoan debris. 59ACr- probably differential compac 8f (table 2) is a fossil collec tion features. 59ACr-6 con tion. 59Acr-8 consists of chips sists of chips taken to repre taken to represent lithology- 50(?) 1,335 sent lithology __ __ 49 1,244 (Bedding plant fault within 9. (Lower part of Mlnu-f of pi. unit 10 rocks makes total 2B) Shale and subordinate thickness of unit uncertain.) limestone. Grayish-black cal 11. (Upper one-fourth of Mlnu-d of careous clay shale with pi. 2B) Limestone and calcare abundant close-spaced sheared ous shale. Very similar to bedding surfaces, many show unit 10 above, but includes ing small slickenslides; with about 40 percent shaly mi 20-30 percent interbedded crite, probably containing medium-dark-gray to dark- some clay; the limestone beds gray clayey micrite, locally are more generally medium containing as much as 30 per dark gray to dark gray and cent unidentified calcite allo- contain a generally higher chems, but commonly 5 per proportion (commonly 30-40 cent or less. The limestone percent) of fragmental fossil (clayey micrite) occurs in debris and may locally contain lenses as much as 4 in. thick as much as 20 percent fine and about 3 ft long and ap quartz silt. In addition, the pears to follow specific hori thickness of sets of limestone zons, so that some resemble and interbedded mudstone is more nearly uniform and gen boudinage structures. 59ACr- erally about 1% ft thick. 7 consists of chips taken to Recognizable fossils include represent lithology . 41 1,285 horn corals, colonial corals 10. (Mlnu-e of pi. 2B) Limestone (chiefly as lenticular heads and calcareous shale. Chiefly made up of single colonies MEASURED BEDROCK SECTIONS 47

Upper member of the Nasorak Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative 13. (Topmost part of lower one-half from 1 in. to 1 ft thick and of Mlnu-d of pi. 2B) Lime from 6 in. to 5 ft long), as stone. Medium-gray very well as f ragmental echinoderm coarse grained biosparite, and leafy bryozoan debris. locally partly dolomitized, con 59ACr-8Af (table 2) is a fos taining local coral fragments. sil collection. 59ACr-8a con Individual beds as much as sists of chips taken to repre 31/2 ft thick, and unit stands sent lithology -____. ______66 1,401 out as a thick-bedded zone between the thinner bedded 12. (Lower part of upper one-half units above and below. of Mlnu-d of pi. 2B) Lime 59ACr-9a consists of chips stone, with minor chert and taken to represent lithology. 14 1,500 dolomite. Chiefly medium- gray to medium-dark-gray 14. (Lower one-half of Mlnu-d of laminated fossiliferous mi- pi. 2B) Limestone, with minor crite and medium-grained to chert and dolomite. Virtually very coarse grained crinoid the same lithology and bed bryozoan biomicrite (contain ding characteristics as unit ing as much as 70 percent 12. A few of the chert speci f ragmental fossil debris), mens show possible ghosts of locally dolomitized (as much spicules in thin section (fig. as but generally less than 50 24). 59ACr-9b consists of percent dolomitized, and local chips taken to represent 127 1,627 ly silicified to grayish-black lithology _-______chert) (cherts commonly con IB. (Upper one-third of Mlnu-c of tain as much as 30 percent pi. 2B) Shale and limestone. euhedral very finely crystal Grayish-black silty calcareous line dolomite, and may contain shale or shaly micrite (prob as much as 60 percent relict ably dolomitized in places), in calcite). Chert and dolomite beds Vz-6 in. thick averaging form irregular patches and about 3 in.; interbedded dark- zones in and along the thin gray dolomitized (as much as limestone beds and make up about 5 percent and 20 per cent of the unit volume, re spectively. A few distinctive interbeds of very coarse grained crinoid biosparite that are also dolomitized in irregular patches, locally con tain as much as 50 percent dolomite, chiefly as replace ment of intergranular cement. Individual limestone beds range from less than 1 in. to about 1 ft in thickness, gen erally averaging about 10 in. thick. Thin shaly partings, averaging about % in. thick, commonly separate the lime stone beds, but all together make up only about 1-5 per cent of unit. Except for f ragmental echinoderm and leafy FIGURE 24. Texture of spicular(?) chert in the Nasorak Formation. Most bryozoan debris, no fossils of the light-gray material is very finely crystalline to aphanitic micro- were recognized, and none granular quartz, A few percent dolomite is also present in the light- were collected. 59ACr-9 con colored fraction, as disseminated very finely crystalline euhedral rhombs. The dark material is chiefly disseminated fine carbon and tiny crystals sists of chips taken to repre of disseminated pyrite, but it also includes a few percent of very finely sent lithology ______-, 85 1,486 crystalline calcite. 59ACr-9b#2. 48 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Upper member of the Nasorak Formation Continued Thickness Thickness (feet) (feet) Unit Cumulative Unit Cumulative irregular patchy zones) silt- 40 percent) silty (about 10 bearing (generally less than percent quartz silt) fine 6 percent quartz silt) carbo grained biomicrite containing naceous shaly micrite that as much as 50 percent frag- may contain a few percent mental fossil material, now clay locally. The chert occurs chiefly ghosts, in discontinuous as indistinctly bordered lenti uneven beds %-6 in. thick. cular nodules within the lime The calcareous shale or shaly stone beds and makes up about micrite makes up about 50 50 percent of the unit. The percent of the unit. 59ACr- chert-limestone beds appear 10 consists of chips taken to relatively continuous and are represent lithology ______12 1,639 rhythmically interbedded with 16. (Lower two-thirds of Mlnu-c of thin (commonly less than Vz pi. 2.B) Limestone, partly in. thick) calcareous shale silicified and partly dolomi- partings, but have very un tized. Chiefly medium-gray even undulating bedding sur very coarse grained crinoid faces such that individual beds biomicrite containing as much pinch and swell in thickness as 60 percent fragmental fos from about 1 in. to as much sil material, locally with as as 8 in. in distances of 1-2 ft. much as 40 percent replace This gives the chert-limestone ment chert and 15 percent re beds the general aspects of placement dolomite as matrix zones of nearly disconnected and rimming cell structures lenticular nodules alined along in and around calcite allo- bedding. Thinning of one bed chems; in even continuous is generally compensated by beds ranging in thickness thickening of adjacent beds, from 2 in. to 1^ ft (fig. 6). suggesting a compaction ori Dark-gray thinly laminated gin for the nodular aspect. dolomite dolomitized micrite In lower 25 ft of unit, chert makes up 5-10 percent of content decreases slightly unit as very thin interbeds, to about 35 percent shaly in and laminae within the lime terbeds increase in thickness stone beds. Dark-gray chert to as much as 1 in. 'making occurs as thin (Vz to 3 in. up as much as 10 percent of thick) discontinuous irregu the rocks and some thin larly surfaced zones along zones are not so prominently bedding planes and a few "nodular" in bed aspect. Basal gmall irregular nodules within 6 ft of unit is a zone con limestone beds. The thin in taining a few thick beds (as ternal lamination of much of much as 4 ft thick) of coarse the limestone has a distinctive grained crinoid biomicrite "crinkly" uneven aspect, per from which a few horn corals haps as a result of differential and Bryosoa were collected compaction over the coarse (fig. 5). 59ACr-12f (table 2) echinoderm debris. 59ACr- is a fossil collection. 59ACr- llf (table 2) is a fossil collec 12 consists of chips taken to tion. 59ACr-ll consists of represent lithology , - . _- 75 1,740 chips taken to represent lith 18, (Upper part of Mlnu-a of pi. ology ______--_____-_ 26 1,666 25) Mudstone and limestone. 17. (Mlnu-b of pi. 25) Chert, lime Grayish-black calcareous silt stone (partly dolomitized), clay mudstone and interbedded and calcareous sh^le. Grayish- dark-gray silty clayey(?) black chert^silicified (60-75, partly dolomitized fossil-bear percent) carbonaceous (about ing micrite. In upper 25 ft 15 percent black opaque films) of unit the mudstone is in micrite; and medium-dark- thin, locally shaly, beds 1-4 gray dolomitlggd (commonly in. Thick, rhythmically inter from 10-50 percent replace bedded with silty micrite beds ment dolomite in apparently of similar thickness (fig. 5). MEASURED BEDROCK SECTIONS 49

Thickness Upper member of the Nasorak Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative to that in unit 16. Fossils in- In lower 33 ft of unit lime include several brachiopods stone is virtually absent; the and, in thin section, a few mudstone is in beds as much possible Foraminifera as well at 1 ft thick and contains as echinoderm and bryozoan minor but distinctive small debris. 59Acr-15f (table 2) patches of pyrites and pyri- is a fossil collection, of which tized brachiopod shells and a split serves to represent the other shell fragments. Bed lithology ______110±(15) 1,920 + (20?) ding is masked in places by Lower member of the Nasorak For close-spaced fracture cleavage mation (Mini) : that gives the outcrop a shaly 21. (Mini of pi. 2B) Mudstone and aspect but only locally follows limestone. Very similar to direction of bedding. 59AO- unit 18, but no pyritized fos 13f (table 2) is a fossil collec sils were noted. Base not tion. 59ACr-13 consists of exposed __.______- 50±(20?) 1,970 + (20?) chips taken to represent In a structurally very dis lithology , 58 1,798 turbed zone about 700 ft 19. (Lower part of Mlnu-a of pi. farther east, rocks thought to 2B) Limestone, Medium- be appropriately assigned to dark-gray coarse-grained cri- unit 21 are associated with noid biomicrite, locally partly limestone beds, chiefly coarse dolomitized in irregularly grained medium-dark-gray bedded strata ranging in biomicrite, that includes a thickness from less than 1 in. brachiopod fauna closely simi to as much as 4 ft. Dark-gray lar to that collected from silty(?) micrite in thin discon lower member of Nasorak tinuous laminae and partings Formation in sea cliff section as much as 1 in. thick are sub at Cape Thompson, pi. 2A. ordinate interbeds, Echino- 59ACr-19-20f and 59ACr- derm debris and subordinate 21f are fossil collections (table bryozoan fragments are the 2). 59ACr-19-20 and 59ACr- only fossils recognized. 21 consists of chips taken to 69AO.14 consists of chips represent lithology. Probably taken to represent lithology _ 13+ (20) 1,811+ (20) several tens of feet of beds are Total thickness of upper represented ______._____ (50?) 1,970+ (70?) member of the Nasorak Base not exposed. Formation ._...... __..__ 1,811+ (20) Total thickness of lower Cape Thompson Member of the member ._...... __.__.... 50 +(70?) Nasorak Formation (Mine): Total thickness of Nasorak 20. (Mine of pi. 25) Limestone. Formation _._..___._._ 1,970 +(70?) Medium-gray (weathers to Sajigvik thrust fault zone. pale grayish orange) partly Kogruk(?) Formation (younger than dolomitized (locally as much Formation), as 15 percent dolomitized PERMIAN AND TRJASSIC ROCKS WEST SECTIONS micrite matrix and rims on [Sections of Permian and Triassic rocks measured in sea-cliff exposures at fossil fragmints) very coarse Agate Rock, by Reuben Kachadoorian and I. L. Tailleur, July 1958] grained crinotd-bryozoan biomicrosparite (in places a fine SHUBLIK FORMATION (TRIASSIC) Ogotpruk Formation (greenish-black rudite rather than a very claystone and grayish-black silt- coarse arenite) generally eon* taining about 75 percent frag- stone, sheared nea,r contact). Probable disconformity. (Although mental fossil allochemB. beds are generally accordant and Irregularly bedded discontinu rela.tip.ns a^re somewhat obscured ous (?) relatively even sur by sheading Pf basal beds pf over faced bids range in thickness lying Ogotoruk, there is a few feet from a few inches to about of reJiff on the contact that may l^i ft. "Crinkly" uneven dis* be attributable to pre-Ogotoruk continuous internal lamina erosipn of uppermost beds of the tion is common, very similar Shublik.) 50 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

Shublik Formation ( ) : Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative 12. Chert and shale. Medium-gray 1. Shale and minor chert. Dark- chert with a dull to glassy gray shale, generally thinly luster in thin slightly uneven bedded in lower half of unit nodular beds 1-8 in. thick. A (beds 1/2-1 in. thick), but with zone of shale in beds gener some thicker beds (as much ally less than 2 in. thick forms as 1 ft thick) in upper half. the basal 3 ft of the unit 17 125.5 Top 5 ft of unit contains a 13. Chert and shale. Interbedded few chert beds, 2-4 in. thick, chert and shale in approxi interbedded with shale in beds mately equal amounts in beds about 1 ft thick ...... _ 23 23 3-6 in. thick; contains some 2. Shale. Dark-gray thin-bedded concretions as much as 3 in. hard (siliceous?) shale ._ . -. 1.5 24.5 in diameter ______-. . 6 131.5 3. Chert. Dark-medium-gray chert 14. Shale. Thinly bedded shale with in beds averaging 5 in. thick; concretions as much as 1 in. beds in upper half 5-10 in. in diameter .______133.5 thick, and beds in lower half 15. Shale with some chert. Predom 2-5 in. thick ._. ._. _ _ .. 13 37.5 inantly shale but including 4. Chert and interbedded shale. several chert beds about 3 in. Chert in beds 2-4 in. thick, thick. Sparse concretions as interbedded with shale in beds much as 3 in. in diameter 4 137.5 1-2 in. thick _._.__._ ____. ______. 43.5 16. Massive chert; locally silty 18 155.5 5. Limestone. Medium-gray lime 17. Chert. Interbedded chert and stone in beds 1-4 in. thick . - _ 6 49.5 silty chert; locally weathers 6. Shear zone ______.-_-_._ 1.5 51 yellow to dark yellow orange.. 2 157.5 7. Cherty limestone with abundant 18. Shale and chert. Predominantly Monotis fossils. Cherty lime shale with a few chert beds, stone in beds 1-8 in. thick, 2-3 in. thick . 3 160.5 commonly medium gray in the 19. Cherty silt ______.8 161.3 central part of a bed grading 20. Shale, mudstone, and chert. to light gray at the margins, Black shale with interbedded with a few interbeds of shale. mudstone and silty shale in Shear zone 1 ft thick 6 ft zones %-2 In. thick. Top half below top of unit. Monotis of unit contains a few dark- abundant throughout the gray to black layers of chert unit __-_-______--______- __- _ 23.5 74.5 about 1 in, thick _ _ .__ 2.5 163.8 8. Chert and shale. Black chert in 21. Chert. Dark-gray slightly silty beds %-2 in. thick, inter in beds ranging in thickness bedded with black calcareous from 1 or 2 in. Jn lower part shale, most commonly as of unit to 6 in. in upper paper-thin laminae but locally part. Zones Me~-2 in. thick as much as 1 in. thick .. . 83.5 that weather to dark yellow 9. Chert and shale. Black chert give the unit an interbedded in beds 1-6 in. thick, with aspect _ __ _-______,__ __ 168.8 slightly undulating bedding 22. Shale. Black shaly mudstone in surfaces; interbedded calcar terbedded with silty shale in eous shale in beds as much layers %-2 in. thick. Upper as 2 in. thick. Basal part of half of unit contains a few this unit is gradational with dark-gray to black chert lay top of underlying unit 10 15 98.5 ers about 1 in. thick _ _ 171.8 10. Calcareous siltstone and shale. 28. Chert. Dark-gray earthy chert Thinly bedded limy siltstone that weathers to a dark yellow with interbedded shale. In in beds that grade in thickness cludes one marcasite-rich zpne from 1 or 2 in. at base to about 9 in. thick in a shaly about 6 in. at top -_ _ _ _ _ 174.8 bed that grades into limy 24, Shale. Black shaly mudgtone siltstone ______-_ _ 104.5 and silty shale, in beds H-3 11. Interval inaccessible in cliff. in. thick. A few chert inter Rocks weather dark gray to beds about 1 in. thick occur black with yellow stain . .-_ 108.5 in upper 2 ft of unit -__-_ __ 180.8 MEASURED BEDROCK SECTIONS 51

Shublik Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) top of unit is a distorted nod Unit Cumulative 25. Chert. Dark-gray earthy chert ular red jasperoid zone about beds ranging in thickness 8 ft thick. In lower part of from 1 or 2 in. at base to unit some dark streaking, 6 in. at top. Locally, zones about 2 in. thick, that ex from Me-2 in. thick selec presses stratification. Base of tively weathered to dark- unit not exposed .___ _ 28+? 131+? yellow ______4 184.8 Unit 3 is oldest stratigraphic unit 26. Shale. Black shaly mudstone exposed at the surface in core and silty shale interbedded in of a minor anticline, whose layers from % to 3 in. thick. banded aspect in outcrop gave Top iy2 ft of unit contains a Agate Rock its name. few chert interbeds about 1 in. PERMIAN AND TRIASSIC ROCKS EAST SECTIONS thick _ . ______3 187.8 [Sections of Permian and Triassic rocks in sea-cliff exposures at the mouth of Imikrak Creek and nearby to the west. Shublik Formation measured 27. Shale. Medium-dark-gray finely by C. L. Sainsbury, R. H. Campbell, Reuben Kachadoorian, and D. W. laminated muddy shale that Scholl, August 1958; the lower part of the Siksikpuk Formation added by weathers to yellowish orange__ 2 189.8 R. H. Campbell and D. R. Currey, August 1959] 28. Shale. Soft black shale in beds SHUBLIK FORMATION (TRIASSIC) commonly ranging in thick Ogotoruk Formation: Grayish-black thin-bedded to shaly ar ness from % 6 to 2 in. and gillite, with interbedded mudstone and siltstone in beds averaging about 1% in. Up Vis-1/* in. thick; persistent but discontinuous zone of red per 10 ft of unit has a rela alteration within a few feet of the underlying contact. The tively massive aspect. Basal Ogotoruk beds are intensely sheared and slickensided 3 ft is a clay shale with a much more so than the more competent beds of the under probable high-iron content, as lying Shublik. The basal Ogotoruk beds are covered, as is it weathers to dark yellow ______13 202.8 the contact, in the immediate vicinity of the measured Possible unconformity (beds may be Shublik section. They are, however, exposed in the sea very slightly discordant). cliffs in a minor anticline about Vs mile west of the expo Siksikpuk Formation. sures where the section was measured. Accordant contact: The contact appears to be an accordant SIKSIKPUK FORMATION (PERMTAN) depositional contact, even though the overlying beds are Shublik Formation. intensely sheared. The shearing is interpreted as the nat Possible unconformity (beds may be ural response of the relatively incompetent Ogotoruk rocks very slightly discordant). to the folding of the more competent Shublik beds, together Siksikpuk Formation (Ps): with the effects of subsequent drag from above by the over 1. Chert and argillite, nodular. riding Ibrulikorak-Agate Eock thrust sheet. Again, the Greenish-gray to greenish- contact zone is covered in the immediate vicinity of the black chert in thin (as much measured Shublik section, and the relations are described as 6 in. thick) lenticular nod from an outcrop to the west the same outcrop as that ules that make up relatively from which the above description of the basal Ogotoruk continuous uneven beds that beds was made. average 3-4 in. thick. Inter- Thickness bedded with greenish-gray (feet) Unit Cumulative argillite beds of similar thick Shublik Formation ( ): ness ______43 43 1. Mostly covered. Float indicates 2. Chert and argillite, evenly the topmost beds are greenish- bedded. Interbedded chert and gray to black siltstone or argillite similar to the rocks argillite, underlain by a zone of unit 1, but in relatively of shaly M

Thickness Shublik Formation Continued (feet) Thickness Unit Cumulative (feet) Unit Cumulative measured, is predominantly 3. Limestone and chert. Medium- shale ___._.______85 200 olive-gray to medium-gray Accordant contact. (weathers to grayish orange) Siksikpuk Formation. Monotis-rich limestone, locally SIKSIKPUK FORMATION (PERMIAN) cherty (including some ir Shublik Formation. regular small patches of dark- Accordant contact. reddish-brown chert), in beds Siksikpuk Formation (Ps): generally from 2 in. to 1 ft thick; some interbedded dark- 1. Argillite. Greenish-gray argil gray to greenish-gray chert. lite in a single relatively con Unit crops out as a relatively tinuous bed 1-2 ft thick. continuous series of ledges Internally laminated, with with gentler more generally relatively sparse thin discon vegetated slopes above and tinuous lenticular laminae of below -...... - 20 60 slightly darker color ...... 2 2 2. Chert and subordinate inter 4. Covered interval. Subdued slope- bedded argillite. Greenish- forming unit, may be shaly gray chert apparently a sili- here, but to the west limestone cified argillite, as it displays and chert similar to unit 3 the same internally laminated above, with some interbedded structure as the argillite black shale, crop out at what appears to be the same strat- predominates as continuous igraphic horizon as this cov beds averaging about 3 in. ered interval (thickness esti thick. The chert is regularly interbedded with greenish- mated) .- ..._...... _. 35 95 gray argillite beds that aver 5. Chert and shale, with some age about 1 in. thick .. 15 17 limestone. Grayish-black to 3. Argillite, variegated red and greenish-gray chert in beds green. Greenish-gray argillite 1-4 in. thick; interbedded with in zones commonly 1-3 ft black to greenish-black shale thick, regularly interlayered and subordinate interbedded with moderate-red argillite in Mowers-bearing limestone. relatively continuous strati- The black chert and shale graphic zones commonly about locally contain thin laminae 1 ft thick. The interlayermg in which Halobia fossils are of red and green generally abundant .. _...... _.. 20 115 follows bedding and from a 6. Shale. Predominantly thin- distance looks like true in- bedded black shale, with a terbedding; in detail, however, distinct sulfurous smell when edges of red layers are very freshly broken; irregularly uneven in many places, and interbedded with minor crosscutting irregular to vein- amounts of thin-bedded dark like apophyses of red into gray chert. In places the shale green indicate that the zones near the base weathers to red of red argillite formed by al dish colors. A few feet above teration of green argillite. Red the base, a continuous thin zones appear to reflect per (1-2 in. thick) layer of very meable horizons, and many of light gray bentonitic(?) clay. the crosscutting apophyses Considerable lateral gradation follow joints ___--___-_ - 15 32 of the unit is indicated by the 4. Argillite, containing sparse cal presence, a short distance to careous fossils near base, and the west, of a 12-ft-thick zone minor interbedded chert. containing abundant thin- to Chiefly greenish-gray to dark- medium-bedded greenish-gray greenish-gray argillite, com argillite and limy argillite in monly weathering to olive which Monotis and Halobia gray and locally to various fossils are locally abundant; reddish browns. Most com this zone lies at about upper monly beds are 1-3 ft thick, middle of unit, which, where with faint internal laminae MEASURED BEDROCK SECTIONS 53

Siksikpuk Formation Continued Thickness (feet) Thickness Unit Cumulative (feet) Unit Cumulative cates that units are accordant; best expressed as color band total thickness of Siksikpuk, as ing on weathered surfaces. estimated from structure sections, Greenish-gray chert in con probably no greater than 400 ft. tinuous even layers, most com Consequently, it is estimated that monly 1-2 in. thick, inter- no more than 100 ft of lower part bedded in argillite at irregular of Siksikpuk Formation is missing intervals. Chert makes up very from these sea-cliff exposures.) minor part of unit. Carbonate Tupik Formation of the Lisburne veinlets heal fractures in both Group. argillite and chert in some places. Near base of unit, two JURASSIC OR CRETACEOUS ROCKS argillite beds contain sparsely The Ogotoruk and Telavirak Formations, as well scattered carbonate fossils that include only brachiopods as many parts of the Kisimilok and Portress Moun and gastropods. 59ACr-89f is tain (?) Formations, are made up of a monotonous a collection of fossils. 59ACr- sequence of similar lithologic types in variable pro 89 consists of chips taken to portions and in beds of variable thickness. The represent lithology. A zone of following classification was devised for field use in fracturing and high-angle faulting intersects the sea these rocks to serve as an abbreviated description coast at the mouth of Imikrak of the general lithology and bedding characteristics Creek; thickness exposed is of an outcrop, to which distinguishing characteris therefore minimum, and a tics, if any, could be added. The classification is stratigraphic thickness of 20 arbitrary, and all gradations between the various ft or more may be missing.__._.__210 + 20? 232 + 20? types may be found. It has, however, proved to be 5. Black shale, argillite, and chert, partly covered. Predominant a convenient field notation and for brevity is re ly grayish-black gypsiferous tained in describing the measured section below. (?) limonitic(?) shale that weathers to variegated shades M. Massive to thick-bedded medium-dark-gray to dark-gray of red, orange, yellow, red mudstone having little or no internal bedding expression. brown, and white against the In many places close-spaced fracture cleavage most com blackish slope. In upper 10- monly axial plane cleavage, but, locally, pencil slates have 15 ft of unit there are some formed at some fold crests and troughs. Rarely fissile thin (%-3 in. thick) interbeds enough to be called a shale. of dark-greenish-gray argil Mg. A dark-greenish-gray subtype of M, commonly sheared. lite and greenish-gray chert___. 45 277 + 20? May superficially resemble some of the greenish argillites 6. Argillite and minor limestone. of the Siksikpuk and Shublik Formations. Generally more Dark-gray to dark-greenish- argillaceous than most of the type-Af rocks. Common at, gray argillite, commonly cal but not restricted to, the base of the Ogotoruk Formation. careous, and in places silty, Mt. Resembles M but commonly has recognizable internal predominates in beds as much bedding expressed as thin laminae of alternating dark-gray as 5 ft thick; internal lamina and slightly lighter colored layers containing slightly more tion expressed as uneven dis abundant quartz silt. continuous thin (commonly about % in. thick), greenish- MS. Mudstone of type M or Mt with very thin interbeds of gray zones in predominantly medium-dark-gray fine-grained sandy siltstone (gray- darker rock. One interbed, 4 wacke), generally rhythmically interbedded in cycles less in. thick, of medium-dark- than 2 in. thick. Sandstone beds locally have small bottom gray silty limestone contains marks, most of which appear to be casts of small pellets a few calcareous fossils: a (fecal?). Low-angle internal cross-lamination is locally horn coral, brachiopods, and visible in sandy siltstone. Cycles are graded beds. a gastropod. 59ACr-88f is a Sm. Zone predominantly M or Mt with prominent irregularly fossil collection. 59ACr-88 interbedded lenses of thick-bedded to massive fine- to me consists of chips taken to rep dium-grained muddy sandstone (graywacke). Individual resent lithology. Base of unit beds are apparently discontinuous, but some zones may be not exposed -______.____...._. 20 + ? 297+20?+? traced a mile or two along the strike. High-angle fault contact. (Farther SM. Interbedded mudstone of type M or Mt and muddy very inland, the map configuration of fine-grained to medium-grained graywacke sandstone in the Siksikpuk-Tupik contact indi- nearly equal amounts. Generally rhythmically interbedded 54 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

in cycles from a few inches to IVs ft thick. The cycles are Thickness (feet) graded beds. Bottom marks are common and some are Unit Cumulative large. Carbonaceous trash is abundant in some sandstones, thickness was corrected to allow for particularly in the Telavirak Formation. Low-angle cross- repetition 150 1,680 lamination is moderately common in sandstone beds. The 8. Partly covered. Chiefly Mt with minor sandstone-mudstone ratio is generally less than 60/40. interbedded SM, base gradational S. Massive to thick-bedded silty very fine grained to medium- with underlying unit 9. Locally grained graywacke sandstone with little or no mudstone folded, apparent thickness may be too interbedded. Sandstone commonly shows little or no in large by a factor of 2 because of ternal bedding laminae, but, locally, a few beds split fairly drag folds having high amplitudes easily along internal bedding planes on which some oriented and wave lengths of 3-20 ft .... _. 150 1,830 mica may be seen. Bottom marks are rare, perhaps because 9. Rhythmically interbedded strata rang shale interbeds are rare. ing from Ms to Sm in cycle thickness, SMt. Similar to SM but intermediate with S in that cycles with subordinate interbedded Mt...... 170 2,000 and beds are as much as 2 ft thick and sandstone-mudstone 10. Chiefly Mt with minor amounts of ir ratios are greater than 60/40. Bottom marks are common regularly interbedded phosphorite in and may be large. lenses as much as 1 in. thick. Locally some structural contortion, but no TELAVIRAK FORMATION, PARTIAL SECTION, NIYIKLIK CREEK appreciable repetition _ 60 2,060 [Section measured by R. H. Campbell and D. R. Currey, July 22, 1960. Thicknesses measured by pacing the outcrop width of the steeply dipping 11. Contorted M with minor Mt and some beds and estimating the correction for local dips] Mg interbeds; contains a few phos phorite nodules locally associated Top not exposed. Beds younger than unit 1 with Mg. Contortion does not appear are covered and lie in structurally com to represent significant repetition .... 200 2,260 plex terrain. Thickness 12. Largely covered. Appears from float to (feet) be largely M or Mt grading to MS at Unit Cumulative 1. Covered. Judging from float, the rocks base _ _ 200 2,460 are chiefly of type SM, similar to unit 13. Chiefly SM with well-developed bottom 2 below, (thickness estimated) 100 100 marks including good load casts and 2. Largely covered. Chiefly SM with in organic (?) bottom marks. Locally a terbedded MS, and MS becomes pre thin phosphorite(?) lens is present dominant near the base _ 250 350 in a mudstone interbed. Top 25 ft of 3. Mostly MS with interbedded Mt. Grades unit is gradational into rocks of MS- from Mt at top, through a central cycle thickness . _____ 100 2,560 thick zone of MS with abundant car 14. Largely covered. Mostly contorted M bonaceous debris and subordinate in mudstone 300 2,860 terbedded Mt to Mt again at base_.____ 350 700 15. Partly covered. Chiefly MS but upper 4. Predominantly MS with interbedded 10 ft of unit is gradational zone to SM. Grades from chiefly MS at top; mudstone of overlying unit 14 280 3,140 through interbedded MS and SM 16. Chiefly SMt with a few interbeds of M. that, near base, includes a prominent The sandstone beds are as much as 5 zone of SM with abundant carbona ft thick and locally have a slabby in ceous debris; to MS at base______. 200 900 ternal parting 200 3,340 5. Chiefly MS and some interbedded SM, 17. Unit grades from Mt with locally abun with minor amounts of Mt inter dant phosphorite lenses at base to MS bedded in some zones. Sandstones at top 125 3,465 locally carry some carbonaceous de 18. Partly covered. Chiefly M, with upper bris. (The thickness indicated allows 100 ft of beds grading to Mt, and a correction for the double repetition lower 120 ft of beds have slaty to of about 15 ft of the beds in one large shaly aspect. Minor amounts of phos drag fold exposed in the cutbank of phorite found as nodules in lower the stream.) . .___ _ 180 1,080 middle part of unit, where beds are 6. Chiefly Sm with abundant carbonace somewhat contorted 525 3,990 ous debris. Basal 300 ft is largely 19. Covered interval 70 4,060 covered, but appears to contain sub ordinate interbedded MS, and prob 20. Chiefly MS but grades to Mt at top. ably grades to predominantly MS at Lower 150 ft is largely covered 250 4,310 the base 450 1,530 21. Thick unit of M mudstone 150 4,460 7. Chiefly SM with only minor inter 22. Thin zone of MS having relatively uni bedded MS near base. Well exposed; form structure _ . 15 4,475 one small drag fold was seen, and 23. Sheared, contorted M...... _ 25 4,500 UNCONSOLIDATED DEPOSITS 55

Thickness (feet) lithology (chiefly red and green chert that was prob Unit Cumulative ably originally derived from the Siksikpuk and 24. Thick unit of MS, partly covered near base. Some drag folding is evident, Shublik Formations) were found on the crest of an chiefly with wave lengths of 1-3 ft, adjacent ridge of Lisburne bedrock at an altitude and apparent thickness may be too of more than 500 feet. The deposit ranges in thick large by as much as one-fourth.______450 4,950 ness from 0 to more than 20 feet observed in one 25. Interbedded strata of 5- and SMt-cycle stream cut where the base of the deposit was not thickness ______135 5,085 exposed. 26. MS, base not exposed -_-__-______._____._ 50+ 5,135 The gravels consist chiefly of well-rounded pebbles, Ogotoruk Formation (largely mudstones of relatively few cobbles, and generally less than 25 Mi and M types). percent sand, silt, and clay (fig. 25A). The deposits Probably not more than 100 ft of strata are porous and relatively well drained. The most represented by covered interval at con tact between the Ogotoruk and Telavirak abundant lithologic types are gray and brown chert, Formations in Niyiklik Creek. cherty limestone, and dolomite (probably derived from the Lisburne Group), with somewhat subordi UNCONSOLIDATED DEPOSITS nate graywacke sandstone and mudstone (probably Unconsolidated deposits cover at least half of the derived from the Jurassic? and Cretaceous rocks to area of plate 1. They generally range in thickness the east), and, most commonly in the coarse sand and from a few feet to a few tens of feet and in only a granule fraction, green and red chert (probably de few places exceed a hundred feet. The various types rived from the Siksikpuk and Shublik Formations). of deposits are: colluvium; fluvial gravel, sand, and All these may have been locally derived; however, silt (both terrace and modern flood-plain deposits); several pebbles and small cobbles of orthoquartzite water-laid gravel and sand of uncertain origin (flu were found for which no local source is known. Lo vial or marine at high altitudes; marine deposits of cally, irregular patches of the gravel are cemented the modern shoreline and at low altitude along older with limonite(?), but most of the deposit is uncon shorelines nearby; lake, lagoon, and swamp deposits solidated and friable. (chiefly peat and muck); wind-deposited sand and The age of the deposit has not been closely ascer silt; and gravel and sand of the modern beach. All tained, but the high altitudes at which it is found but the present beach and flood plains are commonly suggest that it is the oldest unconsolidated deposit on covered with tundra vegetation. Ice is an abundant the post-Cretaceous erosion surface. Stream-terrace constituent in most of the unconsolidated deposits; deposits of the Kukpuk River that are at least as old it is present as both vertical wedges and horizontal as Sangamon occur at much lower altitudes in the layers. The interstitial ice of the fine-grained sedi same area. From this it is inferred that the Ilyirak ments is much less spectacular but quantitatively Gravel is Yarmouth or older and may be as old as more important. late Tertiary; hence, it is herein assigned a Tertiary or Quaternary age. TERTIARY OR QUATERNARY DEPOSITS The environment in which the gravel was de ILYIRAK GRAVEL posited is uncertain. The deposits are much more The oldest of the unconsolidated deposits is prob cleanly washed and better rounded than those of the ably the gravel that mantles the upper flanks on the younger terrace and flood plains that are clearly south side of the Kukpuk River valley from its junc river deposited, yet the bulk of the Ilyirak Gravel tion with the Ipewik River west to the drainage of lies wholly within a broad lowland that has appar Ilyirak Creek, from which the gravel deposit is ently been carved from bedrock by the Kukpuk River herein named the Ilyirak Gravel. The gravel covers and its tributary streams. The higher parts and a single relatively continuous area between altitudes remnant traces of the deposit are at altitudes that of about 150 feet and about 300 feet. At the lower correspond roughly with the highest clearly recog altitudes it is overlapped by younger stream-terrace nizable strath terrace level of the Kukpuk and Ipewik deposits of the Kukpuk River. The upper limit seems River valleys, and the Ilyirak Gravel could be an old to be erosionally controlled. Parts of the continuous stream-deposited terrace. On the other hand, these blanket deposit have been found at altitudes of as altitudes are also approximately accordant with the much as 415 feet, pebbles are mixed with the col altitude of the break in slope at the top of the wave- luvium at higher altitudes on some adjacent slopes, cut bedrock plain north of the mouth of the Kukpuk and, in addition, frost-broken fragments of exotic River (see Kachadoorian, 1966, p. 51-52 and pi. 1). 56 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

60ACr-110(-5.4- -8.8)

4.0 2.0 1.0 0.5 0.25 0.125 0.031 0.016 256.0 64.0 16.0 4.0 2.0 1.0 0.5 0.25 0.125 0.031 0.016 GRAIN SIZE, IN MILLIMETERS GRAIN SIZE, IN MILLIMETERS A. llyirak Gravel B. Saligvik Gravel

58AKd-c-83

/-59ACr-144

4.0 2.0 1.0 05 0.25 0.125 .. 0.0310.016256.0 64.0 16.0 4.0 2.0 1.0 0.5 0.25 0.125 _ _ 0.031 0.016 GRAIN SIZE, IN MILLIMETERS GRAIN SIZE, IN MILLIMETERS c. Stream-Terrace Deposits D. Chariot Gravel

0 256.0 64.0 16.0 4.0 2.0 1.0 0.5 0.25 0.125 Q Q62 0.031 0.016 GRAIN SIZE, IN MILLIMETERS E. Colluvium

FIGURE 25. Size distribution curves of samples of unconsolidated deposits.

No exposures of the llyirak Gravel were found in SALIGVIK GRAVEL which the original sedimentary structures could be Another relatively continuous deposit of uncon observed. The evidence so far seems compatible with solidated gravel and sand occurs at relatively high either stream-terrace or marine (or estuarine) beach altitude (as much as 350 ft) along the east flank of depositional environments. Saligvik Ridge, from which it is here named the UNCONSOLIDATED DEPOSITS 57

Saligvik Gravel. The deposit trends north-northeast. north indicates that it is younger than the erosional The southern half forms a wedge-shaped apron along gap of the Kukpuk River through the southern the flank of Saligvik Ridge and includes good cutbank Lisburne Hills and the erosional tributary Saligvik exposures at the head of Kiligvak Creek, the type Valley; however, its position on the flank of the locality; the northern half forms a long, low ridge valley indicates that the cut bedrock surfaces of both bounded on the east by the center of Saligvik Valley Saligvik and Ogotoruk Valleys may have been deep and on the west by Saligvik Creek, which appears ened on the east side of the gravel deposit after its to have been incised at or near the contact between deposition. The position athwart the divide between the limestone bedrock ridge to the west and the Ogotoruk and Saligvik Valleys seems enigmatic, unconsolidated gravel. The deposit extends both to particularly with regard to the lower extremities of the north and to the south of the low divide that the gravel in Ogotoruk Valley. These lower sections, separates Ogotoruk and Saligvik Valleys. The high however, are thin and poorly exposed. Moreover, est recognized parts of the deposit are at an alti they are in some places intimately associated with tude of approximately 350 feet. At the northern end, stream-terrace deposits of tributaries to Ogotoruk in the northwestern end of Saligvik Valley, the de Creek. It is possible, perhaps probable, that these posit overlies bedrock at an altitude of slightly less parts of the deposit are more recent stream-terrace than 150 feet. To the south, on the west side of deposits that are made up almost exclusively of Ogotoruk Valley, similar gravels also overlie bed gravel and sand reworked from the Saligvik Gravel rock at altitudes as low as 150 feet. at higher altitude on the flank of the valley. If so, the The deposit consists almost entirely of interstrati- Saligvik Gravel probably represents deposition in an fied well-rounded fine pebble to granule gravel and ancestral Saligvik Valley that once extended to the sand (fig. 255). The internal stratification is fairly south considerably beyond the present divide but regular and even. The pebbles consist entirely of which has migrated northward as a result of capture rock fragments which could have been locally de by the headward erosion of south-flowing Ogotoruk rived. Graywacke is the most abundant rock type, Creek. In any case, the Yarmouth Interglaciation but chert and cherty limestone are also well repre provides the youngest depositional base level with sented. The gravel is commonly overlain by a few which the deposit might be correlated, and it seems inches to about a foot of silt containing abundant quite possible that it is older still, perhaps as old as organic debris and a few inches to a foot of tundra late Tertiary. The deposit, therefore, is herein as vegetation. Locally, thick peat deposits (1-6 ft signed a Tertiary or Quaternary age. thick) have formed in depressions that appear to be The Saligvik Gravel is probably easiest to visualize drained thaw lakes and old stream channels at the as the deposit of a northward-flowing tributary of surface of the Saligvik Gravel. Incised stream-cut the Kukpuk River. However, the possibility that it exposures of the gravel show that it is more than 35 is a marine or lacustrine beach deposit cannot be feet thick in some places. Where exposed and thawed, disregarded: the high degrees of rounding and spher the deposits are well drained and friable, and there icity of the pebbles, the rather well-sorted nature of is apparently little or no clay in the interstitial interstratified sand and gravel, and the lack of matrix. abundant interstitial clay are all features that resem The surface expression of the gravel deposit is ble those of the material of the modern beach and generally distinctive, both on the ground and in the are distinctively different from those of the more vertical aerial photographs. The upper surface is recent stream-terrace and flood-plain deposits that characterized by large ice-wedge polygons separated are clearly related to the Kukpuk River. The chief by channels that are as much as li/^ to 2 feet deep. difficulty of the beach-origin hypothesis is that a Where streams have been incised through the pro coastline at an altitude of 350 feet or more would tecting mat of tundra vegetation, the gravels locally probably have made an island or a long peninsula of display a badlands topography, with steep-walled the ridge along whose flank the deposit was laid, and flat-bottomed gully, in a generally dendritic pattern, it is hard to reconstruct the circumstances which encroaching headward into the tundra-covered sur would permit such an island or peninsula, made up face of generally more gentle relief. chiefly of limestone bedrock, to accumulate a beach The age and origin of the deposit are uncertain. in which graywacke pebbles predominate. Adjacent The age is surely older than the river-terrace deposits bedrock units that would provide a local source of of probable Sangamon or older age that truncate it graywacke detritus would have been exposed only on on the north. The low altitude of its base on the nearby islands. Although a reconnaissance search 58 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA was made, no deposits remotely comparable to the along the rivers and streams, no deposits (with the Saligvik Gravel were found on hillsides where islands possible exceptions of the Ilyirak and Saligvik underlain by graywacke-bearing bedrock might be Gravels, whose association with the prominent cut- expected to have accumulated beach deposits during terrace features is indirect at most) were found on a high stand of sea level. those that were examined. At lower altitudes, ter Although the Ilyirak and Saligvik Gravels are race deposits are most common from 3-15 feet above similar in some of their surface expressions and in the present stream grades. They are generally dis presumed minimum age, they are sufficiently differ continuous, but locally, along some individual ent in grain size, pebble lithology, and maximum al streams, are persistent. Most are probably younger titude to indicate that they are not directly correla than the Sangamon river terrace; but some, particu tive with one another. The lower maximum altitude larly those along Ogotoruk Creek, may be early of the Saligvik Gravel may justify the inference that Sangamon or older, because the stream-cut bedrock it is younger than the Ilyirak Gravel. surface on which the Chariot Beach gravel of Sangamon age was deposited lies less than 5 feet QUATERNARY DEPOSITS above the present grade of Ogotoruk Creek where it STREAM-TERRACE DEPOSITS cuts through the Chariot Gravel. Several levels (and ages) of stream-terrace de posits, clearly related to present streams or their CHARIOT GRAVEL immediate ancestors, are present along the Kukpuk Beach and nearshore marine deposits that repre and Ipewik Rivers and their tributaries, as well as sent a eustatically high sea level, probably during along the shorter streams which drain southward to the Sangamon Interglaciation, occur along low-lying the sea, such as Ogotoruk and Kisimilok Creeks. The areas of the coast, generally within a few hundred deposits consist chiefly of subrounded to subangular feet of the present shoreline. They are represented cobble and pebble gravels with abundant interstrati- near the mouth of Ogotoruk Valley by an old bay- fied (as well as interstitial) sand and silt (fig. 25C). mouth bar, whose top ranges in altitude from 34 to The cobbles and pebbles consist, almost without ex 42 feet, and upon which the Chariot base camp was ception, of rock types that could have been derived built; therefore, the Chariot Gravel is here named from the bedrock formations of the map area, up for these deposits. The character and distribution of stream from the present sites of deposition. these gravels, together with the associated under The thickest and most continuous of the terrace lying marine platform and some of the overlying deposits is one about 30 feet thick that is intermit nonmarine deposits, have been described in detail, tently exposed along the Kukpuk River. In many and their origin and age discussed by Sainsbury and places the upper surface of a deposit, though covered others (1965); related deposits in the Point Hope with tundra vegetation and modified slightly by ice- and Cape Krusenstern areas have been described by generated microrelief features, is little reworked and Moore and Scholl (1961, p. 61-63). Except for the displays the relatively flat characteristic terrace relatively high-standing old bay-mouth bar at the form. On this flat surface, shallow lakes and swamps mouth of Ogotoruk Creek and a small outcrop near and their grass-covered drained basins are common. the mouth of Kuropak Creek, the deposits are ex Exposures of the bedrock surface on which this ter posed only in vertical stream-cut or wave-cut sec race material is deposited are commonly within a tions intermittently along the coast. They are most foot of the low-water level of the present river. The generally thin layers of marine sand and gravel, thickness and relative continuousness of terrace de sandwiched between the wave-planed bedrock sur posits at this level indicate that this entire stretch face below, and a cover of nonmarine deposits, of the river was aggraded to a base level, probably chiefly colluvium, of variable thickness. a stand of sea level, at an altitude about 30 feet above The deposits consist generally of friable well- the present sea level. It seems reasonable to infer, rounded coarse- to fine-pebble gravel (fig. 25D) and therefore, that this river terrace correlates with the interstratified sand. The bay-mouth bar deposit at stand of sea level, about 26 feet above the present the Chariot campsite seems to contain a greater- level, during which beach deposits of Sangamon age than-normal proportion of admixed silt and clay(?) were laid down along the coast (Moore and Scholl, thought to be wind-deposited material that has been 1961, p. 61). mixed with the upper part of the gravel by percolat Although many, generally discontinuous, terrace ing rainwater and seasonal frost action. The deposit surfaces are cut in the bedrock at higher altitudes there is about 25 feet thick; where observed else- UNCONSOLIDATED DEPOSITS 59 where, the deposits range in thickness from a few insulates the underlying material so that the top of inches to about 10 feet, but they could, of course, be the permafrost zone rises above the base of the un thicker in some of the low-lying coastal areas where consolidated material. During the summer season, they are now concealed by younger nonmarine de the upper li/2-2 feet of the deposit thaws and, be posits. cause of the impermeability of the underlying frozen ground, becomes saturated with water. The water- COLLUVIUM saturated thawed zone is then free to move down- The most widespread of the unconsolidated de slope. Movement is chiefly by solifluction, but in a posits is colluvium; it has formed at the base of few places, where the matted cover of tundra is nearly every bedrock rubble slope and extends as broken, it may occur by mudflow and shallow slump. aprons of varying width and thickness onto the No direct evidence for the maximum age of the col gentler slopes below. It is almost invariably covered luvium deposits has been found. Deposits are being with tundra vegetation and is exposed chiefly in formed and moved at the present, and because the stream cutbanks, wave-cut bluffs along the coast, and processes by which they are formed are so intimately relatively sparse frost boils. Commonly, but not in associated with the arctic climate, their age is pre variably, there is a pronounced break in elope be sumed to range from earliest Pleistocene to the tween steeper relatively barren bedrock rubble hill present. sides and the gentle well-vegetated colluvium-covered valley slopes. These slope breaks give the impression LAKE, LAGOON, AND SWAMP DEPOSITS of a multitude of small discontinuous terraces. Soli- Peat and muck, the principal constituents of fluction lobes are abundant in the apronlike deposits, swamp, lagoon, and lake deposits, are common in but where aprons have coalesced to blanket the bot many parts of the low-lying coastal plain, in closed toms of some small valleys, longitudinal ridges or nearly closed colluvium-filled depressions at parallel to the valley axes are common. Ice-wedge higher altitudes (such as the low-gradient effluent polygons and tussocks are extremely rare and seem drainage of Pumaknak Pond) and in the drained to be confined to areas where the surface is nearly thaw-lake basins that are extremely common on the flat and downslope movement has not occurred for terrace deposits of the Kukpuk River; they are some appreciable number of years. The thickest and sporadically distributed across the surface of the best exposed of the colluvium deposits forms a promi Saligvik Gravel. Areas that are wet and swampy nent terrace along the coast of the Telavirak Hills. at present are commonly very grassy in appearance The terrace and its associated colluvium deposits in contrast to most of the adjacent deposits of other have been described in detail by Sainsbury and others sorts. The deposits in better drained terrain are (1965). most easily recognized where they occur in the The colluvium is composed of angular to subangu- drained basins of thaw lakes, which generally have lar fragments of bedrock, generally of coarse pebble distinctive marginal scarps. In areas where the de or smaller size, with variable amounts of frost-ad posits appear to have been relatively well drained mixed sand, silt, and clay of probable aeolian origin for some appreciable number of years, ice-wedge (fig. 25E). Locally, the colluvium includes material polygons are common. Peat and muck are also found derived from preexisting unconsolidated deposits interbedded with many of the older terrace deposits, which have been reworked, both with and without the as well as with colluvium and wind-deposited silt and addition of locally derived fragments of bedrock. The sand. Apparently many small stream channels have deposits are commonly less than 10 feet thick, form been filled with colluvium or flood-plain deposits ing thin continuous blankets over gentle bedrock above which the surface runoff was locally ponded, slopes; but, locally, where the colluvium has filled forming a swampy environment in which peat ac old stream gullies, it may be as much as 20 feet thick. cumulated, in a few places to a thickness of several The coastal-terrace deposit at the foot of the Tela feet. These organic-rich layers are everywhere un virak Hills, where material was apparently supplied derlain by older unconsolidated deposits, and the very rapidly as the sea cliffs of Sangamon age were present lakes, swamps, and lagoons are all floored eroded, is as much as 100 feet thick in some places. and surrounded by older unconsolidated deposits. Colluvium forms at the base of bedrock rubble None within the mapped area lies directly on bed slopes, where it is mixed by frost action with finer rock. Consequently, the deposits are invariably material, both locally derived and deposited by aeo thinner than the older unconsolidated deposits that lian processes. The growth of tundra vegetation surround them. 60 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA

The composition of the deposits ranges from for the very recent flood-plain and beach sediments. nearly pure peat to mud containing a fairly high Some dust is known to blow in Ogotoruk and Saligvik proportion of silt, clay, and sand commonly mixed Valleys at present but not in amounts needed to form with peaty organic material. The silt, clay, and appreciable deposits. The most likely sources for the sand probably include both aeolian detritus and that fine material of the aeolian deposits are the barren, derived from older unconsolidated deposits by wave unvegetated moraines and outwash plains exposed erosion of the banks of the small lakes. The deposits during glacial retreat. Many local low areas in which of Mapsorak Lagoon have been studied in detail by aeolian sand and silt predominate at the surface Moore and Scholl (1961, p. 48-50), and many char have a well-developed tundra mat and deep and well- acteristics of that lagoon are probably shared by the defined ice-wedge polygons that must have been others. Because the processes of peat formation seem stabilized for an appreciable number of years and to be associated with tundra vegetation and (but may be as old as late Wisconsin. The age of these more indirectly) with the arctic climate, the range deposits is, therefore, considered Pleistocene and in age of the peat and muck deposits may well be Recent. nearly the same as that of the colluvium from earliest Pleistocene to the present. Muck is certainly FLOOD-PLAIN DEPOSITS forming today at the bottom of many thaw lakes, Modern flood-plain deposits occur along the Kuk- and peat with a radiocarbon age of 26,000 ± 400 puk and Ipewik Rivers, the lower reaches of a few years (middle Wisconsin) was sampled in the Point of their tributaries, and along a few of the shorter Hope area (Moore and Scholl, 1961, p. 63). streams that drain south to the ocean, such as Ogo toruk and Kisimilok Creeks. The surfaces of the de WIND-DEPOSITED SILT AND SAND posits are generally barren of vegetation, but some Silt and sand of probable aeolian origin covers parts that are awash only during relatively infre much of the low-lying coastal-plain areas, as well as quent (two or less a year) flood stages, sustain some the lower flats and gentle slopes that are abundant in grasses and tundra. Ogotoruk and Saligvik Valleys and the valley of The deposits consist of fluvial gravel, sand, and Kisimilok Creek. In the flat areas the deposits are silt. The gravels are chiefly flat elongated tabular commonly covered with a fairly continuous tundra subrounded to subangular pebbles (showing better mat, and ice-wedge polygons are the dominant micro- rounding in lower reaches of small streams as well as relief forms. On the slopes, grassy tussocks are more along the rivers); large cobbles and boulders are common, and solifluction stripes, perpendicular to rare. The size and shape are probably functions of the hillside contours, are the most prominent form the bedding characteristics and jointing of the well- of microrelief. The difference in surface expression indurated original bedrock. The composition of the reflects the difference in stability of the active layer gravels reflects that of local and upstream sources of (the zone in which summer thaw occurs) between bedrock and, to a much lesser extent, older unconsoli the relatively stable flats and the slopes down which dated deposits. The proportion of matrix sand and gravity tends to induce movement during the sum silt in the gravel is variable; but it is commonly mer period of thaw and water saturation. much greater than might be presumed from the sur The deposits are compact and saturated with face appearance of the exposed gravel bars, and may water or ice; cutbanks are quickly degraded by slump locally make up more than 50 percent of a deposit. and soil flow. Thickness is commonly on the order Apparently, gentle currents of the waning flood of 1 or 2 feet; locally it may be as much as 4 feet, and stage winnow the finer matrix from between the greater thicknesses may have accumulated in a few topmost pebbles of the flood-deposited mixture of places where depressions or gullies as much as 20 feet gravel, sand, and silt. deep could be concealed beneath the unconsolidated In the short streams that drain south to the deposits. Silt and sand most commonly is underlain Chukchi Sea, the flood-plain deposits probably do not by colluvium or other older unconsolidated surficial exceed 10 feet in thickness. The deposits of the large material, but in some places the subjacent material rivers, although thicker than those of the small is residual frost-broken bedrock. streams, probably do not exceed a few tens of feet. Windblown deposits of several ages are probably present, as silt and sand are interbedded with some BEACH DEPOSITS OF THE PRESENT SHORELINE swamp deposits and with colluvium as well as lying Recent gravel beach deposits extend along the en upon all the other unconsolidated deposits except tire coastline, continuously except for a few cliffed GEOLOGIC STRUCTURE 61 headlands along the sea cliffs between Crowbill Point suggest that the regional gradient is more nearly east and Cape Thompson. Beneath the sea cliffs the beach or east-northeast than southeast. All the exposed is too narrow to show on the map (pi. 1), but it is rocks have approximately the same density; there nevertheless present as a nearly continuous strand, fore, the relatively smooth gravity gradient is inter broken by major headlands at Cape Thompson, preted to reflect a gradual eastward thickening of Agate Rock, Artigotrat, and Crowbill Point (pi. 2). the sedimentary rocks overlying a dense layer that A narrow, but continuous beach lies along the foot of either slopes relatively smoothly or is so deeply the coastal bluff at the south side of the Telavirak buried that its irregularities are not expressed. Hills and extends to the wider beaches of the ad In the western half of the area the structure is jacent lowlands of Ogotoruk Valley and the valley of dominated by a north-trending zone of imbricate Kisimilok Creek. Across the low-lying coastal plains thrust faults along which rocks of the Lisburne to the northwest of Agarak Creek and to the south Group have been thrust eastward over Lisburne and east of Kisimilok Creek, beach deposits are continu younger strata. In the eastern half of the area the ous along the smoothly curved shoreline, in many dominant structural features are complex high- places as barrier bars, separating the Chukchi Sea amplitude folds and high-angle faults. from fresh- and brackish-water lagoons. The deposits are generally barren of vegetation, but some sparse THRUST FAULTS OF THE WESTERN PROVINCE grasses may be found on the higher parts of the bar The north-trending zone of thrust faults extends rier bars, which are reached by only a few waves from the Chukchi Sea northward to Cape Lisburne from the highest storms each year. (A. J. Collier, 1906; J. T. Dutro, Jr., E. G. Sable, and The beaches are generally confined to altitudes of A. L. Bowsher, written commun., 1958). Four thrust less than 12 feet, though a few of the barrier bars sheets are present in the western part of the map may be as much as 15 feet above sea level. They are area. The rocks of two of these, the Saligvik and generally less than 40 feet wide where they are pres Ibrulikorak thrust sheets, predominate at the sur ent beneath the precipitous limestone cliffs, but they face. A third, the Angmakrok sheet, is only inter are considerably wider in the low-lying coastal areas mittently exposed along the eastern front of Saligvik where some of the barrier beaches are as much as 300 Ridge beneath the younger Saligvik thrust sheet. feet wide. The beach deposits of this and adjacent The fourth, the Agate Rock thrust sheet, appears to areas have been studied in detail by other investiga be merely a large fault sliver below the Ibrulikorak tors in connection with the Chariot program (Scholl fault. The Saligvik thrust sheet has an exposed width and Sainsbury, 1959; Moore, 1960; Moore and Cole, of more than 4 miles and a maximum thickness of 1960; and Moore and Scholl, 1961). According to 7,000-8,000 feet. The Ibrulikorak thrust sheet is Scholl and Sainsbury (1959, p. 57-59), the deposits slightly more than 8 miles wide at its widest point probably are generally less than 25 feet thick and are on the map, and its thickness ranges from about composed of stratified well-sorted well-rounded 2,000 feet at the coastline to an estimated 3,000 sandy pebble gravels consisting chiefly of fragments feet along the Kukpuk and Ipewik Rivers. of fine-grained graywacke, siltstone, chert, and lime Each of the thrust sheets has moved relatively stone. eastward or southeastward, forming an imbricate pattern as shown in the structure sections (pi. 1). GEOLOGIC STRUCTURE The earliest thrust sheet is bounded at the base by A regional dip to the south or southeast is indi the Angmakrok thrust fault; it was subsequently cated by the exposure of progressively younger units broken by high-angle faults and overridden by the from west to east on the map (pi. 1), even though Saligvik thrust sheet along the Saligvik thrust fault westerly dips are common at surface exposures of (pi. 2B) ; the Saligvik thrust sheet was, in turn, the strata. As shown by the structure sections (pi. folded, faulted, and overridden from the west by a 1), Paleozoic and Mesozoic strata 25,000-30,000 feet still later thrust sheet bounded at its base by the thick are present in the eastern part of the area, but Agate Rock and Ibrulikorak faults (pi. 2A). The they have been eroded off the western part. In addi Akoviknak fault is probably the western tail of the tion to the stratigraphic evidence, gravity data show Ibrulikorak fault (see structure sections, pi. 1) and a generally gradual decrease in simple Bouger could represent the upslope exposure of a zone of anomalies along a northwest to southeast profile detachment that, to the east, broke upsection along across the area (Barnes and Alien, 1961, p. 80-86), progressively more westward fronts in successively and more recent data (Barnes, oral commun., 1962) younger pulses (Campbell, 1961c). In that event, 62 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA movement on the Akoviknak fault would be the sum of the movements of all the west-dipping thrust faults, for each of which the Akoviknak would have been the upslope tail. The eastern overthrusting on the Angmakrok thrust is a minimum of 1 mile (see structure section C-C', pi. 1), and an estimate of 2 or 3 miles would not be unrealistic. The movement on the Saligvik thrust is, at a minimum, 1 mile, but probably it is considerably more. The eastward overthrusting on the Ibrulikorak and Agate Rock faults is at least 2 miles and is possibly more than 5 miles. Thus, a total displacement of 7-10 miles is indicated. The displacement could be somewhat greater, but it seems unlikely that the total overthrust displacement is on the order of several tens of miles because it has not brought into juxtaposition very different lithologic facies of the same forma tions. The Mississippian strata of the Saligvik and Ibrulikorak thrust sheets are generally folded into rather broad synclines and anticlines. The limbs of the structures, though cut by some high-angle faults, most of which have relatively small displacements, have relatively uniform gentle dips. Some axial zones, however, are intensely faulted and folded into tight structures of high amplitude. This is particu larly striking in two synclines in the Saligvik thrust sheet, in which Siksikpuk, Shublik, and, locally, Ogotoruk rocks are infolded. In places these struc tures have been further modified by drag effects as they were overridden by the Ibrulikorak thrust sheet. Drag folds of varying amplitudes are common in the basal strata of the thrust sheets. Chevron forms are strikingly abundant in the zone immediately above the Saligvik thrust fault in the sea-cliff exposures just west of the mouth of Amaktusak Creek (pi. 2B). FIGURE 26. Bedding characteristics and structural fea FOLDING AND FAULTING tures in the Telavirak Formation. Interlaminated mudstone and sandy siltstone showing thickening, OF THE EASTERN PROVINCE attenuation, and fracturing associated with adjust ments to the tightly folded configuration in a minor In contrast to the thrust-faulted province in the anticline (a drag fold on the flank of a larger struc western part of the map area, the eastern part is ture) . The glassy material that surrounds and veins the specimen is plastic in which it was imbedded to dominated by north- to northeast-trending folds and prevent its disintegration during sawing and polish high-angle faults. The folds are generally tight, of ing. high amplitude, and have steep-dipping limbs and tightly crumpled axial areas. Overturned folds are to be zones in the crest and troughs of folds where common, generally with both limbs dipping to the the rocks failed by fracture, locally, rather than by west. Minor folds of several types ard widely vary flexure. ing amplitudes are present on nearly '-ul the limbs of Poor exposures, lack of key beds and marker the folds (fig. 26). The high-angle faults appear to horizons, and the abundance of minor folds having be intimately related to the folds. Axial-plane faults amplitudes larger than the size of the outcrops com and bedding-plane faults are common, and slicken- bine to obscure much of the general structural pic siding is abundant on many bedding planes within ture in the areas underlain by the Ogotoruk, Tela the rock units. Many of the high-angle faults appear virak, Kisimilok, and Fortress Mountain (?) For- GEOLOGIC STRUCTURE 63 mations. The continuous projections of the longer faults shown on the map (pi. 1) are based largely on discontinuities of structure across the inferred fault traces rather than continuous exposure of the faults themselves. The major axial traces are similarly in ferential, and the lines on the map serve more to illustrate the general nature of the folding and fault ing than to show the precise locations of continuous readily recognizable features. Although the ampli tudes of the major folds must be of the order of at least several hundred feet, it is important to note that rocks of the Shublik Formation and older units are not returned to the surface to the east of the east ern flank of Saligvik Ridge by the folding or faulting of the Ogotoruk Formation. Nor are recognizably older rocks returned to the surface by folding or faulting in any of the successively younger map units. Joints, perpendicular or nearly perpendicular to FIGURE 28. Fracture cleavage in mudstone interbedded with sandstone in the bedding, are common in the sandstone beds; which the cleavage is not developed. Telavirak Formation. close-spaced, locally slaty, fracture cleavage is com mon in the mudstone beds. In many outcrops the planes, appears to be related to the differential slip fracture cleavage appears to be an axial-plane cleav of the overlying and underlying sandstone beds (fig. age, dipping steeply to the west. In many outcrops it 28). is parallel or nearly parallel to the bedding, giving The hypothetical thrust fault that forms the con many of the mudstones a shaly aspect. In axial tact between the Kisimilok and Fortress Moun zones and some other structural settings, however, tain (?) Formations may be related to the thrust where the fracture cleavage intersects bedding-plane faults of the western half of the area; however, there partings at oblique angles, the fractured rocks re is no local evidence to suggest a direction or amount semble pencil slates (fig. 27). Where the mudstone of displacement. Owing to the poor exposure, the is rhythmically interbedded with more competent possibility that this contact is an unconformity can sandstone, the close-spaced fracture cleavage, which not be eliminated, but the generally smooth curva may be at angles of as much as 30° to the bedding ture of the contact and the indications that both units are discordant with the contact suggest that it may be an eastward-dipping low-angle (thrust) fault.

AGE AND ORIGIN OF DEFORMATION The thrust faulting of the western province and the folding of the eastern province appear to be contemporaneous and are probably related to the same deforming stresses. This is indicated by the parallelism of the general trends of the folds with the fronts of the thrust sheets, by the absence in the western province limestone and dolomite strata of high-amplitude multiple folds of the type found in the less competent flysch facies beds of the eastern province, and by the absence of such high-amplitude folding of the thrust faults themselves. It seems likely that each of the thrust faults was a planar or FIGURE 27. Mudstone of the Ogotoruk Formation with one thin interbed smoothly curved surface at the time the overlying of sandstone that expresses bedding; shows close-spaced fracture cleavage strata were displaced. The places where the thrust at acute angle to bedding. The straight edge of the scale case is 2 inches long. faults cross the stratigraphic units, therefore, indi- 64 GEOMORPHOLOGY cate that some gentle folding occurred before the to move as coherent sheets, chiefly along the numer overthrusting. But the large areas in which the ous weakly bonded bedding planes at and near its faults follow stratigraphic horizons, and which are base. The underlying mudstone-sandstone unit, be even now only broadly folded, indicate that the ing water saturated, may have served as a lubricated Paleozoic rocks were not thrown into high-amplitude zone along which the overlying coherent sheets could folds along with the Jurassic (?) and Cretaceous slide, possibly aided by abnormal fluid pressures strata. (Hubbert and Rubey, 1959). The relatively incom The youngest bedrock unit exposed in the known petent Jurassic (?) and Cretaceous rocks also tended overthrust sheets is the lower part of the Ogotoruk to move downslope, but they were less confined by Formation. As the Ogotoruk and Telavirak Forma overburden than the more competent rocks below tions form a continuous depositional sequence that (and perhaps they were even buttressed laterally by probably also includes the Kisimilok Formation, the the end of the eastern dip at a basin or synclinal time of deformation indicated is post-Kisimilok. If axis in the vicinity of Cape Seppings). The response the contact between the Kisimilok and Fortress in this eastern province was chiefly by tight folding Mountain (?) Formations is an unconformity, then and high-angle faulting. two periods of fairly high intensity deformation would be indicated. However, the rocks of both units GEOMORPHOLOGY are contorted to about the same degree, and it seems The varied geomorphic features of the area repre more likely that the contact is a fault and that all of sent a long and complex history of erosion and depo the bedrock units now exposed in the area were de sition. Most of it was subaerial and fluvial, but ma posited before a single major period of deformation rine erosion and deposition are represented by many in post-Fortress Mountain (?) time. features at low altitudes along the coast and may Other evidence bearing on the age of deformation have affected higher areas where the evidence is may be adduced from the Utukok-Corwin region to poorly preserved. Two major rivers, the Kukpuk the north, where rocks as high in the section as the and the Ipewik, are superposed across the general Nanushuk Group are evidently involved in thrust structural grain of the area. Their valleys are deeply faulting of the same general structural associations incised into an old upland surface of very low relief. as those in the western part of the Cape Lisburne The upland surface appears to be stepped along a Peninsula (Chapman and Sable, 1960, p. 144). Chap northwest-trending line that generally follows the man and Sable (1960, p. 144) believe these structural northern side of the valley of the Kukpuk River. features to be the result of eastward- and northeast North of the Kukpuk River several north- to northward-directed tangential forces originating west of northwest-trending ridges rise to altitudes in excess the peninsula in the Tigara uplift, which Payne of 1,750 feet. South of the Kukpuk River many ridge (1955) describes as of Tertiary (?) age, probably tops and hilltops show remnants of a low rolling post-Paleocene. surface between altitudes of 500 and 1,000 feet. The deformation of rocks of the Chariot area and The general topographic features of areas below vicinity is herein interpreted to be a response to an 500 feet appear to reflect almost exclusively the dis easterly regional dip formed as a result of uplift in section of the old upland surface by minor streams the vicinity of Point Hope and west of it (the Tigara that follow the general structural grain and are uplift of Payne, 1955). The cross sections (pi. 1) tributary to the Kukpuk River or drain south to the show an average gradient of 7°-10° eastward on the sea. Stream-cut terraces may be observed in the base of the Lisburne Group. The association of east valleys of the Ipewik and Kukpuk Rivers at altitudes erly overthrusting with an easterly regional dip sug as high as 600 feet. Fluvial terrace deposits are gests that the thrusting took place by gravity glid found at lower altitudes along the rivers, and locally, ing (Campbell, 1961c). The folding of the eastern as much as 30 feet of such deposits overlie cut bed province, with its predominance of west-dipping rock surfaces at altitudes as low as a foot above the axial planes, took place at the same time under the present low-water level of the rivers. The prominent same regional stresses. The difference in kinds of strike valleys and ridges appear to have developed as structure between the eastern and western provinces tributaries to the Kukpuk River during its incision. merely reflects the difference in response of rocks of Some of the streams of the strike valleys appear to different competence to components of gravitational have been captured; others seem to be in imminent force in the direction of the regional dip. The rela danger of capture by the shorter steeper south- tively competent rocks of the Lisburne Group tended flowing streams graded to the Chukchi Sea coast. GEOLOGIC HISTORY 65

No glacial moraine or outwash deposits have been into Early Cretaceous time. The apparent discon- found, nor are there any topographic features of formity between the Shublik and Ogotoruk Forma clearly glacial origin. tions does not seem to represent significant subaerial The line of wave-faceted north- and northeast- erosion, for the upper Monotis-bearmg limestone trending ridges that marks the present coastline zone of the Shublik is present wherever the two for seems to have been well established at nearly its mations are in unfaulted contact. Even if the Juras present position by the end of Sangamon time. Wave sic Period is not represented by sedimentary depos erosion on the present coast is actively attacking its, though it seems more likely that it is, there is no bedrock only along the cliffs and headlands west of evidence that it was a period of emergence in this the Chariot site; even above those cliffs there are area. Except for sporadic marine deposition of the steep slopes which probably represent the degraded Pleistocene Gubik Formation in the coastal plain of cliffs of the earlier coastline of Sangamon age. the Utukok-Corwin area (Chapman and Sable, 1960, A detailed description of the many minor land- p. 69, table 2), no significant marine deposits are forms and microrelief features of the area was not known to occur in this region above the top of the attempted. The microrelief features are of types Nanushuk Group, which was assigned by Chapman relatively common in arctic climates, and their gen and Sable (1960, p. 69) to an Early and Late Cre eral origin and development have been described by taceous age. The Corwin Formation, the topmost several workers in other areas (Hopkins and formation of the Nanushuk Group, includes non- Sigafoos, 1951; Washburn, 1950; Sigafoos and Hop- marine facies, suggesting that the Utukok-Corwin kins, 1952; Sharp, 1942). Notably absent are such area was emergent during Late Cretaceous time and prominent features as pingos and elongated oriented intermittently during much of the later part of Early lakes. Cretaceous time. All the bedrock units now exposed in the area were GEOLOGIC HISTORY probably deposited before the deformation that re The sequence of sedimentary rocks represents sulted in the thrust faulting and folding. Some nearly continuous marine conditions from Early Mis- minor folding, probably associated with early phases sissippian through Early (?) Cretaceous time. The of the Tigara uplift, certainly preceded the main unnamed unit of Early and Late Mississippian age episode of thrust-fault displacement. The main de represents chiefly shallow-water marine deposition, formation probably took place in several pulses, as with some intertonguing of possible nearshore non- each thrust sheet was folded and broken by high- marine deposits. A gradual deepening of marine con angle faults before it was overridden by the next ditions started before and continued during deposi higher sheet. Some late, anticlimatic folding is in tion of most of the Nasorak Formation. The upper dicated by the folding and high-angle faulting of the 1,600 feet of the Nasorak probably represents highest of the imbricate thrust sheets, the Ibruli- miogeosynclinal conditions and grades upward to the korak. The age of the major deformation is uncer shallower marine platform associations represented tain, but it is most probably Late Cretaceous or early by deposits of the Kogruk(?) Formation. The ap Tertiary. Payne (1955) suggests that uplift in the parent discontinuousness of the Tupik Formation vicinity of the Lisburne Hills (the Tigara uplift) and the interbedding of facies similar to it within the occurred during a post-Paleocene orogeny; he also underlying Kogruk(?) suggest that most probably indicates strong deformation of the Brooks Range this facies was deposited in disconnected shallow geanticline at that time. basins of the general platform association. The ab The subsequent history of the area appears to be sence of a sequence of recognizable Pennsylvanian chiefly one of erosion which reduced the area of the rocks is not accompanied by any evidence of exten Tigara uplift and adjacent parts of the Arctic Foot sive subaerial erosion, and there is no reason to infer hills physiographic province to a surface of relatively that the area was emergent at that time. However, low relief. The ancestral Kukpuk and Ipewik Rivers the possibility of post-Tupik pre-Siksikpuk erosion established their west-trending drainage either on an cannot be neglected. The thin continuous deposits of erosion surface of such low relief that the bedrock the Siksikpuk and Shublik Formations suggest gen structure and lithology had little effect or possibly on erally long-lived stable marine conditions at some flat-lying younger deposits that have since been depth below wave base through most of the Permian completely eroded off. Certainly by middle Pleisto and Triassic, followed in Jurassic or Cretaceous time cene time the major rivers were draining westward by eugeosynclinal conditions that persisted at least toward what had been the higher parts of the Tigara 66 AREAL GEOLOGY, VICINITY OF CHARIOT SITE, LISBURNE PENINSULA, ALASKA uplift. The development of a westward-moving in stratigraphic nomenclature 1963: U.S. Geol. Survey drainage indicates that a general westerly surface Bull. 1194-A, p. 25-26. slope had formed in an area where the Tigara uplift Campbell, R. H., 1965c, Telavirak Formation, Point Hope area, northwest Alaska, in Cohee, G. V., and West, W. S., had previously established an eastward-dipping re Changes in stratigraphic nomenclature 1963: U.S. Geol. gional structure. This suggests tectonic subsidence Survey Bull. 1194-A, p. 26-28. of the Tigara uplift area in post-Tigara pre-middle 1965d, Kisimilok Formation, Point Hope area, north Pleistocene time. Some of the folding of the Ibru- west Alaska, in Cohee, G. V., and West, W. S., Changes likorak thrust sheet may have occurred in association in stratigraphic nomenclature 1963: U.S. Geol. Survey Bull. 1194-A, p. 28-29. with the westward tilting. The record of Sangamon 1966, Areal geology, in Wilimovsky, N.J., and Wolfe, deposits and pre-Sangamon erosion surfaces on J. N., eds., Environment of the Cape Thompson region, which those deposits lie indicates that most of the Alaska: U.S. Atomic Energy Comm. PNE-481, p. 57-84. modern drainage was well established and many of Chapman, R. M., and Sable, E. G., 1960, Geology of the the smaller streams had cut to very nearly their Utukok-Corwin region, northwestern Alaska; U.S. Geol. present grades before the Sangamon Interglaciation, Survey Prof. Paper 303-C, p. 47-167. and that the major landforms were well outlined by Collier, A. J., 1960, Geology and coal resources of the Cape Lisburne region, Alaska: U.S. Geol. Survey Bull. 278, middle Pleistocene time. 54 p. Dunbar, C. 0., and Rodgers, John, 1957, Principles of stratig REFERENCES CITED raphy: New York, John Wiley & Sons, 356 p. Barnes, D. F., and Alien, R. V., 1961, Preliminary results of Folk, R. L., 1959, Practical petrographic classification of lime gravity measurements between Kotzebue and Point Hope, stones; Am. Assoc. Petroleum Geologists Bull, v. 43, no. Alaska, in Kachadoorian, Reuben, and others, Geologic 1, p. 1-38. investigations in support of Project Chariot, Phase III, Friedman, G. M., 1959, Identification of carbonate minerals in the vicinity of Cape Thompson, northwestern Alaska by staining methods: Jour. Sed. Petrology, v. 29, no. 1, p. preliminary report: U.S. Geol. Survey TEI-779, p. 80- 89-97. 86; prepared on behalf of the U.S. Atomic Energy Goddard, E. N., chm., and others, 1948, Rock-color chart: Comm. Washington, Natl. Research Council (repub. by Geol. Soc. Campbell, R. H., 1960a, Areal geology of the Ogotoruk Creek America, 1951) 6 p. Chariot test site and adjacent areas to the west and Gryo, George, Patton, W. W., Jr., and Payne, T. G., 1951, north, northwestern Alaska, in Kachadoorian, Reuben, Present Cretaceous stratigraphic nomenclature of north and others, Geologic investigations in support of Project ern Alaska: Washington Acad. Sci, Jour,, v. 41, no. 5, p. Chariot in the vicinity of Cape Thompson, northwestern 159-167. Alaska preliminary report: U.S, Geol. Survey TEI-753, Haaf, E. ten, 1959, Properties and occurrence of turbidities, p. 87-41, pis. 2, 3; prepared on behalf of the U-S. Atomic in Symposium Sedimentology of recent and old sedi Energy Comm. ment: Geologic en mijnbouw (NW. ser,), 21E Jaarg., p. 1960b, Generalized stratigraphic section of the Lis- 217-222. burne group in the Point Hope A-2 quadrangle, north Hopkins, D. M., and Sigafooa, R. S.? 1951, Frost action and western Alaska, in Short papers in the geologic sciences: vegetation patterns on Seward Peninsula, Alaska: U.S. U.S. Geol. Survey Prof. Paper 400-B, p. B3S7-B339. Geol. Survey Bull, 974-C, p. 51-101. 1961a, Transfer of geologic data from aerial photo Hubbert, M. K., and Rubey, W. W., 1959, Mechanics of fluid- graphs to topographic maps by direct tracing, in Short filled porous solids and its application to overthrust fault papers in the geologic and hydrologic sciences: U.S. Geol. ing, [Pt.] 1 of Role of fluid pressure in mechanics of over- Survey Prof. Paper 424-C, p. C368-C370. thrust faulting: Geol. Soc. America Bull., v. 70, no. 2, p. 1961b, Areal geologic maping in the Cape Thompson 115-166. area, Alaska, in Kachadoorian, Reuben, and others. Geo Imlay, R. W., 1959, Succession and speciation of the pelecypod logic investigations in support of Project Chariot, Phase Aucella: U.S. Geol. Survey Prof, Paper 314-G, p. 155-169. III, in the vicinity of Cape Thompson, northwestern Kachadoorian, Reuben, 1961, Abstract and general introduc Alaska preliminary report: U.S. Geol. Survey TEI-779, tion, in Kachadoorian, Reuben, and others, Geologic inves p. 28-42, fig. 3, pi. 1; prepared on behalf of the U.S. tigations in support of Project Chariot, Phase III, in the Atomic Energy Comm. vicinty of Cape Thompson, northwestern Alaska pre 1961c, Thrust faults in the southern Lisburne Hills, liminary report: U.S. Geol. Survey TEI-779, p. 1-12; northwest Alaska, in Short papers in the geologic and prepared on behalf of the U.S. Atomic Energy Comm. hydrologic sciences: U.S. Geol. Prof. Paper 424-D, p. Kachadoorian, Reuben, 1966, Geographic setting, in Wili D194-D196. movsky, N. J., and Wolfe, J. N., eds., Environment of the 1965a, Nasorak Formation, Point Hope area, north Cape Thompson region, Alaska: U.S. Atomic Energy west Alaska, in Cohee, G. V., and West, W. S., Changes Comm. PNE-481, p. 45-56. in stratigraphic nomenclature 1963; U.S. Geol. Survey Kachadoorian, Reuben, Campbell, R. H., Sainsbury, C. L., Bull. 1194-A, p. 22-25. and Scholl, D. W., 1959, Geology of the Ogotoruk Creek 1965b, Ogotoruk Formation, Point Hope area, north area, northwestern Alaska; U.S. Geol. Survey TEM-976; west Alaska, in Cohee, G. V., and West, W. S., Changes open-file report, Oct. 14, 1959, 43 p. REFERENCES CITED 67

Keller, A. S., Morris, R. H., and Detterman, R. L., 1961, Geol Payne, T. G., 1955, Mesozoic and Cenozoic tectonic elements ogy of the Shaviovik and Sagavanirktok Rivers region, of Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-84, Alaska: U.S. Geol. Survey Prof. Paper 303-D, p. 169-222. scale 1:5,000,000. Kindle, E. M., 1909, The section at Cape Thompson, Alaska: Sable, E. G., and Dutro, J. T., Jr., 1961, New Devonian and Am. Jour. Sci., ser. 4, v. 28, p. 520-528. Mississippian formations in DeLong Mountains, northern Alaska: Am. Assoc. Petroleum Geologists Bull., v. 45, no. Kuenen, P. H., 1957, Sole markings of graded graywacke 5, p. 585-593. beds: Jour. Geology, v. 65, no. 3, p. 231-258. Sainsbury, C. L., and Campbell, R. H., 1959, Geologic strip Leffingwell, E. de K., 1919, The Canning River region, north map of part of Kukpuk River, northwestern Alaska: U.S. ern Alaska: U.S. Geol. Survey Prof. Paper 109, 251 p. Geol. Survey open-file report, Sept. 17, 1959, 10 p. Sainsbury, C. L., Kachadoorian, Reuben, Campbell, R. H., Moore, G. W., and Cole, J. Y., 1960, Coastal processes in the and Scholl, D. W., 1965, Marine platform of probable vicinity of Cape Thompson, Alaska, in Kachadoorian, Sangamon age, and associated terrace deposits, Cape Reuben, and others, Geologic investigations in support of Thompson area, northwestern Alaska: Arctic, v. 18, no. 4, Project Chariot in the vicinity of Cape Thompson, north p. 230-245. western Alaska preliminary report: U.S. Geol. Survey Scholl, D. W., and Sainsbury, C. L., 1959, Marine geology and TEI-753, p. 41-55; prepared on behalf of the U.S. Atomic bathymetry of the nearshore shelf of the Chukchi Sea, Energy Comm. Ogotoruk Creek area, northwest Alaska: U.S. Geol. Moore, G. W., and Scholl, D. W., 1961, Coastal sedimentation Survey TEI-606, 68 p., prepared on behalf of the U.S. in northwestern Alaska, in Kachadoorian, Reuben, and Atomic Energy Comm.; also U.S. Geol. Survey open-file others, Geologic investigations in support of Project report. Chariot, Phase III, in the vicinity of Cape Thompson, Schrader, F. C., 1902, Geological section of the Rocky Moun northwestern Alaska preliminary report: U.S. Geol. tains in northern Alaska: Geol. Soc. America Bull, v. 13, Survey TEI-779, p. 43-65; prepared on behalf of the U.S. p. 233-252. Atomic Energy Comm. Sharp, R. P., 1942, Soil structures in the St. Elias Range, Patton, W. W., Jr., 1956a, New formation of Jurassic Age, in Yukon Territory: Jour. Geomorphology, v. 5, no. 4, p. Gryc, George, and others, Mesozoic sequence in Colville 274-301. River region, northern Alaska: Am. Assoc. Petroleum Sigafoos, R. S., and Hopkins, D. M., 1952, Soil instability on Geologists Bull., v. 40, no. 2, p. 213-218. slopes in regions of perennially-frozen ground [Alaska]: Natl. Research Council, Highway Research Board Special 1956b, New and redefined formations of Early Creta ceous age, in Gryc, George, and others, Mesozoic sequence Rept. 2, p. 176-192. Smith, P. S., and Mertie, J .B., Jr., 1930, Geology and mineral in Colville River region, northern Alaska: Am. Assoc. Petroleum Geologists Bull., v. 40, no. 2, p. 219-223. resources of northwestern Alaska: U.S. Geol. Survey Bull. 815, 351 p. 1957, A new upper Paleozoic formation, central Washburn, A. L., 1950, Patterned ground: Rev. canadienne Brooks Range, Alaska: U.S. Geol. Survey Prof. Paper geographic, v. 4, no. 3-4, p. 5-59. 303-B, p. 41-45. Williams^ Howel, Turner, F. J., and Gilbert, C. M., 1954, 1959, Geology of the upper Killik-Itkillik region, Petrography an introduction to the study of rocks in Alaska: U.S. Geol. Survey open-file report, Aug. 13, thin section: San Francisco, Calif., W. H. Freeman & Co., 1959, 142 p. 406 p.; repr., 1958.

INDEX

[Italic page numbers indicate major references]

Page Page Chukchi Sea _.___. -1, 60, 61,64 Fistulipora sp ._.____.__.____ 9 Page Cleiothyridina obmaxima ______Flood-plain deposits ______60 Acknowledgments _____...______1 sp ______..__,. Folds: Agarak Creek ______._.____.._ 5,61 Cloud, P. E., Jr., quoted. - 26 broad synclines and anticlines 62 Agate Rock ....._...._ .19, 22, 23,61 Collier, A. J., cited ______..______.._.__ 61 chevron ______.____ 62 Agate Rock thrust sheet ..._ _ 61 Colville Group, nonmarine beds ______30 drag _ _ 62 Akoviknak fault _. _._ ._ ._ 61,62 Colville River region...... ___ ..__.__ 28 high amplitude ______62,63 Alapah Limestone of Brooks Range . 14,18 overturned _____.._____- 62 Algal impressions __ _. _._.______Colluvium ______.___.,__. _..______4,59 Foraminifera ______-__ 9 Alizarine red S solution, stain used to de Composita sp - .__.. . ______8 Corals ______.______Fortress Mountain Formation. ___ _ 27, 28, 30 termine calcite and dolomite 8,13 colonial ______.______18 Fortress Mountain (?) Formation ____ 4,27 proportions ...______.______.._. 6 horn ___.______9, 14,18 contact with Kisimilok Formation 28, 63,64 Alolukrak ..__...... ______...... _._.. .. _____ 1 lenticular heads ____.______13 deposition from turbidity currents- 29 Amphiscapha sp ______._...______20 lithostrotionoid ..._.._._____...._ 14, 18 description __.______S8 Amplexizaphrentis sp ._.______8 Zaphrentoid _ _ ___.._ _.____. 5,9 topography ______29 Angayukuk Creek _-_-_ _.______.. 5 Corwin Formation _.______65 Fossil collections ______.__ 6, 8, 20, 26, 28 Angmakrok thrust fault ______61,62 Cretaceous rocks __.______S7, 64 Fossils, Kisimilok Formation ______27 Angmakrok thrust sheet _ .______.______61 Crinoid columnals ______._____.___?, 9, 15,18 Kogruk(?) Formation ____ _ 18 Archimedes sp _____ -.______9 Crowbill Point ._.... ____ .__.3, 4, 14, 19,61 Lisburne Group ______8,9 Arctic Foothills province ______.______65 Cyathoclisia sp _._.___... _ _ Nasorak Formation ______7, 8, 13,14 Artigotrat .....____.______61 Cystodictya sp ._- __ __._ __.___ _.__...____ Ogotoruk Formation ______24 Aucella ______..__.__ _._.._.______.___..__ 28 sedimentary rocks undivided______6 Avonia sp ___...__...___._.__..______Shublik Formation ______20 20 B Deformation, age _._____..._.___ 64, 65 Siksikpuk Formation ______. Tupik Formation __..______. 18,19 Barnes, D. F., cited _..._____.._..__ 61 age and origin _ __....______68 DeLong Mountains __.______._.._. 6, 7, 14, 18 Telavirak Formation _____._____ 26 Barrier bars .______.______61 Fracture cleavage in mudstone _.______Beach deposits, present shoreline ______60 Dictyoclostus sp ______8 Bembexia inumbUicata ....______.____..__ 9 Dimegelasma sp - ___.______. . __... 8 Bentonitic(?) clay, Shublik Formation. 52 Dip, regional ______..... 61 Blastoid .______...___..___._____. 18 Diphyphylum ingens ______.__.______9 Gastropods ______,19 Bouger anomalies ______._.______... 61 s p __..-.___..______._____.__..___..______....___..-_..... 9 Geologic history -__ - - - 65 Bowsher, A. L., cited ...... ______._._._____.______24,61 Diphystrotion sp ______9 Geologic structure __.___ - 61 Brachiopods ___._..____..______._.______7, 8, 14, 18, 19 Dolomites, classification __.._._____.__._ 5 Geomorphology _... ______64 Braehythyris suborbicvlaris 8 Duncan, H. M., fossil identification ...6, 14, 18, 20 Gigantoproductus ______- - 18 Brooks Range, Alapah Limestone _...._____... 14. 18 quoted _____.______-_-______6, 18, 19 zone ____ 18 geanticline ___._____.____._____ 65 Dutro, J. T., Jr., cited ___..______.____6, 18, 19, 24, 61 Gravels: Siksikpuk and Shublik Formations.___ 19 fossil identification .__..__.____.___ 6, 14, 18, 20 Ilyirak ______55 Bryozoans ___.__..._..___...____,___7, 9, 11, 13, 14, 15. 18 Chariot ______58 Buchia ______.___.______28 E Saligvik ______- . 56 crassicolis _._____..._...______28 Eohinoconchua sp ______.____ 8 Gubik Formation, marine deposition 65 okensis ______28 Echinoderms .___.__....__.._.___.____7, 9, 11, 18 sublaevis _,______28 Endothyroid ____..______..______9, 14 H subokensis _____.__...______...______28 Erosion _.______.______...... ___... 64, 65 Halobia ______. 20 sp ______.___.____.______...______..___. 26,28 Erosion surface, post-Cretaceous ___..__ 55 Buxtonia sp .__.______.._.__,__..______. Hexaphyllia sp __ Eumetria sp _...___.______.___.__.__ 8 Hubbert, M. K., cited __.__. 64

Camarotoechid _.______..______._._. 8 Faberophyllum sp ______-_ __ 9 Canadaphyttum sp , ..____...... ___..._____..___ 8 Ibrulikorak fault ______--- - 61 Cancrinella sp __..._.._..,____.__.______.__.___ 20 Fasciculophyllum sp ______9 Ibrulikorak thrust sheet .. ---6, 61, 62, 66, 66 Caninia .______.___.______._ _ 8 Faults: Ice . -___ 56, 60 sp .. . ______g high-angle ______..___...... 16, 19, 23 Ice-wedge polygons ______57, 59, 60 Caninoid coral __ _._.______.___._ g eastern province _._.__ ___._ 62 Ilikrak Creek ______- 19 Cape Krusenstern area __._____.______... 58 thrust _ _. . .._ _ 29, 63 Ilyirak Creek ____ - . _ - - 65 Cape Lisburne __.___.____ 18, 61 Agate Rock .. . 61, 62 Ilyirak Gravel ______- - 5B Cape Lisburne Peninsula ______.._.. 64 Akoviknak _._...__....__.______61, 62 Imikrak Creek ______-- 19. 20 Cape Thompson ______...3, 4, 5, 6, 7, 61 Angmakrok ______.. .. 61. 62 Intraformational breecia, Kogruk(?) Cape Thompson Member, of Nasorak hypothetical ______...... ______28, 63 Formation ___ 37 Formation ______7, 14 Ibrulikorak . 34, 61, 62 Ipewik River ______._-7, 19, 55, 58, 60, 61, 64 measured sections __...______30, 49 Saligvik _____ ...______.49, 61, 62 drainage of ancestral _ - 65 Carbonized plant fragments...... __.._.__ 5, 9, 25 western province .____..-_.______.___. 61, 63 Chapman, R. M., cited ______64 Fenestetta sp _...______-..__.____ 9 Chariot Gravel __.__ . ._ __ 53 Fenestellid bryozoans _.______9 Chonetes oklahomensis ______8 Fenestrate bryozoan __.______._ 9, 14 Joints in sandstone _ __ - SP , _.. ..__.______Q Fish teeth .___ _.._.______9 Jepes, D. L., fossil identification _ 26, 28 69 70 INDEX

Page Page Page Jurassic or Cretaceous rocks ...... SO Nanushuk Group ...... _._ _.._ __,_.29, 64, 65 Saligvik Ridge ._..______.-___.__ 19, 23, 56, 61, 63 lithologic types ...__ ..______. ss Nasorak Creek _...__ 7, 14 Saligvik thrust fault ______61 measured section ...... _..._..._.._....____ ss Nasorak Formation ._...... _.__.___...__. 3, 4, 6, 7 Saligvik thrust sheet -______61, 62 Jurassic (?) and Cretaceous rocks ...... 64 bedding characteristics ____._____,___..__, 7 Saligvik Valley __.... ___.__._.___ 57, 60 contact with Kogruk Formation ...... 18 Sangamon, erosion prior to ______.._. 65, 66 K deposition from turbidity currents,,.. 13 Sangamon deposits _...______58, 66 Kemegrak Hills . __ ...... 1 description ______...,.__...,.... 7 Sangamon Interglaciation __...______58, 66 Kemegrak Lagoon ...... -.. _ 1 fossils ....__ ...... _...... __.. 7, 8, 13, 14 Schizophoria sp _.______..._ 8 Kiligvak Creek ___._.______._. 57 marine deposition _.__ ._____.___- 65 Scholl, D. W., cited ... _... 58, 60, 61 Killik-Itkillik area ___..._._..__._..______._ 20 measured sections _...... __....,....,_._ SO, 44 Sedimentary breccia, Kogruk (?) Forma Kingak Shale, inferred correlation...... 24 Cape Thompson Member _.______SI, 49 tion ___...______-__ 16, 55 Kisimilok Creek ...... _...... 27, 58, 60,61 lower member _ _...... _. SS, 49 Sedimentary rocks undivided _ 4 Kisimilok Formation ...... _._____.._.__..__. 4 upper member , _ _-. 50, 44 contact with Lisburne Group..______5 contact with Fortress Mountain (?) Niyiklik Creek, tributary of Ogotoruk description _ __.. __ 5 Formation ...... __...... 28, 63,64 Creek ______..._ 26 fossils _. ______6 contact with Telavirak Formation . 26 Noatak sandstone, possible correlative. 6 Mississippian, measured sections .. SS correlation with part of Okpikruak See also Unnamed mudstone-sand- Formation ..._ ...... _._...._ 28 stone-limestone unit. description _____ ... _...._ 27 Ogotoruk Creek ....__....,... 1, 20, 22, 58, 60 Shublik Formation ...._..._._ . 3, 4, 18, 19, 63, 65 fossils .-..-...... __..._...... _...___._._ 27,28 Ogotoruk Formation SO, 4, 27 bentonitic(?) clay ._ __.______52 topography ...... __ 27 contact with Shublik Formation _____ 23, 65 description _.______~____ SO Kogruk Formation _...... 7, 14, 18 contact with Telavirak Formation. 26 folded and faulted relations with Kogruk(?) Formation .._...... 8, 4, 7, 14, 65 description ...__._____.______.__ 22 Siksikpuk Formation .. _...... 19 breccia, intraformational ...______37 fossils .. .. ___.__..__ 24 fossils , __.______20 sedimentary ...... _____..... 16,55 fracture cleavage in mudstone beds .. 63 measured sections ... _ _.__._._____ 49, 51 contact with Nasorak Formation...... 13 X-ray diffraction studies, of days _____ 23 zones _.--.______20 description . .-....__...... ___...... ___. U of phosphorite nodules ______23 Sigrikpak Ridge ._.__._..._ _-_-_ - 25, 27 fossils ...._...__...... _...... ______._.__ 18 Ogotoruk Valley __.__.___.__---- 20, 25, 57, 58, 60 Siksikpuk Formation .._.. 3, 4, 6, 18, 19, 65 high-angle fault contact with Tupik Ogsachak _... _.__.._...... __....__....__ 1 description . ..______19 Formation ..__ .....__...... _. 19 Okpikruak Formation, part of, correla folded and faulted relations with measured section ...... __...... _...... as tion with Kis.milok Formation 28 Shublik Formation ._...._ 19 Kukpuk River..!, 7,14,19, 22, 29, 58, 59, 60, 61,64 Orbiculoid brachiopod ...... _....._...... _ 8 fossils ...... _._- .- _.-_ 20 drainage of ancestral ...... 65 Orthotetes sp ...______...... ______.______8 high-angle fault contact with Tupik Kukpuk River valley ...... 55 Orthotetid ______.... 8 Formation ..._ __..__ __ 19 Kunuk Creek .._...... _._..._____.._.__.... 5 measured sections ______.______51, SS Siphonodendron pauciradiale ...... 9 Payne, T. Gf, cited ._...... _ 64,65 sp _. ,- _,__ ._ __._ .. __ 9 Lagoon deposit ______59 Peat, radiocarbon age _ .__.... . 60 SochkineophyUum sp ______.__ 20 Lake deposit ______...... __....__..___... 59 Pelecypods ______...... 9,20 Solifluction lobes ,___.._._.__.______, 59 Lakes, thaw ...... _...... _____._.._.. 57,59 Pennsylvanian Period, absence oj! fossilif- Spirifer ...... ,.,...... ______8 Lebenspuren ...... __.__._ 26,28 erous strata ______-_ _ ___ 19 arkansanut .___...,, _ ,__._ ... 8 Leiorynchus carboniferum __ _._...__._ _._ 8 Pentremites sp ...______.. _..._ 9 increbescens . .. ,...... _.._-___ 8 Liardiphyllum sp __._..__.___....._.._..___. 9 Permafrost gone _.._.__ ._._.._. 59 keokuk - - ,_-_._....- _. .__ . 8 Limestones, classification ._._...... _... 5 Permian rocks ______.______...... 19 sp __ ... . _._.__ __.____-..-- 8 Lingul.a sp ...._..__._....._..._..___....__._ 8 measured east section _ __.__ 51 Spiriferoid - . .- ______8 Linoproductoid brachiopod ....._...... 20 measured west section _ . 49 Spirigerella sp . .______20 Linoproductus sp ..___...._..__..._.__.._....__..___._ 8,20 Petrographic methods and terminology 5 Sgnamularia sp .___...... 20 Lisburne Group ....._.__...... ___ |, 6, 7, 18, 23, 61,64 Phosphorite nodules ______- ______22, 23,54 Stenoporoid bryozoans ______.- 9 contact with sedimentary rocks Plant fragments ... ______5,6,9 Straparottus (Euom-phalus) alaskensis__... 20 undivided ...-...... _____.. 5 Platyceras sp .______._ .__.______. 9 (Euomphalus) sp .______. _ . 20 fossils .....___...... ___....__..... 8,9 Plicatifera sp __ ___..__. ._____ 20 Stratigraphic methods and terminology.. 4, 5 measured sections .. ._..._...... ____ SO, 34 Point Hqpe area ...... -.. .. 58,64 Stratigraphy __. ...__...... , S Lithostrotionetta sp. 1...... _.....__.__._. 9 Point Hope quadrangles ______1 summary table _ _. ______4 sp. 2 9 Previous geologic investigations .__...... 1,3 See also individual formations. sp .._ ..... Productoid . ._ .. .. __ ...... _.._ 8 Stream-terrace deposits ._.. ... __ 58 Loxonema sp ...... _.___...... _...... _...... ___ Pumaknak Pond ______...... _..... 59 Swamp deposit ...... _ . ______59 M Punctospirifer sp .....______._.. a Syringoperoid ___._. _ _ .__,- _____.._- 9 Mapsorak Lagoon, deposits of ...... _...... 60 Pusigrak Lagoon ... .._...._. _.. ,._.. 1 Syringopora, sp ...... ^,.-.....-...... 9 Marine deposition, Early Mississippian Pyritized fossils ...... __.._..__....__.. 31,49 Syringothris sp . ,,__ . . 8 through Early (?) Cretaceous...... 65 Martinia sp -...... _...... _...... ___._... 8 Q MartiniQysis sp __..______20 Quadratia sp __.._._ _. Tachylasma ______...... = .______6 Measured bedrock sections ...... _.__.._._. go Quaternary deposits Tailleur, I. L., cited _ _ 6 ftfiehelinia sp .._...... ___ .__.._..__...... ___.__....._. 9 Telavirak Formation ...... 4, 20, SS, 27 MJerite ...... _. ... 5,11 contact with Kisimilok Formation. 26 dolomitjged ...... _...... 15 Relief ...._...... 64 contact with Ogotoruk Formation-.,.. 26 MJssissippJap rocks, ....._ ... _____.... 5 Rhabdomegon sp __ 9 description __ ___.-..._, _,__ SS measured sections, eapt _...... ___ 34 Rubey, W. W., cited ... 64 fossils __..__ .... -.----_____ 26 sedimentary roekg undivided ...... SS Rynefconelloid ______-_ 8 measured partial section, Niyiklik SO Creek __ _..______..._ 84 Monotis ______.__. 20 Telavirak Hills ...., .--_ __-__ 59, 61 Mopre, G. W., cited 58.6Q Sable, I. G., cited __,_.______24, 61, 64 Terebratuloid ______- ___ 8 Mu(jk -.....-...... ___._.... 60 Sajjjsbury, C. L-, cited 61 Terrace deposits, fluvial -___ - . 64 Saljyvik Creek 57 Terraces, stream-cut ______64 Saligvik Gravel _ 56 Tertiary or Quaternary deposits, gravels 55 Creek ______..... 7______.....^.... B, 6, 18 age and orjgin 57 Thrust sheet, Ibrulikorak ______6, 61, 65, 66 fpssil collections ... ______6, description ....___ 57 Saligvik __-___-,~_-----_--- 61, 62 INDEX 71

Page Page Page Thrust sheets ____. ___..__.____..._.. 61 Tupik Formation Continued W late folding and faulting .._._.._...... 65 high-angle fault contact, with Sik- Wachsmuth Limestone _.._._._.._.___ 14 Tigara uplift ...... 64, 65 sikpuk Formation ...... _ 19 Western province, folding ______62 Tigara uplift area, tectonic subsidence .... 66 measured section ._._ ...___.____ 34 thrust f ults _ 61 Tiglukpuk Formation .....__._._._..______20 Tussocks .._.._. ..______._.._...______..___.._ 59, 60 , , , . -- - _. , ... Wind-deposited silt and sand ..______60 Topography ______64 badlands .______67 »T Trepostomatous bryozoans ...... _._..__.. 9 y Triassic rocks __...._._....______.._ __ 19 Ufimia ._._.______._._.__.._.. ._~ 6 measured east section __.____..______._ 51 Unconsolidated deposits ._._____... 3, 4, 55 Yarmouth Interglaciation ._____._....._.._ 67 measured west section .___._...______. 49 types .__.__.__..___ _.._...... __ _ , , .. ,_ See also individual units. Tundra vegetation __.____._.....__.___.._____ 67, 60 Unnamed mudstone-sandstone-limestone Tupik Formation ._____._._.._..._ 3, 4, 7, 18, 65 unit ______3, 5, S3, 65 description ______18 See ~£o "Sedimentarj^ "rock7""^ndi^ "* " Zaphrentites ...... ______9 fossils __.______.._..______18, 19 vided. SP ------9 high-angle fault contact, with Ko- Utukok-Corwin region ____.__...... _.. 29, 64, 65 Zaphrentoid corals .____.. _ . 6, 9 gruk(?) Formation __._.__.__ 19 Utukok Formation ______.._..______._ .6,14 Zaphriphyllum sp __ ._... .._. ..._..... 9

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