Accomplish Me Cover Photograph South Sawyer Glacier in Southeastern Alaska

Accomplish me Cover photograph South Sawyer Glacier in southeastern Alaska. View southeast from head of Tracy Arm. The United States Geological Survey in Alaska: Accomplishments during 1977

Kathleen AA. Johnson, Editor

GEOLOGICAL SURVEY CIRCULAR 772-B

1978 United States Department of the Interior CECIL D. ANDRUS, Secretary

Geological Survey H. William Menard, Director

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, VA 22202 CONTENTS

Page Abstract. ______Bl Northern Alaska Continued Summary of important results ______! Organic geochemistry of rocks from three Introduction. ______! NPRA wells, by Leslie B. Magoon and Statewide projects ______! George E. Claypool ______B25 Mineral resources of Alaska, by Edward H. Release of NPRA (NPR-4) data, by Robert D. Cobb ______1 Carter ______26 Landsat color mosaic of Alaska, by Nairn R. D. Fossil reconnaissance study, eastern NPRA, Albert, Wm. Clinton Steele, and James R. by Charles A. Repenning______27 LeCompte ______! Reconnaissance snow survey of NPRA, April Landsat data interpretation of various AM- 1977, by Charles E. Sloan, Dennis Trabant, RAP quadrangles, Alaska by Nairn R. D. Al and William Glude ______28 bert, Wm. Clinton Steele and James R. Hydrologic reconnaissance of lakes in NPRA, LeCompte ______4 1977, by Charles E. Sloan and Richard F. Geochemical exploration studies in Alaska, by Snyder ______28 G. C. Curtin, T. D. Hessin, R. M. O'Leary, E. Streamflow in NPRA, 1977, by S. H. Jones _ _ 29 F. Cooley, G. W. Day, and R. B. Tripp _ _ _ 5 Development and operation of gas fields in the Streamflow and channel erosion investigations South Barrow area, by Robert D. Carter and along the TAPS route, by J. M. Childers, D. Robert J. Lantz ______29 Kernodle, and R. Loeffler ______6 A simple target model for offshore permafrost Regional appraisal of Alaska's ground-water at Prudhoe Bay, by Arthur H. Lachenbruch resources, by Chester Zenone and G. S. An- and B. Vaughn Marshall ______30 derson ______? Geophysical profiles through the Shaviovik- Northern Alaska ______? Echooka River region, by Dennis Giovan- The Arrigetch Peaks and Mount Igikpak plu- netti and K. J. Bird ______32 tons, Survey Pass quadrangle, Alaska, by S. Hydrology of arctic Alaska, by J. M. Childers, W. Nelson and Donald Grybeck ______? D. Kernodle, and R. Loeffler ______33 Potential strata-bound lead-zinc mineraliza tion, Philip Smith Mountains quadrangle, East-central Alaska ______34 Alaska, by J. T. Dutro, Jr ______9 Late Paleozoic radiolarians and conodonts Granitic clasts from Lower Cretaceous con found in chert of Big Delta quadrangle, by glomerate in the northwestern Brooks H. L. Foster, D. L. Jones, T. E. C. Keith, Range, by C. F. Mayfield, I. L. Tailleur, C. Bruce Wardlaw, and F. R. Weber ______34 G. Mull, and M. L. Silberman ______!! Late Cenozoic stratigraphy of the south-cen Cretaceous Nanushuk Group, North Slope, tral Brooks Range, by Thomas D. Hamilton _ 36 Alaska, by Thomas S. Ahlbrandt and A. Geohydrology of the Fairbanks-North Star Curtis Huffman ______13 Borough, by G. L. Nelson _ _ _ ;______38 Geologic investigations of metallic mineral re Geohydrology of the Delta-Clearwater area, by sources of southern NPRA, by Michael G. L. Nelson ______38 Churkin, Jr., Carl Huie, C. F. Mayfield, and Warren J. Nokleberg ______15 Stratiform zinc-lead mineralization, Drench- West-central Alaska ______38 water Creek area, Howard Pass quadrangle, Juxtaposed continental and oceanic-island arc western Brooks Range, Alaska, by Warren J. terranes in the Medfra quadrangle, west- Nokleberg and Gary R. Winkler ______17 central Alaska, by William W. Patton, Jr _ 38 Surficial geology of the foothills and moun Preliminary summary of the geology in the tains of NPRA, by Warren Yeend _ ___ 19 northwest part of the Ruby quadrangle, by Coastal plain deposits of NPRA, by John R. Robert M. Chapman and William W. Pat- Williams, L. David Carter, and Warren E. ton, Jr ______39 Yeend______20 Landslides near Melozitna River canyon, by Studies of proposed airfields at the Inigok and Robert M. Chapman and William W. Pat- Tunalik well sites, NPRA, by Reuben Ka- ton, Jr ______41 chadoorian, F. E. Crory, and D. L. Berg _ _ 22 An occurrence of parsonite, a secondary urani Granite on the Barrow arch, northeast NPRA, um mineral, in alaskite of the Wheeler Creek by K. J. Bird, C. L. Connor, I. L. Tailleur, M. pluton, by Thomas P. Miller and Bruce R. L. Silberman, and J. L. Christie ______24 Johnson ______42

III West-central Alaska Continued Southern Alaska Continued Tin-granites of Seward Peninsula, by Travis Analysis of remotely sensed data for use in Hudson, Fred Barker, and Joseph Arth _ _ B44 evaluating onshore impacts of offshore pe troleum development at Kenai, Alaska, by Upper Triassic radiolarian chert from the Ko- Harry F. Lins, Jr ______B76 buk volcanic sequence in the southern Application of remotely sensed data for Brooks Range, by George Plafker, Travis ground-water analysis near Denali, Alaska, Hudson, and D. L. Jones ______45 by James K. Richard ______78 Kigluaik and Bendeleben faults, Seward Pen Computer enhancement of Landsat digital insula, by Travis Hudson and George Plaf data for mapping material-related geomor- ker ______47 phic features near Denali, Alaska, by Cyn Preliminary investigations of coal outcrops thia A. Sheean______79 near Farewell, Alaska, by Ernest G. Sloan, Classification of vegetation in the Denali, Gerald B. Shearer, James Eason, and Carl Alaska area with digital Landsat data, by Almquist ______50 Wayne G. Rohde, Wayne A. Miller, and Charles A. Nelson ______80 Southwestern Alaska ______50 Water resources studies in the Anchorage area, New geologic map of the Goodnews-Hagemeis- by Chester Zenone ______81 ter Island quadrangles region, Alaska, by J. Southeastern Alaska ______82 M. Hoare and W. L. Coonrad ______50 New geologic map of Ketchikan and Prince Lawsonite in southwest Alaska, by J. M. Hoare Rupert quadrangles, southeastern Alaska, and W. L. Coonrad ______55 by Henry C. Berg, Raymond L. Elliott, Upper Jurassic and Cretaceous rocks of the James G. Smith, and Richard D. Koch _ _ _ _ 82 Kamishak Hills-Douglas River area, lower Chemistry of Quartz Hill intrusive rocks, Ket Cook Inlet, by Leslie B. Magoon, Robert M. chikan quadrangle, by Travis Hudson, Ray Egbert, and George Petering ______57 mond L. Elliott, and James G. Smith _ _ _ _ 83 Petrography of the Upper Jurassic through Minor-metal content of Cretaceous greenstone Oligocene sandstones in the Cape Douglas- near Juneau, Alaska, by Arthur B. Ford and Kamishak Hills area, lower Cook Inlet, by David A. Brew ______85 Stephen M. Lankford and Leslie B. Magoon _ 60 Intrusive rocks in the Fairweather Range, Gla Interpretation of depositional environments in cier Bay National Monument, Alaska, by the Chignik Formation, Alaska Peninsula, David A. Brew, Bruce R. Johnson, Arthur B. by Robert L. Detterman ______62 Ford, and Robert P. Morrell______88 New ages on intrusive rocks and altered zones Tarr Inlet suture zone, Glacier Bay National on the Alaska Peninsula, by F. H. Wilson, R. Monument, by David A. Brew and Robert P. L. Detterman, and M. L. Silberman _____ 63 Morrell ______90 Tertiary sedimentary rocks of the Alaska Pen Offshore Alaska ______92 insula between Pavlof Bay and False Pass; Heat flow and organic gas measurements from their geology and petroleum potential, by the Aleutian Basin, Bering Sea, by Alan K. Hugh McLean ______65 Cooper ______92 Environmental geologic studies in northern Southern Alaska ______65 Bering Sea, by Devin R. Thor and Hans Nel New potassium-argon data on the age of min son ______94 eralization and metamorphism in the Wil Navarin basin, northwest Bering Sea shelf, by low Creek mining district, southern Mike Marlow ______96 Talkeetna Mountains, Alaska, by Miles L. Seismicity near Icy Bay, Alaska and in the Silberman, Bela Csejtey, Jr., James G. eastern Gulf of Alaska, by Christopher Smith, Marvin A. Lanphere, and Frederick Stephens ______96 H. Wilson ______65 Outcrop samples from the Continental Slope Tectonic significance of newly discovered low in the eastern Gulf of Alaska, by George er Paleozoic strata in the upper Chulitna Plafker, Gary R. Winkler, Susan J. Hunt, Valley, south-central Alaska, by Bela Csej Susan Bartsch-Winkler, Warren L. Coon tey, Jr., Willis H. Nelson, David L. Jones, rad, and Paula Quinterno ______97 and Norman J. Silberling ______69 Reports on Alaska published by the U.S. Geologi Framework grain mineralogy and provenance cal Survey in 1977 ______102 of sandstone from the Arkose Ridge and Revisions to l:l,000,000-scale map of Alaska _ _ _ 110 Chickaloon Formations, Matanuska Valley, Introduction ______110 by Gary R. Winkler ______70 Goodnews-Hagemeister Island quadrangles Generalized physiography and geology of the region, by J. M. Hoare and W. L. Coonrad _ 112 Beluga coal field and vicinity, south-central Ketchikan and Prince Rupert quadrangles, by Alaska, by Henry R. Schmoll and Lynn A. Henry C. Berg, Raymond L. Elliott, James Yehle ______73 G. Smith, and Richard D. Koch ______114 IV ILLUSTRATIONS

FIGURE 1. Map showing regions of Alaska used in this report ______B2 2. Location map, studies discussed in summary of important results ______3 3. Photograph of surface of coarse-grained gneiss from the Arrigetch Peaks pluton ______8 4. Generalized stratigraphic section, unnamed Upper Devonian formation and Hunt Fork Shale ______10 5. Location map, sampled conglomerate, and potential igneous source areas, northwestern Brooks Range _ 12 6. Generalized stratigraphic sequence, Cretaceous Nanushuk Group ______14 7. Location map, mineral resource assessment studies, southern NPRA ______15 8. Schematic section across Brooks Range and North Slope ______16 9. Generalized columnar section, lowest structural sequence, southern NPRA ______16 10. Geologic map, Drenchwater thrust plate ______18 11. Map of surficial deposits, Arctic coastal plain, NPRA ______20 12. Map of NPRA showing locations of Inigok and Tunalik well sites ______22 13. Lithology and wireline log response of granite in East Teshekpuk No. 1 ______24 14. Photograph showing snow density sampling, NPRA ______28 15. Schematic representation of sub-sea temperatures following submergence of a region underlain by ice-rich permafrost ______31 16. Gravity and magnetic profiles across northeastern Brooks Range front ______32 17. Photograph showing water quality sampling at Bogie Creek ______34 18. Geologic map, northeastern Big Delta quadrangle ______35 19. Sketch map, selected bluff exposures, Koyukuk and Chandalar drainage basins ______36 20. Map of Medfra quadrangle, showing Nixon Fork and Innoko terranes ______39 21. Preliminary geologic map of northwest part of Ruby quadrangle ______40 22. Photograph of headword portion of a large landslide north of Melozitna River canyon ______43 23. Generalized geologic map, western Purcell Mountains ______44 24. Location map, Seward Peninsula tin-granites ______44 25. Location map, Upper Triassic radiolarian chert localities and Carboniferous megafossils within Kobuk ophiolite belt ______46 26. Photomicrograph of Pseudoheliodiscus sp ______47 27. Location map, Kigluaik and Benedeleben faults, Seward Peninsula ______48 28. Generalized geologic map, Goodnews and Hagemeister Island quadrangles ______53 29. Description of map units, Goodnews and Hagemeister Island quadrangles ______54 30. Geologic sketch map, lawsonite and blue amphibole localities and possible suture zone, southwestern Alaska ______56 31. Geologic map, Kamishak Hills-Douglas River area ______58 32. Q-F-L diagrams, Upper Jurassic through Oligocene sandstones, Cape Douglas-Kamishak Hills area _ _ _ 61 33. Location map, potassium argon studies in Chignik and Sutwik Islands quadrangles ______64 34. Geologic map of Alaska Peninsula between Pavlof Bay and False Pass ______66 35. Geologic map, Willow Creek area, southern Talkeetna Mountains ______68 36. Generalized geologic map upper Chulitna Valley area, south-central Alaska ______70 37. Framework grain compositions of 28 point-counted sandstones from the Matanuska Valley ______71 38. Preliminary map showing generalized physiography and geology of the Beluga coal field and vicinity _ 74 39. Urban and developing land, Kenai test site ______77 40. Generalized geologic map, Ketchikan and Prince Rupert quadrangles ______84 41. Plot of normative Q-Or-Ab+An ratios, Quartz Hill intrusive rocks, Ketchikan quadrangle ______86 42. Sketch map, western Glacier Bay National Monument ______89 43. Bathymetric map, Aleutian Basin, Bering Sea ______93 44. Map showing potentially hazardous regions, northern Bering Sea ______94 45. Map showing epicenters and first-motion plots of earthquakes beneath Icy Bay between September 1974 and September 1976 ______96 46. Map showing locations of outcrop dredge samples, eastern Gulf of Alaska ______98 47. Generalized geologic map, Goodnews and Hagemeister Island quadrangles ______113 48. Generalized geologic map, Ketchikan and Prince Rupert quadrangles ______114 TABLES Page TABLE 1. Stratigraphic succession, Koyukuk and Chandalar drainage systems, south-central Brooks Range ______B36 2. Delayed neutron determinations of uranium and thorium in selected grab samples, Wheeler Creek pluton _ 43 3. Potassium-argon ages of granitic rocks, schist, and mineralization, southern Talkeetna Mountains _ _ _ 67 4. Average minor-metal content of metavolcanic rocks near Juneau ______87 5. Summary of data for outcrop samples recovered in dredge hauls, eastern Gulf of Alaska ______100 V The United States Geological Survey in Alaska Accomplishments during 1977

Kathleen M. Johnson, Editor

ABSTRACT 1977); and an open-filed list of recent Federal and State reports on the geology and mineral re United States Geological Survey projects in Alaska study a wide range of topics of economic and scientific interest. sources of Alaska, indexed by quadrangle (Cobb, Work done in 1977 includes contributions to economic geol 1977a). Current bibliographic and mineral-re ogy, regional geology, stratigraphy, environmental geology, source reference materials were made available engineering geology, hydrology, and marine geology. Many to the Alaskan Branch information processing maps and reports covering various aspects of the geology and project for entry into computerized storage and mineral and water resources of the State were published. In addition, the published l:l,000,000-scale map of the State retrieval banks. has been revised in two areas. REFERENCES CITED SUMMARY OF IMPORTANT RESULTS Cobb, E. H., 1977a, Selected Geological Survey, U.S. Bureau of Mines, and Alaska Division of Geological and Geo INTRODUCTION physical Surveys reports and maps on Alaska released during 1976, indexed by quadrangle: U.S. Geol. Survey Significant new scientific and economic geo Open-File Report 77-177,115 p. logic information has resulted from many topical 1977b, Summary of references to mineral occurrences and field investigations of the Geological Survey (otherthan mineral fuels and construction materials) in the Tanana quadrangle, Alaska: U.S. Geol. Survey in Alaska during the past year. Discussions of the Open-File Report 77-432,110 p. findings or, in some instances, narratives of the 1977c, Summary of references to mineral occurrences course of the investigations are grouped in eight (other than mineral fuels and construction materials) in subdivisions corresponding to the six major the Eagle quadrangle, Alaska: U.S. Geol. Survey Open- onshore geographic regions (fig. 1), the off File Report 77-845,122 p. Cobb, E. H., Dusel-Bacon, Cynthia, MacKevett, E. M., Jr., shore projects, and projects that are statewide in and Berg, H. C., 1977, Map showing distribution of min scope. Locations of the study areas are shown in eral deposits (other than organic fuels and construction figure 2. materials) in Alaska: U.S. Geol. Survey Open-File Re port 77-496, 45 p., 1 map, scale 1:2,500,000. STATEWIDE PROJECTS Hoare, J. M., and Cobb, E. H., 1977, Mineral occurrences (other than mineral fuels and construction materials) in Mineral resources of Alaska the Bethel, Goodnews, and Russian Mission quadran By Edward H. Cobb gles, Alaska: U.S. Geol. Survey Open-File Report 77- 156, 98 p.

Products of this office project during 1977 in Landsat color mosaic of Alaska cluded an open-filed map showing the distribu By Nairn R. D. Albert, Wm. Clinton Steele, and tion of mineral deposits (other than organic fuels James R. LeCompte and construction materials) in Alaska (scale 1:2,500,000) (Cobb and others, 1977); open-filed A controlled l:l,000,000-scale Landsat false- summaries of references to mineral occurrences color mosaic of Alaska is now available. The five (other than organic fuels and construction mate sheets of the mosaic cover all of Alaska except for rials) in five quadrangles (scale 1:250,000) in southeastern Alaska, which will be available in Alaska (Cobb, 1977b, 1977c; Hoare and Cobb, the near future, Saint Lawrence Island, the Aleu- B-l 174° 171° 168° 165° 162° 159° 153" 150° 147° 144° 141°

170° 168° 166" 164° 162° 160

FIGURE 1. Regions of Alaska used in this report. .____. .

TOPOGRAPHIC DIVISION ^ ROOKY iioriruiit MAPPING rnmvK DKNVER, COLORADO ALASKA

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FIGURE 2. Location of studies discussed in summary of important results. Numbers keyed to project discussions in text. tian Islands, and several other small islands. The faults in the Chandalar quadrangle are evident mosaic is on a Lambert conformal projection on Landsat imagery, and many of these can be with control established by Topographic Divi extended. One of these fault extensions passes sion, Photogrammetry Branch. All scenes were through the two known porphyry copper depos printed on Cibachrome by a commercial scienti its and probably warrants further study. fic photographic laboratory. Although the scenes There are three groups of lineaments in the were taken at different times of the year (spring Talkeetna quadrangle. The first is similar to lin through fall) and colors vary considerably, we at eament patterns observed in other quadrangles tempted to match colors photographically be in Alaska (Albert, 1975; Albert and Steele, 1976a, tween scenes as much as possible. Details on b) that correspond to a planetary or worldwide coverage, cost, and ordering each of the five fracture pattern. The second group is related to sheets can be obtained from the EROS Data the Denali fault system, and the third is probably Center, Sioux Falls, South Dakota. related to local and regional tectonic events not directly associated with the Denali fault. Much Landsat data interpretation of various AMRAP of our work in the Talkeetna quadrangle cor quadrangles, Alaska roborates geologic features and relations postu By Nairn R. D. Albert, Wm. Clinton Steele, and James R. LeCompte lated by the field geologists. Most notable is the identification of several northeast- to east-north The use of Landsat imagery in the Chandalar east-trending lineaments that correspond to the (Albert and others, 1978), Talkeetna (Steele and Yentna mineral belt (Hawley and Clark, 1973) Albert, 1978), Big Delta (N. R. D. Albert, unpub. and correlate with and connect several faults data, 1977), Goodnews-Hagemeister Island mapped by Reed and Nelson (1977). (Steele, 1978), and Ketchikan-Prince Rupert (W. Several major lineaments in the Big Delta C. Steele, unpub. data, 1977) quadrangles, as quadrangle correspond to faults that were sug part of the Alaska Mineral Resource Assessment gested previously by field geologists but have re Program (AMRAP), provides unique geologic mained unmapped because of the absence of and structural information relevant to mineral ground evidence (H. L. Foster and F. R. Weber, resource assessment. Interpretative techniques oral commun., 1977). Recent field investigations include visual analysis of a black and white, sin at several areas selected on the basis of Landsat gle-band Landsat mosaic of Alaska and various data support the existence of these faults and in computer-generated color and black and white dicate that they may be considerably longer than products (most of which are available from the was thought. EROS Data Center, Sioux Falls, South Dakota). In the Goodnews and Hagemeister Island In the Chandalar quadrangle, several linear quadrangles region, approximately half of the features correspond to geology (Brosge and lineaments are related to faults mapped by Reiser, 1964), geophysics (Cady, 1978; Barnes, Hoare and Coonrad (1978). Because the loca 1976), and mineralization (DeYoung, 1978). One tions of many of the faults mapped in this area lineament and two interlineament zones seem to are uncertain, the Landsat images may show the form boundaries for numerous rock types. Most actual fault traces more accurately than do ear greenschist facies units are confined to an area lier maps. The lineaments also indicate that between all three features; many bedded sedi many faults are probably substantially longer mentary and lower grade metamorphic rocks are than originally mapped. In addition, because so excluded from this area. In addition, these three many lineaments in the area are related to lineament features are strongly related to geo mapped faults, other lineaments are likely to re physical features and to known mineralization or present previously undetected faults. geochemical anomalies (Marsh and others, Nearly all mapped faults in the Ketchikan and 1978a-e; Marsh and Wiltse, 1978). As a result of Prince Rupert quadrangles (Berg and others, these and other observed relations, we believe 1978) are evident on the Landsat imagery. Most that areas with a high likelihood for significant of the other Landsat-derived lineaments are visi mineralization occur where any two of these lin ble in the field and correspond to fracture sets in eament features intersect. Numerous mapped several areas. B-4 REFERENCES CITED niobium in the Chandalar quadrangle, Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-878-H, 1 sheet, scale 1:250,000 (in press). Albert, N. R. D., 1975, Interpretation of Earth Resources 1978e, Geochemical and generalized geologic map Technology Satellite imagery of the Nabesna quadran showing distribution and abundance of zinc in the gle, Alaska: U.S. Geol. Survey Misc. Field Studies Map Chandalar quadrangle, Alaska: U.S. Geol. Survey Misc. MF-655-J, 2 sheets, scale 1:250,000. Field Studies Map MF-878-E, 1 sheet, scale 1:250,000 Albert, N. R. D., Le Compte, J. R., and Steele, W. C., 1978, (in press). Interpretation of Landsat imagery of the Chandalar Marsh, S. P., and Wiltse, M. A., 1978, Composite geochemi- quadrangle, Alaska: U.S. Geol. Survey Misc. Field Stud cal map showing major alteration zones, and detailed ies Map MF-878-J, 2 sheets, scale 1:250,000 (in press). geologic maps of selected mineral prospects, Chandalar Albert, N. R. D., and Steele, W. C., 1976a, Interpretation of quadrangle, Alaska: U.S. Geol. Survey Misc. Field Stud Landsat imagery of the McCarthy quadrangle, Alaska: ies Map MF-878-1,1 sheet, scale 1:250,000 (in press). U.S. Geol. Survey Misc. Field Studies Map MF-773-N, 3 Reed, B. L., and Nelson, S. M., 1977, Geologic map of the sheets, scale 1:250,000. Talkeetna quadrangle, Alaska: U.S. Geol. Survey Misc. 1976b, Interpretation of Landsat imagery of the Tan- Field Studies Map MF-870-A, 1 sheet, scale 1:250,000 across quadrangle, Alaska: U.S. Geol. Survey Misc. (in press). Field Studies Map MF-767-C, 3 sheets, scale 1:250,000. Steele, W. C., 1978, Interpretation of Landsat imagery of the [Supersedes Open-File Report 76-850.] Goodnews and Hagemeister Island quadrangles region, Barnes, D. F., 1976, Bouguer gravity map of Alaska: U.S. southwestern Alaska: U.S. Geol. Survey Open-File Re Geol. Survey Open-File Report. 76-70, 1 sheet, scale port 78-9-D, 1 sheet, scale 1:250,000 (in press). 1:2,500,000. Steele, W. C., and Albert, N. R. D., 1978, Interpretation of Berg, H. C., Elliott, R. L., Smith, J. G., and Koch, R. D., Landsat imagery of the Talkeetna quadrangle, Alaska: 1978, Geologic map of Ketchikan and Prince Rupert U.S. Geol. Survey Misc. Field Studies Map MF-870-C, 2 quadrangles, Alaska: U.S. Geol. Survey Open-File Re sheets, scale 1:250,000 (in press). port 78-73-A, 1 sheet, scale 1:250,000. Brosge, W. P., and Reiser, H. N., 1964, Geologic map and Geochemical exploration studies in Alaska section of the Chandalar quadrangle, Alaska: U.S. Geol. By G. C. Curtin, T. D. Hessin, R. M. O'Leary, E. F. Survey Misc. Field Geologic Inv. Map 1-375, 1 sheet, Cooley, G. W. Day, and R. B. Tripp scale 1:250,000. Cady, J. W., 1978, Aeromagnetic map and interpretation of the Chandalar quadrangle, Alaska: U.S. Geol. Survey Results of geochemical studies made during Misc. Studies Map MF-878-C, 2 sheets, scale 1:250,000 the 1977 field season and compilations of results (in press). from studies made during the 1976 field season DeYoung, J. H., Jr., 1978, Mineral resources map of the outlined a number of areas of possible new min Chandalar quadrangle, Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-878-B, 1 sheet, scale 1:250,000 eral occurrences. At several localities in the Tal (in press). keetna quadrangle (central Alaska Range), high Hawley, C. C., and Clark, A. L., 1973, Geology and mineral tin, tungsten, and beryllium values occur in deposits of the Chulitna-Yentna mineral belt, Alaska: stream sediments and heavy-mineral concen U.S. Geol. Survey Prof. Paper 758-A, p. A1-A10. trates (Curtin, Karlson, Tripp, and Day, 1978). Hoare, J. M., and Coonrad, W. L., 1978, Geologic map of the Goodnews and Hagemeister Island quadrangles region, These occurrences are associated with granitic southwestern Alaska: U.S. Geol. Survey Open-File Re plutons of the McKinley sequence (Reed and port 78-9-B, 1 sheet, scale 1:250,000. Nelson, 1977) and probably are derived from Marsh, S. P., Detra, D. E., and Smith, C. E., 1978a, Geo- greisen zones similar to one described by Reed chemical and generalized geologic map showing distri and others (1978, table 1, No. 42). In addition, bution and abundance of barium, arsenic, boron, and vanadium in the Chandalar quadrangle, Alaska: U.S. significant amounts of gold were found in heavy- Geol. Survey Misc. Field Studies Map MF-878-G, 1 mineral concentrates in several previously unre- sheet, scale 1:250,000 (in press). ported localities on the south flank of the Alaska 1978b, Geochemical and generalized geologic map Range within the Talkeetna quadrangle (Curtin, showing distribution and abundance of copper, molyb Karlson, O'Leary, Day, and McDanal, 1978). denum, and lead in the Chandalar quadrangle, Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-878-D, 1 These discoveries may outline additional gold sheet, scale 1:250,000 (in press). occurrences similar to those in the Chulitna- 1978c, Geochemical and generalized geologic map Yentna mineral belt on the south flank of the showing distribution and abundance of nickel, cobalt, Alaska Range (Hawley and Clark, 1973). A num lanthanum, and yttrium in the Chandalar quadrangle, ber of possible base-metal occurrences were also Alaska: U.S. Geol. Survey Misc. Field Studies Map MF- 878-F, 1 sheet, scale 1:250,000 (in press). outlined in the west half of the quadrangle (Cur 1978d, Geochemical and generalized geologic map tin, Karlson, O'Leary, Day, and McDougal, showing distribution and abundance of antimony and 1978). Discovery of several previously unre- B-5 ported gold and scheelite occurrences in the Sew- Curtin, G. C., Karlson, R. C., O'Leary, R. M., Day, G. WM and ard quadrangle (Kenai Peninsula) is based on McDougal, C. M., 1978, Geochemical maps showing the distribution and abundance of copper, lead, zinc, and high gold and tungsten values in stream sedi molybdenum in the Talkeena quadrangle, Alaska: U.S. ment and heavy-mineral concentrate samples Geol. Survey Misc. Field Studies Map MF-870-G, 4 (Tripp and Crim, 1978). sheets, scale 1:250,000 (in press). In several areas in the northeastern part of the Curtin, G. C., Karlson, R. C., Tripp, R. B., and Day, G. W., Big Delta quadrangle (east-central Alaska), 1978, Geochemical maps showing the distribution and abundance of tin, tungsten, and beryllium in the Tal heavy-mineral concentrates of stream sediment keetna quadrangle, Alaska: U.S. Geol. Survey Misc. contain anomalous amounts of tin, tungsten, mo Field Studies Map MF-870-F, 3 sheets, scale 1:250,000 lybdenum, lead, zinc, and silver. This metal suite (in press). is associated with granitic plutons and suggests Hawley, C. C., and Clark, A. L., 1973, Geology and mineral possible economic tin occurrences. A similar ele deposits of the Chulitna-Yentna mineral belt, Alaska: U.S. Geol. Survey Prof. Paper 758-A, 10 p. ment correlation exists, to a lesser degree, in the Hessin, T. D., Taufen, P. M., Seward, J. C., Quintana, S. J., southeastern part of the quadrangle. Anomalous Clark, A. L., Grybeck, Donald, Hoare, J. M., and Coon- amounts of copper, lead, zinc, and arsenic were rad, W. L., 1977, Geochemical and generalized geologic detected in heavy-mineral concentrates collected maps showing distribution and abundance of copper, near Cretaceous and Tertiary granitic stocks in lead, zinc, and arsenic in the Goodnews and Hagemeis- ter Island quadrangles, Alaska: U.S. Geol. Survey Open- the northeast part of the Goodnews quadrangle, File Report 77-762-L-O (in press). southwest Alaska (Hessin and others, 1977). In Karlson, R. C., Curtin, G. C., Cooley, E. F., and Garmezy, L., several areas in the western part of Talkeetna 1977. Geochemical maps and results of spectrographic Mountains quadrangle (south-central Alaska), analyses for heavy-mineral concentrates from the west heavy-mineral concentrates contained anoma ern half of the Talkeetna Mountains quadrangle, Alaska: U.S. Geol. Survey Circ. 734, 23 p. (in press). lous amounts of either gold and silver or copper Reed, B. L., and Nelson, S. W., 1977, Geologic map of the and molybdenum (Karlson and others, 1977). Talkeetna quadrangle: U.S. Geol. Survey Misc. Field The anomalies suggest possible previously un Studies Map MF-879-A, 1 sheet, scale 1:250,000 (in discovered metal occurrences in these areas. press). During the 1977 field season, approximately Reed, B. L., Nelson, S. W., Curtin, G. C., and Singer, D. L., 1978. Mineral resources map of the Talkeetna quadran 6,000 samples were collected for AMRAP geo- gle, Alaska: U.S. Geol. Survey Misc. Field Studies Map chemical studies in six l:250,000-scale quadran MF-870-D, scale 1:250,000 (in press). gles: Big Delta, Chignik, Sutwik Island, Lake Tripp, R. B., and Crim, W. D., 1978, Mineralogical map Clark, Survey Pass, and Talkeetna Mountains. showing gold and scheelite in heavy-mineral concen The main sample media collected were minus 80- trates in the Seward and Blying Sound quadrangles, mesh stream sediment, heavy-mineral concen Alaska: U.S. Geol. Survey Misc. Field Studies Map MF- trates of stream sediment, and rocks. Other sam 880-J, 3 sheets, scale 1:250,000 (in press). ple media collected in several of the quadrangles Stream flow and channel erosion investigations included stream water, vegetation, and stream- along the TAPS route bank sod. In addition, approximately 3,600 sam By J. M. Childers, D. Kernodle, and R. Loeffler ples of stream sediment and rocks were collected by U.S. Geological Survey geologists and Alaska During spring breakup along the trans-Alaska state geologists as part of AMRAP and Wilder pipeline route, project personnel measured chan ness studies in various parts of Alaska. More nel erosion and flood discharge and pursued than 8,000 of these samples were analyzed for as qualitative investigations of ice-flood interac many as 32 elements in the Anchorage laboratory tions. Exceptional icings were observed at sev and in mobile laboratories stationed at Juneau. eral pipeline stream crossings. These icings, in complete construction, and, on the Sagavanirk- REFERENCES CITED tok River, record floods combined to wash out some spur dikes and other river-training struc Curtin, G. C. Karlson, R. C., O'Leary, R. M., Day, G. W., and tures. McDanal, 8. K., 1978, Geochemical maps showing the The yearly surveillance of channel erosion at distribution and abundance of gold and silver in the Talkeetna quadrangle, Alaska: U.S. Geol. Survey Misc. 28 river crossings along the TAPS route provided Field Studies Map MF-870-E, 2 sheets, scale 1:250,000 another year's record for this ongoing project. (in press). This year's survey was to assess the channel ero-

B-6 sion after completion of the pipeline at all cross samples were collected for geochronologic stud ings. Relatively little erosion has occured at most ies by M. L. Silberman. of the sites since the 1976 surveys. Channel Preliminary work indicates that the intrusive changes were mainly due to construction of the rocks are pervasively metamorphosed. Labora pipeline during the last year. Methods of surveil tory examinations indicate that the intrusive lance include on-the-ground surveys, photo- rocks are predominantly granite in composition grammetric surveys, photographic comparisons, but may range from quartz monzonite to tona- and site visits. Evaluation of photogrammetric lite, according to the classification scheme of techniques confirmed their accuracy for channel Streckeisen (1973). Color index ranges from 5 to erosion studies. 30. Two types of textures predominate: (1) fine- to medium-grained granite and granite gneiss Regional appraisal of Alaska's ground-water re and (2) fine- to coarse-grained granite porphyry sources and augen gneiss (fig. 3). The granitic-textured By Chester Zenone and G. S. Anderson rocks contain a weakly developed, megascopic metamorphic fabric. All gradations from typi A compilation and review of work by earlier in cally granitic rocks to gneisses occur. In all sam vestigators and a survey of current water-use fig ples microscopic textures indicative of regional ures suggest that ground water is a large but metamorphism are moderately to well devel virtually unexplored and undeveloped resource oped. These textures include (1) granulation and in Alaska. Perennially frozen ground perma sutured grain boundaries of quartz and pheno- frost influences the occurrence, movement, crysts of potassium feldspar, (2) foliation and and availability of ground water except in the lineations, (3) polygonal porphyroclasts of southern and southeastern coastal areas of the quartz and potassium feldspar about which the State. The most extensive aquifers occur in allu foliation has been deformed, (4) mortar texture, vium of major river valleys such as the Yukon, and (5) dimensional preferred orientation of Tanana, Kuskokwin, and Susitna. Large quartz. amounts of ground water are also stored in gla The major minerals in the granitic rocks are cial outwash aquifers in coastal basin and valley perthitic microcline, quartz, plagioclase, musco- deposits at Anchorage, Kenai, and Juneau. Both vite, and biotite. No hornblende was observed. recharge and discharge of the large alluvial Accessory minerals include zircon (?), apatite, aquifers are concentrated along stream channels. garnet, calcite, allanite, and fluorite. Alteration The authors of the summary report (to be pub minerals that are probably related to metamor lished as a Professional Paper in 1978) estimate phism are sericite, chlorite, zoisite/clinozoisite, that 25 percent of the total volume of streamflow and iron oxides. in Alaska (exclusive of coastal areas) is contrib The contact of the intrusive rock, which ex uted by ground-water discharge. tends for at least 300 km in the Mount Igikpak and Arrigetch Peaks plutons, is well exposed. In NORTHERN ALASKA most places the contact is quite sharp and paral The Arrigetch Peaks and Mount Igikpak plutons, lel to compositional layering and foliation in the Survey Pass quadrangle, Alaska adjacent metasedimentary rocks. In parts of the By S. W. Nelson and Donald Grybeck Mount Igikpak pluton, however, the contact is complex, and the contact zone is an intricate Approximately 1,000 km2 of intrusive rocks is mixture of metasedimentary and meta-igneous spectacularly exposed in the Mount Igikpak and rocks. Satellitic stocks of intrusive rock along the Arrigetch Peaks plutons in central Survey Pass southwest part of the Mount Igikpak pluton are quadrangle. During 1977 field season these in locally separated from each other and the main trusive rocks were studied as part of the Survey body by mixed zones, and in places intrusive rock Pass AMRAP project. The intrusive rocks were is hard to distinguish from the mixed rocks. The mapped and sampled to determine their compo intrusive nature of the contact is established by sitional variation, to determine their internal (1) the presence of large xenolithic blocks of structure, and to evaluate the mineralization as metasedimentary rocks up to 5 X 10 m in size, (2) sociated with the intrusive bodies. In addition, dikes and sills of orthogneiss cutting metasedi-

B-7 mentary rocks, (3) discordant contacts, and (4) northeast of Akabluak Pass, however, a large an- narrow, discontinuous contact metamorphic tiform in the granite parallels a similar fold in zones containing amphibolite, garnet mica the overlying metasedimentary rocks. schist, and skarns. The plutons are mineralized, especially along In general, attitudes of the contact indicate their peripheries. The mineralization is reflected that the plutons form shallow to moderately in numerous minor occurrences of ore minerals northward dipping slablike bodies, although in and marked geochemical anomalies in lead, mo places this relation is complicated, in part by lybdenum, tin, and silver. Only small areas of the folding. The northward dipping, conformable as contact zones have been examined in detail, but pect of the contact is especially clear along the occurrences of molybdenite, sphalerite, chalco- north side of both plutons. pyrite, galena, stibnite, and magnetite as well as Folds in the plutons range from small symmet skarn samples with more than 0.1 percent tin ric ones with amplitudes on the order of centi and beryllium have been located. Most occur meters, to isoclinal folds with amplitudes of less rences of ore minerals found to date are small. than a meter, to large-scale open symmetric folds The most favorable areas are the contacts of the with amplitudes on the order of hundreds of me pluton in the vicinity of Tupik Creek and an area ters. The small-scale folds are defined by the of skarn about 200 by 300 m in a headwater trib foliation, whereas the large-scale ones are indi utary of the Takahula River (T. 22 N., R. 22 E.). cated by compositional layering in the gneisses. Prominent yellow-orange altered zones as much Petrofabric studies have not yet established the as a square kilometer in area occur in the granitic relations between the various folds in the intru rocks near Angiaak Pass (T. 24 N., R. 17 E.) and sive rocks or between these and folds in the meat the southeast end of the Arrigetch Peaks plu tasedimentary rocks. In one locality 10 km ton (T. 22 and 23 N., R. 22 E.). The altered rocks

FIGURE 3. Surface of coarse-grained augen gneiss from the Arrigetch Peaks pluton.

B-8 consist of silicified granite poor in mafic minerals L., and Mull, C. G., 1977, Geologic map of the Brooks but with disseminated pyrite. Their metal con Range, Alaska: U.S. Geol. Survey Open-File Report 77- 166-B, scale 1:1,000,000. tent is barely above background levels. The dis Sable, E. G., 1977, Geology of the western Romanzof Moun tribution and apparently limited amount of tains, Brooks Range, northeastern Alaska: U.S. Geol. mineralization at the periphery of the main Arri- Survey Prof. Paper 897, 84 p. getch Peaks and Mount Igikpak plutons suggest Streckeisen, A. L., 1973, Plutonic rocks; classification and that a more favorable environment for substan nomenclature recommended by the IUGS Subcommis- sion on the systematics of igneous rocks: Geotimes, v. tial mineralization is in the apical zones or roof 18, no. 10, p. 26-30. zones of similar plutons that are not so well ex Turner, D. L., and Forbes, R. B., 1977, Geochronology of the posed. The discovery of such buried or shallowly southwestern Brooks Range (abs.): Alaska Geol. Soc. exposed plutons will be difficult because of the Symposium, Program with Abstracts, p. 42-43. absence of deformation and narrow contact- Turner, D. L., Forbes, R. B., and Mayfield, C. F., 1978, K-Ar geochronology of the Survey Pass, Ambler River and metamorphic zones that are apparently charac eastern Baird Mountains quadrangles, southwest teristic and because of the complex structure of Brooks Range, Alaska: U.S. Geol. Survey Open-File Re the surrounding metasedimentary rocks. port 78-254, 41 p. Previous workers (Brosge and Reiser, 1971; Fritts and others, 1971; and Brosge and Pessel, Potential strata-bound lead-zinc mineralization, 1977) have suggested that these plutons are of Philip Smith Mountains quadrangle, Alaska Cretaceous age. We believe, however, that the By J. T. Dutro, Jr. pervasive metamorphism and complex structure in the granitic rocks may indicate that the rocks Upper Devonian rocks in the Philip Smith are much older, perhaps equivalent to the Paleo Mountains quadrangle contain anomalous oc zoic granites in the Romanzof Mountains (Sable, currences of lead, zinc, and several other metallic 1977) or the Chandalar quadrangle (Grybeck and elements. A marine depositional cycle, initiated others, 1977). The Cretaceous age of the plutons in the early Late Devonian, produced more than may reflect the widespread Mesozoic metamor- 1,200 m of fine-grained clastic rocks and reefoid phic event(s) in the southern Brooks Range limestone (unnamed formation). Laminated (Turner and Forbes, 1977; Turner and others, dark fine-grained limestone and black shale low 1978). Since the potassium-argon dates are prob in the sequence are succeeded by brown-weath ably tied to the pervasive metamorphic event(s) ering calcareous siltstone and fine-grained sand reflected in the deformation of the plutons, the stone below the main reef horizon. Stro- age of the emplacement is uncertain. Geologic matoporoid reefs and biostromes, as much as 50 evidence is inconclusive because the youngest m thick, at as many as four levels through a 500- rock unit that is presently recognized as intruded m interval, are spatially related to Silurian and by the granite is the Upper Devonian Hunt Fork Devonian structural high areas. In some places, Shale (Brosge and Pessel, 1977). Rubidium/ the lower Frasnian sequence contains volcani- strontium and lead isotope studies are underway clastic rocks and flows, including mafic pillow in order to establish the age of these rocks. lavas. Both the Hunt Fork Shale and the underlying REFERENCES CITED unnamed heterogeneous unit are widely distrib uted in the southern part of the Philip Smith Brosge, W. P., and Reiser, H. N., 1971, Preliminary bedrock Mountains quadrangle (Brosg& and others, geologic map, Wiseman and eastern Survey Pass quad 1977). These rocks, together with the overlying rangles, Alaska: U.S. Geol. Survey Open-File Report 71- Kanayut Conglomerate, reflect a major onlap- 56, scale 1:250,000. Brosge, W. P., and Pessel, G. H., 1977, Preliminary recon offlap-onlap cycle that extends into the early naissance geologic map of the Survey Pass quadrangle: Carboniferous. U.S. Geol. Survey Open-File Report 77-27, scale The unnamed formation, approximately 500 1:250,000. m thick, records five depositional cycles, three of Fritts, C. E., Eakins, G. R., and Garland, R. E., 1971, Geology which are capped by reefoid limestones. The and geochemistry near Walker Lake, southern Survey Pass quadrangle, Arctic Alaska: Alaska Div. Geol. Sur overlying Hunt Fork Shale, more than 700 m vey Ann. Kept., p. 19-26. thick, contains at least five cycles, two of which Grybeck, Donald Beikman, H. M. Brosge, W. P., Tailleur, I. contain thin limestones in their upper parts.

B-9 Samples from a measured sequence of these Anomalous concentrations of lead, zinc, cop Frasnian strata were analyzed spectroscopically per, and silver are found in the Philip Smith for manganese, chromium, cobalt, nickel, zirco Mountains A-2 quadrangle, near a pre-Frasnian nium, copper, lead, and vanadium. Atomic ab structural high (Detra, 1977). At this location the sorption analyses were also performed for lead unnamed Frasnian strata lie unconformably on (D. E. Detra, written commun., 1977). Most of earlier Devonian carbonates on which a paleo- the anomalous values are in the ranges reported karst surface was developed. Rock samples from for black shales (Hawkes and Webb, 1962), al just above this discontinuity yield very high val though those for manganese, cobalt, and chro ues for lead, zinc, copper, and silver. In each of mium exceed the black shale averages. All means four samples, lead values are 20,000 ppm or are greater than those reported by Mason (1966) more; copper ranges from 150 to 1,000 ppm; zinc as typical of shales in general. At eight levels, all ranges from 5,000 to 340,000 ppm; and silver val in the deeper water parts of the cycles, five or ues are 30 to 150 ppm. more elements attain peak values (fig. 4). These Minerals present are sphalerite, pyrite, chalco- high values suggest that the Hunt Fork Shale pyrite, galena, and tetrahedrite (P. B. Barton, could have been the source of subsequent con oral commun., 1977). Preliminary results of anal centration of metals in promising structural set yses of fluid inclusions give a temperature range tings. for the original fluid of 150 to 200°C. This range

235 PPM ( 102 ) 30

170 215

320

460

550

630

- 1050

-UNCONFORMITY

FIGURE 4. Generalized stratigraphic section of unnamed Upper Devonian formation and Hunt Fork Shale showing depositional cycles and variation in analyses of nine elements in rock samples taken at approximately 15-m intervals. Eight levels where five or more elements attain peak values are indicated.

B-10 is clearly not cold, but it is also not typical of hy- served was 0.6 m in diameter. Many conglomer drothermal solutions (E. W. Roedder, oral com- ate outcrops are isolated local exposures; some mun., 1977). appear to have been deposited as local channel Original high metallic values in the dark shales fills rather than as a continuous sheet. At one lo could have been concentrated during or after cality conglomerate is interbedded with mud- burial, and the highly metalliferous fluids might stone containing the fossilized pelecypod have migrated subsequently into favorable strat- Buchia, indicating a probable Neocomian age. igraphic or structural traps either at the uncon Regional mapping indicates that most conglom formity or above structural highs or both. Fur erate is contained within terranes that have ther exploration for similar structural settings yielded specimens of Neocomian Buchia, but a should be carried out on a regional basis and po few outcrops may be correlative with the For tential target areas studied in greater detail to tress Mountain Formation of Albian age. evaluate their economic potential. The sampled conglomerate is on allochthonous thrust sheets that are believed to have moved REFERENCES CITED many kilometers northward during Early Creta ceous time relative to more deep-seated rocks in Brosge, W. P., Reiser, H. N., Dutro, J. T., Jr., and Detter- the Brooks Range (Tailleur and Snelson, 1969; man, R. L., 1977, Generalized geologic map of Philip Smith Mountains quadrangle, Alaska: U.S. Geol. Sur Mull and Tailleur, 1977). Mapping suggests that vey Open-File Report 77-430, scale 1:200,000. most of the conglomerate was deposited before Detra, D. E., 1977, Delineation of an anomalous lead-zinc or during the time the allochthons were being area in the Philip Smith Mountains A-2 quadrangle, moved and therefore was originally deposited an Alaska: U.S. Geol. Survey Open-File Report 77-223, undetermined distance south of its present local lip. Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in min ities. Rocks in the allochthonous sheets located eral exploration: New York, Harper and Row, 415 p. near congolmerate outcrops can account for the Mason, Brian, 1966, Principles of geochemistry (3rd ed.): source of most clasts except the granitic types, New York, John Wiley and Sons, Inc., 329 p. which have no readily apparent source. A wide range of igneous compositions is repre Granitic clasts from Upper Cretaceous conglomer sented in the conglomerate. Mafic rocks, such as ate in the northwestern Brooks Range By C. F. Mayfield, I. L. Tailleur, C. G. Mull, and M. L. basalt and diabase, are abundant and are not Silberman considered in this discussion because they occur throughout the Brooks Range. The granitic rocks Upper Cretaceous conglomerate in the De range in composition from quartz monzonite to Long Mountains and foothills of the central and diorite, and their volcanic equivalents are nearly western Brooks Range contains abundant light- as abundant. The sampling included 55 percent colored granitic clasts. This study was under quartz diorite or dacite clasts, 29 percent diorite taken to determine the age and composition of or andesite clasts, and 16 percent quartz mon these clasts because they do not have a nearby zonite, grandiorite, or quartz latite clasts, Feld source terrane. During the 1975 and 1976 field spar, quartz, biotite, and hornblende are the seasons, 76 samples of granitic igneous rocks most common igneous mineral constituents. were collected in isolated conglomerate outcrops Potassium-argon dates were obtained on from the Killik to the Kugarok River (fig. 5). Pe- hornblende separated from quartz diorite clasts trographic thin sections from a few samples were collected from two different localities. A sample studied; other samples were slabbed and stained collected 5 km south of Migrant Lakes (locality for feldspar identification. Two clasts were dated no. 1, fig. 5) gave an age of 153 ±5 m.y., and a using standard potassium-argon methods. sample from a tributary of upper Nunaviksak The conglomerate is poorly sorted and has a Creek (locality no. 2, fig. 5) gave an age of 186 ± 9 matrix of mudstone and wacke. Dominant clast m.y. The ages should be considered minimum types are chert, limestone, and a large variety of figures, but hornblende retains aragon well so fine- to coarse-grained mafic to granitic igneous these dates suggest that most of the granitic rocks. Clasts are well rounded, boulder to pebble clasts are of Jurassic age. size, and constitute more than 50 percent of the These age and composition data suggest at total rock volume. The largest granitic clast ob least five possible source terranes for the granitic B-ll 161° 160° 159° 158° 157° 156° 155° 154°

67°

50 100 KM I I

EXPLANATION Granite or quartz monzonite Sampled conglomerate Quartz diorite or diorite A K-Ar date from conglomerate clast Y///, Intermediate volcanic rocks

FIGURE 5. Location of sampled conglomerate and potential igneous source areas, northwestern Brooks Range. clasts: (1) the belt of plutons in the Schwatka terrane of felsic volcanic rocks in the Yukon- and Baird Mountains of the southern Brooks Koyukuk Province; (4) the felsic plutonic and Range; (2) a buried terrane in the Brooks Range volcanic phases of mafic and ultramafic alloch- that is now covered by large thrust sheets; (3) the thons in the west-central Brooks Range; and (5)

B-12 an upper thrust sheet that has been removed by most of the conglomerate clasts, many of which erosion. have abundant quartz. If extensive granitic The first possibility, that the clasts were de phases of these allochthons ever existed, they rived from plutons in the Schwatka and Baird have been removed by erosion. Mountains, is the most obvious, but it has several The final possibility for the source of the gran difficulties. The compositions of the plutons are itic clasts is that they were derived from a now mostly granite or quartz monzonite, whereas completely eroded allochthonous igneous ter clasts in the conglomerate are mostly quartz rane of Jurassic age. Regional structural, strati- diorite or diorite (fig. 5). The east to west distri graphic, and petrographic relations favor this bution of the plutons does not adequately ex interpretation. If the rocks of the west-central plain the abundance of clasts to the west in the Brooks Range have been displaced as much as De Long Mountains. In addition, regional rela has been suggested by Mull, Tailleur, Mayfield, tions suggest that the conglomerate is on some of and Pessel (1976), then the source of the clasts the structurally highest thrust sheets, which are would probably have been from an igneous ter interpreted as having overlain the core area of rane originally located south of the present the southern Brooks Range (Mull and Tailleur, Brooks Range. 1977). Thus, the granitic rocks forming the core of the range would not have been exposed for REFERENCES CITED erosion and subsequent deposition on these structurally high sheets. Mull, C. G., and Tailleur, I. L., 1977, Sadlerochit Group in The second possibility, a buried terrane within the Schwatka Mountains, south central Brooks Range, the Brooks Range, is unlikely owing to the struc in Blean, K. M., ed., The United States Geological Sur tural position of the conglomerate relative to the vey in Alaska; accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B27-B29. core of the Brooks Range. Mull, C. G., Tailleur, I. L., Mayfield, C. F., and Pessel, G. H., The third possibility, that the source terrane 1976, New structural and stratigraphic interpretations, was felsic rocks in the Yukon-Koyukuk Province, central and western Brooks Range and Arctic Slope, in is unlikely because no potassium-argon dates Cobb, E. H., ed., The United States Geological Survey from granitic igneous rocks of this area are older in Alaska; accomplishments during 1975: U.S. Geol. Survey Circ. 733, p. 24-26. than Early Cretaceous (W. W. Patton, oral corn- Roeder, Dietrich, and Mull, C. G., 1978, Tectonics of Brooks mun., 1977). Range ophiolites: Am. Assoc. Petroleum Geologists If it is accepted that the first three suggested Bull, (in press). source terranes are unlikely because of the com Tailleur, I. L., and Snelson, Sigmund, 1969, Large scale position, age, and structural position of the gran thrusting in northwestern Alaska possibly related to rifting of the Arctic Ocean: Geol. Soc. America Spec. itic clasts, then it is necessary to consider the Paper 121, p. 569. possibility that the clasts are derived from struc turally higher allochthons that have been partly Cretaceous Nanushuk Group, North Slope, Alaska or completely removed by erosion. The fourth By Thomas S. Ahlbrandt and A. Curtis Huffman possibility, that the source of the granitic clasts was from felsic phases of the mafic-ultramafic al The Cretaceous Nanushuk Group, where ex lochthons in the west-central Brooks Range, is posed on the North Slope (see fig. 2, area 1), is a speculative. Remnants of these allochthons are regressive depositional sequence including ma preserved as klippen in the De Long and western rine, transitional, and nonmarine intervals and Endicott Mountains, where they are the highest ranges in thickness from about 1,800 to 2,700 m structural unit of a series of allochthonous sheets (fig. 6). Preliminary data and previous work indi (Roeder and Mull, 1978). Small amounts of gran cate that there are at least two depocenters in the itic rocks occur at Siniktanneyak Mountain (fig. Nanushuk Group, one in the eastern part of the 5) and near Asik Mountain east of Noatak Vil National Petroleum Reserve in Alaska (NPRA), lage (U.S. Bureau of Mines, unpub. data, 1976). and one to the west. The rocks contained within At Siniktanneyak, plutonic and volcanic granitic the two depocenters differ in detrital composi rocks appear to be differentiated phases from tion, stratigraphic sequence, and sandrshale ra gabbro. Most of these rocks, however, have a tios. For example, coal occurs lower in the high feldspar content but little quartz, unlike eastern sequence than in the western sequence,

B-13 Nanushuk Group lected from the cores for petrographic, porosity and permeability, and delayed neutron analyses. Data from these studies will be included in the computer file as they become available. Nonmarine Depositional environments of sandstone in the western area were differentiated primarily on the basis of sedimentary structures, lateral and ver

Major fluviatile channel (s) tical stratigraphic position, and trace fossil as semblages. The nearshore marine sandstone include shoreface, foreshore, and offshore-bar Transitional < deposits (fig. 6). Shoreface sandstones are thin (< 5 m) and commonly have contorted basal zones, grading upward into low-angle crossbeds Offshore bar with symmetrically rippled upper surfaces Marine crossed by trace fossils. Common trace fossils in clude Gyrochorte (snail trails), Helicodromites Shoreface (spiral burrows), and Arthrophycus; occasionally Grain size Asterosoma and unnamed large-diameter (5- to FIGURE 6. Generalized stratigraphic sequence of Creta 10-cm-wide) burrows are found. The shoreface ceous Nanushuk Group, western North Slope, Alaska. sandstones gradually become thicker up section and are replaced by the prominent foreshore and sandstone constitutes a greater percentage sandstones (5-10 m thick) that are flat-bedded or of the Nanushuk Group in the eastern depo- low-angle crossbedded and contain relatively few center. trace fossils; Diplocraterion and Skolithos are In order to assess the resource potential of the most common. Although separated by siltsone or Nanushuk Group within NPRA, concurrent sur shale, the foreshore sandstones are imbricated face and subsurface studies are being conducted and grade laterally basinward into isolated sand that will later be integrated and compared with stone lenses that are commonly less than 10 m geophysical results through a computer file being thick and 60 m wide and are interpreted as off established by Petroleum Information, Denver. shore bars (fig. 6). The lenses decrease in size During the 1977 field season, 22 sections totaling away from the foreshore sandstones and pass lat 14,600 m were measured and described in detail. erally into siltstone or shale. This work was conducted primarily in the west The transitional interval (fig. 6) represents ern part of the northern foothills region but also mixing of marine and nonmarine sediments, included several of the type localities to the east. probably in a lagoonal or backshore environ Data recorded at each outcrop and in the cores ment. Isolated thin (< 5 m) sandstones contain included color; grain size; sorting, roundness, ing distinctive marine trace or megafossils are percent framework and porosity estimates; sedi interspersed with channel sandstones lacking mentary structures; bedding thickness; lamina trace fossils. Many environments of deposition tion types and style; biologic constituents, and energy levels are represented including es- including trace fossils; transport directions in tuarine, tidal flat, fluviatile channel, eolian, and fluvial sandstone; and radiometric readings. storm deposits (washover fans?). Marine (and These observations were made at 3- to 4-m inter probably brackish water) sandstones in the tran vals in sandstone and wherever possible in silt- sitional interval are contorted, symmetrically stone and shale. Laboratory analyses are rippled, may show ball and pillow structures, and currently being conducted on a total of 1,430 contain a variety of trace fossils including Areni- samples collected from the outcrops. These in colites, Rossellia, Ehizocorallium, Diplocrater clude 382 samples for petrographic, porosity and ion, Asteriacites (star fish traces), and plural permeability, and delayed neutron studies; 295 tubes. Nonmarine sandstones occur as strati- for organic geochemistry analyses; 418 for dino- graphically isolated channels, crevasse splays, flagellate, pollen, and spore content; and 285 for and thin sheet sands of possible lacustrine origin. foraminifer content; 48 samples are being col The channel sandstones are commonly 5 to 10 m

B-14 thick, less than 200 m wide, and consist of trough Smiley, C. J., 1969, Floral zones and correlations of Creta crossbed sets grading laterally or vertically into ceous Kukpowruk and Corwin Formations, northwest ern Alaska: Am. Assoc. Petroleum Geologists Bull., v. asymmetric climbing ripple structures (fig. 6). 53, p. 2079-2093. Normally they are not deformed, except for mi nor channel slumps, and trace fossils are limited to root traces, borings in fossilized logs, and rare Geologic investigations of metallic mineral re dinosaur(?) footprints. sources of southern NPRA By Michael Churkin, Jr., Carl Huie, C. F. Mayfield, The major channels are 10 to 30 m thick and and Warren J. Nokleberg contain thin conglomerate beds or pebble lags composed of chert, carbonate clasts, and quart- Geologic field investigations during the sum zite (fig. 6). Channel size decreases markedly mer of 1977 were concentrated in the southern above the major channels. Stumps of fossil trees, part of NPRA, an area whose mineral resource some in original growth position, are commonly potential is little known (fig. 7). Preliminary found near the bases of such channels. Coal is work determined that iron-stained zones, formed more common in the upper part of the nonmar- from weathering of accessory pyrite, were con ine section but was not observed to be thicker fined mainly to a thin stratigraphic interval in a than 4.3 m. This part of the section is interpreted structural sequence that is discontinuously cov as having been deposited on a delta plain. ered by overlying thrust plates of coeval rocks of Paleotransport studies indicate northeasterly different lithologies (fig. 8). Lead and zinc min transport of sediment in channels of the Nanu- eral deposits in two distinct areas, Red Dog and shuk Group in the western area. Such data sup Drenchwater Creeks (fig. 7), occur in stained port Chapman and Sable's (1960) interpretation zones having the same stratigraphic and struc of northwest-southeast oriented paleoshorelines tural setting. of the Nanushuk Group but differ with Smiley's The Brooks Range and its northern foothills in (1969) interpretation of a north-south orienta southern NPRA consist of numerous thrust tion in the western area. Higher energy environ plates with complex stratigraphy. The bedrock is ments, particularly the foreshore sandstones, intensely folded and faulted with relatively thin have the best hydrocarbon reservoir potential (500 m) sequences of marine sedimentary strata because they have (1) the best visible porosity in of Paleozoic and Mesozoic age. For this reason, outcrop, and maximum thickness (< 25 m, com major thrust plates are regarded as structural se monly 5 to 10 m), (2) an adjacent hydrocarbon quences. Rocks of the lowest recognizable struc source (marine shale), (3) lateral continuity tural sequence are mainly fine-grained siliceous along the paleoshoreline, and (4) a relatively sta clastic sedimentary rocks shale, siltstone, and ble composition owing to removal of diagen- minor sandstone interbedded with radiolarian etically unstable grains under high-energy condi chert and, locally, submarine volcanic rocks. The tions. Biostratigraphic zonation of the Nanushuk Group now seems possible with dinoflagellates, spores, pollen, and foraminifers. Spores and pol len have been recovered from rocks previously thought to be barren, and dinoflagellate zonation has been completed for the Fish Creek test well. The end result of the environmental, laboratory, and geophysical studies will be an assessment of the reservoir potential of the Nanushuk Group within NPRA for hydrocarbons and uranium ~-v ___ARCTIC_.CIRCLE ___---- and thorium. ~

REFERENCES CITED FIGURE 7. Sketch map showing location of mineral re Chapman, R. M., and Sable, E. G., 1960, Geology of the Utu- source assessment studies in southern NPRA (A, Mishe- kok-Corwin region, northwestern Alaska: U.S. Geol. guk Mountain quadrangle; B, Howard Pass quadrangle). Survey Prof. Paper 303-C, p. 47-167. Stippled pattern indicates area of mineral potential.

B-15 BROOKS RANGE NORTH SLOPE

NORTHERN COASTAL PLAIN FOOTHILLS

MINERAL POTENTIAL

FIGURE 8. Schematic section across the Brooks Range and the North Slope. stratigraphy of the lowest structural sequence, lena, and pyrite occur in tuff or in dark chert and which has the only significant base-metal depos shale that are either interbedded with or adja its, is generalized in a columnar section (fig. 9). cent to tuff. Barite is sparser and occurs in black At the base of the section, black shale and chert chert of the Lisburne Group and undiffer- of the Lisburne Group are overlain by argillite and chert of the Siksikpuk Formation that in APPROX. turn are overlain by limy chert, limestone, and THICKNESS IN shale of the Shublik Formation. This thin strati-

Lithic sandstone, mudstone, and shale Mmo graphic interval, of Carboniferous, Permian, and conglomerate Turbidile current structures Triassic age, is overlain by a thick section of Pelecypod Buchia. plant fragments coarse clastic rocks of Cretaceous age. The strata Chert, shale, and limestone Chert is dark to medium gray, weathering light olive-gray in the overlying structural sequence are charac radiolartaii ribbon chert inter layered with black shale Limestone is medium gray, thin terized mainly by carbonates. bedded, very fine grained and generally fos- silrferous with pelagic peleypods.-Monot.s The lowest structural sequence is broken up andHo'obia About 100 m thick by a series of smaller fault slices that form lens- Olive-gray siliceous shale, mudstone, argil life, and chert Maroon and green argilla like blocks usually striking east-west and dip ceous strata are hiqhly cleaved with argil- litic sheen on surfaces Gray to greenish ping steeply south. The fault slices generally are gray radiolanan ribbon chert, knobby and with rosettes of morcasite, weathers maroon, a few hundred meters long and a few tens of me orange, and shades of green and yellow For 250- mation is about 100 to ISO m thick Barite nodules, lenses, and veins in many places ters wide. Beds within the blocks are tectonically are conspicuous on argillaceous to I us slopes locally, formation brightly stretched and dismembered into broken forma stamed red tions. Internal folds are tight and nearly iso Dork facies Mainly black siliceous shale and clinal. The Drenchwater Creek area is an radiolarion ribbon chert Thm beds and laminae of light-gray turbidites and tuHaceous material example of the structural complexity where the interlayered with shale and chert occur m narrow sections of the formation Locally inter lowest structural sequence consists of a tectonic mediate to mafic tuff associated with inter- and breccias Tuffs are cemented by vary breccia. ing amounts of calcite and quartz and con tain chert pebbles that, together with lay During our field studies, we recognized signifi ering, indicate submarine origin Except for shelly fossil fragments ( mainly conoids ) cant potential for zinc-lead deposits along a that comprise thm beds of clastic limestone, pelagic fossils are radiolario, sponge spic- moderately well delineated regional trend of 500- ules, and abundant trace fossils of Were ires type Locally, galena, sphalerite, and chert, shale, and volcanic rocks of similar ages pyrite occur in vem$ and lenses Formation within the lowest structural sequence. Sulfide is about 250 m thick deposits in the Drenchwater Creek area formed BASE OF SECTION NOT EXPOSED contemporaneously with submarine volcanism and deposition of shale and chert of the Lisburne FIGURE 9. Generalized columnar section, lowest structural Group during Mississippian time. Sphalerite, ga sequence, southern NPRA.

B-16 entiated gray-green chert of the Siksikpuk For lead mineralization in the Drenchwater Creek mation. area were analyzed by detailed geologic mapping Two major geologic controls for the occurrence during the summer of 1977 as part of a mineral of sulfide deposits along the northern front of the resource assessment of the northern foothills of Brooks Range have been deduced from detailed the Brooks Range within the National Petro mapping in the Drenchwater Creek area and leum Reserve of Alaska. The area is located in from detailed traverses along the northern front. the western part of the Howard Pass quadrangle First, in the Drenchwater Creek area, the associ (fig. 7), which was partially mapped by Tailleur, ation of sphalerite and galena with submarine Kent, and Reiser (1966). During fieldwork in tuff and adjacent dark chert and shale strongly 1950-53,1976, and 1977,1. L. Tailleur (oral com suggests that: (1) sulfide mineralization was syn- mun., 1977) observed iron staining from weath genetic and stratiform, that is, mineralization oc- ered sulfide minerals, sphalerite, and minor curred at the same time as or just after barite in dark chert and shale in the lower part of sedimentation and volcanism; and (2) volcanic the Lisburne Group along Drenchwater Creek. exhalations were the source of the mineralizing He also noted the similarity of iron staining, sul fluids. Second, intense deformation, including fide minerals, and host rocks between the isoclinal folding, faulting, and development of Drenchwater Creek area and the Red Dog Creek broken formations, has severely disrupted a stra- area in the De Long Mountains, about 160 km tigraphic horizon favorable for the localization of west of Drenchwater Creek. base-metal sulfide deposits. The bedrock geology of the Drenchwater Sparse nodules of barite are widely distributed Creek area consists of the lower part of the Lis throughout the Siksikpuk Formation in southern burne Group (Mississippian), Siksikpuk Forma NPRA, and moderate geochemical concentra tion (Permian), Shublik Formation (Triassic), tions of placer barite occur in the streams drain Okpikruak Formation (Cretaceous), and minor ing the northern foothills of the Brooks Range. diabase dikes that cut all bedrock units. The Typical values of barium range from 1,000 ppm Mississippian through Triassic units are mainly to greater than 5,000 ppm in stream sediments chert and shale. Minor volcanic rocks, volcani- and from 200 ppm to more than 5,000 ppm with clastic rocks, impure limestone, and dolomite an average value of 1,500 to 2,000 ppm in selected also occur in the lower part of the Lisburne rock samples (P. Theobald, written commun., Group but are not common regionally. These 1977). The source of placer barite is most likely rocks generally indicate deep-sea sedimentation residual concentration of barite from sparsely and volcanism. The graywacke, siltstone, and scattered nodules or disseminated grains and mudstone of the Okpikruak Formation are tec- veinlets in various rock units. tonically interleaved with all older units. In other In summary, our studies have revealed that parts of the Brooks Range, the Okpikruak For the lowest structural sequence in the northern mation unconformably overlies all older rocks Brooks Range consists of a highly deformed se and apparently indicates initial uplift of the an quence of chert, shale, sandstone, and sparse cestral Brooks Range geanticline, which was submarine volcanic rocks of Mississippian to formed in the late Mesozoic. No stratigraphic Early Cretaceous age. We have recognized a sig unit is fully exposed in the Drenchwater Creek nificant potential for zinc and lead sulfide depos area because of intense folding, faulting, and its in a thin stratigraphic interval in the lowest shearing. Each of the Mississippian through structural sequence. The zinc and lead deposits Triassic units is relatively thin; maximum thick were formed in a deep marine volcanogenic envi ness is 150 m. The thickness and lateral extent of ronment. Finally, the potential for placer barite units are quite variable, with many discontinu in southern NPRA is significant. ous lenses of various formations (fig. 10). In the Drenchwater Creek area, intermediate to mafic Stratiform zinc-lead mineralization, Drenchwater tuff, tuffaceous sandstone, and shallow sills or Creek area, Howard Pass quadrangle, western flows occur locally in the lower part of the Lis Brooks Range, Alaska By Warren J. Nokleberg and Gary R. Winkler burne Group (fig. 10). Biotite from one shallow sill or flow has been dated by potassium-argon The geologic setting and controls of zinc and methods as 319 m.y. or Late Mississippian (Tail-

B-17 thrust plates in turn may be larger tectonic sli vers in an even coarser tectonic breccia. The tec tonic breccia appears to extend at least several tens of kilometers to the west and perhaps many tens of kilometers to the east along the northern front of the Brooks Range. Additional work dur ing 1978 will focus on the extent of this deformational belt. The tectonic breccia is a new definition of the disturbed belt originally de scribed by I. L. Tailleur (oral commun., 1977). Minor structures, which mimic the major struc tures, consist of pervasive cleavages, dismem bered lenses of various lithologies, and sparse, isoclinal minor folds. The planar structures and bedding generally strike east-west and dip mod erately south. The major and minor structures were formed during a single period of deforma tion, during which blocks from the north were

Strike and dip of thrust and folded under blocks to the south. bedding or cleavage All the galena and sphalerite occur in a 6- to 30-m-wide zone that extends eastward along Lower part of Lisburne Group strike from Drenchwater Creek for about 1,830 MIc, dark chert and shale Mlt, fine-grained tuff m. The zone of sulfide mineralization is re Area of prominent Mltf, coarse-grained tuff stricted to the Drenchwater thrust plate. Spha iron-staining and flows lerite and galena occur primarily as disseminated grains in undeformed fragments of rock, suggest Contact High-angle fault Thrust fault ing that sulfide crystallization occurred coinci- Dotted where Sawteeth on upper concealed dentally with sedimentation. Less commonly, plate, dotted where concealed sphalerite and galena occur in 1- to 2-cm-thick veins of massive sulfides in brecciated chert and FIGURE 10. Simplified geologic map of the Drenchwater shales. Locally the veins crosscut cleavage, sug thrust plate, Drenchwater Creek area, Howard Pass quad gesting a period of remobilization. Analyses of 24 rangle, Alaska. rock, soil, and stream sediment samples from the zone of mineralization show zinc values of 0 to leur and others, 1977). Similar volcanic and vol- greater than 10,000 ppm with an average of caniclastic rocks also occur in the Red Dog Creek about 200 ppm and show lead values of 20 to area, in conjunction with galena and sphalerite 15,000 ppm with an average of about 200 ppm. mineralization (Tailleur, 1970). Galena, sphaler There are two major geologic controls for the ite, and pyrite occur either in tuff, as on the west galena and sphalerite mineralization. First, the side of Drenchwater Creek, or in dark chert and unique occurrence of galena and sphalerite in dark shale interbedded with tuff, as along tuff or dark chert and shale adjacent to tuff Drenchwater Creek and east of the creek. strongly suggests that sulfide mineralization is The prevailing bedrock structure is a coarse stratiform and that volcanic exhalations were the grained tectonic breccia marked by interleaved, source of mineralizing fluids. And second, in fault-bounded lenses of the various formations tense deformation including isoclinal folding, that pinch out within a few hundred or thousand faulting, and dismembering of formations, has meters. The mixture of lenses of various forma severely disrupted the former stratiform deposit. tions is quite evident in most parts of the map A more extensive stratigraphic horizon that was area. Despite the intense deformation, discrete favorable for zinc-lead mineralization may have thrust plates can be separated. Each thrust plate extended from the Red Dog Creek area to the is defined by distinct proportions of various for Drenchwater Creek area, but now consists of dis mations and distinct structural domains. The membered lenses either hidden at depth or

B-18 rarely exposed at the surface as at Drenchwater an elevation of 120 to 150 m. If the terraces and Creek. beach gravel can be correlated, then the high sea level marked by the beach gravel most likely re REFERENCES CITED flects the interglacial immediately following the extensive Pleistocene glaciation. Tailleur, I. L., 1970, Lead-, zinc-, and barite-bearing samples from the western Brooks Range, Alaska, with a section Late Pleistocene glaciation is represented only on petrography and mineralogy by G. D. Eberlein and in the southeast corner of NPRA, where ice Ray Wehr: U.S. Geol. Survey Open-File Report, 16 p. reached down the Nigu River valley slightly be Tailleur, I. L., Kent, B. H., Jr., and Reiser, H. N., 1966, Out yond the mountain front, and by two very small crop/geologic map of the Nuka-Etivluk region, northern exposures of till with associated fresh cirques in Alaska: U.S. Geol. Survey Open-File Report, scale 1:63,360,7 sheets. the headwaters of Driftwood Creek. Most of the Tailleur, I. L., Ellersieck, I. F., and Mayfield, C. F., 1977, area on the North Slope within NPRA was too Mineral resources of the western Brooks Range, in low to nourish glaciers during late Pleistocene Blean, K. M., ed., The United States Geological Survey time and probably lay in the precipitation in Alaska; accomplishments during 1976: U.S. Geol. shadow of a southerly moisture source. Directly Survey Circ. 751-B, p. 24-25. across the range to the south, the record of late Surficial geology of the foothills and mountains of Pleistocene glaciation is rich. NPRA Surficial deposits, except a 1- to 3-m-thick re- By Warren Yeend golith, are generally absent from the low foothills of NPRA north of the Colville River. This area is A piedmont-type glacier covered a substantial characterized by broad, east-west trending, ap- part of the northern slope of the western Brooks palachian-type folds developed in Cretaceous Range within NPRA and extended into the sedimentary rocks sandstone, conglomerate, northern foothills of the range in early or middle siltstone, shale, and coal. The inland boundary of Pleistocene time. This glaciation had been pre unconsolidated sediments of the coastal plain viously recognized in the extreme eastern part of grades into the regolith of these sedimentary NPRA where it reached almost to the Colville rocks in such a way that the boundary is difficult River (Chapman and others, 1964). As the range to map without subsurface information. The becomes progressively lower to the west, the ice contact is questionably placed near the 500-foot was correspondingly more restricted. The ice did (150-m) contour throughout much of the area. In not extend further west than the Utukok River the areas bounded by the Utukok and Meade drainage basin because of the limited source area Rivers, however, bedrock with associated rego available at a sufficiently high elevation to nour lith is present at the surface with little if any ish glaciers west of this area. Much of the till de coastal plain deposits out to the 100- to 200-foot posited by this ice sheet has been eroded, leaving (30- to 60-m) contour, which is near the northern resistant erratics scattered on bedrock. However, boundary of the Utukok River and Lookout the ice had a marked effect on the topography, Ridge quadrangles. producing rounded, low, subdued hills and ridges The Colville River, which flows in an easterly and broad valleys up to and within the high parts direction for much of its course (350 km) follow of the range. Remnants of gravel outwash ter ing the valley cut in the weak shale of the Lower races, deposited as the ice melted or soon after, Cretaceous Torok and Fortress Mountain For are generally 40 to 60 m above the present mations, at an earlier time extended even further streams and rivers. They are present along the to the west. High-level, ancestral Colville River major north-flowing tributaries of the Colville gravels can be traced with confidence to Drift River as well as along the Colville River itself. Al wood Creek where they are perched 160 m above though it does not drain glaciated terrain, the the present river valley. It seems clear the ances Kokolik River valley, west of the Utukok River, tral Colville River was beheaded by the Kokolik possesses gravel terraces at a similar topographic River and subsequently the Utukok River and is position relative to the present drainages, 40 to about to be beheaded once again by a north-flow 60 m above present river levels. These alluvial ing tributary of Disappointment Creek. terraces can be traced into a suspected beach Mass-moved deposits are not common in the gravel at the inland margin of the coastal plain at foothills of NPRA. Talus and block rubble sur- B-19 round some of the high ridges and hogbacks, Coastal plain deposits of NPRA such as Meat Mountain. Earthflows, slumps, and By John R. Williams, L. David Carter, and Warren E. Yeend soil and debris flows are present on river banks where permafrost melts as the river impinges on The general character and distribution of un- a steep bank and rarely on south-facing slopes consolidated deposits in the northern Alaska underlain by fine-grained, ice-rich deposits. On coastal plain within the bounds of NPRA (fig. these slopes summer insolation causes melting, 11) are the subject of this study. Fieldwork, be and soil and vegetation of the active layer flow or gun in 1977 (Williams and others, 1977), is slide on the underlying permafrost. Solifluction, scheduled to continue another summer and is although sporadically present, does not seem to done in support of Chapters 105b (Environmen be a dominant process in slope lowering at pre tal Impact Assessment) and 105c (Land-Use sent, as it is in areas south of the Brooks Range. Study) of the National Petroleum Production REFERENCE CITED Act of 1976 (PL 94-258). Fieldwork was done by contract helicopter based at U.S. Geological Sur Chapman, R. M., Detterman, R. L., and Mangus, M. D., vey and Husky Oil field camps and at Naval Arc- 1964, Geology of the Killik-Etivluk Rivers region, Alas tic Research Laboratory at Barrow. The ka: U.S. Geol. Survey Prof. Paper 303-F, p. 325-407. laboratory has been the base for more than 30

162° 160° 150° 156° 154° 152°

Eolian sand (ruled where reworked by streams) Wave-cut shoreline hachures downslope

FIGURE 11. Generalized surficial deposits map of Arctic coastal plain in National Petroleum Reserve in Alaska. B-20 years of important arctic research, including sand containing lenses of detrital twigs. Else Quaternary geologic studies by Black (1951, where, the eolian sand makes up longitudinal 1964), McCulloch (1967), O'Sullivan (1961), and transverse dunes in an area that is approxi O'Sullivan and Hussey (1960), and Sellmann and mately that first mapped by Black (1951). Dune Brown (1973). Carson and Hussey (1960, 1962) sand is clean and without pebbles; it reaches a have worked out the origin of oriented lakes and thickness of about 30 m in the center of the sand have described processes of thaw collapse and dune area east of the Ikpikpuk River. filling by which the landscape is extensively Deposits mapped as nearshore marine sand modified. Long-continued activity of these pro were probably produced during more than one cesses largely obscures the initial marine, fluvial, transgression and consist of clean to silty or or eolian landforms. This modification, shallow clayey, fine to medium sand containing pebbles frozen ground, and scarcity of natural exposures and granules of chert. In the west these deposits make the photointerpretation and field mapping lie on both sides of a wave-cut scarp a short dis of unconsolidated deposits difficult. tance inland from the Chukchi Sea coast and on The unconsolidated deposits include Pleisto either side of another about 30 m above sea level. cene and Holocene alluvium of the modern East of the Meade River, the marine sand is. sep stream valleys and the Pleistocene marine, flu arated from eolian sand by a wave-cut scarp, the vial, and eolian deposits that blanket the remain base of which is 20 to 25 m above sea level. Still der of the coastal plain and constitute the Gubik farther east, in the vicinity of the Colville River, Formation (Black, 1964; Gryc and others, 1951); the marine sand unit includes areas where the they occupy nearly half of the 97,000 km of the marine deposits have been reworked by streams reserve. The southern limit of the coastal plain that crossed the coastal plain before develop lies along the zone at which the surficial upland ment of the modern stream valleys. The re silt (foothill silt of O'Sullivan, 1961) gives way to worked deposits can be distinguished from the bedrock and regolith in the uplands (fig. 11). The marine sand only by detailed field and labora silt unit overlies a sequence of marine and fluvial tory studies and, therefore, are not separated on deposits that occupy valleys cut in Cretaceous the geologic map. bedrock (O'Sullivan and Hussey, 1960). The Fine-grained marine deposits, consisting of silt gravel mapped (Chapman and Sable, 1960) at an and clay, lie beneath younger marine deposits at elevation of 120 to 150 m above sea level near Skull Cliff southwest of Barrow and to the east longitude 162° W at the upper limit of the up and southeast as indicated in boreholes and in land silt (fig. 11) is probably an ancient beach de coastal exposures (Black, 1964). Beach deposits posit. at Barrow can be traced southeastward along the The upland silt is as much as 40 m thick, is cal north shore of Teshekpuk Lake where these careous, and has a grain-size distribution like gravel and sand deposits lie landward of fine that of eolian silt. In local areas, however, the de grained silt and clay. This shoreline may repre posit is pebbly and in other places contains thin- sent an offshore bar or island complex that per bedded very fine to fine sand and horizons of haps enclosed a lagoon as well as land to the west felted peat. O'Sullivan and Hussey (1960) argued now filled by deltas (alluvial deposits) of the Ik for a noneolian origin, preferring instead a ma- pikpuk, Topagoruk, and Meade Rivers (fig. 11). rine-fluviatile one; however, the position of the Extensive modern gravel beaches are limited to silt downwind from extensive sand dunes and its Icy Cape, Cape Franklin, and Point Barrow; else grain size suggest that part may be eolian, and where the coastal beaches are narrow and thin. the unit may be polygenetic. At the present time data from our fossil collec Lower than the upland silt and separated from tion and organic samples for age dating have not it by a break in slope that ranges from sharp and been received from the laboratory, and much straight (wave cut?) to indistinct is a large area of compilation of field data remains. Therefore, marine sand of nearshore origin in the west and discussion of age assignments for these deposits eolian sand in the east. In some areas near its and possible revision of those by Lewellen boundary with the upland silt, the eolian sand (1972), McCulloch (1967), Sellmann and Brown has been reworked by streams (ruled pattern, fig. (1973), and U.S. Geological Survey (1976) are re 11) and is mantled by about 3 m of stratified served until the fieldwork is completed.

B-21 REFERENCES CITED 160°W 155°W Black, R. F., 1951, Eolian deposits of Alaska: Arctic, v. 4, no. 2, p. 89-111. 1964, Gubik Formation of Quaternary age in north ern Alaska: U.S. Geol. Survey Prof. Paper 302-C, p. 59- 91. Carson, C. E., and Hussey, K. M., 1960, Hydrodynamics in three Arctic lakes: Jour. Geology, v. 68, p. 585-600. 1962, The oriented lakes of Arctic Alaska: Jour. Geol ogy, v. 70, no. 4, p. 417-439. Chapman, R. M., and Sable, E. G., 1960, Geology of the Utu- kok-Corwin region, northwestern Alaska: U.S. Geol. Survey Prof. Paper 303-C, p. 47-167. Gryc, George, Patton, W. W., Jr., and Payne, T. G., 1951, Present Cretaceous stratigraphic nomenclature of northern Alaska: Washington Acad. Sci. Jour., v. 41, no. 5, p. 159-167. Lewellen, R. I., 1972, Studies on the fluvial environment, Arctic Coastal Plain Province, northern Alaska: Little- ton, Colorado, 2 volumes, 282 p. (pub. privately). McCulloch, D. S., 1967, Quaternary geology of the Alaskan FIGURE 12. Map of NPRA showing locations of Inigok shore of the Chukchi Sea, in Hopkins, D. M., ed., The and Tunalik well sites. Bering Land Bridge: Stanford Univ. Press, p. 91-120. O'Sullivan, J. B., 1961, Quaternary geology of the Arctic There are several airfields of this size, or coastal plain, northern Alaska: Iowa State Univ. Sci. smaller, along the northern coast of Alaska, but and Tech., Ph,D. thesis 191 p. O'Sullivan, J. B., and Hussey, K. M., 1960, Non-eolian origin none, to our knowledge, was constructed in the for silts of the Arctic Slope [abs.]: Geol. Soc. America winter. The Inigok and Tunalik airfields, how Bull., v. 71, no. 12, pt 2, p. 1940. ever, must be constructed in the winter and com Sellmann, P. V,, and Brown, Jerry, 1973, Stratigraphy and pleted before the end of May 1978, when the diagenesis of perennially frozen sediments in the Bar spring thaw weakens the ice runways on the row, Alaska, region, in North American Contribution to 2nd International Permafrost Conference, Yakutsk: nearby lakes. The winter snow roads connecting Washington, Natl. Acad. Sci., p. 171-181. the lakes and the drill sites will also be unusable U.S. Geological Survey, 1976, Reinterpretation of part of the after thawing commences. Gubik Formation, Arctic coastal plain: U.S. Geol. Sur Field and laboratory studies by the U.S. Geo vey Prof. Paper 1000, p. 83-84. logical Survey and the U.S. Army's Cold Regions Williams, J. R., Yeend, W. E., Carter, L. D., and Hamilton, T. D., 1977, Preliminary surficial deposits map, Na Research and Engineering Laboratory were tional Petroleum Reserve - Alaska: U.S. Geol. Survey made to evaluate the engineering-geologic and Open-File Report 77-868, 2 sheets. permafrost-related conditions to which the air strips and other structures would be subjected. Studies of proposed airfields at the Inigok and Tun- alik well sites, NPRA The field study was directed at evaluating soil By Reuben Kachadoorian, F. E. Crory1, and D. L. and permafrost conditions and locating suitable Berg1 gravel deposits for the Inigok and Tunalik sites. The Inigok site is underlain by frozen, silty, An integral part of the 1977-1978 petroleum fine sand, and the only locally available borrow is exploration program in NPRA is the drilling of a similar material. Sandy gravel, in limited quan two wells to depths of 5,760 m or more. These tities, was located at several sites along Judy deep wells, at Inigok and Tunalik (fig. 12), will Creek, about 24 km northeast of the proposed In take about 13 months to complete and will re igok site. These deposits are reworked early quire construction of temporary airfields that Pleistocene marine gravels. A large amount of must be operational during summer and winter. Holocene gravel was found along the Kikiak- The airfields must be capable of handling Hercu rorak River, about 42 km southeast of Inigok, but les (C-130) aircraft, which require runways 50 m its use requires removal of up to 3 m of frozen wide and 1,600 m long. overburden. The Kikiakrorak River gravel is pre dominantly flat or platey and will require crush 'U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, N.H. ing to produce a suitable graded gravel for the B-22 runway. An additional source of Holocene gravel must be used in the fill sections as well as the cut was located by a Husky Oil crew (operation con sections. tractor in NPRA) at the confluence of the Col- To evaluate the potential of thawed gravel for ville and Kikiakrorak Rivers, about 58 km east of supporting the aircraft, California Bearing Ratio the Inigok site. This gravel will also require (CBR) tests were conducted on all gravels and crushing. blends of sands and gravels. The potential for us Studies at the Tunalik site indicate that the ing soil-cement to stabilize the sands, particu proposed airstrip will be underlain by silty sand larly if the amount of gravel is limited, was inves and, locally, up to 1.5 m of frozen peat. Suitable tigated. Three different types of cements were sand and gravel borrow material was located tested at various water contents and soil-cement about 6.5 km west of the site, and an additional ratios. The soil-cements were prepared and source of sand and gravel was located on a ter cured at 4° C to simulate possible field condi race north of the Ongorakvik River, about 10 km tions. Good to excellent soil-cement could be north of the Tunalik site. These deposits occur produced with the Inigok sand, provided the ce along a late Pleistocene shoreline of the Arctic ment content was between 15 and 20 percent and Ocean. The sand and gravel north of the Ongor the water content was between 10 and 15 per akvik River are reworked late Pleistocene shore cent. These proportions would require 2,080 to line deposits. The gravel at these sites will not 2,800 tons of cement per 0.1-m depth of the run require crushing. way. The field studies provided a more complete Other laboratory tests included an investiga appreciation of conditions at each site, including tion of the possible use of salt to aid in thawing the quantity and quality of available construc and compacting frozen borrow sand and a study tion materials. Subsequent studies concentrated to estimate the evaporative loss from the frozen on laboratory testing of the materials and full- borrow. Results indicated that inordinate scale testing of design options. After standard amounts of salt would be required and that un classification tests were performed on samples of desirable thawing of the subgrade would occur the sand and gravel, a series of compaction tests after a few years. Substantial sublimation of the were conducted to define the optimum water sand, however, can be expected and could be ad content and density of each soil. The compaction vantageously employed to obtain higher degrees tests were also extended to study the possible of compaction in the upper layers of the subbase. range of attainable densities of frozen fine sand Calculations were made to estimate the depth placed and compacted at different initial water of seasonal thawing in different design configu (ice) contents. These same frozen samples were rations. Various thicknesses of gravel and combi later thawed and surcharged or otherwise con nations of gravel and insulating materials were solidated and wetted to determine the magni used in the computations, as were combinations tude of settlement associated with thawing. In all of landing mat over insulation. Insulation was in tests, the thaw-settlement of the sand when used cluded because it was considered nearly impossi as a fill was greater than the potential settlement ble to haul the necessary volume of gravel to of the same sand in a cut section. This condition prevent thawing into the ice-rich subgrade. The is caused by the lower in-place density of the fill use of landing mat over insulation was consid section, when compared to the in-situ densities ered as an alternative to gravel. of the same sand in the borrow pit. On the basis Several design options were tested at the U.S. of this finding, a design permitting extensive cut Army Waterways Experiment Station using sections rather than fill sections was adopted. sands and gravels similar to those at Inigok. The This procedure contradicts the normal proce test sections were trafficked with a device simu dure for construction in permafrost. The general lating a fully loaded Hercules landing gear. The preference for fill sections in highway and air tests disclosed that the silty sand, when saturate- field construction in permafrost areas is based on dand thawed, would require considerably more the greater in-place density of compacted fill sec than 50 cm of gravel surfacing. Test sections of tions constructed with thawed soils, as compared gravel over insulation, on a strong (that is, fro to the density of the frozen cut sections. In the zen) subgrade indicated that only 38 to 45 cm of two NPRA airfields, however, frozen material gravel was required, provided the insulation had B-23 a compressive strength of 4 kg/cm2. Landing mat (XM-19) placed directly on this insulation was also tested and found to be satisfactory. GRANITE IN EAST TESHEKPUK The laboratory and field studies indicated that frozen silty sand can be effectively used as a sub- Gamma SP ray Acoustic grade for both the Inigok and Tunalik airfields, 10,500' provided it is kept frozen by sufficient insula tion. The wearing surfaces of the runways should be 50 cm or more of gravel or landing mat pain- tedwhite. The exposed sandy shoulders of the runways should be stabilized and revegetated to reduce thawing and control erosion. The construction and performance of the Ini gok and Tunalik airfields will be carefully moni tored to obtain design, construction, and maintenance data that can be directly applied to the design and construction of future airfields in NPRA.

Granite on the Barrow arch, northeast NPRA By K. J. Bird, C. L. Connor, I. L. Tailleur, M. L. Sil- berman, and J. L. Christie Sandy limestone Well depth

Sample examination indicates that the Navy Calcareous sandstone > Sidewall core East Teshekpuk well (sec. 1, T. 14 N., R. 4 W.) bottomed in granite. This granite is the first Granite K/Ar Radiometric date found in the subsurface north of the Brooks Range. Drilling was halted at 3,250 m after pene E TESHEKPUK-I trating nearly 305 m of carbonate strata belong Prudhoe Bay ing to the Lisburne Group and about 12 m of rock described by the well-site geologist as "con glomeratic sandstone." During routine inspec ' ' batholith \ ;""''v tion of well cuttings from the "conglomeratic sandstone," Bird noted cuttings with a granitic texture (interlocking crystals) and granitic com FIGURE 13. Lithology and wireline log response of granite position (quartz, feldspar, and biotite). Because in East Teshekpuk No. 1. granitic rock or granitic debris (conglomerate) has not previously been reported from the sub and chert; approximately 60 percent are quartz. surface, a more detailed investigation of this in Feldspar grains were specifically searched for, terval was undertaken. Samples collected at 3-m but none were found. The age of these sandy car intervals were examined under the binocular mi bonates is Late Mississippian (Chesterian, fo- croscope and in thin section. The cuttings appear raminiferal zones 18-19). to represent the rock being drilled with only mi Granitic rock predominates in samples from nor amounts of contamination from uphole. This 3,240 m to the bottom of the well at 3,250 m. This brief report describes the rocks and their log re rock consists of roughly equal amounts of quartz sponse for the interval 3,200 to 3,250 m (fig. 13). and feldspar with 1 to 5 percent biotite. Cobal- Cuttings from 3,200 to 3,240 m in the Lisburne tinitrate staining reveals that about 75 percent of Group consist predominantly of sandy, fossilifer- the feldspar is potassium feldspar. Crystal size is ous grainstone with minor amounts of oolitic and variable, from 0.1 to 2.0 mm or more, and shows coated-grain grainstone, calcareous sandstone, an interlocking fabric characteristic of an ig wackestone, and secondary chert. The sand in neous origin. Samples from 3,240 m and 3,242 m the limestone and calcareous sandstone consists and a sidewall core from 3,238 m all show moder of fine- to very-fine, subrounded grains of quartz ate to complete alteration of the feldspar to clay B-24 minerals and of the biotite to chlorite. Below intrusive episode in northwestern Yukon 3,242 m the granite is relatively unaltered. (Baadsgaard and others, 1961) persisted west Because of the previous description of this ward through the northeast Brooks Range to the rock as a conglomeratic sandstone, a special ef subsurface of NPRA. fort was made to determine if the cuttings came X-ray fluorescence analyses of cuttings from from granite "wash," a sedimentary deposit, or 3,242 m to 3,245 m indicate that the granite has in=situ granite. Features indicative of a detrital the following composition and is similar in com origin that can be observed in cuttings include position to samples of the Okpilak batholith to (1) cuttings with one or more smooth or rounded the east (Sable, 1977, table 9): edges, (2) cuttings with a weathered rind on one Si02 ______74.56 % edge, (3) rounded, granule- or sand-size granitic A1203 ______12.38 fragments, and (4) cuttings showing sand or Fe203 ______1.43 MgO ______0.26 clayey matrix adhering to the edge of a larger CaO ______1.72 fragment. Because none of these features was ob Na20 ______2.49 served, it was concluded that the drill penetrated K20 ______5.21 in-situ granite and not a sedimentary deposit. Ti02 ______0.16 The contact between the Lisburne Group and P205 ______0.05 the granite appears to be about 3,237 m on the MnO ______0.017 basis of the prominent deflection of the various The areal extent of the granite in the East well logs at this depth (fig. 13). The contact is probably erosional. No evidence of thermal alter Teshekpuk well may be indicated by gravity ation or unusual mineralization was found in the data. The most recent Alaska gravity map carbonate rocks that would suggest an intrusive (Barnes, 1976) shows that the Okpilak batholith relation. The altered nature of the upper 6-9 m of is characterized by a prominent gravity low. The granite may indicate a weathered interval below well is located on the edge of a gravity low en an unconformity; however, no detrital feldspar closed by the 20 milligal contour. If the granite was observed in the sandstone and sandy at East Teshekpuk provides a similar gravity re limestone overlying the granite. sponse, then its outline may be described by the Results of potassium-argon dating on cuttings gravity low, which is irregularly shaped but gen from 3,245 m to 3,250 m shown below also sug erally elongate northwesterly parallel to the Bar gest an erosional, unconformable relation be row arch. tween the Lisburne Group and the granite. REFERENCES CITED Mineral Age Baadsgaard, H., Folinsbee, R. E., and Lipson, J. L, 1961, Ca Potassium feldspar ______332 ± 10 m.y. ledonian or Acadian granites of the northern Yukon Biotite ______243 ± 7 m.y. Territory, p. 458-465,, in Raasch, G. D., ed., Geology of the Arctic, Vol. 1: Toronto Univ. Press, 732 p. Barnes, D., 1976, Bouguer gravity map of Alaska: U.S. Geol. The ages of the two minerals are discordant, Survey Open-File Report 76-70, 1 sheet, scale 1: the feldspar yielding a considerably older age 2,500,000. than the chloritized biotite. The feldspar is only Sable, E. G., 1977, Geology of the western Romanzof Moun slightly perthitic and shows minor to locally tains, Brooks Range, northeastern Alaska: U.S. Geol. moderate sericitic alteration; the biotote is chlor Survey Prof. Paper 897, 84 p. itized severely (K20 content 2.1 percent). Biotite Organic geochemistry of rocks from three NPRA and chloritized biotite in general retain less ar wells gon during post-crystallization thermal events By Leslie B. Magoon and George E. Claypool than feldspar, but because of the minor alter ation of feldspar as well, we consider the ages to Preliminary results of the study of the NPRA be minimum figures. The feldspar age is close to oil and gas source rocks are available for the Top- an age of 384 ± 10 m.y. from hornblende, from agoruk No. 1, Oumalik No. 1, and South Barrow the contact aureole of the Okpilak batholith (see No. 13 wells. The Topagoruk No. 1 well, located fig. 13 for location) (W. P. BrosgS, H. N. Reiser, in sec. 25, T. 15 N., R. 16 W., Umiat meridian and M. L. Silberman, unpub. data, 1976); this (UM), was drilled to a total depth of 3,201 m agreement suggests that an important Devonian from June 1950 to September 1951 and was ex- B-25 tensively cored (Collins, 1958). At a depth of indications of hydrocarbons were found in this about 1,829m, slight indications of hydrocarbons well. This well penetrates the Lower Cretaceous were found (Collins, 1958). Analytical work done and Jurassic sections and a thin Triassic unit be on some of the cores shows that the section fore bottoming in the argillite. The organic car ranges in age from Devonian to middle Creta bon content for Lower Cretaceous rocks is 1 to 2 ceous. The average organic content of the Devon weight percent, as in the Topagoruk and Ouma ian, Permian, Triassic, and Lower Cretaceous lik wells. The Oumalik Formation (< 530 m in rocks is 1 to 2 weight percent, a surprisingly high Barrow well) and the pebble shale unit (Neoco- value if it is representative of 2,700 m of section. mian in the Barrow well) show, from north to In the Prudhoe Bay field, Morgridge and Smith south, increasing organic carbon contents of 1.12, (1972) found the Cretaceous section to be richer 1.27,1.35 and 1.36,1.94, 2.15, respectively. More (5.4 weight percent) and the Permian and Trias data and detailed stratigraphic correlations are sic leaner (0.7 weight percent); the Devonian sec necessary to evaluate this apparent trend. The tion was not analyzed. The organic carbon organic carbon content of the Jurassic (0.83 content of the Jurassic section in the Topagoruk weight percent) rocks is reasonable when com well is 0.5 to 1.0 weight percent, which is less pared to the Jurassic (0.66 weight percent) rocks than in the Prudhoe Bay field (1.9 weight per of the Topagoruk well. The values for the Trias cent). The Carboniferous rocks from both areas sic rocks and argillite appear anomalously high. contain less than 5 percent organic carbon, val Kerogen is dominantly herbaceous, but the sec ues too low to be considered an oil source rock. tion is probably immature with respect to the Oil-generating capacity is indicated in these temperature history necessary for oil generation. rocks by presence of amorphous and some herba Except for the argillite and an anomalous shal ceous kerogen and by above-average volatile hy low (338 m) sample, vitrinite reflectance values drocarbon content, as measured by thermal are 0.4 or less. evolution analysis-flame ionization detection (TEA-FID) (Claypool and Reed, 1976). Evidence REFERENCES CITED for degree of thermal maturity based on ther Claypool, G. E., and Reed, P. R., 1976, Thermal-analysis mal alteration index (TAI), TEA-FID, and vi- technique for source-rock evaluation; quantitative esti mate of organic richness and effects of lithologic vari trinite reflectance suggests that the rocks are ation: Am. Assoc. Petroleum Geologists Bull., v. 60, no. fully mature below 2,438 m. The argillite is prob 4, p. 608-612. ably post-mature (overcooked). Collins, F. R., 1958, Test wells, Topagoruk area, Alaska, in The Oumalik No. 1 well, located in sec. 30, T. 6 Exploration of Naval Petroleum Reserve No. 4 and ad N., R. 16 W., UM, was drilled to a total depth of jacent areas, northern Alaska, 1944-53, Part 5, Subsur 3,618 m from November 1949 to April 1950. The face geology and engineering data: U.S. Geol. Survey Prof. Paper 305-D, p. 265-316. well was extensively cored (Robinson, 1956). At Morgridge, D. L., and Smith, W. B., 1972, Geology and dis depths from 300 m to 1,200 m and at about 3,290 covery of Prudhoe Bay field, eastern Arctic Slope, m, slight indications of hydrocarbons were found Alaska, in King, R. E., ed., 1972, Stratigraphic oil and (Robinson, 1956). This well penetrates a thicker gas fields: Am. Assoc. Petroleum Geologists Mem. 16, p. 489-501. Lower Cretaceous section than Topagoruk No. 1, Robinson, F. M., 1956, Core tests and test wells, Oumalik bottoming in the pebble shale unit at 3,618 m. area, Alaska, in Exploration of Naval Petroleum Re Organic richness and kerogen composition in the serve No. 4 and adjacent areas, northern Alaska, 1944- same interval are comparable to that of the To 53, Part 5, Subsurface geology and engineering data: pagoruk well. Depth to maturity, as indicated by U.S. Geol. Survey Prof. Paper 305-A, p. 1-70. vitrinite reflectance, is shallower in the Oumalik well (2,286 m) than in the Topagoruk well (2,438 Release of NPRA (NPR-4) data By Robert D. Carter m), probably as a result of uplift and erosion. The South Barrow No. 13 well, located in sec. The Naval Petroleum Reserves Production 14, T. 22 N., R. 18 W., UM, was drilled to a total Act of 1976 transferred jurisdiction over Naval depth of 771 m from December 1976 to January Petroleum Reserve No. 4 from the Department 1977. Analytical work was done on the canned of the Navy to the Department of the Interior ef cuttings acquired at intervals of 15 m, and one fective June 1, 1977. Shortly after the act was 10- 3/4 inch casing was set to a depth of 354 m. No signed by the President on April 5, 1976, prep-

B-26 arations were made by the Geological Survey to Miocene Atlantic mollusks are known from receive voluminous Navy files accumulated dur Carter Creek, 240 km east of Ocean Point, but ing nearly 50 years of custodianship of the re the fauna there differs from that at Ocean Point serve. and could be of a different age. Much study re During 1977 more than 100 boxes of file mate mains to be done before a reasonable age can be rial from Washington, D.C.; NPR-1, Elk Hills, inferred for the Ocean Point material, but it will California; Anchorage, Alaska; and Barrow, have a direct bearing on the time of the connec Alaska, were received in Menlo Park. A memo tion of the Arctic and Pacific Oceans. The large randum from the Deputy Solicitor, Department collection promises to be a cornerstone for future of the Interior, advised the Geological Survey in studies of the little known Neogene molluscan June, 1977, that information acquired under the paleontology of the Arctic Ocean. exploration program for the National Petroleum The collared lemming inhabits holarctic tun Reserve in Alaska was to be made available to dra. Generally speaking, one species is common the public under the Freedom of Information to Eurasia and North America west of Hudson Act. As a result of this opinion, an agreement was Bay. A different species, generally thought to be reached with the Environmental Data Service of a primitive relic, lives east of Hudson Bay on the the National Oceanic and Atmospheric Adminis Ungava Peninsula; fossil forms similar to the Un- tration (NOAA) in Boulder, Colorado, to adver gava collared lemming are known from the early tise, reproduce, and disseminate the geologic and Pleistocene of Eurasia and from the late Pleisto geophysical data to the public. cene of Pennsylvania, at the southern limit of Consequently, material pertinent to the petro Wisconsin Glaciation. Fossils of the more wide leum exploration of the reserve since the comple spread species are known from the late Pleisto tion of the Pet-4 program (1944-1953) was cene of Eurasia, Alaska, and western Canada and extracted from the files and sent to Houston for have been found in Wyoming at the southern integration with data gathered during the Navy's limit of the glaciation. Two years ago Agadjanian exploration program which was begun in 1974. (1976) predicted that the Ungava collared lem Every effort was made to obtain the best possible ming must once have lived in Alaska, although records for reproduction such as original well no fossils had been found there. During the four- reports, log films. Copies of these data will be day reconnaissance, Repenning found a speci sent to NOAA in Boulder. Information on the men of the Ungava lemming in the upper part of eight wildcat wells drilled in the northeast part the Gubik Formation, also at Ocean Point. Addi of the reserve will be released first, followed by tional work on the fossil lemming is needed to de South Barrow wells 6 through 14, and then by termine its age significance in Alaska, although it the seismic data in year-by-year packages. The would certainly seem to be pre-Wisconsin. Its initial release should be available early in 1978. presence as a fossil in Alaska strongly supports the interpretation that the living species of the Fossil reconnaissance study, eastern NPRA Ungava Peninsula is a relic. By Charles A. Repenning A new Late Cretaceous flora was found much During four days in August 1977, a trial recon farther down section in the Prince Creek Forma naissance to evaluate the fossil potential of east tion (fig. 2, area 5) that has not yet been studied ern NPRA was conducted by Repenning, Louie by Spicer. In the four days of fieldwork, however, Marincovich, and Robert A. Spicer. Bob Detter- nothing was learned of the Cretaceous-Tertiary man served as guide to the geology and geogra boundary which may be within the Prince Creek phy. Formation and the marine Schrader Bluff For At Ocean Point, along the lower Colville River mation; the Schrader Bluff intertongues with the on the north slope of Alaska (fig. 2, area 4), Mar upper part of the Prince Creek. incovich made a large collection of mollusks in the top of a unit that has been mapped as the REFERENCE CITED Schrader Bluff Formation. The fauna is late Ter Agadjanian, Aleaxander, von, 1976, Die Entwicklung der Lem- tiary in age and is also exclusively of "Atlantic" minge der zentralen und ostlichen Palaarktis im Pleistozan: origin, predating the opening of Bering Strait Mitt. Bayer. Staatssamml. Palaont. hist. Geol., v. 16, p. possibly some 3 million years ago. Middle or late 53-64.

B-27 Reconnaissance snow survey of NPRA, April 1977 coastal plain where there was less wind crust. By Charles Sloan, Dennis Trabant, and William Snow density was intermediate (about 0.30 kg/L) Glude where the snow depth was greatest. Average snow density for the area was about 0.29 kg/L. A reconnaissance snow survey of NPRA was Water equivalent of the snow pack ranged from made in April 1977 to ascertain general snow less than 100 mm in the coastal areas to more characteristics and distribution patterns. than 250 mm in the Brooks Range and averaged Thirty-nine localities were sampled to determine nearly 130 mm for the entire area. snow depth, density, and basal snow pack tem Basal snow pack temperatures ranged from perature. about 20° C on the coastal plain, where the Snow cover in April was thin, wind packed, snow pack was thin and ambient air tempera and relatively continuous. Depth and water con tures were low, to about 5°C in the foothills tent generally increased with altitude and dis where the snow pack was thicker and ambient tance from the coastal plain. temperatures higher. Snow depth ranged from less than 200 mm near the coast to nearly 800 mm in the Brooks Hydrologic reconnaissance of lakes in NPRA, 1977 By Charles E. Sloan and Richard F. Snyder Range near Howard Pass. Snow density was rela tively high (greater than 0.35 kg/L) in the coastal A reconnaissance study of lakes was made in areas where a wind crust was developed and NPRA from June to August 1977 using a helicop lower (less than 0.25 kg/L) inland from the ter on floats. Data were gathered from 202 lakes.

FIGURE 14. Snow density sampling, western NPRA, April 1977. B-28 Field measurements were made of depth, water for large drainages in NPRA. The primary causes temperature, specific conductance, pH, bicar of floods in the study area are rapid spring snow- bonate, secchi depth, color, and turbidity. A bot melt and summer or fall rainstorms. Spring tom grab sample was taken and preserved, and breakup flooding was significantly increased on the existence of an inlet or outlet noted. Water the Colville and Meade Rivers by the presence of samples were taken from selected lakes to deter ice jams. Low-gradient stream systems such as mine algae growth potential, total organic car the Miguakiak River and Teshekpuk Lake are bon, and dissolved inorganic constituents. flooded by the upstream flow of the Ikpikpuk Lakes are the most conspicuous hydrologic River. Winds can cause rapid increases in stage feature in NPRA, covering 20 to 40 percent of the and discharge on the Miguakiak River. Persis surface area of the coastal plain. Most of the tent high flow occurs in basins with large or nu lakes are less than about 2 m deep and freeze to merous lakes where the streams are adequately the bottom in winter. Teshekpuk Lake, covering supplied with water from lake storage. about 816 km2, is the third largest lake in Alaska Low or no flow was observed during the period and is about 6 m deep over most of its basin. of below-normal precipitation from June Most of the deeper lakes in the reserve are in the through August 1977 in several rivers in NPRA. hummocky eolian terrain on the coastal plain Runoff for the water year 1977 for the Nunavak south of Teshekpuk Lake. A number of these Creek, for example, was about 50 percent below lakes are in the 50-foot (15 m) class, and some the annual discharge for six years of record. approach 20 m in depth. Glacial lakes in the About 80 percent of the runoff occurs during Brooks Range are relatively deep, as much as 37 snowmelt on this small stream draining the m in NPRA. coastal plain. Most of the lakes in NPRA have very low spe cific conductance; exceptions are those near the Development and operation of gas fields in the South Barrow area coast that have direct tidal connection to the sea By Robert D. Carter and Robert J. Lantz or have been contaminated by sea water from storm surges. Lakes that freeze to the bottom are Responsibility for supplying gas to the Point shallow enough that wind effects can stir the bot Barrow area passed to the Department of the In tom sediment and produce turbid water. The terior and the Geological Survey on June 1,1977. lakes with the greatest turbidity are the shallow The task is twofold: to continue development coastal plain lakes from Barrow to the Colville and operation of the South Barrow field, and to Delta that are underlain by marine silt. Lakes of find new gas reserves. similar depth underlain by sand are much less An inspection trip to the field and reference to turbid. engineering reports (H. J. Gruy and Associates, Streamflow in NPRA, 1977 Inc., 1976; Husky Oil NPR Operations, Inc., in By S. H. Jones ternal memo., 1976) revealed a need for addi tional wells, extensive workovers of existing Streamflow of selected streams in NPRA was wells, and upgrading of the gas gathering, meter studied by reconnaissance methods during June, ing, and transmission systems. Negotiations are July, and August 1977. The survey made during presently being conducted with the Navy Facili June and July measured discharge and collected ties Command concerning detailed mapping of water-quality samples during low-flow condi these systems so that remedial action can be tions. Streamflow records were collected on the taken. Colville, Meade, and Miguakiak Rivers, and Well drilling at present emphasizes exploring Nunavak Creek from June to September to de and developing new gas reserves so that the termine runoff characteristics of water quality South Barrow field can be shut-in, analyzed in and suspended sediment. detail, and then developed for maximum deliver- Estimates of maximum evident flood-peak ability. One exploratory well and two eastern discharges were made for 10 streams on the basis area confirmation well sites, to be drilled in 1978, of field evidence. Maximum evident flood-peak were chosen on the basis of recent geologic and discharge rates range from 0.08 m3/s/km2 of geophysical data. Detailed plans for the drilling, drainage area to 0.88 m3/s/km2 of drainage area coring, and testing of these wells were written B-29 with particular emphasis on gathering informa treating the submergence as if it were a sudden tion leading to more accurate estimates of re climatic change. For slow transgression and at serves and well deliverability. A supplementary points close to the shoreline, this assumption reservoir engineering study will provide recom must be examined carefully. We assume further mendations in this regard. The Navy Facilities that essentially all the latent heat is released Command is also being asked to consider the over a very small temperature interval, effec construction of a road and pipeline from the tively at 0f near the top of the ice-bonded perma eastern wells to the Point Barrow area. Special frost, and at 0'f near the bottom of permafrost. geophysical studies are underway to identify res We assume also that prior to submergence, a ervoir beds and to trace their structural attitudes thermal steady state had been established on and possible facies changes. land, the geothermal flux is constant, and that the thermal properties of the frozen and thawed REFERENCE CITED materials and the moisture content are uniform. These assumptions are reasonably consistent Gruy, H. J., and Associates, Inc., 1976, Reservoir engineering with subsurface observations on land near Prud and geologic study of the South Barrow gas field, Naval Petroleum Reserve No. 4, Alaska: Report prepared for hoe Bay (Gold and Lachenbruch, 1973). We have U.S. Navy, 16 p. chosen parametric values consistent with the fragmentary observational evidence presently A simple target model for offshore permafrost at available; no great precision should be attached Prudhoe Bay to the numerical results. By Arthur H. Lachenbruch and B. Vaughn Marshall The analysis (Lachenbruch and Marshall, Because of the importance of ice-bonded sub- 1977), based on heat-conduction theory, under sea permafrost in engineering problems related scores the importance of distinguishing between to the exploitation of offshore oil and gas, it is the two cases, 00 > 0f (fig. 15a) and 00 < 0f (fig. useful to consider a highly idealized preliminary 15b). In the first case (00 > 0f), permafrost model of the gross features of Prudhoe Bay per thaws downward progressively from the sea bed mafrost. Although it will certainly be wrong in and eventually disappears. In the second case (00 detail, the model should serve to focus attention < 0f), permafrost persists near the sea bed, even on the sensitive parameters and provide some in the steady state. The second case is expected guiding context for future work. It is a target in a near-shore band where sea-ice freezes to the model in the sense that it gives us something to bottom seasonally, but it is also possible at off "shoot" at. shore locations. 00 depends on the seasonal re The model is represented schematically in fig gime of the sea water, and 0f depends upon salt ure 15. At the time of submergence, the tempera transport mechanisms in the sea bed; small ture is given by the curve t=0; thereafter the sea changes in the relative values of 00 and 0f can bottom is maintained at temperature 00, and the change the sign of their difference and convert melting (and freezing) temperature of interstitial one regime to the other. Several aspects of this ice is maintained at 0f at the upper surface and problem have been discussed in detail by Harri- 0'f at the lower surface of the ice-bonded perma son and Osterkamp (1976) and Osterkamp frost. We shall assume that 00 and 0f have re (1975). mained constant at their presently observed When the cold permafrost is inundated by the values since some effective date of submergence sea, it absorbs heat from the relatively warm sea t=0. This constancy, of course, cannot be true, bed above and from geothermal flux rising from but the assumption is justified by the resulting below. After an initial period (about 1,800 years simplicity of the analysis and by our present ig for Prudhoe Bay), temperatures in the ice- norance of the time-dependence of these quanti bonded permafrost become nearly uniform at the ties. Figure 15a represents the case 00 > 0f which value determined by the melting temperatures of results in a thawed layer at the sea bed, and fig its upper and lower surfaces (for example, curve ure 15b represents 00 < 0f where there is only t3, fig. 15a). A substantial amount of the heat superficial thawing, resulting largely from sea conducted downward through the sea bed is con sonal effects. This model is one-dimensional, sumed in warming the permafrost to its melting that is, we neglect horizontal transfer of heat, temperature (not melting it) in the initial phases. B-30 Temperature, 6,-

sea bed

Case I e>o

FIGURE 15. Schematic representation of sub-sea temperatures at successive times t=0, t,, ts, t,, following submergence of a region underlain by ice-rich permafrost, a. Mean sea-bed temperature, 00, greater than melting temperature, 0f, at top, X(t), of permafrost, b. Mean sea-bed temperature, 0O, less than melting temperature, 0f, at top of permafrost. For conditions at Prudhoe Bay, the total amount per surface, and this disparity in thawing rates of this heat is equivalent to that required to melt can be expected to increase with time. 25-30 m of ice-bonded permafrost. One-third of A literal interpretation of the model suggests the heat required to deplete the initial subfreez- that ice-bonded permafrost might extend to ing cold reserve of permafrost is supplied by depths of 500 m within 15 to 20 km of the shore geothermal flux entering through the lower line at Prudhoe Bay today. The model can be re boundary; for conditions at Prudhoe Bay the fined, revised, or superseded by data acquired lower surface of permafrost rises only about 7 m from a few offshore holes to depths of 100 m in during the first 1,800 years, and thereafter it selected localities. rises at the near-constant rate of about 12 m per thousand years. Under conditions of figure 15a REFERENCES CITED (00 > 0f), the rate of thawing of the upper sur Gold, L. W., and Lachenbruch, A. H., 1973, Thermal condi face of ice-bonded permafrost diminishes pro tions in permafrost A review of North American Lit gressively with time because the thickness of the erature, in Permafrost The North American insulating thawed layer increases. The model ap contribution to the second International Conference: plied to thermal observations in the sea bed im Washington, D.C., Natl. Acad. Sci., p. 3-23. Harrison, W. D., and Osterkamp, T. E., 1976, A coupled heat plies that the present rate of thawing of the and salt transport model for sub-sea permafrost: Alaska upper surface of ice-bonded permafrost is about Univ. Geophys. Inst. Rept. UAG R-247, 21 p. 1 cm/yr or less. Hence permafrost is probably de Lachenbruch, A. H., and Marshall, B. V., 1977, Sub-sea tem grading faster at its lower surface than at its up peratures and a simple tentative model for offshore per-

B-31 mafrost at Prudhoe Bay, Alaska: U.S. Geol. Survey total intensity magnetic and Bouger anomaly Open-File Report 77-395,54 p. profiles. These profiles and their relation to ma Osterkamp, T. E., 1975, A conceptual model of offshore per jor stratigraphic and physiographic boundaries mafrost: Alaska Univ. Geophys. Inst. Kept. UAG R-234. are shown in figure 16. Regional fields have not Geophysical profiles through the Shaviovik- been removed from the data. The regional mag Echooka River region netic gradient in this area decreases in a south By Dennis Giovannetti and K. J. Bird westerly direction according to Woolson (1962, pi. 3). Two short offsets perpendicular to our line Gravity and magnetic data were collected of traverse show a pronounced gradient (3-5 along a northwest-trending 66-km-long profile gammas/km) decreasing to the southwest, in ap that crosses the southern foothills and northern parent agreement with the regional map. The Brooks Range, northeastern Alaska. These data Bouger gravity map of Alaska (Barnes, 1976) are to be used in making depth-to-basement cal shows that the regional gradient in this area de culations in this area to aid in structural inter creases southeasterly, in the same direction as pretations. The gravity and magnetic work in the our profile. Although analysis of the data is still Shaviovik-Echooka River area is part of a pro incomplete, inspection of the profiles shows little gram of geologic and geophysical studies di response to the outcropping basement rocks and rected toward further understanding the stratig few significant anomalies elsewhere. raphy, tectonic style, and petroleum potential of An 8 milligal gravity low is coincident with a the region. This area was chosen for study be syncline, mapped by Keller, Moms, and Detter- cause of the variety of data available. Future man (1961) beneath the Fin Creek well. Creta phases of the study will incorporate the following ceous sedimentary rocks (density = 2.65-2.55 data: (1) surface mapping, (2) U.S. Navy seismic g/cc) are exposed to the north and south of the records, (3) well logs and drill cuttings from four syncline, and Tertiary sedimentary rocks (den wells, (4) low-angle aerial photographs obtained sity = 2.39 g/cc) are exposed in the synclinal from Standard Oil of California (Reber, 1976), trough. Low-amplitude anomalies are character and (5) measured outcrop sections. istic of the gravity profile south of the syncline. Ground magnetic and gravity readings (.8- to These anomalies may be related to geologic 2.5-km station spacing) were used to construct structure, although they are about the same

North gammas South 40

.A. 0 V Total Intensity Magnetic Profile

iilhgals 0-

Bouguer Anomaly Profile

Arctic Foothills Brooks Range elers -1200 Mesozoic . 900 Shaviovik Fin Creek rocks - 600 t t £ . ft - 300 MesozoiA Tertiary!?) rocks, Mesozoic rocks rocks V ^-"^

FIGURE 16. Gravity and magnetic profiles across the northeastern Brooks Range front. Geologic structure, shown diagram- matically here, is the subject for further study. Vertical exaggeration about 5X.

B-32 magnitude as possible gravity errors caused by deep to be detected by ground magnetic observa elevation inaccuracies. Confidence in correlation tions. The small but sharp 20-gamma anomaly of these anomalies with geologic features will de observed between Kemik-1 and Kemik-2 has a pend on comparison with an updated geologic source depth of 1,800 m or less and is within the map now in progress. Density measurements of Mesozoic sedimentary section. It may be caused selected outcrop samples indicate small density by pyroclastic sedimentary rocks logged between contrasts of 0.07-0.03 g/cc between basement 609 and 820 m in Kemik-1. metasedimentary rocks and the overlying Mis- sissippian clastic and carbonate rocks. Larger REFERENCES CITED contrasts exist higher in the section. The nearly flat character of the magnetic pro Barnes, D. F., 1976, Bouger gravity map of Alaska: U.S. Geol. Survey Open-File Report 76-70, 1 sheet, scale file may indicate that the basement and overly 1:2,500,000. ing sedimentary rocks are nonmagnetic to Brosge, W. P., Brabb, E. E., and King, E. R., 1970, Geologic slightly magnetic, or that there is a lack of sig interpretation of reconnaissance aeromagnetic survey of nificant susceptibility contrast along the length northeastern Alaska: U.S. Geol. Survey Bull. 1271-F, 14 of the traverse, or a combination of the two. The P- Keller, A. S., Morris, R. H., and Detterman, R. L., 1961, Ge nonmagnetic character of the rocks is supported ology of the Shaviovik and Sagavanirktok Rivers region, by low susceptibility measurements of 26 sam Alaska: U.S. Geol. Survey Prof. Paper 303-D, p. 171- ples from lower Paleozoic, upper Paleozoic, and 221. Mesozoic basement rocks. Only one sample, a Reber, S. J., 1976, Use of IR color photographs and canyon mafic intrusive rock collected 41 km southwest of photos in photogeologic mapping, Central Brooks Range, Alaska: Am. Assoc. Petroleum Geologists Bull., the profile, was magnetic enough to give a quan v. 60, no. 12, p. 2188. titatively reliable measurement; a value of 1,426 Woolson, J. R, 1962, Exploration of Naval Petroleum Re X 10~6 cgs was measured using a superconduct serve No. 4 and adjacent areas, northern Alaska, 1944- ing susceptometer. Other samples gave question 53, pt. 4, Geophysics: U.S. Geol. Survey Prof. Paper 304- able results of up to 60 X 10~6 cgs, all of which are A, 25 p. [1963]. considered weakly magnetic to nonmagnetic. Hydrology of arctic Alaska There appear to be no obvious correlations of the By J. M. Childers, D. Kernodle, and R. Loeffler low-amplitude magnetic anomalies (5 to 20 gam mas) with geologic features along the profile. A reconnaissance of streams in western arctic Moderately magnetic intrusive rocks are associ Alaska in August 1977 completed a project begun ated with upper Paleozoic carbonate rocks at in 1975 to study the water resources of arctic Flood Creek, 41 km to the southwest, but the ab Alaska. Surveys were made at 55 sites mostly on sence of a significant anomaly along the eastward larger streams draining the Brooks Range. Indi projection of these rocks implies their absence or rect measurements of maximum evident flood alteration to nonmagnetic minerals. Aeromagne- and bankfull discharge were computed from sur tic profiles east of the Shaviovik-Echooka River veys of channel geometry and high water marks. area indicate a 30- to 40-gamma anomaly coinci Results of the flood surveys indicate that maxi dent with the Brooks Range front. Pre-Missis- mum evident flood-peak discharges were under 1 sippian mafic extrusive and intrusive rocks in a m3/s/km2 for streams with drainage areas less west-trending belt have been interpreted to be than 3,000 km2 and were under 0.5 m3/s/km2 for the source (Brosge and others, 1970). Well data streams with drainage areas greater than 3,000 (Kemik-2) indicate that the basement rocks are km2. Bankfull discharge generally exceeded 50- deeper than 2,774 m just north of the Brooks year flood estimates made using relations devel Range front. If the mafic belt extends to the Sha oped from Alaska stream-gaging records and viovik-Echooka area, at a depth of about 3,125 multiple regression analysis of drainage basin m, a 7- to 15-gamma anomaly might be expected characteristics. Land along rivers is attractive between Kemik-2 and Brooks Range front. No for transportation routes and communities, but anomaly of significant amplitude and width to floods are important hazards to be considered for suggest a source depth of 3,125 m is observed. planning development on potential floodways. A The west-trending mafic belt either does not ex general lack of flood and climatic records in tend into the Shaviovik-Echooka area or is too northern Alaska leaves little alternative except

B-33 channel flood evidence for assessing the flood rorak Spring, with 1,500 microsiemens specific hazard. The flood hazard is complicated by the conductance, all springs sampled were of good effects associated with ice, permafrost, and chan drinking water quality. From Point Hope to the nel erosion and deposition. Canning River no rivers were found with measur Surveys were made at 29 sites on streams, able discharge. Through over 2 m of ice, deeper springs, and lakes during April 1976 a time of holes in stream and lakes contained liquid water annual low flow in the Arctic. The surveys were with water quality varying from good for drink made to measure streamflow, lake depth, and ing to objectionable in taste, odor, and color. water quality. Springs were located from large ic ings sometimes visible on Landsat imagery. Sites EAST-CENTRAL ALASKA on rivers were chosen at large bends or conflu ences where greater depths are usual. Sites on Late Paleozoic radiolarians and conodonts found in chert of Big Delta quadrangle lakes were chosen near mid-lake where greater By H. L. Foster, D. L. Jones, T. E. C. Keith, Bruce depths were considered likely. Radar fixes were Wardlaw, and F. R. Weber often helpful in locating position of the helicop ter on almost featureless coastal plain. The sur Late Paleozoic radiolarians and conodonts veys indicate the existence of some springs along have been found at one locality in red chert asso the south slope of the Brooks Range and east of ciated with green and gray chert in the Big Delta Umiat along the North Slope. Except for Kav- D-l quadrangle, Alaska (see fig. 18). These are

FIGURE 17. Water quality sampling at Bogie Creek in the De Long Mountains, June 1977. B-34 144° 45' 144B 30' T,

64° 45'

EXPLANATION Alluvium Fossil locality Chert and greenstone Fault

Serpentinized ultramafic rocks Thrust fault

FOSSIL LOCALITY Green grit unit BIG DELTA QUAD Black quartzite unit

Schist and gneiss unit 10 KILOMETERS Granitic rocks i

FIGURE 18. Geologic map of northeastern Big Delta quadrangle, Alaska, showing new fossil locality. the first pre-Pleistocene fossils found in the Big forms can be assigned to a group of Neogondo Delta quadrangle. The radiolarians are abundant lella that ranges from late Wolfcampian through and consist of: Guadalupian (Permian). Streptognathus be came extinct before the Guadalupian, so a Wolf 1. Unnamed elongate ladderlike specimens campian age is indicated. with large reticulate pores, The chert occurs interlayered with basaltic 2. Paronaella sp. forms with complete outer greenstone that, in turn, is associated with ser- margins connecting the three primary arms, and pentized ultramafic rocks. Locally, thin beds of 3. Unnamed morphotypes related to late slightly metamorphosed graywacke are also in stages of the Family Albaillellidea. terlayered with the greenstone and chert. Most The radiolarians can be matched with species of the chert is fairly massive, although closely known elsewhere to occur in rocks of Late Penn- fractured. Much of it has a sugary texture and is sylvanian and Early Permian age (D. L. Jones too recrystallized for extraction of fossils. Green and Brian Holdsworth, unpub. data, 1978). and gray chert is most abundant, but some red The conodonts consist of Streptognathus sp., chert is also interlayered. Most of the chert oc Xaniognathus sp., and juvenile specimens be curs at the northeastern end of the ultramafic longing to the genus Neogondolella. The juvenile outcrops. B-35 The chert, greenstone, graywacke, and ultra- general succession of nine climatically controlled mafic rocks are slightly metamorphosed and events can be grouped into five major time divi compose a distinct terrane of oceanic origin that sions (table 1). appears to have been thrust over adjacent Preglacial gravel is best exposed in high (90- greenschist, marble, quartzite, and metamor 100 m) terraces north of the Chandalar River phosed grit. Because of the fault relations, near the mouth of its East Fork (locality 1 in fig. knowledge of the age of the chert does not di 19). The clasts, predominantly of pebble size, rectly help date the adjacent metamorphic rocks. consist almost entirely of quartz, chert, and The age of the chert does document a late Paleo quartzite. In comparison with younger allu zoic or younger period of major tectonic activity vium, the clasts are more rounded, better sorted, during which oceanic rocks were emplaced on smaller in mean diameter, and more quartzose. A the continentally derived metamorphosed sub similar-appearing and possibly correlative gravel stratum that makes up the bulk of east-central lies at the base of an 80-m bluff along the West Alaska. Fork of Chandalar River (locality 2). This unit is indurated, contains thin lignitized organic beds, Late Cenozoic stratigraphy of the south-central and has been tectonically deformed. Brooks Range TABLE 1. Stratigraphic succession in the Koyukuk and By Thomas D. Hamilton Chandalar drainage systems, south-central Brooks Range Downcutting along parts of the Koyukuk and Chandalar drainage systems has formed bluffs Postglacial downcutting, thaw-lake formation, and peat Holocene accumulation in major valleys. Accumulation of basin- that locally stand 20 to 80 m high near the south fill deposits up-valley from Itkillik II end moraines. flank of the Brooks Range in the Chandalar, ITKXLUX II GLACIATION. Deposition of till, ice- stagnation deposits, outwash, loess, and proglacial Wiseman, and Bettles quadrangles (fig. 19). lake sediments. Sediments exposed in bluff faces record a se Late Interglacial or interstadial unconformity with local quence of glacial, interglacial, and preglacial Plaistocene peat and forast beds. events that extends through the Quaternary and ITOLLIK I GIACIATION. Deposition of till, outoash, and probably into late Tertiary time. Many events Deposition of interglacial graval, now heavily oxidized. Middle(?) can be correlated with the standard Brooks Pleistocene SftGAVMnKKXOK RIVER GIACIATION. Deposition of younger Range glacial succession, as defined by Detter- pre-Itkillik drift(s). Deposition of thick interglacial alluvium. man, Bowsher, and Dutro (1958) within the Barly(?) Pleistocene AHAKTOVDK RIVER GIACIATION. Deposition of older pre- northern Brooks Range and later extended Itkillik drift(s). southward by Hamilton and Porter (1975). A Pliocene (?) Deposition of preglacial gravel. Older pre-Itkillik drift has been mapped lo o^V~V cally in the Philip Smith Mountains and Chan CONTINENTALINENTAL ^ .' \ \ dalar quadrangles (Hamilton, 1978a, 1978b) and 68° »-----^* I T* PHILIP SMITH MTS \ correlated with the Anaktuvuk River Glaciation of Detterman, Bowsher, and Dutro (1958). Till of presumed Anaktuvuk River age is present at the base of a 60-m bluff along the south side of the Koyukuk River downvalley from Bettles (local ity 3). A possibly correlative till lies near the base of locality 2 in the Chandalar basin. Thick interglacial alluvium at locality 2 forms a 54-m deposit that grades upward from crossbedded fine to medium sand at the base into sandy pebble-to-small-cobble gravel near the top. A comparable fluvial sand, 16 m thick, con taining abundant detrital wood is exposed along the Koyukuk River at locality 3, where it lies be FIGURE 19. Sketch map showing selected bluff exposures, tween drifts of presumed Anaktuvuk River and Koyukuk and Chandalar drainage basins, northern Alaska. Sagavanirktok River age. B-36 Younger pre-Itkillik drift has been mapped as correct, the Itkillik I Glaciation is older than the fairly extensive surface deposits in the Philip late Wisconsin age assigned it by Hamilton and Smith Mountains, Chandalar, and Wiseman Porter (1975) and is separated from Itkillik II quadrangles (Hamilton, 1978a, 1978b, and un- events by an interglacial or mild interstadial pub. data, 1978) and is correlated with the Saga- warm enough to allow treeline to advance to po vanirktok River Glaciation of Detterman, sitions within at least several tens of kilometers Bowsher, and Dutro (1958). In the Koyukuk ba of its present limits. On the other hand, absence sin, boulder-rich diamicton associated with la of pronounced weathering and soil formation custrine clay overlies thick interglacial alluvium suggests that this interval was probably much and in turn is overlain by heavily oxidized gravel. briefer than any preceding interglaciation. The diamicton was deposited when Brooks Itkillik II end moraines usually lie close to the Range glaciers flowed south into the Koyukuk south flank of the Brooks Range and are associ basin and created extensive proglacial lakes ated with abundant ice-stagnation deposits and (Hamilton, 1969). extensive outwash trains (Hamilton and Porter, Heavily oxidized interglacial alluvium directly 1975). Stream incisions through the moraine underlies till of Itkillik I age in exposures near belts usually expose 10 to 20 m of unweathered Settles and near the mouth of the North Fork of gray till that passes downvalley into terraced the Koyukuk River (localities 4-6). Along the outwash deposits 10 to 15 m high (for example, South fork of the Koyukuk, it underlies unoxi- locality 10). The glacial sediments usually bear dized outwash gravel of the Itkillik I Glaciation less than 0.5 m of postglacial loess, peat, and sod. (locality 7). Farther west, at localities 3 and 8, the Alluviation of presumed Itkillik II age occurred gravel appears at heights of 20 to 40 m above between 13,000 and 24,000 years B.P. in the modern river level in positions stratigraphically Koyukuk Valley, and possibly correlative loess at below widespread loess and lacustrine silt depos locality 3 contains organic matter near its base its of Itkillik I age. that dates 28,500 ±775 years B.P. Itkillik I drift has been described by Hamilton Postglacial events have included (1) downcut and Porter (1975) and more recently has been ting along major valleys, (2) alluviation in basins mapped in greater detail within the Philip Smith dammed by Itkillik II end moraines, (3) thaw- Mountains, Chandalar, and Wiseman quadran lake formation in ice-rich silt deposits of Itkillik gles (Hamilton, 1978a, 1978b, and unpub. data, age, and (4) reforestation of the larger valleys of 1978). Thick (20 to 40 m) sections through Itkil the Koyukuk and Chandalar drainage systems. lik I end moraines are exposed along the Koyu Radiocarbon dates show that downcutting oc kuk River (for example, localities 4-6), and curred sometime after 13,160 ± 170 years B.P. at correlative outwash is exposed in both the Koyu locality 5 and basin-filling behind Itkillik II mo kuk and Chandalar basins (for example, local raines commenced shortly before 13,000 years ities 7 and 9). Conflicting radiocarbon dates have B.P. in the upper Sagavanirktok Valley. Thaw- been obtained on Itkillik I deposits. A maximum lake formation in the Koyukuk basin was initi limiting age of 35,400 ±2,000 years B.P. was ob ated about 11,300 years B.P. at one locality. tained on gravel beneath Itkillik I till at locality 5 REFERENCES CITED (Hamilton and Porter, 1975), but dates obtained Detterman, R. L., Bowsher, A. L., and Dutro, J. T., Jr., 1958, subsequently on large wood samples from both Glaciation on the arctic slope of the Brooks Range, the Koyukuk and Chandalar drainages seem to northern Alaska: Arctic, v. 11, p. 43-61. prove that Itkillik I ice advances are older than Hamilton, T. D., 1969, Glacial geology of the lower Alatna 40,000 years. Valley, Brooks Range, Alaska, ire Schumm, 8. A., and Bradley, W. C., eds., United States contributions to The interval between the Itkillik I and II ad Quaternary research: Geol. Soc. America Spec. Paper vances is marked by nondeposition and pre 123, p. 181-223. sumed downcutting at most sites. In several bluff 1978a, Surficial geologic map of the Chandalar quad exposures beyond Itkillik ice limits, peat beds rangle, Alaska: U.S. Geol. Survey Misc. Field Inv. Map containing spruce wood dated at greater than MF-878-A, 1 sheet, scale 1:250,000 (in press). 1978b, Surficial geologic map of the Philip Smith 40,000 years B.P. are present between loess and Mountains quadrangle, Alaska: U.S. Geol. Survey Misc. outwash deposits correlated with the Itkillik I Field Inv. Map MF-879-A, 1 sheet, scale 1:250,000 (in and II advances. If dates and correlations are press). * B-37 Hamilton, T. D., and Porter, S. C., 1975, Itkillik glaciation in m3/s was measured at the gage; in September, the Brooks Range, northern Alaska: Quaternary Re 21.3 m3/s was measured. The gage height had in search, v. 5, p. 471-497. creased 2.1 cm between the two measurements. Waller, Feulner, and Tisdel (1962) suggested Geohydrology of the Fairbanks-North Star that the aquifer is recharged by seepage losses Borough from the Delta River and Jarvis Creek, and that By G. L. Nelson the ground water flows northeastward to feed the springs. However, the springs may also be fed by Monitoring of baseflow and ground-water lev ground-water recharge from the Tanana River els in residential areas of the Yukon-Tanana east of the springs, the Gerstle River, and several uplands near Fairbanks (fig. 2, area 6) is continu small streams draining the north face of the ing. Ground-water levels in the fractured rock Alaska Range. aquifer have been declining more than 1 m/yr in some parts of the upper hills and ridgetops. REFERENCE CITED However, ground-water levels in and baseflow from most areas on the lower slopes are stable. Waller, R. M., Feulner, A. J., and Tisdel, F. E., 1962, Ground water contaminated by arsenic or ni Ground-water movement in the Fort Greely area, Alas trate in excess-of Environmental Protection ka [abs.], in Alaskan Sci. Conf., 12th, College 1961, Agency standards has been found in the frac Proc.: Sci. Alaska 1961, p. 133-134. tured rock aquifer in scattered areas of the up WEST-CENTRAL ALASKA lands. Transitions between areas of con taminated ground water and areas of uncontam- Juxtaposed continental and oceanic-island arc inated ground water are commonly abrupt and terranes in the Medfra quadrangle, west-central occur over a distance of less than 100 m in some Alaska places. Five test wells were drilled in areas of ar By William W. Pattern, Jr. senic-contaminated ground water. Packer tests indicate that some arsenic-contaminated wells Recent geologic mapping in the Medfra quad receive water from two or more discrete zones rangle has revealed the presence of two markedly within the schist. In some cases it is possible to different geologic terranes (fig. 20). The Nixon seal those zones that produce arsenic-rich water Fork terrane, which characterizes the eastern and to develop a water supply of acceptable qual and central parts of the quadrangle, is composed ity and quantity. of a thick sequence of lower Paleozoic carbonate rocks overlain by upper Paleozoic and Mesozoic Geohydrology of the Delta-Clearwater area quartz-carbonate terrigenous deposits. The In- By G. L. Nelson noko terrane, which underlies the northwestern part of the quadrangle, is made up of upper Pa Three test wells were drilled in the State of leozoic and Mesozoic radiolarian chert and mafic Alaska Delta Barley Project area (fig. 2, area 7). volcanic and volcaniclastic rocks. The two ter Permafrost thickness ranged from 15 to 17 m in ranes appear to be in fault contact along a promi the test wells; the static water level is below the nent topographic lineament that parallels the base of the frozen ground. Susulatna River valley. Upper Cretaceous and Large quantities of water are discharged from Tertiary(?) sedimentary and volcanic strata the springs which feed Clearwater, Sawmill, and overlap both terranes, suggesting that structural Granite Creeks, Clearwater Lake, and the Tan- juxtaposition occurred prior to middle Creta ana River, northeast of Delta Junction. In Sep ceous time. tember 1977, discharge at the Clearwater Creek The Nixon Fork terrane is well exposed in the gage and the outlet of Clearwater Lake totaled Medfra quadrangle and can be traced by scat 34.5 m3/s. Records at the Clearwater Creek gage, tered exposures southward across the Michu- maintained from May to October 1977, show a mina lowlands and Farewell fault to the Lime gradual gage-height rise of 8.5 cm during this pe Hills. The stratigraphic sequence, which clearly riod; gage-height began to decline in October. has continental affinities, includes an estimated The maximum gage-height rise due to rainfall 1,500 to 3,000 m of shallow-water, fossiliferous runoff was 1.8 cm. In July, a discharge of 20.5 limestone and dolomite of Ordovician, Silurian, B-38 beds of impure chert at five localities within this ^Susulatna belt. Unit 3 makes up the bulk of the Cripple Innoko f lineament Creek Mountains along the western border of the / quadrangle and appears to overlie unconforma terrane / bly units 1 and 2. It is composed of a thick se quence of tuff, volcanic sandstone, and volcanic N5^ conglomerate within which were found Inocera- mus fragments of probably Early Cretaceous age. The areal extent of the Innoko terrane beyond the Medfra quadrangle is uncertain, but recon naissance mapping by R. M. Chapman (oral commun., 1977) suggests that it can be traced 15 km northeastward into the Ruby quadrangle and X X X X X at least 40 km southwestward into the Ophir quadrangle. 156 REFERENCES CITED Mertie, J. B., Jr., and Harrington, G. L., 1924, The Ruby- FIGURE 20. Map of Medfra quadrangle showing areas un Kuskokwim region, Alaska: U.S. Geol. Survey Bull. 754, derlain by Nixon Fork and Innoko terranes. 129 p. Patton, W. W., Jr., Dutro, J. T., Jr., and Chapman, R. M., and Devonian age and 300 to 500 m of highly fos- 1977, Late Paleozoic and Mesozoic stratigraphy of the siliferous limy sandstone, sandy limestone, con Nixon Fork area, Medfra quadrangle, Alaska, in Blean, glomerate, and spiculite of Permian, Triassic, K. M., ed., United States Geological Survey in Alaska; and Early Cretaceous age (Patton and others, accomplishments during 1976: U.S. Geol. Survey Circ. 1977). At the north edge of the Medfra quadran 751-B, p. B38-B40. gle, this sequence rests unconformably on a Preliminary summary of the geology in the north metamorphic complex of probable Precambrian west part of the Ruby quadrangle age. By Robert M. Chapman and William W. Patton, Jr. The previously poorly known Innoko terrane is characterized by an assemblage of chert and vol Reconnaissance geologic mapping of the area canic rocks that appears to have oceanic or is north of the Yukon River in the Ruby quadran land-arc affinities. Mertie and Harrington (1924) gle was completed in 1977 by R. M. Chapman assigned this assemblage a Mesozoic age, but re and W. W. Patton, Jr. A preliminary geologic cent mapping by Patton and radiolarian and map of the area is shown in figure 21; as office conodont studies by D. L. Jones and Brian and analytical studies are still in progress, this Holdsworth have established that it includes report includes only brief descriptions of the ma rocks at least as old as Mississippian. Structural jor rock units and more significant discoveries. complications and poor exposures preclude a de This area is situated on the southeast border of tailed stratigraphic breakdown of the assem the Yukon-Koyukuk basin and includes both blage, but three gross lithologic units are Cretaceous rocks of the basin and pre-Creta- mappable. Unit 1, composed of varicolored bed ceous rocks of the borderland. It is bounded on ded chert with scattered thin lenticular bodies of the south by the Kaltag fault (Patton, 1973). The limestone, crops out in the extreme northern cor rock units are correlative with units in the Melo- ner of the quadrangle where it forms a 15-km zitna quadrangle just to the north (Patton and wide, northeast-trending belt. Radiolarians and others, 1978), and the same structural trends conodonts of Mississippian age have been identi prevail. fied at eight widely scattered localities along this The gneissic rocks (fig. 21), which form most of belt. Unit 2, made up chiefly of tuff, volcanic the highest part of the Kokrines Hills, are chiefly conglomerate, breccia, and basalt, forms a north garnetiferous quartz-feldspar-biotite gneiss of east-trending, 10-km-wide belt bordering the almandine-amphibolite facies, but include some upper Susulatna River. Radiolarians of Triassic quartzitic gneiss, amphibolitic gneiss, migmatite, age have been recovered from thin intercalated small bodies of marble, and a few small bodies of B-39 the unit of basalt, diabase, chert, tuff, and schis tose greenstone at the north edge of the map area. A Lower Cretaceous unit of probably Neoco mian age, previously unknown along the south eastern margin of the Yukon-Koyukuk province, was found on the Melozitna River 6 km north of its mouth. This unit, at least 300 m thick, con sists primarily of andesitic flows, but also in

EXPLANATION cludes some volcaniclastic and fine-grained tuffaceous rocks, and shaly sedimentary rocks. Unconsolidated Landslides Andesitic to basaltic volcanic and interlayered deposits large/small conglomeratic sedimentary rocks on a hilltop on the east side of the Melozitna River and 10 km Sandstone, quartz conglomerate, siltstone, and shale; non-marine north of the mouth may also be part of this unit. (probably Late Cretaceous) This unit is similar to the Lower Cretaceous (Neocomian) unit of andesitic volcanic rocks ex

Volcanic graywacke and mudstone posed over 60 km to the north in the Melozitna (probably late Early Cretaceous) Hornfelsic zone shown by triangles quadrangle (Patton and others, 1978). A few fos sil ferns, collected in 1977 from the section on the Granitic rocks Melozitna River, are not well enough preserved (probably Early and Igneous pebble conglomerate Late Cretaceous) (probably late Early Cretaceous) to demonstrate details of venation or other spe cific characters, but the size and shape of the pin- ules conform quite nicely with those of the genus Andesitic volcanic rocks (Early Cretaceous, probably Cladophlebis, which is common in the Mesozoic; Neocomian) also these specimens do not resemble any ferns known in the North American Permian (S. H. Ultramafic rocks Mamay, written commun., 1977). Ferns of this genus have been found in rocks of late Early Cre

Basalt, diabase, chert, tuff, taceous (Albian) or Late Cretaceous age about 32 and schistose greenstone km west along the Yukon River (Hollick, 1930, p. 39). The rock assemblage plus the fossil evidence zo Metamorphic rocks strongly favor a Neocomian age for the andesitic unit. A correlation with the basalt, diabase, chert, tuff, and schistose greenstone unit, which Gneissic rocks immediately underlies Cretaceous clastic rocks __»__ __*_ east of the Melozitna River, seems unlikely be Concealed fault Anticline Sync line cause the volcanic rocks in that unit are predomi FIGURE 21. Preliminary geologic map of northwest part of nantly basaltic rather than andesitic and Ruby quadrangle. generally lack a large component of coarse vol granitic rock. The metamorphic rocks include caniclastic rocks. Only late Paleozoic fossils are pelitic schist, quartzite, and calcareous to dolo- known in the basaltic unit farther east along the mitic marble, generally of greenschist facies. The Yukon River valley and to the northeast in the stratigraphic relation between these two units Kanuti River region. and their ages are uncertain. Andesitic rocks were not found elsewhere in The extrusive and intrusive basalt, diabase, this part of the Ruby quadrangle. Apparently chert, tuff, and schistose greenstone probably these rocks are overlapped and concealed by range in age from Permian to Jurassic. The na post-Neocomian conglomeratic rocks to the ture of the contact between this unit and the northeast along the margin of the Yukon-Koyu older rocks is uncertain. A small unit of ultrama- kuk province. fic rocks, largely serpentinized peridotite, to The post-Neocomian Cretaceous clastic rock gether with minor amounts of gabbro, lies within units probably range in age from late Early Cre-

B-40 taceous (Albian) to early Late Cretaceous and 165-km2 area that is 6 to 13 km northwest of the are correlative with similarly designated units in Melozitna River canyon in the Ruby quadrangle. the Melozitna quadrangle. The rocks are only Two more small landslides are present a few kilo moderately deformed by a series of broad anti meters west of this area. Several of the large clines and synclines in which bedding dips rarely landslides were first noted from the air by the exceed 45°. Some crystal-lithic tuff, volcanic writers in 1974. Ground and low-level aerial ob graywacke, and related rocks, resembling those servations and aerial photointerpretation in con in the tuff, volcanic graywacke, and mudstone nection with reconnaissance geologic mapping in unit of the Melozitna quadrangle (Patton and 1977 led to identification of the 26 landslides others, 1978), are included in the three post-Neo- shown in figure 21. With more detailed field- comian units shown in figure 21. work, probably a few more small landslides could The granitic rocks have not yet been studied be found northwest of the Melozitna River and petrographically or dated; quartz monzonite, also in the hills between the Yukon River and granite(?), and granodiorite that are probably Bear Creek. Early and Late Cretaceous age are included. The The large landslides, six of which face south, pluton in the Kokrines Hills is chiefly quartz descend from altitudes of 610-700 m at the heads monzonite and is part of the large Melozitna plu of small stream valleys and range from 0.8 to 1.4 ton that has yielded a potassium-argon age of 111 km in width at the head and from 0.8 to 1.6 km in m.y. (Patton and others, 1978). A small linear length from crown to toe. They apparently body of deeply weathered granite or quartz mon formed as rotational slumps that grade to debris zonite, including xenoliths of mafic rock, is ex slides and earthflows in the lower parts. The posed over a distance of 5 km in the Melozitna slide material consists of bedrock slump blocks River canyon. A granodiorite stock, at the west and bedrock debris from the Cretaceous clastic edge of the map area, has intruded and altered rocks. The headward part of a large landslideis volcanic graywacke and mudstone of probable shown in figure 22. A few tiny lakes occupy shal Albian age to hornfels. Similar granodiorites in low depressions in three of the slides. The smal the Melozitna quadrangle have provided potas ler slides include debris slides and some rotation sium-argon ages of 81.5 to 89.0 m.y. (Patton and al and planar slumps and are located both at the others, 1978). heads of valleys and gullies and along side slopes Only the major areas of unconsolidated depos in the upper parts of stream valleys. They gen its are shown (fig. 21). These deposits are chiefly erally descend from an altitude of about 460 m. younger and older flood-plain silt, sand and The landslides are in, or close to, the axial gravel, and colluvial and eolian slope deposits. zones of synclines and an anticline where the Numerous landslide deposits, which lie outside beds generally dip 10° or less and apparently are these areas, are shown by symbols and discussed not deformed by minor folds and faults. In most in the following report. of the slides the rupture planes are nearly normal to the bedding planes, and there is no apparent REFERENCES CITED control by faults, joints, or incompetent stratigraphic units. As shown in figure 21, 24 of the Hollick, Arthur, 1930, The Upper Cretaceous floras of landslides are located along the anticline and Alaska: U.S. Geol. Survey Prof. Paper 159,123 p. syncline that trend northeast from the head of Patton, W. W., Jr., 1973, Reconnaissance geology of the northern Yukon-Koyukuk province, Alaska: U.S. Geol. Bear Creek; the other two landslides are in the Survey Prof. Paper 774-A, 17 p. axial zones of two synclines to the west of these Patton, W. W., Jr., Miller, T. P., Chapman, R. M., and major structures. Yeend, Warren, 1978, Geologic map of the Melozitna Most of the landslides apparently have long quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-1071,1 sheet, scale 1:250,000 (in press). been nearly stable and are thinly to moderately covered by a normal vegetation of brush and Landslides near Melozitna River canyon small trees, except for the nearly barren steep By Robert M. Chapman and W. W. Patton, Jr. main and flank scarps. These slides are probably at least a few thousand years old, and perhaps as Eight large landslides and sixteen smaller ones old as late Pleistocene. Some of the small slides have been mapped within a northeast-trending, may be considerably younger, but none is fresh. B-41 The large landslides superficially resemble cir duced alaskite outcrops to rubble so the true que glacier features and apparently are what Ea- width of the parsonite-bearing material is uncer kin (1916) interpreted as evidence for small tain, but strongly radioactive material occurs glaciers that left only insignificant deposits in scattered over an area about 3 m wide by 20 m the uplands just west of the Melozitna Canyon. long. Radioactivity readings of up to 10,000 cps True cirque glacier features, including bouldery (counts per second) were obtained in this area. till, small moraines, and tarns, are present in sev The parsonite locality noted in this report was eral places 25 to 55 km to the east on the high the only one found during this reconnaissance north slopes of the Kokrines Hills (Eakin, 1916; study. Because of the narrowness of the parson Patton and others, 1978). The cirque glaciers ite-bearing zone, however, detailed and closely were confined to northerly facing valley heads at spaced traversing would be necessary to deter altitudes of 790 to 920 m (2,600-3,000 ft). In con mine whether similar zones exist elsewhere in the trast, the features west of the Melozitna River alaskite. canyon are at lower altitudes, commonly on well- Coarse-grained alaskite underlies the west end exposed south-facing slopes, and include de of the Wheeler Creek pluton and intrudes Lower tached bedrock blocks and modified transverse Cretaceous andesitic volcanic rocks, Upper Cre minor scarps and cracks that are typical of land taceous rhyodacite hypabyssal rocks, and the slides. Upper Cretaceous porphyritic quartz monzonite of the Wheeler Creek pluton (Miller, 1970). The REFERENCES CITED area underlain by alaskite (approximately 100 km2) is characterized by rounded pink-colored Eakin, H. M., 1916, The Yukon-Koyukuk region, Alaska: U.S. Geol. Survey Bull. 631, 88 p. hills covered with a thick mantle of gruslike ma Patton, W. W., Jr., Miller, T. P., Chapman, R. M., and terial through which scattered outcrops pro Yeend, Warren, 1978, Geologic map of the Melozitna trude. The alaskite itself is a massive rock quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. characterized by large (up to 10 mm) black Map 1-1701,1 sheet, scale 1:250,000 (in press). smoky quartz anhedra in a setting of pink feld An occurrence of parsonite, a secondary uranium spar anhedra. The abundance of black smoky mineral, in alaskite of the Wheeler Creek pluton quartz gives the rock the superficial appearance By Thomas P. Miller and Bruce R. Johnson of being quite mafic, but it is a true alaskite with generally less than 1 percent mafic minerals, al Reconnaissance investigations in the Purcell though locally near the contacts the mafic min Mountains (fig. 23) in 1977 revealed the presence eral content may be as high as 8 percent. Large of parsonite, a hydrous phosphate of lead and clusters of black smoky quartz, purple amethyst uranium with the formula Pb2UO2 (PO4)2 2H2O. crystals (individual crystals as much as 100 mm This is the first reported occurrence of parsonite long), and white quartz crystals (as large as 250 in Alaska although other uranium phosphate mm) are found locally in the grus mantle and minerals have been reported elsewhere, for ex probably represent the weathered remnants of ample at Bokan Mountain in southeastern large quartz-filled vugs and miarolitic cavities. Alaska (MacKevett, 1963). Parsonite has pre The alaskite is composed mainly of potassium viously been reported (Rich and others, 1977) at feldspar, chiefly patch perthite with minor such hydrothermal uranium deposits as those in amounts of albite and abundant quartz. Biotite the two-mica granites of the Limousin region of is the principal mafic mineral, but hornblende west-central France, the uraniferous granites of occurs locally near the contact with country rock; central Portugal, and the Shinkolobwe deposit of magnetite and less commonly allanite are acces Zaire. sory minerals. A potassium-argon age measure The parsonite occurs as a soft, yellow to choco ment of 77.9 ± 2.3 m.y. (Late Cretaceous) has late brown coating closely associated with green been obtained on biotite from the alaskite muscovite on fracture surfaces in a shear zone in (Miller, 1970). alaskite of the Wheeler Creek pluton (fig. 23). High radioactivity readings ranging from 400 Thin magnetite veinlets are also present. The to 600 cps on a hand-held scintillometer were ob identification of parsonite was confirmed by tained over the alaskite. Delayed neutron analy X-ray diffraction. Intensive frost action has re ses of two samples of typical alaskite show 14.4

B-42 FIGURE 22. Headward part of a large landslide north of Melozitna River canyon. ppm and 13.4 ppm uranium and 52.3 and 45.2 TABLE 2. Delayed neutron determinations of uranium ppm thorium, respectively (table 2). Eakins and thorium, in parts per million, of selected grab sam ples, Wheeler Creek pluton (1977) reported anomalous amounts of uranium in stream sediment samples collected from [Analysts: H. T. Millard, Jr., C. M. Ellis, C. McFee. CV, coefficient of variation, or one standard deviation, streams south and east of the parsonite locality. based on counting statistics, expressed as percentage Delayed neutron analyses were also run on two of concentration. Concentrations with CV > 30 percent are enclosed in parentheses and should not be con samples of altered alaskite from the parsonite- sidered reliable] bearing zone. A fist-size grab sample of altered alaskite with a visible coating of parsonite along Lab No. Uranium CV Thorium CV Remarks one side yielded 4,459 ppm uranium (No. 3, table D186403 14.42 1 52.27 4 Typical alaskite 2); laboratory radioactivity readings of 1,600 cps D186404 13.43 2 45.14 4 Typical alaskite were obtained from a hand-held scintillometer D195038 4459.08 1 (565.97) 64 Altered alaskite with abundant on the side containing parsonite. A sample of visible parsonite similar size containing little or no visible parson D195039 881.12 1 (0.00) 50 Altered alaskite ite (No. 4, table 2) yielded 881 ppm uranium. It is with little or no uncertain whether other uranium-bearing min visible parsonite erals besides parsonite are present; however, those samples containing visible parsonite emit alaskite or the possibility of more widespread ted by far the highest radioactivity. Uranium secondary enrichment of the uraniferous alas analyses of individual grab samples, therefore, kite. probably are a reflection of the parsonite content. REFERENCES CITED The original source of the uranium in the par sonite is unknown. The occurrence of an oxidized Eakins, G. R., 1977, Reconnaissance program, west-central uranium mineral associated with a shear zone in Alaska and Copper River Basin, Part 1, in Investigation of Alaska's uranium potential: U.S. Energy Research the uraniferous alaskite certainly indicates sec and Development Admin. Rept. GJO-1639, 51 p. ondary concentration of uranium. The parsonite, MacKevett, E. M., Jr., 1963, Geology and ore deposits of the therefore, may indicate the possible occurrence Bokan Mountain uranium-thorium area, southeastern of primary uranium minerals elsewhere in the Alaska: U.S. Geol. Survey Bull. 1154,125 p.

B-43 Rich, R. A., Holland, H. D., and Petersen, Ulrich, 1977, Hy- drothermal uranium deposits: New York, Elsevier Sci. Pub. Co., 264 p.

Tin-granites of Seward Peninsula By Travis Hudson, Fred Barker, and Joseph Arth

Brief field studies of the granite plutons of Seward Peninsula that are spatially associated -66°15' with tin mineralization were completed during July 1977. These studies were undertaken to identify the general petrologic nature of the plu tons and to obtain representative samples of lithologic facies in them. The samples were collected for petrologic, chemical, and isotopic laboratory studies directed toward understanding the origin of the parent magmas. Altogether, seven granite stocks of northwestern Seward Peninsula and the northern part of the Darby batholith in east ern Seward Peninsula were sampled (fig. 24). 157°00' The field studies revealed the following gen eral relations: 1. Tin-granite complexes at Cape Mountain, Brooks Mountain, and Ear Mountain are

EXPLANATION composite epizonal stocks similar to the gran ite complex of the Serpentine Hot Springs | Qfp | area (Hudson, 1977) in that they contain seri- Floodplam deposits ate-textured biotite granite and porphyritic | Qae | |Qga | biotite granite with aplitic to fine-grained Alluvial and eolian deposits Glacial drift and alluvium equigranular groundmass. Late-stage fine- to medium-grained equigranular intrusions are Alaskite ol the Porphyritic quartz monzomte Wheeler Creek pluton of the Wheeler Creek pluton present at Cape Mountain and Ear Mountain. 2. Tin-granite plutons at Lost River, Tin Creek, Hypabyssal lelsic and Black Mountain contain equigranular volcanic rocks biotite granite. The Lost River and Tin Creek I Kg. \ | Kg, | Quartz monzomte of Monzonite ol Hawk Purcell Mountain pluton River pluton 168°

arsonite locality Thermal springs Glacial morraine Fault

FIGURE 23. Generalized geologic map of the western Purcell Mountains. Modified slightly from Patton, Miller, and Tailleur (1968).

Miller, T. P., 1970, Petrology of the plutonic rocks of west- central Alaska: U.S. Geol. Survey Open-File Report, 132 p. Patton, W. W., Jr., Miller, T. P., and Tailleur, I. L., 1968, Regional geologic map of the Shungnak and southern FIGURE 24. Location of Seward Peninsula tin-granites. part of the Ambler River quadrangles, Alaska: U.S. 1. Cape Mountain 2. Brooks Mountain 3. Lost River 4. Tin Geol. Survey Misc. Geol. Inv. Map 1-554, scale Creek 5. Black Mountain 6. Ear Mountain 7. Serpentine 1:250,000. Hot Springs X. NorthernDarby Mountain batholith. B-44 plutons may be similar to late-stage fine- to Chert, with associated bedded sedimentary medium-grained equigranular granite intru rocks, occurs in at least three thin zones, less sions at Cape Mountain, Ear Mountain, and than 200 m thick, interbedded with the Kobuk in the Serpentine Hot Springs area. volcanic sequence, which trends east-west and 3. The Darby batholith is composite and con has an outcrop width of about 5 km in the Help- tains late intrusions of porphyritic biotite mejack Hills. Patton and Miller (1966) mapped granite with aplitic to fine-grained equigranu these hills as altered mafic volcanic rocks of Ju lar groundmass. This facies appears to be rassic age. The volcanic rocks are predominantly similar to major parts of the Cape Mountain, massive to pillowed basalt and basaltic breccia Brooks Mountain, and Serpentine Hot that have been slightly to strongly altered to Springs granite complexes of northwestern greenstone. Dips are generally more than 60° Seward Peninsula. The presence of placer cas- and, in the one locality where tops could be siterite on Otter Creek (Herreid, 1965, p. 5), determined from pillow structures, they face high concentrations of tin in lead-silver de south. The predominantly volcanic sequence is posits of the Omilak area (Mulligan, 1962), bounded on the north by a unit of undifferenti- and the apparent similarity of parts of the ated chloritic phyllite, quartz-mica schist, and northern Darby batholith to parts of some quartzite of possible Devonian age, and on the northwestern Seward Peninsula tin-granite south by Cretaceous conglomerate (fig. 25). complexes suggest that undiscovered lode tin Structural relations between bedrock units were deposits may be present in the northern not determined during our brief reconnaissance Darby Mountains. study, but structure appears to be complex, and Laboratory studies of representative samples the volcanic sequence may be cut by one or more of the exposed granites have begun. These stud thrust faults. ies should clarify important similarities or differ Age-diagnostic radiolarians were collected ences between the several plutons and add to our from cherts at two of the three field stations at understanding of the origin of the parent which sedimentary rocks were found within the magmas. Kobuk volcanic sequence (fig. 25). These sedi REFERENCES CITED mentary units underlie broad saddles in the to pographically rugged volcanic terrain. At station Herreid, Gordon, 1965, Geology of the Omilak-Otter Creek 77APr91 a band of gray, green, black, and white area, Bendeleben quadrangle, Seward Peninsula, Alas radiolarian-rich ribbon chert, approximately 50 ka: Alaska Div. Mines and Minerals Geol. Report 11, m thick, apparently overlies and is possibly in 12 p. tercalated with greenstone breccia along the Hudson, Travis, 1977, Genesis of a zoned granite stock, Sew ard Peninsula, Alaska: U.S. Geol. Survey Open-File Re southern margin of the saddle. The main part of port 77-35,188 p. the saddle to the north in underlain by thin, dis Mulligan J. J., 1962, Lead-silver deposits in the Omilak area, continuous limestone lenses containing poorly Seward Peninsula, Alaska: U.S. Bur. Mines Report Inv. preserved megafossils within a sequence, roughly 6018,44 p. 150 m thick, of green tuff, black phyllite, and gray volcanogenic sandstone. The geologic rela Upper Triassic radiolarian chert from the Kobuk volcanic sequence in the southern Brooks Range tions between the cherty rocks and the bedded By George Plafker, Travis Hudson, and D. L. Jones fossiliferous sedimentary and volcanic rocks are not known because the contact is not exposed. During the course of reconnaissance field stud The abrupt lithologic change, however, suggests ies of the Kobuk fault zone, age-diagnostic radio that it is a fault. At station 77APr89 a poorly ex larian cherts were collected from an unnamed posed sequence of thinly bedded reddish-brown, sequence of predominantly mafic volcanic rocks green, gray, black, and white chert with moder that forms a discontinuous belt along much of ately abundant radiolarians occurs as rubble or is the southern foothills of the Brooks Range. The discontinuously exposed in a few riblike out cherts were collected at two localities from this crops, as much as 2 m thick, within a saddle ap sequence of rocks, informally referred to herein proximately 200 m wide. Although float of chert as the Kobuk volcanic sequence, in the Helpme- and limestone was observed at the saddle in the jack Hills in the Hughes quadrangle (fig. 25). basaltic terrane at station 77APr90, the chert did B-45 i54°00' 67°00

Bose from USGS Hughes quodrongle, scale U250.0OO

FIGURE 25. Map showing Upper Triassic radiolarian chert (77APr89, 77APr90, 77APr9lA) and Carboniferous megafossil (77APr9lC) localities within the Kobuk volcanic sequence. Dp, Devonian(?) metamorphic rocks; Kc, Cretaceous conglomerate; Q, unconsolidated Quaternary deposits; uv, undifferentiated mafic volcanic rocks; s, chert-bearing sedimentary rocks; Is, lime stone. Geology modified from Patton and Miller (1966).

not contain megascopically visible radiolarians ments are also present. The radiolarians are and was not sampled. similar to dated Triassic faunas known from Sample 77APr89A from station 89 yielded ra Baja California, central Oregon, and elsewhere diolarians of Late Triassic age, including: Pseu- (E. A. Pessagno, Jr., oral commun., 1977). The doheliodiscus sp., Crucella sp., "Eptingium," chert at locality 77APr91A contains only poorly and Tripocyclia sp. (fig. 26). Conodont frag preserved nasselarian dictyomitrid cones and B-46 diometric ages of igneous rocks thought to be part of the sequence. The basaltic rocks associ ated with the radiolarian cherts were originally assigned a probable Jurassic age by Patton and Miller (1966), but they are now considered by Patton, Tailleur, Brosg£ and Lanphere (1978) to be of probable late Paleozoic age. Our data indi cate that, although late Paleozoic fossils do occur in the terrane, at least part of the Kobuk volcanic sequence is of Late Triassic age. These new data provide important constraints on the age of oce anic rocks that constitute the Kobuk volcanic se quence, on correlations of this sequence with ophiolites elsewhere in northern and central Alaska, and on the history of accretion of these oceanic rocks to the continental margin.

REFERENCES CITED

Patton, W. W., Jr., and Miller, T. P., 1966, Regional geologic map of the Hughes quadrangle, Alaska: U.S. Geol. Sur vey Misc. Geol. Inv. Map 1-459,1 sheet, scale 1:250,000. FIGURE 26. Pseudoheliodiscus sp. from sample 77APr89. Patton, W. W., Jr., Tailleur, I. L., Brosge, W. P., and Lan This radiolarian is similar to Late Triassic (Norian) forms. phere, M. A., 1978, Preliminary report on the ophiolites of northern and western Alaska, in Coleman, R. G., and Irwin, W. P., eds., North American ophiolites: Oregon can be dated only as Mesozoic. The radiolarians State Dept. Geology and Mineral Industries Bull. 95, are the only datable fossils that have been ob p. 51-58. tained from the pelagic sedimentary rocks interbedded with the Kobuk volcanic sequence, and Kigluaik and Bendeleben faults, Seward Peninsula they should provide the best available control on By Travis Hudson and George Plafker the age of that part of the terrane in which they occur. The Kigluaik and Bendeleben faults, located The megafauna in sample 77APr9lC from the in south-central Seward Peninsula, together de north side of the saddle at station 91 contains a fine a normal fault system that is about 175 km fossil coral that is probably Diphyllum sp., which long (fig. 27). The two faults are 65 and 90 km is definitely Carboniferous, and probably assign long respectively, trend approximately east- able to the Meramecian Provincial Series of the west, are subparallel but not overlapping, and Mississippian (A. K. Armstrong, written com- have opposite senses of displacement. Displace mun., 1977). The occurrence of upper Paleozoic ments along these faults are responsible for im shallow-water rocks in close association with portant late Cenozoic regional geomorphic and Mesozoic pelagic cherts suggests that the rocks structural relations on Seward Peninsula; sur have been structurally juxtaposed. face features indicative of Holocene displace The mafic volcanic sequence from which the ment are present. Surface features along the radiolarians were obtained is considered by Pat- faults were studied in the field during July 1977 ton, Tailleur, Brosge and Lanphere (1978) to be as part of the Alaska Geologic Earthquake Haz part of an extensive ophiolite terrane in northern ards Project in order to understand better the re Alaska which has been termed the Yukon-Koyu- cent displacement history of the faults and to kuk ophiolite belt. Previous interpretations of clarify further the regional tectonic setting of the the age of the Kobuk volcanic sequence in this fault system. belt have been based on sparse megafossils and The Kigluaik fault marks the abrupt northern foraminifers obtained from limestone lenses or boundary of the rugged Kigluaik Mountains. blocks occurring within the sequence or from ra- Along its central part the fault separates the B-47 166° 166° 164° 163° 162°

^tt^Pr^- #tf£3fcNfefc."J* ^M xL^r^N i ! n^%^ 2 /S >*^^ !_ liy *.. JiV' x A-'i-' 0-a\' f -"<' '' ^S^AI jzo" ' ->,J>T TO.. ^' ' \ I /! ' .^fcJCI ' - L* FAlJL'f^/-^4j: ^S iJv;

FIGURE 27. Location of the Kigluaik and Bendeleben faults, Seward Peninsula, Alaska. Hachured where fault well defined by surface features; dashed where poorly defined; queried where inferred. Letters indicate segments discussed in text. Axis of Kigluaik-Bendeleben-Darby Mountains shown by dash-dot line.

mountains from the adjacent lowlands of Imuruk ment is present between major morainal ridges Basin. The fault is consistently down to the in the headwaters of White River. At the slope- north and has a slightly convex northward orien breaks along the fault trace, surface slopes in lat tation except near its western limit where it eral moraine are as steep as 17°. Maximum changes strike to a northwesterly direction. vertical separations range from 4 to about 10 m. Some surface features and geologic relations Because these separations are measured in the along the fault are summarized separately below oldest (highest) lateral moraines along this seg for the western, central, and eastern segments. ment, they probably are a reasonable measure of Along the western segment of the Kigluaik total post-Wisconsin displacement along the fault (segment a, fig. 27), the surface trace is fault. marked by distinct slopebreaks in bedrock The central segment of the Kigluaik fault (seg ridges, mantled by lateral moraine, that trend ment b, fig. 27) has a surface trace that is very northerly, parallel to major glaciated valleys. well defined and abruptly separates alluvial, col- Where exposed, bedrock on both sides of the luvial, and morainal deposits of Imuruk Basin to fault is biotite-feldspar-quartz schist with some the north from amphibolite-facies biotite-quartz granitic dikes and sills. Foliation in the bedrock and biotite-graphite-quartz schist to the south. is approximately parallel to the fault except west Foliation in the schist strikes parallel to the fault of Martha Creek, where the fault apparently dies and dips about 60° N. A scarp as much as 4 m out near the Nome-Teller road. The bedrock high is nearly continuous along the western part ridges are mostly mantled by lateral moraine, of this segment where bedrock is juxtaposed and the fault transects them at elevations com against unconsolidated late Quarternary depos monly greater than 305 m and as high as 490 m. its including small sharp-crested lateral mo The most prominent lateral moraines are raines that extend northward from the mouths of smooth, moderately sharp crested, and sparsely steep and narrow valleys. Along the eastern part vegetated, and contain fresh boulders of meta- of the segment, the fault transects extensive morphic and plutonic rocks; they are probably morainal deposits of the Cobblestone River val Wisconsin in age. In some places where the fault ley; the scarp is as much as 6.2 m high in the trace crosses ridges, a moderately broad notch or highest lateral moraines just east of the valley swale is developed at the base of the slopebreak. (elevation about 230 m). Total post-Wisconsin There is usually no distinct fault trace along the displacement may be between 4 and 7 m along floors of the glacial valleys, but one sharp escarp this segment. B-48 The eastern segment of the Kigluaik fault evident in the alluvial deposits of the main val (segment c, fig. 27) is less well defined than seg leys the age of recent surface features along ments farther west. For about 18 km east of the this segment is not known. headwaters of Grand Union Creek, the mountain The central segment of the Bendeleben fault front is abrupt and characterized by complex (section b, fig. 27) is characterized by a discon morainal deposits at the mouths of moderate- tinuous scarp and separates the Bendeleben size glacial valleys. These morainal deposits have Mountains from the lowlands of the upper Fish irregular surfaces and are banked up against River drainage system (McCarthy's Marsh). The metamorphic and granitic bedrock of the moun scarp is most evident between the valleys of Ba tain front. Lateral moraine thinly caps some bed ker Creek and Lava Creek. It is developed in col rock ridges south of the fault, but most of the luvium, moraine, and the bedrock of the morainal deposits lie north of and adjacent to the mountain front, but does not transect the youn fault. The irregular and youthful glacial deposits, ger alluvial fans and stream deposits. The scarp some of which are probably late Wisconsin, ob ranges in height from about 2 m to more than 8 m scure this segment of the fault trace. Neverthe and becomes more degraded with increasing less, the trace is reasonably well defined by height. slopebreaks and notches in morainal ridges and The eastern segment of the Bendeleben fault colluvium along the mountain front. East of Pass (section c, fig. 27) crosses, at almost right angles, Creek the mountain front shifts northward in the main axis of the Bendeleben and Darby two en echelon steps from the main trace of the Mountains (fig. 27). The surface trace is similar fault, which apparently dies out in bedrock a few in general features to the western segment of the kilometers east of Pass Creek. The east end of fault and is marked by discontinuous slope- the Kigluaik fault thus appears to be an en eche breaks, benches, and saddles in colluvium over lon system of at least three faults that mark the lying bedrock. Bedrock north of the fault northern front of the mountain range. The two includes foliate granodiorite and amphibolite- supposed en echelon members northeast of the facies gneissic schist and biotite-quartz schist, main trace do not have surface features clearly whereas south of the fault bedrock includes epi- indicative of young displacement; the first marks zonal to hypabyssal felsic intrusive rocks and a moderately abrupt mountain front, whereas slaty to schistose metasedimentary rocks. My- the second is more subdued. The general geo- lonitized granodiorite and porphyry are juxta morphic features suggest that displacement of posed at one locality. This segment is not known western en echelon fault segments is younger to displace moraine or alluvium, but east of the than on eastern segments. axis of the Bendeleben and Darby Mountains it The Bendeleben fault extends from near Mt. approximately defines the topographic break be Bendeleben eastward to the headwaters of the tween the Bendeleben Mountains and the allu- Tubutulik River along the south flank of the viated lowlands of Death Valley. No surface Bendeleben Mountain (fig. 27). The fault is con expression of the fault was observed east of the sistently down to the south and has a generally eastern most Bendeleben Mountains. convex southward surface trace with local shifts In summary, the Kigluaik and Bendeleben in strike, particularly along the central part. faults are major normal faults that are about 65 Some surface features and geologic relations and 90 km long, respectively, have opposite along the fault are outlined below for the west senses of displacement but do not overlap, and ern, central, and eastern segments. together define a fault system about 175 km long. The western segment of the Bendeleben fault Both apparently die out in bedrock at their east (section a, fig. 27) has a surface trace marked by ern and western terminations, and both have slopebreaks, scarps, and saddles in colluvium surface features indicative of Holocene dis overlying bedrock. Bedrock includes a variety of placement that are best developed along their metasedimentary rocks, but lithologic contrasts central parts. Late Cenozoic displacement along are common across the fault and small granitic these faults is largely responsible for develop intrusions are mostly on the north side. Slope- ment of the higher and more rugged parts of the breaks and scarps are locally degraded and as Kigluaik and Bendeleben Mountain ranges and much as 4 m high. No distinct surface trace is the adjacent lowlands that represent sedimen-

B-49 tary basins (Barnes and Hudson, 1977). Total Preliminary investigations of coal outcrops near Farewell, Alaska post-Wisconsin displacement may be about 6 to By Ernest G. Sloan, Gerald B. Shearer, James 7 m on the central Kigluaik fault and about 8 m Eason, and Carl Almquist on the central Bendeleben fault. The Kigluaik and Bendeleben faults are the The purpose of this reconnaissance investiga principal active faults of Seward Peninsula and tion is to determine the extent and quality of coal have large amounts of late Cenozoic dip-slip dis cropping out along the north front of the Alaska placement. Other normal faults with sizeable Range between Big River and the boundary of late Cenozoic displacement are associated with Mount McKinley National Park (area 8, fig. 2). uplift of the Kigluaik, Bendeleben, and Darby Most of the area is covered with coarse granular Mountains (Hudson, 1977; Barnes and Hudson, sediments deposited unconformably over sedi 1977), but surface features indicative of recent mentary rocks of Tertiary age. Rare bedrock out movements have not been identified along them. crops occur in river bluffs and small stream It appears that the Kigluaik and Bendeleben valleys where the surficial deposits have been faults are the most recently active of many major eroded sufficiently to expose the underlying bed Seward Peninsula faults. These faults, together rock. Outcrops of coal were found in exposures with offshore faults west of Teller (Sainsbury, along the little Tonzona River, the upper tribu 1972) and west of Cape Krusenstern in the Chuk tary creeks (unnamed) of Deep Creek, and along chi Sea (Ettreim and others, 1977), serve to iden Windy Fork of the Kuskokwin River. Thin, dis tify a broad region of major late Cenozoic normal continuous beds of coal were found along the Big faulting. This region is also characterized by River. widespread late Cenozoic basaltic volcanism Twelve seams of coal at least 1 m thick crop (Hudson, 1977) and is considered to reflect a re out along the Little Tonzona River in sec. 27, T. gional stress regime that is characterized by 31 N., R. 20 W., Seward Meridian. These coal north-south extension. The areal extent of this seams range in thickness from 1.0 to 7.9 m and regime and the history of faulting within it are total 40.3 m of coal in an 85-m outcrop. Beds not well known. Some of the late Cenozoic basal strike N. 73° E. and dip 47° to 63° northwest. A tic volcanic rocks of Seward Peninsula that are 6.3-m coal seam striking N. 50° E. to N. 60° E. presumably related to extensional tectonics are and dipping 48° to 55° west crops out in sec. 13, as old as 5.7 m.y. (Hopkins and others, 1971), T. 30 N., R. 20 W., Seward Meridian, on the bank which suggests that development of the present of an unnamed tributary of Deep Creek. Nine stress regime began at least as early as the late coal seams more than 1 m thick crop out on Miocene. Windy Fork in sec. 19, T. 27 N., R. 26 W., Seward Meridian. These seams range in thickness from 1 to 10.5 m and total 32.9 m of coal in an 83.6-m REFERENCES CITED outcrop section. Beds strike N. 23° E. to N. 30° W. and dip 37° to 40° south. The measured out Barnes, D. F., and Hudson, Travis, 1977, Bouguer gravity crop is part of the southern limb of a syncline map of Seward Peninsula, Alaska: U.S. Geol. Survey Open-File Report 77-796-C, scale 1:1,000,000. that trends through the area. Ettreim, Steven, Grantz, Arthur, and Whitney, O. T., 1977, Proximate and ultimate analyses and tests of Tectonic imprints on sedimentary deposits in Hope ba physical properties are being conducted on chan sin, in Blean, K. M., ed., The United States Geological nel samples of the coal. Survey in Alaska; accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B100-B103. SOUTHWESTERN ALASKA Hopkins, D. M., Mathews, J. O., Wolfe, J. A., and Silberman, M. L., 1971, A Pliocene flora and insect fauna from the New geologic map of the Goodnews-Hagemeister Bering Strait region: Paleogeography, Paleoclimato- Island quadrangles region, Alaska logy, Paleoecology, v. 9, p. 211-231. By J. M. Hoare and W. L. Coonrad Hudson, Travis, compiler, 1977, Geologic map of Seward Peninsula, Alaska: U.S. Geol. Survey Open-File Report A new geologic map covering an area of about 77-796-A, scale 1:1,000,000. Sainsbury, C. L., 1972, Geologic map of the Teller quadran 31,000 km2 in southwestern Alaska has recently gle, western Seward Peninsula, Alaska: U.S. Geol. Sur been compiled at a scale of 1:250,000 (Hoare and vey Map 1-685, scale 1:250,000. Coonrad, 1978) as part of the Alaska Mineral Re-

B-50 source Assessment Program (AMRAP). The Mesozoic rocks could not be differentiated ex map includes the Goodnews and Hagemeister Is cept where they contained fossils. On the new land quadrangles and parts of the adjoining geologic map most of the area previously mapped Bethel, Taylor Mountains, Dillingham, and Nu- in the Gemuk Group is divided into three parts shagak Bay quadrangles. About 75 percent of the and mapped as undifferentiated rocks of Paleo area mapped under the aegis of AMRAP is zoic and Mesozoic age, tuffs and sedimentary shown in figure 28 at a scale of 1:1,000,000; in fig rocks of Early Cretaceous age, and volcanic and ure 29 map units on this small-scale map are de sedimentary rocks of Jurassic and Early Creta scribed. In figure 29 the units are briefly ceous age. Contacts between these units are un described and correlated with map units of the certain and largely interpretive. larger scale map compiled for AMRAP (Hoare A partial list of observations and conclusions and Coonrad, 1978) and with the 1:1,000,000- made during recent geologic mapping includes scale preliminary geologic map of Alaska (Beik- the following: man, 1974). Figure 28 is duplicated for conve (1) Depositional contacts are rare; most con nience as figure 47 at the end of the report. tacts between bedded rocks are faults. Rough reconnaissance geologic maps of most (2) Northeast- and northwest-trending faults of the area had been published previous to this have cut the rocks into many fault slices and work (Hoare and Coonrad, 1959,1961a, b; Mer- fault blocks that range in size from a few hun tie, 1938, pi. 2). During the earlier geologic map dred square meters to several hundred square ki ping, the locations of geologic observations lometers. (except for those of J. B. Mertie) were plotted on (3) Radiometric dating shows that the intru vertical and oblique aerial photographs because sive igneous rocks include layered gabbros and there were no reliable topographic base maps. To ultramafic bodies of Jurassic age, many granitic make the old data useful in the recent investiga stocks of Late Cretaceous and early Tertiary age, tion, all the old observations and structural data a felsic intrusive-extrusive complex of early Ter were replotted on modern l:63,360-scale base tiary age, and felsic dikes and sills of late Terti maps which recently became available. ary age. Additional fieldwork would improve the new (4) The mafic and ultramafic rocks on and geologic map, but it is better than the old maps near Cape Newenham constitute an altered dis because it is plotted on a modern topographic membered ophiolite complex. base and is based on many more field observa (5) Evidence indicating right-lateral move tions and a better geologic understanding. New ment in the Togiak-Tikchik fault zone is pro paleontological data and numerous radiometric vided by horizontal and subhorizontal age dates have established the absolute and rela slickensides developed on shear planes in the tive ages of the rocks with more certainty. The fault zone. The shear planes are exposed in small map has also benefited from interpretation of upslope-facing scarps that are parallel to large aeromagnetic data (Griscom, 1978) that has sup faults within the fault zone. ported, confirmed, and extended geologic inter (6) Conodonts found in some of the lime pretations. stones document the first known occurrence of During earlier investigations about 75 percent Ordovician rocks in the area. Previously, the of the rocks were mapped as the Gemuk Group, a nearest known Ordovician rocks were in the large undifferentiated unit containing volcanic Lime Hills about 250 km to the northeast. and sedimentary rocks ranging in age from Car (7) New collections of Devonian fossils show boniferous through Early Cretaceous (Cady and that limestones of Devonian age are more wide others, 1955, p. 27-34). A major aim of the recent spread than previously known. The Devonian investigation was to subdivide the Gemuk Group limestones, like those of Permian age, are com into smaller map units of more limited lithologic monly tuffaceous and associated with mafic vol character and age range. Very little progress was canic rocks. made in this regard, however, because as the in (8) Atomodesma shell fragments are valuable vestigation progressed, it became clear that the guides to rocks of Permian age because they oc rocks were more intensely deformed than pre cur in a variety of rock types and even tiny frag viously thought and that many Paleozoic and ments are readily identifiable in the field. They

B-51 162° 161° 160° 159°

W en tO

agemeister Island CORRELATION OF MAP UNITS SURFICIAL DEPOSITS QUATERNARY SEDIMENTARY, VOLCANIC, INTRUSIVE ROCKS AND METAMORPHIC ROCKS

$$$& | Pleistocene - QUATERNARY QUATERNARY QTs > Pleistocene or Pliocene f OR TFRTIARY un ffi'llU'Tnl*- } TERTIARY } Kii** ? Lower Tertiary ' TERTIARY 3*$ } TERTIARY AND j?iS& J CRETACEOUS 1 Upper Cretaceous V^ksV; / (Maestrichian?)

1 Upper and Lower CRETACEOUS k^V J Cretaceous liikblli Kts HKcgtr | Lower Cretaceous

rKJvs= \ Lower Cretaceous 1 , CRETACEOUS dd J to Middle Jurassic j1 AND JURASSIC en oo 1 Lower Upper XJk:-: J to Middle Jurassic JURASSIC &JQ&?^ 5«Vjt xV 1 JURASSIC AND '.tf'V?,! I Lower Jurassic

Hv~si*?*>. i!^ :: :MZPZ -..A . Lower Cretaceous . CRETACEOUS ^Tv to Lower Ordovician (?) TO ORDOVICIAN *K"**"*-fcj T~>^ i**^ |p'z' mg:i; 1 PALEOZOIC (?) ] 7/pCk,-) PRECAMBRIAN s YMBOLS

Hnntart --- Fault or fault zone -T-- Thrust fault

FIGURE 28. Generalized geologic map of the Goodnews and Hagemeister Island quadrangles, southwestern Alaska. See figure 29 for explanation. DESCRIPTION OF MAP UNITS

s I ii Jj^SURFICIAL DEPOSITS Oh Ou UNCONSOLIOATEO SEDIMENTARY DEPOSITS

OP SEDIMENTARY, VOLCANIC, AND METAMORPHIC ROCKS 1 * \ Qtb BASALT OF TDGIAK RIVER VALLEY TKv* QTs SEMICONSOLIOATED MARINE BEACH DEPOSITS | TKv TV VOLCANIC ROCKS AND VDLCANOGENIC DEPOSITS-Chiefly andesitic flows and tuff MzPe Ks SEDIMENTARY ROCKS DF SUMMIT ISLAND-Nonmarine conglomerate, sandstone, shale, and carbonaceous mudstone 1 " Kk KUSKOKWIM GROUP-Conglomerate overlain by interbedded graywacke, siltstone, and shale; commonly micaceous; mostly marine Kb GRAYWACKE OF BUCHIA RIDGE-Chiefly interbedded calcareous graywacke, siltstone, and conglomerate with local coquinas of Buchio shells TUFF AND SEDIMENTARY ROCKS-Varied assemblage of andesitic tuff, graywacke, siltstone, impure limestone, and tuffaceous chert; tuff and tuffaceous sedimentary rocks commonly laumontitized GRAYWACKE AND COMGLDMERATE-Marine graywacke, siltstone, and conglomerate; commonly calcareous MzPz VOLCANIC AND SEDIMENTARY ROCKS-Interbedded intermediate to mafic flows, tuff, tuffaceous sedimentary rocks, and argillite; tuffaceous rocks commonly laumontitized GRAYWACKE DF KULUKAK BAY-Chiefly very hard lithic graywacke and siltstone with local conglomerate VOLCANIC AND SEDIMENTARY ROCKS-Mafic flows and breccias interbedded with volcanogenic sedimentary rocks; fractures commonly coated with laumontite II «. >, I MESOZOIC AND PALEOZOIC ROCKS, UNDIVIDED-Widespread marine unit including volcanic rocks, tuffaceous sedimentary rocks, chert, argillite, siltstone, II I graywacke, conglomerate, and limestone VOLCANIC AND SEDIMENTARY RDCKS-Locally differentiated marine unit of chert, tuffaceous cherty rocks, argillite, siltstone, wacke, conglomerate, limestone, and mafic flows and breccia VOLCANIC ROCKS-Locally differentiated marine unit of pillow basalt; massive mafic flows, breccia, and tuff LIMESTONE-Thin-bedded to massive limestone with minor interbedded tuff and mafic flows; locally recrystallized to marble METAMDRPHIC ROCKS OF KANEKTOK RIVER REGION Gneiss, schist, amphibolite, and marble; upper greenschist to lower amphibolite facies INTRUSIVE ROCKS Th Tif FELSIC INTRUSIVE ROCKS-Chiefly rhyolitic to dacitic dikes and sills; locally mapped Tmi Tim MAFIC INTRUSIVE ROCKS-Diabase, basalt, dioritic, and gabbroic dikes and sills locally mapped TKg* Tn IGNEOUS ROCKS DF NAYDRURUN RIVER AREA Quartz-rich porphyritic felsite intrusive-extrusive complex of dikes, sills, tuff, and breccia Tkg TKg GRANITIC ROCKS-Chiefly quartz monzonite, granodiorite, and quartz diorite stocks Tkg* Jg GABBROIC ROCKS-Commonly shows compositional layering Urn | Jum ULTRAMAFIC ROCKS-Serpentinite, dunite, and websterite Tkg* Jt TRONDHJEMITE-Associated with serpentinite and gabbro 1 Pzmg METAGABBRO AND GREENSTONE-Probable dismembered ophiolite complex of mafic flows, dikes, volcaniclastic rocks, and gabbro altered by greenschist MzPz* facies metamorphism and metasomatism * These units previously undifferentiated within map unit indicated

FIGURE 29. Description of map units for the generalized geologic map of the Goodnews and Hagemeister Island quadran gles (fig. 28), southwestern Alaska. B-54 are most common in thin-bedded fetid lime U.S. Geol. Survey Open-File Report 78-9-B, 1 sheet, stones, but also occur as detritus in fine- to scale 1:250,000. Hoare, J. M., Coonrad, W. L., Detterman, R. L., and Jones, coarse-grained clastic rocks including conglom D. L., 1975, Preliminary geologic map of the Goodnews erates. A-2 quadrangle and parts of the A-2 and B-2 quadran (9) The identification of radiolarians in 19 out gles, Alaska: U.S. Geol. Survey Open-File Report 75- of 119 chert collections helped to define some 308,1 sheet, scale 1:63,360. Mesozoic map units. Elsewhere complex struc Mertie, J. B., Jr., 1938, The Nushagak district, Alaska: U.S. ture and the close association of Mesozoic radio Geol. Survey Bull. 903, 96 p. larians and Paleozoic megafossils made it Lawsonite in southwestern Alaska necessary to map Paleozoic and Mesozoic rocks By J. M. Hoare and W. L. Coonrad as one unit. (10) Rocks of Early Cretaceous age and older Lawsonite has recently been identified at two are allochthonous and are generally strongly de places in southwest Alaska (fig. 30) in the vicin formed. There are a few isolated fault blocks ity of previously reported (Hoare and Coonrad, however, in which the rocks are only mildly de 1977) blue amphibole localities. The only other formed. Examples are Buchia Ridge (see Hoare reported lawsonite locality in Alaska is also asso and others, 1975) and Hagemeister Island. ciated with blue amphiboles and is on the north (11) Rocks of late Early Cretaceous (Albian) west coast of Kodiak Island (Garden and Forbes, age to late Late Cretaceous (Maestrichian) age 1976). The Kodiak locality and the blue amphi are autochthonous and were derived from nearby bole localities are alined parallel to, and a short source areas. The upper Upper Cretaceous rocks distance northwest of, the Border Ranges fault, are mostly or entirely nonmarine; the others are which is interpreted as a Mesozoic plate bound mostly shallow-water marine deposits. ary (MacKevett and Plafker, 1974). It seems rea (12) Deformation by compression from the sonable to suggest that the lawsonite and blue southeast probably began in early Mesozoic time amphibole occurrences in southwestern Alaska and continued into early and middle Cenozoic may be related to an older suture zone of prob time. In late Cenozoic time however, the rocks able early Mesozoic age. were apparently subjected to tensional forces The lawsonite and blue amphibole localities on and a small basalt-floored graben developed in Cape Newenham and Cape Pierce are in, or are the lower Togiak Valley between the Hagemeis closely associated with, a dismembered ophiolite ter and Togiak-Tikchik faults. complex consisting of metasomatized roddingi- tized gabbro, massive greenstones, fine-grained volcaniclastic rocks, pillow lavas, plagiogranite, REFERENCES CITED and serpentine. The complex is part of a broad, Beikman, H. M., 1974, Preliminary geologic map of the poorly defined belt of highly deformed rocks that southwest quadrant of Alaska: U.S. Geol. Survey Misc. trends north and northeast from Cape Newen Field Studies Map MF-611, 2 sheets, scale 1:1,000,000. ham along the southeast side of an allochthonous Cady, W. M., Wallace, R. E., Hoare, J. M., and Webber, E. J., terrane of Precambrian gneisses and schists. The 1955, The Central Kuskokwim region, Alaska: U.S. rocks in the belt are chiefly volcanic and sedi Geol. Survey Prof. Paper 268,132 p. Griscom, Andrew, 1978, Aeromagnetic map and interpreta mentary rocks of Paleozoic and Mesozoic (Trias- tion of the Goodnews and Hagemeister Island quadran sic) age, extensively overlain by Mesozoic gles region, southwestern Alaska: U. S. Geol. Survey sedimentary rocks toward the northeast. The Open-File Report 78-9-C, 2 sheets, scale 1:250,000. belt contains many isolated tectonic blocks, ul- Hoare, J. M., and Coonrad, W. L., 1959, Geology of the tramafic rocks, layered gabbro, plagiogranite, Bethel quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-285, scale 1:250,000. and two other blue amphibole localities. Potas 1961a, Geologic map of the Hagemeister Island quad sium-argon age determinations made on horn rangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map blende from two gabbro bodies and on horn 1-321, scale 1:250,000. blende at the contact between a large body of ul- 1961b, Geologic map of the Goodnews quadrangle, tramafic rock and the country rocks (F. H. Wil Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-339, scale 1:250,000. son and J. G. Smith, written commun., 1977) 1978, Geologic map of the Goodnews and Hagemeis indicate that the mafic and ultramafic rocks are ter Island quadrangles region, southwestern Alaska: of Early Jurassic age. B-55 162° 161° 160°

Jurassic andesite and Cenozoic basalt

beneath unconsolidated

EXPLANATION

Sedimentary rocks

sedimentary rocks

Gneiss and schist

59° L, lawsonite A, blue amphibole

U, ultramafic rock , layered gabbro P, plagiogranite

Mesozoic suture zone?

FIGURE 30. Geologic sketch map showing lawsonite and blue amphibole localities and possible suture zone in southwestern Alaska. B-56 The presence of high-pressure minerals and Late Jurassic through Oligocene and represent the ophiolitic character of the mafic and ultra- the youngest outcropping rock on the northwest mafic rocks in this belt of highly tectonized rocks flank of the Cook Inlet basin. Regionally, these suggest that the belt may be related to a major rocks dip gently to the southeast, occasionally in tectonic feature such as an old suture zone. The terrupted by faults and dip reversals. This report assumed location and trend of the suture zone discusses only the Upper Jurassic through Creta southeast of the Precambrian metamorphic ter- ceous rocks that crop out in the area shown on rane are based on alined exposures of serpentine the geologic map (fig. 31). The geologic map is and structural observations which indicate that based on six weeks of fieldwork done during the the metamorphic terrane has been tectonically summers of 1975 and 1977 and revises the map transported southeastward, whereas the Paleo by Magoon, Adkison, and Egbert (1976). zoic and Mesozoic rocks to the southeast have The Naknek Formation (fig. 31) is known to moved northwestward on southeast-dipping exist in a northeast-trending belt from the thrust faults. From the metamorphic terrane Alaska Peninsula to the Talkeetna Mountains south to Cape Newenham, structural trends are (Burk, 1965; Keller and Reiser, 1959; Detterman northeast and there are several southeast-dip and Hartsock, 1966; Grantz, 1960). The Naknek ping reverse faults. No north-trending faults Formation consists of conglomerate to siltstone, that might be interpreted as an old suture zone but thin-bedded very fine grained fossiliferous have been recognized. Moreover, it seems un sandstone predominates. Field identification is likely that the suture zone would bend abruptly aided by the presence ofBuchia sp.; units overly southward parallel to the seacoast. A more rea ing the Naknek are most reliably differentiated sonable suggestion is that the suture zone arcs by distinctive faunal assemblages. The Naknek gently southwestward toward the Pribilof Is Formation, which contains several intraforma- lands where a large body of serpentinized ultra- tional unconformities, can be mapped through mafic rocks is exposed (Barth, 1956). out the area although the base of the formation is not exposed. Unnamed Lower Cretaceous rocks REFERENCES CITED overlie the Naknek Formation with a very slight angular unconformity. Barth, T. F. W., 1956, Geology and petrology of the The Naknek Formation also occurs in the Kat- Pribilof Islands, Alaska: U.S. Geol. Survey Bull. mai area adjacent to Lake Grosvenor, west of the 1028-F, 64 p. Garden, J. R, and Forbes, R. B., 1976, Discovery of area of this report (Keller and Reiser, 1959, p. blueschists on Kodiak Island, in Short notes on 271). Fossils collected throughout the Katmai Alaskan geology: Alaska Div. Geol. and Geophys. area indicate a Late Jurassic (Oxfordian through Surveys Geol. Kept. 51, p. 19-22. early Portlandian) age and include Buchia con- Hoare, J. M., and Coonrad, W. L., 1977, Blue amphi- centrica, B. mosquensis, and B. rugosa; however, bole occurrences in southwestern Alaska, in Blean, the Naknek Formation from the Iniskin-Tux- K. M., ed., The United States Geological Survey in edni area to the northeast is only as young as ear Alaska; accomplishments during 1976: U.S. Geol. ly Kimmeridgian (Imlay and Detterman, 1973). Survey Circ. 751-B, p. B39. The presence of the unnamed Lower Creta MacKevett, E. M., Jr., and Plafker, George, 1974, The ceous rocks in the Kamishak Hills was first re Border Ranges fault in south-central Alaska: U.S. ported by Parkinson (1960), and an incomplete Geol. Survey Jour. Research, v. 2, no. 3, p. 323-329. section was measured and described by Jones Upper Jurassic and Cretaceous rocks of the and Detterman (1966) (sections 4 and 5 on fig. Kamishak Hills-Douglas River area, lower 31). They described two units a lower unit of Cook Inlet "gray shale and siltstone with many calcarenite By Leslie B. Magoon, Robert M. Egbert, and interbeds.. . containing abundant, mostly frag George Petering mented, valves of Inoceramus," (p. D54), and an upper unit of "rusty-weathering, brownish-gray, The Kamishak Hills-Douglas River area is lo benonitic shale and siltstone that bears fossili cated 350 km southwest of Anchorage in south ferous calcareous concretions." (p. D54). The age western Alaska (fig. 31). The sedimentary rocks of the lower unit is late Hauterivian to early Bar- in and adjacent to this area range in age from remian; the upper unit is Barremian (Jones and

B-57 153° 50' 153° 45' 153" 40'

58° 55

...... v . . . NK ...» .

EXPLANATION

Qs QUATERNARY Surficial deposits 58° 50' -

Kaguyak Formation (Upper Cretaceous) V CRETACEOUS

Unnamed rocks (Lower Cretaceous) Jn Naknek Formation (Upper Jurassic)

Contact Fault Dashed where conceale Measured section

Parts of Mt.Katmai(D-l )and Afognak(D-6) quad

0123 KILOMETERS

ALASKA iS/^^-. «b

FIGURE 31. Geologic map of the Kamishak Hills-Douglas River area, southwestern Alaska.

B-58 Detterman, 1966). The lower unit correlates with the Kamishak Hills, the lower 3 m of the Kag the Nelchina Limestone in the Chitina Valley uyak Formation is a pebble conglomerate con and the Herendeen Limestone of the Alaska taining thick-shelled pelecypods and abraided Peninsula; the upper unit contains the first oc Lower Cretaceous belemnites. The base of the currence of fossils of definite Barremian age in Kaguyak Formation is mapped at the first occur Alaska (Jones and Detterman, 1966). Complete rence of ammonites, thick-shelled pelecypods, sections (1 and 3, fig. 31) of the unnamed Lower conglomerate, and sandstone containing whole Cretaceous rocks were measured by the authors or nearly whole shells of Inoceramus sp. In in 1975 and 1977. The additional section mea places stratigraphic relations are obscured by sured in the lower unit consists of a basal sand small faults, landslides, or intrusions of Tertiary stone, up to 15 m thick, that is rich in Ino- igneous rock. The Kaguyak Formation presum ceramus prisms and belemnites; the upper unit ably covered the entire Kamishak Hills-Douglas contains sandstone channels. Modal analyses in River area prior to post-Cretaceous erosion dicate that sandstone in this unit is arkosic, simi (probably pre-West Foreland time). lar to the Naknek Formation except for the presence of large numbers of Inoceramus prisms REFERENCES CITED (Lankford and Magoon, 1978). Field identifica tion of these Lower Cretaceous rocks is based on Burk, C. A., 1965, Geology of the Alaska Penin these distinctive lithologies and fossils. Post- sula Island arc and continental margin: Geol. Cretaceous faults of less than 15m displacement Soc. America Mem. 99, (part 1), 250 p. have been mapped in the northwest part of the Detterman, R. L., and Hartsock, J. K., 1966, Geology of area (fig. 31). Block slides and slumps of Ka- the Iniskin-Tuxedni region, Alaska: U.S. Geol. guyak Formation rest on the upper shale unit Survey Prof. Paper 512, 78 p. throughout the area. The unnamed Lower Creta Grantz, Arthur, 1960, Geologic map of Talkeetna Mountains (A-2) quadrangle, Alaska and the con ceous rocks are almost 215 m thick in both sec tiguous area to the north and northwest: U.S. Geol. tion 1 and section 3 (fig. 31). These rocks, Survey Misc. Geol. Inv. Map 1-313, scale 1:48,000. including the basal sandstone, thin by erosion to Imlay, R. W., and Detterman, R. L., 1973, Jurassic pa- the northwest until the Kaguyak Formation rests leobiogeography of Alaska: U.S. Geol. Survey Prof. unconformably on the Naknek Formation. Ero- Paper 801, 34 p. sional remnants of the unnamed Lower Creta Jones, D. L., and Detterman, R. L., 1966, Cretaceous ceous rocks exist near the truncated edge. The stratigraphy of the Kamishak Hills, Alaska Penin Kaguyak Formation overlies the unnamed Low sula, in Geological Survey research 1966: U.S. er Cretaceous rocks with a distinct angular un Geol. Survey Prof. Paper 550-D, p. D53-D58. conformity. Keller, A. S., and Reiser, H. N., 1959, Geology of the The Kaguyak Formation, named and de Mount Katmai area, Alaska: U.S. Geol. Survey Bull. 1058-G, p. 261-298. scribed by Keller and Reiser (1959, p. 273) for ex Lankford, S. M., and Magoon, L. B., 1978, Petrography posures in the vicinity of Kaguyak 20 km south of the Upper Jurassic through Oligocene sand of the Kamishak Hills-Douglas River area, is of stones in the Cape Douglas-Kamishak Hills area, Late Cretaceous age. Sections 4 and 5 (fig. 31) lower Cook Inlet, in Johnson, K. M., ed., The Unit contain Pachydiscus (Pachydiscus) kamisha- ed States Geological Survey in Alaska; accomplish kensis Jones of Maestrichtian age (Jones and ments during 1977: U. S. Geol. Survey Circ. 772-B, Detterman, 1966). Section 6 contains the most p. B60. complete basal section. This section comprises as Magoon, L. B., Adkison, W. L., and Egbert, R. M., 1976, much as 305 m of ammonite- and Inoceramus- Map showing goelogy, wildcat wells, Tertiary rich sandstone with some interbedded siltstone; plant-fossil localities, K-Ar age dates and petro the upper 170 m of section is gray siltstone simi leum operations, Cook Inlet area, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-1019,3 sheets, lar to the lower part of the type section of the scale 1:250,000. Kaguyak Formation. Modal analyses indicate Parkinson, L. J., 1960, Cretaceous strata of the Cape that the basal sandstone of the Kaguyak Forma Douglas area, Alaska Peninsula, Alaska [abs.]: tion is similar to the Naknek Formation (Lank- Geol. Soc. America Bull., v. 71, no. 12, pt. 2, p. ford and Magoon, 1978). In the northwest part of 2087.

B-59 Petrography of the Upper Jurassic through tite. In unnamed Lower Cretaceous rocks in Oligocene sandstones in the Cape Douglas- which detrital calcite approaches 70 percent, Kamishak Hills area, lower Cook Inlet only 2 percent diagenetic matrix is present, but By Stephen M. Lankford and Leslie B. Magoon the matrix increases to as much as 32 percent in samples without detrital calcite. Unlike the Nak Sandstones were collected for thin sections nek Formation, the unnamed Lower Cretaceous from five stratigraphic units in the Cape Doug- rocks contain significant amounts of secondary las-Kamishak Hills area of lower Cook Inlet dur calcite cement, probably from recrystallized de ing the summers of 1975 and 1977. A total of 53 trital calcite. thin sections were cut from sandstones that Data from the Kaguyak Formation form two range in age from Late Jurassic through Oligo fields on the Q-F-L diagram. The basal sand cene and include the Naknek Formation (Burk, stone that unconformably overlies the unnamed 1965), unnamed Lower Cretaceous rocks (Jones Lower Cretaceous rocks and the Naknek Forma and Detterman, 1966), Kaguyak Formation tion form the first field, and the upper sandstone (Keller and Reiser, 1959), West Foreland Forma forms the second. Eight samples from the basal tion, Hemlock Conglomerate, and the lower part sandstone have an average composition of of the Tyonek Formation (Magoon and others, QggFggL^, showing a slight enrichment in volcanic 1976). The grain size of these poorly sorted sand lithic fragments compared to the underlying stones ranges from very fine to medium. Using a units. Twelve samples from the upper sandstone petrographic microscope, 300 points per slide are rich in lithic fragments and have an average were counted using a 1-mm grid for very fine- to composition of Q27F32L41. The quartz grains show fine-grained sandstones and a 2-mm grid for me undulatory extinction. The mafic minerals in dium-grained sandstones. The data include po clude trace amounts of mica, but no horn rosity and the amount and type of quartz, blende. Matrix cement (epimatrix) in the upper feldspar, lithic fragments, shell fragments, mafic sandstone consists of decomposed lithic frag components, matrix, and cement. Microcrystal- ments. line quartz grains similar to chert were counted Data on the West Foreland Formation form a as lithic fragments because many include plagio- scattered field near the volcanic lithic fragment clase and other minerals, and a few grade into end member. The average composition of the aphanatic volcanic lithic fragments. The type of sandstone from the West Foreland is Q29F22L49. matrix was recorded using the classification of The quartz grains show undulatory extinction, as Dickinson (1970). in the Kaguyak Formation, and mafic minerals The sandstone composition of the Naknek occur in trace amounts. Matrix cements (ortho- Formation and the unnamed Lower Cretaceous matrix and epimatrix) are diagenetically altered rocks is summarized on a Q-F-L diagram (fig. volcanic lithic fragments. 32). The average normalized compositions of Data on the Hemlock Conglomerate and the these units are QgeFf^ and Q38F59L3, respec lower part of the Tyonek Formation are undif- tively, on the basis of 17 thin sections that plot ferentiated because both units are late Oligocene midway between the quartz and feldspar end in age and of similar composition. These rocks numbers. Calcite grains in sandstone in the un form a tight, uniform field of data with an aver named Lower Cretaceous rocks are fragmented age composition of Q39F24L37. Quartz grains, Inoceramus prisms as much as 3 mm long. These showing undulatory extinction, are abundant, prisms were not included in the Q-F-L diagram and many samples average almost 2 percent even though they are present in amounts from mica, mostly biotite. less than 1 to as high as 70 percent. The mafic Burk (1965) displayed the grain composition minerals include hornblende and mica; the con of coeval units from the Alaska Peninsula on a tent of total mafic minerals averages about 2 per Q-F-L diagram in which quartz and chert are in cent. Diagenetic matrix in these sandstones cluded on the same end member. His data on the consists predominantly of phyllosilicate in thin Upper Jurassic and Lower Cretaceous units rims separating detrital grains. In the Naknek (Naknek Formation, Staniukovich Formation, Formation authigenic minerals include quartz and Herendeen Limestone) compare very well overgrowths, chlorite, sericite, and some laumon- with the data presented here for similar units.

B-60 QUARTZ QUARTZ

FELDSPAR LITHIC LITHIC NO. THIN SYMBOL SECTIONS STRATIGRAPHIC UNIT AGE 8 Hemlock Conglomerate and Lower part of Tyonek Formation Oligocene 4- 8 West Foreland Formation Paleocene A 12 Kaguyak Formation-upper sandstone Late Cretaceous A 8 Kaguyak Formation-basal sandstone Late Cretaceous 7 Unnamed rocks Early Cretaceous O 10 Naknek Formation Late Jurassic

FIGURE 32. Q-F-L diagrams, Upper Jurassic through Oligocene sandstones, Cape Douglas-Kamishak Hills area, southern Alaska.

Burk's data for Upper Cretaceous (Chignik For study. Winkler (1978) examined 28 thin sections mation) rocks show lithic fragments ranging in of sandstones collected from the Chickaloon and abundance from 25 to 80 percent. As this study Arkose Ridge Formations in the Matanuska Val shows, the upper sandstone of the Kaguyak For ley and Talkeetna Mountains. The Chickaloon is mation also contains abundant lithic fragments. coeval with the West Foreland Formation. Only Stewart (1976) presented data on Tertiary the sandstone from the Chickaloon Formation, rocks from the Middle Ground Shoal State No. 1 whose average composition is QaaFaoLss* compares well in upper Cook Inlet and from the Cape favorably with the West Foreland Formation. Douglas area. Recalculating Stewart's Q-F-L The average composition of the Arkose Ridge data so that chert is included as a lithic fragment, Formation is Q^^. The similarity of its com the West Foreland Formation has an average position to that of the underlying granitic pluton composition of Q19F26L55 and Q24F17L59, respec suggests a local, rather than regional, source. The tively, from the two areas. The undifferentiated sandstone compositions of the Naknek Forma Hemlock Conglomerate and Tyonek Formation tion, unnamed Lower Cretaceous rocks, and has an average composition of Q55F 16L29 . from the basal part of the Kaguyak Formation Stewart's data compare well with data in this compare favorably with the sandstone composi- B-61 tions of the Arkose Ridge Formation. Chignik and Sutwik Islands quadrangles In conclusion, the Naknek Formation and the (1:250,000) (area 9, fig. 2). The formation is of unnamed Inoceramus-iich Lower Cretaceous particular interest in that porous sandstones, rocks appear to have originated from a granitic where they were cut by intrusive rock, permitted source. The overlying basal sandstone of the circulation of mineral-bearing fluids and now lo Kaguyak Formation was derived from these cally contain anomalous concentrations of base older units and from the same granitic source. metal sulfides. These same porous sandstones The upper sandstone of the Kaguyak Formation are also of interest as potential reservoir rock for contains abundant volcanic lithic fragments, oil and gas, and the formation contains numer probably a result of extensive volcanic activity. ous coal beds. The same or another period of volcanism in the The Chignik Formation was named and de early Tertiary contributed significant amounts scribed by Atwood (1911, p. 41-48) from expo of lithic material to the West Foreland forma sures along the shore of Chignik Bay; the type tion, whereas the undifferentiated Hemlock section was designated along Whalers Creek, Conglomerate and Tyonek Formation contains near the head of Chignik Lagoon. Burk (1965) more quartz and fewer volcanic lithic fragments. recognized both marine and nonmarine rocks in the formation the marine beds overlie his non- REFERENCES CITED marine Coal Valley Member. Burk, C. A., 1965, Geology of the Alaska Penin A section on the northwest shore of Chignik sula Island arc and continental margin (part 1): Lagoon was measured in detail in July 1977; this Geol. Soc. America Mem. 99, 250 p. is probably the section referred to by Atwood Dickinson, W. R., 1970, Interpreting detrital modes of (1911, p. 41-48). The 490-m section is almost graywacke and arkose: Jour. Sed. Petrology, v. 40, completely exposed between Boomers Cove and p. 695-707. the sandspit at the mouth of Chignik Lagoon; Jones, D. L., and Detterman, R. L., 1966, Cretaceous erosion has removed the top. The beds uncon- stratigraphy of the Kamishak Hills, Alaska Penin formably overlie the Naknek Formation (Upper sula, in Geological Survey research 1966: U.S. Jurassic). Geol. Survey Prof. Paper 500-D, p. D53-D58. The depositional environment of the rocks at Keller, A. S., and Reiser, H. N., 1959, Geology of the Mount Katmai area, Alaska: U.S. Geol. Survey this locality is cyclic nearshore marine to non- Bull. 1058-G, p. 261-298. marine; three complete cycles and a part of a Magoon, L. B., Adkison, W. L., and Egbert, R. M., 1976, fourth are represented in the exposed beds. The Map showing geology, wildcat wells, Tertiary last of the fourth cycle is missing, probably owing plant-fossil localities, K-Ar age dates and petro to erosion. The cycles are of approximately the leum operations, Cook Inlet area, Alaska: U.S. same thickness, ranging from 106 to 137 m. Geol. Survey Misc. Inv. Map 1-1019,3 sheets, scale In the first cycle, which is 122 m thick, a dark 1:250,000. siltstone deposited offshore rests unconformably Stewart, R. J., 1976, Turbidites of the Aleutian abyssal on the Naknek Formation. This deposit is over plain; Mineralogy, provenance, and constraints for lain by a clean, crossbedded sandstone inter Cenozoic motion of the Pacific Plate: Geol. Soc. preted as an offshore bar with a paleoccurrent di America Bull., v. 87, p. 793-808, 14 figs. Winkler, G. R., 1978, Framework grain mineralogy and rection of southwest to northeast. The overlying provenance of Arkose Ridge and Chickaloon For beds are massive sandstone representing fore mation sandstones, Matanuska Valley, in John shore and shoreface deposits. They contain nu son, K. M., ed., The United States Geological merous coquina layers of large thick-shelled Survey in Alaska; accomplishments during 1977: pelecypods including Inoceramus, Glycymeris, U. S. Geol. Survey Circ. 772-B, p. B70. Ostrea, Pecten, and numerous smaller pelecy pods including Anomia. The fossils have not yet Interpretation of depositional environments in been completely identified, so other genera may the Chignik Formation, Alaska Peninsula By Robert L. Detterman be present. The shells are very abundant, and nearly all are disarticulated. Thin, dark siltstone The Upper Cretaceous Chignik Formation is with abundant carbonaceous debris and thin being studied as part of the Alaska Mineral Re coat seamlets overlies the shoreface sandstone source Assessment Program (AMRAP) in the and is interpreted as a coastal plain deposit. The

B-62 siltstone is extensively burrowed. The top of the ing this investigation probably will not greatly siltstone is channeled and overlain by a dark car change this designation, but should increase the bonaceous sandstone, probably a distributary number of genera reported from the formation. channel deposit; this sandstone completes the first cycle. REFERENCES CITED A slight marine transgression initiated the sec ond cycle, which includes 60 m of thin olive-gray Atwood, W. W., 1911, Geology and mineral resources of to yellow-brown sandstone and siltstone prob parts of the Alaska Peninsula: U.S. Geol. Survey ably deposited in a lagoon. These deposits are Bull. 467,137 p. overlain by a shoreface sandstone and 23 m of Burk, C. A., 1965, Geology of the Alaska Peninsula Island arc and continental margin (Pt. 1): Geol. fluvial sandstone and conglomerate with large- Soc. America Mem. 99, 250 p. scale crossbedding, numerous channels, climbing Jones, D. A., 1963, The Upper Cretaceous (Campanian ripple marks, and thininterfluvial shale deposits and Maestrichtian) ammonites from southern with coal beds. Alaska: U.S. Geol. Survey Prof. Paper 432, 53 p. The third cycle starts with 60 m of massive Knappen, R. S., 1929, Geology and mineral resources of sandstone with minor conglomerate representing the Aniakchak district, Alaska: U.S. Geol. Survey foreshore and shoreface deposits. These beds Bull. 797, p. F161-F227. contain numerous shell layers with the same gen Martin, G. C., 1926, The Mesozoic stratigraphy of eral pelecypod fauna as lower in the section, but Alaska: U.S. Geol. Survey Bull. 776, 493 p. with the addition of large Canadoceras and New ages on intrusive rocks and altered zones on Neodesmoceras ammonites. The largest speci the Alaska Peninsula men noted was approximately .43 m across. By F.H. Wilson, R.L. Detterman, and M.L. Silberman These beds are overlain by about 45 m of thin dark- to medium-gray lagoonal siltstone and Preliminary potassium-argon dating of intru sandstone containing a few Inoceramus, but a sive rocks and altered zones in the Chignik and different species than found lower in section. Sutwik Island quadrangles of the Alaska Penin Both the foreshore and lagoonal deposits are ex sula seems to indicate at least three and possibly tensively burrowed; Diplocraterion- and Sko- four Tertiary ages of alteration and mineraliza lithos-type burrows are the most commonly tion. found. The nonmarine part of this cycle is only At Bear Creek Mining Company's Bee Creek 25 m thick and consists of fluvial channel sand prospect, in the Chignik C-2 quadrangle (fig. 33), stone and conglomerate with point-bar crossbed the samples completely studied so far indicate a ding. mineralization or alteration age of about 3.7 m.y. All of the upper 125 m representing the incom An amphibole from an altered sample of one of plete fourth cycle is massive marine sandstone the original plutons has an apparent age near 7 and conglomerate with a few interlayed siltstone m.y. Additional samples of various phases of the beds; these deposits are interpreted as foreshore alteration assemblage are being dated. to shoreface deposits. These beds are extensively Dates on secondary biotite and biotite and po burrowed, mainly with Skolithos-type burrows, tassium-feldspar in late pegmatites in the pluton and contain a few Inoceramus shells. at Warner Bay (Chignik A-2 quadrangle) possi The depositional environment of the Chignik bly indicate a mineralization age of 6.5 m.y. Formation is considerably more complex than Work is also in progress on an unaltered sample originally believed (Atwood, 1911; Martin, 1926; of this pluton from another locality to determine Knappen, 1929; and Burk, 1965). The cyclic the original emplacement date. nearshore-to-continental, high-energy environ Two dates from the prospect at Mallard Duck ment produced numerous massive sandstone Bay (Chignik A-2 quadrangle) suggest two dis and conglomerate beds that have good to fair vis tinct ages of alteration. Amphibole from a chlori- ual porosity and good sorting. These beds are po tized dike intruding strongly propylitically tential reservoir rock for oil and gas. altered rocks has an apparent age near 32 m.y. If The Chignik Formation is considered Late this dike postdates the alteration, as the field re Cretaceous (Campanian) in age (Jones, 1963; lations suggest, then a sample of phyllically al Burk, 1965). The abundant fossils collected dur tered rock (quartz-sericite) collected about 1 km

B-63 56° 15'

FIGURE 33. Location map, potassium-argon studies in Chignik and Sutwik Islands quadrangles. downstream in the same large altered zone indi events in this or other areas. Work in progress is cates another alteration event at approximately expected to resolve these questions. 21 m.y. The dike has a definite intrusive contact A sample of a biotite-dacite from the west end with the altered rocks it intrudes; however, no of Sutwik Island has yielded a biotite age of 35.5 other samples as yet indicate any older alteration m.y. This hypabyssal intrusive body is not defi- B-64 nitely associated with any alteration, though Mollusks of probable Miocene age were col there are abundant small alteration zones in the lected from sandstone beds on the south shore of immediate vicinity. Ukolnoi Island located near the entrance to Pav Finally, a granitic cobble collected from an lof Bay. These marine strata are probably correl outcrop of conglomerate in the Chignik Forma ative with the Bear Lake Formation. As is tion along the south shore of Chignik Lagoon has common in many areas of the southwestern Alas yielded a minimum age of 92 m.y. ka Peninsula, the fossiliferous strata of Ukolnoi Island grade upward into nonmarine volcano- Tertiary sedimentary rocks of the Alaska Penin genie sedimentary rocks that are unconformably sula between Pavlof Bay and False Pass; their overlain by volcanic flows of probable Quarter- geology and petroleum potential By Hugh McLean nary age. Small islands and reefs that lie south of the Unmapped areas of the outermost part of the Alaska Peninsula between Sanak Island and Alaska Peninsula contain late Tertiary marine Deer Island consist mainly of gently dipping co and nonmarine sedimentary rocks, capped by lumnar volcanic flows locally interbedded with volcanic flows, and intruded by numerous ande- volcanic breccia and lenses of tuffaceous sedi sitic dikes and sills. Gently folded sedimentary mentary rocks. rocks between False Pass and Morzhovoi Bay The petroleum potential of Neogene sedimen (fig. 34) consist mainly of nonmarine and shal tary rocks at the Aleutian end of the Alaska Pen low-marine sandstone, mudstone, and conglom insula is limited by their volcanic provenance erate. Locally, these strata contain molluskan and by igneous intrusions including numerous assemblages of Miocene age. The rocks were dikes and sills and a small number of quartz dio- derived largely from a volcanic source terrane. rite stocks that may be comagmatic with some of Rapid facies changes, both lateral and stratigra- the volcanic rocks. Petroleum source rocks such phical, suggest a paleogeographic setting similar as carbonaceous mudstone or marine shale con to the present peninsula in which active volcanic stitute a very small part of the sedimentary re centers supply sediment to nearby fluvial and cord. Most Tertiary sandstone beds can be shallow-marine environments. described as "hard and tight." Low porosity and Sedimentary rocks farther to the northeast, permeability values are primarily due to high between Cold Bay and Pavlof Bay, include ma percentages of tuffaceous and(or) argillaceous rine and nonmarine volcaniclastic rocks ranging matrix or to alteration associated with intrusive in age from Oligocene through Pleistocene. Mol- rocks. lusks of Oligocene age were found in the Bel- REFERENCES CITED kofski Formation. Kennedy and Waldron (1955), who named the formation, reported that it con Burk, C. A., 1965, Geology of the Alaska Peninsula Island tained only plant fossils. Burk (1965) suggested a arc and continental margin: Geol. Soc. America Mem. possible age equivalence of the Belkofski to his 99, 250 p. Eocene Tolstoi Formation on the basis of marine Kennedy, G. C., and Waldron, H. H., 1955, Geology of Pavlof Volcano and vicinity, Alaska: U.S. Geol. Survey Bull. megafossils. Most of the Belkofski Formation, 1028-A, 19 p. [1956]. however, is nonmarine, consisting mainly of vol canic sandstone with thin beds of black carbona- SOUTHERN ALASKA ceous mudstone. The upper part of the formation contains a flora of broad deciduous New potassium-argon data on the age of mineral leaves and conifer needles. Strata in much of the ization and metamorphism in the Willow Creek area between Cold Bay and Belkofski Bay were mining district, southern Talkeetna Mountains, Alaska provisionally mapped as Bear Lake (?) Forma By Miles L. Silberman, Bela Csejtey, Jr., James G. tion by Burk (1965). These strata should be Smith, Marvin A. Lanphere, and Frederick H. mapped as the Belkofski Formation; the Bel Wilson kofski is unconformably overlain by weakly con solidated Pliocene and Pleistocene fluvial The now largely abandoned Willow Creek gravels capped in turn by probable Pleistocene mining district, southern Talkeetna Mountains, andesitic and basaltic lava flows. Alaska, produced nearly $18,000,000 in gold and B-65 EXPLANATION

o ¥ 1 Q> C O u O O* Stepovak Formation of Burk (1965) 2 5 o> § * I5 * Volcanic and sedimentary rocks Tolstoi Formation of Burk (1965)

£ 3

S JC Hoodoo Formation Shumaqin Formation

Naknek Formation

Quartz diorite Contact

FIGURE 34. Geologic map of Alaska Peninsula between Pavlof Bay and False Pass.

B-66 minor silver between 1909 and the early 1950's. TABLE 3. Potassium-argon ages of granitic rocks, schist, Mineralized quartz veins, which contain gold and and mineralization, southern Talkeetna Mountains silver along with minor quantities of base metals [Locations 1 and 2 from Bela Csejtey, Jr., unpub. data, (in pyrite, galena, chalcopyrite, sphalerite, mo 1978; locations 3, 4, 8, 9, and 10, this work; loca lybdenite, and arsenopyrite), cut Late Creta tions 5, 6, and 7 from Csejtey and Smith (1975)] ceous and early Tertiary tonalite and quartz- Location, Rock type Mineral Age, m.y. mica schist of probable Jurassic age (Ray, 1954; fig. 34 Silberman and others, 1976; Bela Csejtey, Jr., 1 Tonalite Biotite 69 ± 2.1 unpub. data, 1978). Hornblende 73 ± 2.2 A generalized geologic map of the Willow 2 Tonalite Biotite 72 ± 2.2 Creek area (fig. 35) shows the mineralized area in Hornblende 74 ± 2.2 3 Biotite- Biotite 65 ± 2.0 the southwestern part of the area underlain by granite Muscovite 67 + 2.0 tonalite and the northern part of that underlain 4 Tonalite Biotite 78 ± 2.4 by schist. Most of the district's production came 5 Schist Muscovite 60 + 1.8 from veins in the tonalite (Ray, 1954). Biotite- 6 Schist Muscovite 66 ± 2.0 granite in the western part of the map area is of 7 Schist Muscovite 59 ± 1.8 about the same age as the tonalite and is prob 8 Serpent inite Actinolite 89 ± 4.5 ably a more felsic differentiate of the tonalite 9 Serpentinite Actinolite 91 ± 4.6 parent magma (Bela Csejtey, Jr., unpub. data, 10 Altered Muscovite 56 ± 1.7 1978). tonalite Potassium-argon ages of minerals from sam ples of tonalite, schist, and metamorphosed ultramafic rocks that intrude the schist are schist facies, but relicts of hornblende and gar summarized on table 3, and the sample locations net, now replaced by chlorite, indicate that it has are shown on figure 35. Additional potassium-ar been retrograded from amphibolite facies (Csej gon data from the Talkeetna Mountains are re tey and Smith, 1975). The potassium-argon ages ported in Csejtey and others (1977). The tonalite of micas from the schist are uniformly lower than and biotite-granite give nearly concordant min those of the tonalite by 5 to 21 m.y. However, two eral-pair ages (biotite-hornblende and biotite- actinolite ages from the metamorphosed mafic muscovite), but these range from 60 to 73 m.y. In rocks, which intrude the schist, yielded concor the Willow Creek area the range in potassium- dant results of 91 and 89 m.y., both older than argon ages of mineral pairs and single minerals is the ages of micas from the tonalite. Amphiboles, 70 to 78 m.y. in general, retain more argon during post-crys The tonalite is mineralogically uniform; mafic tallization thermal events than do muscovites, materials are hornblende and minor biotite, but and their ages probably better represent the time grain size varies. Not enough detailed mapping of prograde metamorphism of the schist terrane has been done to determine whether this is a sin than do the muscovite dates from the schist it gle pluton or a series of composite bodies. Ray self. (1954) indicates that the finer grained tonalite We believe that the whole set of data, particu (quartz-diorite of Ray, 1954) occurs near the larly the rather large spread of ages in both the southern margin and represents a primary fea schist and the tonalite, indicates argon loss from ture of a single pluton, the fine grain size in this the minerals caused by a thermal event younger area being due to proximity of the intrusive than the emplacement of the tonalite. The schist margin. ages do not reflect simple metamorphism by in The tonalite intrudes the schist (Bela Csejtey, trusion of the tonalite since they are younger Jr., unpub. data, 1978; Csejtey and Smith, 1975), than ages given by minerals from that unit. Nu but metamorphism of this unit appears to be merous dikes and irregular intrusions of aplite, uniform and unrelated geometrically to the con pegmatite, lamprophyre, and diabase intrude the tact with the granitic rock. According to Csejtey tonalite; these have not yet been dated. Some re and Smith (1975), the schist is a uniform, setting of parts of the tonalite may have resulted medium-grained quartz-muscovite-chlorite-al- from emplacement of these intrusions if they are bite-minor biotite schist. It is presently green- younger than the tonalite by a significant B-67 "5 I Chickaloon Formation 3 > ox. >*- Rock date A Mineralization date

Quartz mica schist

FIGURE 35. Geologic map of the Willow Creek area, southern Talkeetna Mountains, Alaska.

B-68 amount. done to determine whether they are of the same Throughout the district, there are wide but ir origin. An alternative origin for at least some of regularly distributed areas of propylitic alter the veins of the schist is as metamorphic segrega ation of the tonalite, including one along the tions. Analyses are in progress on samples contact with the schist. Narrow (fractions of a collected to test these possibilities. Other inter meter to several meters) sericitic alteration sel pretations of these age data are possible, but in vages adjacent to mineralized quartz veins occur our opinion, the data probably represent com in the tonalite. Alteration selvages along cross- plex, multistage processes that have affected this cutting veins in the schist are characterized by area. Apparently the alteration-mineralization oxidation. However, most cross-cutting veins in episode was late in the sequence. the schist are found in faults and shear zones, which are relatively permeable and have prob REFERENCES CITED ably allowed access of groundwater, causing oxi dation of sulfides in the quartz veins. Other veins Csejtey, Bela, Jr., Nelson, W. H., Eberlein, G. D., Lanphere, M. A., and Smith, J. G., 1977, New data concerning age in the schist appear to be oriented largely along of the Arkose Ridge Formation, south-central Alaska, in planes of foliation and are without noticeable al Blean, K. M., ed., The United States Geological Survey teration selvages. in Alaska; accomplishments during 1976: U.S. Geol. The potassium-argon age of 56 m.y. from mus- Survey Circ. 751-B, p. B62-B64. covite in a quartz-sericite selvage adjacent to a Csejtey, Bela, Jr., and Smith, J. G., 1975, Petrography, ten tative age, and correlation of schist, Willow Creek, Tal- gold-bearing vein at the Bullion mine (fig. 35, lo keetna Mountains, southern Alaska, in Yount, M. E., cation 10; table 3) suggests a possible source of ed., United States Geological Survey Alaska Program, the thermal episode that has affected the area. 1975: U.S. Geol. Survey Circ. 722, p. 48. Quartz veins are pervasively distributed Ray, R. G., 1954, Geology and ore deposits of the Willow throughout the tonalite (Ray, 1954) and range Creek mining district, Alaska: U.S. Geol. Survey Bull. 1004, 86 p. from .01 m to several meters in thickness. The Silberman, M. L., O'Leary, R. M., Csejtey, Bela, Jr., and Pe- age of the veins must be confirmed by additional terson, J. A., 1976, Geochemical anomalies in the Willow dates determined on other samples, but tenta Creek mining district, southern Talkeetna Mountains, tively we suggest that a mineralization-alteration Alaska: U.S. Geol. Survey Open-File Report 76-191, 5 episode at about 56 m.y. may have reset some of sheets, scale 1:24,000. the tonalite ages. Tectonic significance of newly discovered lower Quartz veins and boudins are very common in Paleozoic strata in the upper Chulitna Valley, the schist. We suggest that some of these, at south-central Alaska least, may have formed during the same episode By Bela Csejtey, Jr., Willis H. Nelson, David L. as vein emplacement in the tonalite. The greater Jones, and Norman J. Silbering effect on the ages of schist may be due to two fac Reconnaissance geologic mapping in the Healy tors. The greater permeability of the schist owing A-6 quadrangle disclosed two massive limestone to its foliation may have allowed more extensive beds of Silurian(?) and Devonian age along the heating of the unit by circulating thermal waters, lower course of Long Creek (localities A and B on and the finer grain size of the micas in the schist fig. 36). The two vertical limestone beds, each may have permitted more argon loss than oc about 20 m thick and striking northeasterly, are curred in the coarser grained minerals in the ton exposed in the canyon wall of the creek. The alite. The apparently older ages of the actinolites limestones are massive to thickly bedded and from the metamorphosed mafic rocks may re medium gray, contain numerous shelly frag flect greater argon retentivity in amphiboles ments, and have undergone only moderate re- than in micas and the lower permeability of the crystallization. They are enveloped by poorly metamorphosed mafic minerals in the schist. exposed, dark-gray shale, argillite, and fine This explanation of the potassium-argon age grained graywacke. Contacts between the limes distribution must be further evaluated by addi tone beds and the enveloping rocks are not well tional age determinations from the veins in both enough exposed to determine whether the con the tonalite and the schist. In addition, stable tacts are depositional or tectonic or a combina isotope analyses and fluid-inclusion examination tion of both. Thus, the age of some of the of the veins in the schist and tonalite should be enveloping rocks might differ from that of the li- B-69 mestones. Fossils from the two limestone beds have been identified by W. A. Oliver, Jr. (written commun., 1977). One of the limestones (locality A, fig. 36) yielded massive stromatoporoids and Dendrostella? sp. of Middle Devonian age. The other bed (locality B, fig. 36) contains Labechia sp. and Favosites sp. of Silurian or Devonian age. Whether the two limestone beds are both of De vonian age, or only one is Devonian and the other is Silurian, cannot be determined on the basis of information presently available. Lithologic characteristics of the limestones suggest that they were deposited in shallow wa 63°00' 10 KILOMETERS ter, perhaps along an ancient continental mar gin. These rocks occur only about 6 km to the EXPLANATION east of a narrow belt of basalt, serpentinite, dia base, and chert interpreted to be remnants of a dismembered ophiolite sequence, indicative of QUATERNARY deep-water ocean floor deposition (Jones and others, 1977). These ophioKtic rocks have been > TERTIARY dated on the basis of conodonts and radiolarians by D. L. Jones (unpub. data, 1978) as Late De vonian in age.

CRETACEOUS The discovery of the Silurian (?) and Devonian sedimentary rocks in the upper Chulitna Valley is of great tectonic importance. The present

JURASSIC proximity of these Paleozoic marginal deposits to ocean floor deposits of slightly younger age is additional evidence for large-scale alpine-type JURASSIC orogenic deformation in south-central Alaska. AND Volcanic and sedimentary rocks TRIASSIC This orogeny took place in middle to Late Creta (Upper Triassic and Lower Jurassic ceous time as the result of northward plate mo tion and suturing of allochthonous terranes to Basalt, serpentine, chert, diabase - DEVONIAN continental rocks that are now part of the North American plate (Csejtey, 1976 and unpub. data;

DSI Jones and others, 1977).

DSga-graywacke and argillite DEVONIAN (Age uncertain; in part probably AND REFERENCES CITED Silurian and Devonian) SILURIAN(?) DSts -limestone Csejtey, Bela, Jr., 1976, Tectonic implications of late Paleo (Devonian and Silurian (?)) zoic volcanic arc in the Talkeetna Mountains, south- central Alaska: Geology, v. 4, p. 49-52. Fossil locality mentioned in text Jones, D. L., Silberling, N. J., and Hillhouse, John, 1977, ____U Wrangellia A displaced terrane in northwestern High-angle reverse fault, approximately located, North America: Canadian Jour. Earth Sci., v. 14, p. U indicates upthrown side 2566-2577.

Thrust fault, teeth on upper plate V "V" Framework grain mineralogy and provenance of sandstones from the Arkose Ridge and Chickaloon Inferred thrust fault, teeth on upper plate Formations, Matanuska Valley FIGURE 36. Generalized geologic map of the upper Chu- By Gary R. Winkler litna Valley area, south-central Alaska. Modal analyses of 20 thin sections from the Arkose Ridge Formation and eight from the Chickaloon Formation, courtesy of Arthur B-70 Grantz and George Plafker, indicate that sand modes of samples from the Chickaloon Forma stones from both formations are subquartzose tion plot within the lithic or feldspatholithic that is, their total of quartzose grains is less than fields. The most obvious dissimilarity is the 50 percent. In proportions of their other detrital scantiness of lithic detritus (averaging about 6 constituents, however, sandstones from the two percent) in Arkose Ridge samples and the abun formations are completely dissimilar and plot in dance of lithic detritus (about 52 percent) in distinct fields in a Q-F-L ternary diagram (fig. Chickaloon samples. Also strikingly dissimilar is 37). Modes of samples from the Arkose Ridge the relative abundance of biotite (averaging 8.3 Formation plot within the feldspathic and litho- percent) in Arkose Ridge samples and the pauci feldspathic fields of Dickinson (1970), whereas ty of biotite (1.0 percent) in Chickaloon samples. QUARTZt 75%/

50%.

Feldspathic Lithofeldspathic Feldspatholithic FELDSPAR 3:1 1:1

FORMATION Q F L BIOTITE SEDIMENTARY RF METAMORPHIC RF MEAN 37 57 6 8.3 Arkose Ridge Fm. Range 24 56 44-70 026 0.320.9 MEAN 28 20 52 1.0 Chickaloon Fm. A Range 747' 828 42-66 .0.22.7 FORMATION V S M C/Q P/F V/L MEAN 71 15 14 .05 .92 .71 Arkose Ridge Fm. Range 0-100 050 0 100 .00.16 .82.98 00 1.00 MEAN 89 7 4 .21 .96 .86 Chickaloon Fm. A Range 77-99 0 18 1-14 .09-.31 93-1.00 .77-.99 Q = total quartzose grains L = total rock fragments (RF) C= polycrystalline quartzose grains V = volcanic and plutonic RF F = total feldspar S = sedimentary RF P plagioclase M -metamorphic RF

FIGURE 37. Framework grain compositions of 28 point-counted sandstones from the Matanuska Valley; roughly following the classifications of Crook (1960) and Dickinson (1970). B-71 Subdivision of the ternary end-members, total Q22F69L09; his Chickaloon sandstones have an quartzose grains (Q), total lithic grains (L), and average composition of Q3oF22L48. His reported total feldspar grains (F), into components fur average values for C/Q are 0.06 and 0.18 for his ther enhances the distinctions between the Ar- Arkose Ridge and Chickaloon samples, respec kose Ridge and Chickaloon samples. One- tively. twentieth of the total quartzose grains in the Ar- Sandstones of the Arkose Ridge Formation are kose Ridge Formation are polycrystalline (C), derived largely from a plutonic provenance. expressed as an average ratio (C/Q) of 0.05, Most diagnostic are the abundance of mica and whereas about one-fifth of Chickaloon quartzose feldspar (particularly myrmekitic and antiperth grains are polycrystalline (C/Q=0.21). In addi itic varieties) and the scantiness of lithic and pol tion, in the Chickaloon Formation, on the aver ycrystalline quartzose detritus. The ubiquity of age, a much greater proportion of total lithic sphene and the trace occurrence of allanite grains are altered intermediate to mafic volcanic among the heavy minerals also indicate deriva grains (V), which may be expressed as V/L ratio tion from a plutonic terrane. of 0.86; in the Arkose Ridge Formation on the average nearly one-third of total lithic grains are On Government Peak, Arkose Ridge, and Eska sedimentary (S), metamorphic (M), or plutonic Mountain, the formation rests unconformably on (V/L=0.72). No statistical significance can be at biotite and biotite-hornblende tonalite, quartz tached to the slight difference in plagioclase feld diorite, and associated metamorphic rocks of the spar (P) to total feldspar (F) ratios between the Talkeetna batholith (Grantz and Wolfe, 1961). Arkose Ridge (P/F=0.92) and Chickaloon (0.96) The age of these subjacent rocks recently has Formations, but myrmekitic and antiperthitic been demonstrated to be Middle and Late Juras textures that are common in feldspar grains of sic (Csejtey and others, 1977). Pebbles from near Arkose Ridge samples have not been observed in the base of the formation are weakly foliated bio feldspar grains of Chickaloon samples. tite and biotite-hornblende tonalite and quartz diorite, and it is plausible that the Arkose Ridge Heavy minerals are not abundant in samples Formation sandstones also are largely derived lo from either the Arkose Ridge or Chickaloon For cally from unroofing of the plutonic and meta mations; their average modes are only 1.6 per morphic terrane. cent and 1.1 percent, respectively. In Arkose Where the Arkose Ridge Formation is pre Ridge samples, epidote, sphene, and apatite pre sumed to lap onto the schist of Willow Creek at dominate in the heavy-mineral suites, although the southwest end of the Talkeetna Mountains, hornblende or muscovite may be the most local derivation also is indicated, for detritus and numerous heavy minerals in particular samples. conglomerate includes pebbles of crenulated Zircon is frequently present in trace amounts, schist (Arthur Grantz, oral commun., 1976) and and allanite, augite, garnet, and detrital chlorite in sandstone includes numerous foliated lithic are sporadically present. In Chickaloon samples, grains and composite amphibole-quartz-epidote muscovite, epidote, garnet, and apatite com metamorphic grains. This terrane is dated by po monly are present, and glauconite, hornblende, tassium-argon methods on muscovite at approxi pumpellyite, and zircon have been noted in sin mately 60 m.y. (Csejtey and Smith, 1975). This gle samples. The only consistent difference be age may record an uplift age of the Willow Creek tween heavy-mineral suites from the two terrane. formations is the ubiquity of sphene in Arkose Ridge samples and its apparent absence from The predominantly volcanic provenance of the Chickaloon samples. Also, garnet frequently is Chickaloon Formation is in complete contrast to present in Chickaloon samples but rarely is pre that of the Arkose Ridge Formation. About half sent in Arkose Ridge samples. the detritus in eight Chickaloon samples is rock fragments, of which 89 percent is strongly to Clardy (1974) presented mineralogical data on weakly altered volcanic lithic detritus. In addi 16 samples from the Chickaloon Formation and tion, polycrystalline quartzose grains that prob four from the Arkose Ridge Formation that com ably represent silicified volcanic detritus are pare favorably with these data. His Arkose Ridge abundant. The provenance of Chickaloon For sandstones have an average composition of mation sandstones, however, is somewhat mixed. B-72 The presence of minor detrital carbonate grains, rocks are overlain by Quaternary surficial depos foliated lithic grains, and detrital garnet and its that range in thickness from several tens of pumpellyite indicate some derivation from up meters in the southeast to less than a meter in lifted sedimentary and metamorphic rocks. the northwest. Lowlands flank the upland on the Nonetheless, the preponderant detritus in sand southwest and southeast; here bedrock is covered stones of the Chickaloon Formation is volcanic; by thicker and probably finer grained Quater inasmuch as the detritus is consistently altered, nary sedimentary deposits, partly of marine and it may have been derived from an older volcanic estuarine origin. The upper Beluga River lies in a unit perhaps the adjacent Talkeetna Forma smaller, less well defined lowland that includes tion not from incorporation of contemporane some Quaternary lacustrine deposits. The east ous volcanic debris. edge of the Tordrillo Mountains borders the up land to the west. REFERENCES CITED Steep escarpments about 75 to 150. m high, where slopes of 45 percent or more are common, Clardy, B. L, 1974, Origin of the lower and middle Tertiary border the major rivers which are incised into the Wishbone and Tsadaka Formations, Matanuska Valley, Alaska: Fairbanks, Alaska Univ., M.S. thesis, 74 p. upland surface. Bedrock and surficial deposits Crook, K. A. W., 1960, Classification of arenites: Am. Jour are exposed intermittently in cliffs. Landslides Sci., v. 258, p. 419-428. and other colluvial deposits are common, and Csejtey, Bela, Jr., and Smith, J. G., 1975, Petrography, ten stability is generally poor, especially where the tative age, and correlation of schist, Willow Creek, Tal keetna Mountains, southern Alaska, in Yount, M. E., rivers are actively eroding. Similar steep escarp ed., United States Geological Survey Alaska program, ments face Cook Inlet. 1975: U.S. Geol. Survey Circ. 722, p. 48. Broad escarpments, 150 to 300 m high, com Csejtey, Bela, Jr., Nelson, W. H., Eberlein, G. D., Lanphere, monly separate the lowlands from the upland. M. A., and Smith, J. G., 1977, New data concerning age of the Arkose Ridge Formation, south-central Alaska, in These escarpments probably were the sites of Blean, K. M., ed., The United States Geological Survey glacial erosion as well as subsequent deposition in Alaska; accomplishments during 1976: U.S. Geol. of lateral moraines. Thus, at present, these es Survey Circ. 751-B, p. B62-B64. carpments are quite irregular; slopes between 15 Dickinson, W. R., 1970, Interpreting detrital modes of and 30 percent are most common. In places along graywacke and arkose: Jour. Sed. Petrology, v. 40, p. 695-707. the broad escarpments the morphology is sugges Grantz, Arthur, and Wolfe, J. A., 1961, Age of Arkose Ridge tive of slope instability and may include sackung formation, south-central Alaska: Am. Assoc. Petroleum features. Major landslides include the Tertiary Geologists Bull., v. 45, p. 1762-1765. bedrock; they may have formed fairly soon after deglaciation as the combined result of oversteep- Generalized physiography and geology of the Be ening of the slopes by glacial erosion, followed by luga coal field and vicinity, south-central Alaska withdrawal of glacier ice and the support By Henry R. Schmoll and Lynn A. Yehle it provided; melting of permafrost and burning of coal beds may have been additional aids to The Beluga coal field lies on the northwest sliding. flank of Cook Inlet basin, about 100 km west of Bedrock in much of the area has been de Anchorage, and the Tertiary sedimentary rocks scribed by Barnes (1966) and is not further dis that underlie it contain abundant deposits of cussed here. Bedrock mapped in figure 38 is coal. There is good potential for coal mining in taken from Barnes (1966) with modifications several parts of the area, some of which are indi from Detterman and others (1976) and Magoon, cated on figure 38. Exploration is currently pro Adkison, and Egbert (1976). The major faults ceeding and development is in the planning shown are well established to the northeast (Cas stages for some of these places. tle Mountain fault), southwest (Lake Clark Although lying generally within the Cook In- fault), and south-southwest (Bruin Bay fault); let-Susitna lowland, the Beluga coal field com they are represented in exposed Tertiary rocks in prises a relative upland that is drained mainly by this area, but their mutual intersection remains the Chuitna and Beluga Rivers and that rises in conjectural (Hackett, 1977), and unequivocal elevation from about 100 m near Cook Inlet to evidence of Holocene faulting in this area is still about 900 m near Capps Glacier. The Tertiary lacking. B-73 152°00' 151°30' 151°00' 150°30'

61°00' ^pf!^?^^Sf^:?;-rf-,'. I'ifimy ^-!' '; :- Gra n i te Po i n t

KILOMETERS FIGURE 38. Preliminary map showing generalized physiography and geology of the Beluga coal field and vicinity, south- central Alaska. Explanation on next page.

Glacial deposits of Pleistocene age are shown glacier from both the present Capps Galcier and in figure 38 as divided into an older and younger Triumvirate Glacier valleys; the southerly belt group, in places separated by a belt of undiffer- represents the northern margin of a glacier from entiated glacial deposits that are intermediate in the Chakachatna and McArthur valleys. age but that appear morphologically more simi The area of older glacial deposits is more var lar to those mapped as younger deposits. The ied than that of the younger deposits. In the up younger glacial deposits occur in two main belts, per Chuitna valley the till exposed in river bluffs each bordered by a fairly prominent terminal appears to be substantially older than that in the moraine. The more northerly belt represents a younger moraines and is overlain locally by B-74 EXPLANATION glaciers and this area likely includes much youn ger outwash and related deposits. These and Qa Alluvial, estuarine, and marine similar deposits mapped as younger glacial de deposits (Holocene) posits in the area to the south probably will Qg Glacial deposits. Chiefly lateral prove good sources of construction materials. and end moraines (Holocene) Lacustrine deposits likewise occur in a youn Qls Landslide deposits (Pleistocene ger and an older belt. The younger deposits, and Holocene) which include silt and clay as well as sand and gravel overlying and adjacent to the silt and clay, Younger lacustrine deposits some in deltaic beds, probably represent an en (Pleistocene and Holocene) larged version of Beluga Lake that formed fol Qvc Volcaniclastic deposits and volcanic lowing withdrawal of the younger glacier. The rocks (Pleistocene and Holocene) older deposits are conjectural, based in part on Karlstrom (1964, pi. 1); they more likely repre Qm Marine, estuarine, and alluvial a sent deposits in a local lake, however, rather than deposits (Pleistocene) the regional lake postulated by Karlstrom. Younger morainal deposits The belt mapped as older marine, estuarine, (Pleistocene) and alluvial deposits that extends from Tyonek Morainal deposits, undifferentiated to the Susitna River represents a stratigraphic sequence consisting of silt and clay overlain by Older lacustrine deposits (Pleistocene) sand and gravel. A similar sequence at Anchor °Qi Older morainal deposits (Pleistocene) . age includes the Bootlegger Cove Clay, radiocar bon dated at about 14,000 years B.P. (Schmoll TV Volcanic rocks and others, 1972). It cannot yet be established Ts Sedimentary rocks. Chiefly sandstone, whether the clay in the Tyonek-Susitna River siltstone, coal, and conglomerate area is the same age as the Bootlegger Cove Clay or older; a similar clay farther down Cook Inlet at ,0£ Other bedrock. Chiefly igneous and

Nikiski

COOK \w \*,

/ N L e T f

1972

c d

FIGURE 39. Urban and developing land, Kenai test site; 1951,1961,1967, and 1972, as interpreted from aerial photography.

B-77 ligious denomination found in Alaska. The lineate surface drainage basins and to provide in commercial strip along the coast was nearly con formation on deposit permeability. Poor tinuous. The terminal at Nikiski had four refin integration of streams in nonmountainous areas eries, and growth continued to the northeast. As indicates more permeable underlying materials previously mentioned, it was determined from in which recharge probably occurs. This relation published sources that nearly all changes ap is striking on the mountain flanks, where many pearing in figures 39c and 39d were the result of streams disappear because of infiltration. offshore petroleum development. Identification of surface water divides was use Results indicate that remotely sensed data, ful in defining probable ground-water basins and with some limitations, can be used to analyze lo in mapping regional ground-water flow direc cations and types of land changes resulting from tions. The Susitna River drains the study area. offshore petroleum development. Furthermore, Regional flow in the study area is toward the Su this type of information lends itself well to men sitna River, by way of 14 sub-basins. The stream suration of particular land-use categories, land- drainage and drainage basin overlays define di use changes, spatial patterns, and trends. Re rection of runoff, and ground-water flow, areas of motely sensed data, however, do not always con maximum storage, and the primary discharge tain the kind of information needed to identify zone the Susitna River. the relations between land-use and land-cover Areas of unconsolidated materials were subdi types. vided on the basis of differences in drainage and vegetation patterns, apparent slopes, and land- REFERENCES CITED forms. On l:250,000-scale Landsat imagery, ma jor landforms were separated into four types: Anderson, J. R., Hardy, E. E., Roach, J. R., and Witmer, R. exposed bedrock, bedrock with a thin cover of E., 1976, A land use and land cover classification system for use with remote sensor data: U.S. Geol. Survey Prof. overburden, terrace deposits, and alluvium. Fur Paper 964, 28 p. ther classification of the mountain flank areas State of Alaska, 1973, Statistical report: Alaska Dept. Natu was possible on l:30,000-scale color infrared pho ral Resources, Div. Oil and Gas, Juneau, Alaska. tography. Unconsolidated materials interpreted 1974, Alaska regional profiles; south-central region: as terrace deposits on l:250,000-scale Landsat Juneau, Alaska, v. 1, 255 p. imagery were separated into two classes: terrace Application of remotely sensed data for ground- levels and talus deposits. The large-scale photog water analysis near Denali, Alaska raphy shows that recharge areas occur where By James K. Richard, Technicolor Graphic Ser many streams disappear on the terraces. vices, Inc.2 A hydrogeologic model has been developed to explain recharge, discharge, and flow within the Favorable areas for ground-water exploration Susitna River valley ground-water system. The near Denali, Alaska have been identified by the model is based on interpretations made from use of remotely sensed data. Manual interpreta Landsat imagery that have been verified in the tions were made part of a computer-enhanced field and on l:30,000-scale color infrared aerial Landsat false-color composite (image #5470- photography. Areas of exposed bedrock and bed 19560, taken August 1, 1976) at 1:250,000 scale rock with thin overburden supply much of the and color infrared photographs at 1:30,000 scale. runoff to the Susitna River valley drainage basin. The interpretations were checked in the field Slopes are steep, locally nearing 50°, and the ma and modified as necessary. terial generally has a low permeability. Most in Four interpretive overlays were made indicat filtration occurs on the upper terrace level where ing features important to the development of a runoff from the mountains first flows over per targeting strategy and hydrogeologic model. The. meable, unconsolidated material. The large overlays present information on stream drain number of disappearing streams is evidence of age, drainage basins, and landforms at two scales rapid infiltration. Ground water is assumed to (1:250,000 and 1:30,000). flow toward the Susitna River from infiltration Analysis of drainage patterns was used to de- areas. The Susitna River valley is, therefore, as 2 Prepared under U.S. Geological Survey Contract sumed to be the area of maximum storage. 14-08-0001-16439. The model can also be used to locate areas B-78 where ground-water development is both feasi color composites. The resulting color images and ble and practical. Under most circumstances, an image that was contrast- and edge-enhanced ground-water supplies are most successfully ob by the EROS Digital Image Enhancement Sys tained in or near major storage areas. In this tem (EDIES) were analyzed to determine the op area, however, the Susitna River flood plain is timum image for investigating material-related relatively inaccessible. Soils and vegetation are geomorphic features. delicate and incapable of supporting continued The linear contrast enhancement best mini use. Saturated ground is quickly made impass mizes the "masking effect" of the vegetation in able by vehicular traffic during warmer seasons. the lowland area. Contrast in bands 4 and 5 was The better drained, more stable ground of the increased to reveal the maximum amount of de upper two terrace levels is best for exploration tail in the lowland area. On band 7, the enhance for ground-water supplies. These areas are most ment was intended to reduce contrast within likely to be developed, and the targeting strategy vegetation types in the valley and emphasize the can be considered consistent with potential land- tall shrub vegetation type along the lowland- use demands. mountain boundary. The resulting enhanced im Computer enhancement of Landsat digital data for age has a twofold advantage over the original im mapping material-related geomorphic featurs age: near Denali, Alaska 1) The enhanced image shows more detail in By Cynthia A. Sheehan, Technicolor Graphic Ser the mottled lowland area and sharper land- vices, Inc.3 water boundaries. The location of mor A series of computer enhancement processes aines, various terrace levels, and outwash were performed on Landsat digital data to dem deposits is based on patterns in the mot onstrate techniques for mapping material-relat tling and alinement of lakes. ed geomorphic features in lowland areas near 2) The tall shrub vegetation emphasized is Denali, Alaska. On a standard Landsat false-col concentrated at the base of the mountain, or composite, the lowland areas appear almost especially on talus slopes, and its lower homogeneously red, masking much of the geolog boundary approximately delineates the up ic detail. Moreover, in the photographic repro per boundary of the Quaternary terrace de duction process, tones are smoothed and the posits. This vegetation type also extends image loses sharpness. By using Landsat digital upstream into the mountains; therefore, data, contrast can be adjusted to enhance fea drainage in the upland areas is also en tures of interest and to produce a sharper, more hanced. easily interpreted image. Three terrace levels can be mapped in the Striping on the image caused by unequal re Denali area. The linear alinement of lakes along sponse of the Landsat multispectral scanner de margins of the Susitna River valley delineates to tectors can obscure linear features on the pographic breaks at the base and crest of the low ground. The application of a histogram normal est terrace. The upper two terraces were mapped ization function, commonly called destriping, re using tonal pattern alinement rather than lake moves this artificial pattern. locations. Field inspection of the lowland areas A destriped August 1,1976 subscene of Land- confirmed that tonal variations on the image cor sat image 5470-19560 covering a 118,623 ha area respond to variations in topography and vegeta of the Susitna River valley was analyzed using an tion on the ground. interactive multispectral image analysis system. In the highland area, drainage patterns were The four enhanced images produced were a lin used for a general structural analysis. The rec ear contrast enhancement, a ratio, a linear con tangular drainage of the Valdez Creek tributar trast enhancement of the ratio, and an enhanced ies has a pronounced northeast-southwest hybrid containing bands 5 and 7 and the band orientation. This area contains sedimentary and 5/band 6 ratio. Black-and-white transparencies metasedimentary rocks striking northeast. To of each band or individual ratio were recorded the north and south the drainage is more dendri with a laser-beam recorder and used to generate tic because it developed on more homogenous ig 3 Prepared under U.S. Geological Survey Contract neous and volcanic terranes. 14-08-0001-16439. The ratio composite and ratio composite with B-79 linear contrast enhancement of the Denali area Classification of vegetation in the Denali, Alaska are dark and contain very little detail in the low area with digital Landsat data By Wayne G. Rohde, Wayne A. Miller, and Charles land area. They were not useful for a study of this A. Nelson, Technicolor Graphic Services, Inc.4 type. However, one of the enhanced ratios, band 5/band 6, did show additional detail in the ter Landsats -1 and -2 provide resource scientists race areas. It was combined with bands 5 and 7 to with an opportunity to acquire multispectral form a hybrid false-color composite. This com data repetitively over large regions. Several in posite is similar in appearance to the linear-con vestigators have reported the application of trast-enhanced image. The increased detail in Landsat data for mapping wildland vegetation the terraces was due to the increased relative (Bentley and others, 1976; DeGloria and others, brightness of vegetation in depressions and small 1975; Krebs and Hoffer, 1976; La Perriere, 1976). valley slopes. Because there is more detail in the Successful application of these data to resource overall lowland area in band 4 than in ratio band mapping requires implementation of interpre 5/band 6, however, the hybrid false-color com tive methods that allow quick, consistent, accu posite proved no better than the linear-contrast- rate, and economical extraction of information. enhanced image. The objective of this project was to demonstrate For the EDIES false-color composite, the data the application of Landsat digital data for classi were destriped and linear-contrast enhanced us fication of wildland vegetation and to assess the ing a standard percentage of the- histogram for accuracy of this application. truncation limits. In this image, changes in vege Landsat-1 scene 5470-19560, taken on August tation on band 7 were enhanced from the original 1,1976 was selected for analysis as it provides re image, further masking rather than enhancing cent, cloud-free coverage of the entire 118,623-ha geologic features. study area near Denali. Bureau of Land Manage ment resource aerial photographs taken on Au An additional enhancement technique, edge gust 24, 1976 were available for strips along the enhancement, was used in creating the EDIES Denali highway. These photographs provide cov image. Edge enhancement is designed to en erage of about 30 percent of the study area and hance boundaries between features with similar were used to develop training statistics, associate spectral characteristics. In the highlands, the cover types with computer classes, and verify the drainage and its orientation are emphasized. Be accuracy of the classification. Aerial photo cause linear structural elements in the highland graphs taken in July 1977 at an approximate area are directly reflected in drainage develop scale of 1:31,000 were also used to verify accu ment, edge enhancement is useful for mapping racy. geologic structure. In lowland areas, the mottled A land-cover classification scheme was defined tones of the outwash and terrace deposits have on the basis of a framework being developed for no particular pattern. With limited analysis it the Denali area. Nine cover types were defined as appears that edge enhancement may, in certain follows: areas, homogenize the mottling rather than en 1. Clear water inland lakes and streams with hance it. low sediment loads; In the Denali area, the linear-contrast-en 2. Sediment-laden water streams and lakes hanced image is best for mapping material-re with high sediment loads, for example, Su- lated geologic features in the lowlands. Although sitna River; ratio images have proved useful in other study 3. Barren areas containing bare rock and soils areas, the ratio and hybrid images do not provide with less than 25 percent vegetation cover, for additional information at the Denali site. The example, roads, roadcuts, borrow pits, talus edge enhancement on the EDIES product em slopes, shoreline of lakes and rivers; phasizes structurally related drainage patterns 4. Tall shrub shrub communities composed of in the highland area, but does not appear advan alder (Alnus cripsa) and(or) willow (Salix sp.) tageous in studying lowland features. This type in thickets ranging from 2.5 to 4.5 m high with of enhancement would be more helpful if it were crown densities of 25 percent or greater; used in conjunction with the contrast enhance ment that emphasizes lowland features. 1 Prepared under U.S. Geological Survey Contract 14-08-0001-16439. B-80 5. Low shrub shrub communities composed of A clustered-stratified random sampling proce willow (Salix sp.) and(or) dwarf birch (Betula dure was used to estimate the accuracy of the nana x B. glandulosa) with heights ranging land cover types displayed on the map overlays. from decumbent forms to as large as 2.5 m On the basis of the area classified into each cover and having a crown density of 25 percent or type, it was estimated that 2,050 plots, each 0.45 greater; ha, would have to be sampled to estimate the 6. Tundra contains low, matlike plants or classification accuracy of each cover type with a cushion plants, for example, sedges, mosses, confidence interval of ± 5 percent at the 0.95 lichens, blueberries, bog cranberries, and lab- probability level. rador tea. Small stands of low shrubs, less Using sampling for proportion statistics, the than 25 percent crown density, or trees in pro overall classification accuracy was estimated to tected hollows may be found in this cover be 84.5 ± 4.2 percent at the 0.95 probability type; level. Classification accuracy was calculated for 7. Open conifer and low shrub stands of timber each of the nine land cover types as follows: 1) with a crown density of 25 to 75 percent and clear water, 100 percent; 2) sediment-laden wa an understory composed mainly of dwarf ter, 99.1 ± 0.6 percent; 3) barren, 99.4 ± 0.3 per birch and willow less than 2.5 m high; cent; 4) tall shrub, 100 percent; 5) low shrub, 84.3 8. Open conifer and tall shrub stands of timber ± 4.4 percent; 6) tundra, 89.8 ± 3.9 percent; 7) with a crown density of 25 to 75 percent and open conifer/low shrub, 85.2 ± 2.7 percent; 8) an understory of alder and (or) willow, more open conifer/tall shrub, 58.8 ±5.1 percent; and than 2.5 m high; and 9) dense conifer, 52.3 ± 6.2 percent. On the basis 9. Dense conifer stands of timber with a crown of the cost of purchasing Landsat data and aerial density of 75 to 100 percent and no visible un photographs from the EROS Data Center, as derstory. well as computer time and man-hours required Training statistics were derived using an unsu- for analysis and accuracy verification, the cost pervised approach. A 10-percent sample of the for mapping wildland vegetation over 118,000 ha pixels was processed with a spectral clustering was estimated to be $0.039/ha. algorithm. The algorithm identified 56 spectral classes in the sampled data. A mean brightness REFERENCES CITED value and variance for each spectral band and a Bentley, R. G., Jr., Salmon-Drexler, B. C., Bonner, W. J., and Vincent, R. K., 1976, A Landsat study of ephemeral covariance matrix were calculated for each com and perennial rangeland vegetation and soil: Bur. Land puter spectral class. These statistics were used in Management, Denver, Colorado, Final Report Type III, a maximum likelihood algorithm to classify each March 1975-December 1976, 234 p. picture element into one of the 56 computer DeGloria, S. D., Daus, S. J., Tosta, N., and Bonner, K., 1975, classes. Color infrared photography and field Utilization of high-altitude photography and Landsat-1 data for change detection and sensitive area analysis, in data collected in July 1976 were used to assign International symposium on remote sensing of environ each computer class to one of the nine land-cover ment, Michigan, 10th, 1975, Proceedings: Ann Arbor, classes in the classification scheme. Michigan Environmental Research Inst., v. 1, p. 359- 368. Evaluation of the classification results indi Krebs, P. V., and Hoffer, R. M., 1976, Multiple resource cated that water was mistakenly classified with evaluation of Region 2 U.S. Forest Service lands utiliz barren land on steep north-facing slopes. An im ing Landsat MSS data: NASA Goddard Space Flight age stratification procedure was used interac Center, Greenbelt, Md., Final Report Type III, July tively to outline mountainous barren areas. 1976, 298 p. La Perriere, A. J. L., Ill, 1976, Use of Landsat imagery for Picture elements within the barren areas, origi wildlife habitat mapping in northeast and east-central nally classified as water, were reclassified into Alaska: Alaska Univ., Fairbanks, Final Report, Decem the barren land class. After classification, a series ber 1976, NAS 5-20195, 39 p. of ground control points was selected to develop a mapping transformation for registering the Water resources studies in the Anchorage area classification results to U.S. Geological Survey By Chester Zenone l:63,360-scale topographic maps. Colored map overlays for parts of four map sheets (1:63,360- Anderson (1977) completed a report on artifi scale) were plotted on a flat-bed plotter. cial recharge experiments conducted on the Ship B-81 Creek alluvial fan from 1972 to 1975. Dearborn lain mainly by the Coast Range batholithic com (1977) reported that geologic and hydrologic plex, a heterogeneous group of plutonic rocks data collected during drilling of a 450-foot test and amphibolite-facies, metamorphosed, bedded well at the South Fork Eagle River alluvial fan rocks. The plutons range in emplacement age indicated that there were no aquifers present from Eocene to Miocene, in structure from gneis- that could support large-yield production wells. sic to massive, and in composition from gabbro to A digital model for steady-state (nonpumping) granite, with grandiorite predominant. The conditions in the confined ground-water system metamorphic age both of plutonic and bedded at Anchorage was developed; work began on a rocks is Eocene. Structural trends, isograds, and transient-state (pumping) model in November. lithologic units strike north to north-northwest. The model will be used as a guide to select hy- The northeasternmost part of the terrane is un draulically favorable sites for future public-sup derlain by relatively less metamorphosed Trias- ply wells and to predict the effects of large- sic and Jurassic volcaniclastic and plutonic volume pumping on regional water levels. rocks. Mineral occurrences consist of porphyry An updated inventory of ground-water data molybdenum deposits in Miocene granite plu in the Eagle River-Chugiak area has been com tons, and sulfide vein and disseminated deposits pleted and preparation of ground-water inter in the metamorphic rocks that have been pros pretive maps was underway in November 1977. pected for gold, silver, copper, lead, and zinc. Figure 40 is duplicated for convenience as figure REFERENCES CITED 48 at the end of the report. The central third of the map area is underlain Anderson, G. S., 1977, Artificial recharge experiments on the Ship Creek alluvial fan, Anchorage, Alaska: U.S. Geol. by greenschist- to amphibolite-facies, metamor Survey Water Resources Inv. WRI-77-38, 39 p. phosed sedimentary and volcanic rocks and by Dearborn, L. L., 1977, Ground-water investigation at the al variously metamorphosed plutonic rocks ranging luvial fan of the South Fork Eagle River, Anchorage, in composition from gabbro to quartz monzonite Alaska Results of test drilling, 1976: U.S. Geol. Survey and in emplacement age from Cretaceous to Mio Open-File Report 77-439, 9 p. cene. Regional metamorphic grade increases northeastward. Potassium-argon studies show SOUTHEASTERN ALASKA Cretaceous metamorphic ages. Premetamorphic ages of the bedded rocks probably are late Paleo New geological map of Ketchikan and Prince Rupert quadrangles, southeastern Alaska zoic to late Mesozoic, with tectonic inliers of By H. C. Berg, R. L. Elliott, J. G. Smith, and R. D. rocks possibly as old as Precambrian. Structural Koch trends, isograds, and lithologic units strike northwest to west. Mineral occurrences include A major goal of the Ketchikan project (which traces of molybdenite in some plutons, and sul also includes the Prince Rupert quadrangle to fide vein and disseminated deposits in the meta the south) was reached in September 1977 with morphic and plutonic rocks that have been the completion of field studies of geology, geo prospected for antimony, gold, silver, lead, and chemistry, geophysics, and mineral resources. A zinc. l:250,000-scale reconnaissance geologic map of The remaining sixth of the map area lies the quadrangles was published in January 1978 southwest of the central terrane and contains the (Berg and others, 1978), and additional maps most varied lithology and most complete suite of and reports describing the geochemistry, geo stratified rocks in the Ketchikan and Prince Ru physics, satellite imagery interpretations, and pert quadrangles. It also includes the least meta mineral resources are scheduled for release by morphosed pre-Tertiary rocks in the map area. June 1978. For administrative reasons, the Ket The bedded rocks range in age from Silurian or chikan project was incorporated into the Alaska older to Late Jurassic, and the plutonic rocks Mineral Resource Assessment Program (AM- from Silurian or older to Cretaceous. Especially RAP) in 1975. distinctive units include a Silurian or older stock The new geologic map, generalized for this re of leucocratic trondhjemite, middle(?) Paleozoic port in figure 40, includes three major geologic rhyolite, and a Jurassic or Cretaceous zoned ul- terranes. The east half of the map area is under tramafic complex that contains spectacular B-82 zones of rhythmically layered dunite and perido- rocks associated with the Quartz Hill (Wilson tite. Mineral occurrences include copper-bearing Arm area) molybdenite deposit have been com barite veins in the Paleozoic rhyolite, veins car pleted. The intrusive rocks form two composite rying gold, silver, and other metals in Upper Ju hypabyssal stocks separated at the surface by a rassic andesitic metatuff, and stratiform narrow septum of gneiss (Elliott and others, titaniferous magnetite deposits in the zoned ul- 1976; Hudson and others, 1977). The plutons tramafic rocks. contain several textural facies ranging from fine- Selected highlights of the Ketchikan-Prince to medium-grained seriate biotite granite to fel- Rupert map area include: sic porphyry with very fine-grained to aplitic (1) The boundary between the central and groundmasses. Sixteen samples representative of eastern terranes is an abrupt structural discord the textural facies were analyzed for trace ele ance that may be the metamorphosed trace of a ments by semiquantitative spectrographic meth major late Mesozoic tectonic suture; ods. (2) The central terrane contains a swarm of Cretaceous garnet-bearing feldspar (plagioclase) A uniform felsic composition characterizes the porphyry stocks and smaller plutons that in major-element analyses; SiO2 ranges from 74.1 to trude variously metamorphosed pelitic and an 77.5 percent, CaO from 0.2 to 1.0 percent, K2O desitic rocks. The swarm of plutons, which has from 4.2 to 4.8 percent, and Na^ from 3.6 to 4.4 been traced for at least 80 km northwest of the percent. The uniformity of composition is illus map area (Berg and others, 1976), terminates trated by the plot of normative Q-Or Ab+An abruptly at the boundary of the eastern terrane; ratios (fig. 41). The differentiation index for (3) The central terrane contains northeast- these (the sum of normative Q+Or+Ab) is the dipping to nearly flat thrust faults and fault compositional parameter that shows the most zones that probably were regionally metamor variation, ranging from 91.3 to 97.3. phosed in Cretaceous time. The thrusts are roughly parallel to the axial surfaces of semire- The trace-element composition of the samples cumbent isoclinal folds overturned to the south is rather bland and shows no distinct enrichment west; and in any of the analyzed elements. Many elements (4) A potentially economic porphyry molyb are present in amounts below their detection denum deposit occurs in a Miocene granite por limits (for example, silver, arsenic, boron, bis phyry stock in the eastern terrane. Molybdenite muth, antimony, tin, tungsten, zinc), and most also occurs in the eastern terrane in Miocene others are present in low to average amounts if quartz porphyry dikes, in the Triassic and Juras compared to the average for low-calcium granites sic rocks at the northeastern corner of the map compiled by Turekian and Wedepohl (1961). area, and in at least one of the Cretaceous feld Some elements present in low to average spar porphyry stocks in the central terrane. amounts are gallium, 7-18 ppm; lanthanum, < 10-30 ppm; manganese, 220-540 ppm; lead, REFERENCES CITED 17-34 ppm; scandium, 1.1-4.2 ppm; vanadium, Berg, H. C., Elliott, R. L., Koch, R. D., Cartin, R. B., and 3.5-12 ppm; ytterbium, 0.5-5.9 ppm; and zircon Wahl, F. A., 1976, Preliminary geologic map of the Craig ium, 22-92 ppm. Barium (40-930 ppm) and D-l and parts of the Craig C-l and D-2 quadrangles, strontium (90-490 ppm) show the widest ranges Alaska: U.S. Geol. Survey Open-File Report 76-430, 1 of abundance. Beryllium (1.5-8.5 ppm) and nio sheet, scale 1:63,360. bium (11-83 ppm), on the average (4 and 25 Berg, H. C., Elliott, R. L., Smith, J. G., and Koch, R. D., 1978, Geologic map of the Ketchikan and Prince Rupert ppm, respectively), may be slightly enriched rel quadrangles, Alaska: U.S. Geol. Survey Open-File Re ative to many other felsic rocks (Turekian and port 78-73-A, 1 sheet, scale 1:250,000. Wedepohl, 1961). Molybdenum is below detec tion limits (2.2 ppm) in all but two samples; these Chemistry of Quartz Hill intrusive rocks, Ketchi two samples contain 8 and 64 ppm molybdenum, kan quadrangle respectively. There is no obvious correlation of By Travis Hudson, Raymond L. Elliott, and James other trace elements with these two greater mo G. Smith lybdenum values. Major- and trace-element analyses of intrusive In summary, the intrusive rocks associated B-83 132° 130°

Caper T Northumberland

FIGURE 40. Generalized geologic map of Ketchikan and Prince Rupert quadrangles, southeastern Alaska. Scale 1:1,000,000 or 1 inch equals approximately 26 km. Base map from National Atlas of the United States, U.S. Geological Survey, 1970. with the Quartz Hill molybdenite deposit are dis enriched in any of the trace elements that were tinctly salic and uniform in the major-element determined. This lack of enrichment could be in composition. This composition suggests that the terpreted as evidence against a differentiation original magma represented either an initial melt origin from the magma. Additional chemical and formed at depth or a highly differentiated resid isotopic studies are underway to help clarify the ual magma that was cleanly separated from its origin of the intrusive rocks and better under parent materials. The trace-element composi stand the genesis of the associated molybdenum tion is distinctly bland and, in most samples, not deposits. B-84 REFERENCES CITED

CORRELATION OF MAP UNITS Elliott, R. L., Smith, J. G., and Hudson, Travis, 1976, Upper I QUATERNARY Tertiary high-level plutons of the Smeaton Bay area, \QUATERNARY southeastern Alaska: U.S. Geol. Survey Open-File Re /AND TERTIARY port 76-507, 15 p. Miocene TERTIARY Hudson, Travis, Elliott, R. L., and Smith, J. G., 1977, Inves [ Eocene tigations of the Wilson Arm molybdenite deposit, in TERTIARY OR Blean, K. M., ed., The United States Geological Survey ! CRETACEOUS in Alaska; accomplishments during 1976: U.S. Geol. Upper or > JURASSIC Survey Circ. 751-B. p. B74. Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of .JURASSIC OR the elements in some units of the earth's crust: Geol. TRIASSIC Soc. America Bull., v. 72, p. 75-192. J Upper Triassic TRIASSIC MESOZOIC OR PALEOZOIC ^Middle and Minor-metal content of Cretaceous greenstone J upper Paleozoic near Juneau, Alaska PALEOZOIC By Arthur B. Ford and David A. Brew 'OR OLDER Silurian or older Greenstone and other metavolcanic rocks of the Douglas Island Volcanics of Lathram, Pom- DESCRIPTION OF MAP UNITS eroy, Berg, and Loney (1965) are widespread in UNCONSOLIDATED DEPOSITS, UNDIVIDED (Quaternary) the lower grade western part of a Barrovian re VOLCANIC ROCKS (Quaternary and Tertiary) gional metamorphic belt near Juneau (Ford and

1 PLUTONIC ROCKS, UNDIVIDED (Miocene) Brew, 1977a). The probable original rocks were

PLUTONIC ROCKS, UNDIVIDED (Eocene) locally pillow-bearing submarine basalt flows, tuff, and agglomerate, in places mixed with vol j PLUTONIC ROCKS, UNDIVIDED (Tertiary or Cretacepus) canic-derived graywacke and shale containing a GRAVINA ISLAND FORMATION AND UNNAMED CORRELATIVE ROCKS (Upper or Middle Jurassic) sparse Cretaceous marine fauna (Ford and Brew, [ Ultramafic and other plutonic rocks 1977b). In the Juneau area the volcanic terrane Metasedimentary rocks makes up Douglas Island, the east side of Lynn

| Metavolcamc rocks Canal south of Berners Bay, and Glass Peninsula on eastern Admiralty Island. Metamorphism was | TEXAS CREEK GRANODIORITE (Jurassic or Triassic) mainly in the prehnite-pumpellyite meta- METAMORPHOSED VOLCANIC AND SEDIMENTARY ROCKS (Jurassic or Triassic) graywacke facies, increasing eastward to the METAMORPHOSED SEDIMENTARY AND VOLCANIC ROCKS (Upper Triassic) lower greenschist facies on eastern Douglas Is PARAGNEISS AND AMPHIBOLITE (Mesozoic or Paleozoic) land.

METAMORPHIC ROCKS, UNDIVIDED (Mesozoic or Paleozoic) The metavolcanic terrane in the Juneau area I METAMORPHOSED SEDIMENTARY AND MINOR has been proposed by Berg, Jones, and Richter VOLCANIC ROCKS (Middle and upper Paleozoic) (1972) to be part of a late Mesozoic basinal ande- | FELSIC METAVOLCANIC ROCKS (Paleozoic or older) sitic island-arc system, named the Gravina-Nut- PLUTONIC ROCKS, CHIEFLY TRONDHJEMITE (Silurian or older) zotin belt, that extended from southern south METAMORPHOSED SEDIMENTARY AND VOLCANIC ROCKS (Silurian or older) east Alaska, near Ketchikan, to the eastern Alaska Range. In an analysis of the tectonic his SYMBOLS tory of this belt, Connelly (1976, p. 147) assumes .... Contact. Approximately located; dotted where concealed the composition of the Douglas Island to be an- ... High-angle fault. Dashed where inferred; dotted where concealed desitic. It is now known, however, that the green

* Thrust fault. Dashed where concealed. Sawteeth on stones on and near Douglas Island have only a upper plate limited range of olivine tholeiitic compositions (Ford and Brew, 1977b), and correlative green FIGURE 40. Continued. stone near Berners Bay is alkali basaltic (Irvine, 1973), which raises considerable uncertainty about including this region in the proposed andesitic island-arc belt. Although volcanism may B-85 Q

Or Ab + An

FIGURE 41. Plot of normative Q Or Ab-f An ratios for Quartz Hill intrusive rocks, Ketchikan quadrangle.

have been approximately coeval in one or more petrologic character of the original volcanic basins along the Gravina-Nutzotin trend in rocks, which cannot be identified mineralogically interior southeast Alaska, it may have been asso owing to extensive metamorphic alteration; (2) ciated with different tectonic regimes in differ understand the tectonic setting of this volcanism ent sectors of the belt. by comparisons with well-known volcanic re Few published analytical data on the rocks in gions elsewhere; and (3) establish the nature of the Juneau area are available for comparing geo- regional variation in the proposed Gravina-Nut chemical and petrologic characteristics with zotin volcanic belt, which will contribute to a other parts of the proposed andesitic-arc belt. As better understanding of the tectonic history of part of our investigation of the Juneau 1:250,000- this part of southeast Alaska. The study, addi scale quadrangle (Brew and Ford, 1974; Ford and tionally, provides baseline data for investigation Brew, 1977a), we therefore have undertaken a of the mineral resources of the Juneau area and study of the chemistry of this terrane in an at for use in correlating poorly fossiliferous green tempt to (1) determine as closely as possible the stone sequences of the region. (Near Juneau, pil- B-86 low-bearing greenstone and greenschist in places samples. The reported averages were calculated contain late Paleozoic or Triassic fossils but are using only determined values and neglecting otherwise difficult to distinguish from the upper those below limits of determinability. On a simi Mesozoic volcanic rocks.) lar basis, palladium and platinum contents of the Quantitative analyses for selected minor met Juneau samples respectively average 12 ppb and als are shown in table 4 for 28 samples previously 10 ppb, and the average Pt:Pd and Pt:(Pt + Pd) analyzed for major elements (Ford and Brew, ratios are respectively 0.83 and 0.47. These aver 1977b). Cobalt, chromium, copper, nickel, scan ages indicate that the metavolcanic rocks in the dium, and vanadium were determined by spec- Ketchikan area are enriched considerably in trographic analysis; and the platinum-group platinum compared to the rocks near Juneau and metals palladium, platinum, and rhodium were that the rocks from both areas are virtually iden determined by the same combined fire-assay and tical in palladium, as well as rhodium, content. spectrographic method used in the studies on Averages calculated as the preceding ones correlative rocks reported by Page, Berg, and may, however, be misleadingly high, depending Haffty (1977). on the percentage of samples that contain an ele Palladium is the only platinum-group metal ment below its limit of detectability. More realis found to be almost consistently present above its tic averages are obtained, we believe, by using all limit of determinabilty, which is 4 parts per bil data and assuming a value of half the limit of de lion (ppb). It is detectable in all 28 samples and terminability for all results below this limit. Cal its amount determinable in 27 samples. Plati culated on this basis, average contents of num, with a limit of determinability of 10 ppb, is palladium and platinum in the Juneau samples detectable in 19 samples (69 percent of the total) are respectively 12 ppb and 6 ppb, and average and determinable in only 5 samples (17 percent Pt:Pd and Pt:(Pt + Pd) ratios are 0.51 and 0.34. of the total). Rhodium, with a limit of determina- For comparison, averages recalculated similarly bililty of 5 ppb, was not detected in any samples. for the metavolcanic rocks from Ketchikan, from Contents of other minor metals in table 5 are data in Page, Berg, and Haffty (1977), are as fol within detection limits for all samples. lows: palladium, 8 ppb; platinum, 7 ppb; Pt:Pd, No published data from other parts of the Gra- 0.88; and Pt:(Pt + Pd), 0.47. Comparison of these vina-Nutzotin belt are available for comparison averages shows different relations than the com with our analytical results, except for the plati parison of averages based only on values above num-group metals in the southern part of the limits of determinability, owing to the much belt near Ketchikan. For that area, Page, Berg, greater percentage of samples with determinable and Haffty (1977) report average contents of pal palladium in the Juneau suite (97 percent) than ladium and platinum to be respectively 11.5 ppb in the Ketchikan suite (60 percent). Using these and 15.7 ppb and the average ratios Pt:Pd and averages, the metavolcanic rocks from both areas Pt:(Pt + Pd) to be respectively 1.37 and 0.578. have nearly the same platinum content, but Rhodium is below detectability in all 40 of their those from Juneau are considerably enriched in TABLE 4. Average content of minor metals, in parts per palladium. million, of 28 metavolcanic rock samples from the Juneau The cogenetic relation of the late Mesozoic area, compared with two average basalts volcanism and Alaskan-type mafic and ultrama-

[Palladium determinations by Joseph Haffty and A. W, Haubert; others by fic plutonism (Berg and others, 1972; Irvine, R. E. Mays, Average basalt and olivine tholeiite compositions from 1973) is supported by similarities in platinum, Prinz (1967); tr., trace] palladium, and rhodium ratios (Page and others, Average Average olivine basalt tholeiite 1977). The Alaskan-type complexes are concen

Arithmetic Standard trated mainly in the southern part of the volcanic Range deviation belt, and none occurs within the terrane sampled Cobalt 62 25-95 43 in the present study. Although similar in having Chromium- 207 46-340 162 210 low rhodium contents, the metavolcanic rocks in Copper 92 36-200 119 75 Nickel 62 22-220 126 the Juneau and Ketchikan areas differ greatly in Scandium 44 21-74 27 26 their platinum\and palladium ratios, which may Vanadium 222 140-280 247 183 suggest that the Juneau-area volcanism was not Palladium 0.012 tr.- 0.019 0.003 cogenetic with Alaskan-type plutonism, or that B-87 the ratios were modified by magmatic differenti Grybeck, Donald, Brew, D. A., Johnson, B. R., and Nutt, C. ation or metamorphism. Several small ultra- J., 1977, Ultramafic rocks in part of the Coast Range batholithic complex, southeastern Alaska, in Blean, mafic complexes are known to occur on the main K.M., ed., The United States Geological Survey in land and islands east of Glass Peninsula (Gry- Alaska; accomplishments during 1976: U.S. Geol. Sur beck and others, 1977), but no data are available vey Circ. 751-B, p. B82-B85. on their platinum-group metal contents. Alas- Irvine, T. N., 1973, Bridget Cove volcanics, Juneau area, kan-type complexes elsewhere show a consider Alaska; possible parental magma of Alaskan-type ultramafic complexes: Carnegie Inst. Washington Yearbook able range in platinum and palladium ratios, and 72, p. 478-491. therefore we consider our data inconclusive for Lathram, E. H., Pomeroy, J. S., Berg, H. C., and Loney, R showing a genetic relation between volcanism in A., 1965, Reconnaissance geology of Admiralty Island, the Juneau area and Alaskan-type mafic and ul- Alaska: U.S. Geol. Survey Bull. 1181-R, 48 p. tramafic plutonism. The data do indicate, how Page, N. J, Berg, H. C., and Haffty, Joseph, 1977, Platinum, palladium, and rhodium in volcanic and plutonic rocks ever, distinct regional variations in platinum- from the Gravina-Nutzotin belt, Alaska: U.S. Geol. Sur group metal characteristics within this late vey Jour. Research, v. 5, p. 629-636. Mesozoic volcanic belt in southeast Alaska. Prinz, Martin, 1967, Geochemistry of basaltic rocks; trace The content of other analyzed minor metals is elements, in Hess, H.H., and Poldervaart, Arie, eds., Ba about normal for rocks of basaltic composition, salts, Vol. 1: New York, John Wiley, p. 271-323. particularly of the olivine tholeiite type, except for comparatively low nickel abundance (table Intrusive rocks in the Fairweather Range, Glacier 4). These results support earlier conclusions Bay National Monument, Alaska By David A. Brew, Bruce R. Johnson, Arthur B. (Ford and Brew, 1977b) that the late Mesozoic Ford and Robert P. Morrell volcanic terrane near Juneau is compositionally unlike the andesitic terranes of the northern and Completion of reconnaissance geologic map southern parts of the Gravina-Nutzotin belt. ping in the high part of the Fairweather Range, The tectonic setting of this volcanism in the Ju Alaska, indicates that about 30 percent of the neau area is enigmatic. Tholeiitic volcanism may Fairweather province (fig. 42), as defined by have been of the island-arc type, but present MacKevett and others (1971) is underlain by in data do not preclude other possibilities, such as trusive rocks of diverse types and ages (fig. 42). an ocean island, or a marginal ocean basin set The oldest group of intrusive rocks consists of ting. layered gabbros of inferred Precambrian or early Paleozoic age (Brew and others, 1977) that form REFERENCES CITED an irregular belt along the axis of the range. Lo cally foliated granitic rocks of inferred Creta Berg, H. C., Jones, D. L., and Richter, D. H., 1972, Gravina- ceous or Tertiary age occur within the gabbro Nutzotin belt tectonic significance of an upper Meso zoic sedimentary and volcanic sequence in southern and belt and to the east toward Johns Hopkins Inlet. southeastern Alaska, in Geological Survey research, Bodies of unfoliated granitic rocks of inferred 1972: U.S. Geol. Survey Prof. Paper 800-D, p. D1-D24. middle Tertiary age form another irregular belt Brew, D. A., and Ford, A. B., 1974, Geology of the Juneau generally to the east of the gabbro belt, but over Icefield and adjacent areas, in Carter, Claire, ed., U.S. lapping to the south. Extensive bodies of well- Geological Survey Alaska program, 1974: U.S. Geol. Survey Circ. 700, p. 54-56. foliated granitic rocks of inferred Cretaceous age Connelly, William, 1976, Mesozoic geology of the Kodiak are exposed in the Coastal province to the west of Islands and its bearing on the tectonics of southern the Fairweather province and in the Geikie prov Alaska: Santa Cruz, California Univ., Ph. D. thesis, 197 ince to the east. P- The cumulus-type layered gabbros mainly in Ford, A. B., and Brew, D. A., 1977a, Truncation of regional metamorphic zonation pattern of the Juneau, Alaska, trude a regionally extensive hornblende schist area by the Coast Range batholith, in Blean, K.M., Ed., and gneiss unit (D. A. Brew, unpub. data, 1978). The United States Geological Survey in Alaska; accom The compositions of the different bodies appear plishments during 1976: U.S. Geol. Survey Circ. 751-B, to vary significantly only in hornblende, magne p. B85-B87. tite, and ilmenite content. In general, the cumu 1977b, Chemical nature of Cretaceous greenstone near Juneau, Alaska, in Blean, K.M., ed., The United lates are fine- to coarse-grained, light- to dark- States Geological Survey in Alaska; accomplishments gray and brown (olivine-) gabbro, gabbronorite, during 1976: U.S. Geol. Survey Circ. 751-B, p. B88-B90. and norite, which have color indices of 40 to 80 B-88 137°

^y %^jji(i

Glaciers Intrusive rock patterns ore shown in gtoc/er->buf nof ! i i ! i I TtKTIAKY in worer-covereowafer-covered oreoareas U ' I I I I I I I ll > QjJ ______Locally' foliated____ granitic* rocks ;I L.KtiAL.tuui>rPFTAPFOllS Geologic_ T . province" 7~"~ '//////y s boundnrv > CRETACEOUS Well-foliated granitic rocks ) Eastern boundary

, ' j rt f PALEOZOIC OR Layered gabbro ; PRECAMBRIAN

FIGURE 42. Sketch map of western Glacier Bay National Monument, showing geologic provinces, intrusive rocks, and Tarr Inlet suture zone. All associated migmatites are included within the intrusive rock bodies shown. B-89 and contain local layers of pyroxenite. The layer conduit for magmas generated near the conti ing is crude to moderately well developed in most nental margin during the middle Tertiary, a time places, but is very well developed locally. The of significant compressional strike-slip motion most complete descriptions of these rocks are along the North American plate at this latitude given by Rossman (1963) and Plafker and (Atwater, 1970). Most simple plate tectonic mod MacKevett (1970). els, however, require subduction at a continental The locally foliated granitic rocks of inferred margin to generate magmas (Dickinson, 1972). Cretaceous or Tertiary age intrude mainly a re gionally extensive biotite schist unit (D. A. Brew, REFERENCES CITED unpub. data, 1978) and have extensive stock- Atwater, Tanya, 1970, Implications of plate tectonics in the work-type migmatites associated with them. The Cenozoic tectonic evolution of western North America: most common rock types are fine- to medium- Geol. Soc. America Bull, v. 81, p. 3513-3535. grained, light-gray (hornblende-) biotite quartz Brew, D. A., Loney, R. A., Kistler, R. W., Czamanske, G. K., diorite, tonalite, granodiorite, and diorite, with Gromme, C. S., and Tatsumoto, M., 1977, Probable Pre- color indices of 20 to 30. cambrian or lower Paleozoic rocks in the Fairweather Range, Glacier Bay National Monument, Alaska, in In the Fairweather province, the unfoliated Blean, K. M., ed., The United States Geologial Survey granitic rocks of inferred middle Tertiary age in Alaska; accomplishments during 1976: U.S. Geol. mainly intrude regionally extensive biotite schist Survey Circ. 751-B, p. B91-B93. and gneiss units as well as the phyllite and Brew, D. A., Loney, R. A., and Muffler, L. J. P., 1966, Tec graywacke semischist that is the protolith of tonic history of southeastern Alaska: Canadian Inst. Mining and Metallurgy Spec. Vol. 8, p. 149-170. those units. Spectacular stockwork and irregular Brew, D. A., and Morrell, R. P., 1978, Tarr Inlet suture zone, banded gneiss migmatites are associated with al Glacier Bay National Monument, Alaska, in Johnson, most all of the bodies. A wide variety of rock K. M., ed., The United States Geological Survey in Alas types is present; most common are medium- ka; accomplishments during 1977: U.S. Geol. Survey to-coarse-grained, light-gray (garnet-) Circ. 772-B, p. B90. Dickinson, W. R., 1972, Evidence for plate-tectonic regimes (hornblende-) biotite granodiorite, granite, and in the rock record: Amer. Jour. Science, v. 272, p. 551- tonalite, with color indices of 8 to 15. Some bo 576. dies are locally prophyritic. Loney, R. A., Brew, D. A., Muffler, L. J. P., and Pomeroy, J. The distribution of the different groups of in S., 1975, Reconnaissnace geology of Chichagof, Baranof, and Kruzof Islands, southern Alaska: U.S. Geol. Survey trusive rocks in the Fairweather and adjacent Prof. Paper 792,105 p. Coastal and Geikie provinces suggests several MacKevett, E. M., Jr., Brew, D. A., Hawley, C. C., Huff, L. possible relations. First is the already described C., and Smith, J. G., 1971, Mineral resources of Glacier (Brew and others, 1977) restriction of the layered Bay National Monument, Alaska: U.S. Geol. Survey gabbros to the lithically monotonous country Prof. Paper 632, 90 p. Plafker, George, and MacKevett, E. M., Jr., 1970, Mafic and rock of the Fairweather province and the similar ultramafic rocks from a layered pluton at Mount Fair- restriction of the locally foliated granitic rocks of weather, Alaska, in Geological Survey research 1970: Cretaceous or Tertiary age. The absence of the U.S. Geol. Survey Prof. Paper 700-B, p. B21-B26. well-foliated granitic rocks of inferred middle Rossman, D.L., 1963, Geology and petrology of two stocks of Cretaceous age from the lithically monotonous layered gabbro in the Fairweather Range, Alaska: U.S. rocks of the Fairweather province suggests that Geol. Survey Bull. 1121-F, 50 p. the area was somehow isolated from the very Tarr Inlet suture zone, Glacier Bay National Monu wide-spread plutonism that affected southeast ment, Alaska ern Alaska at that time (Brew and others, 1966; By David A. Brew and Robert P. Morrell Loney and others, 1975). The middle Cretaceous plutonism characterizes the Geikie province, in Recent reconnaissance geologic mapping west cluding the Tarr Inlet suture zone (fig. 42) as de of Tarr Inlet in Glacier Bay National Monument scribed in the accompanying article (Brew and and previous mapping to the south as far as Tay- Morrell, 1978). lor Bay on Icy Strait suggest that a 5- to 12-km- The location of the greatest volume of granitic wide and at least 100-km-long zone of complex rocks of inferred middle Tertiary age close to the geology between the predominantly metamor- Tarr Inlet suture zone (fig. 42; also D. A. Brew, phic rocks of the Fairweather province (MacKe unpub. data, 1978) suggests that the zone was a vett and others, 1971) to the west and the B-90 predominantly intrusive rocks of the Geikie According to both Rossman and Seitz, fold province to the east represents a suture between structures in the Geikie province cannot be gen significantly different terranes (fig. 42). eralized very well owing mainly to the large The Fairweather Range consists of about 30 amounts of intrusive rocks that are present, percent intrusive rocks of diverse types and ages faulting, and the resulting discontinuity of units. (Brew and others, 1978), 25 percent hornblende Our impression is that the folds are simpler than schist and gneiss in one regionally continuous those in the Fairweather Range, but this simplic unit, and 45 percent biotite schist and gneiss and ity cannot be clearly documented. protolithic graywacke semischist and phyllite. The suture zone itself, where best exposed in The country rocks in the range are probably of the Tarr Inlet-Johns Hopkins Inlet area, is un Precambrian or early Paleozoic age (Brew and derlain by about 20 percent elongated bodies of others, 1977) and were deposited as a thick pile highly foliated biotite-hornblende quartz diorite of marine graywacke and shale with interbedded whose age is inferred to be Cretaceous, the same thick volcanic flows or sills of intermediate com as the dominant intrusive rock throughout the position to the west. Geikie province. The country rocks consist of Fold structures in the country rock are poorly about 40 percent phyllite, slate, conglomerate, understood, but the complexity of folding ap and chert in units that are continuous and coher pears to decrease from west to east. The western ent at kilometer scale, but that have many inter part of the range is characterized by steep- nal discontinuities of individual lithic units; 30 limbed isoclinal folds with northwest-striking percent greenstone, greenschist and other meta- nearly vertical axial planes and moderately volcanic rocks that are apparently more coherent plunging axes. These folds appear to have re internally; and 10 percent gray marble in lenses folded an earlier generation of folds, but the that range in size from a few meters in maximum original orientations have not been determined. exposed dimension to as much as 5 km long and To the east, toward the suture zone, both steep- several tens of meters thick. These country rocks and shallow-limbed folds with north-northwest- are unfossiliferous and their age is unknown. On striking nearly verticaly axial planes and moder the basis of general proportions and similarity of ately plunging axes are present. Fewer key layers lithic types, we suggest that they may be eqiva- are present than to the west, and earlier folds lent to a fossiliferous Permian unit exposed in have not been recognized. the northeastern part of the monument (D. A. The rocks of the Geikie province, east of the Brew, unpub. data, 1978). The rocks in the su suture zone, consist of a varity of Cretaceous and ture zone appear to have been deposited as shale, Tertiary granitic rocks which altogether underlie conglomerate, graywacke, tuffs or flows, chert, about 60 percent of the province. The country and thin limestones in a marine environment. rocks are a diverse assemblage of hornfelsed peli- Fold orientations in the suture zone appear to tic and semipelitic rock, marble and greenstone, vary from unit to unit. Some of the marble layers and amphibolite: underlying approximately 30, have small folds with shallow plunges and north- 25, and 2 percent, respectively, of the whole striking, moderately west-dipping axial planes. A province (the remaining 3 percent is the suture 1-km-long marble layer within a dominantly zone itself, which is included in the Geikie prov phyllitic unit apparently defines a macrofold of ince). These country rocks are inferred to be of about the same orientation. Although the fold middle Paleozoic age on the basis of their prob situation in the greenstones is poorly known, one able equivalence to fossiliferous rocks in the of the larger units is characterized by relatively Chilkat province adjacent to the east. These simple chevron and conjugate kink folds. One of rocks were probably deposited as a thick section the most significant structural features in the of marine shale, graywacke, arkose, volcanic zone is the discontinuity of individual layers flows or tuffs, and limestone (Rossman, 1963; within the mappable units and the abundance of MacKevett and others, 1971) in a shallower envi relatively small (a few kilometers long by a few ronment than that of the older rocks in the Fair- hundred kilometers thick) units. Some of these weather province. The most complete descrip may be inherited from the original depositional tions of the country rocks available are in Ross environment, but tectonic disruption is consid man (1963) and Seitz (1959). ered a more likely cause. B-91 The suture zone as presently mapped (fig. 42) southeastern Alaska, in Geol. Survey Prof. Paper 800-D, widens westward in the northern reaches of the p. D1-D24. Brew, D. A., Johnson, B. R., Ford, A. B., and Morrell, R. P., Brady Glacier, but the geology of that area is not 1978, Intrusive rocks in the Fairweather Range, Glacier well known, and it is possible that rocks inferred Bay National Monument, Alaska, in Johnson, K.M., to belong to the zone are instead part of the Fair- ed., The United States Geological Survey in Alaska; ac weather province. In the vicinity of Taylor Bay complishments during 1977: U.S. Geol. Survey Circ. the zone is probably no more than 5 km wide (fig. 772-B, p. B88. Brew, D. A., Loney, R. A., Kistler, R. W., Czamanske, G. K., 42) and consists of greenschist and greenstone Gromme, C. S., and Tatsumoto, M., 1977, Probable Pre with minor marble, chert, and graywacke semi- cambrian or lower Paleozoic rocks in the Fairweather schist, bounded on the west beneath the Brady Range, Glacier Bay National Monument, Alaska, in Glacier by graywacke semischist and slate of the Blean, K. M., ed., The United States Geological Survey Fairweather province and on the east by locally in Alaska; accomplishments during 1976: U.S. Geol. garnet-bearing amphibolite and gneiss. Survey Circ. 751-B, p. 91-93. Brew, D. A., Loney, R. A., and Muffler, L. J. P., 1966, Tec The suture zone extends north into British Co tonic history of southeastern Alaska: C. I. M. Spec. Vol. lumbia underneath the Grand Pacific Glacier; no 8, p. 140-170. geologic mapping is available for about 100 km in Loney, R. A., Brew, D. A., Muffler, L. J. P., and Pomeroy, J. that direction. To the south the zone projects to S., 1975, Reconnaissance geology of Chichagof, Baranof, wards the Inian Peninsula on Chichagof Island, and Kruzof Islands, Alaska: U.S. Geol. Survey Prof. Pa per 792,105 p. which Loney, Brew, Muffler, and Pomeroy MacKevett, E. M., Jr., Brew, D. A., Hawley, C. C., Huff, L. (1975) show as dominantly Mesozoic country C., and Smith, J. G., 1971, Mineral resources of Glacier rocks to the west separated by intrusive rocks Bay National Monument, Alaska: U.S. Geol. Survey from probably middle Paleozoic country rocks to Prof. Paper 632,90 p. Plafker, George, Jones, D. L., Hudson, Travis, and Berg, H. the east. Plafker, Jones, Hudson, and Berg C., 1976, The Border Range fault system in the Saint (1976) consider the Inian Peninsula to be east of Elias Mountains and Alexander Archipelago, in Cobb, the Border Ranges fault, which they infer to be E. H., ed., The United States Geological Survey in Alas "a late Mesozoic plate boundary that juxtaposes ka; accomplishments during 1975: U.S. Geol. Survey regionally metamorphosed upper Paleozoic Circ. 733, p. 14-16. Rossman, D. L., 1963, Geology of the eastern part of the rocks on the north (east) against predominantly Mount Fairweather quadrangle, Glacier Bay, Alaska: upper Mesozoic deep marine rocks" (p. 14) on U.S. Geol. Survey Bull. 1121-K, 57 p. the southwest. The questions concerning the Sietz, J. F., 1959, Geology of Geikie Inlet area, Glacier Bay, southward extension of the suture zone and of Alaska: U.S. Geol. Survey Bull. 1058-C, p. 61-120. the Fairweather province rocks into Chichagof Island cannot be answered without more field OFFSHORE ALASKA study. The available evidence and the interpretations Heat flow and organic gas measurements from the Aleutian Basin, Bering Sea given here suggest that the Tarr Inlet suture By Alan K. Cooper zone resulted from the collision, sometime be tween Permian and middle Cretaceous, of a The Aleutian Basin is one of the three deep- block of probable Precambrian or lower Paleozo water (more than 3,000 m) sedimentary basins ic rocks to the west with the large block of middle that lie north of the Aleutian Ridge. Several geo Paleozoic rocks to the east; the middle Paleozoic logic and geophysical observations made by in rocks are the essential element (Brew and others, vestigators working in the Aleutian Basin 1966) of what is now called the Alexander terrane (summarized in Cooper and others, 1978), when (Berg and others, 1972). This suggested collision considered collectively, suggest that the basin is zone is within the Alexander terrane as presently a promising area for hydrocarbon exploration. defined in this region, and its role in larger tec Observations relevant to the existence of hydro tonic models is not clear. carbon accumulations include the following: 1) the basin contains a thick section of mostly Ce- REFERENCES CITED nozoic sedimentary deposits (2 to 9 km thick) Berg, H. C., Jones, D. L., and Richter, D. H., 1972, Gravina- overlying an igneous oceanic crustal section; 2) Nutzotin belt tectonic significance of an upper Meso potentially high thermal gradients exist in the zoic sedimentary and volcanic sequence in southern and sedimentary section; 3) structural features (dia- B-92 pirs, faults, basement ridges) are present throughout the basin; 4) the sedimentary section contains potential source and reservoir beds; and 5) within the central part of the basin are abun dant VAMPs (velocity amplitude features), which may be caused by trapped gases within the sedimentary section. As part of the ongoing program for identifying and investigating promising areas for new energy resources, a combined geologic and geophysical cruise (S3-77-BS) was conducted within the Aleutian Basin aboard the U.S.G.S. research ves sel Sea Sounder during the first two weeks in June 1977. The primary objective of the cruise was to measure both the heat flow and the con centration of organic gases in surface sediment at sites in the central Aleutian Basin that had been surveyed with high-energy seismic reflection __ Geophysical trockline Gas analysis profiles during a cruise (L5-76-BS) in 1976 (Coo O Sample attempt Jjf Heat flow per, 1977). A secondary objective was to collect seismic reflection data between sample stations FIGURE 43. Bathymetric map of the Aleutian Basin, Bering Sea, showing geophysical tracklines and geologic sampling and use these data to delineate more accurately sites occupied during June 1977. Bathymetric contours in both the zone of VAMPs and the region of irreg meters. ular buried basement relief. rather than local intrusive heat sources. Thermal The cruise was highly successful, primarily conductivity of the sediment, primarily silty dia- owing to the diligent efforts of the ship's crew tomaceous ooze, ranges from 1.66 to 4.49 and scientific staff, and the excellent weather. A m . High conductivity values (greater total of 26 sample attempts (fig. 43) were made cm X s X °C with a 3-m gravity corer equipped with outrigger than 2.5 mca* are found in thin layers (5- thermal probes; 19 sediment cores, 6 heat flow cm X s X °C measurements, and 8 organic gas analyses were 20 cm thick) of fine-grained silica and heavy- obtained. Nearly 4,000 km of underway geo mineral sand; the well-sorted sand layers consti physical records (single-channel seismic reflec tute 8 to 10 percent of the sediment in the cores tion, gravity, magnetics) was collected. and appear to be the result of widespread tur Analyses of most sediment core data were bidity currents in the abyssal basin. done onboard ship by U.S.G.S. scientists. George The primary constituent of the organic gases, Redden conducted the organic gas analyses of which are totally dissolved in the interstitial wa the freshly recovered sediment using special pro ters, is methane. The concentration of methane cedures and equipment designed by Keith Kven- always increases with depth in the cores and is volden's marine organic geochemistry group. higher, at comparable sub-bottom depths, inside The thermal conductivity of the sediment was the zone of VAMPs. The largest concentration of measured by Vaughn Marshall and Jon Childs methane is found directly over a VAMP. The ori with a computer-activated needle probe built es gin of the methane is unknown and could be ei pecially for the cruise by Jim Chan, from plans ther from in situ biogenic generation of the gas or supplied by Art Lachenbruch's heat flow group. from upward migration of petrogenic gases origi Heat flow values in the central Aleutian Basin nating from deeply buried hydrocarbon deposits. range from 1.2 to 1.7 jucal/cm2/s and average 1.45 A buried basement ridge (30 km long, 10 km ±0.16 jucal/cm2/s. The values are not correlated wide, 3 km relief) was discovered during the with the buried basement relief (heat flow values cruise in the northeastern Aleutian Basin. The are not greater on top of basement ridges); thus ridge, which has been named Sounder Ridge the small variations in heat flow may be caused after the U.S.G.S. research vessel Sea Sounder, by regional subcrustal temperature variations is similar to other buried ridges in the same area B-93 in that it has had a complex constructional his tory that may range from early to late Cenozoic time. The highly successful 1977 field season has provided additional insight into the regional geo logic and geophysical framework of the Aleutian EXPLANATION Basin, especially those aspects pertaining to po Intense ice gouging

tential hydrocarbon resources in the basin. Gas cratering

REFERENCES CITED Intense current activity

Cooper, A. K., 1977, Marine geophysical investigation in the :'-\'-:VJ 'ntense storm surge activity Bering Sea Basin, in Blean, K. M., ed., The United States Geological Survey in Alaska; accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B98- B100. Cooper, A. K., Scholl, D. W., Marlow, M. S., Childs, J. R., Redden, G., and Kvenvolden, K., 1978, The Aleutian Basin, Bering Sea a frontier area for hydrocarbon ex ploration: Offshore Technology Conf. Proc., May 1978, preprint.

Environmental geologic studies in northern Bering Sea By Devin R. Thor and Hans Nelson A three-week cruise to the northern Bering Sea during July 1977 covered 2,900 km of geo physical tracklines and collected 3.5-kHz, 12- 100 KILOMETERS kHz, 200-kHz, Uniboom, minisparker, side-scan sonar, and 120-kj single channel sparker seismic FIGURE 44. Potentially hazardous regions, north data. At 48 stations, 29 box cores, 10 vibracores, ern Bering Sea. and 100 Soutar van Veen grab samples were col lected (Thor, 1978). Environmental evaluation of geologic phe found in surrounding baseline stations. As fur nomena in northern Bering Sea indicates that ther support for the seep, the occurrence of a faulting, ice gouging, bottom currents, storm deep subsurface anomaly at 100 m suggests the surges, and gas-charged sediments pose prob presence of a large subsurface gas cap greater lems with development of offshore resources than 10 km in diameter. High-resolution seismic (Nelson and Thor, 1977) (fig. 44). Surface and profiles show surface termination of subbottom near-surface faults are conspicuous, but Holo- reflectors under a region of 2 km2 in the area cene fault activity is difficult to determine be where the vibracore was obtained. These data in cause strong current scour may be preserving or dicate a potential petroleum resource with a exhuming old scarps. Surface and near-surface known area of surface escape from the large un faulting south of Nome seems to be associated derlying gas cap and a potential hazard for future with thermogenic gas seeps (Nelson and Kven drilling activity in this area. volden, 1978). Analysis of gas from 2-m vibracore Ice scouring of bottom sediment occurs sediment samples showed anomalously high con throughout northeastern Bering Sea where water centrations of hydrocarbons heavier than meth depths are less than 20 m (Thor and others, ane. The ratio of methane to ethane plus propane 1977). Ice gouge furrows reach a maximum depth reached a minimum value of 7 at the bottom of a of 0.75 m in bottom sediment and occur most 1.6-m-long core. Maximum concentrations of commonly as solitary gouges. Pressure ridge rak ethane, propane, rc-butane, and isobutane were ing, most commonly around the shoals of the Yu 76, 3, 6, and 52 times greater, respectively, than kon Delta is caused by a well-developed shear the maximum concentrations of these gases zone of offshore pack ice. Ice gouging affects B-94 most of Norton Sound to some degree but is most Small (3 to 8 m in diameter) circular craters intense in the Yukon Delta. Much of the gouging observed on sonographs over a large area of in the sound probably is caused by allochthonous north-central Norton Sound may be formed by ice from northern Bering and(or) southern gas venting during major storm wave stress on Chukchi Seas. Ice brought into the sound during the sea floor (Hans Nelson and others, unpub. springtime, by a combination of cyclonic water- data, 1977). Vibracore samples and acoustic current gyre and winds, grounds in the shallow anomalies in high-resolution seismic profiles in water of the prodelta. dicate that craters are associated with a thin Sand waves, 1 to 2 m high with wavelengths of cover of Holocene Yukon mud overlying near- 10 to 20 or 150 to 200 m, and ripples, 4 cm high surface freshwater peaty muds and gas-rich sedi with 20-cm wavelength, occupy the crests and ment. Abnormally high amounts of methane gas some flanks of a series of large, linear ridges lying generated by the buried organic debris cause gas west of the Port Clarence area (Field and others, charging of the near-surface sediments. Gas 1977; Nelson and others, 1977; Cacchione and venting and cratering, particularly during peak others, 1977). Ice gouges in varying states of storm periods, have been associated with pipe preservation on several ridges indicate active line breaks in the oil-producing regions of the sand wave modification and recent movement. North Sea and the Gulf of Mexico. Survey tracklines of 1976 were replicated in In conclusion, present knowledge suggests that 1977, and local changes in bedform type and the Yukon Delta and eastern Bering Strait areas trend further substantiate recent bedform activ have severe geologic hazards (fig. 44). Faulting ity. Sand wave movement and bedload transport and current scour are most intense in Bering seem to occur during calm weather; maximum Strait. Ice gouge, bottom current, and storm change may take place when northerly current surge activity are intense for a wide area around flow is enhanced by sea level set-up from major the shallow prodelta area. Apparent gas crater- southwesterly storms. Strong north winds from ing occurs throughout central and eastern Nor the Arctic, however, reduce the strength of the ton Sound. continuous northerly currents and thereby de crease the amount of bedload transport and ac tivity of mobile bedforms near Bering Strait. Evidence from the most recent storm-surge REFERENCES CITED event, in 1974, suggests that severe storms also Cacchione, D. A., Drake, D. E., and Nelson, Hans, 1977, cause major scour and movement of sand sheets Sediment transport in Norton Sound, Alaska [abs.]: over wide areas of southern Norton Sound. Am. Geophys. Union, OES, Trans., v. 58, no. 6, p. 408. A series of large (25 to 150 m in diameter), ir Field, M. E., Nelson, Hans, Cacchione, D. A., and Drake, D. E., 1977, Dynamics of bed forms at an epicontinental regularly shaped, shallow (less than 1 m) depres shelf; northern Bering Sea [abs.]: Am. Geophys. Union, sions in Yukon-derived silty to sandy mud occurs EOS, Trans., v. 58, no. 12, p. 1162. along the southwestern margin of the Yukon Nelson, Hans, Cacchione, D. A., and Field, M. E., 1977, Com Delta and on the flanks of an extensive shallow plex ridge and trough topography on a shallow current- trough in north-central Norton Sound. They dominated shelf, northwest Alaska [abs.]: Am. Assoc. Petroleum Geologists Bull., v. 61, p. 817. usually are associated with increased bottom Nelson, Hans, and Kvenvolden, K. E., 1978, Thermogenic steepness and regions of higher bottom current gas in sediments of Norton Sound, Alaska [abs.]: Off speeds. Some of the northern depressions are shore Technology Conf., May 1978, preprint (in press). found near sea-floor scarps of unknown origin; Nelson, Hans, and Thor, D. R., 1977, Environmental geo those to the southwest on the prodelta front are logic hazards in Norton Basin, Bering Sea [abs.]: Geol. Soc. America, Abs. with Programs, v. 9, p. 1111. clearly associated with ice-gouge furrows. Appar Thor, D. R., 1978, Continuous seismic reflection data, Sea 5- ently, in regions where current speed is increased 77-BS Cruise, northern Bering Sea: U.S. Geol. Survey because of constriction of water flow along flanks Open-File-Report. of troughs, shoals, or delta fronts, any further Thor, D. R., Nelson, Hans, and Evans, J. E., 1977, Prelimi disruption of current flow by slump scarps or ice- nary assessment of ice gouging in Norton Sound, Alaska, in Environmental assessment of the Alaskan gouge furrows initiates scour of the Yukon River- continental shelf: Environmental Research Labs., Natl. derived sediments, forming large shallow depres Oceanog. and Atmospheric Agency, Dept. Commerce, sions. Ann. Tech. Summary Rept., p. E-l-E-18. (in press). B-95 Navarin basin, northwest Bering Sea shelf ber of earthquakes were located offshore. In par By Mike Marlow ticular, only two of the better located earth During the summer of 1977 approximately quakes had epicenters within 20 km of the Pam- 3,000 km of geophysical data, including 24-chan- plona Ridge, the site of a series of three magni- nel seismic reflection profiles, was collected by tude-6 earthquakes in 1970 (Page, 1975). the R/V S.P. Lee from the northwest Bering Sea Although the number of earthquakes detected shelf (fig. 2, area 10). These data revealed that and located offshore may be influenced by sta Navarin basin (Marlow and others, 1976) is actu tion distribution, I believe that the observed pat ally a complex of three distinct subshelf basins, tern in seismicity represents a real contrast in encompassing an area of 44,000 km2. These ba the present level of earthquake activity between sins are each filled with more than 9 km of sedi onshore and offshore areas. mentary section and are separated from one Northeast of Icy Bay and Kayak Island, the another by northwest-trending basement ridges. epicenters of the better located earthquakes de Along the northern perimeter of the complex, the fine two zones of seismicity that have northeast basin fill has been strongly folded and truncated. trends and cut across the east-west trends of Regional studies in nearby Siberia suggest that mapped thrust faults and other structural fea deformation took place in late Miocene(?) and tures. Earthquakes that occurred beneath Icy Pliocene (?) time. In contrast, the central and Bay, at the southwest end of one of these zones, southern areas of the complex appear to have were relocated using a master event technique. formed by crustal extension and down-dropping The epicenters of the relocated earthquakes of basement rocks to form grabenlike basins now have an east-west trend parallel to nearby filled by nearly flat-lying Cenozoic sedimentary mapped faults (Bruns and Plafker, 1975) (fig. rocks. 45); this trend suggests that in the larger, north Along several geophysical lines numerous east-trending zone of seismicity, the earthquakes acoustical anomalies ("bright spots") were de are occurring on several east-west-trending tected that may be related to hydrocarbon de faults. posits (gas?) whose size, extent, and commercial value are unknown. 60.25

REFERENCE CITED

Marlow, M. 8., Scholl, D. W., Cooper, A. K., and Buffington, E. C., 1976, Structure and evolution of Bering Sea shelf south of St. Lawrence Island: Am. Assoc. Petroleum Ge ologists Bull., v. 60, p. 161-183.

Seismicity near Icy Bay, Alaska and in the eastern Gulf of Alaska By Christopher Stephens

The seismicity in the eastern Gulf of Alaska region, on the basis of results of monitoring by the U.S.G.S. seismic network from 1974 to 1976, is characterized by a scattered distribution of 59.75 earthquake epicenters. Local concentrations of FIGURE 45. Epicenters and first-motion plots of the better epicenters do occur, however, such as in the on located earthquakes that occurred beneath Icy Bay, Alas shore area northeast of Kayak Island, northeast ka, between September 1974 and September 1976. The of Icy Bay, and about 50 km south of Yakutat master event used to relocate the earthquakes is shown as Bay. Of the 492 earthquakes located during this a cross. The four closest seismic stations are shown as time period, those with the best control in the so open, inverted triangles. The heavy dashed and solid lines show mapped and inferred thrust faults, respectively. The lution have depths ranging from a few kilometers light dashed lines join earthquakes used in the same com to about 35 km. The largest earthquakes had posite first-motion plot. Note the reversal of focal mecha magnitudes of about 4. A relatively small num nism with increasing depth to the west. B-96 Composite and single-event first-motion plots from Chichagof Island (fig. 46). The samples for several of the relocated earthquakes that oc were to provide geologic control on the seaward curred beneath Icy Bay suggest that there is a re margin of the Gulf of Alaska Tertiary Province, a versal of focal mechanism at depth in this area. major sedimentary basin that has been of inter Earthquakes located at depths less than about 10 est for petroleum exploration for many years km have focal mechanisms consistent with (Plafker, 1971; Plafker and others, 1975). As of thrusting on a plane dipping steeply to the north, January 1978, part of this basin on the Outer which in turn is consistent with the characteris Continental Shelf between Kayak Island and Icy tic large-scale uplift along the eastern Gulf of Bay was under lease for petroleum exploration, Alaska. Earthquakes deeper than about 10 km and eight dry wildcat wells had been drilled for have focal mechanisms indicating relative mo petroleum. Outcrop control along the Continen tion nearly opposite to that of the shallower tal Slope is essential for delineating the offshore earthquakes. The interpretation of the focal distribution of the potentially petroliferous Ter mechanisms for the deeper earthquakes is not tiary sequence, for understanding facies changes clear. Although the nodal planes as drawn are that occur between outcrop sections and wells consistent with normal faulting on a plane dip onshore and the seaward margin of the basin, ping steeply to the north, a change of about 10° and for correlation of the Tertiary sequence with in the dip of the nodal planes for the single event seismic reflecting horizons that at many loca solution would result in a mechanism consistent tions appear to intersect the Continental Slope. with thrusting on a plane with a very shallow dip Despite persistent mechanical difficulties with to the north. Marine refraction profiles from im the main winch, 16 dredge hauls that are be mediately south of Icy Bay (Bayer and others, lieved to have sampled bedrock outcrops or talus 1977) indicate the presence of a shallow layer, were made in water depths ranging from 3,500 m possibly oceanic crust, dipping gently to the to 220 m. Locations for these dredge hauls, which north toward Icy Bay. If this layer extends be are the first known outcrop samples from the neath Icy Bay, and if the deeper earthquakes are Continental Slope in the Gulf of Alaska, are occurring within this layer, then the radical shown in figure 46, and selected preliminary change in focal mechanism over such a short sample date are summarized in table 5. All but depth range might be explained. seven of these hauls included variable amounts of loose glacial erratics of diverse lithology that REFERENCES CITED most likely were rafted into the Pacific Ocean by ice floes, but in part may have been deposited Bayer, K. C., Mattick, R. E., Plafker, George, and Bruns, T. during former glacial advances close to the edge R., 1977, Refraction studies between Icy Bay and Kayak Island, eastern Gulf of Alaska: U.S. Geol. Survey Open- of the Continental Shelf. In addition, three hauls File Report 77-550, 29 p. were made that contained only glacial erratics, Bruns, T. R., and Plafker, George, 1975, Preliminary struc two casts were made in which the dredge buckets tural map of part of the Offshore Gulf of Alaska Tertiary hung up and were lost, four casts did not recover Province: U.S. Geol. Survey Open-File Report 75-508, 1 any sample, and 10 dart cores were attempted, sheet, scale 1:500,000. Page, R. A., 1975, Evaluation of seismicity and earthquake none of which penetrated the surficial mud into shaking at offshore site: Offshore Technology Conf., 7th, indurated sediments. Houston, Texas, Proc., v. 3, p. 179-190. Preliminary analyses of the lithology, physical properties, and paleontology suggest significant Outcrop samples from the Continental Slope in the differences in the geology along the Continental eastern Gulf of Alaska Slope, as follows. By George Plafker, Gary R. Winkler, Susan J. Hunt, Susan Bartsch-Winkler, Warren L. Coonrad, and Paula Quinterno Southeast of Cross Sound (1) Sample 1 indicates that the upper part of Between June 5 and June 15, 1977, the R/V the bedded sequence forming a narrow shelf ba Sea Sounder carried out a program of sampling sin seaward of Chichagof Island includes marine bedrock outcrops along the Continental Slope in glacial deposits equivalent in lithology and age to the eastern Gulf of Alaska between the eastern the uppermost part of the Yakataga Formation end of the Aleutian Trench and the area offshore northwest of Cross Sound. B-97 - 58°

146° 144' 136°

FIGURE 46. Map showing locations of outcrop dredge samples from the eastern Gulf of Alaska. Numerals indicate samples described in table 6 and the text.

Between Cross Sound and Alsek Canyon Wageman (1973) and Taylor and O'Neill (1974) (1) Samples 3 and 6 indicate that much of the could be related to a major pluton of dioritic Continental Slope off the Fairweather Ground composition. consists of pre-Tertiary outcrops of hard feldspatholithic sandstone, pebbly sandstone, argil- From Alsek Canyon to Yakutat Seavalley lite, and greenstone typical of the lithologies of (1) In this segment of the Outer Continental the Yakutat Group on the adjacent mainland. Shelf, the Tertiary sequence thickens markedly (2) Sample 4 is lithologically similar to altered and includes clastic sedimentary rocks ranging in diorite that, on the mainland, commonly in age from late Eocene and possibly older through trudes the Yakutat Group. However, not enough late Oligocene. This older Tertiary sequence, sample was recovered to be certain that it is from roughly 3,000 m thick, lies above probable Creta bedrock. ceous basement, which has been found in sam (3) Samples 2 and 5 indicate that sedimentary ples 8 and 9. rocks of late Tertiary or younger age and litho- (2) The deepest Tertiary(?) sample, number logy similar to the Yakataga Formation occur in 20, is an indurated sandy cobble-boulder con isolated basins on the pre-Tertiary and crystal glomerate from an outcrop located close to the line basement rocks in the vicinity of the Fair- base of the Continental Slope in water 3,180 m- weather Ground. 3,080 m deep. It is not similar in lithology to any (4) The presence of basement rocks, including known conglomeratic strata that crop out on diorite, suggests the possibility that a broad posi shore, but the degree of induration suggests that tive magnetic anomaly centered over the Fair- it could be equivalent to one of the Paleocene or weather Ground described by Naugler and Eocene formations. B-98 (3) Samples 10,11,17,18, and 22 were recov Eastern end of Aleutian Trench south of Kayak ered upslope from the conglomerate and prob Island able Cretaceous outcrops. They consist entirely (1) Sample 36 is from the upper part of a of siltstone, containing a late Eocene to late Oli- prominent topographic ridge that rises 1,000 m gocene microfauna, that is interbedded with above the base of the Continental Slope and is sandstone. These rocks are probably correlative separated from the upper Continental Slope by a with the onshore Tokun and Poul Creek Forma sediment-filled terrace basin. Single- and multi tions. channel seismic profile data indicate that this (4) Microscopic examination of the sand ridge is part of a major east-west-trending struc stones suggests that they range from poorly to tural high that extends for at least 60 km along moderately well sorted, contain abundant unsta the base of the slope (T. R. Bruns, oral commun., ble rock fragments, have pervasive siliceous or 1978). The sample consists of blocks of dense and calcareous cement, and have poor to moderate indurated sandy and pebbly siltstone of early porosity which probably is secondary. Pleistocene age. The siltstone is a deep-water (5) Preliminary evaluation of the argillaceous correlative of the uppermost part of the shallow components in samples 10,11,17,18, 20 and 22 water Yakataga Formation exposed on Middle- indicates that all but sample 10 have above aver ton Island at the edge of the continental shelf. age (>0.4 percent) carbon contents with ranges (2) The unusually high density of the sample, from 0.56 to 1.56 percent carbon. Thermal analy its occurrence on a topographic and structural sis, however, suggests that the samples have un high, and the inability to achieve acoustic pene dergone only moderate thermal histories and tration into the structure with the 160-kj sparker that organic matter present is predominantly of all suggest that sample 36 may have been com a chemical type that does not yield liquid hydro pacted by tectonic deformation related to crustal carbons (G. E. Clay pool, written commun., plate convergence along the inner wall of the 1977). Aleutian Trench. (6) The highly magnetic greenstone in sample (3) The prominent topographic high from 9 is from an area where aeromagnetic data indi which sample 36 was collected is probably largely cate a strong positive linear magnetic anomaly of Quaternary age and hence is unlikely to have trending west-northwest toward Kayak Island any petroleum potential. (Naugler and Wageman, 1973; Taylor and O'Neill, 1974). This anomaly may be caused by a REFERENCES CITED fairly continuous band of spilitized basalt similar Naugler, F. P., and Wageman, J. M., 1973, Gulf of Alaska; to that in sample 9. magnetic anomalies, fracture zones, and plate interac (7) A multichannel seismic reflection profile tion: Geol. Soc. America Bull., v. 84, p. 1575-1584. by T. R. Bruns (oral commun., 1978) indicates Plafker, George, 1971, Pacific margin Tertiary basin, in Fu ture petroleum provinces of North America: Am. Assoc. that the shelf edge is a structural high underlain Petroleum Geologists Mem. 15, p. 120-135. by Eocene and Oligocene strata that form a Plafker, George, Bruns, T. R., and Page, R. A., 1975, Interim wedge dipping and thinning toward the coast. report on petroleum resource potential and geologic Landward of this high is a broad basin filled with hazards in the Outer Continental Shelf of the Gulf of a younger sequence at least 6,000 m thick, pre Alaska Tertiary Province: U.S. Geol. Survey Open-File Report 75-592, 74 p. sumably consisting mainly of late Cenozoic Yak- Taylor, P. T., and O'Neill, N. J., 1974, Results of an aero- ataga Formation. The upper part of this younger magnetic survey in the Gulf of Alaska: Jour. Geophys. sequence overlaps the shelf edge high. Research, v. 9, no. 5, p. 719-723.

B-99 TABLE 5. Summary of data for outcrop samples recovered in dredge hauls, eastern Gulf of Alaska

[Ages for samples containing microfossils are based on studies of the foraminifers by W. W. Rau, silico- flagellates by R. G. Poore, and nannoplankton by David Bukry. All other ages are inferred by lithologic comparison with rocks onshore]

Inferred correlative Sample Water Lithology Fossil Age No. depth (m) content onshore unit

1000-222 Soft to moderately hard Foraminifers, Late Quaternary Uppermost part of gray siltstone with diatoms, Yakataga Formation sparse floating pebbles mollusks to 5 cm diameter, sand grains, and mollusk fragments 2090-1500 Slightly indurated dark- Foraminifers, Early Pliocene Middle part of gray sandy siltstone nannoplankton, or younger Yakataga Formation with floating pebbles diatoms and hard light-gray hemipelagic siltstone with minor glauconite 1250-750 Blocky very hard dense None Jurassic(?) and Yakutat(?) Group gray feldspatholithic Cretaceous (?) sandstone, pebbly sand stone, and black argillite 600-520 Three cobble-size pieces None Cretaceous or Plutons intrusive of epidote- and garnet- Tertiary into Yakutat Group bearing diorite; could be talus or glacial erratics 380-220 Blocky weathered brown Mollusks Late Tertiary Yakataga Formation fossiliferous sandstone and greenish-gray dirty sandstone 157-150 Blocky hard gray to None Jurassic (?) and Yakutat(?) Group greenish-gray sheared Cretaceous (?) feldspatholithic sand stone and dense dark- green, very fine-grained greenstone 2750-2250 One angular chunk of hard None Jurassic (?) and Yakutat(?) Group dark-green calcite- Cretaceous (?) veined, very fine grained spilitized tholeiitic basalt 2125-1700 Two pieces of dark-green None Jurassic (?) Yakutat(?) Group and sheared highly magnetic Cretaceous (?) Yakataga(?) Formation and very vesicular and Tertiary (?) spilitized tholeiitic basalt and weathered brown pebbly feldspatho lithic sandstone 10 1875-1400 Soft gray to greenish- Foraminifers, Late Eocene and Tokun and(or) Poul gray pyritic waxy silt- diatoms Oligocene Creek Formations stone, dark-gray slabby moderately indurated siltstone, and blocky brown-weathering gray friable medium-grained feldspatholithic sand stone with pervasive siliceous cement but moderate secondary porosity

B-100 TABLE 5. Summary of data for outcrop samples recovered in dredge hauls, eastern Gulf of Alaska Continued

Sample Water Lithology Fossil Age Inferred correlative No. depth (m) content onshore unit

11 890-500 Moderately well indurated Foraminifers, Late Eocene Tokun Formation slabby dark-gray silt- coccoliths stone and foraminiferal sandy siltstone with hard brown-weathering gray medium-grained feldspatholithic sand stone with calcareous cement 17 1025-925 Black laminated shale Diatoms, sili- Late Oligocene Upper part of Poul with partings of fine- coglagellates, Creek Formation grained highly mica- foraminifers ceous sandstone and soft medium-gray siltstone. Subordinate gray friable medium- grained feldspatholithic sandstone with pervasive siliceous cement and moderate secondary poros ity 18 510-250 Gray siltstone with abun- Diatoms, sili- Late Oligocene Upper part of Poul dant microfauna and coflagellates Creek Formation sparse glauconite and pyritic micronodules. Cut by closely spaced, slickensided fractures 19 2230-1350 Sticky olive-green chlo- None Jurassic (?) and Yakutat(?) Group ritic mud on dredge jaws Cretaceous (?) that is probably scraped from weathered greenstone 20 3100-1350 Fresh hard blocky pebble- None Paleogene(?) Orca(?) Group or cobble-boulder conglomer Tokun(?) Formation ate with medium-grained feldspatholithic sand stone matrix 22 2575-2300 Weathered dark-gray Foraminifers Early Tertiary Tokun(?) rormation slabby micaceous foraminiferal siltstone and fine- to medium- grained, very dirty sandstone with minor secondary porosity 36 3500-26.50 Two chunks of dense. Diatoms, sponge Early Upper part of olive-gray siliceous spicules, Pleistocene Yakataga Formation siltstone with rare reworked floating sand grains coccoliths and pebbles as large as 1 cm

B-101 REPORTS ON ALASKA Bartsch-Winkler, Susan, 1977a, Geologic mapping in Alaska; U.S. Geological Survey, post-1930, scales PUBLISHED BY THE 1:96,000 to 1:250,000: U.S. Geol. Survey Open-file U.S. GEOLOGICAL SURVEY IN 1977 Rept. 77-681, 1 sheet. ___1977b, Geologic mapping in Alaska; U.S. Albert, N. R. D., and Steele, W. C., 1976, Geological Survey, post-1930, scales 1:20,000 to Interpretation of Landsat imagery of the Tanacross 1:63,360: U.S. Geol. Survey Open-file Rept. quadrangle, Alaska: U.S. Geol. Survey Misc. Field 77-682, 1 sheet. Studies Map MF-767-C, 3 sheets, scale 1:250,000. Bayer, K. C., Mattick, R. E., Plafker, George, and ___1977, Landsat data interpretation, McCarthy, Bruns, T. R., 1977, Refraction studies between Icy Tanacross, and Talkeetna quadrangles, in Blean, K. Bay and Kayak Island, eastern Gulf of Alaska: U.S. M., ed., The United States Geological Survey in Geol. Survey Open-file Rept. 77-550, 29 p. Alaska Accomplishments during 1976: U.S. Geol. Beikman, H. M., 1977, Preliminary geologic map of Survey Circ. 751-B, p. B58-B61. Alaska, in_ Blean, K. M., ed., The United States Anderson, G. S., 1977, Artificial recharge experiments Geological Survey in Alaska Accomplishments on the Ship Creek alluvial fan, Anchorage, Alaska: during 1976: U.S. Geol. Survey Circ. 751-B, p. B1, Natl. Tech. Inf. Service PB-270 623/AS, 50 p. EH. Armstrong, A. K., Harris, A. G., Reed, Bruce, and Beikman, H. M., Holloway, C. D., and MacKevett, E. M., Carter, Claire, 1977, Paleozoic sedimentary rocks Jr., 1977, Generalized geologic map of the eastern in the northwestern part of Talkeetna quadrangle, part of southern Alaska; U.S. Geol. Survey Alaska Range, Alaska, in Blean, K. M., ed., The Open-file Rept. 77-169-B, 1 sheet, scale United States Geological Survey in Alaska 1:1,000,000. Accomplishments during 1976: U.S. Geol. Survey Berg, H. C., Elliott, R. L., Smith, J. G., Pittman, T. Circ. 751-B, p. B61-B62. L., and Kimball, A. L., 1977, Mineral resources of Armstrong, A. K., and MacKevett, E. M., Jr., 1977a, the Granite Fiords wilderness study area, Alaska, Carbonate sedimentation, sabkha facies, with a section on aeromagnetic data by Andrew diagenesis, and stratigraphy, lower part of the Griscom: U.S. Geol. Survey Bull. 1403, 151 p. Chitistone Limestone - the Triassic host rock for Berg, H. C., Smith, J. G., Elliott, R. L., and Koch, Kennecott-type copper deposits, in Blean, K. M., R. D., 1977, Structural elements of Insular Belt ed., The United States Geological Survey in and Coast Range plutonic complex near Ketchikan, Alaska Accomplishments during 1976: U.S. Geol. Alaska; a progress report, in Blean, K. M., ed., Survey Circ. 751-B, p. B56. The United States Geological Survey in ___1977b, The Triassic Chitistone Limestone, Alaska Accomplishments during 1976: U.S. Geol. Wrangell Mountains, Alaska stressing detailed Survey Circ. 751-B, p. B76-B78. descriptions of sabkha facies and other rocks in Biddle, K. T., 1977, Preliminary study of heavy lower parts of the Chitistone and their relations minerals from the Beluga and Sterling Formations to Kennecott-type copper deposits: U.S. Geol. exposed near Homer, Kenai Peninsula, Alaska: U.S. Survey Open-file Rept. 77-217, 63 p. Geol. Survey Open-file Rept. 77-874, 12 p. Armstrong, A. K., and Mamet, B. L., 1977a, Bird, K. J., 1977, Late Paleozoic carbonates from the Carboniferous microfacies, microfossils, and south-central Brooks Range, i^ Blean, K. M., ed., corals, Lisburne Group, arctic Alaska, in Blean, The United States Geological Survey in K. M., ed., The United States Geological Survey in Alaska Accomplishments during 1976: U.S. Geol. Alaska Accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B19-B20. Survey Circ. 751-B, p. B18-. Blackford, Michael, 1977, Seismicity patterns in the ___1977b, Mississippian microfacies of the Lisburne Cook Inlet-Prince William Sound region, Alaska, in Group, Endicott Mountains, arctic Alaska, in Blean, K. M., ed., The United States Geological Blean, K. M., ed., The United States Geological Survey in Alaska Accomplishments during 1976: Survey in Alaska Accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B94-B96. U.S. Geol. Survey Circ. 751-B, p. B18-B19. Blean, K. M., ed., 1977a, The United States Geological Barnes, D. F., 1977a, Bouguer gravity map of Alaska: Survey in Alaska; organization and status of U.S. Geol. Survey Geophys. Inv. Map GP-913, 1 programs in 1977: U.S. Geol. Survey Circ. 751-A, sheet, scale 1:2,500,000. p. A1-A66. ___1977b, Preliminary Bouguer gravity map of central ___1977b, The United States Geological Survey in Alaska: U.S. Geol. Survey Open-file Rept. Alaska Accomplishments during 1976: U.S. Geol. 77-168-C, 1 sheet, scale 1:1,000,000. Survey Circ. 751-B, p. B1-B112. _1977c, Gravity map of the eastern part of Boucher, Gary, 1977, Gravity measurements on summer southern Alaska: U.S. Geol. Survey Open-file Rept. sea ice in the Beaufort and Chukchi Seas, 1976: 77-169-C, 1 sheet, scale 1:1,000,000. U.S. Geol. Survey Open-file Rept. 77-705, 7 p. Barnes, D. F., and Watts, R. D., 1977, Geophysical Boucher, Gary, Ruppel, B. D., Chiburis, E. F., and surveys in Glacier Bay National Monument, in Dehlinger, Peter, 1977, Map showing free-air Blean, K. M., ed., The United States Geological gravity anomalies in the southern Beaufort Sea: Survey in Alaska Accomplishments during 1976: U.S. Geol. Survey Misc. Field Studies Map MF-851, U.S. Geol. Survey Circ. 751-B, p. B93-B95. 1 sheet, scale approx. 1:1,000,000. Barnes, Peter, Reimnitz, Erk, Drake, D. E., and Brabb, E. E., and Hamachi, B. R., 1977, Chemical Toimil, L. J., 1977, Miscellaneous hydrologic and composition of Precambrian, Paleozoic, Mesozoic, geologic observations on the inner Beaufort Sea and Tertiary rocks from east-central Alaska: U.S. shelf, Alaska: U.S. Geol. Survey Open-file Rept. Geol. Survey Open-file Rept. 77-631, 166 p. 77-477, 95 p. Brew, D. A., and Ford, A. B., 1977a, Coast Range Barnes, Peter, Reimnitz, Erk, Smith, Greg, and megalineament and Clarence Strait lineament on Melchior, John, 1977, Bathymetric and shoreline west edge of Coast Range batholithic complex, changes, northwestern Prudhoe Bay, Alaska: U.S. southeastern Alaska, in Blean, K. M., ed., The Geol. Survey Open-file Rept. 77-161, 15 p. United States Geological Survey in Alaska Accomplishments during 1976: U.S. Geol.

B-102 Survey Circ. 751-B, p. B?9. Survey Open-file Rept. 77-735, 36 p. _1977b, Preliminary geologic and Carlson, P. R., Molnia, B. F., Bruns, T. R., and metamorphic-isograd map of the Juneau B-1 Whitney, J. W., 1977, Shelf-edge scarps in the quadrangle, Alaska; U.S. Geol. Survey Misc. Field northern Gulf of Alaska, in_ Blean, K. M., ed., The Studies Map MF-846, 1 sheet, scale 1:31,680. United States Geological Survey in Brew, D. A., Grybeck, Donald, Johnson, B. R., Jachens, Alaska Accomplishments during 1976: U.S. Geol. R. C., Nutt, C. J., Barnes, D. F., Kimball, A. L., Survey Circ. 751-B, p. B96-B97. Still, J. C., and Rataj, J. L., 1977, Mineral Carlson, P. R., Molnia, B. F., Kittleson, S. C., and resources of the Tracy Arm-Fords Terror wilderness Hampson, J. C., Jr., 1977, Map of distribution of study area and vicinity, Alaska: U.S. Geol. Survey bottom sediments on the continental shelf, Open-file Rept. 77-649, 282 p. northern Gulf of Alaska: U.S. Geol. Survey Misc. Brew, D. A., Johnson, B. R., Nutt, C. J., Grybeck, Field Studies Map MF-876, 2 sheets, various Donald, and Ford, A. B., 1977, Newly discovered scales. granitic and gabbroic bodies in the Fairweather Carter, L. D., Repenning, C. A., Marincovich, L. N., Range, Glacier Bay National Monument, Alaska, in Hazel, J. E., Hopkins, D. M., McDougall, Kristin, Blean, K. M., ed., The United States Geological and Naeser, C. W., 1977, Gubik and pre-Gubik Survey in Alaska Accomplishments during 1976: Cenozoic deposits along the Colville River near U.S. Geol. Survey Circ. 751-B, p. B90-B91. Ocean Point, North Slope, Alaska, i£ Blean, K. M., Brew, D. A., Loney, R. A., Kistler, R. W., Czamanske, ed., The United States Geological Survey in G. K., Gromme, C. S., and Tatsumoto, Mitsunobu, Alaska Accomplishments during 1976: U.S. Geol. 1977, Probable Precambrian or lower Paleozoic Survey Circ. 751-B, p. B12-B14. rocks in the Fairweather Range, Glacier Bay Carter, R. D., Mull, C. G., and Bird, K. J., 1977, Any National Monument, Alaska, in Blean, K. M., ed., Prudhoe Bays in Naval Petroleum Reserve No. 4?, in The United States Geological Survey in Blean, K. M., ed., The United States Geological Alaska Accomplishments during 1976: U.S. Geol. Survey in Alaska Accomplishments during 1976: Survey Circ. 751-B, p. B91-B93. U.S. Geol. Survey Circ. 751-B, p. B14-B15. Brooks, R. A., and Finch, W. I., 1977, Carborne Carter, R. D., Mull, C. G., Bird, K. J., and Powers, radiometric survey of the Nome area, Seward R. B., 1977, The petroleum geology and hydrocarbon Peninsula, Alaska: U.S. Geol. Survey Open-file potential of Naval Petroleum Reserve No. 4, North Rept. 77-472, 22 p. Slope, Alaska: U.S. Geol. Survey Open-file Rept. Brosg£, W. P., and Armstrong, A. K., 1977, Lithologic 77-475, 61 p. logs of Lisburne Group in Lawrence Livermore Cathrall, J. B., Cooley, E. F., Detra, D. E., and Laboratory Drill Holes 1 and 2, Confusion Creek, Billings, T. M., 1977, A listing and statistical Chandler Lake quadrangle, northern Alaska: U.S. summary of spectrographic analyses of heavy Geol. Survey Open-file Rept. 77-26, 12 p. mineral concentrate samples for the Philip Smith Brosge, W. P., and Pessel, G. H., 1977, Preliminary Mountains quadrangle, Alaska: U.S. Geol. Survey reconnaissance geologic map of Survey Pass Open-file Rept. 77-426, 70 p. quadrangle, Alaska: U.S. Geol. Survey Open-file Cathrall, J. B., Cooley, E. F., Detra, D. E., and Rept. 77-27, 1 sheet, scale 1:250,000. O'Leary, R. M., 1977, A listing and statistical Brosg*, W. P., and Reiser, H. N., 1977a, Lead-zinc summary of spectrographic and chemical analyses of mineralization at Bear Mountain, southeastern stream-sediments and rock samples from the Philip Brooks Range, 111 Blean, K. M., ed., The United Smith Mountains quadrangle, Alaska: U.S. Geol. States Geological Survey in Survey Open-file Rept. 77-244, 79 p. Alaska Accomplishments during 1976: U.S. Geol. Chapman, R. M., 1977, GeochemLcal anomalies in Survey Circ. 751-B, p. B8-B10. bedrock, west half of Kantishna River quadrangle, ___1977b, Chemical analyses of stream-sediment ill Blean, K. M., ed., The United States Geological samples from the Table Mountain and Arctic Survey in Alaska Accomplishments during 1976: quadrangles, northern Alaska: U.S. Geol. Survey U.S. Geol. Survey Circ. 751-B, p. B35-B36. Open-file Rept. 77-29, 5 sheets. Childers, J. M., Sloan, C. E., Meckel, J. P., and Brosge, W. P., Reiser, H. N., Dutro, J. T., Jr., and Nauman, J. W., 1977, Hydrologic reconnaissance of Detterman, R. L., 1977, Generalized geologic map the eastern North Slope, Alaska, 1975: U.S. Geol. of the Philip Smith Mountains quadrangle, Alaska: Survey Open-file Rept. 77-492, 65 p. U.S. Geol. Survey Open-file Rept. 77-430, 1 sheet, Churkin, Michael, Jr., Carter, Claire, and Johnson, B. scale 1:200,000. R., 1977, A new Ordovician time scale based on Brosge, W. P., Reiser, H. N., and Moore, T. E., 1977, accumulation rates of graptolite shale, in Blean, Chemical analyses of 97 stream-sediment samples K. M., ed., The United States Geological Survey in from the Coleen and Christian quadrangles, Alaska; accomplishemnts during 1976: U.S. Geol. northern Alaska: U.S. Geol. Survey Open-file Rept. Survey Circ. 751-B, p. B4-B6. 77-458, 4 p. Churkin, Michael, Jr., and Eberlein, G. D., 1977, Bruns, T. R., and Bayer, Kenneth, 1977, Multichannel Correlation of the rocks of southeastern Alaska seismic reflection data acquired on the M/V Cecil with other parts of the Cordillera, in Blean, K. H. Green in the Gulf of Alaska, June-August 1975: M., ed., The United States Geological Survey in U.S. Geol. Survey Open-file Rept. 77-352, 22 p. Alaska Accomplishments during 1976: U.S. Geol. Bruns, T. R., and von Huene, Roland, 1977, Sedimentary Survey Circ. 751-B, p. B69-B72. basins on the Shumagin shelf, western Gulf of Churkin, Michael, Jr., Reed, B. L., Carter, Claire, Alaska, in_ Blean, K. M., ed., The United States and Winkler, G. R., 1977, Lower Paleozoic Geological Survey in Alaska Accomplishments graptolitic section in the Terra Cotta Mountains, during 1976: U.S. Geol. Survey Circ. 751-B, p. southern Alaska Range, in Blean, K. M., ed., The B97. United States Geological Survey in Bunker, C. M., Hedge, C. E., and Sainsbury, C. L., Alaska Accomplishments during 1976: U.S. Geol. 1977, Radioelement concentrations and preliminary Survey Circ. 751-B, p. B37-B38. radiometric ages of rocks of the Kigluaik Cobb, E. H., 1977a, Mineral resources of Alaska, in Mountains, Seward Peninsula, Alaska: U.S. Geol. Blean, K. M., ed., The United States Geological

B-103 Survey in Alaska Accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B10-B12. U.S. Geol. Survey Circ. 751-B, p. B1. Dickinson, K. A., 1977, Uranium and thorium __1977b, Placer deposits map of central Alaska: distribution in continental Tertiary rocks of the U.S. Geol. Survey Open-file Rept. 77-168-B, 64 p. Cook Inlet basin and some adjacent areas, Alaska, and 1 map, scale 1:1,000,000. in Campbell, J. A., ed., Short papers of the U.S. __1977c, Selected Geological Survey, U.S. Bureau of Geological Survey uranium-thorium symposium, 1977: Mines, and Alaska Division of Geological and U.S. Geol. Survey Circ. 753, p. 70-72. Geophysical Surveys reports and maps on Alaska Doyle, P. F., 1977, Streamflow and channel erosion released during 1976, indexed by quadrangle: U.S. along the TAPS route, in Blean, K. M., ed., The Geol. Survey Open-file Rept. 77-177, 115 p. United States Geological Survey in _1977d, Summary of references to mineral Alaska Accomplishments during 1976: U.S. Geol. occurrences (other than mineral fuels and Survey Circ. 751-B, p. B7. construction materials) in the Tanana quadrangle, Doyle, P. F., and Childers, J. M., 1977, Channel Alaska: U.S. Geol. Survey Open-file Rept. 77-432, erosion surveys along TAPS route, Alaska, 1976: 110 p. U.S. Geol. Survey Open-file Rept. 77-170, 93 p. 1977e, Summary of references to mineral Dutro, J. T., Jr., Brosgd, W. P., and Reiser, H. N., occurrences (other than mineral fuels and 1977, Upper Devonian depositional history, central construction materials) in the Eagle quadrangle, Brooks Range, Alaska, in Blean, K. M., ed., The Alaska: U.S. Geol. Survey Open-file Rept. 77-845, United States Geological Survey in 122 p. Alaska Accomplishments during 1976: U.S. Geol. Cobb, E. H., Dusel-Bacon, Cynthia, MacKevett, E. M., Survey Circ. 751-B, p. B16-B18. Jr., and Berg, H. C., 1977, Map showing Eberlein, G. D., Gassaway, J. S., and Beikman, H. M., distribution of mineral deposits (other than 1977, Preliminary geologic map of central Alaska: organic fuels and construction materials) in U.S. Geol. Survey Open-file Rept. 77-168-A, 1 Alaska: U.S. Geol. Survey Open-file Rept. 77-496, sheet, scale 1:1,000,000. 45 p. and 1 map, scale 1:2,500,000. Eittreim, Stephen, Grantz, Arthur, and Whitney, 0. T., Coffman, J. L., and Stover, C. W., eds., 1976, United 1977, Tectonic imprints on sedimentary deposits in States earthquakes, 1974: Natl. Tech. Inf. Service the Hope basin, in Blean, K. M., ed., The United PB-260 697/AS, 125 p. States Geological Survey in Coffman, J. L., von Hake, C. A., Spence, William, Alaska Accomplishments during 1976: U.S. Geol. Carver, D. L., and Covington, P. A., eds., 1976, Survey Circ. 751-B, p. B100-B103. United States earthquakes, 1973,: Natl. Tech. Inf. Feulner, A. J., and Reed, K. M., 1977, Bibliography of Service PB-250 362/AS, 118 p. reports by members of the U.S. Geological Survey Cohee, G. V., and Wright, W. B., 1976, Changes in on the water resources of Alaska, 1870 through stratigraphic nomenclature by the U.S. Geological 1976: U.S. Geol. Survey Open-file Rept. 77-687, Survey, 1975: U.S. Geol. Survey Bull. 1422-A, p. 112 p. A1-A84. Finch, W. I., 1977, United States Geological Survey Connelly, William, and Moore, J. C., 1977, Geologic uranium and thorium resource assessment and map of the northwest side of the Kodiak Islands, exploration research program, fiscal year 1977: Alaska: U.S. Geol. Survey Open-file Rept. 77-382, U.S. Geol. Survey Open-file Rept. 77-218, 27 p. 2 sheets, scales 1:250,000 and 1:63,360. Fisher, M. A., and Magoon, L. B., 1977, Geologic Cooper, A. K., 1977, Marine geophysical investigation framework of lower Cook Inlet, Alaska: U.S. Geol. in the Bering Sea basin, in Blean, K. M., ed., The Survey Open-file Rept. 77-136, 73 p. United States Geological Survey in Ford, A. B., and Brew, D. A., 1977a, Truncation of Alaska Accomplishments during 1976: U.S. Geol. regional metamorphic zonation pattern of the Survey Circ. 751-B, p. B98-B100. Juneau, Alaska, area by the Coast Range batholith, Csejtey, Bela, Jr., Nelson, W. H., Eberlein, G. D., in Blean, K. M., ed., The United States Geological Lanphere, M. A., and Smith, J. G., 1977, New data Survey in Alaska Accomplishments during 1976: concerning age of the Arkose Ridge Formation, U.S. Geol. Survey Circ. 751-B, p. B85-B87. south-central Alaska, in Blean, K. M., ed., The ___1977b, Chemical nature of Cretaceous greenstone United States Geological Survey in near Juneau, Alaska, in_ Blean, K. M., ed., The Alaska Accomplishments during 1976: U.S. Geol. United States Geological Survey in Survey Circ. 751-B, p. B62-B64. Alaska Accomplishments during 1976: U.S. Geol. Dearborn, L. L., 1977, Ground-water investigation at Survey Circ. 751-B, p. B88-B90. the alluvial fan of the South Fork Eagle River, 1977c, Preliminary geologic and Anchorage, Alaska - Results of test drilling, metamorphic-isograd map of northern parts of the 1976: U.S. Geol. Survey Open-file Rept. 77-493, 9 Juneau A-1 and A-2 quadrangles, Alaska: U.S. Geol. P. Survey Misc. Field Studies Map MF-847, 1 sheet, Detra, D. E., 1977, Delineation of an anomalous . scale 1:31,680. lead-zinc area in the Philip Smith Mountains A-2 Foster, H. L., Dusel-Bacon, Cynthia, and Weber, F. R., quadrangle, Alaska: U.S. Geol. Survey Open-file 1977, Reconnaissance geologic map of the Big Delta Rept. 77-223, 11 p. C-4 quadrangle, Alaska: U.S. Geol. Survey Detra, D. E., Smith, S. C., Risoli, D. A., and Day, G. Open-file Rept. 77-262, 1 sheet, scale 1:63,360. W., 1977, Spectrographic analyses of heavy-mineral Foster, H. L., Weber, F. R., and Dusel-Bacon, Cynthia, concentrate samples and chemical analyses of 1977, Gneiss dome in the Big Delta C-4 quadrangle, organic samples from the Chandalar quadrangle, Alaska, in_ Blean, K. M., ed., The United States Alaska: U.S. Geol. Survey Open-file Rept. 77-543, Geological Survey in Alaska Accomplishments 151 p. during 1976: U.S. Geol. Survey Circ. 751-B, p. Detterman, R. L., and Dutro, J. T., Jr., 1977, B33. Depositional environment and fauna for a section Gardner, J. V., and Vallier, T. L., 1977, Underway of the Sadlerochit Group, northeastern Alaska, in geophysical data collected on U.S.G.S. cruise Blean, K. M., ed., The United States Geological 54-76, southern Beringian shelf: U.S. Geol. Survey Survey in Alaska Accomplishments during 1976: Open-file Rept. 77-524, 5 p.

B-104 Grybeck, Donald, 1977a, Known mineral deposits of the Hudson, Travis, Plafker, George, and Lanphere, M. A., Brooks Range, Alaska: U.S. Geol. Survey Open-file 1977, Intrusive rocks of the Yakutat-St. Elias Rept. 77-166-C, 45 p. and 1 map, scale area, south-central Alaska: U.S. Geol. Survey 1:1,000,000. Jour. Research, v. 5, no. 2, p. 155-172. ___1977b, Map showing geochemical anomalies in the Hudson, Travis, Plafker, George, and Turner, D. L., Brooks Range, Alaska: U.S. Geol. Survey Open-file 1977, Metamorphic rocks of the Yakutat-St. Elias Rept. 77-166-D, 1 sheet, scale 1:1,000,000. area, south-central Alaska: U.S. Geol. Survey Grybeck, Donald, Beikman, H. M., Brosge, W. P., Jour. Research, v. 5, no. 2, p. 177-184. Tailleur, I. L., and Mull, C. G., 1977, Geologic Hudson, Travis, and Weber, F. R., 1977, The Donnelly map of the Brooks Range, Alaska: U. S. Geol. Dome and Granite Mountain faults, south-central Survey Open-file Rept. 77-166-B, 2 sheets, scale Alaska, in Blean, K. M., ed., The United States 1:1,000,000. Geological Survey in Alaska Accomplishments Grybeck, Donald, Brew, D. A., Johnson, B. R., and during 1976: U.S. Geol. Survey Circ. 751-B, p. Nutt, C. J., 1977, Ultramafic rocks in part of the B64-B66. Coast Range batholithic complex, southeastern Johnson, B. R., Forn, C. L., Hoffman, J. D., Brew, D. Alaska, in Blean, K. M., ed., The United States A., and Nutt, C. J., 1977, Geochemical sampling of Geological Survey in Alaska Accomplishments stream sediments, Tracy Arm, southeastern Alaska, during 1976: U.S. Geol. Survey Circ. 751-B, p. in_ Blean, K. M., ed., The United States Geological B82-B85. Survey in Alaska Accomplishments during 1976: Hamilton, T. D., 1977, Surficial geology of the U.S. Geol. Survey Circ. 751-B, p. B80-B82. east-central Brooks Range, in Blean, K. M., ed., Kachadoorian, Reuben, Ovenshine, A. T., and The United States Geological Survey in Bartsch-Winkler, Susan, 1977, Late Wisconsin Alaska Accomplishments during 1976: U.S. Geol. history of the south shore of Turnagain Arm, Survey Circ. 751-B, p. B15-B16. Alaska, in_ Blean, K. M., ed., The United States Hampton, M. A., and Bouma, A. H., 1977, Seismic Geological Survey in Alaska Accomplishments reflection records showing stable and unstable during 1976: U.S. Geol. Survey Circ. 751-B, p. slopes near the shelf break, western Gulf of B49-B50. Alaska: U.S. Geol. Survey Open-file Rept. 77-702, Karlson, R. C., Curtin, G. C., Cooley, E. F., and 30 p. (unnumbered). Garmezy, L., 1977, Geochemical maps of selected Hardin, Deborah, Barnes, Peter, and Reimnitz, Erk, elements and results of spectrographic analyses 1977, Distribution and character of naleds in for heavy-mineral concentrates from the western northeastern Alaska: U.S. Geol. Survey Open-file half of the Talkeetna Mountains quadrangle, Rept. 77-91, 28 p. Alaska: U.S. Geol. Survey Open-file Rept. 77-530, Hein, J. R., Bouma, A. H., and Hampton, M.- A., 1977, 32 p. and 5 maps, scale 1:250,000. Distribution of clay minerals in lower Cook Inlet Keith, T. E. C., and Foster, H. L., 1977, Ultramafic and Kodiak shelf sediment, Alaska: U.S. Geol. rocks near Volkmar Lake, Big Delta quadrangle, Survey Open-file Rept. 77-581, 17 p. Yukon-Tanana Upland, Alaska, in_ Blean, K. M., ed., Hoare, J. M., and Cobb, E. H., 1977, Mineral The United States Geological Survey in occurrences (other than mineral fuels and Alaska Accomplishments during 1976: U.S. Geol. construction materials) in the Bethel, Goodnews, Survey Circ. 751-B, p. B32-B33. and Russian Mission quadrangles, Alaska: U.S. Kelley, J. S., 1977, Study of heavy minerals from Geol. Survey Open-file Rept. 77-156, 98 p. Tertiary rocks at Capps Glacier and adjacent Hoare, J. M., and Coonrad, W. L., 1977, Blue amphibole areas, southern Alaska: U.S. Geol. Survey occurrences in southwestern Alaska, in Blean, K. Open-file Rept. 77-502, 11 p. M., ed., The United States Geological Survey in Koch, R. D., Elliott, R. L., Smith, J. G., and Berg, Alaska Accomplishments during 1976: U.S. Geol. H. C., 1977, Metamorphosed trondhjemite of the Survey Circ. 751-B, p. B39. Alexander terrane in Coast Range plutonic complex, Hopkins, D. M., 1977, Coastal processes and coastal in_ Blean, K. M., ed., The United States Geological erosion hazards to the Cape Krusenstern Survey in Alaska Accomplishments during 1976: archaeological site: U.S. Geol. Survey Open-file U.S. Geol. Survey Circ. 751-B, p. B72-B74. Rept. 77-32, 17 p. Koch, R. D., Smith, J. G., and Elliott, R. L., 1977, Hudson, Travis, 1977a, Genesis of a zoned granitic Miocene or younger strike-slip(?) fault at Canoe stock, Seward Peninsula, Alaska: U.S. Geol. Survey Passage, southeastern Alaska, i.n_ Blean, K. M., Open-file Rept. 77-35, 188 p. ed., The United States Geological Survey in ___1977b, Preliminary geologic map of Seward Alaska Accomplishments during 1976: U.S. Geol. Peninsula, Alaska: U.S. Geol. Survey Open-file Survey Circ. 751-B, p. B76. Rept. 77-167-A, 1 sheet, scale 1:1,000,000. Kososki, B. A., and Anderson, R. C., 1977, Digital J977c, Map showing preliminary framework data for processing of a 24 channel, single-fold seismic evaluation of the metallic mineral resource reflection line from Naval Petroleum Reserve No. potential of northern Seward Peninsula, Alaska: 4, Alaska: U.S. Geol. Survey Open-file Rept. U.S. Geol. Survey Open-file Rept. 77-167-B, 1 77-707, 7 p. sheet, scale 1:1,000,000. Lachenbruch, A. H., and Marshall, B. V., 1977, Sub-sea Hudson, Travis, Elliott, R. L., and Smith, J. G., temperatures and a simple tentative model for 1977, Investigations of the Wilson Arm molybdenite offshore permafrost at Prudhoe Bay, Alaska: U.S. deposit, in_ Blean, K. M., ed., The United States Geol. Survey Open-file Rept. 77-395, 54 p. Geological Survey in Alaska Accomplishments Lanphere, M. A., Churkin, Michael, Jr., and Eberlein, during 1976: U.S. Geol. Survey Circ. 751-B, p. G. D., 1977, A new radiometric date for the B74. Ordovician-Silurian boundary, in Blean, K. M., Hudson, Travis, Foster, H. L., and Weber, F. R., 1977, ed., The United States Geological Survey in The Shaw Creek fault, east-central Alaska, in Alaska Accomplishments during 1976: U.S. Geol. Blean, K. M., ed., The United States Geological Survey Circ. 751-B, p. B4-B5. Survey in Alaska Accomplishments during 1976: MacKevett, E. M., Jr., Albert, N. R. D., Barnes, D. U.S. Geol. Survey Circ. 751-B, p. B33-B34. F., Case, J. E., Robinson, Keith, and Singer, D.

B-105 A., 1977, The Alaska Mineral Resource Assessment Mull, C. G., 1977, Apparent south vergent folding and Program; Background information to accompany folio possible nappes in Schwatka Mountains, in Blean, of geologic and mineral resource maps of the K. M., ed., The United States Geological Survey in McCarthy quadrangle, Alaska: U.S. Geol. Survey Alaska Accomplishments during 1976: U.S. Geol. Circ. 739, 23 p. Survey Circ. 751-B, p. B29-B31. MacKevett, E. M., Jr., and Holloway, C. D., 1977, Map Mull, C. G., and Kososki, B. A., 1977, Hydrocarbon showing metalliferous and selected assessment of the Arctic National Wildlife Range, nonmetalliferous mineral deposits in the eastern eastern Arctic Slope, Alaska, in^ Blean, K. M., part of southern Alaska: U.S. Geol. Survey ed., The United States Geological Survey in Open-file Rept. 77-169-A, 1 sheet and 99 p. Alaska Accomplishments during 1976: U.S. Geol. tabular material, scale 1:1,000,000. Survey Circ. 751-B, B20-B22. Mann, D. M., 1977, Shelled benthic fauna of the Mull, C. G., and Tailleur, I. L., 1977, SadlerochitC?) eastern Chukchi Sea: U.S. Geol. Survey Open-file Group in the Schwatka Mountains, south-central Rept. 77-672, 112 p. Brooks Range, in^ Blean, K. M., ed., The United Marlow, M. S., 1977, Resource assessment and States Geological Survey in geophysical exploration of the southern Bering Sea Alaska Accomplishments during 1976: U.S. Geol. shelf, i£ Blean, K. M., ed., The United States Survey Circ. 751-B, p. B27-B29. Geological Survey in Alaska Accomplishments Nauman, J. W., and Kernodle, D. R., 1977, Aquatic during 1976: U.S. Geol. Survey Circ. 751-B, p. organisms from selected sites along the B97-B98. trans-Alaska pipeline corridor, September 1970 to Mayo, L. R., 1977, Glacier research, in_ Blean, K. M., September 1972: U.S. Geol. Survey Open-file Rept. ed., The United States Geological Survey in 77-634, 55 p. Alaska Accomplishments during 1976: U.S. Geol. Nauman, J. W., Sloan, C. E., and Kernodle, D. R., Survey Circ. 751-B, p. B5-B6. 1977a, Effects of fuel oil leaks on water quality Mayo, L. R., Zenone, Chester, and Trabant, D. C., in three streams along the trans-Alaska pipeline, 1977, Reconnaissance hydrology of Portage Glacier i£ Blean, K. M., ed., The United States Geological basin, Alaska - 1972: U.S. Geol. Survey Hydrol. Survey in Alaska: accomplishments during 1976: Inv. Atlas HA-583, 2 sheets, scale 1:50,000. U.S. Geol. Survey Circ. 751-B, p. B7. McCoy, G. A., 1977, Fisheries enhancement studies; ___1977b, Stream relocation and benthic limnological studies in southeastern Alaska and invertebrates in Canyon Slough near Valdez, in water quality measurements along the TAPS route Blean, K. M., ed., The United States Geological during pipeline construction, in_ Blean, K. M., Survey in Alaska: accomplishments during 1976: ed., The United States Geological Survey in U.S. Geol. Survey Circ. 751-B, p. B46. Alaska Accomplishments during 1976: U.S. Geol. Nelson, G. L., 1977a, North Slope water resources Survey Circ. 751-B, p. B7-B8. studies, i£ Blean, K. M., ed., The United States ___1977b, A reconnaissance investigation of a large Geological Survey in Alaska Accomplishments meromictic lake in southeastern Alaska: U.S. Geol. during 1976: U.S. Geol. Survey Circ. 751-B, p. Survey Jour. Research, v. 5, no. 3, p. 319-324. B31. McCoy, G. A., Wiggins, W. W., and Schmidt, A. E., ___1977b, Geohydrology of the Fairbanks-North Star 1977, Limnological investigation of six lakes in Borough, in Blean, K. M., ed., The United States southeast Alaska: U.S. Geol. Survey Water Geological Survey in Alaska Accomplishments Resources Inv. Rept. WRI-76-122, 1 sheet. during 1976: U.S. Geol. Survey Circ. 751-B, McLean, Hugh, 1977, Organic geochemistry, lithology, B36-B37. and paleontology of Tertiary and Mesozoic rocks Nelson, Hans, 1977, Ice gouging and other from wells on the Alaska Peninsula: U.S. Geol. environmental geologic problems of northern Bering Survey Open-file Rept. 77-813, 63 p. Sea, in_ Blean, K. M., ed., The United States McManus, D. A., Kolla, Venkatarathnam, Hopkins, D. M., Geological Survey in Alaska Accomplishments and Nelson, C. H., 1977, Distribution of bottom during 1976: U.S. Geol. Survey Circ. 751-B, p. sediments on the continental shelf, northern B98. Bering Sea: U.S. Geol. Survey Prof. Paper 759-C, Ovenshine, A. T., Bartsch-Winkler, Susan, Rupert, p. C1-C31. Jeff, and Kachadoorian, Reuben, 1977, Preliminary Miller, R. J., Curtin, G. C., Hopkins, R. T., Jr., and studies of a 93-meter core at Portage, Alaska, in Csejtey, Be1 la, Jr., 1977, Spectrographic and Blean, K. M., ed., The United States Geological chemical analyses of stream-sediment and rock Survey in Alaska Accomplishments during 1976: samples from the western part of the Talkeetna U.S. Geol. Survey Circ. 751-B, p. B50-B51. Mountains quadrangle, Alaska: U.S. Geol. Survey Page, N.J, Berg, H. C., and Haffty, Joseph, 1977, Open-file Rept. 77-471, 138 p. Platinum, palladium, and rhodium in volcanic and Miller, T. P., 1977, Geologic interpretation of a plutonic rocks from the Gravina-Nutzotin belt, radioactivity anomaly near the West Fork of the Alaska: U.S. Geol. Survey Jour. Research, v. 5, Buckland River, western Alaska: U.S. Geol. Survey no. 5, p. 629-636. Open-file Rept. 77-372, 9 p. Palmer, I. F., and Lyle, W. M., 1977, Cooperative Miller, T. P., and Elliott, R. L., 1977, Progress stratigraphic project in lower Cook Inlet and report on uranium investigations in the Zane Hills Kodiak areas, U.S. Geological Survey and State of area, west-central Alaska: U.S. Geol. Survey Alaska Division of Geological and Geophysical Open-file Rept. 77-428, 12 p. Surveys, in Blean, K. M., ed., The United States Minsch, J. H., Stover, C. W., Person, W. J., and Geological Survey in Alaska Accomplishments Simon, R. B., 1977, Earthquakes in the United during 1976: U.S. Geol. Survey Circ. 751-B, p. States, October-December 1975: U.S. Geol. Survey B45-B46. Circ. 749-D, p. D1-D27. Patton, W. W., Jr., 1977, Pre-Ordovician unconformity Molnia, B. F., 1977, Surface sedimentary units of the in central Alaska, in Blean, K. M., ed., The Gulf of Alaska continental shelf; Montague Island United States Geological Survey in to Yakutat Bay: U.S. Geol. Survey Open-file Rept. Alaska Accomplishments during 1976: U.S. Geol. 77-30, 21 p. Survey Circ. 751-B, p. B39.

B-106 Patton, W. W., Jr., Dutro, J. T., Jr., and Chapman, R. sheet, scale 1:63,360. M., 1977, Late Paleozoic and Mesozoic stratigraphy Robinson, Keith, McDougal, C. M., Day, G. W., and of the Nixon Fork area, Medfra quadrangle, Alaska, Billings, Theodore, 1976a, Distribution and in Blean, K. M., ed., The United States Geological abundance of copper in stream sediments and Survey in Alaska Accomplishments during 1976: moraine debris, McCarthy quadrangle, Alaska: U.S. U.S. Geol. Survey Circ. 751-B, p. B38-B40. Geol. Survey Misc. Field Studies Map MF-773-F, 1 Patton, W. W., Jr., Miller, T. P., Chapman, R. M., and sheet, scale 1:250,000. Yeend, Warren, 1977, Geologic map of the Melozitna ___1976b, Distribution and abundance of lead in quadrangle, Alaska: U.S. Geol. Survey Open-file stream sediments and moraine debris, McCarthy Rept. 77-147, 1 sheet, scale 1:250,000. quadrangle, Alaska: U.S. Geol. Survey Misc. Field Person, W. J., Simon, R. B., and Stover, C. W., 1977, Studies Map MF-773-G, 1 sheet, scale 1:250,000. Earthquakes in the United States, April-June 1975: 1976c, Distribution and abundance of gold in U.S. Geol. Survey Circ. 749-B, p. B1-B27. stream sediments and moraine debris, McCarthy Pessel, G. H., and Brosge, W. P., 1977, Preliminary quadrangle, Alaska: U.S. Geol. Survey Misc. Field reconnaissance geologic map of Ambler River Studies Map MF-773-H, 1 sheet, scale 1:250,000. quadrangle, Alaska: U.S. Geol. Survey Open-file Robinson, Keith, McDougal, C. M., McDanal, S. K., and Rept. 77-28, 1 sheet, scale 1:250,000. Billings, Theodore, 1976a, Distribution and Petty-Ray Geophysical Division, Geosource, Inc., 1977, abundance of molybdenum in bedrock,'mineralized, Marine high resolution geophysical survey - lower vein, and altered rock samples, McCarthy Cook Inlet, Alaska: U.S. Geol. Survey Open-file quadrangle, Alaska: U.S. Geol. Survey Misc. Field Rept. 77-358, 166 p. and 22 illus., scale Studies Map MF-773-J, 1 sheet, scale 1:250,000. 1:96,000. ___1976b, Distribution and abundance of silver in Pew<§, T. L., Bell, J. W., Forbes, R. B., and Weber, F. bedrock, mineralized, vein, and altered rock R., 1975, Geologic map of the Fairbanks D-2 NW samples, McCarthy quadrangle, Alaska: U.S. Geol. quadrangle, Alaska: U.S. Geol. Survey Misc. Inv. Survey Misc. Field Studies Map MF-773-K, 1 sheet, Series Map 1-907, 1 sheet, scale 1:24,000. scale 1:250,000. ___1976, Geologic map of the Fairbanks D-2 SE 1976c, Distribution and abundance of gold in quadrangle, Alaska: U.S. Geol. Survey Misc. Inv. bedrock, mineralized, vein, and altered rock Series Map 1-942, 1 sheet, scale 1:24,000. samples, McCarthy quadrangle, Alaska: U.S. Geol. 1977, Geologic map of the Fairbanks D-2 NE Survey Misc. Field Studies Map MF-773-L, 1 sheet, quadrangle, Alaska: U.S. Geol. Survey Misc. Inv. scale 1:250,000. Series Map 1-950, 1 sheet, scale 1:24,000. Robinson, Keith, McDougal, C. M., O'Leary, R. M., and Pew<§, T. L., Bell, J. W., Williams, J. R., and Paige, Billings, Theodore, 1976, Distribution and R. A., 1976, Geologic map of the Fairbanks D-1 SW abundance of arsenic in bedrock, mineralized, quadrangle, Alaska: U.S. Geol. Survey Misc. Inv. vein, and altered rock samples, McCarthy Series Map 1-949, 1 sheet, scale 1:24,000. quadrangle, Alaska: U.S. Geol. Survey Misc. Field Plafker, George, Hudson, Travis, and Richter, D. H., Studies Map MF-773-M, 1 sheet, scale 1:250,000. 1977, Preliminary observations on late Cenozoic Robinson, Keith, O'Leary, R. M., McDougal, C. M., and displacements along the Totschunda and Denali Billings, Theodore, 1976, Distribution and fault systems, ir^ Blean, K. M., ed., The United abundance of arsenic and mercury in stream States Geological Survey in sediments and moraine debris, McCarthy quadrangle, Alaska Accomplishments during 1976: U.S. Geol. Alaska: U.S. Geol. Survey Misc. Field Studies Map Survey Circ. 751-B, p. B67-B69. MF-773-I, 1 sheet, scale 1:250,000. Plafker, George, Jones, D. L., and Pessagno, E. A., Sable, E. G., 1977, Geology of the western Romanzof Jr., 1977, A Cretaceous accretionary flysch and Mountains, Brooks Range, Alaska: U.S. Geol. Survey melange terrane along the Gulf of Alaska margin, Prof. Paper 897, 84 p. i£ Blean, K. M., ed., The United States Geological Savage, N. M., Eberlein, G. D., and Churkin, Michael, Survey in Alaska Accomplishments during 1976: Jr., 1977, Early Devonian conodonts found with a U.S. Geol. Survey Circ. 751-B, p. B41-B43. classical Upper Silurian brachiopod fauna, Plafker, George, Richter, D. H., and Hudson, Travis, southeastern Alaska, ir± Blean, K. M., ed., The 1977, Reinterpretation of the origin of inferred United States Geological Survey in Tertiary tillite in the northern Wrangell Alaska Accomplishments during 1976: U.S. Geol. Mountains, Alaska, in^ Blean, K. M., ed., The Survey Circ. 751-B, p. B79-B81. United States Geological Survey in Schmoll, H. R., 1977, Engineering geology of Anchorage Alaska Accomplishments during 1976: U.S. Geol. Borough, i£ Blean, K. M., ed., The United States Survey Circ. 751-B, p. B52-B54. Geological Survey in Alaska Accomplishments Post, Austin, 1977, Reported observations of icebergs during 1976: U.S. Geol. Survey Circ. 751-B, p. from Columbia Glacier in Valdez Arm and Columbia B51-B52. Bay, Alaska, during the summer of 1976: U.S. Geol. Silberman, M. L., Mathews, Alan, Potter, R. W., and Survey Open-file Rept. 77-235, 7 p. Nissenbaum, Arie, 1977, Stable isotope Rau, W. W., Plafker, George, and Winkler, G. R., 1977, geochemistry, sulfide mineralogy, and Preliminary foraraLniferal biostratigraphy and potassium-argon ages of the Kennecott massive correlation of selected stratigraphic sections and sulfide deposits, Alaska, i£ Blean, K. M., ed., wells in the Gulf of Alaska Tertiary Province: The United States Geological Survey in U.S. Geol. Survey Open-file Rept. 77-747, 54 p. Alaska Accomplishments during 1976: U.S. Geol. Reimnitz, Erk, Maurer, Doug, Barnes, Peter, and Survey Circ. 751-B, p. B56-B58. Toimil, Larry, 1977, Some physical properties of Silberman, M. L., Morton, J. L., Cox, D. C., and shelf surface sediments, Beaufort Sea, Alaska: Richter, D. H., 1977, Potassium-argon ages of U.S. Geol. Survey Open-file Rept. 77-416, 23 p. disseminated copper and molybdenum mineralization Richter, D. H., Sharp, W. N., Dutro, J. T., Jr., and of the Klein Creek and Nabesna plutons, eastern Hamilton, W. B., 1977, Geologic map of parts of Alaska Range, in_ Blean, K. M., ed., The United the Mount Hayes A-1 and A-2 quadrangles, Alaska: States Geological Survey in U.S. Geol. Survey Misc. Inv. Series Map 1-1031, 1 Alaska Accomplishments during 1976: U.S. Geol.

B-107 Survey Circ. 751-B, p. B54-B56. 1977b, Mineral resources of the western Brooks Simon, R. B., Stover, C. W., and Person, W. J., 1977, Range, in^ Blean, K. M., ed., The United States Earthquakes in the United States, January-March Geological Survey in Alaska Accomplishments 1975: U.S. Geol. Survey Circ. 749-A, 35 p. during 1976: U.S. Geol. Survey Circ. 751-B, p. Sims, J. D., and Rymer, M. J., 1977, Study of modern B24-B25. lacustrine and glaciolacustrine sediments for Tailleur, I. L., Mayfield, C. F., and Ellersieck, I. earthquake-induced deformational structures, Kenai F., 1977, Late Paleozoic sedimentary sequence, Peninsula, ir^ Blean, K. M., ed., The United States southwestern Brooks Range, in Blean, K. M., ed., Geological Survey in Alaska Accomplishments The United States Geological Survey in during 1976: U.S. Geol. Survey Circ. 751-B, p. Alaska Accomplishments during 1976: U.S. Geol. B46-B47. Survey Circ. 751-B, p. B25-B27. Singer, D. A., Curtin, G. C., and Foster, H. L., 1976, Tangborn, W. V., Mayo, L. R., Scully, D. R., and Mineral resources map of the Tanacross quadrangle, Krimmel, R. M., 1977, Combined ice and water Alaska: U.S. Geol. Survey Misc. Field Studies Map balances of Maclure Glacier, California, South MF-767-E, 1 sheet, scale 1:250,000. Cascade Glacier, Washington, and Wolverine and Singer, D. A., and MacKevett, E. M., Jr., 1977, Gulkana Glaciers, Alaska, 1967 hydrologic year: Mineral resources map of the McCarthy quadrangle, U.S. Geol. Survey Prof. Paper 715-B, p. B1-B19. Alaska: U.S. Geol. Survey Misc. Field Studies Map Townshend, J. B., Papp, J. E., Moorman, M. J., MF-773-C, 1 sheet, scale 1:250,000. Deadmon, C. E., and Tilton, S. P., 1976a, Skibitzke, H. E., 1977, Some aspects of remote sensing Preliminary geomagnetic data, College Observatory, for consideration in planning environmental Fairbanks, Alaska, November 1976: U.S. Geol. monitoring of the Aleyska Pipeline, Alaska: U.S. Survey Open-file Rept. 76-300-K, 20 p. Geol. Survey Open-file Rept. 77-643, 32 p. and 9 (unnumbered). sheets. ____1976b, Preliminary geomagnetic data, College Slack, J. R., Smith, R. A., and Wyant, Timothy, 1977, Observatory, Fairbanks, Alaska, December 1976: An oilspill risk analysis for the western Gulf of U.S. Geol. Survey Open-file Rept. 76-300-L, 21 p. Alaska (Kodiak Island) Outer Continental Shelf (unnumbered). lease area: U.S. Geol. Survey Open-file Rept. ___1977a, Preliminary geomagnetic data, College 77-212, 57 p. Observatory, Fairbanks, Alaska, January 1977: U.S. Slack, K. V., Nauman, J. W., and Tilley, L. J., 1977, Geol. Survey Open-file Rept. 77-300-A, 20 p. Benthic invertebrates in an arctic mountain (unnumbered). stream, Brooks Range, Alaska: U.S. Geol. Survey 1977b, Preliminary geomagnetic data, College Jour. Research, v. 5, no. 4, p. 519-527. Observatory, Fairbanks, Alaska, February 1977: Sloan, C. E., 1977, Arctic hydrology studies, in U.S. Geol. Survey Open-file Rept. 77-300-B, 19 p. Blean, K. M., ed., The United States Geological __1977c, Preliminary geomagnetic data, College Survey in Alaska Accomplishments during 1976: "Observatory, Fairbanks, Alaska, March 1977: U.S. U.S. Geol. Survey Circ. 751-B, p. B30-B31. Geol. Survey Open-file Rept. 77-300-C, 20 p. Sloan, C. E., and Nauman, J. W., 1977, Investigations (unnumbered). of impact on hydrologic features by construction 1977d, Preliminary geomagnetic data, College and operation of TAPS, ill Blean, K. M., ed., The Observatory, Fairbanks, Alaska, April 1977: U.S. United States Geological Survey in Geol. Survey Open-file Rept. 77-300-D, 20 p. Alaska Accomplishments during 1976: U.S. Geol. (unnumbered). Survey Circ. 751-B, p. B6. Townshend, J. B., Papp, J. E., Moorman, M. J., and Smith, J. G., 1977, Geology of the Ketchikan D-1 and Tilton, S. P., 1977a, Preliminary geomagnetic Bradfield Canal A-1 quadrangles, southeastern data, College Observatory, Fairbanks, Alaska, May Alaska: U.S. Geol. Survey Bull. 1425, 49 p. 1977: U.S. Geol. Survey Open-file Rept. 77-300-E, Smith, J. G., Elliott, R. L., Berg, H. C., and 18 p. (unnumbered). Wiggins, B. D., 1977, Map showing general geology ____1977b, Preliminary geomagnetic data, College and location of chemically and radiometrically Observatory, Fairbanks, Alaska, June 1977: U.S. analyzed samples in parts of the Ketchikan, Geol. Survey Open-file Rept. 77-300-F, 18 p. Bradfield Canal, and Prince Rupert quadrangles, (unnumbered). southeastern Alaska: U.S. Geol. Survey Misc. Field ___1977c, Preliminary geomagnetic data, College Studies Map MF-825, 2 sheets, scale 1:250,000. Observatory, Fairbanks, Alaska, July 1977: U.S. Staatz, M. H., 1977, I and L vein system, Bokan Geol. Survey Open-file Rept. 77-300-G, 19 p. Mountain, Prince of Wales Island, in Blean, K. M., (unnumbered). ed., The United States Geological Survey in ___1977d, Preliminary geomagnetic data, College Alaska Accomplishments during 1976: U.S. Geol. Observatory, Fairbanks, Alaska, August 1977: U.S. Survey Circ. 751-B, p. B74-B75. Geol. Survey Open-file Rept. 77-300-H, 20 p. Staatz, M. H., Conklin, N. M., and Brownfield, I. K., (unnumbered). 1977, Rare earths, thorium, and other minor ___1977e, Preliminary geomagnetic data, College elements in sphene from some plutonic rocks in Observatory, Fairbanks, Alaska, September 1977: west-central Alaska: U.S. Geol. Survey Jour. U.S. Geol. Survey Open-file Rept. 77-300-1, 20 p. Research, v. 5, no. 5, p. 623-628. (unnumbered). Stover, C. W., Simon, R. B., Person, W. J., and 1977f, Preliminary geomagnetic data, College Minsch, J. H., 1977, Earthquakes in the United Observatory, Fairbanks, Alaska, October 1977: U.S. States, July-September 1975: U.S. Geol. Survey Geol. Survey Open-file Rept. 77-300-J, 20 p. Circ. 749-C, p. C1-C29. (unnumbered). Tailleur, I. L., Ellersieck, I. F., and Mayfield, C. Tysdal, R. G., and Case, J. E., 1977a, Placer River F., 1977a, Southwestern Brooks Range - Ambler fault, Seward and Elying Sound quadrangles, in River quadrangle AMRAP, in Blean, K. M., ed., The Blean, K. M., ed., The United States Geological United States Geological"~Survey in Survey in Alaska Accomplishments during 1976: Alaska Accomplishments during 1976: U.S. Geol. U.S. Geol. Survey Circ. 751-B, p. B47-B48. Survey Circ. 751-B, p. B22-B24. ___1977b, The McHugh Complex in the Seward

B-108 quadrangle, south-central Alaska, in_ Blean, K. M., 1:63,360. ed., The United States Geological Survey in 1977dd, Sagavanirktok D-3 quadrangle, scale Alaska Accomplishments during 1976: U.S. Geol. T:63,360. Survey Circ. 751-B, p. B47-B49. 1977ee, Tanana D-1 quadrangle, scale 1:63,360. U.S. Geological Survey, 1976a, Geological Survey ~1977ff, Wiseman A-1 quadrangle, scale 1:63,360. Research 1976: U.S. Geol. Survey Prof. Paper 1000, 1977gg, Wiseman B-1 quadrangle, scale 1:63,360. 414 p. Vallier, T. L., and Gardner, J. V., 1977, Maps showing ___1976b, Status of land in the McCarthy quadrangle, types and distribution of faults interpreted from Alaska: U.S. Geol. Survey Misc. Field Studies Map seismic profiles in the St. George Basin region, MF-773-0, 1 sheet, scale 1:250,000. southern Bering Sea: U.S. Geol. Survey Open-file _1977a, Aeromagnetic map of the Ketchikan, Prince Rept. 77-591, 13 p. and 2 sheets. Rupert, and northeastern Craig quadrangles, Van Trump, George, Robinson, Keith, O'Leary, R. M., Alaska: U.S. Geol. Survey Open-file Rept. 77-359, Day, G. W., and McDougal, C. M., 1977a, Magnetic 1 sheet, scale 1:250,000. tape containing results of spectrographic and ___1977b, Aeromagnetic map of the Philip Smith chemical analyses of geochemical samples from the Mountains quadrangle, Alaska: U.S. Geol. Survey McCarthy quadrangle, Alaska: Natl. Tech. Inf. Open-file Rept. 77-572, 1 sheet, scale 1:250,000. Service PB-266 9027AS, magnetic tape. ___1977c, Seismic engineering program report, ___1977b, Magnetic tape containing results of July-September 1976: U.S. Geol. Survey Circ. spectrographic and chemical analyses of 736-C, 14 p. geochemical samples from the McCarthy quadrangle, ___1977d, Seismic engineering program report, Alaska (User's guide): Natl. Tech. Inf. Service October-December 1976: U.S. Geol. Survey Circ. PB-266 903/AS, 20 p. 736-D, 23 p. Vennum, W. R., and Eberlein, G. D., 1977, Spherulitic ___1977e, Seismic engineering program report, rhyolite dike from Goat Island, southeastern January-April 1977: U.S. Geol. Survey Circ. 762-A, Alaska: U.S. Geol. Survey Jour. Research, v. 5, 28 p. no. 4, p. 445-451. ___1977f, Seismic engineering program report, Wallace, A. R., and Cady, J. W., 1977, Geophysical and May-August 1977: U.S. Geol. Survey Circ. 762-B, 26 petrologic studies of radioactive contact zones of P- pyroxenite dikes in nepheline syenite of the Ekiek 1977g, Water resources data for Alaska - water Creek pluton, western Alaska, in Campbell, J. A., year 1975: Natl. Tech. Inf. Service PB-264 228/AS, ed., Short papers of the U.S. Geological Survey 424 p. uranium-thorium symposium, 1977: U.S. Geol. Survey U.S. Geological Survey, Topographic Division, 1977a, Circ. 753, p. 6-8. Settles A-1 quadrangle, Alaska: U.S. Geol. Survey, Weber, F. R., Foster, H. L., and Keith, T. E. C., Topog. Ser., scale 1:63,360. 1977a, A newly identified sequence of rocks in the ___1977b, Settles B-1 quadrangle, scale 1:63,360. Yukon-Tanana Upland, Alaska, in_ Blean, K. M., ed., ___1977c, Settles B-2 quadrangle, scale 1:63,360. The United States Geological Survey in ___1977d, Settles C-2 quadrangle, scale 1:63,360. Alaska Accomplishments during 1976: U.S. Geol. ___1977e, Settles D-1 quadrangle, scale 1:63,360. Survey Circ. 751-B, p. B31-B32. ___1977f, Settles D-2 quadrangle, scale 1:63,360. ___1977b, Reconnaissance geologic map of the Big ___1977g, Big Delta A-5 quadrangle, scale 1:63,360. Delta A-2 and A-3 quadrangles, Alaska: U.S. Geol. ___1977h, Big Delta C-6 quadrangle, scale 1:63,360. Survey Misc. Field Studies Map MF-869, 1 sheet, ___1977i, Chandalar B-6 quadrangle, scale 1:63,360. scale 1:63,360. ___1977J, Chandalar C-6 quadrangle, scale 1:63,360. Weber, F. R., and Turner, D. L., 1977, A late Tertiary ___1977k, Chandalar D-6 quadrangle, scale 1:63,360. thrust fault in the central Alaska Range, in ___19771, Fairbanks C-1 quadrangle, scale 1:63,360. Blean, K. M., ed., The United States Geological ___1977m, Fairbanks D-1 quadrangle, scale 1:63,360. Survey in Alaska Accomplishments during 1976: ___1977n, Fairbanks D-2 quadrangle, scale 1:63,360. U.S. Geol. Survey Circ. 751-B, p. B66-B67. ___1977o, Livengood B-3 quadrangle, scale 1:63,360. Whitmore, F. C., Jr., and Card, L. M., Jr., 1977, ___1977p, Livengood C-4 quadrangle, scale 1:63,360. Steller's sea cow (Hydrodamalis gigas) of late ___1977q, Livengood C-5 quadrangle, scale 1:63,360. Pleistocene age from Amchitka, Aleutian Islands, ___1977r, Livengood D-5 quadrangle, scale 1:63,360. Alaska: U.S. Geol. Survey Prof. Paper 1036, 19 p. ___1977s, Philip Smith Mountains A-4 quadrangle, Williams, J. R., Yeend, W. E., Carter, L. D., and scale 1:63,360. Hamilton, T. D., 1977, Preliminary surficial 1977t, Philip Smith Mountains A-5 quadrangle, deposits map of National Petroleum Reserve - scale 1:63,360. Alaska: U.S. Geol. Survey Open-file Rept. 77-868, _1977u, Philip Smith Mountains B-4 quadrangle, 2 sheets, scale 1:500,000. scale 1:63,360. Wilson, F. H., 1977, Soms plutonic rocks of __1977v, Philip Smith Mountains B-5 quadrangle, southwestern Alaska, a data compilation, 1977: scale 1:63,360. U.S. Geol. Survey Open-file Rept. 77-501, 9 p. and _J977w, Philip Smith Mountains C-4 quadrangle, 4 sheets. scale 1:63,360. Winkler, G. R., MacKevett, E. M., Jr., and Nelson, S. _1977x, Philip Smith Mountains C-5 quadrangle, W., 1977, Strata-bound iron-copper-zinc deposits, scale 1:63,360. Prince William Sound region, southern Alaska, in _1977y, Philip Smith Mountains D-4 quadrangle, Blean, K. M., ed., The United States Geological scale 1:63,360. Survey in Alaska: accomplishmsnts during 1976: _1977z, Sagavanirktok A-3 quadrangle, scale U.S. Geol. Survey Circ. 751-B, p. B44-B45. 1:63,360. Winkler, G. R., and Tysdal, R. G., 1977, Conglomerate 1977aa, Sagavanirktok A-4 quadrangle, scale in flysch of the Orca Group, Prince William Sound, 1:63,360. southern Alaska, in Blean, K. M., ed., The United 1977bb, Sagavanirktok B-3 quadrangle, scale States Geological Survey in T:63,360. Alaska Accomplishments during 1976: U.S. Geol. __1977cc, Sagavanirktok C-3 quadrangle, scale Survey Circ. 751-B, p. B43-B44.

B-109 Yeend, W. E., 1977, Tertiary and Quaternary deposits of The Palisades, central Alaska: U.S. Geol. REVISIONS TO 1:1,000,000-SCALE MAP OF Survey Jour. Research, v. 5, no. 60, p. 747-752. ALASKA Yehle, L. A., 1977a, Reconnaissance engineering geology and geologic hazards of the Metlakatla area, Annette Island, in_ Blean, K. M., ed., The INTRODUCTION United States Geological Survey in Alaska Accomplishments during 1976: U.S. Geol. Survey Circ. 751-B, p. B72. ___1977b, Reconnaissance engineering geology of the Geologic mapping in Alaska is an ongoing pro Metlakatla area, Annette Island, Alaska, with cess, each field season yielding new information emphasis on evaluation of earthquakes and other geologic hazards: U.S. Geol. Survey Open-file and insights. Office compilation of new data per- Rept. 77-272, 93 p. mits periodic updating of parts of the Zenone, Chester, 1977, Urban hydrology studies in the l:l,000,000-scale published map of the State Anchorage area, in Blean, K. M., ed., The United States Geological Survey in (Beikman, 1974a, 1974b, 1975a, 1975b; Beikman Alaska Accomplishments during 1976: U.S. Geol. and Lathram, 1976). Included in this chapter are Survey Circ. 751-B, p. B52. updated maps for two areas of the State; the Goodnews and Hagemeister Island quadrangles and the Ketchikan and Prince Rupert quadran gles. These maps are discussed in papers in "Summary of Important Results." It is hoped that this format will allow interested parties to keep their l:l,000,000-scale maps as current as possible, as it will be some time before a com plete revision can be made.

REFERENCES CITED

Beikman, H. M., 1974a, Preliminary geologic map of the southwest quadrant of Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-611, 2 sheets, scale 1:1,000,000. 1974b, Preliminary geologic map of the southeast quadrant of Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-612, 2 sheets, scale 1:1,000,000. 1975a, Preliminary geologic map of southeastern Alaska: U.S. Geol. Survey Misc. Field Studies Map MF- 673, 2 sheets, scale 1:1,000,000. 1975b, Preliminary geologic map of the Alaska Pen insula and the Aleutian Islands: U.S. Geol. Survey Misc. Field Studies Map MF-674, 2 sheets, scale 1:1,000,000. Beikman, H. M., and Lathram, E. H., 1976, Preliminary geo logic map of northern Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-789, 2 sheets, scale 1:1,000,000.

B-110 Goodnews-Hagemeister Island quadrangles region By J. M. Hoare and W. L. Coonrad

162° 161° 160° 159°

w H* H* to :Wri^33&r.:::&r

r^ls.* *«*X»ii wj^t'-fi]''.ij^i»rf!SVv^^Ty*.V'f.".x'..'*'Afc* CORRELATION OF MAP UNITS SURFICIAL DEPOSITS .; ; ; QU;;- [ QUATERNARY SEDIM ENTA RY, VOLCANIC, INTRUSIVE ROCKS AND N1ETAKflORPHIC ROCKS $$$ | Pleistocene QUATERNARY QUATERNARY QTs [ Pleistocene or Pliocene np JFRTIARY m||]-Tn^ [ TERTIARY .*& : ? Lower Tertiary TERTIARY ^m I TERTIARY AND |rESI J CRETACEOUS } Upper Cretaceous v.KV/: ] (Maestrichian?) 1 Upper and Lower CRETACEOUS v K,k \ J Cretaceous u;:iiiu;j } mm kts HKcQH f Lower Cretaceous EKJvsr 1 Lower Cretaceous 1 . CRETACEOUS w J to Middle Jurassic 1 AND JURASSIC 1 Lower Upper CO XJKX J to Middle Jurassic JURASSIC &Ja'gdQ!S»v,tKx 1 JURASSIC AND ttflvsj \ Lower Jurassic

Wvs i**"^"3m*. IMzPz U , Lower Cretaceous . CRETACEOUS *^/*^?Pv to Lower Ordoviciari (?) TO ORDOVICIAN bOi <^

Wi mgj | PALEOZOIC(?) /P^.) PRECAMBRIAN s YMBOLS

. . Print art - - - Fault or fault zone T - -r - Thrust fault

FIGURE 47. Generalized geologic map of the Goodnews and Hagemeister Island quadrangles, southwestern Alaska. Ketchikan and Prince Rupert quadrangles By H. C. Berg, R. L. Elliott, J. G. Smith, and R. D. Koch

132° 130°

FIGURE 48. Generalized geologic map of Ketchikan and Prince Rupert quadrangles, southeastern Alaska. Scale 1:1,000,000 or 1 inch equals approximately 26 km. Base map from National Atlas of the United States, U.S. Geological Survey, 1970.

B-114 CORRELATION OF MAP UNITS

| QUATERNARY \QUATERNARY /AND TERTIARY Miocene TERTIARY Eocene TERTIARY OR ! CRETACEOUS Upper or JURASSIC 1 Middle Jurassic JURASSIC OR KteilVMI TRIASSIC J Upper Triassic TRIASSIC MESOZOIC OR PALEOZOIC \ Middle and /upper Paleozoic

PALEOZOIC OR OLDER Silurian or older

DESCRIPTION OF MAP UNITS

| UNCONSOLIDATED DEPOSITS, UNDIVIDED (Quaternary)

[ VOLCANIC ROCKS (Quaternary and Tertiary)

[ PLUTONIC ROCKS, UNDIVIDED (Miocene)

| PLUTONIC ROCKS, UNDIVIDED (Eocene)

I PLUTONIC ROCKS, UNDIVIDED (Tertiary or Cretaceous) GRAVINA ISLAND FORMATION AND UNNAMED CORRELATIVE ROCKS (Upper or Middle Jurassic) Ultramafic and other plutonic rocks

Metasedimentary rocks

Metavolcanic rocks

I TEXAS CREEK GRANODIORITE (Jurassic or Triassic)

I METAMORPHOSED VOLCANIC AND SEDIMENTARY ROCKS I (Jurassic or Triassic) I METAMORPHpSED SEDIMENTARY AND VOLCANIC ROCKS I (Upper Triassic) | PARAGNEISS AND AMPHIBOLITE (Mesozoic or Paleozoic)

I METAMORPHIC ROCKS, UNDIVIDED (Mesozoic or Paleozoic) I METAMORPHOSED SEDIMENTARY AND MINOR I VOLCANIC ROCKS (Middle and upper Paleozoic) ] FELSIC METAVOLCANIC ROCKS (Paleozoic or older)

I PLUTONIC ROCKS, CHIEFLY TRONDHJEMITE (Silurion or older) [ METAMORPHOSED SEDIMENTARY AND VOLCANIC ROCKS I (Silurian or older) SYMBOLS Contact. Approximately located; dotted where concealed

.... High-angle fault. Dashed where inferred; dotted where concealed

Thrust fault. Dashed where concealed. Sawteeth on upper plate

FIGURE 48. Continued.

* U.S. GOVERNMENT PRINTING OFFICE: 1978 789-107/25

B-115