 Figure 1. False-color composite Landsat image of northern Alaska showing quadrangles discussed in text and approximate outline of the Colville basin (dashed white line). New geologic maps are being prepared jointly by the U.S. Geological Survey and the Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys and Division of Oil and Gas for many of the quadrangles. Boundaries for the National Petroleum Reserve in Alaska (NPRA), the Arctic National Wildlife Refuge (ANWR), and the ANWR 1002 area are shown in green, dotted lines. See Bird and Houseknecht (2001, 2002) for additional information regarding ANWR and NPRA, including explanation of ANWR 1002 area. Area outlined in white is shown in greater detail in figure 2. Image compiled by U.S. Geological Survey, Earth Resources Observation Systems (EROS) Data Center, Sioux Falls, S. Dak. PRINT/VIEW a high-quality PDF image |
 Figure 2. False-color composite Landsat image of the Umiat, Sagavanirktok, Chandler Lake, and Philip Smith Mountains quadrangles, northern Alaska, showing township-range grid, streams, and other features mentioned in text and figure captions. Recent geologic investigations in these quadrangles provided the basis for revisions of Cretaceous and Tertiary stratigraphic nomenclature presented in this paper. TAPS, Trans-Alaska Pipeline System; numbered white dots, TAPS pump stations with pump station number; AC, Autumn Creek; DC, Desolation Creek; MC, May Creek; TC, Torok Creek. Image compiled by U.S. Geological Survey, Earth Resources Observation Systems (EROS) Data Center, Sioux Falls, S. Dak. PRINT/VIEW a high-quality PDF image |
 Figure 3. Chronostratigraphic column for the Colville basin, northern Alaska, showing revised stratigraphic nomenclature and ages of units discussed in this paper (in color); laterally correlative and overlying and underlying units not discussed in this paper are uncolored in diagram. Abbreviations or symbols are as follows: <?>, uncertain relationship; cs*, cobblestone sandstone of Fortress Mountain Formation (informal unit of Mull and others, 2003); ms**, manganiferous shale unit (informal term); Kemik***, Kemik Sandstone (formation) as revised by Molenaar and others (1987); Fm., Formation; Mtn., Mountain; LCU, Lower Cretaceous unconformity. Geologic time scale from Gradstein and Ogg (1996). PRINT/VIEW a high-quality PDF image |
 Figure 4. Chart illustrating relationship between former stratigraphic nomenclature and revised stratigraphic nomenclature as proposed in this paper for the Colville basin, northern Alaska. Stratigraphic columns in red box summarize lateral variation in previous stratigraphic nomenclature for Cretaceous strata from west to east across the western and central foothills of the Brooks Range, as presented by Chapman and others (1964). Colored columns on both sides of chart show revised stratigraphic nomenclature proposed in this paper. Colors extending across chart show correlation of newly revised nomenclature with previous nomenclature. Note that age and stratigraphic nomenclature indicated by gray have been revised; these rocks are now considered Early Cretaceous in age and assigned to the Nanushuk Formation. Quaternary units are not considered in this paper. PRINT/VIEW a high-quality PDF image |
 Figure 5. Sandstone in turbidite channel incised into interbedded mudstone and thin turbidite sandstones of Torok Formation on Heather Creek, Killik River quadrangle. Height of bluff is approximately 100 ft. View to north. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 6. Poorly sorted pebble-cobble conglomerate in debris-flow deposit within Torok Formation, Autumn Creek, Chandler Lake quadrangle. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 7. Relatively incompetent folded and faulted mudstone in Torok Formation, Autumn Creek, Chandler Lake quadrangle. Exposure is about 25 ft high. View to east. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 8. Slope Mountain, a prominent landmark in northwestern Philip Smith Mountains quadrangle near Mile 305 of the Dalton Highway. Upper part of mountain consists of dominantly nonmarine sandstone, conglomerate, and coal of upper Nanushuk Formation overlying dominantly marine sandstone of lower Nanushuk, which prograded over outer shelf silty mudstones of Torok Formation exposed in lowermost slope. Note Trans-Alaska Pipeline at base of mountain. View to northwest. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 9. Nanushuk Formation on south flank of Arc Mountain anticline at Nanushuk River, eastern Chandler Lake quadrangle. Lowland, tundra-covered core of anticline is underlain by mudstone of Torok Formation as shown in left-center of photograph. Marine sandstones of lower Nanushuk form resistant ridge on south flank of anticline; discontinuous ledges of dominantly nonmarine sandstone and conglomerate of upper Nanushuk are exposed to the right in axis of Arc Mountain syncline. View to east. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 10. Resistant, crossbedded sandstone and conglomerate in characteristic exposure of upper part of Nanushuk Formation west of the Anaktuvuk River, Chandler Lake quadrangle. Exposure is about 25 ft thick. View to west. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 11. Crossbedded sandstone in upper part of lower Nanushuk Formation on Slope Mountain, Philip Smith Mountains quadrangle. Predominance of planar crossbedding and local occurrence of herringbone crossbedding (above arrowhead) suggest deposition in a shoreface system influenced by tidal currents (perhaps a tidal inlet on a barred coast). View to north. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 12. Exposure of Seabee Formation overlain by Tuluvak Formation along Colville River at base of Umiat Mountain, central Umiat quadrangle. The Seabee Formation extends from river level more than halfway up to prominent sandstone at base of Tuluvak Formation; contact is shown by yellow dashed line. Note yellow tuff beds within Seabee. Bluff has approximately 400 ft of relief. View to north. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 13. Seabee Formation at base of Umiat Mountain showing predominant mudstone lithology with yellow tuff interbeds. Hammer for scale. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 14. Bentonitic shale with large concretions in upper part of Seabee Formation, east fork of Tuluga River. View to west. Largest concretions are approximately 4 ft in diameter. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 15. Marine or marginal marine sandstone and pea-gravel conglomerate in Tuluvak Formation in May Creek syncline, north of May Creek, eastern Chandler Lake quadrangle. Ledge-forming conglomerate is about 20 ft thick. View to north. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 16. Discontinuous, resistant ledge of Tuluvak Formation on north flank of Big Bend anticline, south side of Outpost Mountain, southern Umiat quadrangle. View to north. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 17. Fluvial conglomerate of Tuluvak Formation near the Anaktuvuk River in the southern Umiat quadrangle. Conglomerate ledge is about 25 ft thick. View to east. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 18. Crossbedded quartz- and chert-pebble conglomerate and sandstone in Tuluvak Formation at same outcrop shown in figure 17. A sandstone sample from this locality has measured 18 percent porosity and 812 millidarcies (mD) permeability (data from C.G. Mull). Photograph by C.G. Mull PRINT/VIEW a high-quality PDF image |
 Figure 19. Bioturbated marine sandstone in Tuluvak Formation along west side of Nanushuk River on south side of Rooftop Ridge, Chandler Lake quadrangle. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 20. Oil-stained sandstone in Tuluvak Formation, north flank of Big Bend anticline near Outpost Mountain. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 21. Exposure of upper part of Schrader Bluff Formation at Shivugak Bluff, along Colville River east of Umiat. Strata consist of resistant sandstones, mostly of shallow-marine origin, interbedded with mudstone, tuffaceous sandstone, tuff, and bentonite. Bluff has approximately 300 ft of relief. View to north. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 22. Tuff beds intercalated with tuffaceous mudstone and bentonite in upper part of Schrader Bluff Formation at Shivugak Bluff. View to northeast. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 23. Shallow-marine sandstone in upper part of Schrader Bluff Formation at Shivugak Bluff showing lag of marine shells in a hummocky cross-stratified facies. White ovals just beneath pen are likely Schaubcylindrichnus trace fossils. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 24. Upper part of Shivugak Bluff showing section that includes the contact between the Schrader Bluff Formation and the overlying Prince Creek Formation (yellow dashed line). The prominent sandstone shown in middle of photograph and underlying rocks are predominantly marine, whereas all overlying rocks are predominantly nonmarine; thus, the top of that sandstone represents the formation contact at this locality. The prominent marine sandstone shown in middle of photograph is approximately 25 ft thick, and the fluvial sandstone at top of bluff is approximately 40 ft thick. View to east with the Colville River in background. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 25. Nonmarine channel sandstone incised into shallow-marine sandstones in Schrader Bluff Formation at Shivugak Bluff. Yellow dashed line marks approximate base of incised channel. Exposure is about 30 ft high. View to north. Photograph by D.W. Houseknecht PRINT/VIEW a high-quality PDF image |
 Figure 26. Exposures of nearly horizontal Prince Creek Formation forming bluff on west side of the Colville River near confluence with the Anaktuvuk River, Umiat quadrangle. Light-colored strata are mostly nonmarine sandstones, and dark-colored strata are carbonaceous mudstones and coal. Bluff has approximately 300 ft of relief. View to north. These strata are typical exposures for the lower part of the Prince Creek Formation. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 27. Exposure of Prince Creek Formation along west side of the Colville River, just north of confluence with the Anaktuvuk River. Light-colored, nonmarine sandstones are interbedded with dark-colored coal and carbonaceous mudstone. Note low-angle bedding (gentle dip to right) in sandstone just beneath thickest coal; this is accretionary bedding in a meandering fluvial (point-bar) deposit. Bluff has approximately 300 ft of relief. View to west. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 28. Silty mudstone, coal, and sandstone in upper part of the Prince Creek Formation at Sagwon Bluffs, central Sagavanirktok quadrangle. Note thrust fault offsetting prominent coal bed. View to west. Photograph by Tim Collett, U.S. Geological Survey. PRINT/VIEW a high-quality PDF image |
 Figure 29. Conglomerate in Prince Creek Formation along Colville River in northern Umiat quadrangle. Ironstone clasts are common and appear reddish brown. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 30. Medium- to coarse-grained, pebbly, crossbedded sandstone in Prince Creek Formation at Shivugak Bluff. This facies is inferred to be of braided fluvial origin. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 31. Sandstones and conglomerates of Sagwon Member of Sagavanirktok Formation at VABM Gard on northwest side of Sagwon Bluffs, central Sagavanirktok quadrangle, overlying the Prince Creek Formation in lower slopes. Approximate contact is shown by yellow dashed line. The White Hills are visible on horizon. View to west. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 32. Poorly consolidated conglomerates at base of Sagwon Member of Sagavanirktok Formation at VABM Gard on west side of Sagavanirktok River. Contact with underlying Prince Creek Formation is concealed beneath gravel talus (approximate location shown by yellow dashed line). View to north. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 33. Lower part of Sagwon Member of Sagavanirktok Formation, at north end of Sagwon Bluffs on east side of the Sagavanirktok River, dipping regionally northward beneath the Arctic Coastal Plain. View to north. This is a reference section for the lower part of the Sagwon Member. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 34. Cliff-forming sandstone and conglomerate in lower part of Sagwon Member of Sagavanirktok Formation on east side of the Sagavanirktok River; exposed section is about 100 ft thick. View to northeast. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 35. Closeup view of quartz-rich sandstone, with quartz- and chert-pebble lag, overlying coal in Sagwon Member of Sagavanirktok Formation. This is the same location shown in figure 33. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 36. Oxidized clinker zone in coal-bearing upper part of Sagwon Member of Sagavanirktok Formation in southeast part of the White Hills. View to south. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 37. White conglomerate cap of basal White Hills Member of Sagavanirktok Formation, at southwest end of the White Hills, western Sagavanirktok quadrangle. View to north. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 38. Poorly consolidated sandstone and conglomerate yield the typical rounded hillsides pattern of the White Hills Member of Sagavanirktok Formation. This photograph shows one of the few good outcrops in the area in an unnamed stream drainage on northwest side of the White Hills. This locality is the type section for the basal part of the White Hills Member. Relief from streambed to hilltop is about 300 ft. View to east. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 39. Crossbedded fluvial sandstones and conglomerates in basal part of White Hills Member of Sagavanirktok Formation along the Toolik River. View to north. This locality is a reference section for the basal part of the White Hills Member. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 40. Bluff along east bank of Sagavanirktok River (foreground) and southern end of Franklin Bluffs (background), showing contrast between Franklin Bluffs Member of Sagavanirktok Formation (background) and brown-weathering, lignite-bearing silty mudstone of upper part of White Hills Member (foreground). The contact between the two members is concealed beneath the gentle slope in the middle of the photograph as shown by yellow dashed line. View to northeast. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 41. Crossbedded sandstone and conglomerate in basal part of White Hills Member of Sagavanirktok Formation in an unnamed stream drainage on northwest side of the White Hills. This photograph was taken at the outcrop shown in figure 38. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 42. Poorly consolidated, crossbedded sandstone and conglomerate of the White Hills Member of Sagavanirktok Formation in unnamed stream drainage on northwest side of the White Hills. This photograph was taken at the outcrop shown in figures 38 and 41. View to northeast. Photograph by D.W. Houseknecht. PRINT/VIEW a high-quality PDF image |
 Figure 43. South end of Franklin Bluffs, Sagavanirktok quadrangle, showing white conglomerate cap and underlying sandstones of Franklin Bluffs Member of Sagavanirktok Formation. Contact between Franklin Bluffs Member and underlying White Hills Member lies just below river level. View to southeast. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 44. White conglomerate cap and underlying pink-weathering sandstones of Franklin Bluffs Member of Sagavanirktok Formation at Franklin Bluffs. View to north. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 45. Wireline log of Mobil West Kadleroshilik Unit #1 well showing correlation of lower Tertiary stratigraphic nomenclature in Franklin Bluffs area with subsurface nomenclature to the northeast. GR, gamma ray log; Res, resistivity log. PRINT/VIEW a high-quality PDF image |
 Figure 46. Brown-weathering, sandy siltstones in lower part of Franklin Bluffs Member of Sagavanirktok Formation at Franklin Bluffs. Dinoflagellate cysts from this facies indicate a nearshore marine or estuarine environment of deposition (Frederiksen and others, 2002). Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 47. Poorly consolidated, crossbedded fluvial sandstones in Franklin Bluffs Member of Sagavanirktok Formation at Franklin Bluffs. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
 Figure 48. Pebble lag in crossbedded sandstone in Franklin Bluffs Member of Sagavanirktok Formation at Franklin Bluffs. Photograph by C.G. Mull. PRINT/VIEW a high-quality PDF image |
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