Prepared in cooperation with the National Park Service Surficial Geologic Map of the Gates of the Arctic National Park and Preserve, Alaska By Thomas D. Hamilton and Keith A. Labay Pamphlet to accompany Scientific Investigations Map 3125 Glaciers and rugged alpine topography of Arrigetch Peaks (Survey Pass quadrangle). Photo by T.D. Hamilton, August 30, 1979 2011 U.S. Department of the Interior U.S. Geological Survey This page intentionally left blank Contents Introduction ....................................................................................................................................................1 Regional Setting ............................................................................................................................................1 Previous Studies ...........................................................................................................................................3 The Glacial Record .......................................................................................................................................4 Quaternary Tectonics and Drainage Evolution ........................................................................................5 Alpine Features ..............................................................................................................................................6 Acknowledgments .........................................................................................................................................7 Description of Map Units ..............................................................................................................................8 Surficial Deposits .................................................................................................................................8 Fan Deposits ................................................................................................................................8 Alluvium ........................................................................................................................................8 Terrace Deposits .........................................................................................................................9 Other Gravel Deposits ................................................................................................................9 Colluvial Deposits ......................................................................................................................10 Sand, Silt, and Organic Deposits ............................................................................................11 Lacustrine and Glaciolacustrine Deposits ...........................................................................12 Glacial Drift and Ice-Contact Gravel .....................................................................................13 Late Holocene Glaciation (Neoglaciation) ..................................................................13 Itkillik Glaciation ...............................................................................................................13 Sagavanirktok River Glaciation .....................................................................................14 Anaktuvuk River Glaciation ............................................................................................14 Gunsight Mountain Glacial Interval ..............................................................................15 Glacial Outwash and Inwash ..................................................................................................15 Bedrock Surface Forms ....................................................................................................................16 References Cited .........................................................................................................................................16 Figures Figure 1. Northern Alaska, showing locations of Gates of the Arctic National Park and Preserve, and Noatak National Preserve .......................................................................................................1 Figure 2. Central Brooks Range, showing map area and areas of previously published surficial and bedrock geologic mapping .....................................................................................................2 Figure 3. Shaded-relief map of central Brooks Range and adjoining foothills ...................................3 Tables Table 1. Glacial advances in the central Brooks Range (modified from Hamilton, 2009) ..................4 Table 2. Physical characteristics of Pleistocene drifts, central Brooks Range (where differentiated, southern valleys shown in brackets). From Hamilton, 1994 .........................6 i This page intentionally left blank Introduction (1) aerial and surface observations of morphology and compo- sition of unconsolidated deposits, (2) tracing the distribution and interrelation of terraces, abandoned meltwater channels, The Gates of the Arctic National Park and Preserve moraines, abandoned lake beds, and other landforms, (3) strati- (GAAR) is centered over the central Brooks Range of north- graphic study of exposures along lake shores and river bluffs, ern Alaska (fig. 1). To the west, it abuts the Noatak National (4) examination of sediments and soil profiles in auger borings Preserve; its eastern boundary is the transportation corridor and test pits, and exposed in roadcuts and placer workings, and occupied by the Dalton Highway and the Alyeska Pipeline. (5) analysis of previously published geologic maps and reports. The GAAR extends northward beyond the northern flank of the The map units used for those maps and employed in the present Brooks Range into the southern Arctic Foothills (Wahrhaftig, compilation are defined on the basis of their physical character, 1965). Its southern boundary lies beyond the south flank of the genesis, and age. Relative and absolute ages of the map units Brooks Range within foothills and depositional basins of inte- were determined from their geographic locations and from their rior Alaska. The accompanying surficial geologic map covers stratigraphic positions and radiocarbon ages (see reports listed all of the GAAR with the addition of a 10-km (6.2-mi) belt or on figure 2 for radiocarbon age data). “buffer zone” beyond its boundaries. A narrower (5-km) buffer zone is employed where the GAAR extends farthest north and south of the Brooks Range, in the north-central and southwest- ern parts of the map area, respectively. Regional Setting The surfical geologic map incorporates parts of ten surficial geologic maps previously published at 1:250,000 scale (fig. 2). The central Brooks Range is dominated by rugged, glacier- In addition, a small part of the buffer zone mapped in the south- abraded peaks and ridges that rise to 1,800-2,100 m (6,000- west corner of the map area was compiled from unpublished 7,000 ft) altitude and are indented by deep cirque basins. Broad, surficial geologic mapping of the Shungnak 1:250,000-scale glacier-carved troughs extend north and south to both flanks of quadrangle. Each of those individual maps was developed from the range and, in the westernmost part of the map area, trend 168° 162° 156° 150° 144° C h u k c h i Beaufort Sea 70° S e a CANADA C o v e r l v i l l e R i A R L L S C H I H i g h w a y T I C F O O T 68° NOAT N o a t a k R i v e r B G AAR N G E R O R A O KS u k n ob R o K i t v e l r r a e r e v D i v R 66° R i o n k u k ku Y u y o K 0 100 200 300 400 500 Kilometers 0 50 100 150 200 250 Miles Figure 1. Northern Alaska, showing major drainages and locations of Gates of the Arctic National Park and Pre- serve (GAAR) and Noatak National Preserve (NOAT). 1 159° 156° 153° 150° 147° 69° HOWARD PASS KILLIK RIVER CHANDLER LAKE PHILIP SMITH MTS Hamilton, 1984a, 2009 Hamilton, 1980c,1982a Hamilton, 1979c, 1980a Hamilton, 1978b, 1979b Mull and others, 1994 Kelley, 1990 Brosgé and others, 1979 68° AMBLER RIVER SURVEY PASS CHANDALAR Hamilton, 1984b, WISEMAN Hamilton, 1981a, Hamilton Hamilton, 1978a, 1979a 2009 Hamilton, 1979d, 1980b and Brubaker, 1983 Dillon and others, 1986 Brosgé and Reiser, 1964 Mayfield and Nelson and Grybeck, 1980 Tailleur, 1978 67° SHUNGNAK Hamilton, unpublished BETTLES Patton and others, 1968 Hamilton, 2002b Patton and Miller, 1973 HUGHES Hamilton, 2002a Patton and Miller, 1966 66° 0 50 100 150 200 250 300 Kilometers 0 255075 100 125 150 Miles Figure 2. Central Brooks Range, showing Gates of the Arctic National Park and Preserve (in green) and its buf- fer zone (in gray). Gray stippled pattern designates park inholdings. Area within the buffer zone covers parts of eleven 1:250,000-scale quadrangles. The first reference cited beneath each quadrangle name is the surficial geo- logic map from which the park map was compiled. The second reference listed for eight of the quadrangles is a compilation of stratigraphic sections and radiocarbon age determinations. Listed in italic is the bedrock geologic map available for ten of the quadrangles. westward forming the upper Noatak River valley. The east- snowfall decrease northward and eastward across the map area west-trending Arctic Foothills (fig. 1) north of the range are (Ellis and others, 1981). This gradient is reflected in depth of dissected by north-flowing drainages and by broad gaps carved winter snow cover and in the distribution of modern and Pleis- by former glaciers. The major valleys followed by those north- tocene glaciers. flowing