| Summary: | Glaciers of middle and late Pleistocene age flowed into the upper Kuparuk map area from the west, east, and south. Glacial deposits are assigned to the Sagavanirktok River (middle Pleistocene) and Itkillik I and II (late Pleistocene) glaciations of the central Brooks Range glacial succession. During the initial (maximum) advance of Sagavanirktok River age, large valley glaciers flowed north along the Itkillik, Sagavanirktok, and Kuparuk River drainages. Moraines are massive but subdued, with heavy loess cover and broad flanks smoothed by solifluction. A subsequent less extensive advance of Sagavanirktok River age overflowed into the upper Kuparuk drainage from the west and south, forming moraines and outwash remnants that are intermediate in appearance between those of the maximum advance and the subsequent Itkillik moraine succession. Itkillik I glaciers abutted divides west, east, and south of the upper Kuparuk drainage, but overflowed those divides only locally. Their moraines are modified by weathering and erosion, but on a much smaller scale than deposits of the Sagavaniktok River glaciations. Crests are slightly flattened, with loess and vegetation cover locally absent; kettle lakes are common. The subsequent Itkillik II advance, which dates between about 25 and 11.5 ka (thousand 14C years B.P.), is marked by little-modified moraines with stony crests and steep flanks. Glacial flow patterns were generally similar to those of present-day river drainage. Two major advances of Itkillik II age took place between about 25 and 17 ka, forming extensive ice-stagnation features around Toolik Lake. A subsequent readvance is dated between about 12.8 and 11.4 ka at its type locality near the east end of Atigun Gorge. Surficial deposits of Holocene age, although less extensive than those of Pleistocene glaciation, are locally significant. They include alluvial terraces along the Sagavanirktok River, fan deposits at the mouth of the Atigun River, raised beaches and fan-delta deposits around Galbraith Lake, and local ...
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