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Unconsolidated surficial deposits, undivided

Unit symbol: Qs
Age range Quaternary (1.806 to 0 Ma)
Lithology: Unconsolidated
Group name: Unconsolidated and poorly consolidated surficial deposits
Unconsolidated, poorly to well-sorted, poorly to moderately well-stratified deposits; consist predominantly of alluvial, colluvial, marine, lacustrine, eolian, and swamp deposits. May include some glacial deposits. Also includes widespread glacial and periglacial deposits that consist of end, lateral, and ground moraine, outwash, rock glacier deposits, and other glacial and periglacial deposits as well as glacially scoured bedrock that may be covered with thin, glacially derived deposits. These glacial deposits are of Holocene and Pleistocene age and may include small areas of potentially latest Tertiary deposits. Map unit locally includes reworked volcanic debris as well as block and ash flows. On generalized map, shown as part of unit QTs

Source map information

Source map Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, 2009, Geologic map of the Yukon-Koyukuk basin, Alaska: U.S. Geological Survey Scientific Investigations Map SIM-2909, 26 p., 2 sheets, scale 1:500,000.
Symbol QTgl
Unit name Glacial and glaciolacustrine deposits.
Description Includes unsorted to poorly sorted till, outwash sand and gravel, alluvium, and eolian deposits. Along the southern edge of Brooks Range, unit is characterized by little-modified middle and late Pleistocene drift including prominent morainal ridges (shown by hachured lines), ice-contact features, and glaciolacustrine deposits. Further south, in Bettles, Hughes, Shungnak, and Selawik quadrangles, unit is composed of discontinuous areas of highly modified drift of Pliocene(?) and early Pleistocene age interspersed with alluvium and eolian deposits. Glacial erratics occur in hilly parts of the central Shungnak and Hughes quadrangles to an elevation of 600 meters. In the Bettles quadrangle the southern margin of the unit consists chiefly of lacustrine sediments deposited from a large proglacial lake. Glacial drift deposits bordering the southern edge of the Brooks Range and extending to the southern edge of the Selawik, Shungnak, Hughes, and Bettles quadrangles. Also includes drift from small Pleistocene alpine glaciers in the Melozitna, Tanana, and Medfra quadrangles
Lithology Unconsolidated

Correlated geologic units

Label Qm
Description Glacial deposits, undivided, of Holocene and/or Pleistocene age
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Glacial Major
Sand < Coarse-detrital < Unconsolidated Glacial Major
Silt < Fine-detrital < Unconsolidated Glacial Indeterminate, major
Boulders < Coarse-detrital < Unconsolidated Glacial Minor