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 Qs
Unit name Eolian and water-laid sand and silt sheets and stabilized dune fields
Description Sand and coarse silt. Extensive sheets of windblown and associated water-laid deposits are present in three separate locations: Baird Mountains, Ambler River, Selawik, and Shungnak quadrangles: Modified and partly dissected sheets of mixed windblown and water-laid deposits bordering the south edge of the Brooks Range. Kateel River and Melozitna quadrangles: Sheet-like dune fields of windblown sand mantling alluvial silt deposits of the Koyukuk Flats. Dunes are much modified and locally dissected by stream erosion. Orientation of parabolic dunes suggest deposition by prevailing northeast winds. Ruby quadrangle: A broad sheet of wind-blown silt and sand that extends over a wide area in the Nowitna Lowland south of the Yukon River. The sheet is much modified by stream erosion, but parabolic and longitudinal dune forms can be recognized in aerial photographs and on 1:63.360-scale topographic maps. The dune forms have a strong northeast-southwest orientation and suggest deposition by prevailing northeast winds. Small isolated sand sheets also occur in Bettles, Hughes, and Medfra quadrangles
Lithology Unconsolidated

Correlated geologic units

Label Qda
Description Active dune deposits
Geologic age Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Sand < Coarse-detrital < Unconsolidated Eolian Indeterminate, major
Silt < Fine-detrital < Unconsolidated Eolian Indeterminate, major