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 Detterman, R.L., Wilson, F.H., Yount, M.E., and Miller, T.P., 1987, Quaternary geologic map of the Ugashik, Bristol Bay and western part of Karluk quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1801, 1 sheet, scale 1:250,000.
Symbol al
Unit name Alluvium, alluvial deposits
Description Ranges from poorly sorted and poorly stratified, coarse, angular fragments near head of valleys to moderately well-sorted, well-rounded, and stratified sand and fine gravel on the coastal plain. Deposits along streams draining volcanoes consist mainly of pumice lapilli; streams cutting glacial moraines contain many large rock fragments. Includes both active and inactive deposits. Inactive deposits commonly vegetated; may include low terrace gravels
Lithology Unconsolidated

Correlated geologic units

Label Qa
Description Alluvium
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Bed Major
Sand < Coarse-detrital < Unconsolidated Bed Major
Coarse-detrital < Unconsolidated Bed Indeterminate, major
Silt < Fine-detrital < Unconsolidated Bed Indeterminate, major
Peat < Unconsolidated Bed Indeterminate, major