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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 Riehle, J.R., and Detterman, R.L., 1993, Quaternary geologic map of the Mount Katmai quadrangle and adjacent parts of the Naknek and Afognak quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-2032, 1 sheet, scale 1:250,000.
Symbol al
Unit name Alluvium
Description Varies from poorly sorted and crudely stratified deposits of coarse angular fragments near valley heads to well-sorted and stratified deposits of sand and pebbles in lowlands. Locally includes boulders where streams have cut through glacial moraines. Unit includes both active and vegetated inactive deposits; unit may include older outwash and (or) terrace deposits too small to show separately.
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