Geologic Map of Alaska: Unconsolidated surficial deposits, undivided

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	Pewe, T.L., Wahrhaftig, Clyde, and Weber, Florence, 1966, Geologic map of the Fairbanks quadrangle, Alaska: U.S. Geological Survey, Miscellaneous Investigations I-455, 5 pages, 1 sheet, scale 1:250,000.
Symbol	Qsu
Unit name	Perennially frozen silt, undifferentiated
Description	Massive, homogeneous unconsolidated, well-sorted silt of eolian origin containing less than 10% clay, locally rich in organic silt and larger organic fragments. Inorganic components are angular grains of quartz, feldspar, and mica, locally cemented by iron oxides. It is buff to brown or gray, locally mottled. Organic silt is brown to grayish black
Lithology	Unconsolidated

Correlated geologic units

Label	Qsu
Description	Silt deposits, undifferentiated
Geologic age	Pleistocene to Holocene
Geologic setting	Unconsolidated

Lithology	Form	Importance
Silt < Fine-detrital < Unconsolidated	Eolian, Loess	Major
Sand < Coarse-detrital < Unconsolidated	Alluvial	Indeterminate, major
Peat < Unconsolidated	Swamp	Indeterminate, major