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 Qab
Unit name Abandoned flood-plain alluvium
Description Well-stratified layers and lenses of unconsolidated gray silt, sand, pebbles, cobbles, and boulders. Occurs in two facies: 1) coarse gravelly alluvium and 2) silty alluvium containing 95% silt and 5% sand.
Lithology Unconsolidated

Correlated geologic units

Label Qac
Description Abandoned channel deposits
Geologic age Pleistocene
Geologic setting Unconsolidated
Lithology Form Importance
Sand < Coarse-detrital < Unconsolidated Alluvial Major
Silt < Fine-detrital < Unconsolidated Alluvial Indeterminate, major