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., and Reed, B.L., 1973, Surficial deposits of the Iliamna quadrangle, Alaska: U.S. Geological Survey Bulletin 1368-A, 64 p., 1 plate, scale 1:250,000.
Symbol Qts
Unit name Stream terrace deposits
Description Crudely stratified deposits of gravel and sand having level or gently sloping upper surfaces form terraces found along virtually all streams in the quadrangle. Many streams show a complex series of multiple terraces and the deposits that form the terraces are locally more than 100 feet thick.. Consist mainly of poorly stratified, well-round pebbles and cobbles having interbeds and lenses of sand and silt
Lithology Unconsolidated

Correlated geologic units

Label Qt
Description Terrace deposits
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Alluvial Major
Sand < Coarse-detrital < Unconsolidated Terrace, stream Major
Silt < Fine-detrital < Unconsolidated Terrace, stream Major
Boulders < Coarse-detrital < Unconsolidated Terrace, stream Indeterminate, major