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 Qtl
Unit name Lake terrace and beach ridge deposits
Description Prominent lacustrine terraces occur along much of Lake Iliamna. Multiple terraces on the north and west sides of the lake are at 40, 80, 100, and 130 above the present lake level, which is 47 feet. Other less well developed terraces also occur. The 40 and 80-foot terraces are best preserved and most continuous. They are generally 1,000 to 3,000 feet wide but locally as much as 5,000 feet wide
Lithology Unconsolidated

Correlated geologic units

Label Qmt
Description Marine terrace deposits
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Terrace, marine Major
Coarse-detrital < Unconsolidated Terrace, marine Indeterminate, major