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 Qbm
Unit name Brooks Lake terraced and modified morainal deposits
Description Brooks Lake terraced and modified morainal deposits. Originally deposited as ground moraine, but subsequently modified by streams emerging from later glaciers. In many places, deposits are adjacent to outwash plains or hanging deltas and may be partially covered by these deposits. A thin layer of loess, derived from braided stream channels in front of glaciers overlies the deposit. Terraces created by runoff streams issuing from glaciers.
Lithology Unconsolidated

Correlated geologic units

Label Qwo
Description Outwash deposits, late Wisconsin-age Glaciations
Geologic age Late-Pleistocene
Geologic setting Unconsolidated
Lithology Form Importance
Sand < Coarse-detrital < Unconsolidated Glacial, outwash Major
Gravel < Coarse-detrital < Unconsolidated Glacial, outwash Indeterminate, major
Silt < Fine-detrital < Unconsolidated Glacial, outwash Minor