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 Qrg
Unit name Rock glaciers
Description Rock glaciers are uncommon in the Iliamna quadrangle. Those present are all apparently inactive and have crescent-like ridges and furrows bowing downslope and commonly have deep conical thaw pits and longitudinal ridges on the surface. All mapped rock glaciers have a distinct wall of debris facing upslope, with a pit between the rock glaciers and the cirque headwall. All are small, no more than one half mile in length in small cirques. No identifiable Tunnel Stade moraines are associated with these features, suggesting there may not have been enough ice during the Tunnel Stade to form a true glacier.
Lithology Unconsolidated

Correlated geologic units

Label Qrg
Description Rock glacier deposits
Geologic age Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Boulders < Coarse-detrital < Unconsolidated Glacial, rock glacier Major