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 Qat
Unit name Alaskan Glaciation, Tunnel Stade
Description A minor resurgence of the Alaskan Glaciation, dating from about 1200 years BP, these deposits are from alpine-valley glaciers that extended no more than .5 to 1.5 miles from the cirque headwall, except at Iliamna Volcano. In contrast to the earlier Tustumena Stade deposits, the Tunnel Stade deposits are more extensive in the north and less so in the southern part of the quadrangle. Most localities show end moraines of two advances. These deposits may represent the "Little Ice Age" in Alaska in part
Lithology Unconsolidated

Correlated geologic units

Label Qhg
Description Drift, neoglacial or so-called Alaskan glaciation
Geologic age Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Boulders < Coarse-detrital < Unconsolidated Glacial Major
Gravel < Coarse-detrital < Unconsolidated Glacial Indeterminate, major