Geologic Map of Alaska: Unconsolidated surficial deposits, undivided

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	Qbk
Unit name	Brooks Lake drift, Kvichak Stade
Description	Little modified, showing relatively fresh knob-and-kettle topography. Contains a heterogeneous assemblage of rock types indicating multiple sources of tributary glaciers. Ice-polished and striated erratics are common on surface of the moraines. Well-preserved lobate end moraines can be followed for many miles; recessional moraines are less preserved, being partially covered by glaciofluvial deposits. Kettle ponds are for most part undrained and retain the irregular shapes left by melting ice blocks, locally loess and vegetation are infilling the kettles. Some of the youngest moraines are locally heavily forested, whereas the oldest moraines at comparable elevations may be only tundra covered. Kvichak moraines are 5 to 20 beyond those of the Iliamna stade and 200 to 400 higher in elevation. Generally only one prominent end moraine though in the headwaters region of the Koktuli River, a complex system of recessional moraines is present
Lithology	Unconsolidated

Correlated geologic units

Label	Qw0
Description	Till, Brooks Lake, Kvichak [Ground moraine assigned Qclass of 1395]
Geologic age	Late-Pleistocene
Geologic setting	Unconsolidated

Lithology	Form	Importance
Gravel < Coarse-detrital < Unconsolidated	Glacial	Major
Boulders < Coarse-detrital < Unconsolidated	Glacial	Indeterminate, major
Sand < Coarse-detrital < Unconsolidated	Glacial	Indeterminate, major
Silt < Fine-detrital < Unconsolidated	Glacial	Indeterminate, major