Unit symbol: | Qs |
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Age range | Quaternary (1.806 to 0 Ma) |
Lithology: | Unconsolidated |
Group name: | Unconsolidated and poorly consolidated surficial deposits |
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. |
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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 |
Label | Qw0 |
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Description | Till, Brooks Lake, Kvichak [Ground moraine assigned Qclass of 1395] |
Geologic age | Late-Pleistocene |
Geologic setting | Unconsolidated |
Lithology | Form | Importance |
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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 |