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 Patton, W.W., Jr., and Moll-Stalcup, E.J., 2000, Geologic map of the Nulato quadrangle, west-central Alaska: U.S. Geological Survey Geologic Investigations Series I-2677, 41 p., 1 sheet, scale 1:250,000.
Symbol Qhs
Unit name High-terraces and slope deposits
Description Light-gray and grayish-orange micaceous silt deposits. Subordinate lenses of sand and peat. Deposits form a broad terrace 10 to 100 m above the floodplain of the Koyukuk Flats and extend as much as 250 m up the slopes of the bedrocks hills surrounding the Flats. Terrace deposits characterized by thermokarst topography marked by many small lakes. Unit also forms terrace and slope deposits along streams that drain bedrock uplands and locally include coarse-grained colluvial and fan deposits.
Lithology Unconsolidated

Correlated geologic units

Label Qt
Description Terrace deposits
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Alluvial Major
Sand < Coarse-detrital < Unconsolidated Terrace, stream Major
Silt < Fine-detrital < Unconsolidated Terrace, stream Major
Boulders < Coarse-detrital < Unconsolidated Terrace, stream Indeterminate, major