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 Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1807, pamphlet, 27 p., scale 1:250,000.
Symbol Qu
Unit name Glacial, glacial-marine, alluvial, and talus deposits, undivided
Description Unconsolidated deposits of poorly sorted clay, silt, sand, gravel, and boulders locally cover bedrock, sometimes to depths of many meters, throughout the map area. Glacial drift, till, and moraine are partly reworked. A glacial-marine terrace deposit, approximately 3-m-thick but too small to show on the map occurs at an elevation of about 25 m about 1 km northwest of the head of Dall Bay on Gravina Island (Chapin, 1918, p. 99; Berg, 1973, p. 35). It consists of stratified glacial till, gravel, and blue clay and contains Quaternary marine fossils (Berg and Cruz. 1982, No. 37). The unconsolidated deposit mapped at an elevation of about 75 rn west of Blank Inlet on Gravina Island may also be a marine terrace deposit that correlates with the fossiliferous deposit northwest of Dall Bay
Lithology Unconsolidated

Correlated geologic units

Label Qs
Description Surficial deposits, undifferentiated
Geologic age Pleistocene to Holocene
Geologic setting Unconsolidated
Lithology Form Importance
Gravel < Coarse-detrital < Unconsolidated Bed Indeterminate, major
Sand < Coarse-detrital < Unconsolidated Bed Indeterminate, major
Clay < Fine-detrital < Unconsolidated Bed Indeterminate, major
Silt < Fine-detrital < Unconsolidated Bed Indeterminate, major
Peat < Unconsolidated Bed Indeterminate, major