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 Weber, F.R., 1961, Reconnaissance engineering geology for the selection of highway route from Talkeetna to McGrath, Alaska: U.S. Geological Survey Open-File Report 61-169, 2 sheets, scale 1:250,000.
Symbol 13c,f
Unit name Ground moraine, channeled, covering well consolidated bedded rocks
Description Deposit of unsorted, unstratified boulders, pebbles, sand, silt, and a small amount of clay, up to 250 feet thick. Locally, boulders exposed on surface may exceed 5 feet in diameter. Components vary greatly in composition depending on lithologies present in source areas -- granitic rocks volcanic rocks, argillite, chert, limestone, quartz, quartzite, graywacke, slate -- generally the most resistant rocks persist. Many small boulders and pebbles are well-rounded. Till is gray and covered in most places with 2 to 5 feet of reddish clay, silt, and sand. Five to 50 feet of thick veneer of ground moraine overlying various types of bedrock. Locally, this veneer includes loess, colluvium, or rarely peat. Components of this till may be larger and more angular than unit 13 and may be made up in large part of the immediately adjacent bedrock.
Lithology Unconsolidated

Correlated geologic units

Label Qwu
Description Drift, undivided, Late Wisconsin-age glaciations (Aleknagik, Brooks Lake, Farewell II, McKinley Park, Riley Creek, Donnelly, Takomahto Lake, and others)
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