Sedimentary rocks of Doonerak Window

Unit symbol: SCs
Age range Silurian to Cambrian (541 to 419.2 Ma)
Lithology: Sedimentary
Group name: Older rock units of the Doonerak Window
Black phyllite and metasiltstone; minor quartzite; graywacke; red, green, and purple phyllite; green chert; siliceous metatuff; lenses of brown dolomite and thin limestone beds cut by abundant mafic sills. Middle Cambrian microfossils, brachiopods and trilobites, Ordovician conodonts, and Silurian graptolites and conodonts have all been recovered from the sedimentary rocks (Dutro and others, 1984; Repetski and others, 1987). Unit is metamorphosed to lower greenschist and prehnite-pumpellyite facies (Dillon and others, 1986). Mafic dikes cutting unit have yielded K/Ar ages on hornblende of 380.5±17 and 395±12 Ma (Dutro and others, 1976; ages recalculated using constants of Steiger and Jager, 1977), approximately Middle Devonian

Source map information

Source map Till, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, 2008, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Open-File Report 2008-1149, 88 p., 2 sheets, scale 1:500,000.
Symbol SCvs
Unit name Volcanic and sedimentary rocks
Description Volcanic rocks, volcaniclastic rocks, and clastic sedimentary rocks exposed in the core of the Doonerak antiform, northeast Wiseman quadrangle. The unit can be divided into at least two lithologic sequences, one dominated by volcanic rocks, the other by sedimentary rocks. This unit is part of the Doonerak antiform.
Lithology Igneous

Correlated geologic units

Label SCvs
Description Volcanic and sedimentary rocks, Doonerak antiform
Geologic age Cambrian to Silurian
Geologic setting Extrusive
Lithology Form Importance
Volcanic < Igneous Major
Clastic < Sedimentary Bed Minor