Etivluk Group, undivided

Unit symbol: JIPe
Age range Middle Jurassic to Pennsylvanian (323.2 to 168.3 Ma)
Lithology: Sedimentary
Group name: Etivluk Group, undivided
Includes Otuk and Siksikpuk Formations and Imnaitchiak Chert; consists of maroon, red, green, gray, black, and variegated chert and siliceous argillite, minor maroon calcareous siltstone and argillite, and rare maroon or gray limestone lenses (Karl and others, 1989a; Mayfield and others, 1987). Original definition suggested Etivluk Group is present only on allochthonous sheets in the Brooks Range, and not present on autochthonous rock units (Mull and others, 1982). Locally, the Otuk and Siksikpuk Formations are mapped separately as units JTro and TrIPeg

Source map information

Source map Ellersieck, Inyo, Curtis, S.M., Mayfield, C.F., and Tailleur, I.L., 1990, Reconnaissance geologic map of the De Long Mountains A-2 and B-2 quadrangles and part of the C-2 quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1931, 2 sheets, scale 1:63,360.
Symbol JIPe1
Unit name Etivluk Group
Description Gray chert with minor amounts of shale; weathers brown, yellow, gray, green, and maroon. Consists of the Siksikpuk and Otuk Formations. Part of the Brooks Range allochthon, Key Creek sequence.
Lithology Sedimentary

Correlated geologic units

Label Pzeg
Description Etivluk Group, undivided: Includes Siksikpuk and Otuk Formations and underlying Immaitchiak Chert
Geologic age Pennsylvanian to Bajocian
Geologic setting Sedimentary, slope-and-deep-water
Lithology Form Importance
Chert < Chemical < Sedimentary Bed Major
Graywacke < Sandstone < Clastic < Sedimentary Carbonaceous Indeterminate, major
Argillite < Metaclastic < Metasedimentary < Metamorphic Zeolitic (prehnite-pumpellyite) Minor
Shale < Mudstone < Clastic < Sedimentary Carbonaceous Minor
Limestone < Carbonate < Sedimentary Bed Incidental