Geologic Map of Alaska: Etivluk Group, undivided

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