Named for Etivluk River, tributary of Colville River, western Endicott Mountains, northern AK. Type locality designated as composite of type locality of Siksikpuk Formation (secs.21 and 23 T12S R1E) and type section of Otuk Formation (sec.31 T10S R16W, Killik River quad). Consists of (ascending): Siksikpuk Formation and Otuk Formation (new) which includes Blankenship Member (new). Group consists characteristically of thin-bedded chert, shale, silicified shale, and silicified limestone. In Endicott Mountains and in some places in DeLong Mountains, Etivluk Group appears to disconformably overlie Lisburne Group; elsewhere contact may be gradational. Disconformably underlies bed of shale, graywacke and conglomerate of Early Cretaceous age. Age of Siksikpuk is Pennsylvanian, Permian, and Early Triassic, and age of Otuk Formation ranges from late Early Triassic to early Middle Jurassic (both based on fossils, some of which are listed in report).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
Includes newly named formation, Imnaitchiak Chert, in Picnic Creek allochthon, Killik River quad. Imnaitchiak Chert contains some rocks previously assigned to Siksikpuk Formation (of Etivluk Group).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
Etivluk Group revised to adopt and include Imnaitchiak Chert of Mull and others (1987). Age of group now is Early Pennsylvanian, Permian, Triassic, and Early and Middle Jurassic in part based on age for Imnaitchiak Chert.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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