- Usage in publication:
-
- Ivishak member*
- Modifications:
-
- Named
- Biostratigraphic dating
- Dominant lithology:
-
- Shale
- Siltstone
- AAPG geologic province:
-
- Alaska Northern region
Summary:
Named as upper member (of 2) of Sadlerochit formation [for Ivishak River]. Type locality designated as east side of Flood Creek between 69 deg 02'40"N and 69 deg 03'20"N where strata dip from 40 deg to 54 deg N, Shaviovik and Sagavanirktok Rivers region, north slope of Brooks Range, northeastern AK. Typically consists of two parts: lower nonresistant shale and minor siltstone unit and an upper resistant siltstone, shale and sandstone unit. Thickness is from 1000 to 2000 ft. Overlies Echooka member (new) of Sadlerochit formation); underlies Shublik formation. Report includes 7 measured sections, lists of fossils with locations, and geologic map of Shaviovik and Sagavanirktok Rivers region. Age of fossils is early part of Scythian Stage (Kummel, written commun., 1954). Age of Ivishak Member is Early Triassic.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Ivishak Member*
- Modifications:
-
- Areal extent
- AAPG geologic province:
-
- Alaska Northern region
Summary:
Ivishak Member of Sadlerochit Formation geographically extended eastward to Kongakut River-Joe Creek area as shown in correlation chart.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Ivishak Formation*
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Alaska Northern region
Summary:
Ivishak Member of Sadlerochit Formation (Keller and others, 1961) raised in rank to Ivishak Formation of Sadlerochit Group. Divided into three newly-named members (ascending); Kavik, Ledge, Sandstone, and Fire Creek Siltstone. Type locality at Flood Creek remains same. Age remains Early Triassic based on marine fauna.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Ivishak Sandstone
- Modifications:
-
- Revised
- Biostratigraphic dating
- AAPG geologic province:
-
- Alaska Northern region
Summary:
In subsurface Prudhoe Bay area Ivishak Sandstone of Sadlerochit Group is equivalent to Ledge Sandstone member of Ivishak Formation of Detterman and others (1975). Age of Ivishak Sandstone is tentatively assigned to Late Permian to Early Triassic (early to middle Scythian) based on microfloral assemblage.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).