- Usage in publication:
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- Shut-in Formation*
- Modifications:
-
- Named
- Reference
- Dominant lithology:
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- Conglomerate
- Sandstone
- Mudstone
- AAPG geologic province:
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- California Coast Ranges province
Summary:
Named for The Shut-in, narrow gorge of Nacimiento River. Type locality is exposures at The Shut-in [gorge] in sec. 19, T24S R8E Burnett Peak 7.5' quad, Monterey Co., CA. Reference section is near Beasley Flat, sec. 11 and 12, T25S R8E, Bryson 7.5' quad, San Luis Obispo Co., CA. Composed of conglomerate with thick-bedded sandstone at type section and mappable beds of sandstone and mudstone in northwest direction. 300 m is exposed at type; is as much as 925 m thick in the northwest part of the Burnett Peak 7.5' quad. Unconformably underlies Piedras Altas Formation (new). Conformably overlies Italian Flat Formation (new) in Bryson 7.5' quad. Italian Flat fault cuts out base in Burnett Peak 7.5' quad. Age is Late Cretaceous (late Maastrichtian(?)) based on fossils [agglutinated foraminifers (spiroplectamminids, W.V. Sliter, written commun., 1985)].
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 ([ ]).