- Usage in publication:
-
- Slate Peak Member
- Modifications:
-
- Named
- Biostratigraphic dating
- Dominant lithology:
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- Sandstone
- Siltstone
- Argillite
- Conglomerate
- AAPG geologic province:
-
- Cascades province
- Okanogan province
Summary:
[Named for Slate Peak in north-central part of unit]. Type locality defined as Barksdale's type locality for Virginian Ridge Formation just west of Winthrop on Wolfe Creek [secs. 35-36 T35N R20E, Thompson Ridge 7.5' quad, Okanogan Co, WA] Measured "composite-stratotype" section (800 ft thick) is on ridge running southeast from Harts Pass. Consists of sequence of thin-bedded lithic sandstone, siltstone and argillite punctuated by thin laterally persistent chert-pebble conglomerate beds. Conformably overlain by Winthrop Formation in southern part of Methow basin; in western basin margin unit is overlain and interfingers with Devil's Pass Member (new) of Virginian Ridge Formation. Overlies Patterson Lake Member (new) of Virginian Ridge Formation in southern part of basin; elsewhere unit unconformably overlies rocks of Harts Pass [Formation!]. Fossils from several localities indicate age as Albian and Cenomanian [Early and Late Cretaceous].
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.
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