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- Usage in publication:
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- Humptulips Formation
- Modifications:
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- Named
- Biostratigraphic dating
Summary:
Unit is named the Humptulips Formation. Includes strata in the northern part of the Grays harbor basin, WA previously referred to as sedimentary rocks of late Eocene age. Consists of massive to thinly laminated sandy siltstone, mudstone, and sandstone that contain light-gray-weathering tuff beds. Unconformably overlies the Crescent Formation; conformably underlies the Lincoln Creek Formation. Correlates with the Skookumchuck and McIntosh Formations in southwest WA and the Aldwell Formation and Twin River Group to the north. Thickness is greater than 3000 ft. Age is middle and late Eocene (Narizian) based of fossils [foraminifers]. (B1565)
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 ([ ]).