- Usage in publication:
-
- Constitution Formation
- Modifications:
-
- First used
- Dominant lithology:
-
- Sandstone
- Siltstone
- AAPG geologic province:
-
- Puget Sound province
Summary:
Constitution Formation covers much of eastern half of Orcas Island (including type area, Mount Constitution) and much of central part of San Juan Island. Consists of generally fine-grained sandstone and siltstone. Is 3000 ft thick. Underlies Deer Point Formation. Overlies Permian beds. Age is Late Triassic or Jurassic(?).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Constitution Formation
- Modifications:
-
- Named
- Dominant lithology:
-
- Siltstone
- Graywacke
- Tuff
- AAPG geologic province:
-
- Puget Sound province
Summary:
Named for exposures at type area on Mt. Constitution, Orcas Island, San Juan Co, WA. Composed of brown, gray, and green massive to slaty, sheared, highly deformed turbidites with prehnite veinlets. Lithologies include siltstone and graywacke. Greenish tuffs and tuff breccias, and light colored lithic sandstones are also present in unit. Thickness is greater than 10,000 ft. Unconformably overlies Orcas Formation. Underlies Lummi Formation. Age is Jurassic or Early 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.
"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 ([ ]).