- A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers.
- Chuckanut Formation (Wikipedia)
The Chuckanut Formation in northwestern Washington (named after the Chuckanut Mountains, near Bellingham), its extension in southwestern British Columbia (the Huntingdon Formation), and various related formations in central Washington (including the Swauk, Roslyn, Manastash, and Chumstick) are fluvial sedimentary formations of Eocene age, deposited from about 54 million years ago to around 34 million years ago. The nature of the deposits and included plant fossils indicate a low-lying coastal plain with a subtropical climate; the nature of the sediments indicates metamorphic sources in northeastern Washington.
- Renton Formation (Wikipedia)
The Renton Formation is a geologic formation in Washington (state) within the Puget Group. It preserves fossils dating back to the Paleogene period.
- Tukwila Formation (en.wikipedia.og)
The Tukwila Formation is a geological formation in King County, Washington within the Puget Group. It is named after Tukwila area, which is close to the formation. The formation consists of various fossils of marine origin.