Tukwila Formation (en.wikipedia.og)

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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.

Puget Group (Wikipedia) The Puget Group is a geologic group in Washington (state). It preserves fossils dating back to the Paleogene period. ¶ Two key formations include the Renton Formation and the Tukwila Formation.
King County, Washington (Wikipedia) King County is located in the U.S. state of Washington. The population was 2,269,675 in the 2020 census, making it the most populous county in Washington, and the 13th-most populous in the United States. The county seat is Seattle, also the state’s most populous city.

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.