Blanchard Mountain was once covered in a massive sandstone deposit called the Chuckanut Formation. Over time, this sandstone unit grew to be more than 10,000 feet thick, trapping many fossils of ancient plant and animal species.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.Dave Tucker (geologist) (Wikipedia)
David Samuel Tucker is a geologist, author, and union organizer in Washington state. He is a research associate at Western Washington University. He was an instructor at North Cascades Institute, and the director of the Mount Baker Volcano Research Center (now closed). He writes the blog Northwest Geology Field Trips, a blog aimed at laypeople detailing where to find interesting geology in the Pacific Northwest. In 2015, he published a popular book on Washington geology, Geology Underfoot in Western Washington. He resides in Bellingham, Washington. In the 1980s he worked as a mountaineering guide in the Cascades, Mexico, and South America.It is thought that the Chuckanut Formation shoreline was of riverine environments combined with a large scale “bedding plane” of material deposition.Racehorse Creek (wa100.dnr.wa.gov)
Racehorse Creek, a small waterway near Deming, Washington, is a must-see destination for fossil aficionados. The area is known for its fossil beds—50 million-year-old leaf fossils, including sycamore and swamp cypress, await dedicated collectors. In addition to abundant fossils, the creek boasts the impressive Racehorse Falls, a 169-foot-tall multi-stage waterfall that’s a short 0.6 mile hike to reach.The Chuckanut Mountains were formed by the folding of the Chuckanut Formation (which is predominantly made up of layers of 55-million-year-old sandstone, conglomerate, shale, and bituminous and sub-bituminous coal) and the later Huntingdon Formation (predominantly shale and sandstone) on top, as well as an exposed section of pre-Jurassic-age phyllite