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Ancient Sea Fossils Still Shine Millions of Years Later
16 Jul
Summary
- Colorful ammonite shells from 69-72 million years ago still shimmer.
- Fossils from the Western Interior Seaway are displayed at Smithsonian.
- Ancient seabed soil formed fertile land for Midwest farming.
Over 70 million years ago, much of present-day South Dakota was submerged under the Western Interior Seaway, a vast inland sea that split North America. This ancient ocean teemed with life, including giant marine reptiles and ammonites, many of which have left behind remarkably preserved fossils.
These fossils, some dating back 69 to 72 million years to the final years of the dinosaurs, are now exhibited at the Smithsonian's National Museum of Natural History. Notably, some ammonite shells display vibrant colors and shimmer due to their mother-of-pearl composition, a phenomenon enhanced during fossilization.
The Western Interior Seaway existed for over 30 million years, spanning from the Arctic to the Gulf Coast during the Cretaceous period. As global climates cooled, sea levels dropped, and the seaway receded, reconnecting the continent.
Beyond fossils, the seaway's geological legacy includes the formation of fertile soil in the American Midwest, which remains a crucial agricultural region today. Evidence of ancient marine life, like sea stars and brachiopods, is found across North America, illustrating the continent's ever-changing geological history.
