Recent Designations

Loss of Dinosaurs Marks the Newest National Natural Landmark Site

In November 2016, Secretary Jewell officially designated the West Bijou Site as a National Natural Landmark (NNL). Located approximately 31 miles east of Denver in Arapahoe and Elbert Counties, Colorado, the addition of West Bijou Site brings the total number of NNLs nationwide to 599.

The West Bijou Site contains some of the most scientifically important exposures of the Cretaceous-Paleogene (K-Pg) boundary [formerly known as the Cretaceous-Tertiary (K-T) boundary].The 1.18 inch band of sediments marks a significant event in Earth's history;a massive extinction of dinosaurs and other terrestrial vertebrates associated with the end of the Cretaceous period of the Mesozoic Era, and the beginning of the Paleogene period of the Cenozoic Era.The K-Pg boundary at the West Bijou Site contains several important features that contribute to our understanding of the most recent of Earth's five large mass extinctions. These features include Cretaceous and Paleogene pollen records and vertebrate fossils, and minerals and metals that support the hypothesis of asteroid impact as the cause of extinctions. Unlike many of the K-Pg sites in the region, magnetostratigraphy and radiometric dating have been completed at the site.

Bisecting the site, West Bijou Creek, maintains a natural hydrologic pattern, flowing through a mosaic of upland and riparian shortgrass prairie plant communities, supporting a diversity of common and rare plant and wildlife species.

West Bijou Site provides an excellent example of a valuable geologic resource located within a natural shortgrass prairie ecosystem.

Scenic view and sunflowers at West Bijou NNL.
West Bijou NNL located in Colorado.

Photo by NPS.

Last updated: March 10, 2020


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