The Earth Story

Bobcat Draw

This photo was taken by the U.S. Bureau of Land Management in the Bobcat Draw Badlands of Wyoming. This site sits in a small basin surrounded by the Bighorn Mountains in the East and the Absaroka Mountains, seen in the background of this image, to the west. The Bighorn Basin is a Laramide mountain range – during the Cretaceous, blocks of deeply rooted, metamorphic crust were thrust upwards on gigantic and deep faults and the Bighorn range is one of those blocks. The Absaroka mountains to the west are younger than the Laramide uplifts and represent a flareup of volcanism that took place after the end of the mountain building events.

As these mountains rose, sediments from them eroded and traveled down rivers to a nearby basin. The sediments in the Bobcat Draw Badlands represent two geologic units made of river sediments carried down rivers into these basins in the Paleocene and Eocene. As those mountains rose about 60-40 million years ago, they also filled in this lowland nearby. Today, some rivers still drain the Bighorns to the west into this basin, but water eventually finds its way out and carries sediments with it, leaving behind this eroding, colorful landscape.

-JBB

Image credit: Bob Wick, Bureau of Land Management https://www.instagram.com/p/BP73N3DlnH6/

Reference: https://pubs.usgs.gov/bul/1756e/report.pdf (big pdf)