One of my favorite places to hike in the Billings area is Zimmerman Park, which is mostly atop the Rimrocks, a cliff formed by sandstone of the Cretaceous Eagle Formation. The Eagle Formation is usually interpreted to be either a barrier island deposit, similar to Padre Island in Texas, or a shallow marine sand bar that ran parallel to the shoreline. The sand was deposited in the Western Interior Seaway, a shallow body of water which stretched across North America from the Arctic to Gulf of Mexico. From Billings, sedimentary rocks become increasingly marine-dominated to the east, and terrestrial to the west.

Here are a few pictures from today’s late afternoon hike: