Just a Day at the Beach

With all the hot & humid days we've had this summer, it'd be nice to spend a day at the beach... and if it were 90 million years ago, we'd be in luck! During the late Cretaceous period (90 mil. years ago), the North American continent was split by a shallow inland sea and western Iowa was right on the edge.


If you're skeptical, take a walk along the shale & limestone bedrock outcrops, near the western entrance and also throughout the park. If you look closely among the piles of rock that have broken from the bedrock, you'll find dozens of clams! This fossil clam (known as Inoceramus) is abundantly found in the thinly bedded limestone of Cretaceous age that are found close to the land surface in the northern Loess Hills; Stone Park is a great place to view them!



If you're interested in geology, here are the names of the formations visible at the western entrance of Stone Park: At the top of the bedrock exposure, the Greenhorn Formation of Cretaceous age can be seen; the strata below include shale and thin limestones of the Graneros Formation, and below that are the sandstones of the Dakota Formation.

For more information, check the Iowa DNR's webpage.