Brown County State Park: Land of Scenic Hills, Ridges, and Valleys (GM-06)
The scenic "Hills of Brown County" were carved from sedimentary rocks that formed about 300 million years ago when southern Indiana was covered by a shallow inland sea. Sand, silt, and mud from highlands to the northeast were carried into this sea by ancient river systems and were deposited in a vast delta complex similar to that of today's Mississippi River. These deposits later hardened into sandstones, siltstones, and shales that form the Borden Group of rocks. Later still, the sea cleared, and thick bed of limestone were deposited over these rocks.

Following regional uplift, the rocks were exposed to weathering and erosion. After that time, hundreds of feet of these ancient rocks were stripped away by the streams of those times, and the scenic hills and valleys of this area were eventually formed. Where more resistant sandstones protected the underlying rocks, much more prominent hills like Weed Patch Hill, Hohen Point, and others were formed.

Ice Age glaciers never actually reached Brown County State Park, but evidence of them can be seen north and east of the park.

Our Hoosier State Beneath Us: Geomorphology