Mattheissen State Park began its slow transformation from a shallow marine environment to what it is today over 400 million years ago. All the things that make the park so interesting to visitors were created through geologic processes that took millions of years to transform the landscape. Many of those processes continue on to this day. The waterfall in the background of this photo, for instance, was produced by the headward erosion of Deer Creek. The orientation of Deer Creek at the bottom of the valley is not a coincidence. It was this stream that created the Lower Dells, cutting through St. Peter Sandstone. Both stream downcutting and other erosional forces, such as joints, continue to widen the valley today.
photo of Cascade Falls
The Lower Dells area of Matthiessen Park is formed exclusively of St. Peter Sandstone. Other areas of the park contain various Pennsylvania strata and Platteville Dolomite. Platteville Dolomite was deposited in the Ordovician Period, while what is now the Matthiessen area was still a high energy, shallow marine environment. The Pennsylvania strata was created as the position of the ancient Pennsylvanian shoreline continually changed. Both marine and non-marine sediments are present as a result of those fluctuations in water level. The changes in depositional environment created cyclical alterations of sandstone, limestone, shale, and coal. Coal can be found in the park, although it is not mined as a mineral resource. The coal found in the Matthiessen area is the Colchester formation.