Brush Creek Canyon is a 217-acre preserve containing a rugged forested gorge along the Silurian Escarpment. Located two miles north of Arlington in Fayette County, it was dedicated as a biological and geological state preserve in 1968.
Located on the western edge of the Paleozoic Plateau landform region, Brush Creek Canyon exemplifies the dramatic landscape of a prominent ridge extending through northeast Iowa known as the Silurian Escarpment. The steep slopes and exposed bedrock of this preserve are formed by 150-foot-tall outcrops of Silurian (435 million years old) dolomite of the Hopkinton Formation. Older, underlying shales are of Ordovician age (450 million years old). In many places, large blocks of dolomite have separated from the cliffs and slumped onto the soft, wet shales underneath, often rotating and leaning as they shift position. The spectacular bluffs and slump blocks are the result of a long history of natural stream erosion in the Brush Creek valley.