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. A total of nearly 270 plant species have been found in the preserve. The rugged topography provides a variety of habitats, ranging from north and east-facing slopes that are deeply shaded, humid, and cool to south and west-facing slopes that are sunny, warm, and dry. Cliff faces host an interesting community of ferns, forbs, and shrubs, and are often dominated by Canada yew. Red oak, sugar maple, white oak, and basswood are the dominant tree species on the slopes. Blue beech and ironwood dominate the understory, with leatherwood, downy arrowwood and bladdernut found on the upper slopes.
Pottawattamie County September 30, 2023