It is a river/lake deposited, feldspar-rich quartz sandstone, deep red in color with white mottling. The Jacobsville Formation, of Late Precambrian age, is the oldest formation exposed in the lakeshore. For a short distance inland from the escarpment, bedrock is occasionally exposed. These extend along the lake about from Munising to Beaver Basin. Except for their exposure near Lake Superior, these layers are presently covered by a veneer of Quaternary glacial drift.īedrock is best observed in the western one-third of the park where cliffs rise up from Lake Superior.

These deposits became the sandstone layers that are exposed within the lakeshore. Geologic history recorded in the sedimentary rocks and surficial deposits of Pictured Rocks National Lakeshore is limited to two widely separated intervals of geologic time, the Late Precambrian, Cambrian, and Early Ordovician Periods (500-800 million years before present), and the Late Quaternary Period (two million years before present to the present).ĭuring the Cambrian and Early Ordovician periods, sediments were deposited in the shallow seas and near-shore deltas that covered what is now northern Michigan. Sea caves, arches, blowholes, turrets, stone spires, and other features like the famous Chapel Rock have been sculpted from these cliffs over the centuries by unceasing waves and weather. sandstone cliffs that extend for more than 15 miles along the shoreline. The geologic formations of Pictured Rocks National Lakeshore are most spectacularly represented by the 50-200 ft.

Definition of township us geological