These formations, known as the Cincinnatian Series, are approximately 200 meters (600 feet) thick and are composed of alternating thin to very thin bedded, gray, fossiliferous limestone and blue-gray ...

Point Bar Features Larger fragments of limestone and weathered shale are common, as are individual fossils weathered out of their enclosing rocks. Cut Bank Features A close-up view of the cut bank ...

A sandstone and shale cap, as thick as 50 feet in places, acts as an umbrella over limestone ridges. The umbrella leaks at places called sinkholes, from which surface water makes its way ...

The Journal of Geology, Vol. 37, No. 7 (Oct. - Nov., 1929), pp. 639-671 (33 pages) The Decorah formation of Ordovician age has been denned as a shale lying above the Platteville limestone and below ...