Madison, Indiana: Geomorphology, and Paleozoic and Quaternary geology
The Madison area in southeastern Indiana has long beenacclaimed for its geomorphic features, Upper Ordovician fossils, and scenic beauty. Madison is located on the Ohio River (Figure1) almost midway between Cincinnati, Ohio, and Louisville, Kentucky. [t is easily accessible by several state highways, and theU.S. 421 bridge over the Ohio River at Madison providesaccess from Kentucky. Clifty Falls State Park offers outstandingrecreational and camping facilities. Madison actually consistsof two towns separated from each other by a 300 ft (90 m)-high rocky bluff: so-called Historical Madison located on theterraces and floodplain and the newer North Madison located onthe upland.
Upper Ordovician and Silurian strata, well exposed in theMadison area along numerous road cuts and tributaries of theOhio River, dip gently westward along he western flank of theCincinnati Arch and the eastern margin of the Illinois Basin. Thebest and most easily accessible outcrops are along U.S. 421 justnorth of Madison where the highway rises from the Ohio Rivervalley to the uplands.
The fossiliferous Ordovician outcrops at Madison areamong the classic Cincinnatian fossil-collecting localities ofsoutheastern Indiana, southwestern Ohio, and northern Kentucky.In addition, the distinctive dolomitic and sparsely fossiliferousSaluda Formation near the top of the Ordovician is wellexposed and reaches its maximum thickness in the Madison area. A roadlog at the end of this article and keyed to Figure 1describes access to the many points of geologic interest in theMadison area. Important vantage points are shown by letters in Figure 1.