Paleontology and geologyShallow seas covered Iowa during the Silurian, and the rocks of this time interval are predominately dolostones, found today in the eastern part of the state. These rocks formed from limy muds that accumulated on the ancient sea floor. The first large-scale reefs formed during the Silurian, although these structures were more like muddy “mounds” than the reefs growing in the tropics today. The preserved remnants of some of these reefs can be seen in eastern Iowa, where fossils include distinctive "chain corals," numerous species of brachiopods, snails, and other marine invertebrates. |