Champlainian series (Middle Ordovician) in Illinois

The Champlainian (Middle Ordovician) rocks of Illinois consist of a large number of widely distributed rock-stratigraphic units, some of which have not been previously described. In this study many of the formations and members were traced by lithologic criteria, supported in most cases by faunal evidence, from the Mississippi Valley east to New York, west to Colorado, north to Manitoba, and south to Tennessee. Conditions of sedimentation during the Champlainian were remarkably uniform over much of the stable interior part of the continent.Ope