The Rome and Conasauga Formations grade westward into the Eau Claire Formation, which is composed of sandstone, siltstone, shale, and dolomite. The Eau Claire ranges in thickness from about 200 feet to more than 500 feet. Overlying these units in the central part of the state is the Kerbel Formation, an upward coarsening sandstone that is interpreted to be a wedge of deltaic sediments. The Kerbel is absent in southernmost, western, and eastern Ohio. Generalized paleogeography of Ohio and adjacent areas during late Middle Cambrian time.
Arrows indicate direction of sediment deposition.
The subsiding Rome trough south and east of Ohio accumulated a great thickness of Cambrian sediments. East of the Rome trough was the continental edge and the Iapetus Ocean. The Knox Dolomite is more than 1,300 feet thick in the southern part of the state and thins to the north beneath a major regional unconformity. Knox deposition continued throughout the remainder of the Cambrian and into the Ordovician Period. The Cambrian-Ordovician boundary therefore is uncertain, lying within the upper part of the Knox but not marked by a significant unconformity.