The pre-Trenton sedimentary history of the Cincinnati Arch geologic province involves the paleogeology and paleogeography of eastern North America from earliest geologic time to Late Ordovician. The early sedimentary record indicates that the North American continent was built up through geologic time by the addition of successive, broad, sedimentary continental shelves around an original shield area composed of igneous and metamorphic rocks. The shield area furnished the original clastic sediments for the shelf areas throughout many erosional cycles. Lack of terrestrial vegetation had a profound effect upon pre-Chazyan sedimentation; eolian activity was extremely important on a broad scale, and erosion, transportation, and deposition of clastic sediments were much more r pid than in subsequent geologic time in eastern United States.

A theory for the origin of "original" dolomite by the diagenetic decomposition of authigenic biotite mica accounts for production of dolomites of widespread formational extent. This theory provides a source of magnesium for the conversion of marine limestones to dolomites, and accounts for the presence of glauconite in sub-Trenton rocks. It explains formation of chert, kaolinite, and siliceous cement by the diagenetic decomposition of authigenic feldspar. "Redeposited" or precipitated dolomite is thought to have resulted from solution of "original" dolomite and subsequent precipitation. "Replacement" or secondary dolomite is attributed to the circulation of magnesium-rich waters through fractures and porous zones in pre-existing limestones.

The transgressive nature of Cambrian deposition involved the movement of three distinct zones of sedimentation northwestward across the Cincinnati Arch geologic province. This resulted in the deposition of three distinct but transitional and time-transgressive bodies of sediment prior to the deposition of the widespread Knox Dolomite Supergroup. The unconformity at the top of the Knox Dolomite Supergroup represents an important time break between two distinctly different periods of sedimentation and two distinctly different lithologic types and fauna.

The interval between the end of Grenville deposition (approximately 1,000 million years ago) and the beginning of Cambrian deposition (about 550 million years ago), represented by the Ocoee, most of the Chilhowee, the Grand Canyon, the Belt, and the Windermere Groups of rocks, and by the extensive period of erosion preceding Cambrian time, is equivalent to a geologic era. The name Lipozoic Era is proposed for this part of geologic time.