PRECAMBRIAN-CAMBRIAN CARBONATE BASINS IN OHIO AND INDIANA
ABSTRACT In the last decade the perception of the ideas about the rocks below the Mount Simon Sandstone in southwestern Ohio have undergone dramatic change. This change is due to a stratigraphic test hole (DGS2627) in Warren County and a number of seismic lines scattered throughout the region. Some of this recently recognized complexity was actually known 70 years ago when a hole (Friend #1 Mattinson) was drilled 404 m into rocks below the Mount Simon Sandstone in Southern Clark County. This well, though reported in the literature at the time was generally forgotten until recently. The original reports on this well and more recent study of the cutting have led us to collect 40 km of seismic data in the area around the well. The limited portion of the basin covered by the present seismic data is 6 km by 6 km. The eastern edge appears to be near South Charleston but the basin is continuing to thicken at the western end of the seismic lines. On the basis of the Friend #1 Mattinson cuttings we know that the upper part of the pre-Mount Simon rock is carbonate. Our interpretation is that the carbonate rock may be 1220 m thick and this unit lies on rock with seismic characteristics similar to the Middle Run Formation in Warren County. The top of the carbonate unit is very irregular suggesting an unconformity with the Mount Simon deposited on a karst surface. The only other location where we have found carbonate rock described below the Mount Simon is in Jay County, Indiana about 140 km to the northwest. The Friend #1 Mattinson well reports provided evidence of hydrocarbon potential and the seismic sections show several possible trap types. Much is unknown about the basin but we think the evidence points to the potential for hydrocarbon production. A modern well is needed in the vicinity of the Friend #1 Mattinson well to clarify the nature of the basin and to test its production potential.