SUBSURFACE FACIES ANALYSIS OF THE CAMBRIAN UPPER CONASAUGA GROUP AND KERBEL FORMATION IN EAST-CENTRAL OHIO

This study presents a subsurface facies analysis of the upper part of the Conasauga Group and Kerbel Formation (both Upper Cambrian age) using well core and geophysical logs. In Well no. 2580 (Seneca County), the upper part of the Conasauga Group is 35- m thick and the total thickness of the Kerbel Formation is 31-m thick. Analysis of the well core identified 14 lithofacies including: massive, laminated, cross-laminated, and hummocky stratified sandstone with burrows; massive and laminated mudstone; heterolithic sandstone and mudstone with tidal rhythmites (double mud drapes), flaser-, lenticular-, and wavy- bedding; and massive arenaceous dolostone. In general, the upper part of the Conasauga Group was a mixed silicicalstic-carbonate depositional system with abundant tidal sedimentary structures consistent with a shallow marine depositional setting. Depositional sequences are interpreted as repetitive prograding tidal flats and adjacent sub-environments. In contrast, the overlying Kerbel Formation represents a transition to a siliciclastic depositional system with a noted transition from planar-laminated and hummocky stratified sandstone with mud drapes at the base to a coarser-grained, more massive sandstone near the top. This sequence is consistent with the progradation of a clastic shoreline or progradation of a delta front distributary channel. Ongoing studies involve correlating these results laterally using geophysical logs from adjacent wells.