OSAGEAN REACTIVATION OF THE WAVERLY ARCH AS A POTENTIAL MECHANISM FOR SHALLOW WATER TIDALLY INFLUENCED DEPOSITS IN THE COWBELL/LOGAN OF SOUTHEASTERN OHIO

The Cowbell/Logan outcrops along Ohio-Hwy 823 in Scioto County, Ohio contain shallow water traces, heterolithic facies (flaser, wavy, and lenticular bedding), bidirectional to herringbone cross beds, and other shallow water sedimentary structures that are inconsistent with a delta front system.

To investigate the origin and lateral extent of these heterolithic and potential shallow water facies types, an outcrop and core study was undertaken. Cores were analyzed and described using a combination of handheld XRF, spectral gamma-ray logging, lithologic observations of sedimentary structures, trace and body fossils, and grain size.

Interpretations of gamma-ray, geochemical, and lithologic facies stacking patterns highlighted what appears to be progradation from open marine muds and siltstones of the underlying Nancy into shelf siliciclastics of the lower Cowbell; however, the heterolithic beds capping this progradation are overlain by hummocky cross-stratified lithofacies (HCS). These hummocky and amalgamated sands are more thickly bedded than the heterolithic facies and appear to have been deposited in deeper water.

Although there are truncation surfaces in both the HCS and heterolithic facies, neither appear to indicate sustained subaerial exposure due to a lack of rooted or weathered surfaces. Evidence does however exist for a potential sequence boundary/correlative conformity within or near the heterolithic facies. Gamma-ray facies stacking patterns, Zr/Al ratios, and a shift to a Skolithos ichnofacies containing Diplocraterion align with a sequence boundary/correlative conformity near the top of the heterolithic facies. A return to Cruziana ichnofacies and hummocked siltstones, as well as a change in stacking patterns, points to subsequent aggradation/retrogradation of siltstone bodies within the upper Cowbell.

This relative sea level progression is inconsistent with published reports of continuous sea level regression during the Osagean Borden interval. A potential mechanism for the shallow water facies and discrepancy in sea level trajectory could be an early reactivation of the Waverly Arch which runs through the study area. This would indicate that the Waverly Arch reactivated sooner than the late Meramecian previously documented in Kentucky.