UPPER MISSISSIPPIAN SEISMIC REFLECTION CHARACTERISTICS IN OSAGE COUNTY, OK

This presentation reports progress on analyzing two full-wave sonic logs in Osage County, OK, with the purpose of estimating post stack seismic reflectivity near the Mississippian-Pennsylvanian boundary. The M-P contact is a major, regional unconformity documented in outcrop, wire line, and surface seismic data. In our study area the key units are Lower Penn. clastics, Miss. Chat or tripolite, and Miss. Dense Limestone. 3D seismic data shows a strong negative amplitude anomaly in close proximity to the M-P contact implying that tripolitic chert exists at the top of the Miss. in direct contact with the Penn. section. Based on average Vp and density values from the well logs, we have estimated average acoustic impedance for key units and examined reflection coefficients in all possible contact scenarios. Our results, find that the observed seismic amplitude anomaly is only consistent with an Miss. Dense Lime over tripolite contact, whereas a direct Penn. over tripolite contact would have very low reflectivity. Thus our work supports the interpretation (seen in outcrop) that the 3D seismic amplitude anomaly represents tripolite developed at some depth into the Miss. rather that directly at the M-P unconformity.