Correlation & Biostratigraphy of Surface and Shallow Subsurface Sections of the Barnett Shale, Llano Uplift, South-central, Texas

Abstract

An outcrop section and a shallow subsurface core of the Barnett Shale from the Llano Uplift, Texas, were described and sampled for conodont biostratigraphy. A total of eighty nine samples were collected and processed for conodont recovery. The biostratigraphic framework was developed based on faunal analysis and correlated to the lithologic descriptions. Exposure surfaces/ unconformities were identified in outcrop and cored section of the Barnett Shale interval. The Barnett Shale in outcrop is missing the middle and lower Meramecian section. The uppermost Barnett Shale contains Morrowan (Pennsylvanian)forms. The Marble Falls Limestone unconformably overlies the Barnett Shale and is missing the lowermost Morrowan section. The cored Barnett Shale interval is missing the entire Chesterian section and is unconformably overlain by Atokan Marble Falls Limestone. The Morrowan Marble Falls Limestone is absent. The contact between the Marble Falls Limestone and Barnett Shale is marked by an exposure surface with an incipient paleosol.