STRATIGRAPHIC AND DEPOSITIONAL ANALYSIS OF THE LEONARDIAN CIBOLO FORMATION IN THE MARFA BASIN IN THE VICINITY OF THE CHINATI MOUNTAINS, TEXAS

The Marfa Basin in Presidio County, Texas, forms the southwestern extent of the Permian Basin. The exposed Lower Permian strata within the Marfa Basin are found roughly 10 miles north of Shafter, Texas, at the Cibolo Creek Ranch. The Lower Permian strata of the Marfa Basin is less studied than the age-equivalent strata of the nearby Delaware and Midland Basins. A detailed study of the Lower Permian strata in the Marfa Basin will enable a better understanding of the depositional and environmental relationships between the less restricted Marfa Basin and the more restricted Delaware and Midland Basins. In order to accomplish this the Lower Permian strata exposed near the Chinati Mountains are being described and correlated using modern carbonate descriptions, lithostratigraphy, biostratigraphy, and sequence stratigraphy. Using this data a depositional model will be created for the Leonardian-aged Cibolo Formation. The Cibolo Formation may represent shelf edge to shelf deposits. Improving the current state of knowledge of the Permian strata within the Marfa Basin will further enable potential for future prospects and plays of petroleum that have not been fully explored within the sedimentary basin. In order to better constrain the timing of events within the Marfa Basin fusulinids will be identified and correlated to known fusulinid zones within the rest of the Permian Basin. Using facies analysis, identification of sequence boundaries will be attempted to determine vertical changes within the section. The data collected from facies analysis and sequence boundaries will be used to determine possible eustatic changes within the Marfa Basin. The Cibolo Formation will be compared to the rest of the time-equivalent formations of the Permian Basin in terms of eustatic changes, and fossil assemblages and depositional settings.