Chemostratigraphy of the Mississippian-Age Barnett Formation, Northern Fort Worth Basin

Krystin Robinson and Harry Rowe
University of Texas at Arlington, Arlington, Texas 76019

The Mississippian Barnett Formation is a lithologic unit composed primarily of laminated siliceous mudrock with some lime mudrock intervals. The Barnett Formation was deposited in the Fort Worth Basin, a Late Paleozoic marine foreland basin that formed as a result of the early Ouachita Orogeny from the collision of Laurasia and Gondwana. The objective of the project is to develop and interpret stratigraphic changes in the geochemistry of the Barnett Formation for the purposes of 1) understanding the paleoceanography of the northern Fort Worth Basin during a unique period in Earth history (ocean anoxia event), 2) develop regional correlation using multiple cores, and 3) refining the stratigraphy for the oil and gas industry. Methods used to carry out the project include: real-time geochemical analysis using x-ray fluorescence (XRF) of the core face, TOC (total organic carbon) and TIC (total inorganic carbon) analysis, and stable carbon isotope analysis of organic and inorganic constituents. Preliminary core data demonstrate that the Barnett Formation is largely siliceous mudstone. Elevated concentrations of redox-sensitive trace elements, including molybdenum, vanadium, zinc and uranium indicate that periods of anoxia and euxinia existed during deposition. These conditions likely contributed to a high level of preservation for organic material. Carbonate dilution occurs throughout the core; however, major element (Ca) data for the core shows thin carbonate-rich layers that likely represent periods of reduced siliciclastic input to the basin. These results further correlate the stratigraphy of the Barnett Formation as well as provide further support for the depositional environments depicted.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012