Petrographic and stratigraphic analysis of the Barnett Shale (Mississippian) in Hill County, Texas: Evidence for eustacy and tectonism.

摘要

The major facies in the EOG Gordon SWD core are mudstone, siltstone, phosphatic layers, shell layers, and a carbonate concretion. Facies C 2 is a sandy phosphate layer, which concentrated organic matter. Facies C2 is traceable and can be interpreted as a condensed section associated with a maximum flooding surface. The uranium in phosphate and organic matter cause a high gamma-ray reading in this interval. High TOC and high gamma-ray response occur in the same intervals of the core, but their magnitudes are not directly related. The Barnett deposition was sourced from the north and was a function of eustacy. The middle and upper unit were sourced from the Ouachita fold-thrust belt. The siltstone facies, common in these intervals, is rich in sponge spicules and is sourced from a reef growing on the thrust belt. A change in relative sea level in these two intervals is due to both eustacy and tectonics.