Abstract

Wolfcampian (Early Permian) strata in the eastern Delaware Basin consist of an upper siliciclastic member and a lower interbedded detrital carbonate and shale section. The siliciclastic units are interbedded, very fine grained, structureless litharenites and laminated silty shales. These sandstones were transported as bedload by density underflows and deposited on the Permian continental slope. The laminated shales were deposited either by turbidity currents or by fluctatuing bottom currents. The lower Wolfcampian consists of interbedded massive limestone breccias, thin graded packstones and grainstones, and shales. Mud supported debris flows deposited the breccias, while turbidity currents deposited the graded limestones.

Primary intergranular porosity in the Wolfcampian cores is filled by ferroan dolomite and silica cements. Ferroan dolomite was precipitated first as rhombic overgrowths on detrital dolomite sand grains. Pervasive silica cementation destroyed most of the remaining primary porosity. Leaching of rock fragments and feldspars created approximately five percent secondary porosity. Within the carbonate units, ferroan dolomite and ferroan calcite cements filled the low primary porosity. No secondary porosity is present in the carbonates.