Facies relations and controls on Artesia Group deposition in the Matador Arch area, Texas
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The Queen and Grayburg Formations of the Texas Panhandle and eastern New Mexico comprise interbedded carbonates, evaporites, and red beds deposited in a shallow epicontinental Permian basin under arid climatic conditions. Carbonates were deposited basinward of evaporites (anhydrite and halite) that were deposited within and along landward margins of regionally extensive (> 28,000 sq. km.), shallow (1-2 meters) brine pools. Siliciclastics comprise flaser-bedded mudstones deposited on mud flats; well sorted, fine-grained, cross-laminated to wind-rippled sandstones deposited as eolian dunes and in interdunal areas; and well sorted, fine-grained, massive sandstones deposited as eolian sand sheets. Along the Matador Arch on the southernmost margin of the Palo Duro Basin, Queen/Grayburg carbonate rocks were deposited within a subsiding trough on the basinward flank of the Matador Arch. Lithofacies mapping based on geophysical and sample logs demonstrates that carbonate facies occur in areas overlying structural depressions on the Arch and along the axis of the northern Midland Basin. Subaqueously precipitated evaporites composed of anhydrite and halite are localized over structural highs on the Arch and dominate Queen/Grayburg non-siliciclastic facies in the Palo Duro Basin north of the Arch. Within the Palo Duro Basin changes in the Queen/Grayburg evaporite facies geographically correspond to underlying structural trends: relatively clastic-free evaporites are concentrated within a northeast-trending broad structural trough bounded on the east and west by structural rises toward clastic source-areas where evaporite facies include a greater component of mudstone. Close correspondence of evaporites and carbonates over structural highs and lows, respectively, along the Arch demonstrates that differential subsidence and uplift influenced bathymetry. The depositional model proposed here places carbonate facies in structural/bathymetric depocenters that maintain better communication with open-marine waters while it places evaporite facies over structural/bathymetric positive features characterized by restricted marine flow and elevated salinities. Bathymetry was probably inherited from topography developed on the pre-transgression landscape by the interplay of subsidence and clastic sedimentation.