SEDIMENTOLOGICAL CHARACTER AND DEPOSITIONAL ENVIRONMENTS OF THE PERMIAN QUEEN FORMATION, EASTERN SHELF, WEST TEXAS

The Permian (Guadalupian) Queen Formation of West Texas consists of a complex suite of siliciclastics, carbonates, and evaporites deposited within and marginal to the Permian Basin. Sediment deposition is aggradational and indicative of a Middle Permian highstand. Vertical facies changes are probably the combined result of uninhibited lateral shifting of channels and high frequency base-level changes. Based on stratal patterns in core sediments and petrophysical logs, two facies and two facies complexes have been identified. Facies 1 is characterized by alternating (<1 m thick) very fine-grained sands and clayey silts with bedded anhydrite layers. Enterolithic anhydrite is common within or just below these sediments and primary sedimentary structures are highly haloturbated; dewatering features are also common. Facies 1 represents ephemeral lake or playa deposition. Facies 2 is rare in the study area and consists of inclined beds <1.5 m thick dominated by well sorted, very fine-grained sandstones. Facies 2 represents eolian deposition in the form of small isolated dunes. Facies Complex A is characterized by upward-fining cycles; thicknesses range from 3-12 m. Grains sizes range from sand with rip-up clasts (channel) through clay-rich mud (overbank). Bedded anhydrite may cap these cycles and represent the transition to the playa facies. Primary sedimentary structures include continuous/discontinuous wavy and planar laminae, scour surfaces, ripple cross laminae, and graded bedding. This complex is interpreted to have been deposited in an ephemeral stream (wadi) environment. Facies Complex B is characterized by upward-coarsening sediment packages; more distal cycles of the complex are represented by much thinner sediment packages (1.5-3 m) than those more proximal cycles (3-9 m). Grains range from clay-rich silts and/or bedded anhydrite at the bases through medium-grained sands near the tops of the cycles; distal deposits are finer grained than proximal deposits. Primary sedimentary structures include continuous/discontinuous wavy laminae and cross laminae. Facies Complex B is interpreted to have been deposited by a wadi fan system. Overall, sediment packages are primarily aggradational, but higher frequency retrogradational packages may be present implying small paleoclimatic perturbations.