Subsidence analysis of the Northwest Shelf of the Delaware Basin: Implications for the initiation and movement of the late Paleozoic Pedernal Uplift

The Northwest Shelf of the Delaware Basin is a prominent geologic feature within the greater Permian Basin Province of southeast New Mexico and west Texas. Structural development of the Permian Basin Province is typically described in three phases. Concurrent with the second phase of development, the Pennsylvanian to early Permian Ancestral Rocky Mountains (ARM) orogenic event refers to the pervasive intraplate deformation of western Laurentia, generally consisting of Precambrian-cored basement uplifts offset from asymmetric sedimentary basins by high-angle reverse faults. Problematic to understanding ARM deformation is a lack of usable age control and tectonic overprinting across the orogen. However, requisite regional stage-scale fusulinid biostratigraphic control and limited tectonic overprinting of the Delaware Basin makes this an ideal region to investigate tectonic subsidence related to ARM deformation. Results from this study indicate peak rates of tectonic subsidence occurred during the Cisco Stage. Along the shelf and in the basin, cumulative tectonic subsidence and decompacted thickness both increase to the southwest consistent with proximity to the Pedernal Uplift. Initiation of the Delaware Basin by the Early Pennsylvanian and declining tectonic subsidence rates from the Late Pennsylvanian to early Permian correlate well with similar studies of the Midland and Orogrande basins. Results from this study generally coincide with the current understanding of the initiation and movement of the Pedernal Uplift. However, flexural response to a fixed load related to thrust faulting along the eastern margin of the uplift likely contributed to tectonic subsidence of the Northwest Shelf and Delaware Basin. Furthermore, comparison of tectonic subsidence curves for the Orogrande and Delaware basins suggests the eastern margin of the uplift may have been more active during the Early Pennsylvanian and early Permian. In relationship to other basins of the ARM, subsidence analysis of the Delaware Basin concurs with a relatively synchronous initiation of tectonic subsidence across the orogen during the Early Pennsylvanian, culminating in peak rates of tectonic subsidence by the Late Pennsylvanian that declined significantly in magnitude by the early Permian.