Competing Influences of Ancestral Rocky Mountain Tectonism and Glacioeustatic Forcing during the Late Paleozoic Ice Age; Oro Grande and Permian Basins, USA

Determining the role of tectonic and eustatic regime variables is an important step in understanding the evolution of ancient depositional systems and predicting degrees of heterogeneity and facies stacking patterns. For the Late Carboniferous (Pennsylvanian) of the Oro Grande and Permian basins, analysis of regime variables is made challenging by the competing influences of the Ancestral Rocky Mountain orogen (ARM) and the peak glacioeustatic forcing of the Late Paleozoic Ice Age (LPIA). World-class three-dimensional exposures from the Sacramento Mountains of southeastern New Mexico, and an extensive core, wireline log, and 3D seismic database from the Horseshoe Atoll, Midland Basin, combine to permit a 4D analysis of both regime variables, as well as their changing influence across the approximate 30 ma time interval (322.8–290.1 ma). Outcrop measured sections and bed tracing as well as structural analysis, LiDAR, and drone imagery, constrained by fusulinid biostratigraphy, are used to document the evolution of the Oro Grande/Pedernal system (Gobbler, Beeman, Holder, Bursum, and Abo formations). Permian Basin equivalents include the Morrowan–Atokan valleys succeeded by Strawn, Canyon, and Cisco retrograding platforms (Delaware and Midland basins). Across both OG and DB systems, throughgoing changes in architecture and heterogeneity of reservoir-scale facies and stacking patterns suggest a dominant role of LPIA eustatic forcing. A clear shift to increasing magnitude of facies tract offset occurs across the Desmoinesian–Missourian boundary, while a combination of high-amplitude eustasy and biotic/climatic influences drives key differences in reef construction and lateral facies variability across the Missourian–Virgilian boundary in both basins. At the platform scale, compressional faults drive uplifts that control the location of entire platforms and siliciclastic fairways.