Salt diapir-influenced, shallow-marine sediment dispersal patterns: Insights from outcrop analogs

Abstract

Unique outcrop exposures of two salt diapirs, a secondary salt weld, and associated syndiapiric strata in northeast Mexico offer an important perspective on salt-influenced petroleum reservoirs by allowing recognition and description of salt-related sandstone depocenters. Spectacular progressive unconformities and halokinetic sequences, coupled with laterally continuous exposures, permit accurate correlation and interpretation of syndiapiric units. Analysis of the syndiapiric Upper Cretaceous, Delgado Sandstone Member (Potrerillos Formation) delineates regional shoreline sediment dispersal locally impacted by diapiric relief and the distribution and internal character of salt diapir-proximal sandstone depocenters. Sequence-stratigraphic correlation defines striking relationships between highstand (HST) and transgressive systems tracts (TST), stratal thinning trends, and salt diapir relief. Transgressive systems tract and highstand systems tract strata show thinning and lithofacies shoaling trends toward diapirs; however, the latter is more pronounced in the HST and occurs at a greater distance from salt diapirs (within 1–2 km [0.6–1.2 mi]). Sandstone depocenters, roughly 0.5–1.0 km (0.3–0.6 mi) wide and 0.5–0.2 km (0.3–0.1 mi) thick, are present in both TST and HST strata and consist of sandier, shallower water facies. However, depocenters are better developed in TST strata as thicker stratigraphic sections on updip diapir margins. We propose that sandstone depocenters formed by preferential sediment reworking and shelf ridge development on landward diapir margins during marine transgression. Elevated diapir relief and higher subsidence rates adjacent to salt diapirs likely enhanced this process. Additionally, depocenters adjacent to El Papalote diapir are smaller and contain deeper water facies than the age-equivalent depocenters adjacent to El Gordo diapir, suggesting that it had higher, broader sea-floor relief.