Platform-Scale Depositional Architecture Control on Slope and Basinal Facies Distribution—Insights from the Wolfcampian–Leonardian Succession of the Midland Basin, Texas

Linkages between shelfal carbonate factories and their equivalent basinal deposits are commonly obscured because of complex autogenetic-dominated processes controlling sediment transport into the basin. Allogenic processes, such as climate, sea-level, and faunal evolution, influence the amount and type of carbonate sediment produced; which drive slope and basinal depositional patterns. This study investigates how shelfal platform evolution during the Wolfcampian through Leonardian (Permian) influences slope and basin depositional architectures in the Midland basin of west Texas.

A statistical relationship was derived between borehole logs and core descriptions to produce a core-calibrated electrical facies model. The resulting categorical decision tree identified ten unique electrical facies that were propagated to ~6000 wells with triple combo logs (GR, NPHI, LLD, RHOB) across the Midland basin.

Results revealed a large-scale evolutionary trend of slope and basinal deposits across the Midland basin in response to changing carbonate factories on the surrounding shelves. Throughout the Wolfcampian, basin-centered deposits were dominated by siliciclastic mudrocks derived from distal terrigenous sources, while shelf margins were dominated by deep oligotrophic microbial boundstone factories. A secular shift to carbonate mudstone-dominate basin center deposits is observed during the Leonardian succession, coupled with a transition to shallow euphotic framestone reef systems along the margins and volumetrically significantly more carbonate sediment gravity flow deposits along the slopes.

The statistical combination of electrical logs provides a window into the evolution of slope and basin-centered deposits through two 2nd order super sequences spanning the Wolfcampian and Leonardian (L1–L6) epochs. The secular trend and lateral linkage from shelf-to-basin, highlighted by the electrical facies model, provides a tool for understanding source to sink processes. This approach aids in furthering our understanding of how these processes manifest in mixed carbonate–siliciclastic systems.