Temporal influence of carbonate platforms on deep-water siliciclastic deposition, Permian of the Midland Basin, USA

Studies of mixed carbonate–siliciclastic systems’ interactions typically emphasize lateral spatial relationships and the role of siliciclastic source terrains in diluting carbonate production. In contrast, the temporal dynamics between these systems are often oversimplified and remain underappreciated in the depositional record. The southern Midland basin provides a unique opportunity to investigate the influence of antecedent topography of Permian and Pennsylvanian-aged shallow water carbonate banks and their slope deposits on the distribution of younger siliciclastic Permian deep-water basin floor fan systems.

This study utilizes a rich dataset of subsurface well-logs (triple combo dataset ~n = 6000) tied to core observations from 12 proprietary cores through a core-based electrofacies model, and a mosaic of 2D and 3D seismic data. Chronostratigraphic mapping of the basin is achieved on the 3rd order composite sequence scale by integrating all subsurface datasets along with calibration to published biostratigraphic markers from around the region.

Results from this investigation reveal a distinct stepwise filling of the southern Midland basin influenced largely by boundary conditions set in place by carbonate platforms spanning the late Pennsylvanian (Horseshoe Atoll) through the early Permian (Hueco and Glasscock Nose). Basin infill occurred both autochthonously, through eastern and western Wolfcampian–Leonardian carbonate banks, and allochthonously, by siliciclastic sand and silt sourced from the northern Midland basin.

Mapped lithologies of basinal siliciclastics, deposited during periods of low sediment supply, reveal a dominant control on their distribution and routing by the antecedent topography created by the underlying carbonates. The resulting basin floor fan systems are highly confined and display moderate to low aspect ratios. During periods of moderate siliciclastic sediment supply, the buried carbonate banks strongly constrain basin-floor fan systems, confining them to the basin center. These fans remain laterally extensive and display higher aspect ratios than those formed during low-sediment-supply periods. Sediment routing is significantly muted in periods of high sediment supply, resulting in ubiquitous silt and sand deposition across the southern Midland basin, resulting in poorly confined basin floor fan systems with very high aspect ratios.