ABSTRACT
The depositional processes responsible for Permian fine-grained basinal deposits are highly debatable. In this study, we use cores and fine-scale subsurface mapping to demonstrate sediment delivery pathways, sedimentary facies, and the depositional model of postorogenic sedimentation of Dean formation in the Midland Basin, western Texas. The most distinct feature of the Dean formation is its thin-bedded (0.6–5 m), laterally continuous, large-scale sheet deposition (length: 35–113 km; width: 30–70 km). Sheet sandstone distribution was confined by basin topography. Dean sheet sandstones show great similarities to the outcrop-based Miocene Marnoso Arenacea Formation in the Apennines (Italy) with regard to grain size, formation thickness, sandstone-bed thickness, and sheet dimensions. These similarities were used to constrain the chronostratigraphic correlation of large-dimension sheet sandstones using wire-line logs. Our results demonstrate that Dean basinal sediments were mainly delivered by subaqueous processes, although time-equivalent sediments on the shelf and platform (small part) may have been delivered by eolian processes. This is a refinement of the “eolian-marine” model previously proposed for the Permian Delaware Mountain Group in western Texas. It is different from the Sahara dust depositional model (eolian fallout maximum during peak glaciation and fluvial influx maximum during climatic optimum). This study adds to our understanding of fine-grained sediment delivery, deep-water sedimentary geology, and reservoir geology of the Midland Basin and serves as an analogy for other fine-grained systems worldwide.
