Southwest Section AAPG Annual Convention

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Using fusulinid biostratigraphy to reconstruct the Pennsylvanian-early Permian history of the Midland Basin


This project aims to reconstruct the Pennsylvanian-early Permian sediment infill history of the Midland Basin. 2,400 wells span across twelve counties comprising the majority of the basin. Each well contains fusulinid depth occurrences that allow for mapping of five biostratigraphiz zones, namely the Wolfcampian, Canyon, Cisco, Strawn, and Lower Strawn. Manipulation of the biozone data to depths below sea level allows for construction of regional chronostratigraphic surfaces that demonstrate the geometry of the basin at the end of the specific time interval. Substraction of two chronostratigraphic surfaces results in regional isopach maps.

Preliminary analysis of the Northwest corner of the Midland Basin shows shelf edge aggradation during the Pennsylvanian and progradational movement during the Permian. Our results agree with previous depositional models of the shelf edge in this region. The southeastern margin of the Midland Basin demonstrates shelf aggradation in the Lower Strawn, Upper Strawn, and Canyon intervals, but strong progradation through the Wolfcampian and Leonardian. Some inferred shelf edges on our chronostratigraphic maps moved in excess of 15 kilometers farther into the basin than other workers shelf edge interpretations potentially suggesting larger progradation in the southeastern margin in the early Permian than previously mapped. Regional isopach maps demonstrate the evolution of the Horseshoe atoll in the Pennsylvanian and subsequent burial through shelf edge progradation in the Wolfcampian. Isopach thickness of the Wolfcampian in general shows thickest accumulations of strata along the eastern shelf of the Midland basin, but localized thick zones occur in the basin center and may represent regions of shelf edge bypass. Further work looks to include counties to the north that extend the ability to map surfaces across the Matador arch and into the Palo Duro basin.