Brian Romans¹, Michael H. Gardner¹

(1) Colorado School of Mines, Golden, CO

ABSTRACT: Reconstructing the Permian Paleogeography of the Brushy Canyon Formation, West Texas

The paleogeography of the Permian basin of West Texas has remained relatively unchanged since P.B. King published the first map in 1942. This reflects the accuracy of the original reconstruction and the abundant outcrop and subsurface data that constrain it. The western margin of the Delaware Basin, the western sub-basin of the Permian Basin, represents the most speculative part of this paleogeography. Eocene extensional tectonism and formation of the Salt Basin graben overlaps the western margin of the Permian Delaware Basin. Tertiary structuring introduces uncertainty regarding the Permian shelf margin trend and configuration and consequent basinal clastic sediment dispersal along the western margin of the Delaware basin. Detailed study of the Brushy Canyon outcrop belt establishes sediment dispersal patterns that can be extended updip toward the shelf margin to the north and west and to the subsurface to the east. Sporadic outcrops in the graben, 2D seismic, gravity maps, and wells in the graben and in the area 25 miles east of the outcrop belt, provide a better reconstruction of the western margin of the Delaware Basin. A grid of northwest-southeast and west-east trending subsurface-outcrop-subsurface cross sections parallel the principal sediment transport trends determined from outcrop. These cross sections are compared to the north-northwest trending regional outcrop cross-section. This comparison illustrates how the architecture and distribution of clastic sediment bodies are dependent upon proper depositional dip and strike projections. Fan-scale isopach maps of the Brushy Canyon Formation illustrate along-strike changes in sediment dispersal across the western margin. Subsurface data in the graben better constrain the configuration of a complex and embayed carbonate shelf margin.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado