Use of Sequence Stratigraphy to Define Stratigraphic Plays in Upper Pennsylvanian and Lower Permian Lowstand Systems Tracts, North-Central Texas

L. F. Brown, Jr.

Sequence stratigraphic interpretation of the Virgilian and Wolfcampian Series, Eastern shelf and adjacent Midland basin, provides new insight into stratigraphic-trap potential in this intensively drilled cratonic basin. Research and application of depositional sequence and systems tract concepts, derived from seismic-stratigraphic analyses of worldwide passive-margin basins, provide new interpretive models to support significant reexploration of this and similar basins. Recognition, correlation, and mapping of 16 third-order, mostly type 1 cyclic sequences permit delineation of possible new stratigraphic-trap plays within lowstand depositional systems tracts. Application of these concepts provides a new perspective of basins in which most traditional plays have been explo ted.

Analysis of 22,000 mi², based on 2,000 mi of cross sections, 5,000 wells, and extensive outcrop data, clearly delineates sequences composed of (1) lowstand incised valley, deltaic, leveed slope, and basin-floor fan tracts, (2) retrogradational (transgressive) shelf carbonate tracts, and (3) highstand fan-deltaic, fluvial-deltaic, and interdeltaic tracts. Paleogeographic maps of the terrigenous systems tracts document a cyclic depositional history of the region controlled by combined tectonism and eustasy. The sequence model infers lowstand plays composed of coastal-onlap pinch-out of deltaic systems basinward of shelf edges, incised valley and submarine canyon-fill traps, and basin-floor fans related to canyon erosion. Results of several decades of research on terrigenous d positional systems in this region, when combined with rapidly evolving ideas derived from seismic sequence analysis, may provide a renewed thrust for stratigraphic prospecting in north-central Texas.

AAPG Search and Discovery Article #91026©1989 AAPG Southwest Section, March 19-21, 1989, San Angelo, Texas.