ABSTRACT: Facies Analysis of Strawn Submarine Fan Complex, Fort Worth Basin, Central Texas

Matt J. Pranter

The Fort Worth basin is a Paleozoic foreland basin located in central Texas. The basin developed in direct response to the tectonic evolution of the Ouachita thrust belt. Fan delta, submarine fan, and related slope depositional systems comprising the lower Strawn Group were deposited within the Fort Worth foreland basin and platform and shelf-edge carbonates developed on the adjacent Concho platform.

The Ouachita thrust belt and related structural highlands served as the principal source areas for the thick accumulation of lower Strawn submarine fan sequences. The nature and distribution of depositional environments were controlled by active subsidence within the Fort Worth basin. Both sediment loading and tectonic loading following thrust-sheet propagation were major contributors to basin subsidence.

The most rapid subsidence within the Fort Worth basin occurred during the early and late Atokan and continued into the early Desmoinesian. Decreasing subsidence and sedimentation rates during the late Desmoinesian and early Missourian established a setting for the development of upper Strawn fluvial and deltaic systems, which eventually prograded across the Fort Worth basin.

Several cycles of fan progradation and abandonment are represented within the lower Strawn. The lower Strawn delta-fed submarine fan turbidites were deposited at the base of the slope forming an aggrading ramplike depositional feature. Individual facies recognized in outcrop and within the subsurface include fan delta, prodelta slope, proximal ramp, and distal ramp facies. Sandstone geometries and sediment distribution patterns reflect this ramplike feature.

AAPG Search and Discovery Article #90096©1990 AAPG Southwest Section Meeting, Wichita Falls, Texas, March 11-13, 1990