ABSTRACT: Patterns of reciprocal sedimentation with Middle and Late Pennsylvanian carbonate-bank systems, Eastern Shelf of North-Central Texas

CLEAVES, ARTHUR, W.

The Middle and Late Pennsylvanian Concho Platform/Eastern Shelf was a region of mixed carbonate and siliciclastic deposition that exhibited four distinct patterns of reciprocal sedimentation. The carbonate component of these patterns includes: (1) a middle Desmoinesian ramp system with shelf interior banks and patch reefs, (2) late Desmoinesian Anson accretionary shelf-margin bank, (3) Missourian accretionary double bank complex, and (4) the Virgilian progradational and aggradational Sylvester shelf-margin bank system. Tectonism on the shelf and in adjacent basins determined the distribution of individual carbonate systems through time, whereas eustatic sea level change cycles controlled carbonate accretion, progradation, and porosity formation by means of meteoric diagenesis.

Carbonate accumulation on the ramp and Sylvester bank systems was largely restricted to the transgressive systems tract. Progradational delta systems reached the outermost shelf during lowstands and complete drowning was obtained with maximum transgression. Virgilian shelf margins were displaced basinward by the formation of siliciclastic lowstand wedges that served as the substrate for the next shelf-edge bank. Neither the Anson nor the Missourian shelfmargin banks prograded the shelf edge, due to a lack of active deltaic sedimentation on the outer shelf. Because the Missourian shelf was completely carbonate-dominated, the outer bank underwent upbuilding during the stable lowstand and transgressive portions of a cycle. The inner bank accreted during stable highstands and underwent minor progradation. Production from carbonate systems is obtained largely from Desmoinesian and Missourian shelf-edge banks, basin-margin pinnacles, and from age-equivalent portions of the Horseshoe isolated platform.

AAPG Search and Discovery Article #90947©1997 AAPG Southwest Section Meeting, San Angelo, Texas