Abstract: Depositional Facies and Environments of the Lower Mineral Wells Formation of the Pennsylvanian Strawn Group in North Central Texas

Susan E. Bradshaw, James M. Mazzullo

The lower Mineral Wells formation of the Strawn group is a siliciclastic-dominated sequence of cyclically interbedded mudstones, sandstones, and carbonates that was deposited in fluvial, deltaic, interdeltaic, and inner shelf environments on the Eastern Shelf of the Midland Basin during late Desmoinesian and early Missourian time. This study examined outcrops of the formation in Palo Pinto and Parker Counties in north central Texas. The purpose of this study is to describe and interpret the facies, depositional environments, and stratigraphy of the formation.

Seven depositional facies have been identified. Point bar facies have a scoured basal contact and consist of massive sandy chert conglomerate overlain by trough cross-bedded and rippled sandstone. Active distributary channel facies consist of bioturbated and cross-bedded sandstones. Interdistributary swamp facies consist of platy mudstones with paleosols and abundant plant fragments. Interdistributary bay crevasse splay facies consist of graded bioturbated muddy sandstones. Transgressive shoreface facies have a sharp basal contact and consist of sandy fossiliferous carbonates and cross-bedded fossiliferous mud-draped sandstone overlain by bioturbated muddy sandstone. Prodelta facies consist of massive, occasionally laminated and sparsely fossiliferous, silty mudstones. Open marine fac es consist of highly fossiliferous mudstones.

The stratigraphy of the Mineral Wells formation is characterized by alternating progradational and transgressive sequences. Progradational sequences consist of vertical successions from

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas