Middle and late Pennsylvanian rocks, North-Central Texas
The middle and late Pennsylvanian (Desmoinesian-Missourian) section of north-central Texas is illustrated by a transect extending from eastern Parker County northwestward to northeastern Palo Pinto County (Fig. 1).
The transect begins in the Dobbs Valley Member of the Mingus Formation (middle Strawn Group, Desmoinesian; Localities 1 and 2) and crosses through the Brazes River Formation and Mineral Wells Formation (upper Strawn Group, Desmoinesian- Missourian; Localities 3 and 4), Palo Pinto Formation, Wolf Mountain Shale, and into the Winchell Limestone (Canyon Group, Missourian; Localities 5 and 6; Figs. 1, 2).
Strawn and Canyon reeks generally reflect the cyclic depositional nature of the Pennsylvanian. The vertical succession of these rocks illustrates the final filling of the Fort Worth Basin and cyclic fluvial/deltaic progradation and marine transgression of the epeiric sea over the Eastern Shelf (Fig. 3). A shelf edge into the Midland Basin developed in Missourian time. Slope and basin depositional systems are recognized in the subsurface in Missourian and Virgilian time. Sources for the clastics were the Quachita Mountains and Southern Oklahoma Mountains. This transect illustrates some of the major elastic and carbonate depositional systems in the Strawn and Canyon Groups.