Correlation problems, lower part of the Canyon Group (Upper Pennsylvanian), western Wise County, Texas

By

Merlynd K. Nestell and Rustin A. Kimbell, Department of Geology, University of Texas at Arlington, Arlington, TX 76019.

Scattered, often poorly exposed, strata that can be correlated with the Upper Pennsylvanian Palo Pinto and Posidion formations (Lowery, 1962), Canyon Group, Brazos River Valley, occur in western Wise County, Texas. These northwest dipping rocks are unconformably overlain and often obscured by southeast dipping Lower Cretaceous (Comanche Series) sand and conglomerate. In the early 1900’s, Bose, Plummer and Moore, and Scott and Armstrong proposed several names for these Pennsylvanian limestone strata (Bridgeport, Hudson Bridge, Martin Lake, Balsora, Sanders Bridge, Boone Creek, and Willow Point), mostly with brief descriptions and poorly located type sections.

Examination of exposures of these strata and their contained fusulinid and conodont faunas has demonstrated that (in descending order): (i) a conodont rich black mudstone (indicating maximum flooding) in the base of the Wolf Mountain Shale and just above the Wiles Limestone correlates to a similar interval just above the Willow Point Limestone, well exposed in the area around the south side of Lake Bridgeport; (ii) the Willow Point Limestone (= Bridgeport Limestone, no longer used) correlates to the Wiles Limestone (top of the Posideon Formation, Brazos River Valley); (iii) a conodont rich black mudstone present in the middle part of the Posideon Formation correlates to equivalent age strata in the Martin Lake area just south of Bridgeport; (iv) the Martin Lake (= Balsora) Limestone (fusulinid/algal grainstone indicating very shallow marine sediments) correlates with the top part of the Palo Pinto Formation; (v) the Sanders Bridge Limestone  correlates with the middle part of the Palo Pinto Formation; (vi) the Hudson Bridge (= Boone Creek) Limestone correlates with the lower part of the Palo Pinto Formation.

AAPG Search and Discovery Article #90010©2003 AAPG Southwest Section Meeting, Fort Worth, Texas, March 1-4, 2003