parker and palo pinto plays:
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.
Basin-Centered Tight Gas Sands and Thrust Faulting in Central Parker County of the Fort Worth Basin: Jimmy D. Thomas
The Fort Worth Basin formed during Early and Middle Pennsylvanian due to the oblique collision of the Afro-South American and North American plates. This tectonic activity not only affected deposition at that time but also affected the underlying formations. Depositional environments changed from shelf carbonates to shallow marine to deep marine then back to shallow marine during basin development. Eustatic cycles combined with tectonic activity have complicated mapping efforts and led to many misunderstandings about the basin. Much of the basin center is unexplored and has potential for enormous gas reserves. Reservoir mapping of just the basin-centered tight gas sediments indicate natural gas reserve potential in the tens of TCF. Is this another giant reservoir that can be "gas-farmed" much like the Barnett Shale?
A four-hundred-foot throw thrust fault extends through southern Parker County with open hole logs indicating repeat sections in the Barnett Shale, Atoka and Strawn formations. Due to the cyclicity of sediments during this time, most of these repeat sections can be mapped as separate deposits. It is also believed that due to the oblique collision of the plates, lateral fault movement and faults of different orientations complicate the understanding of tectonics during this time. This tectonic activity has the potential to have created additional "sweet spots" in the Barnett Shale similar to the Newark East gas field. Faulting and fracturing may have created potential permeability enhancement and hydrocarbon traps in the Ellenburger and Marble Falls making these formations exploration and development targets. Due to a lack of drilling, very little is known about these formations in most of the basin. The Fort Worth Basin is a new exploration frontier for combining the advances in geology and engineering technologies.
