Detrital-zircon analyses, provenance, and late Paleozoic sediment dispersal in the context of tectonic evolution of the Ouachita orogen

New analyses for U-Pb ages and εHft values, along with previously published U-Pb ages, from Mississippian–Permian sandstones in synorogenic clastic wedges of the Ouachita foreland and nearby intracratonic basins support new interpretations of provenance and sediment dispersal along the southern Midcontinent of North America. Recently published U-Pb and Hf data from the Marathon foreland confirm a provenance in the accreted Coahuila terrane, which has distinctive Amazonia/Gondwana characteristics. Data from Pennsylvanian–Permian sandstones in the Fort Worth basin, along the southern arm of the Ouachita thrust belt, are nearly identical to those from the Marathon foreland, strongly indicating the same or a similar provenance. The accreted Sabine terrane, which is documented by geophysical data, is in close proximity to the Coahuila terrane, suggesting the two are parts of an originally larger Gondwanan terrane. The available data suggest that the Sabine terrane is a Gondwanan terrane that was the provenance of the detritus in the Fort Worth basin. Detrital-zircon data from Permian sandstones in the intracratonic Anadarko basin are very similar to those from the Fort Worth basin and Marathon foreland, indicating sediment dispersal from the Coahuila and/or Sabine terranes within the Ouachita orogen cratonward from the immediate forelands onto the southern craton. Similar, previously published data from the Permian basin suggest widespread distribution from the Ouachita orogen. In contrast to the other basins along the Ouachita-Marathon foreland, the Mississippian–Pennsylvanian sandstones in the Arkoma basin contain a more diverse distribution of detrital-zircon ages, indicating mixed dispersal pathways of sediment from multiple provenances. Some of the Arkoma sandstones have U-Pb age dis­tributions like those of the Fort Worth and Marathon forelands. In contrast, other sandstones, especially those with paleocurrent and paleogeographic indicators of southward progradation of deposi­tional systems onto the northern distal shelf of the Arkoma basin, have U-Pb age distributions and εHft values like those of the “Appalachian signature.” The combined data suggest a mixture of detritus from the proximal Sabine terrane/Ouachita orogenic belt with detritus routed through the Appalachian basin via the southern Illinois basin to the distal Arkoma basin. The Arkoma basin evidently marks the southwestern extent of Appalachian-derived detritus along the Ouachita-Marathon foreland and the transition southwestward to overfilled basins that spread detritus onto the southern craton from the Ouachita-Marathon orogen, including accreted Gondwanan terranes.

Interpretation of Paleozoic paleokarst features in the Arkoma Basin of Oklahoma using 3D seismic and well logs

Paleokarst regions worldwide are repositories for hydrocarbons, mineral deposits, and groundwater. Time structure maps were generated for the Ordovician Viola Limestone, Mississippian Caney Shale, and Pennsylvanian Jefferson Sandstone and Wapanucka Limestone. Isochron maps indicate pronounced visible sinkhole time thickening in the Viola-Caney and Caney-Jefferson intervals relative to the Jefferson-Wapanucka. Sinkhole features in the Viola exhibit mappable structural depression, characterized by lower positive amplitude, higher seismic variance, and most-negative curvature. Curiously, spatially coincident sinkhole features in the shallower Wapanucka display the opposite characteristics relative to adjacent areas that have not been modified, namely, higher positive amplitude and lower seismic variance with no mappable time structure relief. Seismic amplitude analysis based on well logs and Gassmann modeling indicate that the Viola has a reduction in limestone acoustic impedance inside sinkholes that allows estimation of increased porosity near 10%. Identical analysis for the Wapanucka suggests that no reasonable alteration of the limestone acoustic impedance alone can account for the observed amplitude behavior, implying that the limestone and overlying shale must be altered in sinkhole areas. Some of these interpreted sinkhole features coincide with vertical pipe structures with up to 490 m (1610 ft) vertical extent, diameter up to 520 m (1700 ft), and separation of at least 460 m (1510 ft). We interpret the Viola sinkhole features and associated vertical pipes to be part of a mature epigene karst system. Conversely, the shallower and more subtle Wapanucka sinkholes we interpret as related to an immature mixed karst system with epigene and hypogene elements. Our study indicates for the first time the seismic evidence of pipe features that extend both below and above the Viola and the presence of Wapanucka sinkhole features in the Arkoma Basin of Oklahoma, which provides a better understanding of paleokarst occurrence and its possible impact on resource exploration.