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Chemoprovenance of the Chattanooga and Woodford Shales of Oklahoma


Upper Devonian to lower Mississippian Chattanooga and Woodford mudrocks are evaluating in terms of major and trace element concentrations to evaluate the hypothesis of a Laurentian cratonic interior provenance. An alternative provenance might include Acadian/Taconic terranes adjacent to southern midcontinent sector of southern Laurentia. In addition, chemostratigraphic correlation are being considered from exposures along the flanks of Ozark uplift to exposures in the Ardmore area, which are some 175 mi. (282 km.) apart. Samples of terrigenous mudrocks are selected from road cut and quarry exposures to minimize chemical weathering alterations. This study uses a complete set of major elements and up to 32 trace elements and 8 REE from ICP-MS and INAA analysis; previous studies have used a more limited number of elements from XRF analysis. In addition, spectral gamma ray profiles measured across the outcrop exposures is used to evaluate chemical weathering from K/Th ratio and to compare results of this study with other studies. Total organic carbon (TOC) is compared to redox sensitive trace metals with positive correlations indicating element enrichment from marine waters and not necessarily from weathering of provenance terranes. Chemical Index of Alteration (CIA) is assessed against the paleogeographic location (20oS) with values expected for paleoclimates of this latitude, indicating local first cycle sources vs. higher values suggesting far sources of lower latitude and/or recycled sedimentary sources. Various incompatible to compatible element ratios are compared to established petrochemical sources. REE element spider diagrams, and LREE/HREE and Eu-anomaly is also consider for constraining provenance. Although research is progress at this time, it is expected that results will have significant impact on understanding Devonian-Mississippian fine textured sediment dispersal across the southern margin of Laurentia for an important petroleum unconventional resource. In addition, the results can stand as mudrock geochemical standard or reference for pre-Ouachita orogeny of North America.