Diagenetic examination and isotopic study of exposure surface in the Glen Rose Formation, early Cretaceous, central Texas




Toktas, Nargul

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The aim of this study is to examine the diagenesis and describe paragenetic sequences of exposure surfaces in the Lower Cretaceous Glen Rose Formation with the goal of identifying early meteoric oxygen isotopic compositions. The study area includes numerous sites located in south to north central Texas. The study employed petrographic studies that included use of Alizarin Red-S stained thin sections, petrographic microscopy, and cathodoluminescence microscopy. Micritization, cementation, dolomitization, dissolution and neomorphism, compaction, and fracturing were seen as diagenetic features. This petrographic information guides the sampling of different carbonate phases for carbon and oxygen isotopic analyses. In general; micritization, dissolution and neomorphism, cementation are present in eogenesis. Oxygen isotope values range from -5.94 / to 0.52 / (vs. VPDB), whereas the carbon isotope values range from -2.21 / to 3.78 / (vs. VPDB). Oxygen isotope values primarily represent marine compositions as opposed to meteoric, though the lightest values could represent early meteoric diagenesis. Using a latitudinal temperature gradient and the lightest δ 18 O end members, meteoric δ18 O values were calculated.


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Cathodoluminescence, Diagenesis, Early Cretaceous, Glen Rose, Petrography, Stable Isotopes