Diagenetic constraints in carbon-isotope stratigraphy of the Upper Jurassic-Lower Cretaceous Vaca Muerta-Quintuco system, Neuquen Basin, Argentina: Implications for a global correlation

The delta C-13(carb) profiles of the Vaca Muerta Formation (Neuquen Basin, Argentina), span the Tithonian to lower Valanginian (Jurassic-Cretaceous transition). The investigated interval was sampled from two sections: the Pampa de Tril (PDT, similar to 120 m-thick covering the lower Vaca Muerta Formation) and Puerta Curaco (PC, similar to 670 m-thick covering the entire Vaca Muerta and Quintuco formations). The succession consists of organic-rich marine carbonates alternating with mudrock beds. A multitechnique screening protocol, including petrography and geochemistry, has been applied to evaluate the degree of preservation of the studied carbonates. The Pampa de Tril and Puerta Curaco sections have delta C-13(carb) values that vary from -12.2 parts per thousand VPDB (at the bottom) to 2.9 parts per thousand VPDB (at the top) and delta O-18(carb) values from - 13.2 parts per thousand VPDB to -5.3 parts per thousand VPDB. The delta C-13(carb) values of the analysed samples, exhibit insignificant correlations with their Mn/Sr (r(s) = -0.13) and Sigma REE (r(s) = -0.19) counterparts. This supports the preservation of at least near-primary delta C-13(carb) compositions that can be implemented to construct a reliable high-resolution carbon-isotope profile for global correlations. The delta C-13(carb) profiles of the Vaca Muerta Formation display a negative excursion of similar to 8-10% at the bottom of the formation (Tithonian) which can be correlated with the VOICE (Volgian Isotope Carbon Excursion) event. (c) 2023 Elsevier Ltd. All rights reserved.