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

Abstract

The δ13Ccarb profiles of the Vaca Muerta Formation (Neuquén Basin, Argentina), span the Tithonian to lower Valanginian (Jurassic-Cretaceous transition). The investigated interval was sampled from two sections: the Pampa de Tril (PDT, ∼120 m-thick covering the lower Vaca Muerta Formation) and Puerta Curaco (PC, ∼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 δ13Ccarb values that vary from −12.2 ‰VPDB (at the bottom) to 2.9 ‰ VPDB (at the top) and δ18Ocarb values from −13.2 ‰VPDB to −5.3 ‰VPDB. The δ13Ccarb values of the analysed samples, exhibit insignificant correlations with their Mn/Sr (rs = −0.13) and ∑REE (rs = −0.19) counterparts. This supports the preservation of at least near-primary δ13Ccarb compositions that can be implemented to construct a reliable high-resolution carbon-isotope profile for global correlations. The δ13Ccarb profiles of the Vaca Muerta Formation display a negative excursion of ∼8–10 ‰ at the bottom of the formation (Tithonian) which can be correlated with the VOICE (Volgian Isotope Carbon Excursion) event.