A Southern Hemisphere Chronostratigraphic Framework for the Pliensbachian–Toarcian Carbon Cycle Perturbations

Lower Jurassic sedimentary successions from the Neuquén Basin, Argentina are unique in the abundance of radiometrically datable material (ash-beds) present, which can be tied to bio- and chemostratigraphic (carbon-isotope) zonations. Here, we present new U-Pb radio isotopic dates, integrated with carbon-isotope and Hg/TOC data, from three localities in Argentina (Arroyo Lapa, Arroyo Serrucho/Las Overas and Chacay Melehue) to generate a biostratigraphically calibrated composite carbon-isotope curve and geochronological framework for the Pliensbachian–Toarcian transition in South America. Using a Bayesian framework we present an age-depth model for this composite record and estimate the age and duration of key intervals extending from the Latest Pliensbachian carbon isotope excursion (CIE) through the Early Toarcian negative CIE. Using a  statistical analysis of all available Karoo and Ferrar Large Igneous Province (LIP ) U-Pb and Ar-Ar radioisotopic ages we create a timeline of the key events and examine the timing of the carbon cycle perturbations specifically looking at potential links to peaks of extrusive emplacement of the Karoo and Ferrar LIP. The geochronological framework is further compared with other available radioisotopic dates from correlative sections, allowing for a more precise constraint and validation of the timing and duration of these Early Jurassic events.