CARBON-ISOTOPES AND CALCAREOUS NANNOFOSSILS, CLUES FOR EARLY JURASSIC MARINE PALAEOENVIRONMENTS IN THE NEUQUÉN BASIN

CHAUMEIL RODRÍGUEZ, MICAELA; PÉREZ PANERA, JUAN PABLO; SPANGENBERG, JORGE E.; GÓMEZ DACAL, ALEJANDRO R.; SUAN, GUILLAUME; MATTIOLI, EMAUELA

Budapest

Congreso; 11th International Congress on the Jurassic System; 2022

The study of global climate changes impacting past marine communities is pivotal to model the paleoenvironments and understand the development of present-day ecosystems as well as the possible threats associated with anthropogenic activities. Ocean Anoxic Events (OAEs) are often associated with hyperthermals and are related to rapid perturbations of the carbon cycle impacting the biosphere. The Toarcian Oceanic Anoxic Event (T-OAE) is one of the most important hyperthermal of the Jurassic Period. It has been studied in detail in several European basins and the Maghreb section of North Africa. Comparatively, little is known from localities in the Southern hemisphere.The Neuquén Basin in Argentina is one of the few places in southwestern Gondwana where the T-OAE has been recorded and has the potential to shed light on its global extent. Los Molles Formation in the Neuquén Basin is the expression of the first marine transgression from the Pacific Ocean in the Early to Middle Jurassic and yields a continuous and rich record of calcareous nannofossils. We present the results of a first multidisciplinary study integrating geochemical (13Ccarb, TOC, major and trace elements) and calcareous nannofossil data from a novel southern section in the Neuquén Basin. The primary aim of the study was to identify marine perturbations with precise biostratigraphic control. The combined data set allowed the identification of the T-OAE besides four additional significant isotope excursions distributed across the Pliensbachian-Bajocian interval. This new geochemical and calcareous nannofossils record is the most time-extended and continuous in the Neuquén Basin and the southwestern Gondwana. Our contribution highlights the global extension of the T-OAE and other Early to Middle Jurassic isotope excursions, and the utility of combining carbon isotopes and calcareous nannofossils for global age correlation and paleoenvironmental reconstructions and evaluation of the marine community response to major long-term environmental changes.