Global carbon isotopic events in a Campanian–Maastrichtian deltaic succession (Tremp-Graus Basin, Spain) and multiproxy stratigraphy for high sedimentation rate environments

Abstract

The Campanian to Maastrichtian sedimentary succession of the Tremp-Graus Basin (NE Spain) is characterized by the offshore-to-prodeltaic upper Vallcarga Fm giving way to prograding deltaic units (the Aren Fm), which are overlain by transitional facies (the Grey Unit) that correspond to the basal part of the Tremp Group. This work aims to improve the stratigraphical scheme of these deposits using a new dataset of δ13Ccarb and δ13Corg, δ18O and TOC variations through time, supported by a new biostratigraphical analysis and compiling previous biostratigraphical and paleomagnetic data. The comparison of isotopic signals from marine reference sections where δ13Ccarb is well calibrated in the Tethys realm allows recognition of global isotopic events that can be used as correlative marker events. Significant high-frequency δ13C variations defined in the δ13Ccarb are identified in the studied succession despite the different sedimentary setting and some can be related to global geochemical events such as the Late Campanian Event (LCE) and the Campanian–Maastrichtian Boundary Event (CMBE), in good agreement with the magnetic chrons at the base of the Tremp Group, and with some new biostratigraphic constraints. From multiple geochemical and petrographic analysis of the organic matter we suggest that the geochemical signal corresponds to global changes, but at higher resolution, sedimentary dynamics are also reflected in the geochemical signals, particularly inputs of surface water in the deltaic signal.