COUPLED CHANGES IN EARLY CRETACEOUS CARBON CYCLING AND WEATHERING PATTERNS: EVIDENCE FROM INTEGRATED ISOTOPE AND SANDSTONE RECORDS OF THE ALPINE TETHYS

In this study we investigate if a major perturbation of the Early Cretaceous carbon cycle was accompanied by altered weathering and erosion rates. The large Aptian carbon isotope anomaly records the response of the biosphere to widespread volcanic activity and probably resulting changes in atmospheric carbon dioxide concentration. Elevated pCO2-levels should also result in an accelerated hydrological cycle and increased silicate weathering, creating a negative feedback loop removing CO2 from the atmosphere. We propose to interpret the widespread occurrence of quartz sandstones in the Tethys--Atlantic seaway as a result of altered weathering and erosion rates in the wake of the Aptian carbon cycle excursion. We challenge the traditional notion that these are "flysch" deposits associated with Early Cretaceous orogenic movements in the western Tethys. We propose that these sandstones have most likely been part of a large conveyor belt system, acting along the Iberian and European margin of the Tethys seaway. Using chemostratigraphic correlations, we shows that the activity of this system was only short lived and coeval with the Aptian carbon-cycle perturbations. We tentatively relate the existence of this system to a transient climate regime, characterized by fluctuating pCO2-levels.