| Summary: | This Ph.D. research project investigated two paleo-environmental dynamics under extreme Mesozoic carbon cycle and climate perturbations evidenced by major anomalies in the carbon isotope record (δ13C) of the Early Jurassic and Early Cretaceous, namely the Toarcian Ocean Anoxic Event (TOAE) and the Valanginian Weissert Event, respectively. The material selected for the study of the T-OAE is from two new cores (Sogno and Gajum), which represent pelagic deepest records (1000-1500 paleowater depth) of the Lombardy Basin (Southern Alps, Italy). Both cores record an expanded black shale interval (the Fish Level) of 5 m and 16 m at Sogno and Gajum, respectively, representing the lithostratigraphic expression of the T-OAE sensu Jenkyns (1985, 1988). The Fish Level correlates with the early Toarcian negative δ13C anomaly named ‘Jenkyns Event’. The Weissert Event was studied in a unique southern polar location, where a 40 m thick Lower Cretaceous black shale section was recovered at Ocean Drilling Program (ODP) Site 692, in the Weddell Sea, nearshore Antarctica. The two case studies were selected in distinct and very different paleo-settings and latitudes, in order to explore how global climate perturbations translate into local paleo-environmental responses in the sedimentary record, documenting potentially different pathways in the bio-geochemical cycles. A detailed characterization of δ 13C stratigraphy, calibrated with nannofossil biostratigraphy, was the basis for a univocal identification of the T-OAE (including the Jenkyns Event) and the Valanginian Weissert Event anomalies. Multi-proxy based organic and inorganic geochemical analyses were used to reconstruct OC burial and preservation rates, the nature and sources of organic matter, carbonate chemistry, the evolution of paleo-temperatures, the paleodepositional environment and redox conditions. Both case studies confirm that local sedimentary records of strongly restricted and/or deep marine basins register the δ 13C signals of global perturbations and associated ...
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