| Summary: | Tese de mestrado, Ciências Geofísicas (Geofísica Interna) Universidade de Lisboa, Faculdade de Ciências, 2018 The KPg mass extinction (~66 Ma) and the PETM (~56 Ma) are both abrupt and global climate events in Earth’s history. The KPg mass extinction is commonly attributed to the Chicxulub impact, but in the last decades it has been linked to the Deccan volcanism. The abrupt warming during the PETM is attributed to methane release from seafloor sediments as consequence of the ocean warming due to the North Atlantic Igneous Province (NAIP) volcanic activity. The mechanisms by which these magmatic events led to global climate changes are still poor constrained. A recent approach combining rock magnetic techniques and mineralogical data provided interesting benchmarks to identify period of iron oxides dissolution linked to environmental acidification. Here, magnetic techniques such as magnetic susceptibility and isothermal remanent magnetization are applied to two marine sections encompassing the KPg (Zumaia, Spain) and PETM (Egypt, GSSP) transitions, in order to provide new insights to identify period of severe environmental changes in the geological record and their link to magmatic activity. The magnetic results obtained for both sections, Zumaia and Dababiya, correlate with biostratigraphic, mineralogical and geochemical data from previous studies at different sections worldwide, demonstrating not only the reliability of the data as well as the global dimension of both events. The data obtained for Zumaia supports an important climate event preceding the KPg boundary. Volcanic markers like magnetite dissolution previously identified in Bidart and Gubbio are confirmed here in the case of the Zumaia section. Magnetite depletion also corroborates the presence of akaganéite and Mercury at Zumaia to support the volcanic theory. On a global scale, these markers correlate with global warming, an increase in atmospheric CO2, environmental acidification via acid rains and presence of high stress opportunistic planctik ...
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