Geochemical Proxy Based Reconstruction The Trace...

Geochemical proxy-based reconstruction widely utilizes the trace elemental and isotopic compositions of marine biogenic carbonates to interpret the past climatic and oceanographic conditions. However, such proxy-based reconstructions are often challenged by marine diagenesis as carbonates are highly susceptible to diagenesis, especially partial dissolution and secondary calcite recrystallization. Thus quantifying diagenetic effect is a prerequisite for development of any carbonate-based geochemical proxy. Among the metal isotopes, Mg isotopic composition (ÃŽ ´26Mg) of foraminiferal carbonates is a promising proxy to reconstruct the secular seawater ÃŽ ´26Mg variability, which is useful in understanding long-term changes in Mg geochemical cycle. However, as the trace metals like Mg in marine carbonates show greater susceptibility to diagenetic alterations due to its low abundance as compared to that in the co-existing pore fluids, development ÃŽ ´26Mg of marine carbonates as a geochem ical proxy critically requires a thorough understanding of the fractionation behaviors of Mg isotopes during diagenesis. Therefore, the primary goal of this dissertation is to quantify the effect of diagenesis on metal isotopes, in particularly, ÃŽ ´26Mg of marine carbonates from various depositional settings to evaluate the effect of advection, diffusion and lithological variation within the sedimentary column on the extent of calcite diagenesis. For this purpose, trace elemental (e.g., Mg/Ca and Sr/Ca) andShow MoreRelatedResearch Report On Marine Calcareous Microfossils1172 Words   |  5 PagesMarine calcareous microfossils are extensively utilized as geochemical proxy-archives. Among the traditional isotope proxies, ÃŽ ´18O and ÃŽ ´13C of foraminiferal tests are used as geochemical tools to determine numerous paleoceanographic parameters, such as, paleo-temperature, sea-ice volume, paleo-sea level, variation of dissolved inorganic carbon (DIC) in the seawater, paleo-productivit y and ocean circulation pattern (Urey et al., 1951; Epstein et al., 1953; Emiliani, 1954; Boyle and Keigwin, 1985;