Tracing ocean circulation and weathering using radiogenic isotopes : An isotope geochemical approach to reconstruct glacial-interglacial changes in ocean circulation and continental runoff

This dissertation aims to develop, evaluate and use new radiogenic isotopic proxies for paleoceanographic and paleoclimatic reconstructions at sub-millennial resolution. The Fe-Mn oxyhydroxide fraction in marine pelagic sediments is an ideal archive for this purpose because seawater-derived trace metals such as neodymium (Nd), hafnium (Hf) and lead (Pb) can be chemically extracted from this fraction. This archive was already successfully used in earlier studies for the reconstruction of the seawater Nd isotope evolution in the South Atlantic, but no such record at sub-millennial resolution exists for the North Atlantic. For Hf and Pb isotopes, not a single record using the Fe-Mn oxyhydroxide fraction exists to date. Especially Hf and Pb isotopes in seawater, however, potentially yield valuable information about short-term climatic changes, intensity of glaciation and the prevailing weathering regime on the continents. Therefore, using seawater-derived Hf and Pb isotopes in conjunction with Nd isotopes from the same seawater-derived fraction allow determining the provenance of a water mass and the climatic conditions prevailing at the continental source area.