Isotope ratios and trace element concentrations of basalts from DSDP Leg 15 sites (Appendix 1)

Formation of the Cretaceous Caribbean plateau, including the komatiites of Gorgona, has been linked to the currently active Galápagos hotspot. We use Hf-Nd isotopes and trace element data to characterise both the Caribbean plateau and the Galápagos hotspot, and to investigate the relationship between them. Four geochemical components are identified in the Galápagos mantle plume: two 'enriched' components with epsilon-Hf and epsilon-Nd similar to enriched components observed in other mantle plumes, one moderately enriched component with high Nb/Y, and a fourth component which most likely represents depleted MORB source mantle. The Caribbean plateau basalt data form a linear array in Hf-Nd isotope space, consistent with mixing between two mantle components. Combined Hf-Nd-Pb-Sr-He isotope and trace element data from this study and the literature suggest that the more enriched Caribbean end member corresponds to one or both of the enriched components identified on Galápagos. Likewise, the depleted end member of the array is geochemically indistinguishable from MORB and corresponds to the depleted component of the Galápagos system. Enriched basalts from Gorgona partially overlap with the Caribbean plateau array in epsilon-Hf vs. epsilon-Nd, whereas depleted basalts, picrites and komatiites from Gorgona have a high epsilon-Hf for a given epsilon-Nd, defining a high-epsilon-Hf depleted end member that is not observed elsewhere within the Caribbean plateau sequences. This component is similar, however, in terms of Hf-Nd-Pb-He isotopes and trace elements to the depleted plume component recognised in basalts from Iceland and along the Reykjanes Ridge. We suggest that the Caribbean plateau represents the initial outpourings of the ancestral Galápagos plume. Absence of a moderately enriched, high Nb/Y component in the older Caribbean plateau (but found today on the island of Floreana) is either due to changing source compositions of the plume over its 90 Ma history, or is an artifact of limited sampling. The high-epsilon-Hf depleted component sampled by the Gorgona komatiites and depleted basalts is unique to Gorgona and is not found in the Caribbean plateau. This may be an indication of the scale of heterogeneity of the Caribbean plateau system; alternatively Gorgona may represent a separate oceanic plateau derived from a completely different Pacific plume, such as the Sala y Gomez.

Element concentration and GDGT fractional abundances of sediment core GeoB3910-2

In dieser Arbeit wurde das Zeitintervall zwischen 20 und 10 ka vor heute einschließlich des Heinrichevent 1 und der Younger Dryas am Kern GeoB 3910-2 neu untersucht. An organischen Parametern, basierend auf der Verteilung von bakteriellen GDGTs, und Elementkonzentrationen wurde eine Rekonstruktion der klimatischen Bedingungen und Veränderungen im Hinterland von NO Brasilien durchgeführt. Es zeigt sich, dass sich die durchschnittliche Landtemperatur gleich der Oberflächenwassertemperatur verhält und im Gegensatz zu den Phasen von H6 bis H2 dem antarktischen Erwärmungstrend ab 17 ka vor heute folgt. Weiterhin konnte gezeigt werden, dass durch die südwärts Verlagerung der ITCZ während H1 und der YD die Niederschläge in NO Brasilen intensiviert wurden, was eine Ausbreitung der Flüsse und Änderung der Erosionsgebiete zur Folge hatte.

Micro-facies and µXRF element scanning data of Dead Sea sediment cores DSEn and 5017-1

Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn - Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (µ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at ~3500-3300 and ~3000-2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns.