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In order to obtain a better knowledge of past oceanographic variability offshore southern Chile, this study reappraises the changes in the sources of nutrients over the last 25 ka based on a detailed comparison of previously published nitrogen isotope and microfossil records (dino?agellate cysts, coccoliths and diatoms) from ODP Site 1233 (41°S). Our ?ndings support the main conclusions of Martinez et al. (2006) in the sense that both the Subantarctic Surface Water and the Gunther Undercurrent are potential sources for the recorded late Quaternary sedimentary d15N signatures at Site 1233, with variable contributions of both sources during different time periods. This study indicates that Subantarctic Surface Water forms the main source for nutrients during the last glacial maximum (25–18.6 cal ka BP), the ?rst part of the deglaciation (18.6–15.7 cal ka BP) and the Holocene (9.8 cal ka BP until present). An increased contribution of Equatorial Subsurface Water as a source of nutrients to the photic zone offshore southern Chile is observed between 14.4 and 9.8 cal ka BP, which is indicative for upwelling conditions at least after 13.2 cal ka BP as indicated by the microfossil data

There is still controversy about the impact and the extent of major high-latitude climate reversals such as the northern hemisphere Younger Dryas and the southern hemisphere Antarctic Cold Reversal. Particularly, the extent to which the southern hemisphere high-latitude ocean atmosphere dynamics determine the southern South American climate, caused by shifts of the Antarctic Circumpolar Current (ACC) and southern westerly wind (SWW) belt, is still a matter of debate. A late Quaternary palaeoenvironmental reconstruction using dinoflagellate cysts and organic geochemical proxies was carried out at ODP Site 1233 (41°0’S, 74°27’W) in the Southeast Pacific, and allowed a better insight into the late Quaternary climate dynamics, i.e., temperature variations, latitudinal shifts of the ACC/SWW-coupled system, changes in the supply of nutrients, etc. Additionally, studies were carried out to improve and to refine environmental proxies such as the process length variation of Operculodinium centrocarpum as a density proxy, the knowledge of ecological preferences of certain dinoflagellate cyst species and the TEX86 index as a temperature proxy. These proxies subsequently allowed a more detailed reconstruction of the palaeoenvironment at Site 1233 during the last 25 kyr.Our results demonstrate that climate variability in the Southeast Pacific mid-latitudes during the last 25 kyr is closely coupled to global atmospheric and oceanographic reorganisations. Both the northern and southern hemisphere high-latitudes play a crucial role in regulating millennial-scale climate variability, while the effects of variable tropical circulations seem to superimpose on the large scale fluctuations controlled by (sub)polar dynamics.

Dinoflagellate cysts are used as a proxy for the reconstruction of the salinity variations during Holocene times in the southwestern Black Sea. Core GeoB 7625-2, located 50 km northeast of the mouth of the Sakarya River, was sampled with a 200 year time interval between 0.25 ka BP – 7.8 ka BP. In the lower part of the core, some crucial intervals were sampled with a higher resolution for the determination of the reconnection between the Black Sea and the Sea of Marmara. A drastic change in the dinoflagellate cyst assemblage – from a freshbrackish water to saltwater association – is observed between ~9.6 and ~8.1 ka BP. The fresh to brackish water indicator species are Spiniferites cruciformis form 1-4 and Pyxidinopsis psilata, while the most important saltwater species are Lingulodinium machaerophorum and cysts of Pentapharsodinium dalei. The first occurrence of euryhaline species took place synchronous with a sea level rise and an increase in productivity. The process length of L. machaerophorum, a salinity proxy, indicates a gradual salinity increase. This assumes a gradual reconnection between the Black Sea and the Sea of Marmara, which conflicts with the catastrophic flood (Noah’s Flood Hypothesis) introduced by Ryan et al. (1997, 2003). The 500 to 800 year cycles observed in the sedimentary record by Lamy et al. (2006), and related to the North Atlantic Oscillation, were not only recorded by us in the salinity variations but also in dinoflagellate cyst abundances (productivity). The observed productivity changes are furthermore related to the sedimentation rate: the increase in precipitation in Anatolia possibly results in a higher sediment discharge leading to a better preservation of the organic-walled microfossils. This makes it difficult to determine whether the fluctuations of the dinocysts/gram ratio are the result of fluctuations in productivity or are an artefact due to changes in the sedimentation rate. Furthermore, it is shown that Peridinium ponticum, a species restricted geographically to the Black Sea, is a good proxy for the reconstruction of Holocene salinity variations since its relative abundance fluctuates synchronous with the process length variations of L. machaeorophorum.