Carbon and carbonate concentrations of recent and Pleistocene sediments of the Norwegian-Greenland Sea

Surface sediment samples from the Norwegian-Greenland Sea were investigated to reconstruct the spatial distribution of recent carbonate dissolution on the seafloor. Additionally, carbonate dissolution records of Ocean Drilling Program sites 985 and 987 are presented to outline the development of Pleistocene carbonate preservation. Today, well-preserved carbonate tests can be observed along the inflow of warm Atlantic surface water, extending as far as into the northernmost Norwegian-Greenland Sea. Increased dissolution is indicated along the continental margins and in the deepest parts of the Greenland Basin. Factors favoring carbonate preservation were found to be supersaturation of the water column with respect to calcium carbonate, high carbonate rain and probably excess alkalinity of bottom waters supplied by the arctic river discharge. Supralysoklinal dissolution is most important for recent carbonate dissolution in the Norwegian-Greenland Sea, whereas the deepest parts of the Greenland Basin reaches the calcite saturation horizon. Pleistocene dissolution records show some prominent peaks of extreme carbonate dissolution. During the Brunhes chron, carbonate dissolution maxima can be related to meltwater pulses, which probably inhibited deep-water formation in the Norwegian-Greenland Sea during deglaciation events. Long-term severe carbonate dissolution is evident during the late Matuyama chron. This can be probably related to low carbonate rain, due to a more eastwards located East Greenland Current and the nearly absence of the not yet polar adapted Neogloboquadrina pachyderma sin. during that period. Extreme dissolution events during the late Matuyama indicate strongly reduced deep-water formation.

Calcareous dinoflagellates in Maastrichtian to early Miocene sediments of DSDP Hole 39-357

The evolution of calcareous dinoflagellate communities has been investigated for the latest Cretaceous to earliest Neogene interval of the mid-latitude South Atlantic. In doing so, the response of calcareous dinoflagellates to Cenozoic climatic change has been addressed for the first time. Trends in species composition and distribution patterns of wall types indicate significant changes which correlate with major palaeoenvironmental modifications. A first major shift concerning the relative abundance of species and wall types occurred across the Cretaceous-Tertiary boundary. The associations remained stable during the entire Paleocene and Eocene. Only in the late Eocene did a dramatic decrease in temperature cause a slight diversification. A second major shift in the abundance patterns occurred across the Eocene-Oligocene boundary. The early Miocene warming is possibly reflected in the distinct increase in relative abundance of one species. The assemblages of calcareous dinoflagellates evidently react to major climatic changes during the Cenozoic. These poorly investigated organisms may thus provide an important contribution to the understanding of earth's palaeoclimatic evolution.

Determination of absolute coccolith abundances in deep-sea sediments by spiking with microbeads and spraying - SMS-method (Table 1)

A quick new method is described for the quantification of absolute nannofossil proportions in deep-sea sediments. This method (SMS) is the combination of Spiking a sample with Microbeads and Spraying it on a cover slide. It is suitable for scanning electron microscope (SEM) analyses and for light microscope (LM) analyses. Repeated preparation and counting of the same sample (30 times) revealed a standard deviation of 10.5%. The application of tracer microbeads with different diameters and densities revealed no statistically significant differences between counts. The SMS-method yielded coccolith numbers that are statistically not significantly different from values obtained from the filtration-method. However, coccolith counts obtained by the random settling method are three times higher than the values obtained by the SMS- and the filtration-method.