Geochemical, sedimentological and micropalaeontological studies of sediment cores from the Vesteris Seamount region (Central Greenland Sea) are used to reconstruct the sedimentation pattern, depositional history and palaeoceanography for the last 250,000 years. The dating and correlation of the sediments were based on oxygen and carbon isotope stratigraphy, absolute ages as well as a palaeomagnetic age model. The hemipelagic deposits near the Vesteris Seamount are characterized by biogenic, terrestrial and volcanogenic sediment input. Besides granulometric results a geochemical data set (carbonate, total organic carbon, sulphur) characterize the sedimentation processes of interglacial and glacial times during the interaction of Atlantic (Norwegian current) and polar surface water masses (East Greenland current) and deep water masses (North Atlantic deep water, Arctic deep water, Greenland Sea deep water) in the Greenland Basin.
By analyzing stable light isotope ratios (18O, 13C) in tests of the planktic foraminifera Neogloboquadrina pachyderma sin. a stratigraphic frame (Antonow, 1995) was established reaching down to O-isotope stage boundary 8/7. In contrast to the Norwegian and Iceland seas the 18O-ratios of Greenland Sea sediments are much more triggered by the ice-effect than by temperature variations. High 13C-ratios occur during interglacial times due to an effective ventilation of surface water masses. The recent surface water masses of the different hydrographic regimes (polar, arctic and atlantic domains) show a typical 13C/18O-field distribution (Vogelsang, 1990; Weinelt, 1993). By knowledge of the ancient isotopic ice-effect (Labeyrie et al., 1987) the 13C/18O-"patterns" of the investigated sediment components allow an identification of different surface palaeo-water masses influencing the central part of the Greenland Sea. During deglaciation (stage boundaries 8/7, 6/5 and 2/1, events 3.3 and 3.1), enormous meltwater input stabilises the water column, leading to periodic interruptions in deep water renewal. The influence of water masses from the Polar and Atlantic Domains in the Greenland Sea are very variable over time. The oceanic fronts in the Vesterisbanken area are always close together, allowing only a narrow Arctic Domain to exist.
A low content of carbonate (5 to 10 weight-%) is a common feature of most of the core sections representing glacial conditions. The corresponding low values of total organic carbon (TOC, 0.2 to 0.3 weight-%) represent the "normal" (hemi)pelagic sedimentation. Sporadic TOC-peaks (more than 0.5 weight-%) indicate a terrigenous input by turbidites and/or contourites. Increased TOC-values, high 13C-ratios, and moderate 18O-ratios are typical for the sedimentation during interglacial times. The distribution pattern of carbonate shows some irregularities (high contents in O-isotope stage 6) and differs from those of the Norwegian Sea. This feature is also described from further cores (Jünger, 1994) of the Greenland Abyssal plain. Peaks of the content of sulphur (up to 0.3 weight-%) of the sediment column are caused by turbiditic volcaniclastics, distributed around the seamount during an intensive Late Quaternary volcanic eruption phase which began 105 ka.
The different isotope records, geochemical and sedimentologic parameters presented in this study reveal climatic trends and give notice of the palaeoceanographic development of the central Greenland Sea and adjacent seas. Although the Vesterisbanken area is rather unique in relation to other positions within the Greenland Sea, climatic data can be compared favourably to the established Late Pleistocene/Holocene sedimentation pattern in the northern North Atlantic. Due to their good correlation to ice core records from Greenland and Antarctica, the Vesterisbanken sediments present a high-resolution regional picture of global climate change.
Antonow, M., Geomar Rep. 44, 1-121 (1995).
Jünger, B., Geomar Rep. 35, 1-103 (1994).
Labeyrie, L. D. et al., Nature 327, 477-482 (1987).
Vogelsang, E., Ber. Sonderforschungsber. 313 23, 1-136 (1990).
Weinelt, M., Ber. Sonderforschungsber. 313 41, 1-106 (1993).