DEPOSITIONAL REGIMES IN THE NORWEGIAN GREENLAND SEA - THE LAST 2 GLACIAL TO INTERGLACIAL TRANSITIONS

Various models of surface and deep-water circulation in the Norwegian- Greenland Sea (NGS) have been proposed for the last two glacial to int erglacial transitions. Although much progress has been made in underst anding the sedimentary response to climatic and oceanographic changes, conflicting interpretations have been developed. To clarify some of t hese discrepancies and to test or modify the existing circulation conc epts: a multiparameter approach is applied, combining sedimentological , micropaleontological, organic- geochemical and isotopic methods. On the basis of indicative properties a combined litho- and organo-facies concept is developed and calibrated with modern depositional settings beneath different surface water masses. Sedimentary regimes are then derived for glacial and deglacial settings. Atlantic water intrusions in the NGS reveal complex and highly dynamic patterns for the last two glacial and interglacial periods, with repetitive inflows during Isot ope Stage 6 and a high variability in Isotope Stage 5. Specific facies patterns show maximum extensions of Atlantic Water intrusions during the climatic high-stands 5.5.1, 5.3 and 5.1 and narrowest intrusions i n the cool phases 5.4 and most pronounced in 5.2. In contrast, differe nt glacio-marine depositional regimes depict variable sea ice coverage and supply of ice-rafted debris. Most conspicuous are short-term depo sitional events marked by diamictons, which are related to the high in stabilities of continental ice sheets. Some of the diamictons seem to occur contemporaneously with Heinrich layers H1 and H2. The probable t emporal and obvious phenomenological concidence of Heinrich layers and NGS diamictons suggests a common trigger mechanism which caused an al most simultaneous disintegration of huge continental ice masses along the shelves of North America and the eastern margin of the NGS. A prev ious estuarine circulation model claims regional upwelling along the e astern margin of the NGS for specific periods of the last deglaciation . The organic character of sediments covering the same time intervals show a clear predominance of reworked fossil organic matter and thus d oes not support the estuarine model.