Abstract:
The Greenland-Scotland-Ridge (GSR) is a prominent submarine feature that sets boundary-conditions for exchange of water between the North Atlantic and the Norwegian Sea. Its importance caused a series of DSDP drillsites as early as Leg 38 and Leg 49 (the sites on the Reykjanes Ridge). The Norwegian Sea was later visited by several ODP Legs that addressed, amongst others, the Voering Plateau, the Yermak Plateau, the East Greenland Current (such as by Legs 151 and 162). All these expeditions provided a wealth of important data. The location of the drillsites shows that several questions Leg 38 could not address due to the technology of that time are still open. Faunal/Floral maps of all available Diatoms, Radiolaria, Forams and Coccoliths (DSDP/ODP data plus extensions), e.g. both, siliceous(!) and calcareous biota, show extreme faunal/floral differences between North Atlantic and Norwegian Sea during the Miocene and preglacial Pliocene (now: 2.6 Ma) and little or no faunal/floral gradients post 2.6 Ma and during the Oligocene. The maps integrate over large stratigraphic intervals and large coring gaps. Appearing gradients are thus robust against technical disturbances. A subsidence-pattern: Water exchange (WE) in the Oligocene, inhibited WE until 2.6 Ma, reestablished WE post 2.6 Ma appeared to be inconsistent with known plate-tectonic concepts, such as "sclater curves". The extraordinary thickness of the Icelandic crust and the unspecified but "non oceanic" crust beneath the Faeroe-Basalts (Faeroe Block) had not been included in respective models ("sclater curves"). Recently the movements of the continents over the Iceland Hot Spot (IHS) had been addressed. Dated volcanics show a consistent trace of the IHS from about the Tamyr Region (Siberia) through West Greenland, East Greenland to Iceland. Hot spots impact the overlying crust thermally. An early opening of the GSR, a later closing (impact of the IHS plus thickness of Icelandic and Faeroese crust) followed by a reopening from 2.6 Ma on appears thus a plausible way to interpret early DSDP data. Such interpretations lead to different circulation patterns both in the Norwegian Sea and the North Atlantic. Middle Miocene temperature drops, visible as early as in DSDP Site 407 can easily be explained by ice buildup. They do not require overflow through the Denmark Straits. Old seismic data show that overflow in the Denmark Straits occurred "not too much" before 2.6 Ma. Across other sections of the GSR it is, with difficulties, around 2.6 Ma. In the Faeroe Shetland Channel the data that are available to the author do not permit a conclusion. To arrive at datasets that are suitable for coupled atmosphere/ocean models redrills of DSDP sites 336, 337 and 352 are needed. New sites are needed directly in the Denmark Straits (two shallow, one deep) and in the Faeroe Shetland Channel.