Jörn Thiede and Annik M. Myhre


  During Leg 151, seven locations were drilled in the western Norwegian-Greenland Sea, in Fram Strait, and on the Yermak Plateau. These sites allow us to address the paleoceanographic and climatic history of the surface- and bottom-water masses in high Northern Hemisphere deep-sea basins, of the mode and pattern of water exchange between the Arctic Ocean and the Norwegian-Greenland Sea through Fram Strait, and the Neogene and Quaternary history of glaciation of the surrounding shelves and land regions. A detailed and well-developed pelagic biochronology has been defined for all of the sites, allowing correlation of their stratigraphic record to sedimentary sequences from lower latitudes. Except for a few short-lived interruptions caused by hiatuses, the entire paleoceanographic history from the Eocene, when the Norwegian-Greenland Sea was small and narrow, to the Quaternary can be described.
  When the Norwegian-Greenland Sea was small and consisted of a sequence of narrow basins, surface water penetrated the area from the North Atlantic Ocean and brought temperate to subtropical siliceous faunas and floras. Only during the latter part of the Oligocene and the early part of the Miocene did cool to temperate water develop. The first signs of marine ice covers or the presence of icebergs developed during the late Miocene, earlier on the Iceland Plateau, later in the northern and eastern part of the investigated region. The influence of the marine ice covers and of the influx of icebergs, first from Greenland and later from northwestern Europe, increased during the course of the Pliocene until it reached an important threshold approximately 3 to 4 Ma off southern Greenland and only 2.6 Ma in Fram Strait and off northwestern Europe. This is interpreted as an increase in the dynamics and growth of the ice caps on either side of the Norwegian-Greenland Sea.
  In the course of the Pliocene and Quaternary, rapid changes between glacials and interglacials can be observed. Some of the sediment properties reflect Milankovitch frequencies: in the earlier part of the history these were mainly obliquity-related; during the past 600-700 k.y. that were mainly eccentricity-related. A temperate interval in the middle Pliocene interrupted the history of the delivery of ice-rafting even in Fram Strait and coincided well with the development of boreal forests on northeastern Greenland. Site 907 on the central Iceland Plateau received large quantities of volcanic ash related to the volcanism developed on Iceland and potentially also on Jan Mayen. Site 908 on the Hovgård Ridge allows us to address the tectonic history of the opening of Fram Strait and of the subsidence of the Hovgård "microcontinent." The drill sites of the Yermak Plateau are heavily influenced by sediments related to the development of glaciation on Svalbard. Site 910 penetrated a clearly overconsolidated part of the sequence and seems to have been overridden by the Svalbard ice cap, prior to ~600 ka.

Date of initial receipt: 7 March 1996
Date of acceptance: 31 May 1996

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