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Evolution of Norwegian Sea: Synthesis of ODP Leg 104 Drilling

Elliott Taylor, Olav Eldholm, Jorn Thiede

Three drill sites across the Voring Plateau region off Norway addressed questions of the origin and structure of seaward-dipping reflectors along this passive margin and of the paleo-oceanographic changes that took place throughout the development of the Norwegian-Greenland Sea. Early Eocene volcanism produced a 760-m thick sequence of interbedded tholeiitic basalts and volcaniclastic sediments at Site 642. Velocity and density changes between the interbedded lithologies and between fine and medium basalt flows give rise to the divergent, seaward-dipping reflectors. This sequence overlies an andesitic series that we interpret was emplaced in the latest phase of continental rifting.

Interpretation of sediment facies and microfossil records provide a history of the evolution of the Norwegian-Greenland Sea. The lower Eocene volcanic pile was emplaced subaerially, and interbedded sediments reflect a nearshore environment at Site 642. Lower-Middle Eocene sediments cored at the base of the Voring Plateau (Site 643) contain a fauna indicative of deep-water conditions. The contrasting faunas between Sites 642 and 643 suggest significant vertical offset existed along this margin since its early inception. Oligocene sediments reflect a constricted basin that gave way to intensified bottom-water circulation, lowered CCD, and upwelling conditions in the middle Miocene (13.5 Ma). A warm-water event is found in uppermost Miocene sediments but gives way to significant cooling hrough the Pliocene. Predominant terrigenous input to the area is documented at around 4.3 Ma, indicating the onset of glacial conditions. Interglacial and glacial events persist throughout the remaining sediment record.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.