The Distribution of Major Pelagic Sediment Components in the Mesozoic and Cenozoic North Atlantic Ocean
Jӧrn Thiede, Jan-Erik Strand, Torleiv Agdestein, 1981. "The Distribution of Major Pelagic Sediment Components in the Mesozoic and Cenozoic North Atlantic Ocean", The Deep Sea Drilling Project: A Decade of Progress, John E. Warme, Robert G. Douglas, Edward L. Winterer
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Ten years of deep-ocean drilling have helped to assemble an enormous and largely untapped body of new data about the evolution of the Mesozoic and Cenozoic oceans. The rapid physiographic-tectonic evolution of the ocean basins and the fluctuations of the earth's climate during the Late Mesozoic and Cenozoic, including the climatic deterioration of the past 30 m.y., led to very important changes in the depositional regimes in the deep oceans. These changes are related to the initiation of a vigorous polar bottom-water formation and the generation of steep zonal hydrographic gradients in the surface water-masses. The effects of these changes on pelagic sedimentation cannot be separated easily from each other, but sedimentation rates of pelagic deposits have been used here to quantify the sediment flux into the Late Mesozoic and Cenozoic North Atlantic Ocean. Phases of high (>10- >50 m/10-6y) sediment input at 140-110 m.y.BP, 55-45 m.y.BP and during the past 25 m.y. alternated with intervals of much lower sediment input. Hiatuses which interrupted the sediment record are most frequent at 2-3 km and 4-5 km paleodepth. Processes such as dissolution or downslope displacement generated these hiatuses. They produced a distinctive depth-related accumulation pattern of the North Atlantic deep-sea deposits during the past 140 m.y. Concentrations of pelagic sediment components (calcareous, siliceous, organic and terrigenous detrital material) have been used to describe the temporal and spatial distribution of North Atlantic deep-sea deposits.
Biogenic components outweighed by far the terrigenous detrital flux throughout the past 140 m.y. Carbonate- secreting organisms made quantitatively the most important contribution to the Late Mesozoic and Cenozoic North Atlantic deep-sea sediments. Two phases of sedimentation of carbonate-rich deposits were separated by an interval between 100 and 80 m.y.BP when CaCO3 particles were deluted by chiefly terrigenous detrital material. Before 110 m.y.BP ago the highest concentrations of calcareous matter were confined to the deepest part of the then 4.0-4.5 km- deep North Atlantic Ocean. Since 80 m.y.BP sediments with high concentrations of calcareous matter were deposited above 3 km paleodepth and also between 4 and 5.5 km paleodepth during the past 25 m.y.BP. The deeper occurrence is associated with indications of downslope displacement of calcareous material into the deep abyssal plains in the North Atlantic.
Siliceous particles are the second most important biogenic components (> 20%), but they were preserved only during two relatively brief intervals, 120-100 and 50-40 m.y.BP. Organic carbon concentrations were high (> 1%) 130-100 m.y.BP, coincident with the older maximum of opaline material, and during the past 5 m.y. when they were confined to the part of the basin deeper than 5 km. The North Atlantic did not receive a very high input of terrigenous material during its early history, but about 100-90 m.y.BP sediments with high concentrations of terrigenous material were shed into the basin. During the past 80 m.y. terrigenous material was essentially confined to the deepest part of the basins.
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At the present the Glomar Challenger has drilled over 500 holes over the world ocean, involving hundreds of scientists from dozens of countries. This volume is intended as a review of some of theimportant results from the most comprehensive, ambitious and successful earth-bound geologic project ever undertaken. The symposium upon which this volume originated was held April 4, 1979 at the SEPM/AAPG Annual Meeting in Houston. No comprehensive synthesis of all aspects of the DSDP has appeared, and the topic coverage in this volume is biased towards the sediments and fossils, and their significance for certain aspects of earth history – paleogeography, bathymetry, climatology, oceanography, ecology, environments – all in keeping with the audience of sedimentary geologists.