Temporal and Spatial Distribution of Ice-Rafted Mineral Grains in Pliocene Sediments of the North Atlantic: Implications for Late Cenozoic Climatic History
Richard Z. Poore, 1981. "Temporal and Spatial Distribution of Ice-Rafted Mineral Grains in Pliocene Sediments of the North Atlantic: Implications for Late Cenozoic Climatic History", The Deep Sea Drilling Project: A Decade of Progress, John E. Warme, Robert G. Douglas, Edward L. Winterer
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An important result of Deep Sea Drilling Project (DSDP) Leg 12 was the discovery of ice-rafted mineral grains in Pliocene sediments of the Labrador Sea and the Hatton-Rockall Basin. The oldest (first) occurrence of ice-rafted mineral grains in these sediments is associated with the evolutionary first appearance of the planktic foraminifer Globorotalia inflata (d’Orbigny) and the extinction of the coccolith Reticulofenestra pseudoumbilica (Gartner), or the first occurrence of the coccolith Emiliania ovata Bukry, or both. This association yields a paleontologic age estimate of 3.0 m.y.BP for the start of low-elevation Northern Hemisphere glaciation extensive enough to produce icebergs in the North Atlantic. Results from subsequent drilling in the North Atlantic (DSDP Legs 37, 48, and 49) confirm that the first ice-rafting is at about 3.0 m.y.BP, and further show that during the Late Pliocene, icebergs penetrated as far south as 45° N. lat in the central North Atlantic (DSDP Hole 410) but not as far south as 37° N. lat (DSDP Holes 333 and 335).
The estimated age of 3.0 m.y.BP for the onset of Northern Hemisphere low-elevation glaciation derived from the North Atlantic is supported by a 3.2 m.y.BP estimate based on paleomagnetically controlled oxygen isotope data from the Equatorial Pacific. North Atlantic planktic foraminiferai assemblages show that warm sea-surface temperatures in the northwestern Atlantic preceded the initiation of Northern Hemisphere glaciation.
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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.