Diatom biostratigraphic and palaeoceanographic interpretations for the middle to high latitude North Atlantic Ocean
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abstract
Diatoms are useful for biostratigraphic correlation of Neogene sediment sections in the North Atlantic Ocean. The warm-temperate assemblage observed in cores from the middle and high latitude Atlantic enables partial application of the diatom zonations defined in the eastern equatorial Pacific. Sixteen of the equatorial Pacific diatom zones are recognized in cores from the middle latitudes of the North Atlantic.The diatom assemblage implies that surface waters were warm during the early Miocene in the Rockall Plateau region. A decrease in the quality of diatom preservation, and the occurrence of numerous hiatuses at approximately the early-middle Miocene boundary, suggest a major change in oceanic circulation. An increase in deep water overflow from the Norwegian Sea may have been a contributing factor. Although middle Miocene sediments at both middle and high latitudes are generally enriched with silica, a possible restriction of siliceous sedimentation towards the high latitudes is observed during this time. The interval representing the early late Miocene and earliest Pliocene is generally devoid of diatoms.Conditions favouring siliceous sedimentation continued at high latitudes and returned to middle latitudes of the North Atlantic during the late Pliocene, maybe in response to increased intensity of the Gulf Stream. The abundance and preservation of diatoms in high latitude Quaternary sediments is partially controlled by climatic fluctuations. The occurrence of the Denticulopsis seminae group suggest that cool, low saline waters may have occurred in the North Atlantic between 1.1 and about 0.70 Ma.
