Distinguishing climatic and current effects in mid-Pleistocene sediments of Hatton and Gardar Drifts, NE Atlantic

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Abstract
Samples taken from DSDP sites 552 and 553 on Hatton Drift and site 611 on Gardar Drift in the northeast Atlantic Ocean were examined by analyses of carbonate content, coarse fraction amount and composition, fine fraction size and composition, and oxygen isotope ratios. The age of both sections is the mid-Pleistocene, ranging from the end of the Jaramillo Normal Event to the boundary between the Matuyama and Brunhes epochs (about 0.77–0.96 Ma). Records of this time show a change from a dominance of 23 ka to longer periodicity at about 0.818 Ma. This is marked at site 552, but less so at site 611. The grain size is mainly controlled by coccoliths, foraminifera and ice-rafted material, all of which are related to glacial-interglacial changes. Zones barren of and abundant in coccoliths are sensitive indicators of climatic effect. Carbonate increase lags behind foraminiferal oxygen isotope records of surface warming in several glacial to interglacial transitions at both drifts. Different types of carbonates oozes occur on Hatton and Gardar drifts. Of several possible factors influencing these, bottom current effects seem more significant than others, deduced from size analysis of the fine fraction. Sedimentological results in this study further confirm that sediment drifts in the NE Atlantic have maintainted their basic characteristics at least since the mid-Pleistocene.