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Neogene Deep and Surface Water Palaeoceanography |
Department of Geology, University of Exeter, Exeter, Devon, EX4 4QE
Stratigraphic Services International (UK) Ltd., Chancellor Court, 20 Priestley Rd., Guildford, Surrey, GU2 5YL
The modern benthic foraminifera of the north-east Atlantic Ocean show a distribution pattern related to bottom water masses. Varimax factor analysis of data from depths > 2000 m gives factors which correlate with North-East Atlantic Deep Water (NEADW), North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW); a fourth factor corresponds with the basal part of the Mediterranean Water.
Miocene to Pleistocene benthic foraminiferal assemblages have been compared with the modern assemblages. On the assumption that species have not changed their environmental preferences through time, the fossil assemblages can be used to infer the past existence of water masses similar to those of today. The results presented here show that in the late Miocene, AABW penetrated to the southern flank of Rockall Plateau at the time of build-up of the East Antarctic ice sheet. During the early Pliocene the rate of production of NADW increased, perhaps as a result of a decrease in size of the Antarctic ice sheet, which in turn led to the southward retreat of the limit of penetration of AABW. Throughout much of the Pleistocene, as now, AABW has not penetrated north of the Azores Ridge. NEADW was the most extensive bottom water mass in the late Pliocene and Pleistocene.
