Paleoenvironmental changes in the Norwegian Sea and the northeast Atlantic during the last 2.8 m.y.: Deep Sea Drilling Project/Ocean Drilling Program Sites 610, 642, 643 and 644

摘要

Sedimentological, isotopic and magnetostratigraphic investigations of Ocean Drilling Program and Deep Sea Drilling Project sites 642, 643, 644 and 610 document the oceanographic and climatic evolution of the Norwegian Sea and the northeastern Atlantic over the last 2.8 m.y.. The results show that a major expansion of the Scandinavian Ice Sheet to the coastal areas took place at about 2.56 Ma. Relatively severe glacials appeared until about 2 Ma. The period 2.6 ‐ 1.2 Ma experienced in general cold surface water conditions with only a weak influx of temperate Atlantic water as compared with late Quaternary interglacials. The Norwegian Sea was a sink of deep water through this period but deepwater ventilation was reduced and calcite dissolution was high compared with the Holocene. Deep water formed by other mechanisms than it does today. Between 2 and 1.2 Ma the glaciations in Scandinavia were small. A transition toward larger glacials took place during the period 1.2 to 0.6 Ma, corresponding to warmer interglacials and reduced calcite dissolution. Only during the last 0.6 m.y. has the oceanographic and climatic system of the Norwegian Sea varied in the manner described in previous studies of the late Quaternary. A strong thermal gradient was present between the Norwegian Sea and the northeastern Atlantic during the Matuyama (2.5–0.7 Ma). This is interpreted as a sign of a more zonal and less meridional climatic system over the region compared with the present situat