Marine and terrestrial climate variability in the western Mediterranean Sea during marine isotope stages 20 and 19

摘要

The climate variability within late Marine Isotope Stage (MIS) 20 and MIS 19 is examined with particular reference to the response of marine and terrestrial realms in the area surrounding the Alboran Sea (western Mediterranean Sea). Sediment samples from the Ocean Drilling Program Site 976 were used to derive high temporal resolution (average resolution of 450 years) palynological (pollen and spores) and calcareous plankton (coc-colithophores and foraminifera) records. These data, together with the new δ~(18)O_(G.bulloides). make it possible to discuss the paleoenvironmental changes within a well constrained chronological frame. Cooler phases, including late MIS 20 and several cold spells during MIS 19b-a, are marked, on land, by the expansion of open vegetation formations dominated by steppe and semi-desert taxa. At the same time, the western Mediterranean Sea is marked by the incursion of North Atlantic polar-water planktonic taxa. MIS 19c and interstadials of MIS 19b-a are characterized by the spread of prevalent temperate forest taxa that parallel the expansion of warm-water calcareous plankton taxa during periods of lighter δ~(18)O. Climate variations at both precessional and millennial to sub-millennial time-scales, expressed by on land and marine signals, highlight the sensitivity of the western Mediterranean area to both orbital forcing and rapid internal oscillations of the climate systems involving remote connections with North Hemisphere high latitudes. The correlation within the central-western Mediterranean and North Atlantic climate dynamics including the time/spatial gradients related to regional and global climate processes contributes to the reconstruction of the Earth climate dynamics and marine vs land responses, in full Early-Middle Pleistocene transition. These new evidences also provide an opportunity to improve knowledge of MIS 19c now considered, due to its orbital geometry, the best orbital analogue to the Holocene.