HR: 09:15h
AN: PP11C-06 INVITED     [Abstracts]
TI: Timing and Duration of Terrestrial Interglacials in SW Portugal: Direct Land-Sea Comparisons
AU: * Tzedakis, P
EM: p.c.tzedakis@leeds.ac.uk
AF: Earth and Biosphere Institute, School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: Roucoux, K H
AF: Earth and Biosphere Institute, School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: deAbreu, L
AF: Department of Earth Sciences, University of Cambridge, Godwin Laboratory, New Museums Site, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AU: Shackleton, N J
AF: Department of Earth Sciences, University of Cambridge, Godwin Laboratory, New Museums Site, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AB: While a broad correspondence between marine and terrestrial stages has been noted for some time, the lack of sufficiently precise terrestrial chronologies impedes the assessment of phase relationships between changes on land and variations in global ice volume. One way around this problem is to examine marine sequences containing a reliable vegetation signal. The linking of land and sea records through joint pollen and marine proxy analyses from the same samples allows an in situ assessment of phase and amplitude relationships, bypassing correlation issues. The Portuguese margin, where the combined effects of major river systems and narrow continental shelf lead to the rapid delivery of terrestrial material to the deep-sea environment, has in recent years emerged as a prime research area for linking marine and terrestrial records. In particular results from core MD95-2042 have led to a major revision of our understanding of the timing and duration of the last interglacial in southern Europe (Shackleton et al., 2002 Quat. Res. 58, 14). This new scheme proposed that the onset of interglacial conditions on land occurred inside MIS 5e and that forest persisted in southern Europe for 16 kyr, well into the interval of ice growth (MIS 5d). Here we attempt to establish whether similar (i) diachroneity between marine and terrestrial stages and (ii) patterns of extended terrestrial interglacial duration are observed during earlier periods. Foraminiferal oxygen isotope and pollen analyses were undertaken on the interval 190-350 ka from a new core MD01-2443, retrieved in the same area as MD95-2042. Contrary to expectations, what emerges is that the duration of terrestrial temperate stages does not follow any consistent pattern, with tree populations sometimes declining well before ice inception. The pollen record reveals the occurrence of abrupt changes during intervals of low ice volume. What emerges is that while the broad timing of interglacials is consistent with orbital theory, their specific duration appears to be dictated by millennial variability.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1827 Glaciology (1863)
DE: 1833 Hydroclimatology
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting