SEDIS - Publications
Ziegler, M. et al. (2010): The precession phase of the boreal summer monsoon as viewed from the eastern Mediterranean (ODP Site 968)
ODP 160 968
Utrecht University, Department of Earth Sciences, Utrecht, Netherlands
Lourens, Lucas J.
The precession phase of the boreal summer monsoon as viewed from the eastern Mediterranean (ODP Site 968)
Quaternary Science Reviews
The astronomical timescale of the Eastern Mediterranean Plio-Pleistocene builds on tuning of sapropel layers to Northern Hemisphere summer insolation maxima. A 3000-year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel, S1, in the early Holocene occurred approximately 3000 years after the insolation maximum. The origin of the time lag remains elusive, however, because sapropels are generally linked to maximum African monsoon intensities and transient climate modeling results indicate an in-phase behavior of the African monsoon relative to precession forcing. Here we present new high-resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from ODP Site 968 in the Eastern Mediterranean. We show that the 3000-year precession time lag of the sapropel midpoints is consistent with (1) the global marine isotope chronology, (2) maximum (monsoonal) precipitation conditions in the Mediterranean region and China derived from radiometrically dated speleothem records, and (3) maximum atmospheric methane concentrations in Antarctica ice cores. We show that the time lag relates to the occurrence of precession-paced North Atlantic cold events, which systematically delayed the onset of strong boreal summer monsoon intensity. Our findings may also explain a non-stationary behavior of the African monsoon over the past 3 million years due to more frequent and intensive cold events in the Late Pleistocene. Abstract Copyright (2010) Elsevier, B.V.
Quaternary geology; boreal environment; Cenozoic; climate forcing; East Mediterranean; Foraminifera; geochemistry; Holocene; Invertebrata; isotope ratios; isotopes; Leg 160; Mediterranean Sea; microfossils; monsoons; O-18/O-16; Ocean Drilling Program; ODP Site 968; orbital forcing; organic compounds; oxygen; paleoclimatology; paleoenvironment; precession; Protista; Quaternary; sapropel; stable isotopes; terrestrial environment;
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