Distribution of the calcareous nannofossil Reticulofenestra asanoi within the Early–Middle Pleistocene transition in the Mediterranean Sea and Atlantic Ocean: correlation with magneto- and oxygen isotope stratigraphy
Published:January 01, 2005
Viviana Reale, Simonetta Monechi, 2005. "Distribution of the calcareous nannofossil Reticulofenestra asanoi within the Early–Middle Pleistocene transition in the Mediterranean Sea and Atlantic Ocean: correlation with magneto- and oxygen isotope stratigraphy", Early–Middle Pleistocene Transitions: The Land–Ocean Evidence, M.J. Head, P.L. Gibbard
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Quantitative analyses of the calcareous nannofossil Reticulofenestra asanoi and related species have been performed on the Early-Middle Pleistocene transition in the Mediterranean Sea (ODP Sites 976 and 963) and Atlantic Ocean (DSDP Hole 610A) in order to improve the understanding of their stratigraphic distributions. Abundance patterns have allowed the identification of the lowest common occurrence (LCO) and highest common occurrence (HCO) of R. asanoi in a short interval below and above the lowest occurrence of Gephyrocapsa sp. 3. Correlation with oxygen isotope stratigraphy at Site 976 places the LCO of R. asanoi at the Marine Isotope Stage (MIS) 34-33 transition and its HCO at the MIS 23-22 transition. At Site 963, the HCO of R. asanoi (estimated age of 0.96 Ma correlated to MIS 25) is regarded as ‘artificially’ low, and its highest occurrence (estimated age 0.90 Ma correlated to MIS 23) has therefore been used for bio-chronostratigraphic correlation. The LCO of R. asanoi is estimated at 1.05 Ma at Site 963 and 1.17 Ma at Hole 610A, which suggests correlation to MIS 30 and MIS 35, respectively. These data suggest a possible diachrony for the LCO of R. asanoi.
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Early–Middle Pleistocene Transitions: The Land–Ocean Evidence
The Early–Middle Pleistocene transition (around 1.2 to 0.5 Ma) marks a profound shift in Earth’s climate state. Low-amplitude 41 ka climate cycles, dominating the earlier part of the Pleistocene, gave way progressively to a 100 ka rhythm of increased amplitude that characterizes our present glacial—interglacial world. This volume assesses the biotic and physical response to this transition both on land and in the oceans: indeed it examines the very nature of Quaternary climate change. Milankovitch theory, palaeoceanography using isotopes and microfossils, marine organic geochemistry, tephrochronology, the record of loess and soil deposition, terrestrial vegetationa! change, and the migration and evolution of hominins as well as other large and small mammals, are all considered. These themes combine to explore the very origins of our present biota.