The stratigraphic transition and suggested boundary between the Early and Middle Pleistocene in the loess record of northern Eurasia
Published:January 01, 2005
A. E. Dodonov, 2005. "The stratigraphic transition and suggested boundary between the Early and Middle Pleistocene in the loess record of northern Eurasia", Early–Middle Pleistocene Transitions: The Land–Ocean Evidence, M.J. Head, P.L. Gibbard
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This review focuses on the loess–palaeosol record across the Early–Middle Pleistocene transition to show the main structural features in key sections from the Loess Plateau of China via central Asia to Europe. Loess–palaeosol sequences in general demonstrate an impressive coherence with oxygen isotope osillations, providing a high-resolution terrestrial record for stratigraphic subdivision. Accordingly, they are considered useful for detailed climatostratigraphy and correlation. Nonetheless, there are many uncertainties in loess–palaeosol stratigraphic correlation across the Early–Middle Pleistocene transition from region to region within northern Eurasia. The interval between the top of the Jaramillo Subchron and the Matuyama–Brunhes (M-B) Chron boundary is discussed in detail because it embraces suitable horizons for placing the Early–Middle Pleistocene boundary. This interval contains a variable number of loess and palaeosol horizons in sections along the different loess provinces from east to west. A distinctive palaeosol unit just below the M–B reversal can serve as a marker horizon for establishing the Early–Middle Pleistocene boundary. In south Tajikistan, it corresponds to the pedocomplex 10 (PC10) and to palaeosol S8 in the Loess Plateau of China. The base of this soil horizon correlated with the base of Marine Isotope Stage 21 can be considered as a distinctive geological level for recognizing the Early–Middle Pleistocene boundary on the continent.
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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.