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| Mid-Pleistocene Transition | |
|---|---|
| Name | Mid-Pleistocene Transition |
| Period | Pleistocene |
| Start | ~1.25 million years ago |
| End | ~0.7 million years ago |
| Significance | Shift in glacial cycles from 41-kyr to ~100-kyr periodicity |
Mid-Pleistocene Transition The Mid-Pleistocene Transition marked a major change in Quaternary glaciation characterized by a reorganization of glacial-interglacial cycles, coincident with shifts in ice volume, ocean circulation, and biosphere dynamics. This interval influenced the trajectories of hominin populations, faunal communities, and coastal systems during the Pleistocene, and has been linked to changes recorded in marine and terrestrial archives across the globe.
The term denotes the interval when dominant glacial pacing moved from obliquity-paced ~41,000-year cycles to larger-amplitude ~100,000-year cycles, altering the expression of orbital forcing observed in proxy records from sites such as Vostok Station, Camp Century, Ocean Drilling Program cores, and terrestrial sequences near Olduvai Gorge. Researchers working at institutions like Lamont–Doherty Earth Observatory, British Antarctic Survey, Scripps Institution of Oceanography, and CNRS have used isotope stratigraphy, magnetostratigraphy, and tephrochronology to define its timing and character. The phenomenon is central to debates involving paleoclimatology, paleoceanography, and paleoanthropology and features in syntheses produced by organizations including the Intergovernmental Panel on Climate Change and panels convened by the International Union for Quaternary Research.
Chronologies synthesizing records from Marine Isotope Stage stratigraphy, Greenland Ice Sheet Project cores, EPICA ice cores, and radiometric-dated sequences at Lake Baikal indicate a gradual onset between ~1.25 Ma and ~0.7 Ma with local lead–lag relationships relative to orbital parameters cataloged by John Imbrie, Milutin Milanković theory applications, and astronomical solutions from groups at NASA and the Institut de Mécanique Céleste et de Calcul des Ephémérides. The transition involved increases in glacial amplitude, longer-duration glacials, asymmetric terminations, and changes in atmospheric greenhouse gas concentrations recorded alongside shifts in North Atlantic stadials associated with events cataloged by researchers at Woods Hole Oceanographic Institution and Max Planck Institute for Chemistry.
Explanations advanced by investigators at Lamont–Doherty Earth Observatory, University of Cambridge, University of Washington, and ETH Zurich include nonlinear response models, ice-sheet dynamical instabilities, regolith removal hypotheses influenced by work from Peter Huybers and Andrey Ganopolskii, carbon cycle feedbacks involving the Southern Ocean and terrestrial carbon reservoirs, and pacing changes due to secular variations in Earth's orbital eccentricity derived from astronomical calculations by Jacques Laskar. Competing ideas emphasize ice-sheet regolith interactions proposed by researchers affiliated with University of Copenhagen and threshold behavior in coupled climate-cryosphere models developed at Princeton University and Imperial College London.
Multiproxy records including benthic foraminiferal δ18O from Ocean Drilling Program and Integrated Ocean Drilling Program sites, atmospheric CO2 from EPICA and Vostok Station ice cores, loess–paleosol sequences from the Chinese Loess Plateau, pollen assemblages from Lake Ohrid, and speleothem records from caves studied by teams at University of Oxford and University of Bern document changes in ice volume, temperature, and hydrology. Faunal turnover evidenced in deposits at Boxgrove, Dmanisi, and Atapuerca complements geochemical signals, while magnetostratigraphy anchored by work at Geological Survey of Canada and paleomagnetic laboratories provides chronologic control.
Numerical experiments using Earth system models developed at NCAR, MPI-Met, UK Met Office Hadley Centre, and GFDL have tested hypotheses about ice-sheet dynamics, carbon cycle feedbacks, and orbital forcing interactions. Studies employing intermediate-complexity models from CLIMBER and full-complexity coupled simulations from groups at CNRM and Potsdam Institute reproduce emergent ~100-kyr behavior under conditions including regolith depletion, ice-stream hysteresis, and CO2 drawdown mechanisms invoked by teams associated with University of Arizona and University of Melbourne.
In the North Atlantic and Scandinavian sectors, expanded ice sheets documented in geomorphological maps produced by Geological Survey of Sweden and Natural Resources Canada coincide with iceberg-rafted debris layers correlated to Heinrich-like events analyzed by researchers at Brown University and University of Copenhagen. Monsoon weakening inferred from speleothem and marine records compiled by investigators at Peking University and Australian National University affected South Asian and East Asian regions, while sea-level reconstructions based on sequences from Bermuda, Great Barrier Reef, and Sulu Sea reveal amplified glacio-eustatic swings with implications for coastal migration studied by teams at University of Hawaii and University of Southampton.
The altered pacing of glacial cycles influenced habitat fragmentation, resource availability, and migration corridors implicated in hominin dispersals discussed in literature from Max Planck Institute for Evolutionary Anthropology, Smithsonian Institution, Harvard University, and University College London. Larger-amplitude ice volumes drove greater eustatic sea-level falls preserved in coral terraces at Huon Peninsula and submerged landscapes investigated near Doggerland and Sunda Shelf, impacting coastal archaeology and biogeography studied by researchers at University of Cambridge and Queensland Museum.