Marine Isotope Stage 5
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| Marine Isotope Stage 5 | |
|---|---|
| Name | Marine Isotope Stage 5 |
| Period | Pleistocene |
| Epoch | Late Pleistocene |
| Start | ~130 ka |
| End | ~71 ka |
| Predating | Marine Isotope Stage 6 |
| Following | Marine Isotope Stage 4 |
Marine Isotope Stage 5 is a warm interval of the Late Pleistocene characterized by interglacial and interstadial conditions documented in marine oxygen isotope records from ocean drilling, polar ice cores, and terrestrial archives. It encompasses multiple warm peaks and cooler intervals that correlate with global changes in temperature, ice volume, and sea level recorded by stratigraphic datasets from the North Atlantic Drift, Mediterranean Sea, Bering Strait, and other regions. Researchers from institutions such as the British Antarctic Survey, Lamont–Doherty Earth Observatory, and the Max Planck Institute for Evolutionary Anthropology use it as a benchmark for comparing paleoclimate, paleobotany, and Pleistocene archaeology.
Definition and stratigraphic context
The stage is defined in the marine oxygen isotope stratigraphy established by teams at the Deep Sea Drilling Project, Ocean Drilling Program, and Integrated Ocean Drilling Program using benthic foraminifera δ18O and δ13C records from cores like those at Ocean Drilling Program Site 677 and Vema Channel. Correlations link these marine records to ice-sheet and ice-core chronologies from Greenland Ice Sheet Project 2, European Project for Ice Coring in Antarctica (EPICA), and speleothem sequences from Hulu Cave and Soreq Cave. Biostratigraphic markers such as foraminifera turnovers and tephra layers tied to eruptions of Campi Flegrei and Santorini enable high-resolution alignment with regional stratigraphy used by the Quaternary Research Association.
Subdivisions and chronology (MIS 5a–5e)
Stratigraphers subdivide the interval into substages commonly labeled 5e, 5d, 5c, 5b, and 5a, based on isotopic minima and maxima in stacks such as the LR04 Benthic Stack. 5e corresponds to the last interglacial peak near ~125 ka recognized in records from Sicily, Bermuda, and Great Barrier Reef. 5d and 5b are cooler substages reflected in North Atlantic cores and correlated with iceberg-rafted debris layers documented in the Heinrich events literature, while 5c and 5a are warmer substages with regional expressions recorded in Lake Baikal and Lake Tanganyika. Chronologies use absolute dating from U–Th dating of speleothems, radiocarbon dating limits, and amino acid racemization in shells from sites like Terra del Fuego to constrain ages between ~130 ka and ~71 ka.
Paleoclimate evidence and proxies
Paleoclimate reconstructions integrate proxies: benthic and planktonic foraminiferal δ18O from cores at Mauritania and Iberian Margin; ice-core isotopes from Greenland GISP2 and Vostok; pollen assemblages from Loess Plateau and Black Sea sequences; and biomarker analyses from Cariaco Basin and Red Sea sediments. Marine microfossils such as Nassellaria and radiolarian faunas, plus alkenone unsaturation indices measured at laboratories in Woods Hole Oceanographic Institution, provide sea-surface temperature estimates. Terrestrial indicators include glacier moraines mapped in the Alps, Scandinavia, and the Appalachians, and vegetation shifts recorded in pollen diagrams from Kilimanjaro and Sierra Nevada cores. Speleothem growth intervals in Heshang Cave and isotopic excursions in Lake Malawi sediments add seasonality and hydrological context.
Regional expressions and sea-level changes
Global ice-volume reductions during the warm substages produced sea-level highstands documented in coral reef terraces at Bermuda, Bahamas, and the Red Sea with elevations often inferred from uplift-corrected markers. In the Mediterranean, sedimentary facies shifts and coastal speleothems indicate shoreline transgressions affecting archaeological sites in Levantine Corridor and Cyprus. Northern latitude records show partial retreat of the Laurentide Ice Sheet and readvance signatures in the Fennoscandian Ice Sheet, while permafrost degradation impacted landscapes across Siberia. Tide-gauge proxies and model-data comparisons by groups at NASA Goddard Institute for Space Studies estimate peak sea-levels during 5e at several meters above present in tectonically stable locations, though regional isostatic and tectonic factors produced local variability.
Causes and mechanisms of variability
Orbital forcing via variations in eccentricity, obliquity, and precession as articulated in the Milankovitch cycles framework set the pacing for insolation changes that initiated the substages, with amplification by greenhouse gas concentrations recorded in EPICA Dome C and Siple Dome ice cores. Feedbacks involving albedo changes from retreating ice sheets, ocean circulation shifts in the Atlantic Meridional Overturning Circulation, and atmospheric teleconnections with the El Niño–Southern Oscillation and Indian Ocean Dipole modulated regional climate. Volcanic forcing tied to large eruptions such as those documented in the Green Tuff tephrostratigraphy produced short-term cooling episodes, while vegetation–climate feedbacks recorded in pollen from Iberian Peninsula and Eastern Mediterranean influenced carbon cycle dynamics.
Implications for human evolution and archaeology
The environmental variability and sea-level oscillations during the interval affected dispersal routes and coastal resources exploited by Homo sapiens, Neanderthal populations, and contemporaneous hominin groups in regions including the Levant, North Africa, and Southeast Asia. Archaeological sequences at sites like Skhul and Qafzeh, Ksar Akil, and Jebel Faya show behavioral and technological changes contemporaneous with warm substages, while genetic studies from laboratories at the Max Planck Institute for Evolutionary Anthropology and Wellcome Sanger Institute use coalescent models to relate demographic expansions to climatic amelioration. Coastal refugia, submerged landscapes on the Sunda Shelf and Sahul Shelf, and riverine corridors influenced migration and resource use, with paleoecological reconstructions informing debates about timing of dispersal into Europe and Australia.