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| Sangamonian | |
|---|---|
| Name | Sangamonian |
| Start | ~130,000 |
| End | ~80,000 |
| Era | Quaternary |
| Period | Pleistocene |
| Named for | Sangamon River |
| Region | North America |
Sangamonian.
The Sangamonian is a late Pleistocene interglacial interval recognized in North American stratigraphy and paleoclimatology that is correlated with the interglacial commonly termed the Eemian in European literature and the Marine Isotope Stage 5e recognized in oceanographic studies. Researchers working at institutions such as the United States Geological Survey, Smithsonian Institution, University of Chicago, University of Illinois Urbana-Champaign, and Ohio State University have characterized Sangamonian deposits in river terraces, loess-paleosol sequences, and coastal sequences. Chronologies developed by teams at Lamont–Doherty Earth Observatory, Scripps Institution of Oceanography, Geological Survey of Canada, and British Geological Survey have linked Sangamonian stratigraphy to marine and ice-core records from projects like ODP Leg 162, EPICA, and GRIP. Evidence from field studies near the Sangamon River, Mississippi River, Illinois River, Ohio River, and Missouri River has made the Sangamonian a focal term in North American Quaternary geology.
Sangamonian deposits occur in fluvial terraces, lacustrine fills, eolian loess units, and coastal barrier sequences associated with Late Pleistocene sea-level highstands. Stratigraphers at the United States Geological Survey, National Oceanic and Atmospheric Administration, California Institute of Technology, and Yale University have mapped Sangamonian sediments in correlation with underlying Illinoian tills and overlying Wisconsinan tills in regions including the Great Lakes, Midwestern United States, Missouri Plateau, and Atlantic coastal plain. Paleopedologists from Cornell University, University of Minnesota, and University of Wisconsin–Madison have described Sangamonian paleosols within loess sequences named by earlier workers affiliated with the Illinois State Geological Survey and the Iowa Geological Survey. Stratigraphic frameworks developed in collaboration with the International Commission on Stratigraphy and regional surveys often reference marker horizons identified by micropaleontologists at Woods Hole Oceanographic Institution and geochronologists at Argonne National Laboratory.
Absolute and relative ages for Sangamonian deposits have been constrained using radiometric and stratigraphic methods applied by teams at Lawrence Livermore National Laboratory, Brookhaven National Laboratory, Australian Nuclear Science and Technology Organisation, and Uppsala University. Correlations to Marine Isotope Stage 5 and specifically MIS 5e are supported by oxygen isotope comparisons from cores recovered during ODP, IODP, and work by PAGES researchers. Radiocarbon limitations beyond ~50,000 years have led to reliance on uranium-series dating performed by groups at University of Oxford and optically stimulated luminescence (OSL) dating developed at University of Cambridge and University of Oxford laboratories. Ice-core chronologies from Greenland Ice Core Project and NEEM provide independent constraints that facilitate alignment of Sangamonian ages with events recorded in Antarctic Ice Sheet records and the Last Interglacial global sea-level reconstructions.
Paleoenvironmental reconstructions for the Sangamonian employ pollen zonation developed by palynologists at Duke University, Pennsylvania State University, and University of Michigan, as well as stable isotope analyses by researchers at ETH Zurich and University of Bern. Vegetation signals recovered from sites near Prairie State, Great Plains, and Appalachian Mountains indicate expanded temperate forest communities, documented by comparisons with assemblages studied by scientists at Kew Gardens and Royal Botanic Gardens, Edinburgh. Alkenone sea-surface temperature records compiled by Max Planck Institute for Chemistry and GEOMAR alongside faunal evidence from Monterey Bay Aquarium Research Institute and Florida Museum of Natural History support warmer-than-Holocene conditions during peak Sangamonian intervals, while speleothem records from Mulu Caves and Crag Cave studied by teams at University of Innsbruck and University of Arizona record regional hydroclimatic variability.
Fossil assemblages attributed to Sangamonian deposits include vertebrate faunas documented by curators at the Field Museum, American Museum of Natural History, and Carnegie Museum of Natural History, and plant macrofossils curated at Missouri Botanical Garden and Harvard University Herbaria. Notable taxa reported from Sangamonian contexts include temperate trees and shrubs recorded by paleobotanists from Royal Ontario Museum and Canadian Museum of Nature, while megafaunal occurrences studied by researchers at Smithsonian National Museum of Natural History include remains comparable to assemblages from La Brea Tar Pits and stratigraphic comparisons with Pleistocene sites listed by the Society of Vertebrate Paleontology. Mollusk and ostracod faunas analyzed by specialists at Natural History Museum, London and Smithsonian provide paleoecological indicators used in basin-scale reconstructions by teams at University of California, Santa Cruz and University of Florida.
Regional correlation of Sangamonian units employs frameworks developed by the North American Commission on Stratigraphic Nomenclature and integrates data from the Loess Plateau analogs in China studied by Chinese Academy of Sciences scientists. Subdivisions recognized in different basins reflect local terrace sequences near the Chesapeake Bay, San Francisco Bay, and Gulf Coast where coastal Sangamonian units are correlated with inland sequences in the Ohio Valley and Midcontinent Rift region. Cross-continental correlation with the Eemian of Europe and interhemispheric comparisons with records examined by researchers at University of Cape Town and University of São Paulo have been facilitated by isotope stratigraphy from Scripps Institution of Oceanography and fauna correlations noted by paleontologists at Naturhistorisches Museum Wien.
The Sangamonian interval is significant for understanding Late Pleistocene climate dynamics, sea-level highstands, and biogeographic responses prior to the Last Glacial Maximum, influencing interpretations by archaeologists at Peabody Museum of Archaeology and Ethnology, National Museum of Natural History, and Royal Ontario Museum regarding human dispersal and occupation in North America. Cultural and technological sequences in Late Pleistocene archaeology curated at Denver Museum of Nature & Science and The British Museum are contextualized against Sangamonian environmental baselines established by researchers at University of Arizona and Arizona State University. Conservation scientists at US Fish and Wildlife Service and policy analysts at National Park Service use Sangamonian analogs for projecting responses of ecosystems and coastlines under future warming scenarios modeled by groups at NASA Goddard Institute for Space Studies and NOAA Geophysical Fluid Dynamics Laboratory.
Category:Quaternary geologic stages