Tentative correlation of midcontinent glacial sequence with marine chronology
A tentative glacial-interglacial 3-million-year chronology is synthesized by regional correlation of Midcontinent tills and paleosols to marine paleotemperature/eustatic cycles and oxygen isotope stages. The paleotemperature curves of Beard et al. (1982), based on planktonic foraminiferal abundances, correspond directly with eustatic cycles during the last 3 Ma. These generalized curves are shown to correlate reasonably well with standard oxygen isotope stages at least for the past 900 ka. This indicates that paleotemperature and Vail-type eustatic cycles have been glacially induced during the last 3 Ma. The chronology developed here utilizes both paleotemperature and oxygen isotope stages; however, below the Jaramillo magnetic subchron, isotope curves are more variable and only paleotemperature stages are used. Tills and paleosols at type localities in the Midcontinent area of the US are correlated to the SPECMAP oxygen isotope time scale. Because mid-Brunhes events are poorly constrained by radiometric dates, alternative correlations are possible. The oldest known Midcontinent tills correlate to the first Plio-Pleistocene cold paleotemperature stage and drop in sea level at 2.4 Ma. This Late Pliocene event also corresponds to the first major isotopic enrichment and the onset of late Cenozoic ice-rafting in the North Atlantic region.
- Research Organization:
- Univ. of Washington, Seattle (USA)
- OSTI ID:
- 6653642
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FEDERAL REGION VIII
AGE ESTIMATION
GEOCHEMISTRY
MORAINES
PALEOCLIMATOLOGY
SEDIMENTS
SOILS
CENOZOIC ERA
CORRELATIONS
DEPOSITION
FORAMINIFERA
GLACIERS
ISOTOPE RATIO
OXYGEN ISOTOPES
PALEOTEMPERATURE
PLANKTON
SEDIMENTATION
ANIMALS
AQUATIC ORGANISMS
CHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
INVERTEBRATES
ISOTOPES
MICROORGANISMS
NORTH AMERICA
PALEONTOLOGY
PROTOZOA
SARCODINA
USA
580100* - Geology & Hydrology- (-1989)
580400 - Geochemistry- (-1989)