Abstract
A speleothem record of Midcontinental climate and vegetation change during marine oxygen isotope stages 3 and 4
Abstracts with programs - Geological Society of America, Vol.30(7), p.260
Geological Society of America, 1998 annual meeting
1998
Abstract
Three stalagmites from Crevice Cave in southeastern Missouri yield consistent overlapping records of oxygen and carbon isotopic changes during Marine Oxygen Isotope Stages 3 and 4. Eastern Missouri today represents a climatically sensitive ecotonal boundary; the pre-settlement vegetation consisted of a mosaic of oak-hickory forests and tall-grass prairies. Dominated by large C-4 grasses (bluestem, Indian grass, etc.), the tall-grass prairies generate soil organic carbon with a carbon-isotopic signature distinct from that of the forest biomass (mostly C-3 vegetation). Carbon-isotopic signatures preserved in speleothems (which precipitate from waters that pass through the overlying soil) may thus serve as indicators of the dominance of forests vs. grasslands through time. We establish an accurate, high-resolution chronology for the composite stalagmite record with U-Th techniques using thermal-ionization mass spectrometry. Sampled at a resolution of a few hundred years, the record reveals that between 75 and 55 ka, the midcontinental climate oscillated on millennial timescales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Maximum warmth and prairie vegetation peaked between 59 and 55 ka. Forest persisted between 55 and 25 ka, and a cooling trend initiated at 55 ka culminated at 41 ka. The prominent shift to cooler conditions and forest vegetation at 55 ka coincides with the onset of global ice buildup during Stage 3 (taking the deep-sea chronology at face value) and suggests global climatic cooling. We speculate that glacial advance into the Upper Mississippi Valley and the deposition of Roxana Silt most likely lagged behind the 55 ka cooling by at least several thousand years.
Details
- Title: Subtitle
- A speleothem record of Midcontinental climate and vegetation change during marine oxygen isotope stages 3 and 4
- Creators
- Jeffrey A Dorale - University of MinnesotaLarry EdwardsEmi ItoLuis A Gonzalez
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.30(7), p.260
- Conference
- Geological Society of America, 1998 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 1998 annual meeting
- Language
- English
- Date published
- 1998
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240783402771
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