Abstract
OSL confirmation of wiggle-matched U-series-tuned delta (super 13) C speleothem record with pollen assemblages of the last interglacial to glacial transition, central Illinois, USA
Abstracts with programs - Geological Society of America, Vol.50(6)
Geological Society of America, 2018 annual meeting & exposition
11/2018
Abstract
Collective records of pollen and ostracodes from central Illinois (Pittsburg, Raymond, and Bald Knob basins) provide evidence of consistent environmental change spanning the end of the penultimate glaciation (MIS 6) to the onset of the last glaciation (MIS 3). The records highlight initial tundra-like conditions transitioning to wet/cool dense spruce forest during the late Illinois Episode, a tripartite interglacial (Sangamon Episode) succession, overlain by fossil assemblages that suggest an abrupt shift to continental conditions. The early Wisconsin Episode is marked by return of a lacustrine environment, and upward abundance of spruce pollen and cryophilic ostracodes. The fossil assemblages pre-date reliable radiocarbon dating; establishing the chronology of dramatic changes summarized above has been daunting. Researchers have taken various approaches to this problem, such as invoking similarities with the European pollen record, or predicted vegetation biome response based on changing orbital parameters. The most satisfying and intriguing chronology is based on wiggle-matching of normalized data U-series-tuned delta (super 13) C record from Crevice Cave, Missouri, with stratigraphic detrended correspondence analysis (DCA) of the pollen record from Raymond Basin. The wiggles were initially tuned by visually matching maximum rates of change; the best matches result in R2 values of 0.75. Among the intriguing results of the wiggle-matched chronology is that the abrupt change in warm/wet to non-analog continental conditions occurred between 71 - 70 ka in concert with the onset of MIS 4. Independent vetting of the wiggle-matching results has been attempted for more than 15 years using OSL dating. The results have been inconsistent and vexing, in part because many samples of interest are near or beyond the practical limit of OSL dating with quartz. The latest ages are IRSL ages on feldspar. The results are consistent with wiggle-matched ages in the part of the record from 90 to 40 ka, vetting the important correlation at ca. 71 ka. Age reversals and other problems are observed in ages that are ostensibly late MIS 5 (> 135 ka). At this juncture, OSL (IRSL) ages from these sediments are best judged as "greater than" dates.
Details
- Title: Subtitle
- OSL confirmation of wiggle-matched U-series-tuned delta (super 13) C speleothem record with pollen assemblages of the last interglacial to glacial transition, central Illinois, USA
- Creators
- B. Brandon Curry - Illinois State Geological Survey Champaign, IL USA United StatesJin Cheul Kim - Korea Institute of Geoscience and Mineral ResourcesJeffrey A Dorale - University of Iowa
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.50(6)
- Conference
- Geological Society of America, 2018 annual meeting & exposition
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2018 annual meeting & exposition
- Language
- English
- Date published
- 11/2018
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240805102771
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