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Department of Geology, Baylor University,

STEVE DRIESE 1 , Zheng-Hua LI 2 , Hai CHENG 3 , Gary STINCHCOMB 1 , Jim KOCIS 4 , Sally HORN 5 , and Mathew BOEHM 5. SPELEOTHEM MICROMORPHOLOGY IMPROVES INTERPRETATIONS OF FLOODPLAIN PALEOCLIMATE RECORDS AND ENHANCES INTERPRETATIONS OF THE TIMING AND STRUCTURE OF THE MID-HOLOCENE WARM PERIOD.

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Department of Geology, Baylor University,

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  1. STEVE DRIESE1, Zheng-Hua LI2, Hai CHENG3, Gary STINCHCOMB1, Jim KOCIS4, Sally HORN5, and Mathew BOEHM5 SPELEOTHEM MICROMORPHOLOGY IMPROVES INTERPRETATIONS OF FLOODPLAIN PALEOCLIMATE RECORDS AND ENHANCES INTERPRETATIONS OF THE TIMING AND STRUCTURE OF THE MID-HOLOCENE WARM PERIOD • Department of Geology, Baylor University, • Center for Space Plasma & Aeronomic Research, University of Alabama at Huntsville • (3) Department of Geology and Geophysics, University of Minnesota • (4) Department of Geosciences, University of Massachusetts, and • (5) Department of Geography, University of Tennessee, Knoxville

  2. Floodplain Archives in SE USA • Savannah Creek (SC), SE Tenn., (Driese et al., 2008, Quaternary Research) • Lower Tenn. River Valley basin (Kocis, M.S. Thesis, 2011; (MS, JA, HA) ms. in prep.) • Raccoon Mtn. Cave (RMC) speleothem (Li & Driese, Sedimentology, accepted; ms. in prep.) SC RMC

  3. Floodplain soils and buried soils Savannah Creek site near Ooltewah, TN; Driese et al., 2008 Site MS along Tennessee River, Marshall County, AL; Kocis, unpub. MS Thesis, UT-Knoxville , 2011 Normalized δ13CSOM values: values were subtracted from the average recent (last 1000 years) δ13CSOM value for each floodplain section (e.g., Nordt et al., 2008)

  4. Soil Organic Matter (δ13C, ‰ PDB) N = 294 Kocis, M.S. Thesis, 2011 N = 42 4 Mid-Holocene Warm/Dry Episodes (4.2-6.6 ka BP) X X X X Driese et al., 2008, QR

  5. Speleothem Methodology • UV Fluorescence (UVf) of ultra-polished thin sections (@Baylor U.) • U/Th dating of speleothem (@U. Minnesota) • Micro-drilling of powders for δ13C and δ18O analyses (@U. Tennessee-Knoxville and Alabama-Huntsville) • Pollen extraction (@U. Tennessee-Knoxville)

  6. Speleothem Chronology

  7. Speleothemδ13C, ‰ PDB Pink = dry Blue= wet 4,449 yr BP 4,441 yr BP δ13C‰ PDB Sr/Ca: Springer et al. 2008; Geophy. Research Letters (This Study) U/Th ages, BP

  8. Major Terra Rossa Surfaces A B pre-7500 yr BP wet period PPL XPL

  9. Terra Rossa Material

  10. SpelothemUVf Transects Micro-banding is invisible using ordinary microscopy but very apparent with UVf! 7.5ka BP major dissolution surface with 0.5-1 mm thick terra rossa deposits

  11. Microbandedfacies drier wetter Annual growth bands, seasonality record? drier organics = “bright” 4870 yr BP dissolution surface (wet)

  12. Time Series of Annual Microbands mean = 0.038 mm/yr wetter drier

  13. Summary: SpeleothemMicrofacies and Timing • Dry periods (7400~6890, 5950~5340, and 4870~4050 yr BP): 10-100 μm thick, micro-banded (bright/dark UVf) intervals, which may represent annual precipitation bands • Wet periods (13,000-7,500, 6890-5959, and 5340-4870 yr BP): Disconformity surfaces, identified by calcite crystal corrosion and truncation, associated non-UVf capped by bright UVf, and perched terra rossa (clastic) material; Coarse, sector-zoned UVf crystals with wide bands?

  14. Future Work: Pollen in Speleothems (RM0710-8-1) from Raccoon Mountain Caverns, TN (Marine Isotope Stage 3 (Middle Wisconsinan) Quercus Castanea Pinus Fraxinus (Research of Matthew Valente, UT-Knoxville)

  15. Future Work: Correlation with Anderson Pond Sinkhole, TN interval at 87-83 cm depth in new Anderson Pond core (>charcoal age at 80-81 cm depth, 6242-5997 yr BP) Delcourt (1979) Ecol. Monographs

  16. Future Work: Correlation with Anderson Pond, TN Joanne Ballard point-counts Pollen from Delcourt (1979) Mid-Holocene warm/dry interval, 5000-8000 based on > charcoal Do desiccation intervals with illuviated clays & high charcoal in new Anderson Pond core correspond to dry periods recorded in Raccoon Mountain Cave speleothem?)

  17. Summary and Conclusions • Speleothem UVf micromorphology veryusefulin detecting “hidden” microfabrics (e.g., micro-dissolution surfaces, micro-banding) not visible in PPL or XPL • Chronol.-constrained speleothems, combined w/micro-imaging/sampling for δ13C and δ18O analyses → detailed interpretations of timing of wet-dry cycles, ppt. seasonality • Speleothems can provide better time resolution of climate changes than floodplains/buried soils (ideally use both)

  18. Acknowledgments • NSF EAR 0822824 to Li and Horn • NSF EAR 0823131 to Driese • Charcoal work by Joanne Ballard • Pollen work by Matthew Valente • UT-Knoxville Initiative for Quaternary Paleoclimate Research (IQPR)

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