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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. - PowerPoint PPT Presentation
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STEVE DRIESE1, Zheng-Hua LI2, Hai CHENG3, Gary STINCHCOMB1, Jim KOCIS4, Sally HORN5, and Mathew BOEHM5
(1) Department of Geology, Baylor University, (2) 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
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.)
RMCSC
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 (last1000 years) δ13CSOM value for each floodplain section (e.g., Nordt et al., 2008)
4 Mid-Holocene Warm/Dry Episodes (4.2-6.6 ka BP)
X X X X
Kocis, M.S. Thesis, 2011
Driese et al., 2008, QR
N = 294
N = 42
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)
δ13C
‰ P
DB
Blue= wet
Pink = dry
(ThisStudy)
Sr/Ca: Springer
et al. 2008;
Geophy. Research
Letters
4,449 yr BP
4,441 yr BP
U/Th ages, BP
pre-7500 yr BP wet period
A B
PPL XPL
7.5ka BP major dissolution surface with 0.5-1 mm thick terra rossa deposits
Micro-banding is invisible using ordinary microscopy but very apparent with UVf!
4870 yr BP dissolution surface (wet)
organics = “bright”
Ann
ual g
row
th b
ands
, se
ason
ality
rec
ord?
drier
wetter
drier
mean = 0.038 mm/yrwetter
drier
Dry periods (7400~68907400~6890, 5950~53405950~5340, and 4870~40504870~4050 yr BP): 10-100 μm thick, micro-banded (bright/dark UVf) intervals, which may represent annual precipitation bands
Wet periods (13,000-7,50013,000-7,500, 6890-59596890-5959, and 5340-48705340-4870 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?
Castanea Quercus
PinusFraxinus
(Research of Matthew Valente, UT-Knoxville)
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
Do desiccation intervals with illuviated clays & high charcoal in new Anderson Pond core correspond to dry periods recorded in Raccoon Mountain Cave speleothem?)
Mid-Holocene warm/dry interval, 5000-8000 based on > charcoal
Pollen from Delcourt (1979)Joanne Ballard point-counts
Speleothem UVf micromorphology very useful in 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)
NSF EAR 0822824 to Li and HornNSF EAR 0823131 to DrieseCharcoal work by Joanne BallardPollen work by Matthew ValenteUT-Knoxville Initiative
for Quaternary Paleoclimate Research (IQPR)