1. Speleothem Micromorphology Enhances Interpretations of the Timing and Structure of the Mid-Holocene Warm Period
Steven G. Driese
Department of Geology, Baylor University
Zheng-Hua Li
Center for Space Plasma & Aeronomic Research, University of Alabama at Huntsville
Hai Cheng
Dept. of Geology & Geophysics,
University of Minnesota
Stalagmite,
Raccoon Mtn. TN
NSF EAR to S.G.D.
NSF EAR to Z.-H.L.
South-central Section GSA 2013 Austin

2. Purpose
Investigate the feasibility of using speleothems to reconstruct a high-resolution paleoclimate history in southeastern US.
Combine UV fluorescence micromorphology with U-Th chronology to establish annual records for speleothem.
Compare δ13C values of speleothem deposits with floodplain records, to ascertain Holocene paleoclimate history and events, such as mid-Holocene Altithermal event.

3. Distribution of Caves in the United States
Chattanooga, TN
Isotopically studied sites
From Culver et al., 1999

4. Raccoon Mountain Cave

5. C, O isotopes in the cave system
Temperature / Water effect
Vegetation / Atmosphere

6. Sample analyzed for this study
15 cm

7. Time series of annual microbands
mean = mm/yr
wetter
drier

8. Time series of annual microbands
wetter
wetter
mean = mm/yr
wetter
wetter
drier
drier
drier

9. Base

10. Top
Onset of next wet phase obliterates annual bands, with angular unconformity
This major dissolution surface mantled by terra rossa material is tentatively dated as pre-7.6 ka, so we have 400 years of record going into the onset of the mid-Holocene warming and drying

11. Speleothem δ13C values, ‰ 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)
Example 1: 100 yrs
Example 2: 400 yrs
U/Th ages, yrs. BP

12. Nature of Annual Layers
dark: spring + summer
(a) Shihua Cave, Beijing; (b) Stalagmite ER-77, Ernesto Cave, Italy; (c) Flowstone WM1, Wilder Mann Cave, Austria, Meyer et al. (2009): (in Fairchild & Baker, 2012)
bright: fall + winter

13. Warm/Dry Hypsithermal/Altithermal event during Mid-Holocene: prolonged ENSO episodes, linkage between SW and SE USA?
redrawn from

14. Summary: Proxy Records of Abrupt Holocene Climate and Environmental Change
First example (100 year record) captures the transition from a 5.4 ka dry phase into wet phase, with very distinct seasonality
Second example (400 year record) captures the transition from late Pleistocene to early Holocene, dissolution unconformity (with terra rossa) into first post-7.6 ka dry phase
FUTURE APPLICATION TO OTHER MID-HOLOCENE INTERVALS WHERE ANNUAL LAMINAE PRESERVATION IS VISIBLE? TEXAS?

15. Soil Organic Matter (δ13C, ‰ PDB)
Kocis, M.S. Thesis, 2011, Univ. of Tennessee-Knoxville
N = 294
N = 42
4 Mid-Holocene Warm/Dry Episodes ( ka BP)
Driese et al., 2008,
Quaternary
Research X X X X

16. Refined Paleoclimate Reconstructions
N.A. Mid-Holocene Thermal Maximum
From Marcott et al. (2013) “A reconstruction of regional and global temperature for the past 11,300 years”: Science, v. 339, p , Figure 2(I).