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Steven G. Driese Department of Geology, Baylor University Zheng-Hua Li Center for Space Plasma &...
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Transcript of Steven G. Driese Department of Geology, Baylor University Zheng-Hua Li Center for Space Plasma &...
Steven G. Driese Department of Geology, Baylor University
Zheng-Hua LiCenter for Space Plasma & Aeronomic
Research, University of Alabama at Huntsville
Hai ChengDept. of Geology & Geophysics,
University of Minnesota
Stalagmite,Raccoon Mtn. TN
South-central Section GSA 2013 Austin
Speleothem Micromorphology Enhances Speleothem Micromorphology Enhances Interpretations of the Timing and Structure of the Interpretations of the Timing and Structure of the Mid-Holocene Warm PeriodMid-Holocene Warm Period
NSF EAR-0823131 to S.G.D.NSF EAR- 0822824 to Z.-H.L.
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.
Chattanooga, TN
Distribution of Caves in the United States
From Culver et al., 1999
Isotopically studied sites
Raccoon Mountain Cave
C, O isotopes in the cave system
Te
mp
era
ture
/
Wa
ter
eff
ect
Ve
ge
tatio
n /
Atm
osp
he
re
Sample analyzed for this study
15 cm
Time series of annual microbands
mean = 0.038 mm/yrwetter
drier
Time series of annual microbands
mean = 0.027 mm/yr
wetter
drier drierdrier
wetter
wetter
wetter
Base
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
Top
Onset of next wet phase obliterates annual bands, with angular unconformity
Speleothem δ13C values, ‰ PDBδ13
C‰
PD
B
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, yrs. BP
Example 1: 100 yrs
Example 2: 400 yrs
Nature of Annual Layers
dark: spring + summer
bright: fall + winter(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)
Warm/Dry Hypsithermal/Altithermal event during Mid-Holocene: prolonged ENSO episodes,
linkage between SW and SE USA?
redrawn from http://www.cdc.noaa.gov/ENSO/
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?
Soil Organic Matter (δ13C, ‰ PDB)
4 Mid-Holocene Warm/Dry Episodes (4.2-6.6 ka BP)
X X X X
Kocis, M.S. Thesis, 2011, Univ. of Tennessee-Knoxville
Driese et al., 2008, Quaternary Research
N = 294
N = 42
Refined Paleoclimate Reconstructions
From Marcott et al. (2013) “A reconstruction of regional and global temperature for the past 11,300 years”: Science, v. 339, p. 1198-1201, Figure 2(I).
N.A. Mid-Holocene Thermal Maximum