Steven G. Driese Department of Geology, Baylor University Zheng-Hua Li Center for Space Plasma & Aeronomic Research, University of Alabama at Huntsville.

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