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Evidence for high-frequency (10 4 -10 5 yr) glacial-eustasy during Paleozoic greenhouse intervals. Bethany P. Theiling a,b and Maya Elrick a a University of New Mexico b Purdue University . Purdue Stable Isotope (PSI) Facility.

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evidence for high frequency 10 4 10 5 yr glacial eustasy during paleozoic greenhouse intervals

Evidence for high-frequency (104-105 yr) glacial-eustasy during Paleozoic greenhouse intervals

Bethany P. Theilinga,b and Maya Elricka

aUniversity of New Mexico

bPurdue University

purdue stable isotope psi facility
Purdue Stable Isotope (PSI) Facility

1) Sercon 20-20 IRMS, continuous flow δ13C, δ15N, C/N, %C and %N

-PDZ Europa Elemental Analyzer (EA)

-Gilson Trace Gas Analyzer 

2) Sercon 20-22 IRMS, continuous flowδ13C, δ15N, C/N, %C and %N

-Carlo Erba EA

-Gilson Gas Chromatograph 

3) Delta V Plus IRMS, continuous flowδ2H, δ18O, δ13C, and δ15N

-Thermo TC-EA

-GasBench II-PAL

4) Delta V Advantage IRMS, dual inlet and continuous flow δ15N, δ18O, and Δ17O

-Headspace extraction of denitrifiers and gold tube thermal decomposition for δ15N, δ18O, and Δ17O

-Vacuum line: thermal decomposition of solids for δ18O and Δ17O on dual inlet

-Laser ablation of solids for δ15N, δ18O and Δ17O (in preparation)

Tim Filley

Greg Michalski

objectives
Objectives

Demonstrate the power of interdisciplinary paleoclimate research (stable isotopes + stratigraphy and sedimentology)

Present evidence that continental glacial ice existed and fluctuated on orbital timescales during late Silurian (424-419 Ma) and early Late Devonian (382-372 Ma) global greenhouse time intervals

slide4

Greenhouse vs. icehouse time intervals

Temperature

curve

Also in greenhouse deposits

Glacial dropstones

Evidence of cyclic changes in water

depth

Geochemical fluctuations best

described by changing ice-volume

(Modified from Scotese 2007)

high frequency 10 4 10 5 yr cycles
High-frequency (104-105 yr) cycles

(S. Atchley)

Pietras et al. (2003)

slide7

Oxygen isotopes: Conodonts

Ca5Na0.14(PO4)3.01(CO3)0.16F0.73(H2O)0.85 (Sweet,1988)

Convert to Ag3PO4

upper silurian cycles
upper Silurian cycles

Oklahoma, Ontario, Pennsylvania, England

upper silurian
Upper Silurian

Pleistocene δ18O:

0.5-2.0 ‰

0.8 ‰

1.9 ‰

3.2 ‰

1.8 ‰

slide12

Upper Devonian cycles

China, Europe, Middle East, Nevada, Pennsylvania, New York

upper devonian
Upper Devonian

1.3 ‰

0.4 ‰

0.5 ‰

1.6 ‰

0.1 ‰

1.0 ‰

0.2 ‰

1.0 ‰

evaporation
Evaporation

5 m of surface seawater would have to evaporate to generate a 0.5‰ increase in δ18O, increasing surface salinity by ~2 ppt

20 m of surface seawater would be evaporated to generate a 2‰ increase in δ18O, increasing surface salinity by ~10 ppt.

slide19

Conclusions

  • δ18O is generated by a combination of ice-volume fluctuations, SST changes, and evaporation
  • Isotopic trends support the hypothesis of glacio-eustasy driving late Silurian and early Late Devonian cycle formation
  • Magnitude of glacio-eustatic change over cycle development is ~10s of meters

Implications

Significant glacial ice existed and fluctuated over 104 - 105 yr

timescales

2) Indicates that these “greenhouse” intervals are not ice-free

3) Climate models must address the large latitudinal

temperature gradients needed to generate polar ice and high seawater surface temperatures.

acknowledgements
Acknowledgements

Funding

NSF-EAR 0920830

Lab

ViorelAtudorei, Dani Gutierrez

Field

Andy Yuhas, Stephanie Yurchyk