1. 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

2. Purdue Stable Isotope (PSI) Facility
1) Sercon IRMS, continuous flow δ13C, δ15N, C/N, %C and %N -PDZ Europa Elemental Analyzer (EA) -Gilson Trace Gas Analyzer 2) Sercon IRMS, continuous flow δ13C, δ15N, C/N, %C and %N -Carlo Erba EA -Gilson Gas Chromatograph 3) Delta V Plus IRMS, continuous flow δ2H, 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

3. 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 ( Ma) and early Late Devonian ( Ma) global greenhouse time intervals

4. Greenhouse vs. icehouse time intervals
Temperature
curve
Greenhouse
High pCO2
Globally high sea Level
Globally high temperatures
Little to no glacial ice
Sluggish atmospheric
and oceanic circulation
Icehouse
Low pCO2
Globally low sea level
Globally low temperatures
Vast expanses of continental glacial ice
Vigorous atmospheric
and oceanic circulation
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)

5. High-frequency (104-105 yr) cycles
(S. Atchley)
Pietras et al. (2003)

6. Oxygen isotopes

7. Oxygen isotopes: Conodonts
Ca5Na0.14(PO4)3.01(CO3)0.16F0.73(H2O)0.85 (Sweet,1988)
Convert to Ag3PO4

8. upper Silurian cycles
Oklahoma, Ontario, Pennsylvania, England

9. upper Silurian (Ludlow-Pridoli)
paleoequator

10. central Oklahoma cycles

11. Upper Silurian
Pleistocene δ18O: ‰
0.8 ‰
1.9 ‰
3.2 ‰
1.8 ‰

12. China, Europe, Middle East, Nevada, Pennsylvania, New York
Upper Devonian cycles
China, Europe, Middle East, Nevada, Pennsylvania, New York

13. early Late Devonian (Frasnian)

14. central Nevada cycles

15. Upper Devonian
1.3 ‰
0.4 ‰
0.5 ‰
1.6 ‰
0.1 ‰
1.0 ‰
0.2 ‰
1.0 ‰

17. Δ δ18O
70% ice: 30% SST
30% ice: 70% SST
0.2 ‰
~15 m: <1°C
~5 m: <1°C
1.0 ‰
~65 m: ~1°C
~30 m: ~5°C
2.0 ‰
~120 m: ~3°C
~50 m: ~6°C
3.0 ‰
~200 m: ~4°C
~90 m: ~10°C

18. 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.

19. Conclusions Implications
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 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.

21. Acknowledgements Field Andy Yuhas, Stephanie Yurchyk
Funding NSF-EAR Lab Viorel Atudorei, Dani Gutierrez
Field Andy Yuhas, Stephanie Yurchyk