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Evidence for high-frequency (10 4 -10 5 yr) glacial-eustasy during Paleozoic greenhouse intervals

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

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  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 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

  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 (424-419 Ma) and early Late Devonian (382-372 Ma) global greenhouse time intervals

  4. 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)

  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: 0.5-2.0 ‰ 0.8 ‰ 1.9 ‰ 3.2 ‰ 1.8 ‰

  12. 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 ‰

  16. 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.

  17. 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.

  18. Acknowledgements Funding NSF-EAR 0920830 Lab ViorelAtudorei, Dani Gutierrez Field Andy Yuhas, Stephanie Yurchyk

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