The Late Paleozoic Ice Age: Dynamic Glaciation In An Icehouse World

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The Late Paleozoic Ice Age Dynamic Glaciation
In An Icehouse World

• Michael Rygel
• Department of Geology, SUNY Potsdam
• CSPG University Outreach Lecture Tour

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Acknowledgements

• Co-Authors Chris Fielding, Tracy Frank, Lauren
  Birgenheier
• Post-Doc (University of Nebraska-Lincoln) funded
  by NSF Grant EAR-0417578 (Fielding and Frank)
  Coffman Endowment in Sedimentary Geology
  (Fielding)
• Canadian Society of Petroleum Geologists

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Outline

• Traditional views and significance of the Late
  Paleozoic Ice Age
• Glacial record of eastern Australia
• Evidence for dynamic glaciation
• Future work

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Late Paleozoic Ice Age (LPIA)

• Greatest of the Phanerozoic glaciations
• Most recent transition from icehouse to
  greenhouse conditions

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LPIA Traditional Views
http//www2.nau.edu/rcb7/globaltext2.html

• Widely accepted that glaciation occurred between
  the late Devonian to the middle Permian
• Reconstructions show vast ice sheets throughout
  this time

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Glaciation and Cyclothems

• Wanless and Shepard (1936)
• Cyclic strata (cyclothems) occur throughout
  Euramerica
• Hypothesized that cyclothems formed in response
  to waxing and waning of Gondwanan glaciers
• Lacked detailed correlations and met with some
  resistance

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Glaciation and Cyclothems

• Support for glacioeustasy grew over the next 50
  years
• Studies in the UK and USA demonstrated that
  cycles could be traced across, and probably
  between, basins
• Glacioeustatic model now widely accepted

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LPIA Traditional Views
after Isbell et al. (2003)

• Continuous glaciation over 50-100 Ma
• Waxing and waning of large ice sheets drove
  sea-level change
• Poor biostratigraphic radiometric control
• Diagnoses of glacial facies predates modern
  sedimentological concepts

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Dynamic Glaciation
Isbell et al. (2003)

• Isbell et al. (2003) recognized 3 discrete
  glacial intervals in Gondwanan basins

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Dynamic Glaciation

• Much of the existing literature predates advances
  in radiometric dating and modern sedimentology
• Dynamic glaciation hypothesis has profound
  implications critical testing underway

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Glacial Record of Eastern Australia
after Isbell et al. (2003) and Powell and Li
(1994)

• Contains both Carboniferous and Permian glacial
  deposits.

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Glacial Record of Eastern Australia

• Study areas in eastern Australia that have
  correlative, relatively complete
  Carboniferous-Permian successions

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Glacial Record of Eastern Australia
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Facies associated with glaciation

• Diamictites with faceted, striated,
  bullet-shaped clasts

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Facies associated with glaciation

• Rhythmically laminated mudrocks
• Ice-rafted debris

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Facies associated with glaciation

• Glendonites

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Glacial Record of Eastern Australia
Fielding et al. (2008)
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Comparison with the paleotropics
d180
pCO2
Montañez et al. (2007)
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Late Paleozoic Glacioeustasy

• Late Pennsylvanian glacioeustasy reached
  amplitudes of 80 m and probably exceeded 100 m.
• - Soreghan and Giles., 1999, Geology, v. 27,
  p. 255-258
• Pennsylvanian glacioeustatic sea-level changes
  were probably larger than the 120 m fluctuations
  recorded for the Pleistocene.
  - Joachimski et al., 2006, Geology, v. 34,
  p. 277-280

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Comparison with the paleotropics
Rygel et al (2008)

• Dynamic glaciation yields dynamic glacioeustasy

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Dynamic Glaciation
Isbell et al. (2003)
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Dynamic Glaciation

• 8 discrete glacial intervals 1-8 Ma in duration
• Longer and more widespread glacials through
  Carboniferous to acme in Early Permian declining
  trend to Late Permian
• LPIA lasted longer in eastern Australia than
  anywhere else in Gondwana

Rygel et al (2008) modified from Isbell et al.
(2003)
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Future Work

• Improved correlation
• Spatial and temporal distribution of glaciers
• Ancient climate