3 Quaternary Chronology Conundrums: Approximating and Assessing Event Ages

Monday, 18 April 2016
8:00 AM - 12:00 PM
Chancellor Ballroom

EVIDENCE OF MELTWATER MEGAFLOODS NEAR THE SOUTHERNMOST ICE MARGINS OF THE LAURENTIDE ICE SHEET BETWEEN 20.5 AND 18.5 KA

Paper number: 3-7
Program: Theme Sessions
Time: 10:00 AM – 10:20 AM

Authors

  • Hong Wang Presenting Author
    University of Illinois at Urbana-Champaign, Champaign, IL
  • Brandon Curry
    Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL
  • E. Donald McKay
    Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL
  • Richard Berg
    Illinois State Geological Survey, Champaign, IL
  • Andrew Stumpf
    University of Illinois Urbana-Champaign/ Prairie Research Institute, Champaign, IL
  • Sebastien Huot
    Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL
  • Amanda Keen-Zebert
    Desert Research Institute, Reno, NV

Abstract

The last Northern Hemisphere ice sheet margins retreated in the late phase of the Last Glacial Maximum, peaked at 19 thousand calibrated years ago (ka) in response to large-scale changes in all components of the climate system. This recession is presumably to have weakened the Atlantic meridional overturning circulation via freshwater input triggering the Southern Hemisphere deglacial warming by a bipolar seesaw mechanism. The Southern Hemisphere warming was likely responsible for the increase of CO2 in global atmosphere, resulting in the ice–CO2 feedback and initiating the full process of the deglacial warming on the planet. Significant sea-level rise of 5-10 m at 19 ka provides a strong evidence for this hypothesis. However, the evidence of large-scale meltwater discharges from Northern Hemisphere ice sheets is rare. Here we provide AMS 14C and OSL chronologies to argue ice-margin retreat from the Lake Michigan Lobe of the Laurentide Ice Sheet and associated meltwater outwash deposits in the middle Illinois River valley between 20.5 and 18.5 ka and peaked at 19 ka. This event concurred with the immense ice-margin retreat from the Midwestern and Northeastern USA during Erie Interstadial warming period. Much of 900,000 km2 area was free of ice during this interval. Our finding supports the Milankovitch hypothesis that the rising boreal summer insolation in mid-high latitudes triggered the last deglaciation.

Geological Society of America Abstracts with Programs. Vol. 48, No. 5

doi: 10.1130/abs/2016NC-275360

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