Paper No. 66-1
Presentation Time: 1:35 PM
LAURENTIDE ICE SHEET READVANCE CA. 21.7 K CAL YR BP AND FORMATION OF GLACIAL LAKE EMINENCE, SOUTH-CENTRAL INDIANA
The chronology of advance and retreat of the Laurentide Ice Sheet (LIS) near its late Wisconsin limit in south-central Indiana provide insights into potential mechanisms driving ice sheet behavior during the last glacial maximum. Recent chronologic and stratigraphic data from five sites in south-central Indiana addressing this topic indicate: 1) the LIS (East White sublobe) reached its maximum late Wisconsin limit ca. 23.9 k cal yr BP, in agreement with ages from the Miami (Ohio) and Decatur (Illinois) sublobes; 2) a ca. 40 km readvance between 22 to 21.5 k cal yr BP came within 10 km of the maximum limit; 3) glacial Lake Eminence formed sometime after ca. 23.9 k cal yr BP when the LIS retreated from its maximum position and existed for ca. 2 kyr until the ca. 21.7 k cal yr BP readvance crossed the northern part of the lake basin. Two new cores from the Lake Eminence basin document ca. 10 m of glacial lake sediment between two late Wisconsin tills, providing evidence the LIS readvanced into the lake. The readvance did not completely cross the lake basin, as five previously collected cores along a north-south transect document a southward-thinning of glaciolacustrine sediment beyond the limit of the readvance. Analysis of LiDAR DEMs within and adjacent to the glacial Lake Eminence basin allow the limit of the readvance to be traced for tens of kilometers through Morgan and Johnson Counties. Additional coring efforts would further refine the spatial extent of the readvance. The timing of the readvance in south-central Indiana correlates with the age of readvance of the Scioto sublobe in south-central Ohio and formation of ice-walled lake plains in central Illinois, suggesting a regional response to climatic conditions although existing proxy records do not suggest a clear mechanism driving this response of the southern-most lobes of the LIS in North America.