Sedimentary Analysis of the New Ulm Till and its Importance for Understanding Ice Flow on a Deforming Bed on the Des Moines Lobe of the Laurentide Ice Sheet

• Main Author: Hill, Jessica
• Format: Text
• Language: English
• Published: 2008
• Subjects: Boulder Pavement; Ice Sheet
• Online Access: http://archives.gac.edu/cdm/ref/collection/irstudents/id/3477

The nature and dynamics of the Des Moines lobe of the Laurentide Ice Sheet have been the subject of extensive research focused on better understanding ice flow mechanics. Some models have suggested that a deforming bed may have influenced the Des Moines lobe flow and geometry over a large region. The goal of this project was to determine if till composition is homogenous or if there are variations in composition that may have been the result of local differences in deformation of the Des Moines lobe bed. This research project focused on the striated and faceted boulder pavement that lies immediately below till deposited by the Des Moines lobe (New Ulm till), and on the composition of the lowermost layer of the New Ulm till. Lithologies of the coarse sand size fraction were identified in the till samples from the study area along the axis of the Des Moines Lobe trough. Results show that the lithologic components vary between both a) samples from the same site and, b) samples from different sites. Thus it does not appear that the lowermost New Ulm till is homogeneous, and the possibility of local differences in deformation processes acting on the bed exist.