Evidence for an Early Saginaw Lobe Ice Retreat and Drainage Adjustments Across Southern Michigan, USA
Date of Award
Doctor of Philosophy
Geological and Environmental Sciences
Mohamed Sultan, Ph.D.
Alan E. Kehew, Ph.D.
Robb Gillespie, Ph.D.
Peter Voice, Ph.D.
Glacial geology, Huron-Erie lobe, Laurentide ice sheet, Saginaw lobe
The Saginaw lobe of the Laurentide Ice Sheet (LIS), flowed out of Saginaw Bay, across Lower Michigan and into northern Indiana. As it retreated, the Saginaw lobe deposited the Sturgis moraine, a recessional moraine of the lobe in southern Michigan. Positioned to the west and east of the Saginaw lobe were the Lake Michigan and Huron-Erie lobes, respectively. These lobes retreated across the region asynchronously, with the Saginaw lobe retreating first. The asynchronous behavior of the lobes allowed for the Lake Michigan and Huron-Erie lobes to overprint and alter landscapes once occupied by the Saginaw lobe ice.
The Kalamazoo moraine, an ice-marginal ridge north of the Kalamazoo River, is up-ice relative to the Sturgis moraine. Surficial geology and bedrock topographic mapping were completed north of the Kalamazoo moraine, to understand the distribution of glacial deposits of this area. Longitudinal and terrace profiles were created along prevailing meltwater channels in the area north of the Kalamazoo moraine using LiDAR data. Three OSL dates from prevailing meltwater channels yielded ages of 13.5 ± 1.4, 17.0 ±1.4, and 13.6 ± 1.5 ka. Surficial mapping, profile analysis, and OSL ages imply that meltwater originating from the Saginaw—Huron-Erie interlobate area drained westward across the Saginaw lobe terrain north of the Kalamazoo moraine.
Optically stimulated luminescence (OSL) ages from lacustrine sediments from the Sturgis moraine include ages of 27.9 ± 1.7, 26.6 ± 1.7, and 23.4 ± 1.9 ka. One radiocarbon age (22.22 ± 0.8 cal ka BP) was determined from bryophytes from near the base of an ice-walled lake plain succession sampled atop the moraine. The OSL ages from the Sturgis moraine indicate that deglaciation of the Saginaw lobe could have been underway in Michigan between ≈27 and 22 ka, while ice margins of the Huron-Erie and Lake Michigan lobes were further south in Indiana and Illinois. This contrasts with previous reconstructions of the LIS which show a continuous ice margin at ≈20.5 cal ka BP much farther south of the Sturgis moraine.
Erber, Nathan, "Evidence for an Early Saginaw Lobe Ice Retreat and Drainage Adjustments Across Southern Michigan, USA" (2022). Dissertations. 3890.