ABSTRACT Recent mapping in southwestern Michigan conducted through U.S. Geological Survey STATEMAP, EDMAP, and Great Lakes Geologic Mapping Coalition projects has produced new interpretations of the origin of the landforms and sediments of the Lake Michigan and Saginaw lobes of the Laurentide Ice Sheet and the dynamics of these lobes. The Lake Michigan lobe advanced southeastward into a proglacial lake at least as far east as the Kalamazoo moraine. During its advance, the lobe extensively deformed the lacustrine sediments it overrode. These structures will be discussed in several pits. When ice backed away from the Kalamazoo moraine, it formed a series of proglacial lakes, several of which were described for the first time in the studies upon which this guidebook is based. As the ice retreated, lowland areas between morainal uplands were utilized by meltwater drainage events, some of them probably catastrophic in nature. The Saginaw lobe stagnated over a broad marginal area as it retreated northeastward toward Saginaw Bay. The resulting stagnant marginal zone is coincident with the subcrop of the Marshall Sandstone. Enhanced basal drainage into the underlying sandstone may have played a role in the dynamics of the lobe. High-relief, supraglacial landforms such as hummocky topography and ice-walled lake plains overprint subglacial landforms in this region, which include large tunnel valleys with inset eskers. Better understanding of the glacial geology of this region is critical to economic development, management of water resources, and exploration for aggregates and other resources.

The Great Lakes Geologic Mapping Coalition (GLGMC), consisting of state geological surveys from all eight Great Lakes states, the Ontario Geological Survey, and the U.S. Geological Survey, was conceived out of a societal need for unbiased and scientifically defensible geologic information on the shallow subsurface, particularly the delineation, interpretation, and viability of groundwater resources. Only a small percentage (<10%) of the region had been mapped in the subsurface, and there was recognition that no single agency had the financial, intellectual, or physical resources to conduct such a massive geologic mapping effort at a detailed scale over a wide jurisdiction. The GLGMC provides a strategy for generating financial and stakeholder support for three-dimensional (3-D) geologic mapping, pooling of physical and personnel resources, and sharing of mapping and technological expertise to characterize the thick cover of glacial sediments. Since its inception in 1997, the GLGMC partners have conducted detailed surficial and 3-D geologic mapping within all jurisdictions, and concurrent significant scientific advancements have been made to increase understanding of the history and framework of geologic processes. More importantly, scientific information has been provided to public policymakers in understandable formats, emphasis has been placed on training early-career scientists in new mapping techniques and emerging technologies, and a successful model has been developed of state/provincial and federal collaboration focused on geologic mapping, as evidenced by this program’s unprecedented and long-term successful experiment of 10 geological surveys working together to address common issues.

Abstract The spatial variation of sedimentary aquifer properties (e.g., porosity and permeability) must be characterized in order to develop accurate models of groundwater flow and solute transport. Aquifer characterization should ideally involve the following steps: (1) analysis of borehole logs, cores, and hydraulic testing data to determine the sedimentological nature and origin of the strata, and their hydraulic properties; (2) stratigraphic correlation of borehole logs and cores in order to assess the lateral continuity of distinctive sediment types (facies) between boreholes; (3) use of geophysical profiles to assess the orientation and structural continuity of sequences of strata, and to recognize distinctive geophysical patterns that can be related to distinctive sedimentary facies; (4) modeling of the geometry and distribution of sedimentary facies in the volume between boreholes, and (5) distribution of properties such as porosity and permeability as a function of sedimentary facies. Unfortunately, hydrogeologists rarely incorporate information on the sedimentology of aquifers, and shallow geophysical methods are not routinely used for aquifer characterization. Furthermore, techniques for accurately modeling the sedimentary facies or hydrofacies in three dimensions are still under development. However, recent use of combined sedimentological and geophysical techniques (e.g., GPR, high-frequency seismic, resistivity, electrical conductivity) have helped to describe the spatial variation in the porosity and permeability of sedimentary aquifers. These advances are leading to quantitative, 3-D stratigraphic models that provide a link among spatial variation in porosity and permeability, different scales of stratification (defined mainly by variations in grain size, shape, and fabric), and variation in geophysical parameters such