ABSTRACT The last-glacial megaflood Kankakee Torrent streamlined hills and the remarkably straight backslope of the Kalamazoo moraine (Lake Michigan lobe of the Laurentide ice sheet) in southwestern Michigan. Flooding ensued as proglacial Lake Dowagiac overflowed across remnants of the Lake Michigan lobe at the position of the inner margin of the Kalamazoo moraine as glacial debris and ablating ice were pinned against Portage Prairie. Proglacial Lake Dowagiac developed in the Dowagiac River valley as the lobe retreated to form the Valparaiso moraine. A minimum age of the Kankakee Torrent (18.7 ± 0.6 k.y. B.P) is indicated by the weighted mean value of six optically stimulated luminescence ages determined from quartz sand in glaciofluvial sediment on the Kalamazoo moraine (Lake Michigan and Saginaw lobes). This value is consistent with tighter age control based on radiocarbon ages of tundra plants within silty sediment forming ice-walled lake plains and in a torrent-scoured lake basin (Oswego channel) in Illinois. Crosscutting relationships of well-dated moraines indicate the Kankakee Torrent occurred sometime between 19.7 and 18.9 calibrated (cal.) k.y. B.P. as it skirted the south margin of the Valparaiso Morainic System.

ABSTRACT In the central United States, the Laurentide ice sheet advanced considerably farther south and west during the Illinois Episode (marine isotope stage [MIS] 6) in Illinois than during the Wisconsin Episode (MIS 2). The Illinois Episode landscape, beyond the last glacial margin, is thus relatively undisturbed from its original form, with only a drape of last glacial loess on uplands, resulting in some of the best preserved geomorphic features of the MIS 6 Laurentide ice sheet. Recent field observations and high-resolution digital elevation maps have led to new ideas about how an ancestral Lake Michigan Lobe reached its southernmost Pleistocene extent (ca. 150–140 ka) and about the region’s deglacial history. Illinois Episode moraines are notably more narrow and discontinuous than last glacial moraines in northeastern Illinois. Subglacial lineations in Illinois, formed during the Illinois Episode, include a continuum from drumlins and megaflutes to megascale lineations. Crag-and-tail forms are most apparent in southeastern Illinois, influenced by buried Paleozoic bedrock obstacles. In north-central Illinois, megaflutes and drumlins occur in an area of thick glacial drift (>20 m). During deglaciation, an MIS 6 Lake Michigan Lobe likely separated into sublobes as the ice sheet thinned and basal ice conditions became warmer and wetter. Ice streaming into the Kaskaskia River Basin, southwestern Illinois, is envisioned during this period. Factors that likely contributed to faster glacial flow in the basin include the regional topography, a relatively soft and fine-grained substrate, and the subglacial hydrology.

ABSTRACT Landscape features that formed when buried ice melted and overlying sediment collapsed are abundant and widespread in the part of Wisconsin’s Northern Highland region glaciated by the Wisconsin Valley Lobe and the western part of the Langlade Lobe. Stagnation and burial of ice of the Wisconsin Valley Lobe are documented by broad tracts of hummocky moraine topography that record the position of the maximum extent of the lobe, and by extensive pitted and collapsed heads-of-outwash and outwash plains deposited during recession. Recession of the Wisconsin Valley Lobe was characterized by episodes of stagnation interspersed with episodes of readvance, documented by small west-east–trending heads-of-outwash. Advances of the western margin of the Langlade Lobe deposited large northwest-southeast–trending heads-of-outwash characterized by extensive areas of pitted and collapsed outwash plains with obscure but recognizable ice-contact faces. Following recession of the Wisconsin Valley and Langlade Lobes, the Ontonagon Lobe advanced out of the Superior Basin and over sediment containing abundant buried ice. Permafrost and debris cover combined to delay the melting of buried ice and the formation of the postglacial landscape. Regional correlation of ice-margin positions, combined with geomorphic and stratigraphic relationships, indicates that ice buried in north-central Wisconsin persisted in some places for up to 5000 yr or more following the recession of active ice.

ABSTRACT Lobes, or ice streams, of the southern Laurentide ice sheet readvanced periodically during their overall retreat after the Last Glacial Maximum in the Great Lakes region. The Saginaw Lobe readvanced around 20 ka to form a prominent moraine, the Sturgis moraine, near the Michigan-Indiana border. Detailed mapping of nineteen 7½ min quadrangles at a scale of 1:24,000 in and adjacent to Calhoun County, Michigan, supports the interpretation that a large drumlin field behind the moraine was formed at this time, when the basal drainage of the glacier was distributed with high basal pore pressure. During retreat, after moraine construction, the drainage mode switched to a conduit-type system, in which meltwater drained to recessional ice-marginal positions through tunnel valleys. We mapped at least three discontinuous ice-marginal positions on the basis of coarse-grained, subaerial fans beginning at the ends of the tunnel valleys. There is a close association of kames with the tunnel valleys at these locations, suggesting that supraglacial meltwater contributed to the subglacial drainage. Our results support a model in which the drumlins were produced by deformation of the basal diamicton during ice advance prior to the formation of the tunnel valleys during ice retreat. This hypothesis rebuts a previously proposed model for this area in which the drumlins and tunnel valleys, along with boulder gravel deposits, were attributed to formation during a single, catastrophic subglacial sheetflood.

ABSTRACT Developing accurate chronologies is important for understanding the formation and evolution of glacial environments in the Quaternary. Radiocarbon dating is a prominent technique for creating chronologies for glacial events during the late Pleistocene, and although radiocarbon dates from vertebrate fossils are relatively abundant, these dates have been underutilized for timing glacial events. Here, the utility of using radiocarbon dates from large mammal fossils for dating glacial events is explored further. Specifically, this study examines the potential of exclusive use of dated mammal remains to establish a chronology of deglaciation in New York State after the Last Glacial Maximum. We predict the earliest occurrence dates of megafauna to represent a minimum age for the initiation of deglaciation because glacial ice would have needed to have melted for plants and animals to begin to inhabit the state. We also predict dates to progress to more recent ages from south to north following recession of the Laurentide ice sheet. The data support these predictions. The earliest occurrence dates for mammoth and caribou, the suspected first large mammal species to occur within the state, are between 17,470 and 16,430 calibrated yr B.P. These dates imply first occurrence of large mammals in New York State and thus a minimum age of deglaciation beginning ca. 17,000 calibrated yr B.P. Because of the likely delay between the timing of deglaciation and the first mammal inhabitants of the state, this date must be viewed as a minimum age, with deglaciation having occurred sometime prior to this age. Comparing south to north, as an indicator of glacial regression, dates from New York State south of 42°N latitude are earlier compared to dates collected north of this latitude. This progression of dates from south to north supports the prediction that megafauna expanded northward following recession of the Laurentide ice sheet, and it implies that radiocarbon-dated mammalian megafauna data are useful, even exclusively, in identifying the timing of certain glacial events.

Abstract A detailed geologic framework model was utilized for groundwater analysis using a fully three-dimensional variably saturated flow model. The geologic framework model, which was developed by a team of glacial geologists from federal and state geological surveys, was fully three-dimensional and did not contain the usual (unrealistic) assumption of widespread aquifer layers separated by leaky aquitard layers of equal extent. The goal of the analysis was to explore the implications of the new generation of geologic framework models for regional groundwater flow, and particularly, groundwater–surface water interactions. A transient numerical simulation, using infiltration at the ground surface as a boundary condition, revealed rich flow complexity, including: (1) widespread, yet patchy, recharge areas with rates that vary through several orders of magnitude, with the recharge rates being statistically correlated to hydraulic conductivity of the vadose zone sediments, elevation, and ground surface slope; (2) the predominance of local flow systems, resulting in an abundance of seepage zones along the sides of the incised (postglacial) stream valleys, and other manifestations of the high water table and strong groundwater–surface water interaction, such as kettle lakes and wetlands; and (3) existence of partially confined aquifers owing to partial burial of deltaic deposits by moraines and lake-bottom deposits having slow vertical permeability. Taken together, these findings support the need for, and value of, high-resolution geologic framework models and the potential fruitful outcome of strong collaboration between glacial geologists and groundwater modelers.

ABSTRACT The Sidney Geosol in Ohio and Indiana is believed to have developed between marine isotope stage (MIS) 5 and MIS 2. Development stopped when the Laurentide ice sheet extended south of the Great Lakes during MIS 2. Prior reported data and new chronological information are employed here to show that pedogenesis of the Sydney Geosol started prior to 50 cal ka and ended time-transgressively through burial by sediment of the Laurentide ice sheet. Near Sidney, Ohio, the termination age is ca. 25.9 cal ka, whereas at Snyder, Indiana, near the limit of the ice-sheet expansion, the age is ca. 21.9 cal ka. However, at Oxford, Ohio, an interstadial organic accumulation between till units may imply that the upper portion of the Sidney Geosol formed under different conditions than the remainder. At a third site, Huffman Park, Ohio, glacially transported tree remains represent a landscape older than 50 cal ka, which is currently difficult to correlate with any specific paleosol, but which suggests that further insights about conditions prior to ca. 25.9 cal ka may be preserved in the record.

ABSTRACT Based on the interpretation of 893 finite radiocarbon ages, we have revised the time-distance diagram for the Lake Michigan Lobe of the Laurentide ice sheet in Illinois. The data set contains 507 reliable ages determined using standard benzene synthesis–liquid scintillation, including “legacy” ages determined in the 1950s and 1960s at the inception of the radiometric radiocarbon dating method. In addition, the data set includes 278 radiocarbon ages determined by accelerator mass spectrometry. We analyzed the data set based on context, precision, and accuracy to vet minimum or maximum age estimates of diachronic phases. The last glaciation in Illinois is marked by a local maximum margin in northeastern Illinois during the Marengo Phase (modal probability 28,000 cal [calibrated] yr B.P.), and subsequent glacial maximum culminating during the Shelby Phase (24,200 cal yr B.P.). From about that point, the Lake Michigan Lobe entered an overall retreat mode, with significant advances at ~22,200 and 21,100 cal yr B.P. (the Marseilles and Minooka Subphases of the Livingston Phase) and at 20,500 cal yr B.P. (Woodstock Phase). The latter age is also the conservative estimate of the onset of the lacustrine Milwaukee Phase, with referent deposits located as far north as Milwaukee, Wisconsin. This phase ended as the Lake Michigan Lobe made its final advance into Illinois during the Crown Point Phase (18,490 to ca. 16,500 cal yr B.P.), interfingering with the proglacial lacustrine Glenwood Phase deposits (16,900–15,000 cal yr B.P.).

ABSTRACT Glaciotectonic deformation of glacigenic deposits in southwestern Michigan is described and analyzed to determine the source of stress of these strained sediments, which manifests as overturned folds and other deformation similar to shallow crustal décollements. The succession is exposed in 11 aggregate mining operations along the Valparaiso Upland, in portions of Berrien, Van Buren, and Allegan Counties in southwest Michigan. Observed deformation includes a complex array of folds, faults, and thrust features as much as 5 m below the surface exposure of the pit face, consistent with horizontal compressional stresses that were generally aligned with ice flow. Fabric measurement of elongated clasts in the surficial till indicates ice flow from northwest to southeast across the area and parallel to drumlins in the area. Stratigraphically, the area is dominated by fine, lacustrine deposits with coarse sand and gravel capped by the Saugatuck Till during the last glaciation. Sediment grain size, pore-water pressure fluctuations, and topographic relief are interpreted to be responsible for the deformation observed as the Lake Michigan Lobe overrode a proglacial lake basin, including fans and deltas, as it advanced eastward to the Kalamazoo moraine. The fine texture and fabric of the lacustrine sediment package restricted the flow of subglacial water and caused abrupt local increases of pore-water pressure and concomitant coupling and decoupling of the bed-substrate interface. Advancing ice deformed sediments in two stages: (1) proglacially along a décollement at the ice margin, and then (2) subglacially as ice overrode the sediments.

ABSTRACT U.S. Geological Survey (USGS) Monograph 53 by Frank Leverett and Frank Taylor identified more than 20 deltas of late Pleistocene age in the Lower Peninsula of Michigan. To that list, we add many additional deltas discovered during the course of our research. These “relict” deltas are important proxies for paleoenvironmental conditions, particularly wave energies, as well as prevailing wind and longshore drift directions. If dated, they can help to constrain the chronologies of ice retreat and proglacial lake stages. In plan view, relict delta morphologies usually protrude from a paleolake shoreline and are often elongate or cuspate shaped. Most of the deltas identified by Leverett and Taylor have this morphology and are located at the junction of a major present-day river and a relict paleolake shoreline. In this chapter, we map and discuss these deltas, first identified by Leverett and Taylor, while also identifying and describing the other, newly found deltas. All of these deltas formed during the marine isotope stage 2 ice retreat, roughly 28–13 ka. To identify and characterize them, we utilized a variety of data within a geographic information system, mainly a statewide USGS 7.5′ digital raster graphic, a 10 m digital elevation model (DEM), county-level Natural Resources Conservation Service soil data, and schematic lithologic depth profiles interpreted from descriptive water well and oil/gas logs. DEMs were particularly useful, because they can be “flooded” to various elevations of paleolakes. Maps of soil wetness and textural characteristics were also useful in detecting and delineating deltas. In sum, we mapped 61 deltas; 27 had been known from previous works, whereas 34 are newly reported in this study. Most are composed of sandy, well-drained sediments and have smooth, graded longitudinal profiles. Of these, most are perched above a relatively low-relief, poorly drained lake plain. However, unlike several deltas recognized by Leverett and Taylor, we found that many of the newly reported deltas are (1) adjacent to one or more formerly unknown shorelines, (2) not associated with a modern river, (3) complex, and/or (4) broad, coalesced features, deposited by more than one river, with fan-like morphologies. The methods that we used to identify and delineate these deltas can be applied to other regions. Mapping like the kind reported here will aid in a better understanding of the paleocoastal and terrestrial conditions during the late Pleistocene.

ABSTRACT The glaciated terrain along the northern edge of the Appalachian Plateau in the eastern Finger Lakes of central New York has long been recognized as an important location for meltwater routing and for proglacial lake development in the Great Lakes region. Despite recognition of multiple ice margins formed by the Ontario Lobe of the Laurentide ice sheet during the late Wisconsinan, numerical age control of several margins has been elusive, particularly in regard to regional readvances of the Port Bruce (ca. 16,980–18,000 cal [calibrated] yr B.P.) and Port Huron (ca. 14,300– 16,000 cal yr B.P.) Phases. Utilizing light detection and ranging (LiDAR) terrain models in the eastern Finger Lakes area, we identified and described the Mapleton, Tully, and Labrador Hollow moraines. Associated ice-marginal landforms include push moraines, fans, and hummocky topography. In places, these features intrude into the northern heads of through valleys. Coring of three basins directly associated with these landforms yielded more than 20 samples of boreal tree needles and twigs, and Dryas leaves. Accelerated mass spectrometry (AMS) radiocarbon assay results indicate that poststadial lacustrine sedimentation began at ca. 15,000 cal yr B.P., consistent with ages of the Port Huron Phase.

ABSTRACT Thick successions of glacial sediments are important components of shallow aquifer systems, wetland ecologies, and aggregate resources in northeast Illinois. Multiscale mapping studies have often utilized single surface geophysical methods to locally characterize and map geologic units. In this study, two-dimensional (2-D) electrical resistivity methods were combined with high-resolution shear-wave seismic-reflection methods to better characterize glacial sediments and interpret geologic settings. Study sites were associated with sediments of a Wisconsinan phase of glaciation in northeast Illinois and included a regional bedrock valley, a buried tunnel valley, a pitted outwash fan, and an ice-marginal alluvial fan. Electrical resistivity methods were valuable tools with which to characterize textural relationships within geologic units, and they complement the seismic data with regard to stratigraphic boundaries. The seismic data indicated internal architectural features that were not resolvable with electrical resistivity methods. Thus, the combination of electrical methods and seismic methods improved both the detailed geologic characterization of natural resources as well as understanding of local glacial sedimentology.

ABSTRACT Mapping of glacial deposits in Michigan dates to the very beginnings of the glacial theory in North America and logically divides into three parts: (1) early work (1885–1924) by Frank Leverett, Frank Taylor, and their colleagues, culminating in U.S. Geological Survey Monograph 53 and the publication of the first surficial geology maps for the state; (2) incremental upgrades (1925–1982) of Leverett and Taylor’s work in subsequent, statewide maps by Helen Martin and William Farrand; and (3) the period since 1982, characterized by a relatively small number of detailed, process-oriented studies at various scales, including the STATEMAP and EDMAP projects and investigations led by university researchers. Progress in mapping the surficial geology of Michigan has been challenged by the complexity of glacial deposits and limited state and federal funding. The most recent maps are Farrand’s statewide maps of glacial geology, which are based on the maps of Martin, which, in turn, were based on the original reconnaissance maps by Leverett and Taylor, now more than a century old. Thus, statewide maps of surficial sediments and landforms in Michigan are outmoded, often inaccurate, and in need of revision. Fortunately, new technologies and data sets are revolutionizing traditional mapping methods, creating opportunities for making cost-effective and accurate maps of Michigan’s glacial deposits. Digital soils data, in particular, when viewed within a geographic information system environment, offer an especially promising avenue for improved glacial mapping.

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 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.