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Large parts of the upper Midwest, USA were impacted by permafrost during the Last Glacial Maximum (LGM). Even though permafrost persisted as the Laurentide Ice Sheet began to recede, direct age control of this interval is largely lacking. To better temporally constrain the permafrost interval in western Wisconsin, we identified two sites, outside the Late Wisconsin (MIS 2) glacial limit, that contain relict, ice‐wedge pseudomorphs, initially interpreted to be sand wedges, hosted within well‐drained outwash deposits. The pre‐Wisconsin (>MIS 5) host material commonly displays up‐turned bedding near the contact with the wedges, indicative of well‐formed features. The wedges are filled with well‐sorted, gravel‐free, medium and fine sands, and lack evidence of post‐formational disturbance, pointing to an aeolian sand infill and confirming them as sand wedges. Ventifacts on nearby uplands attest to windy conditions here in the past. Optically stimulated luminescence (OSL) ages on five sand wedges indicate that they filled with sand between c. 19.3 and 18.3 ka at the southerly site and between c. 15.1 and 14.7 ka at the northerly site, which is closer to the LGM margin. Sand wedges at the latter site were wider and had more complex morphologies, possibly suggesting a longer interval of formation and/or more intense permafrost. We also examined a site along a ridge crest, between the two wedge sites, which displayed interbedded loess and sand, dated by OSL to 12.7 ka. Together, these results point to dry, cold, windy conditions in west‐central Wisconsin, within 100 km of the LGM limit. At this time, aeolian sands were being transported across a landscape with (at least scattered) permafrost. The OSL results suggest multiple phases, or perhaps time‐transgressive, sand‐wedge formation, associated with permafrost between c. 19 and 15 ka, with dry, windy (and likely, cold) conditions persisting until at least 12.7 ka. [ABSTRACT FROM AUTHOR]

Understanding the spatial and temporal variation in soil temperatures is important to classification, land use, and management. To that end, mean annual soil temperature (MAST) data for Wisconsin and Michigan were modeled to (i) determine the effects of the Great Lakes and their snowbelts on soil temperatures, and (ii) better estimate the location of the boundary between the mesic and frigid soil temperature regimes in this region. The location of the mesic-frigid (M-F) line is particularly difficult to determine where east-west gradients in air temperature cross north-south trends in snowfall due to Lake Michigan. Additionally, the soil temperature regime of several Great Lakes' peninsulas near the M-F line is in question. To determine the accuracy of our soil temperature model, soil temperature data output from it were compared with data derived from thermocouples implanted in soils at 39 sites in northern Michigan that had been collecting data several times daily for more than 6 yr. Error statistics for the model show that it has essentially no mean bias when examined on an annual basis or for winter, and only a bias of 0.1[degrees]C for the warm season. The M-F line in Wisconsin and Michigan is slightly north of most previously estimated locations, and is strongly influenced by the snowbelt in southern Michigan. Soils in deep snow areas stay warmer in winter than do soils inland, increasing their MAST and forcing the M-F line north of where air temperatures alone might have placed it. Lake-effect areas also stay cold longer into the spring season, and cool down more slowly in fall. Soil temperatures in these areas are, therefore, more moderated on an annual basis, as indicated by coefficients of variation.

Students in a graduate seminar at Michigan State University produced a series of detailed vegetation, soils, and landform maps of a 1.5-square-mile (3.9 [km.sup.2]) study area in southwest Lower Michigan. The learning outcomes (maps) and skill development objectives (sampling strategies and various GIS applications) of this field-intensive mapping experience were driven by the assumption that students learn and understand relationships among physical landscape variables better by mapping them than they would in a classroom-based experience. The group-based, problem-solving format was also intended to foster collaboration and camaraderie. The study area lies within a complex, interlobate moraine. Fieldwork involved mapping in groups of two or three, as well as soil and vegetation sampling. Spatial data products assembled and used in the project included topographic maps, a digital elevation model (DEM), aerial photographs, and NRCS (National Resource Conservation Service) soil maps. Most of the soils are dry and sandy, with the main differentiating characteristic being the amount of, and depth to, subsurface clay bands (lamellae) or gravelly zones. The presettlement (early 1830s) vegetation of the area was oak forest, oak savanna, and black oak 'barrens.' Upland sites currently support closed forests of white, black, and red oak, with a red maple, dogwood, and sassafras understory. Ecological data suggest that these oak forests will, barring major disturbance, become increasingly dominated by red maple. This group-based, problem-solving approach to physical geography education has several advantages over traditional classroom-based teaching and could also be successfully applied in other, field-related disciplines. Key Words: pedagogy, fieldwork, mapping, problem-based learning, vegetation.

The evolution of fragipans in the Great Lakes region is poorly understood despite the common occurrence of fragipans in the region. To help resolve this problem, three soils with fragipans in northern Michigan were studied to evaluate the pedogenic pathways for fragipan evolution, and the results extended to soils forming under similar conditions. Soil characterizations were made via field, physical, chemical, and micromorphological observations and analyses and were evaluated in terms of the major models of fragipan genesis. Because it appears that a combination of pedogenic models best explains many of the fragipan properties of our soils, while also allowing for their variable expression, we developed a new model--one that integrates and synthesizes existing models and one findings--to explain fragipan evolution for many soils in Michigan and the Great Lakes region. The Michigan Model of Fragipan Evolution (MMFE) is therefore a synthesizing model that involves the self-weight collapse of a wet soil or parent material, followed by physical ripening of the collapsed zone. Ripening helps to retain the closely packed fabric and intergrain bridging in the collapsed zone, creating a protofragipan. Later, amorphous bonding agents precipitate in the protofragipan due to its position near a weathering-front discontinuity. The resulting fragipan develops progressively and becomes better expressed with further pedogenesis. Fragipan degradation is eventually initiated by an increasingly prominent, perched zone of saturation that forms seasonally above the fragipan. With time, processes associated with fragipan degradation and translocation of materials to lower parts of the profile exceed processes associated with progressive development, and the fragipan is destroyed.

Many of Michigan's loamy soils exhibit varying degrees of fragipan expression, which may be variously influenced by their parent materials. We examined three soils in northern Michigan with varying degrees of fragipan expression to assess development of fragipans formed in acidic and calcareous glacial drift. To accomplish this, soil characterizations were made through field, physical, chemical, and micromorphological observations and analyses. The soils have bisequal horizonation: an upper sequum associated with podzolization processes and lower sequum associated with lessivage. Protofragipans and fragipans are found only in the lower sequum. The soils experience periodic episaturation and contain at least one lithologic discontinuity, often near the protofragipan or fragipan. The protofragipan and fragipans have loamy sand to loam textures, weak platy to subangular blocky structure, higher bulk densities (1.5-1.9 g c[m.sup.-3]) and lower pH values (4.8-6.8) than adjacent horizons, brittle failure, and fine vesicular pores. Eluvial protofragipan and fragipan horizons contain albic materials that tongue into underlying argillic horizons. Illuvial fragipans exhibit clay coats, flows, and bridging. Thin-section characterizations confirm the presence of closely packed fabrics, intergrain bridging by clays, and void pedofeatures. Scanning electron microscopy (SEM) provides evidence of eluviation, reorganization of silt and clay, fluctuating redox conditions, degraded void pedofeatures, and the presence of surficially amorphous (bonding) materials in the protofragipan and fragipans. Soil extraction data do not preclude the presence of a fragic-property (brittleness) agent. Results, therefore, indicate that these protofragipans and fragipans are pedogenic and can form, with variable expression, in both acidic and calcareous glacial parent materials.

Soils in northern lower Michigan, all formed in sandy glacial outwash, were examined to determine the effects of vegetation and fire frequency vs. climate on their development. To accomplish this, soil development was quantified for 13 pedons that span a region known as the Grayling Fingers. Next, a GIS was used to examine spatial interrelationships among the following data sets for the Fingers area: soils, climate, and presettlement vegetation. The 13 sampled pedons span a major pedologic ecotone between an area of strongly expressed spodic morphology (with hardwood forests, low fire frequencies, and deep snowpacks) and one where soils are Psamments. The Psamment area is dominated by jack pine and oak barrens, which frequently burned in presettlement time, and have much less snow cover in winter. The texture and mineralogy of all pedons are generally similar, thereby ruling out parent material as a controlling factor in their development. The relationships among vegetation patterns and soil development remain unclear in this area. Spatial relationships among snowfall amounts and snowpack thicknesses, however, correlate extremely well to soil development patterns. Thus, I conclude that in this region, patterns of soil development are related primarily to the influence of snowmelt infiltration and its previously documented impact on podzolization. Overstory vegetation may provide a strong, reinforcing influence or may be reacting in turn as a dependent variable to soil development and soil moisture during spring, as impacted directly by snowmelt infiltration.

In midlatitude locations with steep slopes, geomorphic aspect can be an important factor in determining spatial variations in soil development. This study examines the influence of aspect on soil development in Baraga County, Michigan, as a means of explaining within-landform variability. The soils are sandy and have spodic morphologies. All are located on steep slopes (45-73%) of contrasting aspect. Ten pedons each from backslopes on north-to-northeast-(N-NE) and south-to-southwest-(S-SW) facing slopes were described, sampled, and compared using standard techniques. Variation in slope gradient was not, statistically, a determining factor in the differential soil development found here. Aspect has strongly influenced soil development, however, with soils more strongly developed (i.e., more podzolized) on N-NE slopes than on S-SW slopes. Several soil characteristics indicative of strong podzolization were found on N-NE slopes, including higher values of solum thickness and POD index, greater losses of extractable Fe and Al from E horizons and concomitant gains in B horizons, and darker and redder B horizon colors. Soils were generally cooler on N-NE slopes in summer, with essentially similar temperatures under snowpacks in winter. Cooler temperatures and greater amounts of infiltrating water in soils with N-NE aspects may have accelerated podzolization by allowing more organo-metallic complexes to be formed and translocated. Podzolization driven by translocation of amorphous, inorganic compounds appears, however, to be nearly equivalent on sites of differing aspect. Of the ten pedons on N-NE slopes, nine classified as Spodosols (Entic or Typic Haplorthods) and the other was an Entisol. Seven of the 10 pedons on S-SW slopes classified as Entisols (Udipsamments or Udorthents), and the remaining three were Spodosols.

Secondary pedogenic carbonates are usually associated with ustic or drier soil moisture regimes; when found elsewhere, their interpretation can be troublesome. We studied three Alfisol pedons in Michigan that contained secondary carbonates on ped faces. The purpose of the research was to (i) characterize these accumulations, (ii) examine possible genetic explanations for the accumulations, (iii) determine if these soils have calcic horizons, given the recent redefinition of this diagnostic horizon, and (iv) evaluate how current 'k horizon' nomenclature might apply to these soils. Three different drainage classes and two soil temperature regimes were represented in the sampled pedons: a fine, mixed Glossic Eutroboralf; a fine, illitic, mesic Aquic Hapludalf; and a fine-loamy, mixed, mesic Aeric Endoaqualf. All three pedons had thin (

The texture, mineralogy and surface topography of some sandy soils in Michigan are examined to determine the origin of lamellae expression in these soils. Three separate pedogenic processes are found to be responsible for lamellae genesis. Process one involves lithologic discontinuities, process two involves sieving processes of clays and silts and process three involves flocculation by carbonates. Generally, sandy pedons dominated by fine sands and silts are more likely to have lamellae.

Gravel distribution within treethrow mounds and adjacent undisturbed soils in Wisconsin and Pennsylvania were examined to determine the pedoturbation effects of tree uprooting. Erosion of fine materials from the fresh root plate and subsequent treethrow mound leaves gravels as a lag deposit forming surface gravel armors. Continued slow erosion of remaining nongravelly materials diminishes topographic expression of the mound. In time, gravel armors remain as the only evidence of past uprooting events. Key Words: treethrow, microtopography, gravel armor, pedoturbation.

In Michigan's Upper Peninsula, sand dunes are widespread on the sandy floor of former Glacial Lake Algonquin, and many of the nearby uplands also have thin mantles of loess. Previous work concluded that these dunes formed during the early Holocene, long after the lake had drained. Where these dunes have migrated against bedrock uplands, many have accreted into larger dune complexes. South and east of these complexes, uplands are mantled with well-sorted sediment, comparatively rich in finer sands and much like the thin, locally sourced loess deposits in Wisconsin and Michigan. Near the dunes, this loess is typically 50–75 cm thick, and rich in very fine sands; presumably much of this sand was deposited as short-range "blow-over" while the dunes were forming. The loess thins to ≈45 cm and becomes siltier on sites farther downwind, to the southeast. Because the dune complexes contain almost no silt, the silt in the loess was likely generated by deflation of saltating sands on the lake plain, transported in suspension, and deposited generally uniformly across the forested uplands, as indicated by spatial trends in silt contents. Periodic Holocene drought may have thinned the forest and helped to intermittently facilitate this type of eolian activity. [ABSTRACT FROM AUTHOR]

Our study adds to the Quaternary history of eolian systems and deposits in western Wisconsin, USA, primarily within the lower Chippewa River valley. Thickness and textural patterns of loess deposits in the region indicate transport by west-northwesterly and westerly winds. Loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands, similar in some ways to shadow dunes. In many areas, sand was transported up and onto the western flanks of bedrock ridges as sand ramps, presumably as loess was deposited in their lee. Long, linear dunes, common on the sandy lowlands of the Chippewa valley, also trend to the east-southeast. Small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes. Finally, in areas where sediment was being exposed by erosion along cutbanks of the Chippewa River, sand appears to have been transported up and onto the terrace treads, forming cliff-top dunes. Luminescence data indicate that this activity has continued throughout the latest Pleistocene and into the mid-Holocene. Together, these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period. [ABSTRACT FROM AUTHOR]