ABSTRACT On a regional geological map, western Wisconsin looks as if it has very simple, even boring, geology. It is dominated by flat-lying, layer-cake Ordovician sedimentary rocks thinly overlain by Pleistocene glacial drift, yet detailed investigation reveals many interesting geologic features, furnishing research projects and teaching examples for all levels of geological education. In this “simple” area around Spring Valley, Wisconsin, you will see a major cave, an old mine, a large earthen dam and a meteorite impact site. In addition to what these sites say about the area’s geologic and human history, they furnish insight into how geologists piece together evidence as well as illustrate relevant subjects such as groundwater supply, control of catastrophic flooding and intelligent land use. It is our hope that, while enjoying learning about the features in this scenic part of Wisconsin, many of you will be inspired to seek out the unique geology of your area, and bring that knowledge into your classrooms.

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Abstract The geochemistry of selenium in soils on loess deposited as marine sediments involves the depletion by erosion of Se adsorbed on clays and iron oxides and its accumulation in lowlands. This depletion has affected the human heart-death rates (HDR) in Shaanxi Province, China, in western counties of the state of Wisconsin, and elsewhere. In Shaanxi province, a high age-adjusted, annual HDR of 140/ 100,000 people (due to cardiomyopathy or “Keshan disease”) was found to be accompanied by blood-Se values of 20 ng/cm 3 for people living in eroded, clay-poor loess hills. HDRs persisted (without Keshan disease) to middle ages, but were accompanied by somewhat higher blood-Se values. For people living in areas where some clays had been deposited on the Wei River terrace, HDRs were less (66–72) and were accompanied by blood-Se values of 133-79 ng/cm 3 (n = 85), respectively. These values are at the low end of the blood-Se levels found in many other countries. From equations derived from these data, a blood-Se level of 274 ng/cm 3 can be projected for the onset of such heart diseases, a value still less than half of that considered to be the toxic level of Se. In western Wisconsin counties, containing loess derived in part from seleniferous (2–40 µ g/g) Cretaceous shale from Minnesota, the population had lower annual HDRs (283–315/100,000 people) than in counties in which low-clay (sandy) soils predominate (HDR = 343–406). A soil extraction by 0.1 N NaOH gave Se values of 57–91 ng/g for soils in areas having the highest HDRs and 102–120 ng/g in areas having the lowest HDRs. Thus, topography, erosion of clay, bedrock source, and crop depletion of clay adsorbed Se appear to affect human blood levels of Se and heart-death rates.

ABSTRACT Red Wing, Minnesota, is located in the upper Mississippi River valley near the northern margin of the Driftless Area, a portion of southeast Minnesota and western Wisconsin that was not glaciated in the late Quaternary characterized by river valleys deeply dissected through a sequence of Paleozoic sediments. River terraces are prominent in the field trip area. These terraces developed in two steps. Glacial outwash filled the valleys in the late Quaternary, followed by at least two pulses of incision associated with meltwater drainage from large glacial lakes to the north, including glacial Lake Agassiz. Following the last pulse of meltwater incision, tributary streams built sediment fans in the valley floor which the post-glacial Mississippi River was not able to erode. As a result, large lakes—including Lake Pepin—developed in the valley bottom. Lake Pepin has subsequently shrunk by delta progradation from the north. Evidence of Native American habitation in the area extends to Paleoindian time (ca. 11 ka B.P. calendar), but there is limited evidence of large, horticultural populations until A.D. 700. This timing coincides with the advance of the Lake Pepin delta front from St. Paul south to the Red Wing area. Large village sites were strategically placed on terraces above the Mississippi. Recent application of LiDAR (light detection and ranging) and resistivity surveys have aided ongoing archaeological investigations in the Red Wing area. Burial mound groups are visible in airborne LiDAR elevation data, and resistivity surveys have revealed evidence of an extensive village at the Silvernale site.