ABSTRACT The Minneapolis Chain of Lakes is a focal point of natural beauty in the heart of the city. Given the recreational and aesthetic imperative, these urban waterbodies have for decades been heavily managed for water quality and lake level. In the early stages of development of Minneapolis’ civic infrastructure, the area’s lakes and streams, as well as the Mississippi River, were given special consideration for preservation. This did not, however, mean that the lakes were preserved in their “natural” state, for they were connected by channels, dredged and filled to turn wetlands into open water and dry land, and even reshaped to better conform to the prevailing fashion of design. These manipulations had dramatic effects on the Chain’s smallest lake, Brownie, which became meromictic after a rapid drop in lake level caused by ditching across the divide to Cedar Lake. The lakes and surrounding area were important sources of subsistence for Dakota and Ojibwe people through the middle of the nineteenth century, and some of the earliest substantive interactions between missionaries and Native Americans in Minnesota played out around the Chain of Lakes and nearby Mississippi River valley. The relative orientation of the lakes (and of other groups of lakes in the Twin Cities), and some lakes’ unusual depths relative to surface areas, result from their formation by melting of ice blocks buried in valley train fill during final retreat of the Laurentide ice sheet. Below tens to hundreds of feet of glacial material, mapping of bedrock surfaces indicates the presence of paleo–Mississippi River channels dating from at least two previous interglacials. The integration of multiple subdisciplines of geology and of various basic sciences within paleolimnology and limnogeology, as well as the relevance to students of historical and environmental information, makes lake sediment studies well suited to hands-on, place-based educational approaches as stand-alone courses or laboratories for a number of different core curriculum and nonmajor classes.

ABSTRACT This one-day trip provides an overview of the hydrostratigraphic attributes of the Platteville aquitard in the Twin Cities Metropolitan area. As a shallowly buried, extensively fractured carbonate rock in an urban setting, vulnerable to contaminants, the Platteville has been the subject of a wide variety of geomechanical and hydrogeologic studies over the past few decades. This work, combined with our own borehole geophysics and outcrop observations, has led to a more comprehensive understanding of the Platteville. The field trip will provide examples of what we have learned from these many different data sources, which collectively lead to a characterization of the Platteville as a complex “hybrid” hydrogeologic unit. Under certain conditions, and from one perspective, it can serve as an important aquitard that limits vertical flow, whereas in other conditions, and from another perspective, it is best considered a karstic aquifer with bedding-plane parallel conduits of very high hydraulic conductivity that permit rapid flow of large volumes of water. One particular focus of the trip will be demonstration of what appears to be predictability in both vertical and bedding-plane fracture patterns that in turn provides some degree of predictability of flow paths in three dimensions. These relationships appear to be operative for the Platteville in other parts of the Upper Midwest where the Platteville is shallowly buried. We will demonstrate that effective management of such complex, karst, “hybrid,” hydrogeologic units requires a sophisticated, nuanced understanding of their heterogeneous behavior.

ABSTRACT This field trip guide presents a summary of the Paleozoic bedrock geology of the Twin Cities (Minneapolis and St. Paul) region as well as an introduction to the Quaternary depositional and erosional history of the Twin Cities area, focusing on the carving of the Mississippi River gorge by glacial River Warren. Within this geological context, the philosophy behind a variety of pedagogical techniques is discussed, together with student learning goals, opportunities, and objectives for each locality.

Abstract Effective geologic and geotechnical mapping in cities requires abundant subsurface data. Large data resources exist in the records of public agencies in the Twin Cities in the form of engineering test boring logs. An efficient system for acquiring and compiling these data aided by computer was developed and used to compile a number of geotechnical maps and reports on the geology, hydrology, engineering characteristics, and construction materials resources of the area. Much new information was obtained on the subsurface continuity and stratigraphy of complex Quaternary deposits, on the buried rock surface topography, and on the geology of bedrock formations.