Browsing by Subject "Minnesota River Valley"

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    Archean Geology of the Minnesota River Valley Sacred Heart to Morton Geology
    (University of Minnesota Duluth, 2016-12) Grant, James A; Oreskovich, Julie A
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    Guidebook 14. Field Trip Guidebook for the Precambrian Terrane of the Minnesota River Valley
    (Minnesota Geological Survey, 1982) Weiblen, Paul W.
    The gently rolling farmland of southwestern Minnesota is a deceptive blanket over a rich record of the evolution of the earth's crust. The effects of Pleistocene glaciation dominate the area, and the landscape is characterized by a wide variety of glacial deposits which cover most of the bedrock geology. However, many outcrops are a product of glacial erosion and all the Precambrian outcrops in the Minnesota River Valley (MRV) were exposed by steambed erosion in the Glacial River Warren. This river drained Glacial Lake Agassiz prior to the disappearance of the ice sheet which prevented northward drainage to Hudson Bay. As can be seen in Figure 2, the Precambrian rocks of Minnesota occupy a central position in the North American continent. This position is reflected in the present day drainage pattern of the continent. Despite the low topographic relief (600-2,000 ft), there are three major drainage divides in Minnesota. The gentle relief and low elevation are also deceptive indicators of the crustal thickness of the North American continent in the region, which is on the order of 40 km. Despite its thickness and antiquity, the crust in Minnesota has remained geologically active. This is attested to in part by the fact that the Mesozoic north-south hinge line of the sedimentary basins involved in the formation of the Rocky Mountains crossed Minnesota. During the Paleozoic the region was involved in a number of oscillations of epicontinental seas. The distribution of the thin veneer of Phanerozoic rocks (maximum thickness less than 600 m), which were produced in these two episodes of crustal evolution, is shown in Figure 3 and in the geologic map of Minnesota on the frontispiece of the guidebook The geologic record is briefly outlined on the back cover. The thick, "stable" crust in the region is currently involved in the isostatic rebound associated with the disappearance of the Pleistocene ice sheets over North America. The locations of 12 recorded earthquakes in Minnesota are shown on Figure 3. The distribution of the earthquakes appears to be related to Precambrian tectonic features (Mooney and Morey, 1981), and may be related to reactivation of old fault systems in the course of isostatic rebound (Dutch, 1981). The Precambrian rocks in Minnesota define five distinct geologic terranes. The geology of these terranes is briefly outlined on the last page of the guidebook, and further details may be found in Sims and Morey ( 1972) and in more recent papers listed in Morey and others (1981). The outcrops in the MRV are part of the oldest terrane (I). They contain a record of a broad spectrum of igneous and metamorphic rocks which span a time interval from at least 3,500 to 1,800 m.y. Terrane I extends into central Minnesota where it is separated from the greenstone-granite terrane (II) to the north by a complex tectonic zone.
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    Guidebook 19. Field Trip Guidebook Kaolinitic Clays of the Minnesota River Valley and Southwestern Minnesota
    (Minnesota Geological Survey, 1992) Setterholm, Dale R.; Heine, John J.
    A thick mantle of chemical weathering products covers crystalline bedrock of Archean and Proterozoic age in much of central and western Minnesota. The mantle has a vertical profile typically composed of progressively more weathered material upward from fresh bedrock to an erosion surface now covered either by strata of Late Cretaceous age or by glacial and postglacial deposits of Quaternary age. In a pioneering study of regional relationships, Parham (1970) showed that most upland areas underlain by crystalline bedrock in western Minnesota have weathering profiles averaging 30 m in thickness, though profiles as great as 60 m thick may be present locally. Weathered materials are considerably thinner on steep side slopes and absent in many places along valleys cut into the bedrock surface. Nonetheless, their widespread occurrence has created considerable commercial interest. Much of our knowledge of the processes responsible for the origin of the weathering profile in southwestern Minnesota was established by S.S. Goldich in a 1936 University of Minnesota doctoral dissertation entitled "A study in rock weathering" (Goldich, 1938). Six samples of saprolite from the Redwood Falls-Morton vicinity in the Minnesota River Valley were compared chemically and mineralogically with fresh Archean gneiss, their probable parent material. Using these data, together with data from elsewhere, Goldich established an alteration sequence in which calcium-rich plagioclase was transformed to clay, followed by the dissolution of the potassium-rich feldspar and other mafic minerals. These observations are embodied in the so-called Goldich stability series, which in one form or another is taught to every beginning student in geology.
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    Guidebook 5. Field Trip Guide Book for Precambrian Migmatitic Terrane of the Minnesota River Valley
    (Minnesota Geological Survey, 1972) Grant, J.A.; Himmelberg, Glen R.; Goldich, S.S.
    The Minnesota River Valley provides a tantalizing window onto the Canadian Shield on the eastern margin of the Great Plains, tantalizing because of the high grade of the metamorphism, and especially because of the antiquity of the rocks there exposed. Essentially, this is a migmatitic terrane of granitic gneisses with lesser amphibolitic gneisses, commonly with pyroxene, and biotite-rich gneisses, which may contain garnet, cordierite, sillimanite, anthophyllite, or hypersthene. Some of the rocks are greater than 3.0 b.y. in age, and they have been involved in metamorphism and deformation at least 2.6 b.y. ago. These events left rocks with a metamorphic grade in the upper amphibolite or granulite facies, and with a major structure that is similar throughout most of the exposed area. Later minor intrusions, dominantly mafic, cut the older rocks, and conglomerate and quartzite of the Sioux Formation of Late Precambrian age locally overlie them. Deep weathering of the gneisses formed a regolith about 100 feet thick, a part of which was reworked in the formation of Cretaceous deposits of sand and clay. Over this came the glacial deposits of the Pleistocene. With the formation of Lake Agassiz, drainage via Glacial River Warren scoured out the precursor of the present valley leaving an underfit present-day Minnesota River and the glimpse of the Precambrian described in the following pages. The granitic gneisses in the vicinities of Morton, Granite Falls, and Montevideo are among the oldest known crustal rocks. Like very ancient rocks in other parts of the world the gneisses have had a complicated history, and metamorphic changes have masked their original characters and obscured their age. Conservatively the age may be given as 3200 or 3300 m. y. Goldich and others (1970) have attempted to probe the metamorphic history and concluded that the gneisses date back to 3550 m.y. ago. Similarly old, or older gneisses (3600 to 4000 m.y.) have been reported from the Godthaab district, West Greenland (Black and others, 1971). Field and more detailed geochronological and geochemical investigations are being continued, and the nature of this work is briefly indicated in following sections.
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    Investigation of Kaolin in Eastern Redwood County, Minnesota, Using Gravity, Magnetic, and Electrical Resistivity Methods
    (University of Minnesota Duluth, 1990-10) Chandler, Val W; Hauck, Steven A; Severson, M; Heine, John J; Reichhoff, J; Schaap, Bryan D
    The utility of gravity, magnetic and electrical resistivity methods for kaolin exploration was evaluated on a test-drilled 300-meter by 600-meter prospect in the Minnesota River Valley in eastern Redwood County, Minnesota. Seven Wenner soundings and three resistivity profiles were taken over the prospect, and interpretations were constrained by direct determinations at nearby bedrock exposures and by drill hole (regolith) data. High-precision gravity data also appear to reflect thickness variations in the low-density kaolin. The magnetometer is not sensitive to the kaolin itself, but it may be useful in detecting rocks in the protolith that yield chlorite-rich, weathered clays, such as diabase dikes.
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    Mapping Industrial Clay Potential in the Minnesota River Valley
    (University of Minnesota Duluth, 1998-12) Zanko, Lawrence M; Oreskovich, Julie A; Heine, John J; Grant, James A; Hauck, Steven A; Setterholm, Dale R
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    Regional and Local Geologic, Mineralogic, and Geochemical Controls of Industrial Clay Grades in the Minnesota River Valley and the Meridian Aggregates Quarry, St. Cloud, Minnesota
    (University of Minnesota Duluth, 1991-07) Hauck, Steven A; Heine, John J; Shurr, George W; Toth, Thomas A; Tozer, Mary K; Victory, Denise A
    The purpose of this project is to determine the regional and local geological, mineralogical, and geochemical factors that control the distribution and grade of the industrial clays in the Minnesota River Valley (MRV) between Redwood Falls and Fairfax, Minnesota and at the Meridian Aggregates Quarry (MAQ), St. Cloud, Minnesota. These controlling factors fall into three broad categories: 1) bedrock controls - parent rock characteristics; 2) physical controls - faults, paleotopography, etc.; and 3) chemical controls.
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    Testing Of Selected Samples From Mapping Of Industrial Clay Potential In The Minnesota River Valley, South-Central Minnesota
    (University of Minnesota Duluth, 1999-08) Heine, John J; Zanko, Lawrence M
    As part of the mapping of industrial clay potential in the Minnesota River Valley (MRV) and Cottonwood River Valley (Zanko et al., 1998), 94 samples were collected for reference and future analysis. The primary focus of that study was to outline areas of potential for industrial clays, primarily kaolins, and ball clays, based on field observations and examining the water well logs for the area. The mapping project’s goal was to produce a GIS-based reference tool for land-use planning and clay exploration. This study was conducted to analyze 27 selected samples from Area 10 of Zanko et al. (1998), along the Cottonwood River in Brown County, Minnesota. This area was selected for additional work, based on field mapping, because of the high potential for the delineation of useful industrial clays. The lack of analytical data about the clays in this area made determining the potential of the area difficult. The clays included in the study are largely Cretaceous in age, Cretaceous sediments, and secondary sediments (Zanko et al., 1998), and a sample of an uncertain age, possibly a weathered Paleozoic shale. Most of these clays formed from the weathering and reworking of crystalline Archean bedrock, along with mineral contributions from weathered Paleozoic bedrock in the southeastern part of the study area. Similar Cretaceous clays are currently mined by the Ochs Brick and Tile Company, Springfield, Minnesota, and Minnesota Valley Minerals Inc., Mankato, Minnesota, for use in brickmaking and artistic ceramic clays. Other industrial clays in the area come from primary kaolin deposits, clays which formed in place from the intense weathering of crystalline Archean bedrock. No samples of primary kaolins are included in this study, but they do make up the largest tonnage of industrial clays mined in the MRV area, and are dominantly used in the production of portland cement.
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    Utilization of Minnesota Clays to Produce New Clay Products: Initial Research
    (University of Minnesota Duluth, 1989-11) Hauck, Steven A; Toth, Thomas A
    NRRI's mission was to evaluate the geologic, geochemical, mineralogical and physical characteristics of clays throughout the state of Minnesota. During the project period, the 499 clay samples collected represented primary and secondary kaolinitic clays, Cretaceous shales, glacial tills, loess and lake clays, Precambrian argillites and shales, and Paleozoic shales. In addition, detailed geologic mapping of existing clay mines was conducted to document the three dimensional relationships between the different types of samples.