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Please use this identifier to cite or link to this item: http://hdl.handle.net/11299/59140

Title: Guidebook 19. Field Trip Guidebook Kaolinitic Clays of the Minnesota River Valley and Southwestern Minnesota
Authors: Setterholm, Dale R.
Heine, John J.
Keywords: geology
southwestern Minnesota
Minnesota Geological Survey
kaolinitic clay
kaolinite
Minnesota River Valley
Issue Date: 1992
Publisher: Minnesota Geological Survey
Series/Report no.: Guidebook
19
Abstract: 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.
Description: PREPARED FOR THE 29TH ANNUAL MEETING OF THE CLAY MINERALS SOCIETY AND THE SOIL SCIENCE SOCIETY OF AMERICA MINNEAPOLIS, MINNESOTA, 1992
URI: http://purl.umn.edu/59140
ISSN: 0192-6268
Appears in Collections:Guidebook Series

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