Mineral Content and Distribution as Indexes of Weathering in the Omega and Ahmeek Soils of Northern Wisconsin

L. D. Whittig1 and M. L. Jackson
University of Wisconsin, Madison, Wisconsin
1 Present address, Soil Survey Laboratory, Soil Conservation Service, Beltsville, Maryland.

Abstract: Quantitative estimation of mineral concentrations was made for the clay fractions of Omega loamy sand (Brown Podzolic) and Ahmeek loam (Brown Forest). These soils are relatively young and have developed from Pleistocene (late Wisconsin) outwash and till, respectively, in northern Wisconsin. A mineral weathering depth function was found, in which illite and chlorite present at depth have weathered to vermiculite and montmorillonite nearer the surface, particularly in the clay fractions of Ahmeek loam. In the fine clay, the montmorillonite content increases from 5 percent in the C1 horizon to 44 percent in the A1 horizon. Conversely, chlorite decreases from 11 percent in the C1 to virtually none in the A1 horizon. Weathering in these soils is also reflected by distribution of minerals as a function of particle size. The occurrence of mineral-weathering depth and size functions in these young soils is attributed to accelerated leaching made possible by the coarse texture of the soils.

Clays and Clay Minerals; 1955 v. 4; no. 1; p. 362-371; DOI: 10.1346/CCMN.1955.0040140
© 1955, The Clay Minerals Society
Clay Minerals Society (www.clays.org)