Texture, Mineralogy, and Lamellae Development in Sandy Soils in Michigan

The texture, mineralogy, and to a lesser extent topography, of some sandy soils in Michigan were examined to determine the possible genesis of lamellae in these soils. Differences in lamellae presence and depth were studied in four Haplorthods, one Argic Udipsamments, and one Psammentic Eutroboralf on a subtly undulating lake terrace in northern lower Michigan. Dolomite or feldspar weathering was not pronounced in these well-drained soils; one pedon retained substantial carbonates at depth, probably mainly within lamellae. Significant correlations (r) were observed between the depth to the uppermost textural band (an indication of the amount and development of lamellae for the entire profile) and profile-weighted contents of the following size separates: <50 µm (−0.82*, significant at P < 0.05), < 125 µm (−0.92*), 250-2 µm (−0.90*), and 2000-500 µm (0.96**, significant at P < 0.01). Correlations between clay content and depth to first lamella were not significant (r = −0.72), suggesting that sandy pedons dominated by fine sands and silts are more likely to have lamellae than are those with more clay. Clay inberited from the parent material was probably rapidly translocated downward to form lamellae; deep translocation out of the solum is especially plausible in the coarser textured Haplorthods. Deposition of clay in textural bands is probably due, initially, to cessation of wetting fronts or flocculation by carbonates. Sieving processes may act to thicken these features, especially in finer textured pedons. Lithologic discontinuities may have also affected lamellae formation by stopping wetting fronts at or near sites of textural change. Topographic factors also contributed to lamellae formation; pedons within and near a small depression had thicker and shallower lamellae than did those on uplands, possibly due to lateral translocation of colloids.