Mottling and Iron Distribution in a Glossoboralf‐Haplaquoll Hydrosequence on a Glacial Moraine in Northwestern Wisconsin

Abstract

Distribution of iron oxide and forms of mottling and cutans under various moisture regimes were studied in a Woodfordian glacial moraine landscape. Hydrosequence members were observed and sampled along two transects in adjacent first‐order drainage basins. Considerable iron had been translocated out of the A horizon and either into the B horizon or out of the solum, in all pedons studied. Mottle development followed an expected systematic sequence from none at well‐drained (WD) sites, where unsaturated movement of water predominates; to considerable at somewhat poorly drained (SPD) sites, where saturated flow occurs frequently and where the dry‐wet cycle is characteristic; to few at very poorly drained (VPD) sites where gleying has been favored by stagnant water conditions in wet seasons. At WD sites mottles were either absent or of low chroma both in the interiors and on the faces of peds. At SPD sites mottles were of low chroma on ped faces and of high chroma inside peds, and Fe‐Me concretions were relatively abundant. At VPD sites neutral gray hues predominated both inside peds and on surfaces of macrospores, and there were only a few iron concretions or, at wettest sites, “pipestems.” Changes in distribution of iron extractable by aqua regia, dithionite and oxalate characterized the degree of crystallinity of iron compounds in the sequence. Iron oxides were most crystalline at WD sites where they tended to concentrate in the clay fraction. Iron oxides were concentrated in sand‐size concretions at SPD sites.