SECONDARY CARBONATES IN 3 FINE AND FINE-LOAMY ALFISOLS IN MICHIGAN

Secondary pedogenic carbonates are usually associated with ustic or dr ier soil moisture regimes; when found elsewhere. their interpretation can be troublesome. We studied three Alfisol pedons in Michigan that c ontained secondary carbonates on ped faces. The purpose of the researc h was to (i) characterize these accumulations, (ii) examine possible g enetic explanations for the accumulations, (iii) determine if these so ils have calcic horizons, given the recent redefinition of this diagno stic horizon, and (iv) evaluate how current ''k horizon'' nomenclature might apply to these soils. Three different drainage classes and two soil temperature regimes were represented in the sampled pedons: a fin e, mixed Glossic Eutroboralf; a fine, illitic, mesic Aquic Hapludalf; and a fine-loamy, mixed, mesic Aeric Endoaqualf. 411 three pedons had thin (<50 cm) leached zones near the surface, and carbonate coatings ( calcans) on ped faces within the lower B and/or upper C horizons. Two Of the three pedons had horizons that met calcic horizon criteria. Hor izons of preferential carbonate accumulation sometimes occurred near s ubtle textural breaks in the lower solum. Some B horizons in one pedon contained carbonate accumulations in amounts that exceeded that of th e presumed parent material. The calcans have probably resulted both fr om vertical translocation of carbonates, followed by precipitation at depth, as well as internal redistribution of carbonates from ped inter iors to ped faces. Use of the k subscript is warranted for some horizo ns in these soils. We recommend that its usage should be similar to t or s, i.e., horizons Kith evidence of secondary carbonates merit the k subscript.