A determinative soil development index for pedo-stratigraphic studies

Abstract

Pedologists and Quaternary scientists working with stratigraphic columns which may include paleosols have need of a simple, quantitative procedure to distinguish paleosols from unweathered sediments and to represent the degree of soil development. Soil development indices which are most widely used have been derived for soil chronosequences on relatively stable landscapes and require that soil properties be compared to those of the parent material in order to quantitatively assess soil development. In studying stratigraphic columns, which may represent dramatically unstable landscapes, parent material may not always be readily determined, or there may be multiple soil parent materials which make a comparative approach untenable. This paper presents a determinative index based on morphological and micromorphological properties which are most effective in distinguishing “soil” from “non-soil”. This index successfully separated soils and paleosols from unweathered sediments in a stratigraphic sequence in northern New Hampshire. A Kruskal-Wallis test determined that means of index value groups which corresponded to sets of observed chemical and morphological soil properties were significantly different. This index was also successful in distinguishing independently-assessed morpho-genetic soil horizons and correlated well with Harden index values for a set of soil toposequences in southern Wyoming.