STONELAYERS (STONE-LINES): A PRIORI ASSUMED TO BE BASAL PARTS OF BIOMANTLES

Basal stonelayers (stone-lines) are common in biomantles of soils that form in mixed clast sediments in many subaerial and subaqueous environments. On land, biomantles that contain stonelayers occur on all continents -- except possibly Antarctica. On stable continental surfaces of the humid tropics and subtropics, biomantles not uncommonly are meters thick, and their basal pedogenic stonelayers commensurately meters deep. In the midlatitudes biomantles are typically thinner, and their stonelayers typically shallower. Biomantle thickness largely reflects the dynamic interplay between bioturbation and erosional removals. In the upper Midwest biomantles with stonelayers are well expressed in the upper part of Sangamon soils formed in Illinois drift -- formerly called the 'ferretto zone' with 'pebble band'. Biomantles with stonelayers are also well expressed in Holocene (modern) soils formed in pre-Illinoisan drift on the Iowan surface, and in modern soils formed in Wisconsinan drift of the Des Moines lobe. Utilizing this dynamic pedogenic approach provides views of Quaternary landscape evolution that are fundamentally different, and we believe more realistic, than those provided by a pedimentation-pedisedimentation (geogenic) approach.