Amazonian Dark Earths

Abstract

Amazonian dark earths (ADEs) are expanses of pre‐Columbian anthropic soils mostly reported at, or close to, the land surface of Tertiary Age, nonflooding terrain of eastern and southern Amazonia. In the field, the first salient characteristic of ADE is strong melanization of the topsoil. A small number of soil micromorphological studies have been conducted on pre‐Columbian anthropic soil expanses from the Brazilian Amazon. Except where inputs of alluvial sediments directly affect the locale where an ADE expanse has formed, soil micromorphological studies suggest that thick melanized ADE layers are not the result of additions of mineral sediments of a different geological origin. All studies coincide that melanization is a result of the combined effect of intense staining with organic matter of the fine mineral fraction, coupled with the ubiquitous presence of microscopic charcoal fragments.