Weathering before the advent of land plants: Evidence from unaltered detrital K-feldspars in Cambrian-Ordovician arenites

Abstract

Potassium chelation by land plants and the consequent depletion of K + ion activity in soil waters make K-feldspars unstable in present-day soils. Other factors remaining constant, the absence of land plants in pre-Silurian time would make K-feldspars stable. Dissolution of plagioclase under the action of soil water would be the same in both pre- and post-Silurian time. The presence of abundant fresh K-feldspars and the absence of plagioclase in the Cambrian-Ordovician arenites of Ohio, Wisconsin, Minnesota, Missouri, Texas, Wyoming, and Montana are probably due to the absence of potassium chelating agents in the soils of the time.