ABSTRACT

Studies of vertical profiles of quartz-rich Ultisols of the Carolina piedmont and coastal plain reveal patterns of grain dissolution which may be used as an indicator of weathering intensity. The formation of sand-sized material begins with the dismemberment and dissolution of the saprolite and parent rock and forms grains with solution embayments. Further dismemberment occurs until grains show very irregular and skeleton-like outlines. Skeletal grains characterize the root zone which is probably the zone of greatest solution activity. The repetitive nature of the observed patterns of dissolution and grain production enables one to formulate a model based on the degree and the amount of embayed quartz in the soil. The model proposes that after the initial release of the fragment, it i further modified by the soil water and as time proceeds and dismembering of the fragments occurs, dissolution at the grain contacts continues. Eventually, as the zone of greatest activity develops, it is possible that a soil profile consisting dominantly of embayed monocrystalline quartz would develop.