added by archaeologs A term no longer used to describe the final stages of the Neolithic A Group in Nubia (c 2800-2300 BC), prior to the beginning of the C Group phase. In soils, the B horizon lies immediately beneath the A horizon and may reach a depth of 65 to 90 centimeters (26 to 35 inches). It is a zone of more moderate weathering in which there is an accumulation of many of the products removed from the A horizon.