Alluvial (Al-lu'-vi-al). A name, now obsolete, applied by Jameson (1808) from the teachings of A.G. Werner in the 1790's to the group or series of rocks consisting of unconsolidated or poorly consolidated gravels, sands, clays, and peat that were believed to have been formed after the withdrawal of the ocean from the continents. It constituted the fourth (following the Floetz ) of the divisions in which Werner placed the rocks of the geologic column. Syn: Tertiary.