The detrital composition of siliciclastic rocks from six localities in the Taconic and Acadian sections of New York and Quebec can be described as mixtures of two or more differentiable sedimentary components. A sedimentary component is defined as a mineral or group of minerals that sort independently of other sedimentary constituents. Because of grain morphology, phyllosilicates usually dominate the finer-grained component, and quartz or mixtures of quartz and feldspar dominate the coarser-grained components. The chemical composition of a sedimentary component is distinctive, and the differentiation of sedimentary components usually results in the concomitant separation of associated elements. Typical separations include the enrichment of K 2 O and Al 2 O 3 in the finer-grained, phyllosilicate-rich fraction and the enrichment of SiO 2 and Na 2 O in the coarser-grained, tectosilicate-rich fraction. Fe 2 O 3 and MgO are also enriched in the fine fraction, if they are abundant constituents in the phyllosilicates. The chemical composition of the graywackes from North America was compared to the chemical composition of unlithified turbidite sediments from the Black Sea. The chemical variation trends found in the deeply buried sedimentary rocks are similar to the trends found in the suite of slightly buried and unlithified deep-sea sediments. This indicates that burial alteration does not necessarily result in large-scale redistribution of the constituent elements. It is possible, therefore, to use the chemical variations observed in a suite of deeply buried and mineralogically altered sedimentary rock to infer the original clastic assemblage and to help clarify the processes that produced the sediment.