ABSTRACT

Many sediments, including the fine-grained pelagic deposits, possess polymodal grain size distributions. Resolution of individual modes show them to be related either to compositional fractions or to depositional processes or both, and sometimes permits the tracing of dispersal patterns. The sedimentation balance provides a means of obtaining continuous cumulative size distribution curves of fine-grained sediments. The resultant cumulative curve is processed by computer to yield a size frequency curve which is often polymodal. This frequency curve is resolved into its individual components by analog computer. The method is discussed briefly and illustrated by a study of pelagic sediments from the Northwest Pacific. Samples collected nearest land have the most components and the best s rted components. Fifteen modes were decanted from five samples and X-rayed. Components from different samples were found to have similar compositions when plotted on a feldspar-kaolinite-mica ternary diagram. Based on like composition and nearly identical mean size values, it is possible to trace the sedimentary components from sample to sample.