Extraterrestrial Material in Marine Sediments

Abstract

Marine sediments are the repository for most of the extraterrestrial material accreted by the Earth (Brownlee, 1981). Cosmic material in marine sediments includes megascopic meteorites and meteoritic fragments, microscopic meteoritic particles and spherules and microscopic glassy particles called microtektites. Most cosmic particles are magnetic, due to indigenous metallic iron or to magnetite formation during atmospheric entry. They therefore can be separated from sediments by magnetic methods (Brownlee, 1981). Although extraterrestrial material forms a tiny fraction of most marine sediments, it is concentrated in pelagic sediments with low sedimentation rates, deposited far from land (such as in the central Pacific).