The concentration of hydrogenous (authigenic) elements such as Mn, Co, and Ni in sediments has a relationship to the bulk sedimentation rate. New indicator to measure sedimentation rate of terrigenous materials in sediments: expressed as the weight ratio of a hydrogenous element to TiO (sub 2) . The ratio varies according to depositional environments. Geochemical examination of Pacific DSDP materials has shown that the distribution of element ratios (MnO/TiO (sub 2) , Co/TiO (sub 2) , and others) in surface sediments of the Pacific has not changed since the Middle Cretaceous. Applications: (1) estimating sedimentation rates of ancient sedimentary rocks on land, (2) assessing the depositional environment of geosynclinal cherts, and (3) examining subduction process at the Japan Trench. Ophiolite suites are not always oceanic crust segments generated at a mid-ocean ridge. Plate tectonic orogenic model based on a hypothesis of offscraping mechanism at a plate convergence should be re-examined.--Modified journal abstract.