Access Restriction

Author Chamley, Hervé ♦ Géochimie, Sédimentologie Et ♦ Cadet, Jean-Paul ♦ Charvet, Jacques
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Nankai Trough ♦ Dsdp Leg ♦ Japan Trench ♦ Restricted Southern Japanese Origin ♦ Subaerial Alteration ♦ Wide Range ♦ Argillaceous Diagenesis ♦ Turbiditic Sediment ♦ Ash Bed ♦ Hemipelagic Sediment ♦ Clay Association ♦ Late Cenozoic Clay Sedimentation ♦ Various Source ♦ Shikoku Basin ♦ Terrigenous Influ-ence ♦ High Sedimentation Rate ♦ Major Change ♦ High Submarine Relief ♦ Volcanic Influence ♦ Southern Margin ♦ Short Successive Step ♦ Tectonic Activity ♦ Island Arc Rock ♦ Middle Miocene ♦ Early Pleistocene ♦ Chiefly Illite ♦ Local Alteration ♦ Whole Northern Philippine Sea ♦ Clay Deposition ♦ Inner Part ♦ Mineralogic Transition ♦ Main Factor ♦ Pleistocene Sedimentation ♦ Minor Importance ♦ Clay Mineralogy
Abstract The clay mineralogy and morphology of DSDP Leg 87 sediments, studied from 200 samples and considered togeth-er with data from DSDP Legs 57 and 58, are discussed and interpreted in terms of paleoenvironment. Terrigenous influ-ence represents the main factor responsible for clay deposition in the Nankai Trough and Japan Trench, both marked by proximity to Japan, high submarine relief, and high sedimentation rates. The argillaceous diagenesis is of local or minor importance and includes the readjustment of fleecy to lathed smectites. The volcanic influence consists chiefly of a re-working of smectite developed by subaerial alteration of island arc rocks and secondarily of a local alteration of ash beds. The late Cenozoic clay sedimentation in the Nankai Trough (Sites 582 and 583) underwent a major change during the early Pleistocene. Hemipelagic sediments characterized by a wide range of minerals, derived from various sources charac-terizing the whole northern Philippine Sea (Leg 58 data), were replaced by turbiditic sediments with clay associations typical of a restricted southern Japanese origin (chiefly illite and chlorite). The mineralogic transition, which roughly parallels the lithologic one, occurs by short successive steps. It appears to express indirectly the tectonic activity of the southern margin of Japan, marked by the subduction of the Shikoku Basin and the formation of the Nankai Trough. Middle Miocene to Pleistocene sedimentation on the inner part of the Japan Trench (Site 584) corresponds to a regu-
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study