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Clay Sedimentation and Paleoenvironment in the Shikoku Basin since the Middle Miocene (Deep Sea Drilling Project Leg 58, North Philippine Sea)
| Content Provider | Semantic Scholar |
|---|---|
| Author | Chamley, Hervé |
| Copyright Year | 1980 |
| Abstract | Clay sedimentation in Shikoku (back-arc) Basin began in the early middle Miocene; this sedimentation was accompanied by basaltic intrusions, with moderate alteration under closed conditions (smectite, sometimes chlorite and talc). After a short period of sedimentation of brown pelagic clay, dominated by in situ smectite formation, hemipelagic deposits become common at DSDP Sites 442, 443, and 444; these deposits show various and diachronous mineralogical changes. Miocene sedimentation was influenced by volcanism; volcanogenic materials were derived chiefly from adjacent volcanic arcs by subaerial alteration and erosion. Latest-Miocene to Pleistocene clay sedimentation was progressively influenced by continental climatic factors (irregular world cooling). The major sources of clay minerals in Shikoku Basin are recognized: illite and chlorite from Japan; smectite from volcanic arcs; kaolinite supplied from the southwest by the Kuroshio Current, whose influence probably starts from the initiation of the marine basin; vermiculite, attapulgite, and most of the irregular mixed-layer clays from Asia. The main sources of detritus changed with time, mainly because of vertical movements of volcanic ridges, forming temporary barriers against oceanic circulation. The Iwo Jima and Kyushu-Palau ridges emerged during the Miocene, and the Kyushu-Palau Ridge subsided in two major stages during the Pleistocene. Thus the sedimentary clays of Shikoku Basin, for the middle Miocene to the present, are indicators of geodynamics, currents, and climate. INTRODUCTION AND METHODS During DSDP Leg 58, three sites in the vicinity of the expected spreading center of Shikoku inter-arc basin were drilled in the northern Philippine Sea. At Sites 442, 443, and 444 a subcontinuous Miocene to Pleistocene series overlying oceanic basalts was penetrated (see site chapters, this volume). Site 442 lies on the eastern flank of the submerged Kyushu-Palau ridge, whereas Sites 443 and 444 are on a clastic wedge bordering the Iwo Jima-Bonin Ridge (Figure 1). Methods are explained in the companion paper by Chamley in this volume. |
| File Format | PDF HTM / HTML |
| DOI | 10.2973/dsdp.proc.58.118.1980 |
| Alternate Webpage(s) | http://deepseadrilling.org/58/volume/dsdp58_18.pdf |
| Alternate Webpage(s) | https://doi.org/10.2973/dsdp.proc.58.118.1980 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
