English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The stratigraphy of the Deep Sea Drilling Project/Ocean Drilling Program drill sites in the northern Shikoku Basin and Nankai Trough area are reviewed in the context of data from ODP Site 808, and interpreted with generalized depositional models for the Nankai Trough and Shikoku backarc basin. Backarc rifting between about 27 and 14 Ma caused the partitioning of the Shikoku Basin early in its history into a western (e.g., DSDP Sites 442 and 297) and eastern Shikoku Basin (e.g., DSDP Sites 443 and 444), separated by the linear and topographically high spreading ridge and the Kinan seamount chain. Pliocene terrigenous turbidites recovered at DSDP Site 297 appear to have been restricted to southwest of the spreading center; therefore, terrigenous turbidity currents coming from the Suruga Trough, to the east-northeast, do not appear to have been capable of overspilling the ridge crest, and if they overspilled the confines of the trench would have been confined to the eastern Shikoku Basin. We therefore believe that the terrigenous turbidites at Site 297 probably were delivered to the Shikoku Basin via Ashizuri Canyon at the western end of Shikoku, which lacks volcanoes of this time interval and is therefore a better candidate source for the more quartzofeldspathic sands rather than the Izu collision zone. Alternatively, another viable sediment source for these terrigenous turbidite sands is via a canyon from Kyushu. The ODP Site 808 stratigraphy shows that at about 300 k.y., major terrigenous sediment overspill occurred across the subducting, extinct, spreading ridge crest, marked by a prominent debris-flow event, associated with the abrupt southwestward progradation of the sandy trench-wedge turbidite system. As a consequence, the western and eastern parts of the Nankai Trough became linked depositional basins for the accumulation of terrigenous sands derived mainly from the Izu collision zone. At ODP Site 808, the geochemistry suggests that the source of the approximately 14-Ma rhyolitic pyroclastic unit immediately overlying the basaltic oceanic basement appears to have been different from that for the younger ash units higher up in the succession. A probable source for the rhyolitic pyroclastic unit may be related to the onland geology in Japan where circa-14-Ma unroofed granites occur on Kii Peninsula and in Kyushu. On Kii Peninsula, considerable volumes of middle Miocene pyroclastics remain, and therefore provide good temporal and spatial correlatives for the pyroclastics encountered at the base of ODP Site 808. Some of the subaqueous pyroclastics at Site 808 may also have come from submerged explosive volcanic centers to give reworked deposits. The Miocene volcaniclastics recovered from DSDP Site 297 also may be related to the rhyolites at ODP Site 808.

Stratigraphic Synthesis of the DSDP-ODP Sites in the Shikoku Basin, Nankai Trough, and Accretionary Prism