The origin of strata within the inner accretionary prism of Nankai Trough; evidence from clay mineral assemblages along the NanTroSEIZE transect

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doi: 10.1111/iar.12252
Author(s): Underwood, Michael B.
Author Affiliation(s): Primary:
New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, Socorro, NM, United States
Volume Title: Island Arc
Source: Island Arc, 27(3). Publisher: Wiley Blackwell on behalf of Geological Society of Japan, Tsukuba, Japan. ISSN: 1038-4871
Note: In English with Japanese summary. 90 refs.; illus., incl. sects., sketch maps
Summary: One of the more prominent architectural elements of the Nankai subduction margin, offshore southwest Japan, is an out-of-sequence thrust fault (megasplay) that separates the inner accretionary prism from the outer prism. The inner prism (hanging wall of the megasplay) is dominated by mudstone, which is enigmatic when the sedimentary facies is compared to coeval deposits in the Shikoku Basin (i.e. inputs from the subducting Philippine Sea plate) and to coarser-grained turbidite sequences from the Quaternary trench wedge. Clay mineral assemblages amplify the mismatches of sedimentary facies. Mudstones from the inner prism are uniformly depleted in smectite, with average bulk values of 23-24 wt%, whereas the Shikoku Basin deposits show progressive decreases in proportions of smectite over time, from averages of 46-48 wt% at 10 Ma to 17-21 wt% at 1 Ma. Plate-boundary reconstructions for the Philippine Sea region provide one solution to the conundrum. Between 15 Ma and 10 Ma, the Pacific plate subducted near the NanTroSEIZE transect, and a trench-trench-trench triple junction migrated to the northeast. Accretion during that period involved sediments that had been deposited on the Pacific plate. Motion of the Philippine Sea plate changed from 10 Ma to 6 Ma, resulting in sinistral slip along the proto-Nankai Trough. Sediments accreted during that period probably had been deposited near the triple junction, with a hybrid detrital provenance. Renewed subduction of the Philippine Sea plate at 6 Ma led to reorganization of watersheds near the Izu-Honshu collision zone and gradual incision of large submarine canyons on both sides of the colliding Izu arc. Accreted Pliocene mudstones share more of an affinity to the triple junction paleoenvironment than they do to Shikoku Basin. These differences between subducting Shikoku Basin strata and accreted Pacific plate sediments have important implications for interpretations of frictional properties, structural architecture, and diagenetic fluid production. Abstract Copyright (2018), John Wiley & Sons, Ltd.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Accretionary wedges; Cenozoic; Clay mineralogy; Clay minerals; Expedition 315; Expedition 322; Expedition 333; Expedition 338; Expedition 348; Faults; Geotraverses; Hemipelagic environment; IODP Site C0001; IODP Site C0002; IODP Site C0011; IODP Site C0012; Illite; Integrated Ocean Drilling Program; Kumano Basin; Leg 190; Marine environment; Megasplay faults; Miocene; NanTroSEIZE; Nankai Trough; Nankai subduction zone; Neogene; North Pacific; Northwest Pacific; ODP Site 1173; ODP Site 1177; Ocean Drilling Program; Pacific Ocean; Pacific Plate; Philippine Sea Plate; Plate boundaries; Plate tectonics; Pliocene; Provenance; Quaternary; Sedimentation; Sheet silicates; Shikoku Basin; Silicates; Smectite; Subduction zones; Tertiary; West Pacific
Coordinates: N331400 N331801 E1364300 E1363800
N324453 N324945 E1365501 E1365254
N313900 N321500 E1350200 E1340000
Record ID: 2019010332
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom