Evolution of tectono-sedimentary systems in the Kumano Basin, Nankai Trough forearc

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doi: 10.1016/j.marpetgeo.2015.05.032
Author(s): Moore, G. F.; Boston, B. B.; Strasser, M.; Underwood, M. B.; Ratliff, R. A.
Author Affiliation(s): Primary:
University of Hawaii, Department of Geology and Geophysics, Honolulu, HI, United States
Other:
Eidgenössische Technische Hochshcule Zürich, Switzerland
New Mexico Institute of Mining and Technology, United States
Ratliff Geological Consulting, United States
Volume Title: Marine and Petroleum Geology
Source: Marine and Petroleum Geology, Vol.67, p.604-616. Publisher: Elsevier, Oxford, United Kingdom. ISSN: 0264-8172
Note: In English. 91 refs.; illus., incl. sects., sketch map
Summary: Sedimentary deposits in the distal Kumano forearc basin of the Nankai accretionary margin off Kii Peninsula, Japan, have been imaged using three-dimensional (3D) seismic data. The seismic data, along with logging and core data from the Integrated Ocean Drilling Program (IODP) show that the unconformity between the accretionary prism and overlying forearc sediments is time-transgressive. The unconformity at Site C0002 separates 5 Ma prism rocks from 3.65 Ma basin deposits; at Site C0009 it separates 5.6 Ma prism from 3.8 Ma basin sediments. Acoustic reflections in the basal deposits are sub-parallel to the underlying accretionary prism; the acoustic facies varies in thickness from 50 to 750 m. The mudstone deposits and laterally equivalent turbidites are interpreted as lower trench-slope deposits. The condensed slope sediment (SS) section decreases in age from 3.5 to 1.5 Ma at Site C0002 to 1.5-0.9 Ma at C0009. Acoustic sequences within the lower forearc basin (LFB) contain higher proportions of silt and sand turbidites and progressively onlap the SS unit along a low-angle discontinuity (KL) in a landward direction. Because of the landward onlap of the LFB unit, the oldest LFB strata at C0002 are older than 1.67 Ma, whereas those at C0009 are younger than ∼0.9 Ma. Thus, the amount of time missing or characterized by condensed sedimentation across the KL unconformity decreases in duration in the landward direction. The landward-onlapping sequences tilt progressively landward in response to regional uplift along an out-of-sequence thrust (OOST; mega-splay) fault. Regional tilting shifted the basin's depocenter progressively landward, expanding that part of the basin from ∼10 km in width to >30 km. The onset of sand-silt turbidite deposition in the distal basin began after more accommodation space was created by the uplift of the outer ridge along the splay fault at ∼1.9 Ma. Conversely, turbidites of the Upper Forearc Basin (UFB) progressively onlap LFB in a seaward direction. Furthermore, the respective thicknesses of the LFB and UFB units switch from the seaward side of the basin (C0002) farther landward (C0009): the LFB unit is > 800 m thick in the seaward region, whereas it is only 200-300 m thick in the landward region; the UFB unit is < 50 m thick in the seaward region, and up to 600 m thick in the landward region. Thus, Kumano Basin responded in both space and time to a complex interplay between tectonics and sedimentation. The stratigraphy records a balance between the effects of prism uplift along the basin's distal edge with the rerouting of channels and canyons along the basin's proximal edge.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 20 Geophysics, Applied; Accretionary wedges; Asia; Basins; Cenozoic; Cores; Expedition 315; Expedition 319; Far East; Fore-arc basins; Geophysical methods; Geophysical profiles; Geophysical surveys; Honshu; IODP Site C0002; IODP Site C0009; Integrated Ocean Drilling Program; Japan; Kii Peninsula; Kumano Basin; Marine sediments; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Pacific Ocean; Sedimentary basins; Sediments; Seismic methods; Seismic profiles; Seismic stratigraphy; Surveys; Tectonostratigraphic units; West Pacific
Coordinates: N331800 N331801 E1363801 E1363800
N332728 N332728 E1363209 E1363209
Record ID: 2016068613
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands