Provenance and depositional processes of tephras and Tertiary volcaniclastic sandstones from IODP Expedition 322, Nankai Trough
Final Report Abstract
During Nankai IODP Expedition 322 sediments down to the early Miocene have been drilled which allow constraining the physical, compositional and structural characteristics of the subduction input into the seismogenic zone. Based on sediment compositions, sediment textures, and sedimentary structures we contributed to the determination of the depositional history of the Shikoku basin that is a prequisite to understand the beaviour of the downgoing plate in the seismogenic zone. We also identified a mixed Paleo-Honshu and Izu-Bonin arc provenance of 4 tuffaceous sandstone beds characterizing late Miocene Unit IIa, whereas the older tuffaceous sandstone bed 3b has an Izu-Bonin and the younger tuffaceous sandstone beds 1 to 3a have a Paleo-Honsu arc source. We showed their origin from voluminous explosive eruptions and their emplacement as terrigenous primary pyroclastic flows that have transformed into submarine pyroclastic density currents at the shore line and traveled subsequently 350 km on the ocean floor until their deposition. We have been preliminarily been able to constrain source areas for tephra layers found within the Quaternary to Pliocene sediments of Legs 322 and 333 which assist also the findings of mixed Honshu-Izu-Bonin provenance in Unit II. Tephra inventories of older ODP and DSDP sites in that region but also from Neogene slope sediments at Boso and Miura peninsula at todays Japanese coast correlates with the tephras found during Expeditions 322 and 333. Time periods influenced stronger from Honshu sources alternate with phases predominantely fed by Izu-Bonin tephras. Cooperation’s with other 322 scientists additionally resulted in provenance signals inside the dispersed tephras, indicated alteration effects within the incoming plate volcanics, facilitated comparison of halogens in solid and fluid phases of the sediments, and initiated several research topics awaiting for additional analysis and samples. These topics show a wide spectrum of research from high-resolution geochemical signatures in the sediments investigating also their cyclicity, to the investigation of isothermal remnant magnetization and rock magnetic characterization of sediments. Future research in this region (IBM cruises; PI Kutterolf and Julie Schindlbeck will participate) and ongoing collaborations on the open topics will therefore be continued in the next years and probably help to solve the remaining questions. The project was very successful within the limits of sample quality and the normal fluctuation of IODP post cruise research personal. We succeeded in recruiting a very promising PhD student who is using parts of the results for her PhD thesis and we initiated long-living cooperation’s with Scudder and Murray from Boston University and Yamamoto from JAMSTEC that have and will be continued in other projects related to IODP (KAP, CRISP, IBM).
Publications
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(2013) Emplacement processes of submarine volcaniclastic deposits (IODP Site C0011, Nankai Trough). Marine Geology, 343, 115-124
Schindlbeck J.C., Kutterolf S., Freundt A., Scudder R.P. Pickering K.T., Murray R.W.
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(2013), Depositional architecture, provenance, and tectonic/eustatic modulation of Miocene submarine fans in the Shikoku Basin: Results from Nankai Trough Seismogenic Zone Experiment. Geochemistry, Geophysics, Geosystems, 14, 1722-1739
Pickering, K.T., Underwood, M.B., Saito, S., Naruse, H., Kutterolf, S., Scudder, R., Park, J.-O., Moore, G.F. & Slagle, A.
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Large volume submarine ignimbrites in the Shikoku Basin: An example for explosive volcanism in the Western Pacific during the late Miocene. Geochemistry, Geophysics, Geosystems, Volume 15, Issue 5, May 2014, Pages 1837-1851
Steffen Kutterolf, Julie C. Schindlbeck, Rachel P. Scudder, Richard W. Murray, Kevin T. Pickering, Armin Freundt, Shasa Labanieh, Ken Heydolph, Sanny Saito, Hajime Naruse, Michael B. Underwood, Huaichun Wu
