Skip to Main Content
Book Chapter

Facies architecture, detrital provenance, and tectonic modulation of sedimentation in the Shikoku Basin: Inputs to the Nankai Trough subduction zone

Michael B. Underwood
Michael B. Underwood
Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, USA
Search for other works by this author on:
Kevin T. Pickering
Kevin T. Pickering
Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK
Search for other works by this author on:
Publication history
25 September 201714 March 2018


The Shikoku Basin is a back-arc basin located offshore southwest Japan. Sediments within the basin make up a key part of the subduction inputs to the Nankai Trough. A 19 m.y. history of sedimentation has been documented at Sites C0011 and C0012 of the Integrated Ocean Drilling Program (Kumano transect) and Sites 1173 and 1177 of the Ocean Drilling Program (Muroto and Ashizuri transects, respectively). This paper focuses on three noteworthy aspects of that history: (1) the onset of substantial pyroclastic influx, which shifted significantly along the strike length of the margin, from 3.3–3.9 Ma at Sites 1177 and 1173 to 7.6–7.8 Ma at Sites C0011 and C0012; (2) transport of sand by sediment gravity flows, which resulted in three discrete sand bodies during the Miocene (Kyushu, Daiichi Zenisu, and Daini Zenisu submarine fans); and (3) clay mineral assemblages within hemipelagic mudstones, which show systematic reduction of 3 wt% detrital smectite per 1 m.y. decrease in age. Collectively, these temporal and spatial adjustments of lithofacies and sediment composition have important implications for downdip and along-strike projections of frictional, geotechnical, and hydrogeological properties as strata enter the Nankai subduction zone. The stratigraphic positions of smectite-rich Miocene mudstones, for example, should match up with increases in the volume of fluid production by clay dehydration during subduction. The higher-permeability sand bodies (Kyushu and Zenisu submarine fans) should act as preferred conduits for focused fluid flow. The potential for buildup of fluid overpressures should increase above and laterally adjacent to stratigraphic pinch-outs of sand bodies, especially where the aquifers are inclined or confined between basement highs. These three-dimensional complexities set the Nankai-Shikoku system apart from other subduction zones (e.g., Japan Trench, Costa Rica) where inputs consist of comparatively homogeneous pelagic and hemipelagic deposits.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables


GSA Special Papers

Geology and Tectonics of Subduction Zones: A Tribute to Gaku Kimura

Geological Society of America
ISBN electronic:




A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal