USSSP-Participation in IODP Expedition 322 Nantroseize Stage 2 Subduction Input on the D/V Chikyu. Correlation Between Core, Log, and Seismic Data in Lower Shikoku Basin Sediments at IODP Site C0011

DESCRIPTION: This project will carry make rigorous, quantitative correlations between core data, logging-while-drilling data, and seismic data from cores to further document the pre-subduction inputs to the Nankai Trough.

OUTCOMES: Using an empirical relationship between electrical resistivity and porosity, the resistivity log was used to generate continuous downhole porosity and density curves for Site C0011 that show good agreement with core-based measurements where available. These new data provide insight into the intervals where fluid flow from the subducted material beneath the trench is focused. Using the porosity and P-wave velocity (Vp) relationship from the Shikoku Basin and other global compilations, a Vp curve was calculated for Site C0011. The log-derived Vp curve was used in conjunction with the resistivity-derived density curve to construct a synthetic seismogram to compare with seismic data through the subduction inputs transect across the Kashinosaki Knoll. The synthetic seismogram resolves a significant number of the strong reflections in the seismic stratigraphy. In particular, a contrast at ~250 mbsf is well resolved, likely correlating to a change in lithology from hemipelagic mud with abundant ash to mudstone with lesser ash (Lithologic Subunit 1A/B transition) identified by Expedition 333 Scientists. The new synthetic seismogram also resolves the strong reflections correlated to the sandstone unit of the middle Shikoku Basin facies (~350-400 mbsf) and the turbidite facies of the lower Shikoku Basin (>750 mbsf).