Data report: consolidation and permeability of sediments from Sites C0011, C0012, and C0018, IODP Expeditions 322 and 333, NanTroSEIZE Stage 2

Abstract

This report documents the results of constant-rate-of-strain consolidation tests on mud and mudstone samples from the Kumano transect of the Nankai subduction margin. The coring sites include Integrated Ocean Drilling Program Sites C0011 and C0012 in the Shikoku Basin (subduction inputs) and Site C0018 in a small basin on the landward tren ch slope. Samples from Sites C0011 and C0012 yielded compression indexes of 0.31 to 2.70 (average = 0.99); values generally decrease with increasing depth. Values of in situ intrinsic permeability at Site C0012 range from 3.03 × 10 –15 m 2 to 3.65 × 10 –19 m 2 and decrease erratically with depth. Comparable values at Site C0011 decrease steadily with depth and range from 1.17 × 10 –16 m 2 to 1.57 × 10 –19 m 2 . At both sites, overconsolidation ratios (maximum past effective normal stress to computed values of in situ hydrostatic vertical effective stress at equivalent depths) are indicative of apparent overconsolidation. At Site C0018, values of compression index range from 0.42 to 0.60 (average = 0.53), with no obvious trend as a function of burial depth. Values of in situ intrinsic permeability decrease with depth from 3.33 × 10 –16 m 2 to 1.47 × 10 –17 m 2 , and the overconsolidation ratio varies from 0.76 to 1.82, indicating that the specimens are slightly underconsolidated to moderately overconsolidated.