Abstract
This paper deals with the development of the microfabric of hemipelagic clay during the early compaction stage. Materials used are core samples ca. 30 cm long, composed of homogeneous hemipelagic clay, collected from the superficial layer of ocean bottom sediments in the Okinawa Trough, Japan. Architecture of constituent particles, together with void ratio, shear strength and anisotropy of magnetic susceptibility (AMS), was analyzed in the core samples. Void ratios decrease downward through ca. 6-4 to ca. 4-2 at ca. 5 cm in burial depth. Shear strengths increase exponentially through ca. 0 kPa to ca. 6 kPa downward at ca. 10 cm in burial depth. The AMS parameters are rather constant throughout the column, suggesting no significant particle re-orientation of magnetic minerals by compaction. The microfabric of the samples is characterized mainly by the combination of peds and connectors. A ped is an aggregation of clay particles, and a connector is train of particles which connect peds successively to each other. The particles of the connector in the superficial layer within 6 cm in depth are linked each other by edge-to-edge and edge-to-face contacts. The architecture of the connectors changes to edge-to-face and face-to-face linkage with burial compaction. Thus, the increase of shear strength and the decrease of void ratio are resulted from this change of the connector's architecture.
