Subduction input (sediment before subduction)‐located seaward of the trench is one of the largest iodine budgets on the earth's surface. It is responsible for the deep iodine source in the landward of the trench where the iodine flux is significantly high. However, the distribution in the subduction input is poorly understood, contrary to the subducted sediment (sediment after subduction) landward of the trench. We determined...

The properties of host sediments and pore water considerably affect both the occurrence and formation processes of methane hydrate. In coarse‐grained layers, hydrates are generally concentrated preferentially in the pore space, and their formation is influenced by pore water salinity. To understand how geophysical and geochemical factors control the distribution of methane hydrates, we conducted numerical simulations using a o...

Summary Subseafloor pelagic sediments with high concentrations of organic matter form habitats for diverse microorganisms. Here, we determined depth profiles of genes for SSU rRNA , mcrA , dsrA and amoA from just beneath the seafloor to 363.3 m below the seafloor (mbsf) using core samples obtained from the forearc basin off the S himokita P eninsula. The molecular profiles were combined with data on lithostratigraphy, depositi...

The degree of gas hydrate saturation at I ntegrated O cean D rilling P rogram ( IODP ) S ite C 0002 in the K umano B asin, N ankai T rough, was estimated from logging‐while‐drilling logs and core samples obtained during IODP E xpeditions 314 and 315. Sediment porosity data necessary for the calculation of saturation were obtained from both core samples and density logs. Two forms of the Archie equation (‘quick‐look’ and ‘stand...