The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a multidisciplinary investigation of fault mechanics and seismogenesis along subduction megathrusts and includes reflection and refraction seismic imaging, direct sampling by drilling, in situ measurements, and long-term monitoring in conjunction with laboratory and numerical modeling studies. The fundamental objectives of NanTroSEIZE are to characterize the nature of fault slip and strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. As part of the NanTroSEIZE program, operations during Integrated Ocean Drilling Program (IODP) Expedition 348 were planned to extend and case riser Hole C0002F, begun during IODP Expedition 326 in 2010 and continued during Expedition 338 in 2012, from 860 to 3600 meters below the seafloor (mbsf).Riser operations during Expedition 348 were carried out and deepened the hole to 3058 mbsf, a new maximum depth record in scientific ocean drilling. Operations included installation and cementing of 13 3 ⁄8 inch casing to 2008.9 mbsf and an 11¾ inch liner to 2922.5 mbsf, stabilizing the borehole for future deepening. Reaching this depth required two sidetracking operations from the original Hole C0002F, resulting in the designation of Holes C0002N and C0002P for the successively deeper sidetracks. During drilling, a suite of logging-while-drilling (LWD) and measurement-while-drilling (MWD), mud-gas, and cuttings data were collected over the interval from 2162.5 to 3058.5 mbsf in Hole C0002P, and a partial suite was collected in Hole C0002N. The interval from 2163 to 2218 mbsf was cored with the rotary core barrel (RCB). Planned future riser drilling operations will deepen the hole to penetrate the plate boundary fault at ~4600-5200 mbsf.Additionally, a test hole for a prototype slimhole small-diameter RCB (SD-RCB) coring system, Hole C0002M, was drilled in riserless mode near Hole C0002F. The hole was advanced to 475 mbsf, where four cores were collected to 512.5 mbsf.Overall, Expedition 348 sampled and logged a deep interval in Holes C0002N and C0002P within the inner accretionary wedge, from 856 to 3058.5 mbsf, including a never-before sampled zone in the lowermost ~1 km of drilling. Cores were collected over a 55.5 m interval from 2163 to 2218.5 mbsf. The sampled sedimentary rocks are composed of hemipelagic sediment and fine turbi-

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Multidimensional spectrofluorometry was employed to characterize dissolved organic matter (DOM) in arsenic-contaminated shallow aquifers at Jianghan Plain (JHP), central China, to better understand the effect of biogeochemical processes on arsenic mobilization. The microbial humic quinone and amino acid components identified indicate the importance of microbially mediated processes in the reduction of iron oxyhydroxides. The relationship of quinone and amino acid-like components with Fe(2+) and S(2-) helps us understand the sequential redox transformation (SRT) in the high arsenic aquifer system and the origin of bicarbonate in groundwater. Correlation between DOM components and dissolved arsenic and Fe suggests that arsenic mobilization could be linked to the microbial reduction of iron oxyhydroxides with liable DOM as electron donors as well as to the electron shuttling function served by humic quinones.

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