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Site U1450 (proposed Site MBF-2A) occupies a central position at 8°0.42′N and 87°40.25′E in the east–west transect across the Bengal Fan at 8°N. It is located at equal distance from Site U1451 on the flank of the Ninetyeast Ridge and Site U1455 on the flank of the 85°E Ridge. The overall thickness of the fan reaches ~4 km at this location (Curray et al., 2003). Neogene sediment thickness decreases toward the two ridges, which is likely the result of ongoing deformation on both ridges during the Neogene (Schwenk and Spiess, 2009). At this central position of the transect, the upper Miocene and Pliocene–Pleistocene sections of the fan appear to be most expanded and are inferred to contain a higher resolution record, as well as accumulating, on average, coarser grained material. The shallow section at this site is one of the seven ~200 m deep sections along the 8°N transect that constrain the Middle Bengal Fan architecture in space, time, and sediment delivery rate during the Pleistocene. The deeper section at this site will document the delivery mechanisms of the fan and the climatically and tectonically influenced sediment supply from the Himalaya during the Neogene. Changes in the source regions in response to tectonic and climatic evolution of the Himalaya are expected to be reflected in the sediment’s mineralogical and geochemical compositions, the geochronological data, and in accumulation rates across the transect. 

Site U1455 (proposed Site MBF-1A) is the last site drilled during Expedition 354 in the Bengal Fan. It is a reoccupation of Deep Sea Drilling Project (DSDP) Site 218 (see Figure F11 in the Expedition 354 summary chapter [France-Lanord et al., 2016e]) (von der Borch, Sclater, et al., 1974), which was the first attempt to drill the Bengal Fan and was only spot cored with the rotary core barrel (RCB) system to 773 meters below seafloor (mbsf). The site is above the eastern flank of the 85°E Ridge at 8°0.42′N, 86°16.97′E at 3743 m water depth. Site U1455 is one of three deep-penetration sites along the Expedition 354 transect dedicated to reveal Neogene fan evolution and Himalayan erosion. This site will also document Pleistocene fan architecture when integrated into the complete seven-site transect. Coring to 900 mbsf was planned to determine Miocene to Pliocene accumulation rates and changes related to Himalayan erosion and environment. The deeper part of the site will extend the existing Site 218 record back into the middle Miocene. Because of time constraints at the end of the expedition, we focused coring on three objectives: the Pleistocene (0–122 mbsf), the late Miocene terrestrial vegetation transition from C3 to C4 plants (360–431 mbsf), and the middle Miocene (773–949 mbsf) to extend the existing core record of Site 218. 

Site U1453 (proposed Site MBF-4A) is in the center of our seven-site transect of shallow-penetration holes. It is located at 8°0.42′N, 86°47.90′E in a water depth of 3690.5 m. Combined with the other transect sites, Site U1453 will document depocenter migration and quantify overall sediment delivery to 8°N since the Pleistocene. Site U1453 is located ~1 km south and ~5 km east of a prominent surficial channel. The channel exhibits pronounced meandering point bars and internal terraces. Sediment transported by this channel has therefore significantly influenced deposition at this site during the channel’s lifetime. A prominent buried point bar is located <1 km west of the site. The overall seismic reflectivity at the drill site is relatively high, indicating coarse material throughout most of the drilled section, except for the lower portion of the drill hole. Distinct and variable local spillover deposits were expected at the site in response to the channel and meander evolution. Toward the base of the hole, lower seismic reflectivity and distinct layering is inferred to reflect hemipelagic or distal levee deposition. In addition to coring, downhole logging was introduced as an important objective of Site U1453 after attempts to log at Sites U1450 and U1451 were unsuccessful. Logging data are essential for determining the inventory of lithofacies and structures in the fan given the limitations in completely recovering unconsolidated coarse material and the importance of measuring in situ physical properties and imaging fine-scale sedimentary structures. Therefore, we decided to log Hole U1453A despite its shallow ~215 m penetration to increase chances that we could acquire this critical in situ log data. This was particularly important for characterizing the in situ properties of thick sandy intervals that half-length advanced piston corer (HLAPC) cores returned as loose and liquefied sand. 

This chapter documents the procedures and methods employed in the various shipboard laboratories on the R/V JOIDES Resolution during International Ocean Discovery Program (IODP) Expedition 354. This information applies only to shipboard work described in the Expedition Reports section of the Expedition 354 Proceedings of the International Ocean Discovery Program volume. Methods used by investigators for shore-based analyses of Expedition 354 data will be described in separate individual publications. This introductory section provides an overview of operations, curatorial conventions, depth scale terminology, and general core handling and analyses. 

Site U1451 (proposed Site MBF-3A) is the easternmost site of our Bengal Fan transect at 8°N and was the only one aimed at coring the oldest part of the fan. The site is located above the western flank of the Ninetyeast Ridge at 8°0.42′N, 88°44.50′E in 3607.3 m water depth. Seismic data show that the overall fan section is condensed at Site U1451 compared to the axial part of the fan because of ongoing deformation along the Ninetyeast Ridge since the Miocene (Schwenk and Spiess, 2009). The drilling objective was to recover the complete fan section down to a seismic unconformity, which is believed to indicate the onset of fan deposition at this location. Site U1451 also contributes to the Miocene–Pliocene transect of three ~900 m deep holes documenting Himalayan erosion and paleoenvironment. Finally, the upper section of the site is part of the seven-site transect drilled to investigate late Pliocene to recent depocenter migration and overall fan sedimentation. 

Site U1454 (proposed Site MBF-7A) is the westernmost of the transect of seven shallow-penetration sites drilled in the Bengal Fan at 8°N during Expedition 354. The site was introduced during the expedition as an alternate site to capture the most recent and Late Pleistocene fan deposition at high resolution. Expedition 354 sites in the eastern and central part of the transect revealed that fan deposition above and below the Toba ash layer (~75 ka) was remarkably low, indicating migration of turbidite channel activity to the west of the 85°East Ridge for probably the last 300 ky. 

International Ocean Discovery Program Expedition 354 to 8°N in the Bay of Bengal drilled a seven-site, 320 km long transect across the Bengal Fan. Three deep-penetration and an additional four shallow holes give a spatial overview of the primarily turbiditic depositional system that comprises the Bengal deep-sea fan. Sediments originate from Himalayan rivers, documenting terrestrial changes of Himalayan erosion and weathering, and are transported through a delta and shelf canyon, supplying turbidity currents loaded with a full spectrum of grain sizes. Mostly following transport channels, sediments deposit on and between levees while depocenters laterally shift over hundreds of kilometers on millennial timescales. During Expedition 354, these deposits were documented in space and time, and the recovered sediments have Himalayan mineralogical and geochemical signatures relevant for reconstructing time series of erosion, weathering, and changes in source regions, as well as impacts on the global carbon cycle. Miocene shifts in terrestrial vegetation, sediment budget, and style of sediment transport were tracked. Expedition 354 has extended the record of early fan deposition by 10 My into the late Oligocene. 

Site U1452 (proposed Site MBF-5A) is in the center of our seven-site transect. It is located in a relatively flat environment with a smooth morphology. Topographic expressions of channels are absent in the vicinity of the site. The seismic profile at this site reveals a prominent, >20 km wide, and up to 40 m thick levee; the top is only at ~5 m below the seafloor. At this site, we focused on coring the upper levee to provide a detailed record of this type of depositional system. Two holes were cored through this levee to allow high-resolution sedimentological, geophysical, geochemical, and micropaleontological investigations. A single mudline core from Hole U1452A was devoted to detailed study of the hemipelagic deposition during the last glacial cycle and to the Toba ash. Hole U1452B was cored to 217.7 m drilling depth below seafloor (DSF) for the study of the Upper Pleistocene section. Finally, Hole U1452C was cored to 41.3 m DSF to provide a more complete record of the levee and to allow more extensive sampling. 

Site U1449 (proposed Site MBF-6A) is part of our seven-site transect designed to document turbiditic transport processes and the architecture of deposition in the Middle Bengal Fan at 8°N since the Pleistocene. Sediments will also be used to trace sources of eroded material in the Himalaya and reconstruct erosion rates as a function of climate change. Site U1449 is located at 08°0.419′N, 088°6.599′E in a water depth of 3653 m. The main Hole U1449A penetrated to 213.5 m drilling depth below seafloor (DSF) and was cored by a combination of the advanced piston corer (APC), half-length APC (HLAPC), and extended core barrel (XCB) systems. Hole U1449B consists of a single APC core from the mudline taken for microbiological studies.