Climate-tectonic control on the structure and built-up of the Bengal Shelf: Processing and evaluation of high-resolution multichannel seismic profiles for an IODP-Proposal

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The Ganges-Brahmaputra rivers transport the worldwide largest sediment freight from the Himalayas to the Bay of Bengal. This source-to-sink system is driven by climatic-tectonic links, i.e. the monsoon and the uplift of the Himalayas. Consequently the sedimentary depocenters of the Ganges-Brahmaputra rivers contain a record of the interaction of climate and tectonic processes. The long-term Neogene history of the system can be studied in the deep-sea fan and the corresponding IODP proposal 552 (France-Lanord, Spieß et al.) was positively evaluated and is ready for drilling. The shortterm Pleistocene history of the system, however, is recorded in the rapidly accumulating shelf sediments. The tectonic subsidence of the shelf, caused by the collision with the overriding Indo-Burmese plate, constantly adds new accommodation space for the high terrigenous flux delivered from the Himalayas by the monsoonal precipitation. Drilling at the shelf of Bangladesh by a Mission Specific Platform or the new JOIDES Resolution will contribute to understand: The Pleistocene climatic variability of the Indian monsoon system by studying the provenance of detrital material and determining salinity changes, The Pleistocene sea level changes by seismic stratigraphy, dating of oolithic beaches ridges and low-stand deposits at the shelf edge, An estimation of the Pleistocene subsidence of the area, The Holocene monsoonal changes including the frequency of tropical cyclones with an ultra-high resolution record in the shelf canyon (~ 1 km Holocene sediments) by analysing marine and terrestrial biomarkers, and The effects of deforestation and intensification of agriculture in the Indian-Himalaya region by analysing the geochemistry of canyon sediments. This proposal aims to process the high-resolution multichannel data recorded on the shelf and upper slope during the 2006 SONNE cruise SO188. In combination with the data of SO93/SO126 profiles and the samples of outcropping units, the structural framework of the outer shelf and upper slope is analysed by using seismic stratigraphic methods. Based on this evaluation an IODP drilling proposals with sites in the shelf canyon, outer shelf and upper slope for the Holocene and Pleistocene history are developed.