T32E-03
PLEISTOCENE THROUGH OLIGOCENE RECORD OF HIMALAYAN OROGENY AND CLIMATE. THE IODP EXPEDITION 354 DRILLING TRANSECT ACROSS THE MIDDLE BENGAL FAN AT 8°N

Wednesday, 16 December 2015: 11:50
104 (Moscone South)
Volkhard Spiess1, Christian France-Lanord2, Tilmann Schwenk1, Adam Klaus3 and IODP Expedition 354 Scientific Party, (1)University of Bremen, Bremen, Germany, (2)Organization Not Listed, Washington, DC, United States, (3)Texas A & M University College Station, College Station, TX, United States
Abstract:
IODP Expedition 354 in the Bay of Bengal February-March 2015 drilled a seven site, 320 km-long transect across the Bengal Fan at 8°N. Three deep penetration and additional four shallow holes provided a spatial overview of the primarily turbiditic depositional system, comprising the Bengal deep sea fan. Sediments originate from Himalayan rivers, documenting terrestrial changes of the monsoon evolution and 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 are laterally shifting over hundreds of kilometers on millennial time scales.

Expedition 354 documented these deposits in space and time by identifying, coring and dating numerous stratigraphic marker horizons across the transect, allowing a detailed reconstruction of channel-levee migration, abandonment, reoccupation and overall uniform growth in the late Pleistocene. High resolution records of these growth patterns were acquired in several levee, interlevee and hemipelagic successions.

Miocene through Pliocene fan development was studied at three deeper sites, which document and recovered sand rich facies throughout most of the cores acquired by the half-APC coring technology, intercalated by longer periods of hemipelagic deposition and absence of turbiditic input as the results of major depocenter shifts.

Recovered sediments have Himalayan mineralogical and geochemical signatures suitable to reconstruct time series of erosion, weathering and changes in source regions as well as impacts on the global carbon cycle. Miocene shifts in terrestrial vegetation, in sediment budget and in style of sediment transport have been tracked. Expedition 354 has extended the record of early fan deposition by 10 Ma into the Late Oligocene.

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