EP21E-05
IODP Expedition 354: A Bengal fan record of Himalayan erosion, weathering and organic carbon burial during the Neogene.

Tuesday, 15 December 2015: 09:00
2003 (Moscone West)
Christian France-Lanord, CRPG-CNRS-Univ. Lorraine, Vandoeuvre les Nancy, France, Volkhard Spiess, University of Bremen, Bremen, Germany, Adam Klaus, Texas A & M University College Station, College Station, TX, United States, Albert Galy, CRPG Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre-Les-Nancy, France, Valier Galy, Woods Hole Oceanographic Institution, Marine Chemistry & Geochemistry, Woods Hole, MA, United States and IODP Expedition 354 Science party
Abstract:
The development of the Himalayan orogen induced a major change in continental distribution, topography and climate that impacted the global biogeochemical cycles. The development of the highest mountain range coupled to the intense monsoonal precipitation regime generated an intense erosional flux that enhanced both organic carbon burial and silicate weathering. The largest part of the sediment flux was exported to the Bengal Fan, accumulating a long-term archive of this erosion. These sediments record the nature of eroded formations in the Himalaya and allow the documentation of weathering as well as organic carbon fluxes.

In February-March 2015, IODP Expedition 354 drilled an E-W transect in the middle fan at 8°N to investigate interactions between the growth of the Himalaya, the development of the Indian monsoon, and processes affecting the carbon cycle. This expedition obtained a comprehensive record of turbiditic deposition since the Late Oligocene. Shipboard results reveal that the chemical and mineralogical compositions of turbiditic sediments cored across the transect are relatively stable throughout the Neogene. They reveal a weak regime of chemical weathering with no significant variation through time. This differs from the distal fan record (Leg 116) where from ~7 to 1 Ma, weathered and smectite rich sediments dominated. This difference implies that the distal fan record is not related to a direct evolution of the erosion regime but rather is controlled by a change in sediment transport within the fan. Shipboard estimates of organic carbon loading and behavior resemble observations made in the modern Ganga-Brahmaputra river sediments, suggesting efficient terrestrial organic carbon burial in the Bengal Fan [1]. Preliminary observations support the idea that Himalayan erosion has consumed atmospheric CO2 through the burial of organic carbon, more than by silicate weathering.

[1] http://dx.doi.org/10.1038/nature06273

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