ORGANIC-CARBON BURIAL FORCING OF THE CARBON-CYCLE FROM HIMALAYAN EROSION

Weathering and erosion can affect the long-term ocean-atmosphere budge t of carbon dioxide both through the consumption of carbonic acid duri ng silicate weathering and through changes in the weathering and buria l rates of organic carbon(1-4). Recent attention has focused on increa sed silicate weathering of tectonically uplifted areas in the India-As ia collision zone as a possible cause for falling atmospheric CO2 leve ls in the Cenozoic era(5-7) The chemistry of Neogene sediments from th e main locus of sedimentary deposition for Himalayan detritus, the Ben gal Fan, can be used to estimate the sinks of CO2 from silicate weathe ring and from the weathering and burial of organic carbon resulting fr om Himalayan uplift. Here we show that Neogene CO2 consumption from th e net burial of organic carbon during Himalayan sediment deposition wa s 2-3 times that resulting from the weathering of Himalayan silicates. Thus the dominant effect of Neogene Himalayan erosion on the carbon c ycle is an increase in the amount of organic carbon in the sedimentary reservoir, not an increase in silicate weathering fluxes.