Organic carbon burial forcing of the carbon cycle from Himalayan erosion

Weathering and erosion can affect the long-term ocean–atmosphere budget of carbon dioxide both through the consumption of carbonic acid during silicate weathering and through changes in the weathering and burial rates of organic carbon1,2,3,4. Recent attention has focused on increased silicate weathering of tectonically uplifted areas in the India–Asia collision zone as a possible cause for falling atmospheric CO2 levels in the Cenozoic era5,6,7. The chemistry of Neogene sediments from the main locus of sedimentary deposition for Himalayan detritus, the Bengal Fan, can be used to estimate the sinks of CO2 from silicate weathering and from the weathering and burial of organic carbon resulting from Himalayan uplift. Here we show that Neogene CO2 consumption from the net burial of organic carbon during Himalayan sediment deposition was 2–3 times that resulting from the weathering of Himalayan silicates. Thus the dominant effect of Neogene Himalayan erosion on the carbon cycle is an increase in the amount of organic carbon in the sedimentary reservoir, not an increase in silicate weathering fluxes.