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| Erosion of Deccan Traps determined by river geochemistry: impact on the global climate and the 87Sr/86Sr ratio of seawater Dessert, C.; Dupre, B.; François, L.M.; Schott, J.; Gaillardet, J.; Chakrapani, G.; Bajpai, S. (2001). Erosion of Deccan Traps determined by river geochemistry: impact on the global climate and the 87Sr/86Sr ratio of seawater. Earth Planet. Sci. Lett. 188(3-4): 459-474. dx.doi.org/10.1016/S0012-821X(01)00317-X
In: Earth and Planetary Science Letters. Elsevier: Amsterdam. ISSN 0012-821X; e-ISSN 1385-013X, meer
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| Abstract |
f = R-f x C(0)exp[-Ea/R(1/T-1/298)] where f is the specific CO2 consumption rate (mol/km2/yr), R-f is runoff (mm/yr), C-0 is a constant (= 1764 mu mol/l), Ea represents an apparent activation energy for basalt weathering (with a value of 42.3 kJ/mol determined in the present study), R is the gas constant and T is the absolute temperature (K-o). Modelling results show that emplacement and weathering of Deccan Traps basalts played an important role in the geochemical cycles of carbon and strontium. In particular, the traps led to a change in weathering rate of both carbonates and silicates, in carbonate deposition on seafloor, in Sr isotopic composition of the riverine flux and hence a change in marine Sr isotopic composition. As a result, Deccan Traps emplacement was responsible for a strong increase of atmospheric pCO2 by 1050 ppmv followed by a new steady-state pCO2 lower than that in pre-Deccan times by 57 ppmv, implying that pre-industrial atmospheric pCO2 would have been 20% higher in the absence of Deccan basalts. pCO2 evolution was accompanied by a rapid warming of 4°C, followed after 1 Myr by a global cooling of 0.55°C. During the warming phase, continental silicate weathering is increased globally. Since weathering of continental silicate rocks provides radiogenic Sr to the ocean, the model predicts a peak in the 87Sr/86Sr ratio of seawater following the Deccan Traps emplacement. The amplitude and duration of this spike in the Sr isotopic signal are comparable to those observed at the Cretaceous-Tertiary boundary. The results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on Earth. |
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