Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO₂ uptake by continental weathering and alkalinity river transport to the oceans

Abstract

[1] The silicate rock weathering followed by the formation of carbonate rocks in the ocean, transfers CO 2 from the atmosphere to the lithosphere. This CO 2 uptake plays a major role in the regulation of atmospheric CO 2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks. This leads us to develop the first world lithological map with a grid resolution of 1°Â 1°. This paper analyzes the spatial distribution of the six main rock types by latitude, continents, and ocean drainage basins and for 49 large river basins. Coupling our digital map with the GEM-CO2 model, we have also calculated the amount of atmospheric/soil CO 2 consumed by rock weathering and alkalinity river transport to the ocean. Among all silicate rocks, shales and basalts appear to have a significant influence on the amount of CO 2 uptake by chemical weathering.INDEX TERMS: 1030 Geochemistry: Geochemical cycles (0330); 1060 Geochemistry: Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008); 1645 Global Change: Solid Earth; 1886 Hydrology: Weathering (1625); KEYWORDS: lithological map, global carbon cycle, spatial distribution, river basins, riverine inputs to oceans, modeling Citation: Amiotte Suchet, P., J.-L. Probst, and W. Ludwig, Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO 2 uptake by continental weathering and alkalinity river transport to the oceans, Global

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

“…The proportion of CO 2 consumption by Deccan basalts is a factor of ϳ 4 more than its fractional area of continental drainage. This reinforces the earlier findings (Dessert et al, 2001;Amiotte-Suchet et al, 2003) that Deccan Traps (and basalts in general) are consuming CO 2 disproportionately more than their aerial coverage during their chemical weathering.…”

“…The proportion of various elements in the dissolved phase is a complex function of their relative abundances in minerals and of the mode and rate of their weathering. Chemical weathering of rocks involves consumption of CO 2 , a greenhouse gas that exerts strong influence on climate (Berner et al, 1983;Kump et al, 2000;Amiotte-Suchet et al, 2003;Dessert et al, 2003). Several parameters regulate the rate and intensity of chemical weathering and associated CO 2 consumption.…”

“…These include lithology of the drainage basin, runoff, temperature, vegetation, and relief. In terms of lithology, recent works on basaltic provinces suggest that they weather more rapidly relative to granites and gneisses and that their weathering exerts important control on marine geochemical balances and global change (Meybeck, 1986;Bluth and Kump, 1994;AmiotteSuchet and Probst, 1995;Louvat and Allegre, 1997;Dessert et al, 2001;Amiotte-Suchet et al, 2003;Dessert et al, 2003).…”

Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

“…No simple relationship between cation fluxes and runoff is apparent for granite [53], unless physical erosion rates are high [59]. However, Amiotte-Suchet et al [60] found that weathering rates of pure silicate sandstones and granites were about five times less responsive to runoff than pure silicate shales and basalts. As we are following the same approach assuming that these rocks comprise exclusively silicate minerals, we apply our runoff correction only to basalt and shale.…”

“…We treated all volcanic rocks as basalt; otherwise, we used the rock types of Amiotte-Suchet et al [60]. In a few cases, we altered the geology to match literature data.…”