Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO 2 uptake by continental weathering and alkalinity river transport to the oceans Philippe Amiotte Suchet Microbiologie et Ge ´ochimie des Sols, UMR-INRA/Universite ´ de Bourgogne, Centre des Sciences de la Terre, Dijon, France Jean-Luc Probst Laboratoire des Me ´canismes de Tranfert en Ge ´ologie, UMR-CNRS/Universite ´ Paul Sabatier, Toulouse, France Wolfgang Ludwig Centre de Formation et de Recherche sur l’Environnement Marin, Universite ´ de Perpignan, Perpignan, France [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°  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. KEYWORDS: lithological map, global carbon cycle, spatial distribution, river basins, riverine inputs to oceans, modeling 1. Introduction [2] The significance of rock weathering in the global carbon cycle has already been discussed by many authors, such as Berner et al. [1983], Meybeck [1987], Amiotte Suchet and Probst [1993a, 1993b, 1995], Ludwig et al. [1998, 1999], Gaillardet et al. [1999]. Recently, it has been demonstrated that the riverine inputs of carbon to the ocean have to be taken into account in the regional distribution of sources and sinks of CO 2 in the ocean [Aumont et al., 2001]. The chemical and physical erosion of land materials releases into rivers carbon which is subsequently discharged into the oceans (dissolved organic (DOC) and inorganic (DIC) carbon and particulate organic (POC) and inorganic (PIC) carbon). The present-day riverine flux of carbon is esti- mated to be about 1 Gt C yr 1 (0.8 to 1.2 according to literature estimates); DIC, PIC, DOC and POC fluxes represent, respectively, 38%, 17%, 25% and 20% of the overall carbon flux. Most of the carbon transported by the rivers originates from atmospheric CO 2 , except PIC and half of the DIC which are supplied by the physical and chemical erosion of carbonates. [3] The chemical erosion of inorganic materials consists in dissolving or hydrolyzing primary minerals of rocks and soils. The chemical reactions require CO 2 and release DIC, as can be seen, for example, in the equation for albite hydrolysis, 2NaAlSi 3 O 8 þ 2CO 2 þ 11H 2 O ! Al 2 Si 2 O 5 OH ð Þ 4 þ 2HCO  3 þ 2Na þ þ 4H 4 SiO 4 ; ð1Þ or in the equation for the calcite dissolution, CaCO 3 þ CO 2 þ H 2 O ! Ca 2þ þ 2HCO  3 : ð2Þ [4] In river water, bicarbonates can be assumed to be equal to the alkalinity. All bicarbonate flux released by silicate hydrolysis (equation (1)) originates from the atmos- pheric CO 2 , while it is only half for carbonate dissolution