The early Paleozoic carbon cycle

• Published in: Earth and planetary science letters Vol. 190; no. 3; pp. 181 - 196
• Main Authors: Goddéris, Yves, François, Louis M., Veizer, Ján
• Format: Journal Article Web Resource
• Language: English
• Published: Elsevier B.V 2001; Elsevier Science Bv
• Subjects: carbon cycle; Earth sciences & physical geography; isotope ratios; lower Paleozoic; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Sciences de la terre & géographie physique; sea water; sea water; models; carbon cycle; isotope ratios; lower Paleozoic
• ISSN: 0012-821X; 1385-013X; 1385-013X
• DOI: 10.1016/S0012-821X(01)00377-6

A review of O, C, Sr and S isotope trends for the entire Phanerozoic shows that the present-day values of isotope signals are similar to those at the Proterozoic termination. The sharp rise in 87Sr/ 86Sr since ∼65 Ma has been attributed to an uplift and subsequent metamorphism and erosion associated with the Himalayas and Tibet. This orogenic evolution has been postulated to have influenced the global organic and inorganic carbon cycles and climate as well. A similar large-scale orogeny, the Pan-African event, also dominated the Neoproterozoic (Vendian) times, and the similarity of modern and Neoproterozoic isotope values for seawater may therefore have had a comparable tectonic cause. In this contribution, we present the results of a numerical model of the coupled C–alkalinity–S–Sr cycles suggesting that the early Paleozoic (from early Cambrian to late Devonian) evolution of Sr, O, C and S seawater isotope signals could have been the consequence of progressive oxidation of a large reduced carbon reservoir exhumed during the Pan-African orogeny. The δ 18O measured in brachiopod shells is used as a forcing of the model, postulating that any change in the oxygen isotopic composition of seawater is the result of a disequilibrium in the organic carbon subcycle through the coupling of the oxygen isotopic and carbon cycles. The calculated δ 13C, 87Sr/ 86Sr and δ 34S are in good agreement with the data, as is the reasonable calculated history for atmospheric pCO 2 and its relation to global climate.