Carbon isotope record of Late Cambrian to Early Ordovician carbonates of the Argentine Precordillera

A more than 2000-m-thick Cambrian-Ordovician carbonate platform succession developed on the exotic Argentine Precordillera terrane during rifting from Laurentia and drifting towards Gondwana. On base of these carbonates, a carbon isotope curve could be developed for the Cambrian-Ordovician. We measured delta(13)C(carb) and delta(13)C(org) values on bulk rocks, selected components and diagenetic cements. Whereas the carbon isotope signals of intertidal and supratidal rocks are altered by diagenesis, most subtidal carbonates exhibit primary marine values. We can report reliable curves for the Middle-Late Cambrian transition and for the latest Cambrian to earliest Middle Ordovician. The delta(13)C curve matches well with the published data from global Cambrian-Ordovician boundary sections. Excursions and shifts in the carbon isotope curve correspond to events in sequence stratigraphy. This indicates the interdependence on sea level which rules the productivity and/or preservation of organic carbon and therefore the partition between C-org and C-carb burial. (C) 2003 Elsevier Science B.V. All rights reserved.