Oxygen and carbon isotope compositions of middle Cretaceous vertebrates from North Africa and Brazil: Ecological and environmental significance

In order to investigate mid-Cretaceous terrestrial climates of low paleolatitudes, Moroccan, Tunisian and Brazilian vertebrate apatites have been analyzed for their oxygen and carbon isotope compositions of phosphates (delta O-18(p)) and carbonates (delta O-18(c), delta C-18(c)). At each site, coexisting theropod dinosaurs, titanosaurid sauropods, pterosaurs, crocodilians, turtles and fish have distinct delta O-18(p) and delta C-18(c) values reflecting their ecologies, diets and foraging environments. Oxygen isotope compositions of surface waters (delta O-18(w)) estimated from turtle and crocodile delta O-18(p) values range from -5.0 +/- 1.0 parts per thousand to -2.4 +/- 1.0 parts per thousand, which do not differ from mean annual rainwater values occurring today under inter-tropical sub-arid to arid climates. High water temperatures ranging from 21 +/- 6 degrees C to 34 +/- 2 degrees C deduced from fish delta O-18(p) values are in agreement with those published for mid-Cretaceous low latitudes. Temporary or seasonal droughts are inferred from high delta O-18(p) values of lungfish teeth, even though lower reptile delta O-18(p) values suggest the use of distinct and most likely larger or regularly renewed bodies of water. Environmental conditions of the studied low latitude regions during the Aptian-Cenomanian interval were somewhat similar to those experienced today under semi-arid to arid tropical or equatorial climates, but with higher mean surface temperatures than present-day ones. (C) 2010 Elsevier B.V. All rights reserved.