NEOTROPICAL CLIMATE AND ENVIRONMENT FROM STABLE ISOTOPES IN MAMMALIAN AND FISH TOOTH ENAMEL FROM THE EARLY MIOCENE THROUGH THE PLIOCENE

Quantitative reconstructions of terrestrial paleoclimate and environment for the tropics are notoriously scarce. However, these data are crucial for applications as diverse as paleoecological reconstruction and testing of climate models. The combined effects of Andean uplift, closure of the Central American Seaway, and global trends on Neotropical climate and environment during the Neogene remain uncertain. However, environmental conditions provide critical context for understanding biological evolution and events such as the Great American Biotic Interchange.

We have undertaken a stable isotope analysis of fossil tooth enamel and pedogenic carbonate concretions to assess paleoclimate and terrestrial ecosystem structures in northern South America during the Miocene and Pliocene. The analyses presented here utilize material from the Castilletes Formation (early Miocene) and Honda Group (Middle Miocene) of Colombia and the Urumaco (Late Miocene) and San Gregorio (Pliocene) Formations of Venezuela. In particular, we have measured (a) the phosphate oxygen and carbonate carbon and oxygen isotope compositions of mammalian teeth, (b) the carbon and oxygen isotope compositions of pedogenic carbonate concretions, and (c) the phosphate oxygen isotope composition in fish teeth.

Our studies have ensured that the fossil enamel preserves original isotopic signals as well as conducting investigations into paleotemperature, seasonality, and ecosystem structure. The fauna selected for this study allow an assessment of change in each of these variables over space and time. Furthermore, we compare the results for each time interval with existing climate estimates from synchronous mid latitude localities. Ultimately, these low latitude data help to constrain models of both physical environment and biological evolution throughout the Neogene.