Gran Barranca : Evolution and Environmental Change through the Middle Cenozoic of Patagonia

The turn of the twentieth century began an intense period of paleontological exploration of Patagonia. The field work of Carlos Ameghino in Patagonia, including Gran Barranca, documented in correspondence with his brother Florentino, was central to the discovery of the biostratigraphic sequence of pre-Santacrucian mammalian faunas. The work of the Ameghinos was stimulated by rivalry and benefitted from substantive contributions from contemporaries, notably Andrés Tournouër. The early field study at Gran Barranca was sustained during the early twentieth century by geologists working in mineral and petroleum exploration in Patagonia, including a noteworthy contribution by Egidio Feruglio. The contributions of paleontologists working for museums of natural history in the United States, Elmer Riggs, Bryan Patterson, and George Simpson, represent another midcentury phase of activity at Gran Barranca. This work yielded exquisite specimens and set a new standard of utility for documentation and stratigraphic resolution. The Second World War and immediate post-war period also saw collecting activity at Gran Barranca by paleontologists associated with Argentine museums, Alejandro Bordas, Alfredo Castellanos, and Galileo Scaglia, work that continued to yield novelty from the exposure. Rejuvenated by contemporary revolutions in tectonics and geochronology, Rosendo Pascual and his many students and collaborators at the National University and Museum of La Plata initiated multidisciplinary work at Gran Barranca, two noteworthy components of which were the stratigraphy and sedimentology of Luis Spalletti and Mario M. Mazzoni and the geochronology mediated by Larry G. Marshall of the abundant basalts of central Patagonia and Gran Barranca. This work enabled the first refined interpretations of the Patagonian fossil record in light of broader scientific questions about middle Cenozoic earth history. Continuing this tradition, scientists from the Facultad de Ciencias Naturales yMuseo de La Plata, DukeUniversity, the Museo Argentino de Ciencias Naturales, and the Universidad de Buenos Aires, and numerous other institutions, using technical advances in radioisotopic dating and magnetostratigraphy and an intensification and diversification of collecting effort, bring much that is new to an increasingly sophisticated understanding of faunal and floral response to environmental change through the middle Cenozoic.