MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Abrupt onset of Patagonian desertification by 11 Myr ago: insights from the fossil record
Autor/es:
PALAZZESI, L; BARREDA, V.D.; GULER, M.V.
Lugar:
Tokio
Reunión:
Congreso; XIII International Palynological Congress; 2012
Resumen:
Abrupt onset of Patagonian desertification by 11 Myr ago: insights from the fossil record Luis PALAZZESI1, Viviana BARREDA1 , Verónica GULER2 1Sección Paleopalinología, División Paleobotánica, Museo Argentino de Ciencias Naturales ?Bernardino Rivadavia?, Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina. CONICET. Email: lpalazzesi@macn.gov.ar 2Departamento de Geología, Universidad Nacional del Sur, San Juan 670 (8000), Bahía Blanca, Argentina. CONICET The southern Andean uplift forced the initial desertification of the eastern Patagonian foreland during the Neogene, giving rise to the largest desert in America. Patagonian landscapes during this changing period have been virtually impossible to reconstruct due to the scarcity of fossil evidence. Here we present the best floristic reconstruction yet attempted during this overwhelming wet-arid transition inferred from fossil pollen grains for the interval 23 to 7 million years ago (Mya). Our results provide constrains of two independent palynological signals by 11 Mya including a 60-fold fossil pollen increase in desert-taxa (joint-pines and amaranths) and an up to 80-fold drop in rainforest-taxa (podocarps and southern beeches). This abrupt and widespread turnover in key climate-sensitive taxa supports the idea that the Andean rain-shadow existed by 11 Ma (Late Miocene) in the eastern Patagonian foreland. We further demonstrate that the dominance of grasses are not only much younger than previously thought, but also challenge the hypothesis that grasslands had a major, direct influence on the diversification of grazing mammals. Floristic turnovers associated with the Andean uplift will assist in elucidating how plants have responded during one of the world?s most important shifts in atmospheric circulation patterns.