Mid-Cenozoic vegetación reconstruction based on palynological data from southeastern Santa Cruz province, Argentina

HEREDIA, M. E.; PAEZ, M. M.; GUERSTEIN, G. R.; PARRAS, A.

Bariloche

Congreso; Southern Connection Congress 2010; 2010

The present work is part of a multidisciplinary project including sedimentological data, facies analysis, marine invertebrates and palynology. The aim of this study is to analyze the palynological assemblages recovered from four sections between 49ºS and 50º 30’S. In two of them crops out the Centinela Fm. at Estancia 25 de Mayo (50º30’S, 72º15’W; dated as 22.5 Ma) and La Escondida (51º24’S, 72º09’W) sections, southwestern Santa Cruz. Gran Bajo (49º31’S, 68º14’W; between 25.9 and 25.3 Ma) and Meseta Chica (49º31’S, 68º15’W) sections allow to characterize San Julián Fm. on the Atlantic coast. Here we show the results from both Gran Bajo and Meseta Chica sections. A minimum of 300 palynomorphs were counted in order to achieve, frequency diagrams and cluster analysis. The information from Gran Bajo section indicates that a large humid temperate forest developed towards the end of the Late Oligocene represented by elements belonging to Nothofagaceae and Podocarpaceae, together with an incipient herb – shrub vegetation (e.g. Proteaceae, Anacardiaceae, Caryophyllaceae y Sparganiaceae). An important pteridophytic diversity might have developed as part of the lower layer of the forest. This information is in agreement with a shallow marine environment close to the coast barely influenced by ocean waters. Upwards, in the Meseta Chica section, the elements representing the forest are still dominant though its composition changed as it is shown by the reduction of some arboreal taxa