CONICET | Buscador de Institutos y Recursos Humanos

In the coastal region of Santa Cruz province (Argentina) the late Early Miocene sediments of the Santa Cruz Formation are deposited on top of the underlying marine Monte León Formation and overlain by polylithic gravels of Andean origins that are regionally extensive, known as ?Patagonian gravels.? In past studies we explored microremains through this sedimentary sequence south of Coyle River. Here, we present the first results of phytolith analysis in the fossil locality Rincón del Buque (RDB) located north of Coyle River. The samples were taken in three profiles with an equidistance of 5,7 and 8,5 km (RDBSouth, RDBCentral and RDBNorth) that show a gradual upwards transition from estuarine to fluvial depositional environments. In this framework 23 samples selected according to the sedimentary characteristics were studied. The samples contained a variety of microremains, including diatoms, radiolarians, freshwater sponge, stomatocysts, microcharcoals and sporomorphs, aside from phytoliths. Phytolith assemblages exhibit a granulometric trend with greater abundance of small phytoliths (diagnostic) in estuarine levels, while large phytoliths are more abundant in fluvial sediments. Phytolith are principally unicellular elements, mostly of graminoid affinity, but with variations in the content of cyperoid, arecoid and dicot phytoliths at different levels of the profiles. Among the grasses, pooids (mainly festucoids) are most abundant, but phytoliths of PACMAD grasses such as danthonioids, panicoids and chloridoids are also present but less abundant. Specifically, phytoliths of the warm-adapted PACMADs are present in many cases linked with levels with vertebrate fossils of Santacrucian Age.