Phytolitic Analysis of the Quequén Grande River

SABATINO MALENA; OSTERRIETH MARGARITA

The Phytolitarien

Society for Phytolith Research

Año: 2005 vol. 17 p. 19 - 19

The Quequén Grande River is one of the autochthonous basins of the South of the Buenos Aires Province, standing out among the surrounding ones for its bigger flow and extension. The basin is particularly interesting because it developed in a plain environment constituted by deposits of different origin from most of the plains in the rest of the world. The aim of this work was to make a quali-quantitative characterization of the silicobioliths in the bottom sediments of the course and to analyze the morphological characteristics of the silicophytoliths to find a link with their possible sources of contribution. The sedimentologic analysis was based on the morphological characteristics of the bed and the type of physiographyc units; the sampling method was the volumetric. The predominant morphologies were the Estrobilolitas and the rectangular phytoliths, which are linked with the pooideae subfamily of grasses. These phytoliths are associated with type C3 grasses of humid conditions, typical of hydromorphic or saturated soils during extensive periods of time, corresponding to the predominant vegetation of the last 8000 years. The silicophytolith degradation, evident in the fragmentation and dissolution of its surface, was observed in the most abundant morphologies in the study area. This bespeaks the alochtone character of these particles, which were worn away and altered by the transport. The point shaped and articulated phytoliths found in the river bars indicate the stability of this environment and the deposit conditions of the sediments, since these morphologies are very fragile and they tend to break easily at the least disturbance of the environment.