MICROFACIES MICROBIALÍTICAS y BRIOFÍTICAS PALEOZOICAS DEL BAJO DE VÉLIZ, SAN LUIS, ARGENTINA.

Abstract

Three tufa stromatolite (TS) banks have been found in the siliciclastic pelitic sequence of the Véliz palaeolake, identified within the Eopermian Bajo de Véliz Formation, San Luis Province, Argentina. The TS are laminated stratified structures 2m long and 0.20m thick, made up by domes with association of three microfacies. MFB is characterized by a framework of plant origin, identified as bryophytes due to their similarity to such Upper Permian genera as Uskatia, Polyssaievia and Bajdaievia described by Neubourg in 1960 for Russian basins; MFL is composed of laminae of microbia!ithic origin, replaced by neomorphic sparite, interlayered with detrita! silt and clay-size grains; and MFM is constituted by mammillate and globose forms of microbial origin. The three calcareous banks, formed in an organic rich silicilastic lacustrine environment, are proposed to be due to the activity of carbonated springs during periods of low detrital supply.