CCT SAN LUIS   20913
CENTRO CIENTIFICO TECNOLOGICO CONICET - SAN LUIS
Centro Científico Tecnológico - CCT
congresos y reuniones científicas
Título:
Bajo de Véliz stromatolites revisited
Autor/es:
BENAVENTE, C.A., A.C. MANCUSO, N.G. CABALERI, E.M. CRESPO
Lugar:
Puerto Madryn (Chubut)
Reunión:
Otro; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018
Institución organizadora:
Instituto Patagónico de Geología y Paleontología (IPGP, CCT CONICET-CENPAT)
Resumen:
The discussion about the true biogenicity of Ca-rich deposits has been extensive, and in the past, abiogenic structures have been referred to stromatolites when their origin was linked to inorganic precipitation of carbonate. Later on, different types of carbonate precipitation have been described including: mineralization (inorganic); and biogenic precipitation of carbonates, namely: biologically controlled, biologically induced and biologically influenced mineralization. The Bajo de Vélizsubbasin, located on the east margin of the Paganzo Basin, in the NE of San Luis province, presentsthe Bajo de Véliz Formation,referred to as Permian. The unit is a siliciclastic succession, well known by its extraordinary fossiliferous content and includes carbonate levels.The carbonates have been previously described as stromatolites based on microfacies analysis with the identification of bryophyte and cyanobacteria as producers. Nevertheless, new polished sections and thin section microfacies analysis under low magnification binocular microscope along with SEM - EDS analysisshows no trace of biogenicity at a microstructure level.New data shows that the microfabric is formed by a combination of Ca-rich parallel and subparallel veins (spar), included in a Si-rich matrix with Fe content. These microstructures were previously identified as bryophyte remains but no feature other than morphological resemblance was found. Thispoints to a genesis linked to a probable carbonate rich seep that caused Ca and Si mineralizationin the form of complex dendrites. Further cathodoluminescence analysis can confirm the timing and different phases of mineralization and if there was incremental growth