PALEOGEOGRAFIA Y PALEOAMBIENTES DE LA FORMACION VILLA MONICA, PRECAMBRICO, SIERRA LA JUANITA, TANDILIA, ARGENTINA

MANASSERO, MARCELO, ZALBA, P Y MOROSI, M.

Mar del Plata

Jornada; 6 tas Jornadas Geológicas y Geofísicas Bonaerenses; 2007

Universidad mar Del Plata-CIC

ABSTRACT A Complex association of peritidal carbonatic and siliciclastic, facies have been found, in the The Villa Mónica Formation (Neoproterozoic), overlying the Cuarcitas Inferiores, at the Estancia La Siempre Verde, La Placeres and Don Camilo quarries, Sierra La Juanita. The calcareous facies comprise well-preserved head stromatolites (subtidal) with “in situ” grown random aggregates of pyramidal quartz megacrystals filling fenestral cavities.and also strongly weathered algal-siliciclastic boundstones with siliciclastic intercalations (intertidal) which have been dolomitized, illitized or silicified. The algal-siliciclastic-heterolithic facies are composed of major detrital illitic claystones or mudstones and quartzitic sandstones. The paleoenvironmental conditions have evolved from a shallow progradating carbonate platform, with periodical oscillations of the sea level to tidal influenced littoral conditions. The coastal line was probably NE-SW and the deeper facies were located to the west. Field work and microtextural studies reveal a complex story of weathering and diagenesis   Key words: peritidal head and algal boundstones Precambrian carbonate platform, heterolithic facies .