Precordilleran Reefs

CAÑAS F. Y CARRERA, M G

Ordovician fossils of Argentina

Secretaria de Ciencia y Tecnología Universidad Nacional de Córdoba

Lugar: Córdoba; Año: 2003; p. 131 - 154

The Ordovician platform carbonates of the Argentine Precordillera host a range of reef types that records organic and paleoecologic evolution of the marine biota, global paleogeographic changes that affected oceanographic and atmospheric conditions, as well as different regional palaeoenvironmental scenarios. The Lower Ordovician represents a period of reorganization of reef communities in which no dominant metazoan constructors prevailed. Since the Middle Ordovician two metazoan groups dominated over reef constructors: stromatoporoids and bryozoans. Benthic microbial communities are always present as reef builders, but seem to be more important in the Lower Ordovician, or more probably they were subsumed within algal-metazoan reefs from the Mid Ordovician onwards (Riding, 2000). From a “Precordillerean” perspective, Early Ordovician reefs are clearly microbialite dominated, and seem to differ only slightly in ecology and constitution from the Early Cambrian microbialite-archeoscyath reefs. In this sense, contribution of reef related biotas to the Ordovician radiation only account for new lithistid sponges, receptaculitids, and some equinoderms inhabit these shallow environments.