Integrated correlation of the Camaquã Basin (Southernmost Brazil) with other Ediacaran units of southwestern Proto-Gondwana

Abstract

Ediacaran organic-walled microfossils (OWM) were recently reported for the Camaquã Basin. Sphaeromorphic acritarchs, such as Leiosphaeridia sp, Lophosphaeridium sp. and Germinosphaera, as well as one kind of ornamented microfossil (Tanarium irregulare) were extracted from rocks of either marine (Maricá Group) or continental (Bom Jardim, Santa Bárbara groups) depositional systems. The stratigraphic distribution of organic-walled microfossils within well age-constrained siliciclastic successions made it possible to correlate these microfossils with other coeval Ediacaran assemblages in the world, especially in southwestern Proto-Gondwana. This comparison has shown similarities and differences among them. The Camaquã Basin microfossils register a more extended time interval, but present a smaller diversification than the other assemblages, probably due to have lived within more stressing environments. These differences led us to create a new microfossil assemblage, the CAMBAP (Camaquã Basin Palynoflora) Assemblage, which represents an ecozone, with cosmopolitan microfossils living closely associated with microbial mats.