ASSINATURAS TAFONÔMICAS DE UM RECIFE ALGÁLICO DE ALTA ENERGIA E BAIXA TURBIDEZ: EXEMPLO DO ÚNICO ATOL DO ATLÂNTICO SUL

Taphonomic reef studies are concentrated in models elaborated for Cenozoic coral reefs. Seeking to elaborate a set of taphonomic signatures applicable to an algal reef, samples from the Rocas Atoll (Equatorial South Atlantic, Brazil) were analyzed. The carbonate facies (Framestone I and II) show small variability allowing for the formation of a taphonomic criteria indicative of algal reefs with insignificant influence of terriginous grains, with low turbidity and high energy. The calcareous algae represent the dominating taphocoenosis bioconstructor. Calcareous encrustations of coralline algae, vermetid gastropods, bryozoans and foraminifers are thick extensively distributed encrustation. The bioerosion of clasts and samples of the paleo-reef are dominated by traces of sponges (Cliona), polychaetes, sipunculids and, in lesser proportion, bivalve mollusks. The high diversity of cementing organisms, presence of aragonitics and calcitic cements and exclusively carbonate sedimentation are important taphonomic signatures. The energy of the waves and, especially, the holocenic eustatic variations were important taphonomic factors generators of the reef growing development. The taphonomic signatures are a potential tool for the recognition and interpretation of algal reef with similar environmental characteristics and for understanding the geobiologic history of the Equatorial South Atlantic Atoll.