BIOESTRATIGRAPHY OF SOUTHERN BRAZILIAN MIDDLE-UPPER TRIASSIC

Abstract

The rocks of Middle/Upper Triassic from Southern Brazil (Paraná Basin) can be divided in three major and clearly distinct biostratigraphic units from the basis to the top: 1) Therapsid Cenozone, dominated by Dicynodonts and Cynodonts; 2) Rhynchosauria Cenozone, with an expressive presence of Rhynchosaurs and absence of Dicynodonts and 3) Jachaleria Level, marked by the presence of the Dicynodont Jachaleria. This last one is here proposed as an informal biostratigraphic unit, once that the number of fossils collected until now is low and the occurrence of this fossil assemblage is very restricted. This biostratigraphic framework is very similar to that occurs in Argentinean Triassic. Besides, in both sedimentary sequences it is not observed any evidence of significant hiatus between the different fossil levels, just a change from an anastomosed to a braided fluvial system towards the top of the package.