Geological context of the dinosauriform-bearing outcrops from the Triassic of Southern Brazil

摘要

The Triassic of the western Gondwana (southern Brazil and northwestern Argentina) records the oldest dinosaurs. The Southern Brazilian Triassic fauna is subdivided into four assemblage zones (AZ's), recorded in alluvial (channel and floodplain) deposits, split into three third-order sequences that comprise the Santa Maria Supersequence. These deposits record dinosauriforms in three of these AZ's, mostly in near-channel environments (channel deposits, crevasse splays, distal floodplains) with different types of preservation (mostly partly articulated, with little carbonate deposition). There is faciological homogeneity within the Dinodontosaurus, Santacruzodon and Hyperodapedon AZ's, whereas change in fluvial style is recorded at the Riograndia AZ. So, further stratigraphic studies must include the recognition of post-depositional tectonism, in order to better understand the autogenic and allogenic mechanisms of deposition. It is suggested here that there is a lateral change on main channel deposition, with the areal restriction of the Santacruzodon AZ probably linked to reactivation on the Passo do Sobrado lineament and modification of the basin floor. (C) 2014 Elsevier Ltd. All rights reserved.