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The Camaquã Supergroup constitutes a rift stile se dim ntary basin, located in the central-south region of Rio Grande do Sul state , Brazil, which deposition occured between the Ediacaran and the Eocambrian. In it ́s y ounger unit, the Guaritas Group, composed of fluvial, eolian and aluvial fan deposit s, a new Formation was recently discovered, named Serra do Apertado, which until th en adn ́t detailed studies about facies analyses and architectural elements. The ini tial studies about the Guaritas Group go back to the beginning of the 20th century, after th discovery of copper occurences in that region, but references about sedimentary prove nance of this unit are scarce in the literature. The present study was engaged on applying the faci s and architectural elements analysis methods in the Serra do Apertado and super ior Pedra Pintada Formations, in order to interpret the depositional palaeoenvironme t of those units and establish descriptive distinction criteria to the first one. The method of macroscopic provenance analysis was also applied in conglomeratic deposits of the Guaritas Group, in order to study it ́s compositional variations through time an d space. Was verified that in the Serra do Apertado Formation occurs only one type of architectural element, named EL – sheet floods , which have tabular geometry, thickness varying be twe n 2 and 3 m, lateral continuity of dozens of meters and facies a s ociations that indicates cicles of raising and waning flow, which depositional environ ment was interpreted as efemeral rivers. The superior Pedra Pintada Formation presen ts the elements DB – barcanoid dunes, and IF – fluvial interdunes, that occurs intercalated, both presenting thickne ss of dozens of meters and lateral continuity of hundreds of meters, being interpreted as aeolian dune fields with interdunes. The provenance analysis shown that in the Guaritas Group exists deposits with distal source areas to the north of the basin, that are associated with a fluvial system paralel to the longest basin axis, and deposits wit h more proximal sources mainly to the east, that are associated with transversal fluvial systems and aluvial fans. The comparison of pebble compositional data between the Guaritas Group units shown that, from the base to the top of the succession, the bas in ́s east border transversal fluvial system passes from more distal source areas to more pr ximal, characterizing a downstream diminution on the river ́s catchment area , th t was interpretated as a reactivation of the border fault by the time of the deposition of the Varzinha and Pedra Pintada Formations. Along the stratigrafy of the Se rra do Apertado Formation, the group of quartzose pebbles varies in an inversely p roportional way in relation to the non quartzose pebble group. As it wasn ́t verified a sou rce area distance control in this kind of variation, and as the main factor that comands i t i the pebble ́s composition, it was interpreted that this is due to climatic variations , where more arid climates correspond to

A formação Serra do Apertado (EOCAMBRIANO, RS) e seu contexto tectônico na evolução do rift Guaritas