Evolução estratigráfica e paleogeográfica do grupo Santa Bárbara (Ediacarano) na Sub-Bacia Camaquã Central, RS

Abstract

In the Central Camaquã Sub-basin, the Santa Bárbara Group (Ediacaran) is over 2,000 m thick, being well exposed in the Minas do Camaquã and Bom Jardim regions. The group is represented by a sucession of marine to coastal sandstones and rhythmites, and alluvial fan conglomerates, disposed in progradational-retrogrational cycles. Detailed stratigraphic studies of paleoenvironments, paleocurrents and provenance have lead to the subdivision of the Group in the central sub-basin into four formations: 1. Passo da Capela Formation: silty-sandy unit composed of outer- and inner- subaqueous fan turbidites and offshore tempestites; 2. Seival Formation: sandstones of coastal deposits, including tidal flat sistems; 3. Rincão dos Mouras Formation: alluvial fan and braided alluvial pebbly unit and 4. João Dias Formation: mainly sandstones interpreted as foreshore and shoreface coastal deposits. These studies have permitted the detailed correlation between the Minas do Camaquã and Bom Jardim regions, thus supporting the proposition of including in the Santa Bárbara Group as defined here, the deposits exposed in the Minas do Camaquã region, traditionally attributed to the Arroio dos Nobres Formation.