Plataformas dominadas por ondas com ação de tempestade – estudo de caso: a Formação Três Marias, Grupo Bambuí, Bacia do São Francisco, Minas Gerais, Brasil

Abstract

In some oceans, the coastline has hydraulic parameters associated with storm waves, generating flows that produce characteristic sedimentary facies called tempestites. The Três Marias Formation, Bambuí Group, is the youngest unit of an Ediacaran-Cambrian foreland basin, in which transitional/costal facies have been previously described, but the published studies on its sedimentological and stratigraphic record have a low level of detail. The aim of this study was to better understand the paleoenvironmental evolution of the basin at its final stage through detailed stratigraphic surveys. The ten facies defined were arranged into five facies’ associations, named according to the subenvironment on a coastal platform. The stratigraphy of the Três Marias Formation in its type area is represented mainly by sandstones deposited from the beach to the lower shoreface on a shallow platform, influenced by storm waves. High- to medium-frequency cycles are represented by rocks marking maximum regressions and transgressions. The upper interval of the survey suggests strong regression by showing deltaic plain deposits. This study contributes to the discussion on the evolution of the Bambuí basin at the Cambrian, a topic that deserves attention, considering the various ecological, tectonic and climatic transitions experienced by the Earth during this time.