Cronoestratigrafia e interpretação paleoambiental de depósitos miocenos da formação Solimões, Região de Coari, AM

Abstract

The Miocene is one of the periods of Earth characterized by pronounced climatic and bioevolutive changes associates to the expressive marine transgressions. In the South America, these events were concomitant with the progressive uplift of Andes cordillera causing significant paleogeographical and paleoenvironmental modifications. In the center-western region of the Amazônia, the palynologic and stratigraphic studies of Miocene Solimões Formation identified two facies associations, unconformably overlain by Pleistocene siliciclastic deposits of Içá Formation: 1) The Association 1- laminated pelite, characterized by grey pelites with concentration of organic matter, related to an lacustrine environment; and 2) Association 2 sandstone and pelite with heterolithic inclined stratification representative of a meandering fluvial system. The continental inflow is indicated by abundance of phytoclast and fresh water algae (Ovoidites). The Neomiocene age for the Solimoes Formation on the Coari region is indicated by occurrence of Echitricolporites spinosus (Superzone X sensu Muller et al., 1997) and confirmed by the presence of Echiperiporites akanthos, it doesn´t reach the Pliocene epoch. Reworked palynomorphs as Crassoretitriletes vanraadshoovenii and Grimsdalea magnaclavata, forms commonly found in the Mesomiocene, confirm the Neomiocene age and the erosive event during Mesomiocene. Additionally, the concomitant erosion of Paleozoic rocks of western border of Amazonas basin is indicated by abundant Neodevonian acritarchs.