Palinoestratigrafia dos depósitos neógenos da região nordeste de Eirunepé, Bacia do Solimões, Amazonas

Abstract

In two outcrops of the Solimões Formation, in the communities Torre da Lua and Aquidabã, region of Eirunepé, southeast of Amazonas, 35 samples were collected where, through palynological studies and stratigraphic survey, we aimed to provide information on palynomorph groups, contextualize the paleoenvironment and chronostratigraphically position the Solimões Formation in this region. The paleontological content is represented by animal fossils (e.g., molluscs, fragments of a chelonian shell, vertebrate bone fragment and fish scales) and plants (woody fragments and charred leaf impressions). The microfloristic analysis resulted in the identification of 8 species, 1 fungus spore, 5 lycophyte and fern spores and 2 angiosperm pollen grains, respectively: Frasnacritetrus indicus, Cyathidites spp, Deltoidospora adriennis, Echinatisporis muelleri, Ischyosporites dubius, Magnastriatites grandiosus, Echiperiporites estelae and Grimsdalea magnaclavata. The analysis of sedimentary facies resulted in the identification of 6 lithofacies: massive orthoconglomerate (Cm), cross-laminated sandstone (Ac), massive sandstone (Am), massive fossiliferous pelite (Pmf), massive pelite (Pm) and lignite (L). These lithofacies were grouped into 2 facies associations, Lake (AF1) and Crevasse splay (AF2), in an environmental context characterized by clay decantation deposits with preservation of organic matter in which, sporadically, there was an increase in traction, confirmed by the occurrence of sandstone and conglomerate inputs. Palynological data — which, through the occurrence of Grimsdalea magnaclavata, indicate a Neomiocene age for the Solimões Formation deposits — combined with faciological and literature data, as well as paleoenvironmental reconstructions carried out in regions close to this work, allow us to state that the referred unit consists of floodplain deposits formed in a fluvial-lacustrine environment.