2020-01-282020-01-282015-06-23MENDES, Anderson Conceição. Fácies e proveniência de depósitos siliciclásticos cretáceos e neógenos da bacia do Amazonas: implicações para a história evolutiva do proto-amazonas. Orientador: Afonso César Rodrigues Nogueira. 2015. 113 f. Tese (Doutorado em Geologia e Geoquímica) – Instituto de Geociências, Universidade Federal do Pará, Belém, 2015. Disponível em: http://repositorio.ufpa.br:8080/jspui/handle/2011/12240. Acesso em: .https://repositorio.ufpa.br/handle/2011/12240Siliciclastic deposits exposed near the channel of the modern Amazon River and overlaid by Neogene units have been attributed to the Cretaceous, formally named as Alter do Chão Formation. Integrated studies based on sedimentology, stratigraphy, trace fossils, petrography of sandstones and heavy minerals, as well as, U-Pb dating of zircon grains allowed reconstitute the depositional paleoenvironment and infer the probable source areas of these Cretaceous deposits in the Amazon Basin. Despite its wide geographical distribution throughout the Amazonas Basin, stratigraphic and sedimentological studies of Alter do Chão Formation were located in areas where there was not allowed a better paleoenvironmental and paleogeographic reconstruction. These deposits record the evolution of a large-scale fluvial system or “Big River”, with meandering pattern in the central-eastern Amazonas Basin, while in the western portion of the basin, predominate an anastomosed configuration with large overbank zones colonized by animals and plants. The recorded of this biologic activity are traces fossil of Taenidium, Planolites, Diplocraterion, Beaconites, Thalassinoides, adhesive meniscate burrows and excavations of insects and vertebrates, as well as, root marks. The fluvial succession consists of kaolinitized and locally silicified conglomerates, sandstones and pelites, grouped in eight architectural elements, Gravel Bar, Sand edforms, Lateral Accretion Bar, Levee, Channels, Crevasse Splay Lobes, Abandoned Channel Fills and Overbank Fines. The expressive terrigenous supply probably came of uplifted areas related to Gurupá Arch, eastern limit of the basin, and zircon grains ages range from 1.8 to 2.9 Ga, indicate the Maroni-Itacaiúnas and Central Amazon provinces as main cratonic sources of sediments. The massive sediment input reflected in the hundreds of meters thick of cretaceous deposits, extense for thousands of kilometres, suggests expressives drainages from the craton, feeding an approximate E-W-oriented "Big River”. Probably, the Late Cretaceous paleogegraphy will be similar to current configuration of the modern Amazon River, but with opposite migration, directioned to the Pacific Ocean. The unconformity between Alter do Chão Formation and Neogene deposits attests long period of subarial exposure in the Amazon Basin during the Paleogene, coincident with the development of lateritic-bauxitic profiles. Paleocurrent measures confirms the flow reversion to the east, in direction of Atlantic, during the Neogene. Additionally, the spectrum of zircon grains ages, ranging from 0.5 to 2.7 Ga, comparable to obtained for Quaternary deposits, indicates cratonic and mainly Andean sources, recording the beginning of the Amazon River. The results obtained here allowed, by first time, to propose a transcontinental drainage model for the Late Cretaceous, as weel as, to record the initial sedimentation of proto-Amazon river during the Neogene.Acesso AbertoGeologia estratigráficaSedimentação e depósitosFácies (Geologia)Bacia do AmazonasTeseCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASGEOLOGIA SEDIMENTAR E ESTRATIGRÁFICAGEOLOGIA