Navegando por Assunto "Palinomorfos"

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Acesso aberto (Open Access)
Foraminifera, thecamoebians and palynomorphs as hydrodynamic indicators in Araguari Estuary, Amazonian Coast, Amapá State - Brazil
(2010-12) LAUT, Lazaro Luiz Mattos; FERREIRA, Daniele Esteves da Silva; SANTOS, Valdenira Ferreira dos; FIGUEIREDO JÚNIOR, Alberto Garcia de; CARVALHO, Marcelo de Araújo; MACHADO, Odete Fátima
The Araguari estuarine dynamics is singular among traditional models of estuaries under tidal regime due to influence of macrotidal and tidal bore. In order to establish estuarine zones in Araguari according foraminifera, thecamoebians, paliynomorphs and physical-chemistry parameters, sixteen sample stations were established along the estuary. Turbidity and temperature were the environmental parameters which allowed determination of the estuarine gradient. Eighteen species of foraminifera, ten of thecamoebians and fourteen of particulate organic matter types were identified. Cluster analysis in R-mode showed three microorganism assemblages and four palynomorph ones. The CCA analyze shows turbidity and total organic matter with the most influence over foraminiferal and thecamoebians distribution at Araguari. Clustering analysis in Q-mode using all data formed four groups suggesting three estuarine zones in Araguari: Zone I composed of thecamoebian species and continental palynomorphs; Zone II - composed by mangrove foraminifera, thecamoebians and all palynomorph assemblages; and Zone III - composed by mangrove and estuarine foraminifera and all palynomorph assemblages.
Acesso aberto (Open Access)
O Neógeno e Pleistoceno da Amazônia Central: Palinoestratigrafia, Paleoambiente e relação com os eventos evolutivos do Rio Amazonas
(Universidade Federal do Pará, 2021-03-19) LIMA JÚNIOR, Walmir de Jesus Sousa; JARAMILLO, Carlos Alberto; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Outcrop-based facies analysis of 25 m-thick Neogene succession was carried out in the Eastern Solimões Basin, Central Amazonia. The Miocene Solimões Formation includes lake/overbank, suspended-load meandering fluvial channel with subdelta crevasse, and flood plain/crevasse splay deposits, confirming the previously interpreted Pebas-Solimões megawetland system. The Upper Pleistocene Içá Formation unconformably overlies the Solimões Formation and comprises mixed load to bedload meandering fluvial channel and floodplain deposits. The Solimões Formation's palynostratigraphy was carried in this exposed succession and a drill core (196-291 m), generally in organic matter-rich mudrock. The occurrence of exclusively continental fossils associated with phytoclasts and freshwater algae such as Ovoidites confirm the wetland setting restricted to Western Amazonia. Monoporopollenites annuulatus and other grasses indicate an oscillation between shrub and tree phases linked to dry and humid interval fluctuations. The upper Miocene-Pliocene ages for the Solimões Formation obtained since amplitudes zones identified mainly Crassoretitriletes vanraadshovenii, Echiperiporites akanthos, Echiperiporites stelae, Fenestrites spinosus, Psilastephanoporites tesseroporus, Grimsdalea magnaclavata, and Alnipollenites verus. The first appearance of Alnipollenites verus is modified for the Miocene. Reworked palynomorphs found in this succession indicate autocyclic processes related to the environmental dynamic, while acritarchs indicate erosion of Paleozoic source areas. The Andean tectonics affected Central Amazonia dramatically, causing the progressive uplift of the Solimões Basin and the emergence and demise of the Pebas-Solimões mega-wetland succession. This progradation event was amplified by the expressive sea-level fall in the middle-Tortonian (11-8 Ma), resulting in the Andean Amazon River's onset. The generated unconformity resulted in a gap and bypass sediment of ~ 9,5 Ma. Only in the Late Pleistocene, the Solimões Basin subsided, causing the implantation of a mixed- to bedload meandering system that represents the sedimentation restart of the Amazon River in the Central Amazonia.