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ABSTRACT
Amazonia covers nearly 50% of Brazil. The history of this biome is marked by many changes in the landscape caused mainly by the Central and Northern Andes uplift. This event has influenced the palaeogeography of the Amazon and therefore its biogeography and possibly biodiversity. Herein we present palynological and lithostratigraphical results from the Solimões Formation in the well 1AS-33-AM. It was drilled in the Solimões Basin, Amazonas State, Brazil, reaching 405 m in depth. We identified 152 palynomorphs, in 32 samples, among them some biostratigraphical markers, such as Crassoretitriletes vanraadshoovenii, Fenestrites spinosus, Cichoreacidites longispinosus, Ladakhipollenites? caribbiensis and Echitricolporites mcneillyi, allowing us to recognise four biozones sensu Lorente (Citation1986): Crassoretitriletes Interval Zone (399.10–276.70 m), Asteraceae Interval Zone (276.70–262.00 m), Psilatricolporites caribbiensis Interval Subzone (239.90–70.00 m) and Echitricolporites–Alnipollenites Interval Subzone (70–32 m). The palynological and lithostratigraphical results indicate two environmental phases. The palynomorph association presents a change marked by the sudden appearance and predominance of Grimsdalea magnaclavata from 239.90 m upwards and a general increase in the number of species. The lithostratigraphy shows from approximately the same depth greater amounts of sandstones towards the top of the well, suggesting a change from a paralic to a fluvial environment of higher energy. The first phase can be associated with the Pebas/Acre depositional systems, wetlands composed by lakes and swamps with seasonal floods that existed from 23 to 7–5 Ma. The second phase indicates a fluvial system that may be interpreted as a record of the modern Amazon transcontinental fluvial system, which was already established in the Pliocene.
Acknowledgements
We would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for sponsoring this study. We would also like to thank the Serviço Geológico do Brasil (CPRM) and Departamento Nacional de Produção Mineral (DNPM) for the samples and Petrobrás/CENPES for the confocal photomicrography of the dinoflagellate cyst.
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No potential conflict of interest was reported by the authors.
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Notes on contributors
Fatima P.R. Leite
Fatima Praxedes Rabelo Leite is currently a post-doctoral fellow at the Universidade Federal de Mato Grosso, Brazil. She earned her bachelor' s degree in biology from the Universidade Santa Ursula in 1990 and her master's degree is in sedimentary geology, awarded by the Universidade de São Paulo in 1997. Fatima then obtained a PhD from the Universidade Federal de Brasília in 2006. She has undertaken two postdoctoral contracts at the Smithsonian Tropical Research Institute, Panama in 2007 and 2010/2011. Fatima' s research is on the Neogene biostratigraphy, palaeoecology and palynology of Amazonia.
Jackson Paz
Jackson Douglas Silva Da Paz is a lecturer at the Universidade Federal de Roraima, Brazil. He earned his bachelor' s degree in geology from the Federal University of Amazonas in 1998; his master's degree was awarded by the Universidade Federal do Pará in 2000. Jackson also received his PhD in from the Universidade Federal do Pará (2005). His interests are Early Cretaceous continental sedimentology, palaeoecology and stratigraphy.
Dermeval A. do Carmo
Dermeval Aparecido Do Carmo is a lecturer at the Universidade Federal de Brasília, Brazil. He holds bachelor' s, master' s and PhD degrees. Most of his publications are on Cretaceous micropalaeontology, but he has also worked on Triassic, Neogene and Quaternary material. Recently, Dermeval has been researching Ediacarian and Lower Palaeozoic micropalaeontology.
Silane A. Silva-Caminha
Silane A.F. Da Silva Caminha is a lecturer at the Universidade Federal de Mato Grosso, Brazil. She earned her bachelor' s degree in biology in 2001 from the Universidade Federal de Rondônia, and her master' s in botany from the National Institute for Amazon Research (INPA). In 2008 Silane finished her PhD on ecology at INPA. Silane is leader of two research groups, namely the palaeontology of Mato Grosso and Amazonian palynology. Her interests are Neogene pollen analysis, palaeoecology and pollen morphology, especially the origin and evolution of the Amazon and Pantanal.