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Start Over Descriptor "Coastal deposits" Journal brazilian journal of geology
3 results on '"Coastal deposits"'

1. Sequence stratigraphy of fluvial to shallow-marine deposits: The case of the early Permian Rio Bonito Formation, Paraná Basin, southernmost Brazil

Author

Ricardo Maahs, Juliano Küchle, Claiton Marlon dos Santos Scherer, and Renata dos Santos Alvarenga

Subjects
Sedimentology, estuarine deposits, coastal deposits, tide, wave, Guatá Group, Geology, QE1-996.5
Abstract

Abstract This study presents new sedimentology data and attempts to understand coastal processes, sedimentary dynamics and stratigraphic patterns of the Rio Bonito Formation (early Permian) in Paraná Basin, southern Brazil. The study was performed based on the description of five cores, located in a small-scale area - São Gabriel City - in Rio Grande do Sul State, southern Brazil. Eighteen facies were described and grouped into nine facies associations. Later, these facies associations were then grouped into three depositional systems: fluvial, tide-dominated estuary and wave-dominated shallow-marine depositional systems. A paleoenvironmental evolution is proposed using three block diagrams showing the paleoenvironmental stage (S1, S2, and S3). S1 contains the oldest part of the sedimentary record with predominance of fluvial system deposits, S2 comprises dominantly estuarine system deposits, and S3 is mostly composed of shallow-marine deposits. Stratigraphic framework showed a general retrogradacional tendency, with thickness variations along the systems tracts that allowed for the construction of a curve of accommodation changes to the Rio Bonito Formation in the region of São Gabriel during the early Permian. This study contributes to a better understanding of the fluvial discharges, tidal and oscillatory (wave) currents and their interactions and dominances along stratigraphic records of coastal deposits.

Published
2019
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2. Sequence stratigraphy of fluvial to shallow-marine deposits: The case of the early Permian Rio Bonito Formation, Paraná Basin, southernmost Brazil.

Author

Maahs, Ricardo, Küchle, Juliano, dos Santos Scherer, Claiton Marlon, and dos Santos Alvarenga, Renata

Subjects
SEQUENCE stratigraphy, MARINE sediments, ALLUVIUM
Abstract

This study presents new sedimentology data and attempts to understand coastal processes, sedimentary dynamics and stratigraphic patterns of the Rio Bonito Formation (early Permian) in Paraná Basin, southern Brazil. The study was performed based on the description of five cores, located in a small-scale area -- São Gabriel City -- in Rio Grande do Sul State, southern Brazil. Eighteen facies were described and grouped into nine facies associations. Later, these facies associations were then grouped into three depositional systems: fluvial, tide-dominated estuary and wave-dominated shallow-marine depositional systems. A paleoenvironmental evolution is proposed using three block diagrams showing the paleoenvironmental stage (S1, S2, and S3). S1 contains the oldest part of the sedimentary record with predominance of fluvial system deposits, S2 comprises dominantly estuarine system deposits, and S3 is mostly composed of shallow-marine deposits. Stratigraphic framework showed a general retrogradacional tendency, with thickness variations along the systems tracts that allowed for the construction of a curve of accommodation changes to the Rio Bonito Formation in the region of São Gabriel during the early Permian. This study contributes to a better understanding of the fluvial discharges, tidal and oscillatory (wave) currents and their interactions and dominances along stratigraphic records of coastal deposits. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
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3. Mudanças no nível do mar durante o Pleistoceno Tardio registradas em depósitos fluviais e influenciados por maré da Formação Itaubal, porção onshore da Bacia da Foz do Amazonas, Brasil

Author

José Tasso Felix Guimarães, Afonso César Rodrigues Nogueira, Isaac Salém Salém Alves Azevedo Bezerra, and Werner Truckenbrodt

Subjects
geography, geography.geographical_feature_category, Pleistocene, Coastal plain, Pleistoceno, lcsh:QE1-996.5, Fluvial, Last Glacial Maximum, Unconformity, coastal deposits, Itaubal Formation, depósitos costeiros, lcsh:Geology, Paleontology, Amazônia, Amazonia, mudanças no nível do mar, Formação Itaubal, Facies, General Earth and Planetary Sciences, sea-level changes, Quaternary, Holocene, Geology
Abstract

The Pleistocene deposits exposed in the Amapá Coastal Plain (onshore portion of the Foz do Amazonas Basin, northeastern South America) were previously interpreted as Miocene in age. In this work, they were named as "Itaubal Formation" and were included in the quaternary coastal history of Amazonia. The study, through facies and stratigraphic analyses in combination with optically stimulated luminescence (single and multiple aliquot regeneration), allowed interpreting this unit as Late Pleistocene tidal and fluvial deposits. The Itaubal Formation, which unconformably overlies strongly weathered basement rocks of the Guianas Shield, was subdivided into two progradational units, separated by an unconformity related to sea-level fall, here named as Lower and Upper Units. The Lower Unit yielded ages between 120,600 (± 12,000) and 70,850 (± 6,700) years BP and consists of subtidal flat, tide-influenced meandering stream and floodplain deposits, during highstand conditions. The Upper Unit spans between 69,150 (± 7,200) and 58,150 (± 6,800) years BP and is characterized by braided fluvial deposits incised in the Lower Unit, related to base-level fall; lowstand conditions remained until 23,500 (± 3,000) years BP. The studied region was likely exposed during the Last Glacial Maximum and then during Holocene, covered by tidal deposits influenced by the Amazon River. RESUMODepósitos pleistocenos expostos na Planície Costeira do Amapá (porção onshore da Bacia da Foz do Amazonas, nordeste da América do Sul) foram anteriormente interpretados como de idade miocena. Neste trabalho, esses depósitos foram chamados de "Formação Itaubal" e incluídos na evolução costeira quaternária da Amazônia. O estudo, mediante o uso de análise de fácies e estratigrafia em combinação com luminescência opticamente estimulada (regeneração de alíquotas simples e múltiplas), permitiu posicionar essa unidade no Pleistoceno Tardio, interpretada como depósitos fluviais e influenciados por maré. A Formação Itaubal, que sobrepõe discordantemente rochas intensamente intemperizadas do embasamento do Escudo das Guianas, foi subdivida em Unidade Inferior e Superior, de caráter progradante, separadas por desconformidade relacionada à queda do nível do mar. A Unidade Inferior apresenta idades entre 120.600 (± 12.000) e 70.850 (± 6.700) anos AP e consiste de depósitos de submaré, canal fluvial meandrante influenciado por maré e depósitos de planície de inundação, depositados durante condições de nível de mar alto. A Unidade Superior apresenta idades entre 69.150 (± 7.200) e 58.150 (± 6.800) anos AP e é caracterizada por depósitos de canal entrelaçado, que retrabalham a Unidade Inferior, depositada em condições relacionadas à queda do nível de base. Condições de nível de mar baixo permaneceram até 23.500 (± 3.000) anos AP. A região estudada foi provavelmente exposta durante o Último Máximo Glacial e, posteriormente, durante o Holoceno, recoberta por depósitos influenciados por maré oriundos do Rio Amazonas.

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