Evolução estratigráfica da sequência neocarbonífera-eotriássica da Bacia do Parnaíba, NE do Brasil
The Parnaíba Basin consists in an intracratonic basin whose sucession of rocks is arranged in five supersequences. The Upper Carboniferous-Lower Triassic Sequence represents the third major sedimentary cycle and corresponds to Balsas Group, which is divided into four units: Piauí Formation, Pedra...
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| Formato: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/21057 |
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| Resumo: | The Parnaíba Basin consists in an intracratonic basin whose sucession of rocks is
arranged in five supersequences. The Upper Carboniferous-Lower Triassic Sequence
represents the third major sedimentary cycle and corresponds to Balsas Group, which is
divided into four units: Piauí Formation, Pedra de Fogo Formation, Motuca Formation
and Sambaíba Formation, from base to top. Different interpretations have been made by
several authors in recent decades to interpreted the depositional system and
environments related to each unit that belongs to this sequence. In general way, it is
described as a thick pack of siliciclastic sediments deposited under complex conditions,
varying from clastic/evaporitic shallow marine to lacustrine and desert environment.
Aiming to clarify the sedimentary sequence evolution, this work underwent a
stratigraphic analysis of the Upper Carboniferous-Lower Triassic deposits by applying
modern concepts of the sequence stratigraphy based on well and seismic database.
Three main depositional sequences of higher frequency were identified in each well
analyzed. The sequence 1 corresponds to rocks initially deposited by a fluvial system
with braided channel characteristics which evolved to shallow marine with coastal
sabkha conditions related to a transgressive stage, that later evolved to a deltaic system.
The Sequence 2 corresponds to rocks deposited in a lacustrine/desert environment
associated with sabkha generated during a period of increased aridity in which the area
occupied by the Parnaíba Basin had been suffering. The registration of a major
regressive phase is shown in Sequence 2 which evolved to a dominantly desert
environment recorded in Sequence 3. Seismic stratigraphy analyses allow to define a
series of stratigraphic surfaces and related genetic units, as well as to infer its lateral
expression. Seismic facies associated with such sequences are dominantly parallel and
sub-parallel, with good lateral continuity, suggesting the sedimentary rate was relatively
constant during deposition. |
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