Mixed siliciclastic–carbonate sedimentation in an evolving epicontinental sea : aptian record of marginal marine settings in the interior basins of north-eastern Brazil.
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2021
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Resumo
The Aptian evaporitic transitional sequence (sag phase) of the Brazilian mar-
ginal basins records the first connection between the Central and South Atlan-
tic oceans in the equatorial area. During this phase, lacustrine carbonate
reservoirs and giant salt deposits developed in the southern basins of Santos
and Campos, forming world-class petroleum reservoirs. The sag succession is
also well-preserved in the interior rift basins of north-eastern Brazil, where
upper Aptian strata are represented by a continuous section. This contribution
presents an interpretation of the evolution of a third-order depositional
sequence comprising lacustrine limestones, marine siliciclastic facies and
evaporite deposits of the intracontinental Araripe Basin. The Lowstand Sys-
tems Tract is characterized by fluvial deposits filling accommodation gener-
ated during the syn-rift phase. The overlying deposits comprise marine facies
with preservation of dinoflagellates and marine ichnotaxa, evidencing marine
deposition in bayhead delta settings. The transgressive surface is represented
by limestones, including the Konservat–Lagerstatte € laminites, onlapping the
basement rocks. Above, tide-dominated bay deposits with distinct subtidal,
intertidal and supratidal portions are recorded. The Maximum Flooding Sur-
face is a dark shale below foreshore to shoreface facies, marking the beginning
of the Highstand Systems Tract, culminating with deposition of evaporites
(gypsum and anhydrite). The stratigraphic architecture and palaeocurrents
measured in different facies associations suggest that marine waters reached
the basin from the south. The data unequivocally records late Aptian marine
ingressions of an incipient South Atlantic Ocean over the interior basins of
north-eastern Brazil, while lacustrine conditions were still prevailing in the
Pre-Salt sag units of the Santos and Campos basins.
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Cretaceous Konservat–Lagerstatte, Epicontinental marine ingression, Mixed carbonate–siliciclastic system, Pre-Salt analogue
Citação
VAREJÃO, F. G. et al. Mixed siliciclastic–carbonate sedimentation in an evolving epicontinental sea: aptian record of marginal marine settings in the interior basins of north-eastern Brazil. Sedimentology, v. 68, p. 2125-2164, 2021. Disponível em: <https://onlinelibrary.wiley.com/doi/full/10.1111/sed.12846>. Acesso em: 29 abr. 2022.