Research Interests:
Research Interests:
Research Interests:
A Sub-bacia Camaquã Oriental compreende exposições da borda leste da Bacia do Camaquã, como o Vale do Piquiri, pertencentes ao Grupo Santa Bárbara (Ediacarano). Estudos estratigráficos de fácies, sistemas deposicionais, proveniência e... more
A Sub-bacia Camaquã Oriental compreende exposições da borda leste da Bacia do Camaquã, como o Vale do Piquiri, pertencentes ao Grupo Santa Bárbara (Ediacarano). Estudos estratigráficos de fácies, sistemas deposicionais, proveniência e paleocorrentes conduziram à subdivisão do Grupo Santa Bárbara na Sub-bacia Camaquã Oriental em duas unidades: (i) Formação Passo da Capela, formada por turbiditos de leques subaquosos; e (ii) Formação Rincão dos Mouras, constituída por arenitos e conglomerados de leques aluviais e sistemas fluviais entrelaçados. Este artigo propõe formular um modelo de evolução de altos estruturais durante o preenchimento de uma bacia rifte. Conglomerados de leques subaquosos da Formação Passo da Capela apresentam composição do arcabouço derivada da própria bacia (arenitos), indicando autofagia, além de rochas do embasamento (quartzitos, xistos, metarriolitos). Análises de paleocorrentes indicam dispersão dos sedimentos segundo NNE, compatível com litotipos do Complexo...
Research Interests:
ABSTRACT: Following the rise of metazoans, the beginning of bioclasticity and substrate competition, the saga of microbial mats was in a fluctuating decline in the end of the Neoproterozoic era. Increases in diversity during the... more
ABSTRACT: Following the rise of metazoans, the beginning of bioclasticity and substrate competition, the saga of microbial mats was in a fluctuating decline in the end of the Neoproterozoic era. Increases in diversity during the Phanerozoic and punctual upturns in the microbial carbonate production occured after the events of global mass extinctions. Gradually along the Phanerozoic, the microbial colonies occupied isolated niches and grazers-free environments, characterized by physically and/or geochemically stressful conditions, such as those found in saline bays, alkaline lakes and hydrothermal or cold seep vents. Here we report one of the oldest occurrences of a vent camp coupled with cold seepage of methane in the geologic record, associated with well-preserved microbialites and elephant skin structures. During the seep activity, oxygen depletion and high salinity conditions are prohibitive for complex animal life, clearing the way to microbial colonies to flourish. Due to the c...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
... means. Stratigraphically equivalent sedimentary samples from the Permian Rio Bonito (in southeastern Brazil) and San Miguel (in eastern Paraguay) formations were collected close to and far from major intrusive bodies. The ...
Research Interests:
Research Interests:
Research Interests:
In the northern/northeastern portion of the intraplate Paraná Basin, the Middle Permian Corumbataí Formation is a ~200m thick succession of mixed siliciclastic (mudstones/sandstones)-carbonatic (micrites and oosparites) rocks, deposited... more
In the northern/northeastern portion of the intraplate Paraná Basin, the Middle Permian Corumbataí Formation is a ~200m thick succession of mixed siliciclastic (mudstones/sandstones)-carbonatic (micrites and oosparites) rocks, deposited in storm-influenced offshore to coastal plain settings. Indeed, bivalve-rich shell-beds (coquines) and bioclastic sansdstones are interpreted as proximal tempestites, which were particularly common in the interval of the Pinzonella illusa and Pizonella neotropica biozones (middle and upper portions of the Corumbataí Formation). Indeed, for more than 20 years, storm-generated flows and waves were regarded as the main sedimentological process responsible for the genesis of those fossil-rich deposits. Herein, we describe by the first time, bivalve-rich concentrations that seems to a sedimentary product of high-energy events other than storms. In the Batalha river section (22°21’30.05”S/47°35’20.17”W), Rio Claro County, State of São Paulo, a silty shale ...
Research Interests:
After the late Cryogenian glaciation the central region of Brazil was the site of extensive deposition of platformal carbonates of the Araras Group. This group includes a basal cap carbonate sequence succeeded by transgressive, deep... more
After the late Cryogenian glaciation the central region of Brazil was the site of extensive deposition of platformal carbonates of the Araras Group. This group includes a basal cap carbonate sequence succeeded by transgressive, deep platform deposits of bituminous lime mudstone and shale. Facies and stratigraphic data combined with carbon and oxygen isotopic analyses of the most complete section of the transgressive deposits, exposed in the Guia syncline, were used to evaluate the depositional paleoenvironment and to test the correlation of these deposits along the belt and with other units worldwide. The studied succession consists of 150 m thick tabular beds of black to grey lime mudstone and shale with predominantly negative δ 13 C PDB values around –2.5 to −1 • / • • . The δ 13 C PDB profile of Guia syncline shows a clear correlation with the upper portion of Guia Formation in the Cáceres region, about 200 km to the southwest. The δ 13 C PDB profile of the Araras Group is compar...
Research Interests:
The endemic Permian, Paranean molluscan fauna evolved within a huge epeiric sea (Paraná and Chaco-Paraná basins, South America; Huab Basin, Namibia, and Main Karoo Basin, South Africa) under conditions of extreme geographic isolation and... more
The endemic Permian, Paranean molluscan fauna evolved within a huge epeiric sea (Paraná and Chaco-Paraná basins, South America; Huab Basin, Namibia, and Main Karoo Basin, South Africa) under conditions of extreme geographic isolation and high environmental stress. In the Brazilian portion of the Paraná Basin, the oldest known members of this remarkable fauna are recorded in the Kungurian Serra Alta Formation, representing the first recolonization of the sea floors after the Irati-Whitehill anoxic event. The Serra Alta Formation is mainly represented by dark grey mudstones interbedded with thin layers of fine-grained sandstones and rare limestones, deposited in oxygen-deficient (dysoxic-anoxic) conditions. Here, we investigated two geological sections in the eastern border of the Paraná Basin, as well the literature data, in order to elucidate the paleoecology of those bivalves. Our results demonstrate that, besides the barren dark grey mudstones, mainly deposited under anoxic condit...
Oxygen-deficient facies dominate the sedimentary record of several epeiric seas and are common in the transgressive systems tracts of several Paleozoic, Mesozoic and younger age intracratonic sedimentary sequences. They are mainly... more
Oxygen-deficient facies dominate the sedimentary record of several epeiric seas and are common in the transgressive systems tracts of several Paleozoic, Mesozoic and younger age intracratonic sedimentary sequences. They are mainly materialized by monotonous, fossil-poor (barren) successions of black shales and/or massive or well-laminated mudstones deposited under conditions of oxygen depletion. During the late Paleozoic, the intracratonic Paraná Basin, located in the central Gondwanaland, was covered by a huge (>1.600.000 km2), shallow and isolated epeiric sea. Oxygen-deficient facies are commonly recorded in the Mesosaurus-bearing Irati Formation (Artinskian) and the barren, dark-grey mudstones of the Serra Alta Formation (Kungurian). Despite the low fossiliferal potential, a detailed sedimentological (sub-cm scale), ichnological, and taphonomical analysis in those deposits indicate a much dynamic and complex paleonvironmental scenario than presented in previous studies. Based ...
ABSTRACT The Permian Serra Alta Formation was generated under transgressive conditions within a large, calm epeiric sea. A monotonous succession of 'barren', massive mud-stones deposited under oxygen-deficient conditions... more
ABSTRACT The Permian Serra Alta Formation was generated under transgressive conditions within a large, calm epeiric sea. A monotonous succession of 'barren', massive mud-stones deposited under oxygen-deficient conditions (mainly below storm wave base) is the main lithofacies of this unit. Fossils are generally rare and diluted in the matrix, but certain intervals contain shell-rich concentrations with well-preserved, closed articulated bivalves, mixed with shells and comminuted debris with variable quality of preservation, all encased in carbonate concretions. Two main scenarios may account for the origin of these bivalve-rich concretions (i.e. unique events in seawater chemistry or unique burial-starvation couplets). Sedimentological and taphonomic information indicates that the final deposition of the original shell-rich mudstone intervals was probably tied to episodic influx of fine-grained sediments in distal settings. Moderate bioturbation is also recorded suggesting low rates of sedimentation prior to early diagenesis. Hence, the fossil concentrations in concretions were formed due to the interplay of event and background sedimentation. These are internally simple concentrations with complex depositional histories. The concretion-bearing beds are not randomly distributed in the Serra Alta Formation. Rather, they are found in the sparsely fossiliferous offshore deposits of the basal to intermediate portions of the unit. Thus, the concretionary mudstone beds and associated deposits are preserved in particular intervals and can be tracked for kilometres. This indicates that the conditions essential for concretion development existed only at particular stratigraphical intervals. Finally, our study strongly corroborates the idea that concretions are critical sources of sedi-mentological, taphonomic and stratigraphical information. □ Biostratinomy, bivalves,