Microfacies and sequence stratigraphy of the Amapa Formation, Late Paleocene to Early Eocene, Foz do Amazonas Basin, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evolução tectono-metamórfica das rochas máficas e ultramáficas da região de Águas de Lindóia e Arcadas, estado de São Paulo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise tectono-estratigráfica das sequências permotriassica e jurocretácea da bacia Chacoparanense Uruguaia (Cuenca Norte)

Pós-graduação em Geologia Regional - IGCE

Evolução tectono-sedimentar mesozóico-cenozóica da região de Franca

Pós-graduação em Geologia Regional - IGCE

Heavy mineral as a tool to refine the stratigraphy of kaolin deposits in the Rio Capim Area, Northern Brazil

Estudos de minerais pesados provenientes em depósitos cauliníticos da Formação Ipixuna na região do rio Capim (Brasil) revelaram uma mineralogia matura a supermatura, representada dominantemente por zircão e turmalina e, subordinadamente, rutilo, cianita e estaurolita. Os minerais encontrados não variam muito, entretanto cada unidade caulinítica apresenta uma assinatura particular definida por diferenças nasproporções entre os principais minerais, assim como em suas características texturais. Este trabalho demonstrou que asunidades de caulim soft (inferior) e semi-flint (superior) podem ser consideradas seqüências deposicionais distintas. As altas percentagens de opacos em relação aos minerais transparentes e altos teores de zircão são diagnósticos da unidade caulinítica inferior. O incremento no volume de grãos de zircão e turmalina arredondados a subarredondados na unidade caulinítica superior sugere que esta inclui grãos que foram submetidos a um grau mais elevado de retrabalhamento. O aumento no volume de grãos não alterados de estaurolita e cianita na unidade superior leva a concluir que, além da reciclagem sedimentar, uma fonte distinta deve ser invocada. Estes resultados também mostram que as características da assembléia de minerais pesados da unidade intermediária são comparáveis com aqueles da unidade superior, o que sugere mesmo posicionamento estratigráfico.

Strontium isotope stratigraphy of the Pelotas Basin

Dados da razão isotópica de estrôncio foram obtidos a partir da análise de conchas de foraminíferos recuperadas dos depósitos terciários da Bacia de Pelotas visando o refinamento do arcabouço cronoestratigráfico dessa seção. Este artigo representa a primeira abordagem à obtenção de idades numéricas para esses estratos. A estratigrafia de isótopos de estrôncio permitiu a identificação de oito hiatos deposicionais na seção Eoceno-Plioceno, aqui classificados como desconformidade, além de uma seção condensada. O reconhecimento de hiatos deposicionais representa um importante avanço, considerando a baixa resolução cronoestratigráfica da seção cenozóica da Bacia de Pelotas. Além disso, foi identificado um substancial aumento na taxa de sedimentação na seção neomiocênica. Tendências gerais de paleotemperatura e produtividade foram identificadas com base em dados das razões isotópicas de oxigênio e carbono da seção Oligoceno-Mioceno. Essas tendências são coerentes com eventos globais, evidenciando as condições ambientais durante a sedimentação.

Modelo tectono-estrutural dos campos de petróleo Namorado, Cherne e Albacora

The main goal in this research is a tectono-estructural characterization of the Cherne, Albacora and Namorado Fields, located at Campos Basin, in order to investigate the relationship between the geologic evolution and the rock´s physical properties of the reservoir, and how they affect the hydrocarbon accumulation in those fields. Well correlations show that the inferior turbidites have a regional lateral continuity. Basic petrophysics analysis, calculated here, shows that the three fields present porosity values that range from 15 to 20%, shale volume range from 26 to 30% and formation water saturation range from 23 to 45%, based on formation water resistivity dada from Albacora Field. Petrophysics maps feature a trend in Albacora Field that increase the porosity values to SE, and in Cherne and Namorado Field the trend increase towards N. Seismic horizons where interpreted between the first appearance of the Namorado Sandstone and the top of Quissamã Formation. This interval presents normal listric faulting, in Cherne and Namorado Field with NWSE and NE-SW direction, and sedimentation trend to NW-SE, in Albacora Field the faulting presents a NNE-SSW and N-S direction, with a sedimentation trend to NE-SW. Seismic attribute maps present amplitude anomalies close to the producing wells, and on Namorado Field, it indicates a potential hydrocarbon accumulation in the NE region. For each field is indicated laboratory tests for a better characterization of the petrophysical properties, since that they don’t form the same reservoir level, therefore, not influencing the water saturation calculation

Interpretação tectono-estratigráfica do reservatório Quissamã (Eo-meso-albiano) nos campos de Pampo, Bicudo e Bonito, Bacia de Campos

Hydrocarbon accumulations occur in marine carbonate reservoirs of Quissamã Formation (early to midlle Albian), southwest Campos Basin. We investigated Pampo, Bicudo and Bonito fields, in order to understand the tectono-structural framework of oncolite/bioclast coarse-grained calcarenite reservoir and the calcilutite-marl-shale sealing interval (Late Albian to Turonian). The database of eleven wells from those fields allowed to elaborate structural sections correlating the Macaé Group – both Quissamã reservoir and Outeiro seal, the latter corresponding to the tectonic deepening phase of basin evolution. Based on density and electric logs, it was prepared structural sections of the carbonate reservoirs with consequent identification of porous zones and oil-water contacts. An extensive 3-D seismic database (~300 Km2) allowed to map three reflectors which represent the limiting units of Macaé Group

Análises tectono-estratigráfica e faciológico-diagenética da coquina-reservatório Lagoa Feia, Campo de Linguado, Bacia de Campos

A tectono-stratigraphic study of bivalve coquina-reservoir of Linguado Field allowed to identify two trends of permoporosity development. The delineation of these depositional-diagenetic traps were made through structural and stratigrafic cross-sections and maps. It resulted in the identification of shelf-ramp systems (tilted to SSE), it tickens from 60 to 70 meters and ends against an antithetic fault. The main coquina is bounded by fine siliciclastic units, white clay (low Gamma Ray values) or shale (high Gamma Ray values) lithologies, influencing diagenesis of basal or top coquina limestones (cimented, non-porous). Also in the middle of coquina-reservoir the “clayer” material is also associated with cemented carbonates, with also compartimentalize the reservoir into two subzones. The coquina porosity of the subzones is taken from density-neutron logs, while induction log estimates permeabilities and fluid saturations. It’s noticed the porosity development into pairs, good one followed by a regular/poor one and vice versa. These pairs form verticals succession, pair cycles where porosity improves or decreases upwards. These two scales of pore heterogeneity impose strong layering to the reservoir, and influences fluid saturations, oil-water contacts and porosity cut-offs. In a cross-section with density and induction logs, it can be observed the porosity variation along the shelf-ramp coquina (between 3LI_0004_RJS e 3RJS_0157C_RJ), the porosity is better developed in a downdip direction in the case of the two shelf wells, and also be the three ramp wells. The southern west downdip, 3RJS_0157C_RJ well, has best porosity pairs-cycles; however, its lowest structural conditions favour water saturation. Therefore it is fundamental for reservoir fluid evaluation a cross-plot analysis of RHOB-NPHI and Induction logs

Caracterização tectono-sedimentar do Grupo Lagoa Feia (Eocretáceo) no Campo de Pampo, sudoeste da Bacia de Campos

The Lagoa Feia Group (Early Cretaceous) is widely distributed around the Campos Basin, forming deep prospects in the basin. It has two large coquinas platforms shellfish, and the lower deck constituent important reservoir in the southwestern of this basin, a producer of oil in the trend-Badejo-Linguado-Pampo. Due to the rising national energy demand is necessary to see the incorporation of technical knowledge and training of human resources in the knowledge of petroleum reservoirs. In this sense, the Pampo Field, as well as other fields of the trend, fall as interesting target area for study. Accumulations of hydrocarbons are partitioning structural - stratigraphic only for the three fields. They are mixed origin of traps, with influence of structural, stratigraphic and diagenetic. With the development of catchment areas of the latter condition has manifested itself in such a way to verify parts with nonproducing wells, which are observed in the intervals coquinas are closed, with reduced thickness and / or low quality porous. The understanding of these accumulations, by testing structural, stratigraphic and reservoir and the use of geological and geophysical techniques, will bring a better understanding of the portions relating to economic accumulation or subeconomic development of hydrocarbons in this region, contributing to the scientific knowledge of the Pampo Field.

Diatom stratigraphy of the lower Pliocene part of the Sisquoc Formation, Harris Grade section, California

Lower Pliocene diatoms were studied from the Sisquoc Formation and lowermost Foxen Mudstone, exposed along Hams Grade north of Lompoc, California, to refine the diatom biostratigraphy of post-Monterey Formation sediments in California. Sixty-seven diatom taxa were identified in the 25 samples examined from the 790-m thick (2950-ft) section. The diatoms are assignable to the uppermost Nitzschia reinholdii Zone and Thalassiosira oestrupii Zone of Damn (1981), and five tentative subzones for local correlation are proposed. Regional correlations and taxon occurrence are discussed, and the base of the Nitzschia reinholdii Zone is redefined as at the last occurrence of Thalassionema schraderi.

The Oligocene-Neogene deep-sea Columbia Channel system in the South Brazilian Basin: Seismic stratigraphy and environmental changes

The Columbia Channel (CCS) system is a depositional system located in the South Brazilian Basin, south of the Vitoria-Trindade volcanic chain. It lies in a WNW-ESE direction on the continental rise and abyssal plain, at a depth of between 4200 and 5200 m. It is formed by two depocenters elongated respectively south and north of the channel that show different sediment patterns. The area is swept by a deep western boundary current formed by AABW. The system has been previously interpreted has a mixed turbidite-contourite system. More detailed study of seismic data permits a more precise definition of the modern channel morphology, the system stratigraphy as well as the sedimentary processes and control. The modern CCS presents active erosion and/or transport along the channel. The ancient Oligo-Neogene system overlies a ""upper Cretaceous-Paleogene"" sedimentary substratum (Unit U1) bounded at the top by a major erosive ""late Eocene-early Oligocene"" discordance (D2). This ancient system is subdivided into 2 seismic units (U2 and U3). The thick basal U2 unit constitutes the larger part of the system. It consists of three subunits bounded by unconformities: D3 (""Oligocene-Miocene boundary""), D4 (""late Miocene"") and D5 (""late Pliocene""). The subunits have a fairly tabular geometry in the shallow NW depocenter associated with predominant turbidite deposits. They present a mounded shape in the deep NE depocenter, and are interpreted as forming a contourite drift. South of the channel, the deposits are interpreted as a contourite sheet drift. The surficial U3 unit forms a thin carpet of deposits. The beginning of the channel occurs at the end of U1 and during the formation of D2. Its location seems to have been determined by active faults. The channel has been active throughout the late Oligocene and Neogene and its depth increased continuously as a consequence of erosion of the channel floor and deposit aggradation along its margins. Such a mixed turbidite-contourite system (or fan drift) is characterized by frequent, rapid lateral facies variations and by unconformities that cross the whole system and are associated with increased AABW circulation. (C) 2009 Elsevier B.V. All rights reserved.

Microfacies and sequence stratigraphy of the Amapa Formation, Late Paleocene to Early Eocene, Foz do Amazonas Basin, Brazil

On the basis of thin-section studies of cuttings and a core from two wells in the Amapa Formation of the Foz do Amazonas Basin, five main microfacies have been recognized within three stratigraphic sequences deposited during the Late Paleocene to Early Eocene. The facies are: 1) Ranikothalia grainstone to packstone facies; 2) ooidal grainstone to packstone facies; 3) larger foraminiferal and red algal grainstone to packstone facies; 4) Amphistegina and Helicostegina packstone facies; and 5) green algal and small benthic foraminiferal grainstone to packstone facies, divisible locally into a green algal and the miliolid foraminiferal subfacies and a green algal and small rotaliine foraminiferal subfacies. The lowermost sequence (Si) was deposited in the Late Paleocene-Early Eocene (biozone LF1, equivalent to P3-P6?) and includes rudaceous grainstones and packstones with large specimens of Ranikothalia bermudezi representative of the mid- and inner ramp. The intermediate and uppermost sequences (S2 and S3) display well-developed lowstand deposits formed at the end of the Late Paleocene (upper biozone LF1) and beginning of the Early Eocene (biozone LF2) on the inner ramp (larger foraminiferal and red algal grainstone to packstone facies), in lagoons (green algal and small benthic foraminiferal facies) and as shoals (ooidal facies) or banks (Amphistegina and Helicostegina facies). Depth and oceanic influence were the main controls on the distribution of these microfacies. Stratal stacking patterns evident within these sequences may well have been related to sea level changes postulated for the Late Paleocene and Early Eocene. During this time, the Amapa Formation was dominated by cyclic sedimentation on a gently sloping ramp. Environmental and ecological stress brought about by sea level change at the end of the biozone LF1 led to the extinction of the larger foraminifera (Ranikothalia bermudezi). (c) 2009 Elsevier B.V. All rights reserved.

Lapa das boleiras rockshelter: stratigraphy and formation processes at a paleoamerican site in Central Brazil

Lapa clas Boleiras rockshelter, a Paleoamerican archaeological site in Central Brazil, was intensely occupied by humans from 10,000 C-14 BP (11.8 cal kyr BP), until approximately 7500 C-14 BP (8.4 cal kyr BP). In this paper we present some interpretations about the formation processes operating on the site. One of our main conclusions is that the bulk of accumulated sediments at the site is of anthropogenic origin: they are constituted by volumetrically significant quantities of plant ash remains, what is somewhat unexpectedly in view of prevailing models about the lifestyle of Paleoamerican hunter-gatherers in South America. The evidence we discuss below is also consistent with paleoenvironmental data that suggest a dry period during the mid-Holocene in the region, probably leading to a decrease in human occupation [Araujo, A.G.M., Neves, W., Pilo, L.B., Atui, J.P., 2005. Holocene dryness and human Occupation in Brazil during the `Archaic Gap`. Quaternary Research 64, 298-307]. We surmise that both factors underpin a surprising reduction in sediment accumulation at the site during the mid-Holocene. (C) 2008 Published by Elsevier Ltd.