Geology, Geochemistry, and Geochronology (U-Pb) of the Rio Fortuna Gneiss - Serra do Baú Intrusive Suite - Paraguá Terrane - SW Amazonian Craton

O Gnaisse Rio Fortuna aflora na região da serra Santa Bárbara, nas imediações do Destacamento Militar Fortuna, na fronteira Brasil-Bolívia. Estes ortognaisses estão inseridos no Terreno Paraguá, em um setor afetado pela Orogenia Sunsás (1.0 a 0.9 Ga.). São classificados como ortognaisses de composição monzo a granodiorítica, com registros de, no mínimo, três fases de deformação. Idade U-Pb em zircão de 1.711 ± 13 Ma obtida por ablação a laser MC-ICP-MS, é considerada como correspondendo à idade de cristalização do protólito ígneo. Geoquimicamente, essas rochas constituem uma sequencia ácida formada por um magmatismo subalcalino, do tipo cálcio-alcalino de alto potássio, metaluminoso a peraluminoso.

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.

ICE-KEEL SCOUR MARKS IN THE GEOLOGICAL RECORD: EVIDENCE FROM CARBONIFEROUS SOFT-SEDIMENT STRIATED SURFACES IN THE PARANA BASIN, SOUTHERN BRAZIL

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caracterização estrutural do Lineamento de Piúma e sua influência na porção norte da Bacia de Campos

The detailed study of the Brazilian continental margin basins became possible with the advancement of geophysical tools, with emphasis on seismic reflection. Characterizing the structural and stratigraphic elements of Brazil’s marginal basins they realized that there was a relationship with structures present on the adjacent continental basement. So many works began to be made to understand this relationship and know the major factors that influenced the evolution of the continental margin. The study area of this work includes the northern portion of the Campos Basin and the continental outcropping adjacent areas, which corresponds to the northern of Rio de Janeiro state and the southern of Espirito Santo state. This area stands an important structural feature of NW-SE direction with a projection to the Campos Basin called Lineamento de Piúma. The outcropping basement rocks belongs to the Ribeira Belt which was bonded to other mobile bands forming the continent Western Gondwana during the Brasiliano Cycle, which later fragmented giving rise to the Atlantic Ocean. The opening of the ocean results on the formation of the marginal basins of Brazil. These basins have continental, transitional and marine facies. On Campos Basin the continental phase resulted on the formation of horsts and grabens bounded by synthetic and antithetic faults. Continuing rifting formed the saline lakes that deposited siliciclastic and carbonate sediments. The transitional phase resulted on thick packages consist of evaporites (halite and anhydrite) that was deposited in lagoon environment, tectonically quiet arid and semi-arid. The marine phase it deposited siliciclastic and carbonate in the Campos Basin resulting in shales, marls, limestones, ritmito, turbidites, sandstones and others. The objective of this study is to investigate the possible continuation... (Complete abstract click electronic access below)

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

Geologia da região da Fazenda Salobo, Vazante - MG

Important deposits of Zn-Pb associated with the Vazante Group, and Au in Group Canastra occur in the Vazante-Paracatu region (MG). They are located in the Brasília Fold Belt, which was generated from a convergent tectonic in the Brasiliano cycle, forming a complex system of imbricated nappes and faults. This study aims to characterize stratigraphic, structural and metamorphic aspects of an area, located in the Salobo’s farm region. A geological mapping in 1:20,000 scale was executed in order to identify the outcropping lithotypes and to collect structural measures. Drill holes were described to support the surface data and samples were selected for the preparation of thin and polished sections. In this context, the occurrence of rock types and hydrothermal processes that had not been previously described were found, for example layers of phosphatic quartzite in the Serra do Poço Verde Formation (SPV), hydrothermal hematites from martitization magnetite in contact by detachment of the Serra do Garrote Formation and SPV in the Vazante Group and layers of microbanded iron formations in Paracatu Formation (Canastra Group). In the area, four deformational phases were recognized, occurring progressively, in which two of them are related to convergent tectonic, with the development of thrust faults, one is associated to tectonic escape and/or reactivation of basement faults and the last has a distensive character, representing the post-convergence relaxation. The metamorphism in the area was subgreenschist facies, reaching lower greenschist, with temperatures up to 350°C

Evolução tectônica do Trend Badejo-Linguado-Pampo, bacia de Campos (RJ)

The regional geological work for the oil industry, in order to find potential areas for hydrocarbon exploration and understand the geological parameters responsible for the formation of the deposit are known importance. This work fits into that scenario, with regional research with the aid of wells and 2D and 3D seismic sold by DBEP (Database Exploration and Production). Were also used as GeoGraphix software package Landmarks modules Prizm and SeisWork 2D and 3D, and the Surfer 8 and ArcGIS 9.2 with the infrastructure provided by the 05 PRH - ANP with LSGI (Laboratory of Seismic and Geological Interpretation) located at UNESP -- Campus de Rio Claro. The work focuses on study the trend of oil-Badejo-Linguado-Pampo, producing fields since the beginning of offshore holdings. The Campos Basin is now known as the offshore basin of the country more productive, and the high structural Badejo is a structure of great importance in the basin presents itself as largely responsible for the conditioning of hydrocarbon fields Pampo, Linguado and Badejo. Therefore this work also aims to increase knowledge of the region in terms of tectonic and stratigraphic characterize the geometry of the structures associated with this major regional structure. For this we used structural contour maps of the main chrono-horizons, and Isopach maps for the purpose of better understanding the tectono-sedimentary evolution of the Campos Basin locally.

Coquinas eoaptianas do sudoeste da Bacia de Campos: fácies deposicionais, eventos diagenéticos e fatores controladores da qualdade do reservatório

Pós-graduação em Geologia Regional - IGCE

A formação Serra Alta, Permiano, no centro-leste do Estado de São Paulo, Bacia do Paraná, Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Review of Deep Time and the Texas High Plains: History and Geology by Paul H. Carlson

This brief book is a history of the Lubbock Lake Landmark site, a nationally recognized archeological site located on the Texas southern High Plains on the north side of the city of Lubbock. The location has been the subject of intense investigations by archaeologists since 1939. Paul H. Carlson, a noted author and professor of history at Texas Tech University, states that his purpose was to go back through what John McPhee called "deep time" to show how the Lubbock Lake location was formed and was used by humans through time. He accomplishes this in five chapters.

Correlation of the middle Eocene Kellogg Shale of northern California

The Kellogg Shale of northern California has traditionally been considered to be late Eocene in age on the basis of benthic foraminifer, radiolarian, and diatom correlations. The 30-m-thick Kellogg section exposed west of Byron, California, however, contains middle Eocene planktonic foraminifers (Zone P12), coccoliths (Subzones CP13c and CP14a), silicoflagellates (Dictyocha hexacantha Zone), and diatoms. Quantitative studies of the silicoflagellates and diatoms show a general cooling trend through the section which is consistent with paleoclimatic trends for this part of the middle Eocene (ca. 42-45 Ma) from elsewhere in the world. Seven new silicoflagellate taxa (Corbisema angularis. C, exilis, C, hastate miranda, C. inermis ballantina, C. regina, Dictyocha byronalis, Naviculopsis Americana) and one new coccolithophorid species (Helicosphaera neolophota) are described.

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.

How Old Is Luzia? Luminescence Dating and Stratigraphic Integrity at Lapa Vermelha, Lagoa Santa, Brazil

During an excavation in the 1970s, a disarticulated female human skeleton, later nicknamed Luzia, was discovered at 12m depth at Lapa Vermelha rockshelter in central Brazil. Radiocarbon dating of associated charcoal suggested an age of 11.4-16.4 ka for the skeleton. The scattering of the skeletal parts, some uncertainty about the exact provenience of the skeleton, and evidence of pervasive insect turbation in the archaeological layers have raised doubts about the accuracy of the age. Luminescence dates for the depositional ages of the sediments at Lapa Vermelha are reported here. Single-grain optically stimulated luminescence (OSL) of quartz along with grain-size, chemical and micro-morphological analyses of the sediments were employed to assess stratigraphic integrity, particularly the degree of sediment mixing. These various lines of evidence point to high stratigraphic integrity with little mixing at Lapa Vermelha. Sediments closest to where Luzia was recovered give OSL ages ranging from 12.7 to 16.0 ka, thus not refuting the original dates. (C) 2010 Wiley Periodicals, Inc.

Facies associations and controls on the evolution from a coastal bay to a lagoon system, Santa Catarina Coast, Brazil

The diverse Holocene morphological features along the south coast of the state of Santa Catarina include lagoons and residual lakes, a barrier, a delta (constructed by the Tubarao River), and pre-existing incised valleys that have flooded and filled. This scenario contains the sedimentary record of the transition from a bay to a lagoon system, which occurred during the rise and subsequent semi-stabilisation of the relative sea-level during the Holocene. The geomorphological evolution of this area was investigated using a combination of morphology, stratigraphic analysis of rotary push cores, vibracores and trenches with radiocarbon dating, taxonomic determination and taphonomic characterisation of Holocene fossil molluscs. Palaeogeographic maps were constructed to illustrate how the bay evolved over the last 8000 years. The relative sea-level rise and local sedimentary processes were the prime forcing factors determining the depositional history and palaeogeographic changes. The Holocene sedimentary succession began between 8000 and 5700 cal BP with the deposits of transgressive sandsheets. These deposits correspond to the initial marine flooding surface that was formed while the relative sea-level rose at a higher rate than the input of sediments, prior to the formation of the coastal barrier. The change from a bay to a lagoon system occurred around 5700 and 2500 cal BP during the mid-Holocene highstand with the formation of the barrier and with the achievement of a balance between sea-level rise and sedimentary supply. Until 2500 cal BP, the presence of this barrier, the following gentle decline in sea level and the initial emergence of back-barrier features restricted the hydro-dynamic circulation inside the bay and favoured an increase in the Tubarao River delta progradation rate. The final stage, during the last 2500 years, was marked by the increasing back-barrier width, with the establishment of salt marshes, the arrival of the delta in the back-barrier, and the advance of aeolian dunes along the outer lagoon margins. This study shed light on the mechanisms of coastal bay evolution in a setting existed prior to the beginning of barrier lagoon sedimentation. (C) 2012 Elsevier B.V. All rights reserved.

Seismites as a tool in the palaeoenvironmental reconstruction of fluvial deposits: The Cambrian Guarda Velha Formation, southern Brazil

Soft-sediment deformation (SSD) is widely described in the literature, but there is no clear consensus regarding its origin and significance. Existing models for SSD in fluvial sediments do not clearly demonstrate a relationship between the structures, preserved facies expression, and larger-scale depositional architecture. In this study several types of SSD structures are recorded in Cambrian fluvial deposits and these occur interbedded with undeformed strata throughout the entire stratigraphic interval. The random distribution of these features in relation to primary facies types and fluvial forms indicates that they have neither a direct nor indirect relationship with any depositional processes or bedform type. We propose that the relationship of SSD at the bed-set-scale to larger-scale depositional architecture, combined with tectono-stratigraphic analysis allows the determination of both short-term fluvial hydraulic conditions in ancient stream systems, such as the nature of the flow regime responsible for depositing ancient fluvial stream successions, and the long-term subsidence rates, in the form of mean recurrence interval of the seismic events responsible for triggering the generation of SSD in tectonically active basins. (c) 2012 Elsevier B.V. All rights reserved.