Navegando por Assunto "Bacias (Geologia)"

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Análise faciológica da formação Codó (Aptiano superior) na Região de Codó (MA), leste da Bacia do Grajaú
(Universidade Federal do Pará, 2000-09-11) PAZ, Jackson Douglas Silva da; ROSSETTI, Dilce de Fátima; http://lattes.cnpq.br/0307721738107549
The Codó Formation, focused in this paper, is exposed in the adjacencies of Codó town, eastern Maranhão State, where it consists of intergraded shales, limestones and evaporites, laterally continuous, forming shoaling-upward successions averaging 2.5 m in thickness. Sedimentological features, the abundance of freshwater ostracodes and Charophyte algae, as well as the absence of any marine fauna, characterize this unit as a dominantly lacustrine unit, which can be described by three broad facies associations, attributed to: 1. central lake; 2. transitional lake; and 3, marginal lake. The central lake facies association represents the base of the shoaling upward successions and consists of two facies: a) black shale; and b) evaporite. The dominance of shale beds in this association indicates sedimentation in low energy depositional settings, typical of central lake areas, where the abundance of pyrite and the bituminous composition point to highly reducing conditions. The scarcity of infauna is indicated by the complete absence of bioturbation, which is consistent with anoxia. The evaporite facies point to a highly saline lake setting. The transitional facies association consists of: a)laminated argillite; hb)lime- mudstone; c)peloidal limestone (mudstone to packstone); and d)meso-crystalline limestone. These deposits, between central lake and marginal lake facies associations, own in the middle portion of the shoaling upward cycles, consistent with a transitional lacustrine setting. The marginal lake facies association represents the top of the shoaling upward successions and consists of a variety of intergrading lithofacies: ajmassive pelite; b)calcite-arenite; Cc) ostracodal limestone (wackestone to grainstone); d) pisoidal limestone (packstone) ; e)gipsite-arenite; £f) tuffa; and 9) rhythmite. These deposits show an abundance of sedimentary features (i.e., paleosoil, karstic surface, fenestrae) typical of subaerial and/or meteoric exposure, which is consistent with their interpretation as marginal lake deposits. A lacustrine facies model with ramp margin and low energy flow is proposed for the study area, taking into account the following characteristics: 1) low rates of sediment supply; 2) presence of areas with low relief around the lacustrine basin; 3) abundance of sedimentary features recording episodes of subaerial and/or meteoric exposure; and 4) prevalence of marginal facies. This interpretation is further suggested by: 1) the small thickness of the depositional cycles, which is attributed to decreased accommodation; 2) absence of turbiditic deposits, which are typical in lacustrine settings with pronounced slope break; and 3) absence of resedimented deposits, which are also common in bench margin lacustrine settings. The abundance of black shales and evaporites suggests a hydrologically closed lacustrine basin with stratified and saline water column for the study area. The depositonal cycles identified reveal a regressive character for this lacustrine succession. Three types of cycles were recognized: 1) complete shoaling-upward cycle; 2) incomplete shoaling-upward cycle; and 3) flooding-upward cycle. The origin of these cycles is attributed to tectonism, based on the assymetrical vertical stacking pattern. This interpretation is corroborated by the presence of sin- sedimentary deformational features related to sin- depositional sismic activity. The faciological, palaeontological and geochemical data presented in this work suggested on show that the Late Aptian marine transgression recorded in the northern portion of the São Luís-Grajaú Basin did not reach the Codó area.
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Compartimentação morfotectônica do interflúvio Solimões-Negro
(Universidade Federal do Pará, 2003-11-26) BEZERRA, Pedro Edson Leal; SILVA, Maurício Borges da; http://lattes.cnpq.br/1580207189205228
From the morphostuctural and morphotectonic analysis integrated to the informations of remote sensing images, litoestratighaphy , geomorfology , the seismic data and field investigations was defined the neotectonic structuration and its influence in the elaboration of the relief forms and drainage net during the Upper Tertiary and Quaternary. This relation is shown through the morphotectonic compartimentation of the Solimões-Negro watershed, subject of this research (SA.20-Manaus Sheet). The discussions concentrated in the area of the cenozoics covers which overlay the east and west borders of the Solimões and Amazon paleozoics sedimentary basins, respectively. This area occupies about 290 000 km2, and is situated between the parallels 0° and 4° S and meridians 60° and 66° WGr, in the Amazonian region, involving parcels of Amazon and Roraima States. The geologic units formed during, or imediatelly after, the implantation of the neotectonic regimen are represented by: 1) the Içá Formation formed after the Miocene, probably of the Plio-Pleistocene age; 2) the Pleistocenics Terraces; 3) the Holocenics Terraces; 4) the inundatable watersheds areas of holocenic age; and 5) the Holocenics Alluviums. The modelling of the landscape for the drainage net evidences a relief compartimentation at plains systems, linked to the actual fluvial dynamics, and depressions, normally leveled by a planing surface formed in the Middle Pleistocene, in retaken by erosion, and preserved on tabular watershed. The neotectonic structuration has a direct relationship with the regeneration of the discontinuities of the paleotectonic structuration, that is, with the resurgent tectonic . This old estructuration is defined by: 1) Tacutu Lineament of NE-SO orientation, that show continuity to the northwest quadrant of the area; 2) the Madeira Lineament, also of NE-SO orientation that section the Southeastern quadrant; 3) the Purus Arc with NW orientation that establishes the limits between the Solimões and Amazon basin; e (4) minors lineaments as the Juruá and the Japurá ones, of E-O direction, defined outside of the domains of the research area. The neotectonic tensions field was alliviated through two kinematics pulses of essentially transcorrent nature. In the first pulse, occurred immediately after the inversion of the Amazonian Occidental drainage for east, had established the main corridors of drainage in the predominant NE-SO direction through the northeast of Amazonas and Roraima states in the brasilian territory, reaching the Guyana Republic and the Atlantic Ocean through rift valley of the Tacutu. The second one, predominantly transtensive, occurred in the Upper Pleistocene /Holocene, provoked the redirectioning of this system for the Amazonas hidrographic basin, and answers for the actual configuration of the relief and drainage net. The Relief Systems are differentiate for the degree of development of the drainage net, showing a evident gradation from the most evolued to the less evolued, that is reflected in the configuration of the watershed and its dimensiona, and that register the history of the implantation of the neotectonic structural picture and its geometric and kinematic differentiations. This register is represented through five morfotectonics compartments, called: Juruá River - Purus River Tanspressive Compartment; Madeira River - Purus River Transcorrent Compartment; Negro River- Japurá River Trancorrent Compartment; Negro River - Solimões River Trantensive Compartment; and the Branco River- Negro River Transtensive Compartment. The morphostructural and morphotectonic evolution occurred from southwest to northeast. So, the drainage net show best developed in the Juruá River — Madeira River Compartment; it is in development in the central zone formed by the Madeira River - Purus River, Negro River-Japurá River and Negro River- Solimões River Compartments; and show a initial stage of development in the Negro River- Branco River Compartment. In the northeast border of the Negro River Japurá River Transtensive Compartment, the development of the drainage net is composed, showing features of initial stage, as the amorphous and multibasinal pattern, with other typicals features of drainage net in development. The structures of the Juruá River Purus River Compartment are generated by inverse faults in the Upper Tertiary. In the the Madeira River - Purus River and Negro River — Japurá River compartments they are dextrals directional faults with component of oblique slip, probably of the reverse type in the Tertiary Superior and normal in the Pleistocene; in the Negro River - Solimões River Compartment they are mainly normal and oblique-dextrais types in the Upper Pleistocene. The Negro River- Branco River Compartment configures a wedge structure with oblique movement in the northwest and east borders, and extensional in its central zone, with evolution initiated in the Upper Pleistocene extending to the Holocene. Recent activity of some of these faults is marked by seismic events with intensities that arrive 5,5 mB.
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Evolução estrutural da Bacia do Amazonas e sua relação com o embasamento
(Universidade Federal do Pará, 1991-02-19) WANDERLEY FILHO, Joaquim Ribeiro; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
This dissertation presents some aspects concer- ning the structural evolution of the Amazon basin and discusses the role of the Pre-Cambrian structures in the development of its architeture. The Pre-Cambrian record comprises strutures re- lated to two main thermal-tectonic events. The oldest one, Archean age, is responsible for the installation of granitic- greenstone terrains, and also the formation of shear belts composed of high grade metamorphic rocks. This event controlled the formation of the basic structural lineaments, trending Nw- SE, NE-SW and E-W. The second event, in the eastern Amazon re- gion, caused the development of NW-SE and WNW-ESE normal faults and NE-SW transfer faults related to an extensional NE-SW proterozoic axis giving rise to the formation of several basins of which, Cachimbo Graben is the most remarkable one. The structural evolution of the Amazon basin throug Phanerozoic time is strongly related to the geometry of the Pre-Cambrian structures. The installation of the Amazon basin is related to cyclic opening and closing of the Iapetus ocean during Paleozoic time. During this cycle, ancient weakness zones tren- ding NE-SW and NW-SE were reactivated as normal and transfer faults respectively. The movements associated to the transfer faults compartmentalized the basin into four distinct structural blocks, of which the compartmental zone of Purus (Purus Ar- ch) isa special example. The Purus arch separates the Amazon basin to the East from Western Solimões basin. Its origin is related to reactivation of normal faults of the Cachimbo Graben. The fragmentation of the Gondwana megacontinent, during mesozoic time, is witnessed in the Amazon basin by the following features: a) NE-SW and NNE-SSW normal faults; b) Nw- SE transfer faults; c) ENE-WSW wrench faults and d) igneous and sedimentary infill. During Cenozoic time, the Amazon basin and adjacent zones suffered effects of stress that generated essencially dextral whrench faults.
Acesso aberto (Open Access)
Evolução paleogeográfica, durante o cenozóico, da região de Bragança, NE do estado do Pará
(Universidade Federal do Pará, 2002-02-28) ALMEIDA, João Revelino Caldas de; BORGES, Mauricio da Silva; http://lattes.cnpq.br/1580207189205228; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
The main morphologic features of northeastemn Para State are strongiy related to middle Cenozoic extensional tectonics which is responsible by the Gondwana break up resulting in the formation of the Equatorial Atlantic Ocean and of the passive margin. The area is included in the Bragança-Viseu Basin, which evolved from the extensional tectonics incidence on the northeastem of the Para State since the Upper Jurassic. During the Miocene this area underwent transtensional tectonics that generated NW-SE normal faults and E-W and NE-SW dextral strike-slip faults. This tectonic event formed large subsided areas and corridors that facilitated transgression towards the continent since 150 km from the present coastline. This transgression originated the carbonatic sequence included in the Pirabas Formation, deposited in areas with drainage systems typical of subsided regions. Some areas remained emerged during the transgression. In the Bragança-Viseu Basin the sediments of Pirabas Formation are scarce, which suggest presence of a structural high blocking the transgression of the “Pirabas Sea”. The occurrence of limestone towards the south of Bragança suggest a cost line characterized by bay heads and promontories facing northwest. On the basis of geophysics interpretation, it was demonstrated in the Bragantina region the absence limestone towards the main depocenter of the Bragança-Viseu Basin. Therefore in this area, there are only occurrence of Precambrian rocks overlaid by Quaternary sediments (debris flows) included in the Post-Barreiras sequence.. The landscape has not change since Miocene - Pliocene, as can be demonstrated by the colinas relief. The geologic data suggest that the landscape evolution is controlled by structures related to the transtensional event.
Acesso aberto (Open Access)
Paleoambiente e proveniência da formação cabeças da bacia do Parnaíba: evidências da glaciação famenniana e implicações na potencialidade do reservatório
(Universidade Federal do Pará, 2014-06-10) BARBOSA, Roberto César de Mendonça; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
The hydrocarbon prospection history of the Paleozoic Parnaíba Basin, northeastern Brazil, has been unfavorable when compared to the putatively large reservoirs of the Pré-Sal of the Coastal basins and the onshore Solimões Basin. However, the discovery of natural gas in the Devonian-Eocarboniferous siliciclastic deposits of the Canindé Group which include Pimenteiras, Cabeças and Longá formations, has motivated new research to improve the paleoenvironmental and paleogeographic interpretations to understand the petroliferous system, the possible plays and the potenciality of the Upper Devonian Cabeças reservoir. Based-outcrop facies and stratigraphic analysis combined with detrital zircon geochronology allowed to interpret the paleoenvironment and the sedimentary provenance from Cabeças reservoir. Six facies association grouped in the succession with up to 60m thick, records the evolution of deltaic system influenced by glacial processes mainly in the top of the unit: 1) distal deltaic front, composed of massive mudstone and conglomerate, sandstone with massive bedding, even parallel lamination and sigmoidal cross-bedding; 2) proximal deltaic front, represented by sandstone with massive bedding, even parallel lamination and sigmoidal cross-bedding sandstone and massive conglomerate; 3) deltaic plain, consisting laminated mudstone, massive conglomerate, sandstone with massive bedding and trough cross-bedding; 4) glacial shoreface, composed by sandstone with rippled bedded and hummocky crossbedding; 5) subglacial deposits, which include massive diamictite, diamictite with sandstone pods and intraformational breccia; and 6) melt-out deltaic front, consisting of sandstone with massive bedding, even parallel lamination, climbing ripple-cross lamination and sigmoidal cross-bedding sandstone, as well as, deformed sandstone. In the Fammenian (374-359 Ma), a fluvial dominated deltaic front prograding to the NW (eastern border of the basin) and to the NE (western border of the basin) on a storm influenced platform (Pimenteiras Formation). In the eastern border of the basin, the paleocurrent pattern and the U-Pb zircon ages spectrum indicate that the Cabeças delta was fed by source lands located in the southeastern of the basin, probably in the Borborema Province. Mesoproterozoic (~ 1.039-1.009 Ma) and Neoproterozoic zircon ages are the most populous, differently of the grains with Archean (~ 2.508-2.678 Ma) and Paleoproterozoic (~ 2.054-1.992 Ma) ages. The youngest concordant zircon grain yielded a 206Pb/238age of 501.20 ± 6.35 Ma (95% concordant) indicating Cambrian source areas. The main sediments source of the Cabeças delta in the eastern border were provide of the Transversal Zone Domain and the Brasilian plutons of the crystalline basement found in the southeast of the Parnaíba Basin. Small contribution of sediments was derived from the Central Ceará and of the Western Rio Grande do Norte domains. In the Famennian, the migration of the Gondwana Supercontinent to the South Pole resulted in the implantation of the glacial conditions concomitant with the sea-level fall and exposure of the coastal region. The advance of the glaciers upon the basement crystalline rocks and deltaic deposits generated erosion, deposition of diamicton with exotic and faceted clasts, as well as, glaciotectonic strucutures such as foliation, boudins, folds, duplex, faults and fractures reflecting a brittle-ductile tangential shear. The unconsolidated and water saturated substrate had temperature slightly below to the melting point of ice (warm permafrost). Sporadic conglomerate lenses (dump structure) in shoreface deposits suggest an ice-rafted process due to icebergs during glacier retreat phase. The increase of the temperature in the Late Famennian reflects the dextral rotation of the Gondwana and South Pole migration from western portion of the South America and to the West Africa. The new paleogeographic configuration positioned the basin in subtropical latitudes initiating the glacier retreat and increase the influence of the isostatic rebound. The structures formed during pressure decrease were clastic sills and dykes, ball-and-pillow structures, beds disruption and intraformational breccia. Thrust faults associated with foliated diamictites in the western border of the basin suggest glaciers migrating to the N-NE. The continuity of the sea-level rise propitiates the implantation of melt-out deltaic system and, afterwards, a transgressive platform (Longá Formation). Diamictites interbedded with deltaic front deposits in the Upper Cabeças Formation correspond intervals with low pore volume and can represent secondary stratigraphic traps in the reservoir. The subglacial primary anisotropies were found in the both borders of the Parnaiba Basin, extend the glacial influence and opens a new perspective about the heterogeneity and effective potentiality of the Cabeças reservoir from the Mesodevonian- Eocarboniferous petroliferous system.
Acesso aberto (Open Access)
Processamento sísmico CMP e CRS de dados sintéticos acústicos e elásticos representativos das bacias paleozóicas da região Amazônica
(Universidade Federal do Pará, 2007) NAZARÉ, Cláudia Priscila Pereira; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
Among the several difficulties found in oil and gas exploration in the Amazon area, the existence of diabase sills, although important to the process of maturation of organic matter in all Brazilian Paleozoic basins, turns difficult the seismic exploration. The diabase disturbs the seismic signal, generating multiple reflections and scathering. With the purpose of understanding the seismic wave propagation and, mainly, the difficulties found by the seismic imaging methods in these complex geological settings, in this work it is presented the results of acoustic and elastic seismic modeling in synthetics models of the Amazonas and Solimões Basin, using finite-differences techniques. I present the seismic processing of this data set by the Common Midpoint (CMP) and Common Reflection Surface (CRS) stacking methods, and the pos-stack depth migration with split-step method. The results of stacking with CRS method show that both acoustic and elastic data has a better signal-noise ratio and lateral continuity of the reflectors when compared with the results of CMP stacking. The interpretative analyzes of stacked and migrated sections show that reflection events located on the top of models (in time until 0.7sec. and in depth until 1.200 meters) present apparently better resolution, but the botton of models has not been satisfactorily imaged by the occurrence of multiple reflections overlapped to primary reflections.
Acesso aberto (Open Access)
A sucessão siliciclástica-carbonática neocarbonífera da bacia do Amazonas, regiões de Monte Alegre e Itaituba (PA)
(Universidade Federal do Pará, 2010-03-14) LIMA, Hozerlan Pereira; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Neocaboniferous deposits of Morrowanian age in the Amazon Basin, northern Brazil, characterize the transition zone between Monte Alegre (siliciclastic rocks) and Itaituba (carbonate rocks) formations. The outcrop-based facies and stratigraphic analyses of this up to 40m thick succession, exposed in the Monte Alegre and Itaituba regions, State of Pará, allowed the recognition of five facies associations (FA), representative of a transitional desertic to coastal system, comprising: eolian dune/interdune (FA1), sandy sheet/wadi (FA2), lagoon/washover (FA3), beach/tidal flat (FA4) and lagoon/tidal delta (FA5). FA1 contains bimodal fine to medium-grained sandstone with medium-scale trough cross-stratification, subcritically climbing translatent stratification and inversely graded lamination (dune deposits). Massive fine sandstones with root marks suggest development of paleosols, while adhesion warts indicate eolian grain migration on wet interdune surface. FA2 comprises fine to medium-grained sandstone with even-parallel stratification and subcritically climbing translatent stratification, related to deflation, while fine to medium-grained sandstone with tangential and recumbent-folded cross-stratification and convolute bedding suggest migration of high-energy ephemeral rivers. FA3 with laminated mudstone and fine-grained sandstone with climbing-ripple cross lamination, hosting the ichnofossil Palaeophycus, suggests a low-energy environment of lagunar/washover type. FA4 is characterized by fine to medium-grained sandstones with planar and low-angle cross-stratification, interbedded with lenticular dolomite, locally truncated by fine to medium-grained sandstones. These facies correspond to the zone of swash and backwash on beach environment, locally cut by small channels, while the carbonate is interpreted as precipitated in ponds. FA 4 also comprehends mudstones with mudcracks and mud curls as well as small to medium-scale planar cross-bedded sandstones with mud drapes lining foresets and reactivation surfaces, suggesting migration of sandwaves in intertidal zones. FA5 is represented by dolomitized limestones (mudstones, wackestones, packstones and grainstones) containing vuggy and moldic porosities. Bioclasts include brachiopods, echinoderms, foraminifers, ostracodes, bryozoans, trilobites, mollusks and non-fragmented corals, and furthermore the trace fossil Thalassinoides. Additionally, this facies association comprises conglomerates with pebbles of dolomitized limestones, fine-grained sandstones with low-angle cross-stratification and reactivation surfaces, locally overlaid by fine sandstones with sigmoidal cross-stratification and climbing cross-lamination, which were interpreted as tidal inlet and tidal delta deposits. The facies/microfacies associations and paleontological data presented here point to a lagoonal environment, connected in part to a coastal desert zone, and characterize the transition between Monte Alegre and Itaituba formations. The abundance of fine sands with rounded grains in carbonate facies is consistent with siliciclastic influx from the desert adjacent to coastal environment. Warm tropical conditions for the environments can be inferred from the limestones and their diverse fauna as well as from the clay minerals, principally smectite. The interbedding of siliciclastic and carbonate rocks which characterizes the end of the deposition of the Monte Alegre Formation and the beginning of the sedimentation of the Itaituba Formation justifies a unique system representation for this interval.