scholarly journals TECTÔNICA DA FAIXA DE DOBRAMENTOS BRASÍLIA – SETORES SETENTRIONAL E MERIDIONAL.

2012 ◽  
Author(s):  
Alexandre Uhlein ◽  
Marco Antônio Fonseca ◽  
Hildor José Seer ◽  
Marcel Auguste Dardenne
Keyword(s):  
Ductile Deformation ◽  
Low Grade ◽  
Thrust Belt ◽  
Fold Belt ◽  
Central Brazil ◽  
Structural Style ◽  
Deformational History ◽  
Fold And Thrust Belt ◽  
Lithostratigraphic Units ◽  
External Domain

A Faixa neoproterozóica de dobramentos e empurrões Brasília é uma das unidades tectônicas do Brasil Central. Uma análiseestrutural e tectônica da Faixa Brasília é aqui apresentada, com dois domínios estruturais: (1) interno, com unidades alóctones, foliação Spsubhorizontal ou suavemente dobrada e médio a alto grau de metamorfismo. (2) domínio externo, com estrutura de dobras e empurrões,predomínio de foliação Sp e médio a baixo grau de metamorfismo. A leste da Faixa Brasília ocorre o domínio cratônico (Craton do São Francisco), com unidades autóctones, suavemente dobradas. A vergência das dobras e empurrões é, geralmente, para o Cráton do SãoFrancisco. O encurtamento na cobertura é balanceado por zonas de cisalhamento, amplas dobras, falhas de empurrão e inversas e falhastranscorrentes. O estilo da deformação varia com o nível crustal. Assim, no domínio externo da faixa, predomina um estilo thin-skinned,enquanto que no domínio interno, aparecem zonas de deformação dúcteis mais intensas e largas, com metamorfismo mais alto (estilothick-skinned). O segmento sul da Faixa Brasília está mais deformado e provavelmente representa o resultado de uma colisão diacrônica,mais antiga, em relação ao setor setentrional. A mega inflexão dos Pirineus e a zona de superposição pode ser o resultado da interferênciaentre duas faixas neoproterozóicas distintas, com transporte tectônico local de Norte para o Sul.Palavras chave: Faixa móvel neoproterozóica Brasília; estilo nstrutural; evolução geodinâmica. ABSTRACTTECTONICS OF THE BRASÍLIA FOLD BELT: THE NORTHERN AND SOUTHERN PARTS - The Neoproterozoic (ca. 650-580) Ma Brasíliafold-and-thrust-belt is a major tectonic unit in Central Brazil and can be divided into two structural domains (internal and external). In theinternal domain, most surface rocks consist of allochthonous units in a higher metamorphic grade displaying low dipping cleavage,asymmetrical folds and thrusts with significant stratigraphic repetition. The external domain is a typical foreland fold-and-thrust belt wheremedium to low grade metamorphic rocks prevail and present steeply dipping cleavage Sp. Towards the cratonic area (cratonic domain),most lithostratigraphic units are authoctonous with vertical open folds and slaty cleavage. The general vergence of folds and thrust faults inboth domains is towards the east (São Francisco Craton). Shortening of cover across the fold belt is almost always balanced by coverbasementdetachments, fold-and-thrust structures and also by NE or NW trending wrench faults. The style of deformation variesconsiderably across strike due to crustal level. Typical thin-skinned fault-fold morphology in external domain gives rise downwards to morepervasive wide zones of ductile deformation at high metamorphic grades (thick-skinned structures) in the internal domain. The Southernpart of the Brasilia belt has a more complex deformational history than the northern one. This is probably due to structural overprintcaused by a diachronic collision. The Pirineus Inflection, where local vergence is towards the South, may represent the interference zonebetween the the two parts.Keywords: Neoproterozoic Brasília fold-and-thrust belt; structural style; Geodinamic evolution.

The 2018 M w 7.5 Highlands Earthquake in Papua New Guinea: Implications for Structural Style in an Active Fold and Thrust Belt

Tectonics ◽  
2021 ◽  
Vol 40 (4) ◽  
Author(s):  
Luke Mahoney ◽  
Richard Stanaway ◽  
Sandra McLaren ◽  
Kevin Hill ◽  
Eric Bergman
Keyword(s):  
Papua New Guinea ◽  
New Guinea ◽  
Thrust Belt ◽  
Structural Style ◽  
Fold And Thrust Belt

scholarly journals Combined Multiple Attenuation Methods and Geological Interpretation : Seram Sea Case Study 2D Marine Seismic Data

2019 ◽  
Vol 34 (1) ◽  
Author(s):  
Tumpal Bernhard Nainggolan ◽  
Said Muhammad Rasidin ◽  
Imam Setiadi
Keyword(s):  
Satisfactory Result ◽  
Radon Transform ◽  
Seismic Data ◽  
Thrust Belt ◽  
Geological Interpretation ◽  
Structural Style ◽  
Predictive Deconvolution ◽  
Fold And Thrust Belt ◽  
Short Period ◽  
Marine Seismic

Multiple often and always appear in marine seismic data due to very high acoustic impedance contrasts. These events have undergone more than one reflection. This causes the signal to arrive back at the receiver at an erroneous time, which, in turn, causes false results and can result in data misinterpretation. Several types of multiple suppression have been studied in literature. Methods that attenuate multiples can be classified into three broad categories: deconvolution methods; filtering methods and wavefield prediction subtraction methods. The study area is situated on Seram Sea in between 131°15’E – 132°45’E and 3°0’S – 4°0’S, Seram Trough which is located beneath Seram Sea at northern part of the Banda-Arc – Australian collision zone and currently the site of contraction between Bird’s Head and Seram. This research uses predictive deconvolution and FK-filter to attenuate short period multiple from their move out, then continued by SRME method to predict multiple that cannot be attenuated from previous method, then followed by Radon transform to attenuate multiple that still left and cannot be attenuated by SRME method. The result of each method then compared to each other to see how well multiple attenuated. Predictive deconvolution and F-K filter could not give satisfactory result especially complex area where multiple in dipping event is not periodic, SRME method successfully attenuate multiple especially in near offset multiple without need subsurface information, while SRME method fails to attenuate long offset multiple, combination of SRME method and Radon transform can give satisfactory result with careful selection of the Radon transform parameters because it can obscure some primary reflectors. Based on geological interpretation, Seram Trough is built by dominant structural style of deposited fold and thrust belt. The deposited fold and thrust belt has a complexly fault geometry from western zone until eastern of seismic line.

scholarly journals Mechanical Influence of Inherited Folds in Thrust Development: A Case Study from the Variscan Fold-and-Thrust Belt in SW Sardinia (Italy)

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 276
Author(s):  
Fabrizio Cocco ◽  
Antonio Funedda
Keyword(s):  
Ductile Deformation ◽  
Mechanical Anisotropy ◽  
Thrust Belt ◽  
External Zone ◽  
Layer Cake ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Vertical Variations ◽  
Stratigraphic Succession

Fold-and-thrust belts have a high variability of structural styles, whose investigation provides continuous updates of the predictive models that try to better approximate the geometries recognized in the field. The majority of studies are focused on the geometry and development of folds and thrust surfaces and the amount of displacement, taking into account the role played by the involved stratigraphic succession assumed as a layer cake. We present a case study from the external zone of the Variscan fold-and-thrust belt in SW Sardinia, where it was possible to investigate the lateral and vertical variations of the mechanical properties of the involved succession, how they related to previous folding, control thrust geometry, and kinematics. In this case, the superposition of two fold systems acted as a buttress that induced extensive back-thrusting. We found that there is a close connection between the attitude of the bedding and the geometry of back thrust surfaces, shear strength during thrust propagation, and variation in the shortening amount, depending on which part of the folds were cut across. The folding-related mechanical anisotropy also seems to have induced a ductile deformation in the footwall of back-thrusts. Although the case study considers the development of back-thrust, the relations between thrust and not-layer cake geometries could also be applied to fore-thrust development.

scholarly journals Mechanisms of basin contraction and reactivation in the basement-involved Malargüe fold-and-thrust belt, Central Andes (34–36°S)

2016 ◽  
Vol 153 (5-6) ◽  
pp. 926-944 ◽  
Author(s):  
M. BRANELLEC ◽  
B. NIVIÈRE ◽  
J.-P. CALLOT ◽  
J.-C. RINGENBACH
Keyword(s):  
Rio Grande Valley ◽  
Central Andes ◽  
Thrust Belt ◽  
Fold Belt ◽  
Active Deformation ◽  
Frontal Part ◽  
Fold And Thrust Belt ◽  
Morphologic Response ◽  
Eastern Border ◽  
San Rafael

AbstractWe have conducted a structural study of both the basement-involved Malargüe fold-and-thrust belt (MFTB) and the active San Rafael Block (SRB), which are located in the Central Andes at latitude 34–36°S. Based on several field examples located both in the inner and frontal part of belt and from the distal foreland zone, we focus on the relationships between basement and cover deformation with respect to the known palaeogeography and structural inheritance. In several zones, we point out similarities in the structural and sedimentary responses to Andean shortening. The recent morphologic response has also been investigated through the analysis of active deformation along the eastern border of the SRB. We show that these structural and sedimentary processes are continuous in time and space since they can be applied in the various parts of the fold belt and also at different stages of fold-and-thrust-belt building as well. Finally, we propose the illustration of those mechanisms by complete cross-section along the Rio Grande valley and a possible kinematic scenario of deformation propagation.

Bivergent extension in the overriding plate above a slab tear (Dodecanese, Greece)

2020 ◽  
Author(s):  
Bernhard Grasemann ◽  
David A. Schneider ◽  
Konstantinos Soukis ◽  
Vincent Roche
Keyword(s):  
Eastern Mediterranean ◽  
Hanging Wall ◽  
Finite Extension ◽  
Normal Fault ◽  
Vertical Axis ◽  
Normal Faults ◽  
Low Grade ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Variscan Basement

<p><span lang="EN-US">Tearing in the Hellenic slab below the transition between the Aegean and Anatolian plate is considered to have significantly affected Miocene tectonic and magmatic evolution of the eastern Mediterranean by causing a toroidal flow of asthenosphere and a lateral gradient of extension in the upper plate. Some studies suggest that this lateral gradient is accommodated by a distributed sinistral lithospheric-scale shear zone whereas other studies favor a localized NE-SW striking transfer zone. Recent studies in the northern Dodecanese demonstrate that the transition zone between the Aegean and Anatolian plate is characterized by Miocene extension with a constant NNE-SSW sense of shear accommodating the difference in finite extension rates in the middle-lower crust. Neither localized or distributed strike-slip faults nor rotation of blocks about a vertical axis have been observed.</span></p> <p><span lang="EN-US">In this work we focus on the geology Kalymnos located in the central Dodecanese. Based on our new geological map, three major tectonic units can be distinguished: (i) Low-grade, fossil-rich late Paleozoic marbles, which have been deformed into S-vergent folds and out-of-sequence thrusts. This fold-and-thrust belt is sealed by an up to 200 m thick wildflysch-type deposit consisting of low-grade metamorphic radiolarites and conglomerates with tens of meters-scale marbles and ultramafics blocks. (ii) Above this unit, amphibolite facies schists, quartzites and amphibolites are tectonically juxtaposed along a several meter-thick thrust fault with low-grade ultramylonites and cohesive ultracataclasites/pseudotachylites with top-to-N kinematics. (iii) At highest structural levels, a major cataclastic low-angle normal fault zone localized in Verrucano-type violet slates separates Mesozoic unmetamorphosed limestones in the hanging wall. The sense of shear of the normal fault is top-to-SSW. All units are cut by brittle high-angle normal faults shaping the geomorphology of Kalymnos, which is characterized by three major NNW-SSE trending graben systems.</span></p> <p><span lang="EN-US">New white mica Ar-Ar ages suggests that the middle units represent relics of a Variscan basement, which was thrusted on top of a fold-and-thrust belt during an Eo-Cimmerian event. Zircon (U-Th)/He ages from the Variscan basement are c. 28 Ma, indicating that the lower units were exhumed below the Mesozoic carbonates during the Oligocene-Miocene. Since Miocene extension in the northern Dodecanese records top-to-NNE kinematics, we suggest that back-arc extension in the whole Aegean realm and transition to the Anatolian plate is bivergent, and tearing in the Hellenic slab did not significantly affected the extension pattern in the upper crust.</span></p>

Sign in / Sign up

Export Citation Format

Share Document