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>

scholarly journals The role of basement-involved normal faults in the recent tectonics of western Taiwan

2016 ◽  
Vol 153 (5-6) ◽  
pp. 1166-1191 ◽  
Author(s):  
KENN-MING YANG ◽  
RUEY-JUIN RAU ◽  
HAO-YUN CHANG ◽  
CHING-YUN HSIEH ◽  
HSIN-HSIU TING ◽  
...  
Keyword(s):  
Active Faults ◽  
Foreland Basin ◽  
Normal Fault ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Normal Faults ◽  
Thrust Belt ◽  
Structural Style ◽  
Fold And Thrust Belt ◽  
Recent Tectonics

AbstractIn the foreland area of western Taiwan, some of the pre-orogenic basement-involved normal faults were reactivated during the subsequent compressional tectonics. The main purpose of this paper is to investigate the role played by the pre-existing normal faults in the recent tectonics of western Taiwan. In NW Taiwan, reactivated normal faults with a strike-slip component have developed by linkage of reactivated single pre-existing normal faults in the foreland basin and acted as transverse structures for low-angle thrusts in the outer fold-and-thrust belt. In the later stage of their development, the transverse structures were thrusted and appear underneath the low-angle thrusts or became tear faults in the inner fold-and-thrust belt. In SW Taiwan, where the foreland basin is lacking normal fault reactivation, the pre-existing normal faults passively acted as ramp for the low-angle thrusts in the inner fold-and-thrust belt. Some of the active faults in western Taiwan may also be related to reactivated normal faults with right-lateral slip component. Some main earthquake shocks related to either strike-slip or thrust fault plane solution occurred on reactivated normal faults, implying a relationship between the pre-existing normal fault and the triggering of the recent major earthquakes. Along-strike contrast in structural style of normal fault reactivation gives rise to different characteristics of the deformation front for different parts of the foreland area in western Taiwan. Variations in the degree of normal fault reactivation also provide some insights into the way the crust embedding the pre-existing normal faults deformed in response to orogenic contraction.

Kinematic evolution of a fold-and-thrust belt developed during basin inversion: the Mesozoic Maestrat basin, E Iberian Chain

2016 ◽  
Vol 155 (3) ◽  
pp. 630-640 ◽  
Author(s):  
MARINA NEBOT ◽  
JOAN GUIMERÀ
Keyword(s):  
Hanging Wall ◽  
Evolutionary Model ◽  
Normal Fault ◽  
Fault System ◽  
Rift System ◽  
Thrust Belt ◽  
Northern Margin ◽  
Kinematic Evolution ◽  
Fold And Thrust Belt ◽  
Maestrat Basin

AbstractThe Maestrat basin was one of the most subsident basins of the Mesozoic Iberian Rift system, developed by a normal fault system which divided it into sub-basins. Its Cenozoic inversion generated the N-verging Portalrubio–Vandellòs fold-and-thrust belt in its northern margin, detached in the Triassic evaporites. In the hinterland, a 40 km wide uplifted area, in the N–S direction, developed, bounded to the N by the E–W-trending, N-verging Calders monocline. This monocline is interpreted as a fault-bend fold over the ramp to flat transition of the E–W-trending, N-verging Maestrat Basement Thrust, and also indicates the transition from a thick-skinned (S) to a thin-skinned (N) style of deformation. This paper presents a kinematic evolutionary model for the northern margin of the basin and a reconstruction of the Maestrat Basement Thrust geometry, generated by the inversion of the Mesozoic normal fault system. It contains a low-dip ramp (9°) extended southwards more than 40 km, attaining a depth of 7.5 km. As this thrust reached the Mesozoic cover to the foreland, it propagated across the Middle Muschelkalk evaporitic detachment, generating a nearly horizontal thrust which transported northwards the supra-salt cover, and the normal fault segments within it, for c. 11–13 km. The displacement of the basement in the hanging-wall of the low-dip basement ramp generated the 40 km wide uplifted area, while the superficial shortening was accumulated in the northern margin of the basin – which contains the thinnest Mesozoic cover – developing the Portalrubio–Vandellòs fold-and-thrust belt.

Basement-involved inversion at the Appalachian structural front, western Newfoundland: an interpretation of seismic reflection data with implications for petroleum prospectivity

2004 ◽  
Vol 52 (3) ◽  
pp. 215-233 ◽  
Author(s):  
Glen S. Stockmal ◽  
Art Slingsby ◽  
John W.F. Waldron
Keyword(s):  
Seismic Reflection ◽  
Hanging Wall ◽  
Normal Fault ◽  
Hydrocarbon Exploration ◽  
Normal Faults ◽  
Apparent Magnitude ◽  
Seismic Reflection Data ◽  
The Public ◽  
Reflection Data ◽  
New Interpretation

Abstract Recent hydrocarbon exploration in western Newfoundland has resulted in six new wells in the Port au Port Peninsula area. Port au Port No.1, drilled in 1994/95, penetrated the Cambro-Ordovician platform and underlying Grenville basement in the hanging wall of the southeast-dipping Round Head Thrust, terminated in the platform succession in the footwall of this basement-involved inversion structure, and discovered the Garden Hill petroleum pool. The most recent well, Shoal Point K-39, was drilled in 1999 to test a model in which the Round Head Thrust loses reverse displacement to the northeast, eventually becoming a normal fault. This model hinged on an interpretation of a seismic reflection survey acquired in 1996 in Port au Port Bay. This survey is now in the public domain. In our interpretation of these data, the Round Head Thrust is associated with another basement-involved feature, the northwest-dipping Piccadilly Bay Fault, which is mapped on Port au Port Peninsula. Active as normal faults in the Taconian foreland, both these faults were later inverted during Acadian orogenesis. The present reverse offset on the Piccadilly Bay Fault was previously interpreted as normal offset on the southeast-dipping Round Head Thrust. Our new interpretation is consistent with mapping on Port au Port Peninsula and north of Stephenville, where all basement-involved faults are inverted and display reverse senses of motion. It also explains spatially restricted, enigmatic reflections adjacent to the faults as carbonate conglomerates of the Cape Cormorant Formation or Daniel’s Harbour Member, units associated with inverted thick-skinned faults. The K-39 well, which targeted the footwall of the Round Head Thrust, actually penetrated the hanging wall of the Piccadilly Bay Fault. This distinction is important because the reservoir model invoked for this play involved preferential karstification and subsequent dolomitization in the footwalls of inverted thick-skinned faults. The apparent magnitude of structural inversion across the Piccadilly Bay Fault suggests other possible structural plays to the northeast of K-39.

scholarly journals Hurricane Fault

Geosites ◽  
2019 ◽  
Vol 1 ◽  
pp. 1-12
Author(s):  
Robert Biek
Keyword(s):  
East Coast ◽  
Hanging Wall ◽  
Grand Canyon ◽  
Normal Fault ◽  
Local Area ◽  
Fault Scarp ◽  
Normal Faults ◽  
Slip Rates ◽  
The Town

The Hurricane fault is the big earthquake fault in southwestern Utah. It stretches at least 155 miles (250 km) from south of the Grand Canyon northward to Cedar City and is capable of producing damaging earthquakes of about magnitude 7.0. The Hurricane fault is a “normal” fault, a type of fault that forms during extension of the earth’s crust, where one side of the fault moves down relative to the other side. In this case, the down-dropped side (the hanging wall) is west of the fault; the upthrown side (the footwall) lies to the east. Like most long normal faults, the Hurricane fault is composed of discrete segments that tend to rupture independently (figure 1). The fault lies at or near the base of the Hurricane Cliffs, which form an impressive, little-eroded fault scarp several hundred feet high. Conspicuous, west-tilted, faulted slivers of mostly Triassic and Jurassic red beds are locally exposed at the base of the cliffs, and contrast strongly with gray Permian carbonates exposed in the cliffs themselves. Several Pleistocene basaltic lava flows flowed across and are now offset by the fault zone, dramatically recording long-term slip rates. Should you make the mistake of pronouncing the name “Hurricane” as one would when describing a mighty storm on the East Coast, you should stand to be corrected, for locals pronounce it as “Hurricun” even though pioneers named the town after ferocious winds common to the local area.

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.

scholarly journals Onset of Aegean-style extensional deformation in the contractional southern Dinarides documented by incipient normal fault scarps in Montenegro

2021 ◽  
Author(s):  
Peter Biermanns ◽  
Benjamin Schmitz ◽  
Silke Mechernich ◽  
Christopher Weismüller ◽  
Kujtim Onuzi ◽  
...  
Keyword(s):  
Normal Fault ◽  
Thrust Belt ◽  
Slip Rates ◽  
Fold And Thrust Belt ◽  
Different Color ◽  
Fault Scarps ◽  
The Last Glacial Maximum ◽  
Lichen Growth ◽  
Extensional Structures ◽  
The Last Glacial

Abstract. We describe two previously unreported, 5–7 km long normal fault scarps (NFS) occurring atop fault-related anticlines in the coastal ranges of the Dinarides fold-and-thrust belt in southern Montenegro, a region under predominant contraction. Both NFS show well-exposed, 6–9 m high, striated and locally polished fault surfaces in limestones, documenting active faulting during the Holocene. Sharply delimited ribbons on free rock faces show different color, varying karstification and lichen growth and suggest stepwise footwall exhumation, typical of repeated normal faulting earthquake events. Displacements, surface rupture lengths and geometries of the outcropping fault planes imply paleoearthquakes with Mw ≈ 6 ± 0.5 and slip rates of c. 0.3–0.5 mm/yr since the Last Glacial Maximum. Slip rates based on cosmogenic 36Cl data from the scarps are significantly higher: modeling suggests 1.5 ± 0.1 mm/yr and 6–15 cm slip every c. 35–100 yrs, commencing c. 6 kyr ago. The total throw on both NFS – although poorly constrained – is estimated to max. 200 m, and offsets the basal thrust of a regionally important tectonic unit. Both NFS are incipient extensional structures that postdate growth of the fault-related anticlines on top of which they occur. Interestingly, the position of the extensional features agrees with recent geodetic data, suggesting that our study area is located exactly at the transition from NE-SW-directed shortening in the northwest to NE-SW-directed extension to the southeast. While the contraction reflects ongoing Adria-Europe convergence taken up along the frontal portions of the Dinarides, the incipient extensional structures might be induced by rollback of the Hellenic slab in the SE, whose effects on the upper plate appear to be migrating along-strike the Hellenides towards the northwest. The newly found NFS provide evidence for a kinematic change of a thrust belt segment over time. Alternatively, the NFS might be regarded as second-order features accommodating changes in dip of the underlying first-order thrust faults to which they are tied genetically.

Structure and genesis of the Boulder-Weld allochthon, Denver Basin, Colorado - Gravity slide or Laramide thrust sheet?

2020 ◽  
Vol 57 (3) ◽  
pp. 271-304
Author(s):  
Edward J. Sterne
Keyword(s):  
Hanging Wall ◽  
Normal Fault ◽  
Normal Faults ◽  
Front Range ◽  
Denver Basin ◽  
Thrust Sheet ◽  
Pierre Shale ◽  
Transport Direction ◽  
Tear Fault ◽  
Gravity Slide

This study was undertaken to determine the structure and genesis of the Boulder-Weld allochthon (BWA), the 216 mi2 (559 km2) remnant of a once larger feature, that moved east from the flank of the Front Range into the western part of the Denver Basin. This review of surface and subsurface data revealed new aspects of the BWA, especially in its western part. There, the decollement of the BWA ramps 900 feet up-section to the east from a near bedding-parallel detachment low in the upper transition member of the Pierre Shale to a bedding-parallel detachment near the base of the Fox Hills Formation. Repeated sections found in wells east of the decollement ramp demonstrate up to two miles of translation in the system. Secondary faults in the hanging wall of the allochthon include antithetic thrusts bounding pop-up structures and occasional normal faults that almost exclusively overprint the decollement ramp. The hanging wall is also cut by a postulated tear fault separating areas exhibiting different amounts of translation. The western, trailing edge of the decollement shows attenuation in its hanging wall that increases to the west. This part of the decollement either represents a very low-angle breakaway normal fault or a thrust fault cutting slightly down-section in the direction of transport. Past studies perceived a southeast transport direction for the BWA in contrast to the northeast slip directions on nearby Laramide thrusts, a difference used to interpret the allochthon as a gravity slide. However, similar east-west oriented slickenlines on thrusts across the western part of the allochthon and into the neighboring Front Range leave open the possibility the BWA originated as a Laramide thrust sheet. Furthermore, both the BWA and Laramide thrusts in the neighboring Front Range utilized detachments near the top of the Pierre Shale, suggesting a possible common genesis. Given the available data, both the gravity slide and Laramide thrust models provide viable explanations for the BWA.

Thermochronological constraints on the Eocene exhumation of the Grand Forks complex, British Columbia, based on 40Ar/39Ar and apatite fission track geochronology

2013 ◽  
Vol 50 (5) ◽  
pp. 576-598 ◽  
Author(s):  
J.F. Cubley ◽  
D.R.M. Pattison ◽  
D.A. Archibald ◽  
M. Jolivet
Keyword(s):  
Fission Track ◽  
Hanging Wall ◽  
Closure Temperature ◽  
Normal Faults ◽  
Low Grade ◽  
Early Eocene ◽  
Apatite Fission Track ◽  
Slow Cooling ◽  
Rapid Phase ◽  
Grand Forks

The Grand Forks complex (GFC) is a metamorphic core complex within the composite Shuswap complex in the southern Omineca belt of the Canadian Cordillera. It is juxtaposed against the surrounding low-grade rocks of the pericratonic Quesnel terrane by outward-dipping Eocene normal faults. The GFC attained peak metamorphic conditions of 750–800 °C and 5.5–6.0 kbar (1 kbar = 100 MPa) in the late Paleocene to early Eocene, followed by ∼2.5 kbar of near-isothermal decompression at upper-amphibolite to granulite facies conditions (∼725–750 °C) in the early Eocene. Subsequent low-temperature greenschist-facies exhumation (∼0.7–1.5 kbar) was accommodated by the brittle–ductile Kettle River normal fault (KRF) on the east flank of the complex and the Granby fault (GF) on the west flank. This study presents 16 new 40Ar/39Ar hornblende and biotite dates from the GFC and low-grade rocks in the hanging walls to the KRF and GF. Cooling of the GFC through the closure temperature of hornblende (∼ 530 °C) is constrained to the interval between ∼54 and 51.4 ± 0.5 Ma, whereas cooling through the closure temperature of biotite (∼280 °C) occurred at 51.4 ± 0.2 Ma. In the hanging wall of the KRF, cooling through the closure temperature of hornblende and biotite occurred nearly coevally at 51.7 ± 0.6 Ma and 51.0 ± 1.0 Ma, respectively. Five apatite fission track dates (closure temperature ∼110 °C) from the GFC and adjacent hanging walls are indistinguishable within error, yielding an average age of 34.6 ± 2.0 Ma. The lack of difference in biotite and apatite ages between the GFC and the low-grade hanging wall rocks against which it is juxtaposed suggests no significant movement on the KRF and GF after ca. 51 Ma. Results from this study and a previous study on U–Pb dating of the GFC document rapid cooling of the GFC in excess of 200 °C/Ma in a 4 Ma interval between 55 and 51 Ma (Eocene). This rapid phase of exhumation of the GFC was followed by 15 Ma of slow cooling (∼10 °C/Ma) of the joined GFC and hanging wall between ∼280 °C (biotite closure) and ∼110 °C (apatite closure).

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