Modelling oblique inversion of pre-existing grabens

2019 ◽  
Vol 487 (1) ◽  
pp. 263-290 ◽  
Author(s):  
Hongling Deng ◽  
Hemin A. Koyi ◽  
Jinjiang Zhang
Keyword(s):  
Western China ◽  
Normal Faults ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Analogue Models ◽  
Weak Zones ◽  
Different Parts ◽  
Extensional Structures

AbstractA series of analogue models were run to investigate oblique inversion of pre-existing grabens when overprinted by later shortening and the effect of these grabens on development of contractional structures. Obliquity angle (α) defining the initial trend of pre-existing grabens relative to the shortening direction, was systematically changed from 0°, 10°, 20°, 30°, 40°, 50°, 65° and 90°. Different structural styles are shown in different models and also in sections cutting across different parts of the models. Model results show that existence of multi-grabens enhances lateral discontinuity of overprinted thrusts in map view. With increasing the obliquity angle, more and longer lateral ramps developed sub-parallel to the graben trends. The pre-existing grabens were apparently rotated from their initial trends during shortening. Some of the normal faults bounding the grabens were partially inverted and resulted in bulging of the syn- and post-rift graben fill sediments. Most normal faults were displaced and rotated by thrusting, and provided relatively weak zones for propagation of thrusts. By comparing with observations from Qingxi graben in western China and from the SW Taiwan fold-and-thrust belt, where oblique inversion occurred, model results can be used to interpret unclear relationships between thrusts and pre-existing extensional structures during superimposed deformation.

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.

A SEISMIC STRUCTURAL OVERVIEW OF LIARD BASIN, NORTHEAST BRITISH COLUMBIA, CANADA

2021 ◽  
pp. 1-53
Author(s):  
Jennifer Leslie-Panek ◽  
Margot McMechan
Keyword(s):  
British Columbia ◽  
Rocky Mountain ◽  
Structural Features ◽  
Boundary Structure ◽  
Thrust Belt ◽  
Western Canada Sedimentary Basin ◽  
Large Structures ◽  
Fold And Thrust Belt ◽  
High Level ◽  
Extensional Structures

The Liard Basin is an important sub-basin of the Western Canada Sedimentary Basin located in Northeast British Columbia along the eastern margin of the Canadian Cordillera. It contains significant potential unconventional gas resources but is largely underrepresented in public literature. Using available-for-purchase 2D seismic data, a regional structural interpretation of the basin was completed providing the first seismically controlled, high-level overview of the structural features of the basin and its surrounding area. The shape of the Liard Basin largely reflects the orientation of older Paleozoic and Proterozoic extensional structures that localized structures formed during Cretaceous - Tertiary compressive deformation. The eastern boundary of the basin is marked by the well-documented Bovie Structure. The Liard Anticline and the Liard River Anticline found near 60o N latitude are the only large structures located within the Liard Basin proper. Inversion of the herein named Liard Basin Boundary Structure, a west-side-down fault zone of Early Paleozoic age, localized the northwest boundary of the basin with the Liard Fold and Thrust Belt. A triangle zone bounds the Rocky Mountain Foothills and the Liard Basin to the southwest. Reflectors in the Proterozoic strata below the Liard Basin were deformed by compressive and then extensional structures prior to the deposition of Paleozoic strata. Proterozoic strata are involved in all the major structures of the adjacent Liard Fold and Thrust Belt, the Rocky Mountain Foothills and the Bovie Structure. These structures controlled the location of the Liard Basin.

The Amer Belt: remnant of an Aphebian foreland fold and thrust belt

1986 ◽  
Vol 23 (12) ◽  
pp. 2012-2023 ◽  
Author(s):  
Judith G. Patterson
Keyword(s):  
Normal Faults ◽  
Lake Area ◽  
Thrust Belt ◽  
East Side ◽  
Progressive Deformation ◽  
The West ◽  
Polyphase Deformation ◽  
Thrust Belts ◽  
Fold And Thrust Belt ◽  
Stratigraphic Model

Aphebian supracrustal sequences occur as outliers throughout the northwestern portion of the Churchill Structural Province of the Canadian Shield. In the Amer Lake area, medium- to high-grade, polydeformed Archean rocks are unconformably overlain by the Amer supracrustal sequence, which comprises quartzite, carbonate, mafic volcanic, and meta-arkose and meta-pelitic units. This supracrustal sequence is interpreted as having been deposited under miogeoclinal conditions, transitional to exogeoclinal.The Amer sequence crops out in a broad, west-southwest-plunging synclinorium and contains evidence of polyphase deformation that includes the following: (1) Folds plunging gently to the west-southwest and west-southwest-striking thrust faults, transected by oblique tear faults. Thrust vergence is northerly to northwesterly, onto the Archean craton. Because of the orientation of the synclinorium, there is a down plunge view of the thrusts at the eastern end of the belt. (2) Younger, localized cross folds, probably representative of progressive deformation. (3) Late, northwest-trending normal faults, with east side down.The stratigraphic elements and family of structures in the Amer Belt are similar to those found in the foreland fold and thrust belts of major Phanerozoic and Proterozoic orogens. The Amer Belt is interpreted as being a remnant of a once extensive foreland fold and thrust belt.Some workers have considered the northwestern Churchill Structural Province a large cratonic foreland of the Trans-Hudson Orogen. However, remnants of a foreland fold and thrust belt, a major batholithic complex, and profound geophysical breaks interpreted as being possible sutures are incorporated into a new tectono-stratigraphic model that proposes that a cryptic Aphebian orogen exists in the northwestern Churchill Structural Province.

Mid-crustal detachment beneath southern Timor-Leste: seismic evidence for Australian basement in the Timor collision complex (and implications for prospectivity)

2021 ◽  
Author(s):  
T. R. Charlton
Keyword(s):  
Seismic Data ◽  
Passive Margin ◽  
Petroleum Exploration ◽  
Seismic Survey ◽  
Normal Faults ◽  
Thrust Belt ◽  
Collision Complex ◽  
Fold And Thrust Belt ◽  
Timor Leste ◽  
Seismic Sections

Seismic data originally acquired over SW Timor-Leste in 1994 shows two consistent seismic reflectors mappable across the study area. The shallower ‘red’ reflector (0.4-1s twt) deepens southward, although with a block-faulted morphology. The normal faults cutting the red marker tend to merge downward into the deeper ‘blue’ marker horizon (0.5-2.8s twt), which also deepens southward. Drilling intersections in the Matai petroleum exploration wells demonstrate that the red marker horizon corresponds to the top of metamorphic basement (Lolotoi Complex), while the blue marker horizon has the geometry of a mid-crustal extensional detachment. We see no indications for thrusting on the seismic sections below the red marker horizon, consistent with studies of the Lolotoi Complex at outcrop. However, surficial geology over much of the seismic survey area comprises a thin-skinned fold and thrust belt, established in 8 wells to overlie the Lolotoi Complex. We interpret the fold and thrust belt as the primary expression of Neogene arc-continent collisional orogeny, while the Lolotoi Complex represents Australian continental basement underthrust beneath the collision complex. In the seismic data the basal décollement to the thrust belt dips southward beneath the synorogenic Suai Basin on the south coast of Timor, and presumably continues southward beneath the offshore fold and thrust belt, linking into the northward-dipping décollement that emerges at the Timor Trough deformation front. The same seismic dataset has been interpreted by Bucknill et al. (2019) in terms of emplacement of an Asian allochthon on top of an imbricated Australian passive margin succession. These authors further interpreted a subthrust anticlinal exploration prospect beneath the allochthon, which Timor Resources plan to drill in 2021. This well (Lafaek) will have enormous significance not only commercially, but potentially also in resolving the long-standing allochthon controversy in Timor: i.e., does the Lolotoi Complex represent ‘Australian’ or ‘Asian’ basement?

Deep seismic reflection profiling across the central part of Northern Honshu arc, Japan

2020 ◽  
Author(s):  
Hiroshi Sato ◽  
Tatsuya Ishiyama ◽  
Hidehiko Shimizu ◽  
Naoko Kato ◽  
Masanao Shinohara ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Velocity Structure ◽  
Normal Faults ◽  
Rift Basin ◽  
Thrust Belt ◽  
Backarc Basin ◽  
Seismic Line ◽  
Fold And Thrust Belt ◽  
Axial Part ◽  
Reverse Faulting

<p>Northern Honshu, Japan, is a classic example of compressive island arc forming a trench-arc-backarc basin and was rifted away from the Asian continent in Miocene. The subduction of the Pacific plate generates megathrust earthquakes, such as the 2011 Tohoku-oki earthquake (M9) and an overriding plate deforms associated with M7-class reverse faulting. The amount of shortening is largest where along the Miocene failed rift basin, the Neogene post rift sediments form a fold-and-thrust belt. To understand the mechanisms of the deformation of overriding plate and generation of devastative earthquake, to reveal the detailed lithospheric structure of overriding plate is significant. In 2019, an onshore-offshore seismic reflection profiling was performed across the Japan trench to the axial part of the backarc basin. Here we focus on the crustal structure of the onshore section across the central part of northern Honshu.</p><p>The length of onshore seismic line is 160 km within the total 850-km-long seismic line. The air-gun shots in the forearc and backarc sides were recorded by onshore seismic line using 1616 fixed channels. Onshore seismic sources were four vibroseis trucks and dynamite shots. To obtain the deep crustal image, we used low-frequency signals. The produced sweep frequency was 3 to 40 Hz and seismic signals were recorded by 4.5 and 5 Hz geophones. Sets of 150 stationary vibroseis sweeps were performed at about 10 km interval along the seismic line. By conventional common-midpoint reflection methods and refraction tomography reveal the crustal structure down to 10 km. Together with the velocity structure obtained by earthquake tomography (Matsubara et al., 2019). Lithospheric structure is estimated by velocity structure obtained from active and passive sources, and geological data.</p><p>With seismic reflection profiles in the forearc (Miura et al., 2005) and backarc (No et al., 2014), the onshore seismic section portrays the first image of the seismic reflection profile across the Northern Honshu arc from the trench to the backarc basin. The basic structure of the over ridding plate were formed by the rifting of backarc opening stage. Most of the active faults inherited from the Miocene normal faults. The formation of backarc basins were achieved by the development of multi-rift systems. An axial part of failed rift within a continental crust is marked by a higher P-wave velocity lower crust, thick post-rift sediments underlaid by thick basalts. The failed rift is bounded by faults dipping to the outward of rift axis associated with mafic intrusion in a rift axis. The reverse faulting of the rift-bounding faults produced a fold-and-thrust belt in the post-rift Neogene basin fill. Judging from the tectonic geomorphological and geological features, these faulting and fault-related folding are active in late Quaternary. Detachment in this fold-and-thrust belt commonly accommodates in over pressured mudstone units in the rift basin. The major style of deformation of backarc is basement involved normal faults. Reactivation as reverse fault concentrated along the backarc continental failed rift.</p>

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>

Kinematics of a backthrust system in the Agrio fold and thrust belt, Argentina: Insights from structural analysis and analogue models

2020 ◽  
Vol 100 ◽  
pp. 102594
Author(s):  
Fernando Lebinson ◽  
Martín Turienzo ◽  
Natalia Sánchez ◽  
Ernesto Cristallini ◽  
Vanesa Araujo ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Analogue Models

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.

Sign in / Sign up

Export Citation Format

Share Document