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.

scholarly journals Seismic Activity of the Manisa Fault Zone in Western Turkey Constrained by Cosmogenic 36Cl Dating

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 451
Author(s):  
Nasim Mozafari ◽  
Çağlar Özkaymak ◽  
Dmitry Tikhomirov ◽  
Susan Ivy-Ochs ◽  
Vasily Alfimov ◽  
...  
Keyword(s):  
Fault Zone ◽  
Normal Fault ◽  
Vertical Displacement ◽  
Historical Records ◽  
Western Turkey ◽  
Slip Rates ◽  
Vertical Displacements ◽  
Surface Ruptures ◽  
Fault Scarps ◽  
Calculated Average

This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two surface ruptures at 3.5 ± 0.9 ka and 2.0 ± 0.5 ka, with vertical displacements of 3.3 ± 0.5 m and 3.6 ± 0.5 m, respectively. An event at 6.5 ± 1.6 ka with a vertical displacement of 2.7 ± 0.4 m was reconstructed on the Mugırtepe fault. We attribute these earthquakes to the recurring MFZ ruptures, when also the investigated faults slipped. We calculated average slip rates of 1.9 and 0.3 mm yr−1 for the Manastır and Mugırtepe faults, respectively.

scholarly journals Quaternary slip-rates of the Kazerun and the Main Recent Faults: active strike-slip partitioning in the Zagros fold-and-thrust belt

2009 ◽  
Vol 178 (1) ◽  
pp. 524-540 ◽  
Author(s):  
Christine Authemayou ◽  
Olivier Bellier ◽  
Dominique Chardon ◽  
Lucilla Benedetti ◽  
Zaman Malekzade ◽  
...  
Keyword(s):  
Strike Slip ◽  
Thrust Belt ◽  
Slip Rates ◽  
Fold And Thrust Belt ◽  
Slip Partitioning

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.

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.

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.

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.

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