Sinistral Strike-slip Displacement Research Articles

Cenozoic double-layered structure in the western Qaidam Basin, northern Tibetan Plateau, China

• Cenozoic double-layered structure was identified in the western Qaidam Basin. • The Qaidam Basin suffered much stronger shortening deformation in west than east. • The double-layered structure in the western Qaidam Basin was initiated at Pliocene . • Double-layered structure was due to far-field effect of the India-Asia collision. The Qaidam Basin in the northern Tibetan Plateau lies above over 3000 m elevation above sea level, being the inland terrestrial basin with the highest altitude in the world. This basin is surrounded by the Eastern Kunlun, Altyn and Qilian Mountains, and represents a key area to decipher the tectonic and kinematic evolution of the northern Tibetan Plateau during Cenozoic times. The Cenozoic deformation of the Qaidam Basin is synchronous with the uplift of the northern Tibetan Plateau. The structural coupling between Cenozoic shallow and deep deformation systems in the Qaidam Basin is complicated and poorly understood, because of the lack of studies of the deformation at the depth. Based on the detailed structural analysis of the Honggouzi and Nanyishan anticlines in the western Qaidam Basin, we found that the fault-propagation fold was usually developed in the shallow part and “Y” shaped thrust faults occur at both sides of the anticlinal core, while fault-bend folds developed above the bottom detachment fault in the deep, which together constitute the Cenozoic double-layered structure (DLS). The DLS is relatively well developed in the northwest and gradually disappears to the southeast in the Qaidam Basin, indicating that the deformation and shortening in the western Qaidam Basin is much stronger than that in the eastern Qaidam Basin. The initial formation time of the DLS started from Pliocene (Shizigou Fm.) and continue to present, which supports that the Qaidam Basin was a “plate-shape-like” compressive flexing basin without obvious deformation during Eocene to Pliocene. The formation of the DLS in the western Qaidam Basin was due to the continuing N/NNE-directed compression in the southwest and the large-scale sinistral strike-slip displacement along the Altyn Tagh fault in the northwest related to the far-field stress effect of the India-Asia collision.

Structural–Kinematic Parageneses and Dynamic Evolution Model of the Baltic–Mezen Shear Zone in the Phanerozoic, the Northwestern Part of the East European Platform

The tectonic features of the Baltic–Mezen shear zone that developed along the border of the Fennoscandian Shield and the Russian Plate in the north of the East European Platform are considered. It is established that tectonic evolution of the considered zone was associated with strike-slip displacements in the basement rocks, which occurred and were dispersed in cover deposits in the form of low-amplitude faults and diagonal fold-and-thrust systems associated with sublayer detachments. The dynamic relationship of the geological–structural and geomorphic anomalies of the Baltic–Mezen zone with segments of bending of its mainline and virgation, as well as with the nodes of intersection of the main shear zone with transverse faults, is noted. Based on a study of structural and kinematic parageneses, it has been established that the Baltic–Mezen shear zone in the Phanerozoic developed mainly under dextral strike-slip displacement and transpression conditions during eight activation phases of the Caledonian, Hercynian, and recent deformation stages. Periodically there was a change in deformation regimes and kinematic inversions, and a shear zone evolved in conditions of transtension and sinistral strike-slip displacements. The kinematics of the Baltic–Mezen shear zone is consistent with the general dynamic patterns of the evolution of the East European Platform, in particular, with the formation of collision structures of the Scandinavian Caledonides, with extensive Late Devonian tectonic–magmatic events and features of the recent development of the Euro–Arctic region.

Sinistral strike slip of the Zhangjiakou-Penglai Fault and its control on hydrocarbon accumulation in the northeast of Shaleitian Bulge, Bohai Bay Basin, East China

Abstract The structural style, fault activity, strike-slip displacement, and the formation mechanism and hydrocarbon migration and accumulation in the center tectonic zone in the northeast Shaleitian Bulge of Zhangjiakou-Penglai Fault Zone were studied by seismic attribute analysis, structural geometric analysis, fault activity analysis, structure evolution history and simulation of hydrocarbon migration, based on 3-D seismic and drilling data. The main results are as follows: (1) The study area is a superimposed tectonic zone, which experienced early (Paleocene and Eocene) extension and late (Oligocene and Pliocene-Quaternary) strike-slip and pull-apart. (2) The sinistral strike slip of the northeast Shaleitian Bulge of Zhangjiakou-Penglai Fault Zone went through two periods, Oligocene and Pliocene-Quaternary, and the Bohai section was active earlier than the inland section. (3) The sinistral strike slip displacement of Zhangjiakou-Penglai Fault is 4 km since Cenozoic, including 1 km in the Oligocene, and 3 km in the Pliocene-Quaternary. (4) The strike-slip movements have resulted in the increase of fault activity and basin-mountain restructure in the fault zone, also contributed to the formation of the central tectonic belt and the conjugate evolution in north-east structural belt. (5) The conjugate strike slip of the Zhangjiakou-Penglai Fault Zone dominated the migration and accumulation of hydrocarbon in shallow formations by controlling the injection points and segments of hydrocarbon from the deep layers to shallow layers.

Paleomagnetism of the Upper Paleozoic of the Novaya Zemlya Archipelago

The rock magnetic and paleomagnetic results from the Upper Paleozoic sedimentary sequences composing the isles of the Novaya Zemlya Archipelago are presented. The recorded temperature dependences of the magnetic susceptibility, the magnetic hysteresis parameters, and the results of the first-order reversal curve (FORC) measurements suggest the presence of single-domain or pseudo-single-domain magnetite and hematite grains in the rocks. The Upper Paleozoic deposits overall are promising for unraveling the tectonic evolution of the Barents–Kara region. Together with the rock magnetic data, the positive fold and reversal tests testify to the primary origin of the indentified magnetization components. However, the interpretation of the paleomagnetic data should take into account the probable inclination shallowing. New substantiation is offered for the paleomagnetic poles for Early Devonian and Late Permian. For the first time, paleomagnetic constraints are obtained for the Late Carboniferous boundary. It is shown that the Early Cimmerian deformation stage within the Paikhoi–Novaya Zemlya region is associated with the sinistral strike slip displacement along the Baidaratskii suture during which the internal structure of the Southern Novaya Zemlya segment could undergo shear in addition to the nappe-thrust transformations. The Northern Novaya Zemlya segment, which is shifted northwest with respect to the Southern segment, was deformed in the thrusting mode with an overall clockwise rotation of this segment relative to the East European Craton.

Late Cenozoic transpressional mountain building directly north of the Altyn Tagh Fault in the Sanweishan and Nanjieshan, North Tibetan Foreland, China

For many tectonicists, the structural development of the northern Tibetan Plateau stops at the Altyn Tagh Fault (ATF). This study challenges that assumption. Structural field observations and remote sensing analysis indicate that the Sanweishan and Nanjieshan basement cored ridges of the Archean Dunhuang Block, which interrupt the north Tibetan foreland directly north of the ATF, are bound and cut by an array of strike-slip, thrust and oblique-slip faults that have been active in the Quaternary and remain potentially active. The Sanweishan is a SE-tilted block that is bound on its NW margin by a steep south-dipping thrust fault that has also accommodated sinistral strike-slip displacements. The Nanjieshan consists of parallel, but offset basement ridges that record NNW and SSE thrust displacements and sinistral strike-slip. Regional folds characterize the extreme eastern Nanjieshan and appear to have formed above blind thrust faults which break the surface further west. Previously published magnetotelluric data suggest that the major faults of the Sanweishan and Nanjieshan ultimately root to the south within conductive zones that are inferred to merge into the ATF. Therefore, although the southern margin of the Dunhuang Block focuses significant deformation along the ATF, the adjacent cratonic basement to the north is also affected. Collectively, the ATF and structurally linked Sanweishan and Nanjieshan fault array represent a regional asymmetric half-flower structure that is dominated by non-strain partitioned sinistral transpression. The NW-trending Dengdengshan thrust fault system near Yumen City appears to define the northeastern limit of the Sanweishan-Nanjieshan block, which may be regionally viewed as the most northern, but early-stage expression of Tibetan Plateau growth into a slowly deforming, mechanically stiff Archean craton.

Cenozoic evolution of the Tan–Lu Fault Zone (East China)—Constraints from seismic data

The Tan–Lu Fault Zone (TLFZ) is a continental-scale strike–slip fault zone in the East China that contains rich and significant information about the Mesozoic–Cenozoic evolution of eastern Asia. It experienced a long-term and complex superimposed deformation characterized by Mesozoic sinistral and Cenozoic dextral motions. The fault has a well-documented Mesozoic sinistral displacement history, but its Cenozoic history is poorly known. In this study, based on the observations of the interrelationships of fault kinematics, fault geometry and concomitant sedimentation, the Cenozoic evolution of the TLFZ is constrained by abundant seismic data from oil fields. Numerous bends along the Cenozoic master fault sensitively record changes in the stress field during strike–slip motion. Taking into account the Cenozoic evolution of the Bohai Bay Basin (east China), the evolutionary history of these strike–slip bends is investigated, and the results indicate that dextral motion along the TLFZ began at about 40Ma. Furthermore, the Cenozoic evolutionary history of the TLFZ is suggested to include an extensional deformation (with a possible weak sinistral shear) from 65 to 40Ma. From 40 to 0Ma, dextral motion occurred due to a change in the subduction direction of the Pacific Plate relative to the Eurasian Plate causing the fault to experience dextral shear with a component of extensional deformation. Dextral motion was most intense from 40 to 25Ma, and then the dextral direction may have suddenly changed from a nearly NE–SW trend to a nearly N–S trend at around 25Ma. Dextral motion was relatively enhanced again after 12Ma and was particularly strong after 5Ma. Episodic and ephemeral thrusting deformation might have occurred during the Quaternary. The cumulative Cenozoic dextral displacement of the TLFZ is far smaller than its Mesozoic sinistral strike–slip displacement (may be no more than 21km).

The use of speleothem damage and in situ fault displacement monitoring to characterise active tectonic structures: an example from Západní Cave, Czech Republic

The EU-TecNet fault displacement monitoring network records three-dimensional displacements across specifically selected tectonic structures within the crystalline basement of central Europe. This paper presents a study of recent and active tectonic fault displacement recorded at Západní Cave in northern Bohemia (Czech Republic). It extends previous geological research by measuring speleothem damage within the cave and monitoring displacements across two fault structures within the Lusatian Thrust Zone. The measured speleothem damage, which are characterised by strike-slip movements, show dextral strike-slip displacement along the WSW-ENE striking fault and sinistral strike-slip displacement along the NNW-SSE striking fault. It is found that the compressive stress σ1 is located in the NW or SE quadrant while the tensile stress σ3 is oriented perpendicular to σ1, i.e. in the NE or SW quadrant. The results of fault displacement monitoring show a long-term dextral strike-slip trend along the WSW-ENE striking fault while the NNW-SSE striking fault presents evidence for uplift of the eastern block. There are notable periods of increased geodynamic activity, referred to as pressure pulses, in 2008, 2010-2011, and 2012. The significant correspondence between the measured speleothem damage and the results of fault displacement monitoring confirm the supposition that, at this site, the compressive stress σ1 persists in the NW or SE quadrant. The presented results offer an insight into the periodicity of pressure pulses, demonstrate the necessity for protracted monitoring periods as a means for better understanding geodynamic processes, and show that it is possible to characterise the displacements that occur across individual faults in a way that cannot be accomplished from geodetic measurements made using Global Navigation Satellite Systems.

Aqaba-Levant transform-related faults in the Gulf of Suez rift: The Durba–Araba fault, Sinai Peninsula, Egypt

The Gulf of Suez rift is dominated by NNW- to NW-striking “Clysmic” faults trending parallel to the rift. In addition there are NNE- and WNW-striking (oblique) faults that trend at an angle to the rift. The Durba–Araba fault (DAF) in southwestern Sinai represents one of several NNE-striking faults. It separates the Durba fault block on its NW from the Araba fault block on its SE. Detailed (1:20,000 scale) field mapping and structural studies of the DAF and the onshore area to the east of Belayim Bay (eastern margin of the central Gulf of Suez rift), indicate that the exposed part of the DAF extends for 7.5km NNE from the mouth of Wadi Araba, at which point it bends and splays into three N- to NNW striking faults, forming a horse tail structure. The fault shows 4km of pure sinistral strike-slip displacement. Northerly plunging fault propagation folds in the Phanerozoic rocks adjacent to the DAF accommodated the sinistral displacement. These folds are cut and displaced by the splay faults. Near its northern end, the middle splay fault affects the Pliocene El Qa’a Formation. At Gebel Qabeliat a group of en echelon left-stepping NNE- to N-striking faults overlaps the DAF generating a pull-apart (rhomb) graben, in which Pliocene and Quaternary sediments are downthrown against the Upper Miocene rocks. Kinematic indicators on most of these faults show major sinistral strike-slip movement. Palaeostress analysis of slip striae indicates sub-horizontal ENE to NNE extension, comparable to the present day stress regime. Cross-cutting relationships indicate that the NNE- to N-striking oblique faults are younger than the NW-striking Clysmic faults. These faults are probably presently active since they affect Pliocene and Quaternary sediments. It is proposed that these faults are related to the Aqaba-Levant transform that has been active since the Middle Miocene.

Metallogenic epoch of the Jiapigou gold belt, Jilin Province, China: Constrains from rare earth element, fluid inclusion geochemistry and geochronology

The Jiapigou gold belt is located on the northern margin of the North China Craton, and is one of the most important gold-mining and production regions in the circum-Pacific metallogenic zone. Research has been conducted in this area since the 1960s, however, the timing of the gold mineralisation is still unresolved, and an ideal metallogenic model has not been well established. To address these questions, a systematic geological, geochemical and geochronological investigation was conducted. The study revealed that (i) the gold-bearing quartz veins can be divided into two groups, earlier and later gold-bearing quartz veins according to their occurrence and the geochemical characteristics, (ii) the geochemical characteristics of the ore bodies, while similar to granite, are clearly different from the altered rock, and (iii) the geochemical characteristics of the later gold-bearing quartz veins have more similarity to the altered rock than the earlier gold-bearing quartz veins do. Therefore, we conclude that two independent stages of metallogenesis within the Jiapigou gold deposit area are related to magmatic activity in the Palaeoproterozoic and the Yanshanian stage of the Mesozoic, that the ore-forming fluids are mainly of magmatic origin, and that magma contamination by the altered rock was stronger in the Mesozoic. Zircon LA–ICP–MS U–Pb data show that the age of the Palaeoproterozoic granite is ~2426.0 Ma and that of the Mesozoic granite is ~166.2 Ma; these ages can be interpreted as the maximum ages of the two periods of gold mineralisation. In addition to investigating the geotectonic and regional structure of the Jiapigou gold belt, this study also proposes that the WNW-trending zone of gold mineralisation is a result of a magmatic event within the basement in the early Palaeoproterozoic, and that large-scale sinistral strike-slip displacements of the Huifahe and Liangjiang Faults in the late Middle Triassic (Yanshanian epoch) controlled the later tectono-magmatic event and the NNE–ENE-trending zone of gold mineralisation.

Applications of water-based magnetic gradiometry to assess the geometry and displacement for concealed faults in the southern Adirondack Mountains, New York, U.S.A

Abstract An integrated magnetic gradiometry and structural analysis was conducted on three lakes in the southern Adirondacks Mountains, New York, in order to develop a geometric and kinematic model for concealed and long lived faults that transect the Proterozoic basement structures, offset Paleozoic strata to the south, and may be associated with the development of the post-Paleozoic cratonic dome (the Adirondack dome). Two lakes occur along the trace of two of the most prominent topographic lineaments that have been proposed to be faults in the southern Adirondack Mountains, and a third lake is located at the apparent fault intersection. Hinkley Lake occurs over the east–west trending lineament that corresponds to the trace of the Prospect fault. Indian Lake resides in a set of north–northeast trending pronounced lineaments that transect an anorthosite-cored structural dome and are inferred to be faults on the NYS geologic map. Piseco Lake is immediately adjacent to the intersection of the two proposed fault zones (Prospect and Indian Lake fault zones). Magnetic surveys were conducted on all three lakes, resulting in anomaly maps. Accompanying two dimensional geologic models for Hinkley and Piseco Lake were produced. At Piseco Lake, field evidence supports a brittle deformation history with sinistral-normal displacement. A similar deformation history is consistent with field data collected at Indian Lake. Correlation of the two dimensional magnetic models resulted in a sinistral, releasing-bend fault geometry beneath Piseco Lake, and the fault truncation of a granitic gneiss cored antiform for the subsurface geology of Hinkley Lake. The magnetic data and models suggest that Piseco Lake resides over a sinistral, pull-apart structure with sufficient throw to preserve the lowermost Paleozoic strata that once covered much of the Adirondack dome. This would account for both sinistral strike-slip and normal displacement on the interpreted faults, at Piseco and Indian Lakes, and rotation of structural blocks as the result of fault interaction. Relative timing, regional relationships, and ties to published ages suggest that the distribution of the faults is a relic of Neoproterozoic Iapetan rifting, Paleozoic displacement, and Mesozoic uplift of the Adirondack dome. Finally there is probable correlation of these faults with modern seismic activity.

Shear structures in the Serra do Azeite shear zone, southeastern Brazil: Transtensional deformation during regional transpression in the central Mantiqueira province (Ribeira belt)

The Serra do Azeite shear zone (SASZ) is a northeast-trending regional structure in southeastern Brazil. Kinematic analysis carried out in the SASZ suggests a ductile sinistral transtensional regime in amphibolite facies conditions. Constrictional, flattened, and simple-shear strain domains occur in mylonites with stretching lineation plunging to the east–southeast. Kinematic indicators suggest oblique top–down-to-the-east–southeast and sinistral strike-slip components along variably oriented shear planes. Results of the simple geometrical construction applied to the shear-zone pattern, coupled with field data and kinematic analysis, suggest that sinistral transtensional shearing resulted from east–northeast-directed crustal extension and sinistral strike-slip displacement, accompanied by north–northeast/south–southwest contraction and vertical thinning. The K/Ar and Ar/Ar cooling ages match the proposed interval for crustal extension in the central Mantiqueira province (0.6–0.58/0.57 Ga) based on ages of alkaline granitoids and volcanic rocks. These data indicate types-I and -S granite magmatism, as well as metamorphism and dextral transpressional deformation along the Ribeira belt. Therefore, we interpret the transtensional regime as a result of southwest-directed lateral extrusion and uplift crustal slices (overall oblique extrusion) during an orogenic-scale partitioned transpressional regime. Our results suggest this regime was coeval with a phase of regional stretching subparallel to the Ribeira belt, which would explain the coexistence of extensional and compressional structures during overall plate convergence.

A reassessment of the tectonic zonation of the Uralides: implications for metallogeny

Abstract A review of the structural zonation of the ‘oceanic’ Urals shows that only its westernmost Sakamara, Tagil and Magnitogorsk zones reveal the presence of thrust structures, whereas in the East Uralian megazone and Trans-Uralian zone, the classic zonation rather reflects late- or post-collisional granitic welding and strike-slip displacement of the orogen for 100–300 km. This sinistral strike-slip displacement is responsible for the lens-shapes structure of the individual zones in the Urals. Metallogenically, these orogen-parallel faults and the eastern boundary of the East European craton control the distribution of the orogenic Au deposits. Restoration of the individual zones into their pre-strike-slip fault positions suggests that the Urals contains only two magmatic arcs, one in the west and one in the east. The western Tagil-Magnitogorsk immature arc hosts a variety of chromite, Alaska-type PGE and major VMS deposits. The eastern Valerianovka arc effectively stitches together the Kazakh-Tien Shan structures and is host to important copper-gold and giant iron(-copper) skarn deposits. The geodynamic evolution of the Urals can be observed with the generation of the immature Tagil-Magnitogorsk magmatic arc in the Late Ordovician. Metallogenic zoning of the VMS deposits supports the petrological data that the arc developed due to eastward subduction inside the oceanic back-arc basin that existed in the rear of the Kazakhstan-Tien Shan arcs. In the late Palaeozoic, these arcs collided with each other and were together thrust onto the East European craton. Syncollisional granitoid intrusions welded the magmatic arcs, which were soon displaced into presently observed fragments along the post-collisional orogen-parallel strike-slip faults.

Late Mesozoic–Cenozoic sedimentary basins of active continental margin of Southeast Russia: paleogeography, tectonics, and coal–oil–gas presence

Various settings took place during the Late Mesozoic: divergent, convergent, collisional, and transform. After mid-Jurassic collision of the Siberian and Chinese cratons, a latitudinal system of post-collision troughs developed along the Mongol-Okhotsk suture (the Uda, Torom basins and others), filled with terrigenous coal-bearing molasse. The dispersion of Pangea, creation of oceans during the Late Jurassic are correlated to the emergence of the East Asian submeridional rift system with volcano-terrigenous coal-bearing deposits (the Amur-Zeya basin). At that time, to the east there existed an Andean-type continental margin. Foreland (Upper Bureya, Partizansk, and Razdolny) and flexural (Sangjiang-Middle Amur) basins were formed along the margin of the rigid massifs during the Late Jurassic to Berriasian. During the Valanginian-mid-Albian an oblique subduction of the Izanagi plate beneath the Asian continent occurred, producing a transform margin type, considerable sinistral strike slip displacements, and formation of pull-apart basins filled with turbidites (the Sangjiang-Middle Amur basin). The Aptian is characterized by plate reorganization and formation of epioceanic island arcs, fore-arc and back-arc basins in Sakhalin and the Sikhote-Alin (the Alchan and Sangjiang-Middle Amur basins), filled with volcanoclastics. During the mid-Albian a series of terranes accreted to the Asian continental margin. By the end of the Albian, the East Asian marginal volcanic belt began to form due to the subduction of the Kula plate beneath the Asian continent. During the Cenomanian–Coniacian shallow marine coarse clastics accumulated in the fore-arc basins, which were followed by continental deposits in the Santonian–Campanian. From the Coniacian to the Maastrichtian, a thermal subsidence started in rift basins, and continental oil-bearing clastics accumulated (the Amur-Zeya basin). Widespread elevation and denudation were dominant during the Maastrichtian. This is evidenced by thick sediments accumulated in the Western Sakhalin fore-arc basin. During the Cenozoic, an extensive rift belt rmade up of a system of grabens, which were filled with lacustrine–alluvial coal–and oil-bearing deposits, developed along the East Asian margin.

The Batman and Quigleys gold deposits of the Mt. Todd (Yimuyn Manjerr) Mine, Australia: structural, petrographic and mineralogical investigations of coeval quartz sulphide vein and lode/stockwork systems

The Mt. Todd Mine (renamed the Yimuyn Manjerr in August 2000) in the Northern Territory of Australia is located at the southern end of the Pine Creek Inlier (PCI). The mine is host to several discrete ore bodies that strike NNE within a broad NE-trending corridor of gold mineralisation. These deposits exhibit a spatial association with local granite plutons and, in particular, are situated within the intermediate contact metamorphic aureole of the Tennysons Leucogranite. They exhibit a marked difference in ore style, ore system and dominant sulphide mineralogy. The Batman and Quigleys deposits of the Mt. Todd Mine are located 4–5 km apart within the NE-trending corridor of gold mineralisation. The Batman deposit comprises a stack of discontinuous, steeply west-dipping sheetlike veins within an ore envelope that defines a broad zone of normal faulting. It constitutes a quartz–pyrrhotite–pyrite dominant system of >500-m depth continuity. The Quigleys deposit comprises a series of discontinuous, east-dipping lodes that are interconnected and subtended by stockwork veins within a single continuous fault plane. The deposit constitutes an arsenopyrite–pyrite-dominant system of limited depth continuity. Despite their differences, detailed structural, petrographic and mineragraphic studies of the vein/lode systems have established that the deposits are similar in vein/lode morphology, principal orebody-forming process, tectonic history, alteration assemblage and relative geological timing. There is broad agreement in the type of host lithofacies and an association with a NE-trending regional magnetic lineament. The studies suggest that mineralogic differences between the deposits are the result of a gross metal and sulphide zonation about the Cullen Batholith that corresponds with decreasing temperature and increasing distance from the margin of the batholith as noted by other workers. The deposits are therefore interpreted to have formed at the same time in response to similar structural and tectonic controls. Gold mineralisation in the Mt. Todd Mine is thereby constrained to a single mineralising event. The quartz sulphide veins and lodes of the Batman and Quigleys deposits are typified by hydrothermal fracturing and/or normal faulting of the upper crust during sinistral strike–slip displacement on a NE-trending basement strike–slip fault. The deposits are similar to other orogenic gold deposits within the PCI, but with affinity to the thermal aureole gold style. However, in the Batman deposit, the association of gold with bismuth and reduced ore mineralogies makes this deposit unique in the PCI.

Deformation in Neogene sediments of the Sorbas and Vera Basins (SE Spain): constraints on simple-shear deformation and rigid body rotation along major strike-slip faults

Detailed structural analyses are presented of the Neogene Sorbas Basin adjacent to the E–W striking Gafarillos fault zone and the Vera Basin adjacent to the 020° striking Palomares fault zone in southeastern Spain. A stress regime with an E–W oriented subhorizontal maximum principal stress ( σ 1) existed in pre-Tortonian (>11.3 Ma) time. A strike-slip regime with NW–SE oriented compression during Tortonian and earliest Messinian time caused dextral displacement along the E–W trending Gafarillos fault of approximately 10 km. Structural analysis indicates that most displacement took place in the Early Tortonian. Deformational patterns within the adjacent pull-apart basin reflect a dextral simple shear-zone of at least 500 m width. Kinematical analysis of folds in the Sorbas Basin suggests, however, that rotational effects are largely caused by rigid-body rotation without much internal deformation. Sinistral strike-slip displacements occurred along the Palomares fault zone under the influence of the same stress-regime. An abrupt change in the orientation of the stress field to N–S directed compression in earliest Messinian time (6.5 Ma) caused the termination of displacements along the Gafarillos fault zone, whereas the 020° trending Palomares fault zone continued to accumulate sinistral strike-slip displacements of about 25 km. Volcanism occurred along splays of the fault zone. A wider shear-zone of a few kilometers width evolved, in which considerable anti-clockwise rotation of folds occurred. Kinematic analysis of these folds shows that these rotational effects are again dominantly rigid-body rotations. Assuming rotations are merely caused by simple-shear deformation overestimates the amounts of strain. A better way to deal with simple-shear deformation is to compare observed shortening caused by folding with the magnitude of rotation of fold-hinges.

Deformation features in Paleogene sands in the Hoegaarden area (Belgium)

During excavation works for the construction of the TGV track along the motorway Brussels-Liège (E40) near the interchange Tienen-Hoegaarden-Jodoigne a number of interesting, but only temporary outcrops were created. These outcrops offered not only the occasion to learn more about the stratigraphy, paleogeography and paleobotany of the Paleogene, but also revealed some particular deformation features. The Outgaarden Section, SE of the interchange, showed chaotically deformed sands at the base of the Upper Paleocene Tienen Formation. The highly viscous deformation features originated in a high-energy depositional environment. Dewatering, mass movements and strong currents caused the syndepositional, probably gravitationally-induced sediment deformation. The Goudberg Section, NW of the interchange, exposed the Overlaar Petrified Forest, of which part of the silicified tree-stumps were recovered to constitute the main feature of the planned GEOPARK HOEGAARDEN. In this section tectonically-induced faulting could be demonstrated. The fault shows a clear normal displacement. A sinistral strike-slip displacement is moreover supposed. Faulting occurred prior to the deposition of the Pleistocene loam cover but definitively postdates the deposition of the Ypresian clays. It is proposed that this faulting event in the Tertiary sediments may be caused by a reactivation of underlying master faults in the Lower Paleozoic basement of the Brabant Massif.

Progressive changes in sedimentary facies and stratal patterns along the strike-slip margin, northeastern Jinan Basin (Cretaceous), southwest Korea: implications for differential subsidence

Abstract In strike-slip basins, proximal stratal patterns are a function of displacement on basin-bounding faults. In order to better understand factors that control changes in sedimentary facies and stratal patterns of the northeastern part of the Jinan Basin (Cretaceous), a strike-slip basin, we made a detailed analysis of sedimentary facies, depositional architecture and paleoflows. The sedimentary successions can be grouped into five facies associations representing five depositional environments: (1) facies association FA I (alluvial fan); (2) FA II (small-scale Gilbert-type delta); (3) FA III (large-scale, steep delta slope); (4) FA IV (base of large-scale, steep delta slope and prodelta); and (5) FA V (lacustrine plain). The successions are divided into two distinct sedimentary fills on the basis of facies associations, depositional architecture and paleocurrents: (1) marginal fill and (2) longitudinal fill. The marginal fill (ca. 3.2 km thick) is present along the strike-slip basin-bounding fault. The lower part of the marginal fill (ca. 1.3 km thick) consists of alluvial-fan deposits (FA I) along the bounding fault which are transitional northward to small-scale Gilbert-type delta (FA II) and lacustrine plain (FA V) deposits. The upper part of the marginal fill (ca. 1.9 km thick) contains large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits accompanied with a northward change in facies associations. In the marginal fill, the successive alluvial fan, small-scale Gilbert-type delta and large-scale, steep delta/prodelta deposits are overlapped (shingled) northeastward. The longitudinal fill (ca. 2 km thick) is characterized by eastward overlapped stacks of large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits with a westward progradation. The longitudinal fill was overstepped by the marginal fill. The northeastward shingled geometry of the marginal fill was most likely caused by sinistral strike-slip displacements on the basin-bounding fault. The slightly oblique (northward) progradation of the marginal fill was due to the northward basin-floor tilting. In the marginal fill, the progressive changes in facies and depositional architecture from the lower alluvial fan/small-scale Gilbert-type delta to the upper large-scale, steep delta/prodelta are suggestive of increase in basin subsidence along the strike-slip basin margin that was closely related to the variation in displacement on the basin-bounding fault. The sinistral strike-slip movements on the bounding fault also caused the eastward overlapping of the longitudinal fill.

Structural evolution of the northeast Asian continental margin: an example from the western Koryak fold and thrust belt (northeast Russia)

The western Koryak fold and thrust belt consists of a set of tectonostratigraphic terranes that contain units ranging from Lower Palaeozoic to Cenozoic. Three deformational events have been identified in the study area. The first event structures are folds, domes and shear zones with related high-pressure/low-temperature metamorphism. These structures are early Carboniferous and are only recognized in the metamorphic terranes. The second event structures are imbricate fans of thrusts and folds with southeast vergence, broken formation and serpentinite mélange. These are latest Jurassic to early Cretaceous (early Albian) and occur throughout the study area. During this event, thrusting was accompanied by dextral strike-slip faulting. The second event structures are overlapped by the Upper Albian sedimentary rocks with an angular unconformity at the base. During metamorphism associated with the first and second deformational events, some of the rocks were metamorphosed to blueschist grade and were affected by strain with axial ratios of up to 15[ratio ]1. The third deformational event is characterized by significant sinistral strike-slip displacement at higher crustal levels. This resulted in a new set of structures and rotation of pre-existing structures. The age of the sinistral strike-slip faults is interpreted to be late Cretaceous to Cenozoic. The kinematics of the second and third deformational events correspond to assumed proto-Pacific plate motions based on palaeomagnetic data.

Three-dimensional accommodation analysis of the Triassic in the Paris Basin: a new approach in unravelling the basin evolution with time

The mechanisms governing the development of the Paris Basin throughout the Triassic are regarded as being the result of superimposed and successive processes. In this study, the Triassic succession of the Paris Basin was re-interpreted in a sequence stratigraphic context, using essentially wireline log data. From this, a series of isopach maps, lithofacies maps and palaeobathymetric maps was produced for each sequence. Three-dimensional accommodation analysis was then carried out sequence by sequence, over the entire basin to produce a precise, detailed accommodation history for the entire Triassic succession. Previous studies have proposed that the Triassic was deposited during a rift period in a transtensional stress regime, with the formation of a trough superposed onto three fault systems derived from the Variscan structural framework. In this study, Scythian to Ladinian sediments (Buntsandstein and Muschelkalk) record the stress regime that prevailed over much of NW Europe. The basin architecture at this time is in continuity with the neighbouring Germanic Basin. Our three-dimensional accommodation modelling shows that the stress regime changed during the Carnian and the late Norian (Keuper). The Carnian events are marked by (1) the creation of a large depocentre infilled with halite, and (2) a northwest migration of this depocentre during the mid-late Carnian along with deposition of the Grès-à-Roseaux, an extensive fluvial deposit. This documents renewed strike-slip movement along the Bray fault. The Norian events involved major tectonic uplift on the basin margins, producting fan delta progradation into the basin. Rotation of the previous depocentre axis occurs on the downthrown side of the Bray fault. This may be viewed as a consequence of sinistral strike-slip displacement along the Bray fault, forming a local transpressive stress regime. The following Liassic cycle commenced with the Rhaetic sequences and illustrates a complete change in the stress regime. This corresponds with the new stress regime which prevailed over northwest Europe during the Liassic cycle. Accommodation curves from the basin complement this interpretation recognising two major accommodation phases which are separated by a significant unconformity. Both phases record periods of accelerating accommodation followed by a more uniform phase of decelerating accommodation. The accelerating phases correspond to periods of rapid accommodation space creation and result in thick evaporite deposits. They correspond to ‘rift pulses’ which occurred in the remote North Atlantic and Tethyan domain. Each accommodation phase is proposed to correspond to lithospheric stretching pulses followed by a relaxation period. This study illustrates the importance of sequence stratigraphy coupled with three-dimensional accommodation analysis in refining important stages in the basin evolution with time.

Late Quaternary faulting and neotectonics, South Victoria Land, Antarctica

Three Quaternary fault traces in Hidden and Garwood Valleys, South Victoria Land, provide direct evidence for neotectonic activity in the Transantarctic Mountain rift shoulder of the West Antarctic Rift system. The faults trend NE-SW and all show a large component of sinistral strike-slip displacement. The late Quaternary faults lie parallel to Palaeozoic brittle structures, suggesting that inherited anistropy has governed younger fault orientations. Sinistral displacement on NE-SW-striking Quaternary faults appears to be inconsistent with the predicted Cenozoic NW-SE dextral oblique extensional regime in South Victoria Land but can be accommodated by minor clockwise rotation of crustal blocks.