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In summary, the parsimonious explanation is that the mylonitic lineation is the LDZ transport direction, and that the LDZ is part of the larger Keisarhjelmen detachment, along with the overlying Wilhelmtinden mylonite zone (Fig. LDZ kinematics [8] describe a shallowly NNW-plunging lineation on the west-dipping mylonitic foliation (their fig. 8), but with uncertain kinematics as indicators were not observed. [8] present valuable new isotopic and field data regarding NW Spitsbergen's tectonic history, and propose the existence of the Germaniahalvøya terrane with Scandian (Late Caledonian) igneous activity and deformation. Within this terrane, the Lerner Deformation Zone (LDZ) is cast as an east-directed thrust, with the Liefdefjorden Migmatite Complex in the footwall and Lenerøyane Group metasediments above. [Extracted from the article]

Fluid escape pipes are vertical pathways of focused flow venting from a variety of deep overpressure sources. These geological features are typical of many sedimentary basins, including proven petroliferous provinces worldwide, such as the North Sea and the Exmouth Plateau in the Northern Carnarvon Basin, NW Australia. High-quality three-dimensional (3D) seismic reflection data from the western Exmouth Plateau revealed the occurrence of exceptionally well-imaged fluid escape pipes affecting the Jurassic strata and the Triassic Mungaroo Formation, a key reservoir unit in the basin. A total of 171 fluid escape pipes, including blowout, seepage and hydrothermal pipes, were mapped, and their geomorphological characteristics were analysed. In the study area, these features form prominent vertical columns up to 4.5 km long disrupting continuous reflections of the Triassic to Jurassic section. Numerous fluid escape pipes terminate with palaeo-pockmarks affecting the Upper Jurassic syn-extension strata, providing evidence for pipe genesis during the early stages of the Late Jurassic rifting in the Exmouth Plateau. Fluid escape pipes were found rooting from different stratigraphic levels, suggesting multiple fluid sources within the Triassic sediments. Several fluid flow structures nucleated along or near rift-related fault planes within the Mungaroo Formation, providing further evidence of rifting as a main triggering factor of important fluid flow in the basin. In the study area, the presence of fluid escape pipes represents a significant risk for the preservation of potential hydrocarbon accumulations, as, when these features form, vertical fluid venting breaches through stratigraphy, compromising the integrity of seal units. This seems supported by the lack of significant discoveries within the area covered by seismic survey analysed in this study. [ABSTRACT FROM AUTHOR]

Widespread wrench tectonics have been described along the northern Andes. The Bucaramanga fault, described as sinistral strike-slip, bounds the high Santander Massif. We combine structural and thermochronological data from the central-southern portion of the fault to investigate the vertical displacement. The structural survey data show old phases of activity preserved in the host rocks along the fault trace, with the superimposition of different generations of slickenlines, and both strike-slip and dip-slip kinematics indicators. New and previous thermochronological data show that differential exhumation of the fault walls has been ongoing for the last 50 Ma. The hanging wall, the Santander Massif, records, in the central portion, decreasing exhumation rates from the early Miocene to the mid- to late Miocene and, in the southern portion, constant rates from the Late Oligocene to the Pliocene. Combining such observations, the thermochronological offset resulting from the relative motion of the two fault walls is comparable with the observed drop in elevation across the fault, suggesting that the present topography of the Santander Massif is related to vertical movement along the Bucaramanga fault. We infer that the fault has a significant Neogene reverse component, consistent with the present day horizontal global positioning system vector data, long-term exhumation rates and the structural assemblage. Supplementary Material: The Supplementary Materials contain methodological information on the thermochronological procedures, a compilation of the previously published data used in this study and the structural geology dataset, https://doi.org/10.6084/m9.figshare.c.4620140 [ABSTRACT FROM AUTHOR]

The identification of extensive intrusive igneous complexes in both subsurface data and field studies has led to the quantification of the volumes of igneous material present within sedimentary sequences. Despite this research, however, little connection has been established between the amount of igneous material intruded into a basin and its effect on subsequent basin evolution in terms of burial and loading. We used subsurface data from the Faroe-Shetland Basin to investigate igneous intrusions with the aim of understanding how additional igneous material influences basin evolution. We found that the total estimated thickness of Cretaceous sediments is likely to be an overestimate because the sedimentary fill consists of significant quantities of igneous material emplaced during the Paleocene (56-54 Ma). This additional igneous material has not previously been accounted for in estimates of sedimentation rates and the burial history of the Faroe-Shetland Basin. Petroleum system modelling to understand the generation and expulsion of hydrocarbons benefits from correct estimates of basin fill. The overthickening of basins by igneous material will affect the timing of hydrocarbon generation and therefore the correct evaluation of exploration targets. The volume of igneous material and the time at which this material was emplaced must be acknowledged and considered in order to fully understand basin evolution. [ABSTRACT FROM AUTHOR]

The break-up of continents at magma-poor rifted margins is a complex yet little understood process accounting for intricate interactions between tectonic and magmatic processes. Whereas high-resolution seismic data may resolve the firstorder architecture of ocean-continent transitions (OCTs), direct access to rocks remains limited to deep-sea drilling. In this study, we combine seismic observations from the East Antarctica margin (Geoscience Australia Survey 228) with field observations from the Bracco-Levanto area (Northern Apennines, Italy), representing modern and fossil examples of ultradistal magma-poor rifted margins respectively. The combination of detailed structural mapping and petrological studies from fossil examples with architectural features observed in seismic sections from present-day OCTs enables to bridge the different observation scales. Field evidence indicates that the magmatic budget is not zero, as magma is present throughout the exhumation process. Extensional detachment faults that exhumed serpentinized mantle and deep-seated gabbro intrusions are truncated by later high-angle normal faults, which most probably acted as feeders for the emplacement of massive synextensional basalts. These observations suggest a polyphase tectonic and magmatic evolution of the ultra-distal margin prior to the formation of the first true oceanic crust, which can be studied in detail only by combining seismic and outcrop observations. [ABSTRACT FROM AUTHOR]

Many sedimentary rock successions contain plan-view circular structures, such as impacts, diapirs and carbonate build-ups. When remotely sensed, it can be difficult to discriminate between their formation mechanisms. Herewe examine this problem by assessing the origins of circular structures imaged in high-resolution multibeam bathymetric data fromWeymouth Bay, UK. The imagery shows 30-150 m across, concave-down structures within the upper Purbeck Limestone Group on the southern limb of the Purbeck Anticline. Similar structures have not been identified in the extensive outcrops around the bay. The morphology and geological setting of the structures are consistent with three different interpretations: carbonate mounds, periclinal folds and evaporite diapirs. However, none of these structures has been previously recorded in the upper Purbeck Limestone Group outcrops of this internationally renowned geological region. We apply a scoring system to 25 features of the circular structures to discriminate between these three alternative interpretations. This analysis indicates that evaporite diapirs are the least likely and carbonate mounds the most likely origin of the structures. The presence of carbonate mounds revises the upper Purbeck palaeofacies distribution in its type area and provides an analogue for the exploration for hydrocarbon reservoirs in lacustrine mounds. [ABSTRACT FROM AUTHOR]

The Nallamalai Fold Belt comprises late Palaeoproterozoic to Mesoproterozoic sedimentary rocks deformed into a fold-and-thrust belt along the eastern side of Peninsular India. The age of thin-skinned thrusting, folding and low- to mediumgrade metamorphism in the belt is unclear, with estimates ranging from Palaeoproterozoic to early Palaeozoic. A possible Pan-African age for thrusting has previously been inferred from Rb-Sr dating of muscovite in shear zones from the adjacent Krishna Province (501 - 474 Ma) but these structures are separated from the Nallamalai Fold Belt by a major thrust. Here, we present in situ U-Pb dating of metamorphic monazite within a low-grade metasedimentary rock in the Nallamalai Fold Belt at the Mangampeta barite mine. Our date of 531 ± 7 Ma for the monazite is the first direct evidence that west- to NW-directed nappe stacking, folding and low-grade metamorphism in the fold belt are related to Pan-African incorporation of India into the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

Seismic reflection data allow for the 3D imaging of monogenetic edifices and their corresponding plumbing systems. This is a powerful tool in understanding how monogenetic volcanoes are fed and how pre-existing crustal structures can act as the primary influence on their spatial and temporal distribution. This study examines the structure and lithology of host-rock as an influence on edifice alignment and provides insight into the structure of shallow, sub-volcanic monogenetic plumbing systems. The anticlinal Ben Nevis Structure, located in the northerly extent of the Faroe-Shetland Basin, NE Atlantic Margin, was uplifted during the Late Cretaceous and Early Paleocene by the emplacement of a laccolith and a series of branching sills fed by a central conduit. Seismic data reveal that multiple intrusions migrated up the flanks of the Ben Nevis Structure after its formation, c. 58.4 Ma (Kettla-equivalent), and fed a series of scoria cones and submarine volcanic cones. These monogenetic edifices are distributed around the crest of the Ben Nevis Structure. The edifices are fed from a complex network of sills and transgressive sheets, involving lateral magma migration of tens of kilometres before extrusion at the surface. This work highlights the importance of underlying basin structures in influencing the sites and development of subaerial monogenetic fields, and the importance of lateral magma flow within volcanic systems. [ABSTRACT FROM AUTHOR]

Seismic reflection data and field observations have revealed the presence of voluminous igneous sill complexes emplaced into organic-rich shale formations in sedimentary basins worldwide. Damage and structures associated with sills have major implications for fluid flow through basins. Constraining the distribution of these structures requires a good understanding of the sill emplacement mechanism. However, most mechanical models of sill emplacement assume elastic host behaviour, whereas shale is expected to deform inelastically. This contradiction calls for new field observations to better constrain sill emplacement mechanisms. In this paper, we report on detailed field observations of spectacularly exposed fingers and a sill emplaced in shale at Cuesta del Chihuido, in the Neuquén Basin, Argentina. Exceptional outcrop conditions allow detailed descriptions of both (1) the entire cross-section of the intrusions, and (2) the deformation structures accommodating intrusion propagation in the host rock. All intrusions exhibit irregular, blunt or rectangular tips. The structures accommodating the tip propagation are systematically compressional, including reverse faults, folding and imbricate thrust system. Our observations suggest that the studied intrusions have propagated by pushing the host rock ahead, as a viscous indenter. Our observations suggest that the viscous indenter model is probably a dominant mechanism of sill emplacement in shale. [ABSTRACT FROM AUTHOR]

Four hundred square kilometres of 1 m binned, full coverage swath bathymetry data, integrated with similar resolution onshore topography, have been used to generate a seamless onshore to offshore bedrock map covering an extensive area adjacent to the 'Jurassic Coast' World Heritage site. Analysis of these data provides new insights into the structural development of the Purbeck Monocline Cenozoic inversion structure; in particular, variations in the expression of strain between the hanging-wall block and the fault inversion zone. The footwall to the basin-bounding faults compartmentalized deformation and uplift, and acted as a buttress to compression. The data also show a limited thickness changes within the major lithostratigraphical divisions, and a notable absence of basin-related extensional faulting in the offshore area that is in marked contrast to the more extensively studied onshore region. This indicates that prior to inversion, the basin evolved by intermittent activity on a few major extensional faults. This improved understanding of the development of the basin and inversion structures results from our ability to integrate and quantitatively manipulate these high-resolution and spatially extensive offshore and onshore datasets. [ABSTRACT FROM AUTHOR]

The analytical results of a total of 205 metabasic specimens from 10 palaeomagnetic sites collected from Oscar II Land in Western Spitsbergen are presented. Petrographic, structural and palaeomagnetic data all demonstrate that the pre-Caledonian ferromagnetic fabric of the metabasic rocks has been extensively reoriented and intensively remineralized. New in situ laser ablation inductively coupled plasma mass spectrometry 40Ar/39Ar age determinations suggest that the host rocks have been subject to three resetting events during the 426 - 380 Ma (Caledonian sensu lato), 377 - 326 Ma and c. 300 Ma intervals. The latter two resetting events coincide in time with the Barents Shelf-wide rift-controlled subsidence events. The derived palaeomagnetic data do not fall on the expected apparent polar wander path of Laurussia for syn- to post-Caledonian time. Consequently, four models invoking palaeogeographical great and small circle rotations, regional tectonism involving thrusting and normal listric faulting have been investigated to account for this lack of correspondence. The palaeomagnetic data do not lend support to reconstructions linking Western Svalbard with Pearya but point instead to the importance of listric faulting related to the opening of the North Atlantic Ocean that modified the geometry of the West Spitsbergen Fold and Thrust Belt. [ABSTRACT FROM AUTHOR]

The northern Sinai inverted basins exhibit superb outcrop examples of compressional transfer zones and display the control of these zones on syntectonic and post-tectonic sedimentation. Two main types of transfer zones, hard- and soft-linkage transfer zones, were identified at different scales. Hard-linkage transfer zones form inward and outward fault kinks whereas the soft-linkage transfer zones are expressed by plunging anticline-syncline pairs between overlapping positively inverted fault segments. An example of a wrench-related compressional transfer zone is also displayed by a restraining-bend anticline formed within the strike-slip fault system of the Sinai hinge belt. The displayed examples of compressional transfer zones invariably exerted fundamental control on deposition of syn- and post-tectonic sediments, flow directions of drainage systems, locations of sediment entry points, and the intensity of erosion patterns of the structurally high sediment source areas. This study highlights the close relationship between the transfer zones and hydrocarbon accumulations in clastic syntectonic reservoirs in inverted and wrench basins. [ABSTRACT FROM AUTHOR]

Strike-slip faults are commonly assumed to influence magma transport and emplacement in the Earth's crust. However, direct observations of magma conduits within strike-slip faults are lacking. Here we provide some of the first detailed field observations of dykes emplaced within strike-slip faults in the Neuquén Basin, Argentina. We show how fault planes within strike-slip fault zones affect the emplacement of dyke offshoots, resulting in complex dyke morphology. Our study also emphasizes the importance of pre-existing strike-slip fault array on the development of dyke swarms, showing that orientations of dyke swarms may not systematically relate to the principal tectonic stress axes. [ABSTRACT FROM AUTHOR]

The eastern Aquitaine basin and North Pyrenean Zone show many characteristics of retro-wedge models. However, they differ significantly in that slow subsidence and low deformation continued throughout orogenesis so that growth and steady-state phases cannot be distinguished. We show that the eastern Pyrenees record two clear phases of convergence and probably never attained steady state. Analysis of the Aquitaine retro-foreland basin along the Ariège ECORS deep seismic line, eastern French Pyrenees, integrates a new litho- and chronostratigraphy, subsidence analysis, low-temperature thermochronology data, new interpretations of seismic lines and a balanced cross-section. Within an overall regression, two shallowing-up cycles (Latest Santonian-Danian, Thanetian-Oligocene) record slow tectonic subsidence of the eastern Aquitaine basin separated by a quiet period. Continuing thick-skinned shortening was low to moderate. The early marine basin, generated by loading of the weak, extended margin, was supplied axially from an unknown eastern edifice while the young Pyrenean orogeny to the south remained submerged. During the quiet period of ultra-slow subsidence, no basin migration and negligible sediment supply, continental conditions characterized the eastern orogen. The second marine transgression was quickly followed by continental conditions. The basin was supplied by the now emerging Pyrenean orogen and continued to subside until Miocene time. [ABSTRACT FROM AUTHOR]

The Mississippian North Wales Platform is located on the margins of the East Irish Sea Basin and has been little studied over the last 30 years. The exposed Visean limestones provide new insights into the deposition, porosity evolution, distribution of dolomitization, and Pb-Zn and Cu mineralization on the NorthWales carbonate platform. This is of relevance to the characterization of fault-related dolomite hydrocarbon reservoirs and age-equivalent Mississippi Valley-type mineral deposits. In particular, the study demonstrates the intimate relationship between sedimentation, basin-scale tectonism and postdepositional fluid flux. Depositional cyclicity is marked, with metre-scale upward-shallowing cycles in which pervasive marine and meteoric calcite cements occlude matrix porosity and syndepositional fractures. Consequently, subsequent burial diagenetic replacive dolomitization is matrix selective and cements are primarily restricted to fractures. Seven phases of dolomite are defined based on texture and cathodoluminescence petrography, with phases D1-D3 as the most volumetrically significant. Dolomite phases D0-D2 arematrix replacive, cross-cutting stratigraphy and locally fingering along beds for several metres. Dolomite phases D3-D7 are hosted by faults and fractures and also line vugs. Evidence of telogenesis is recorded where burial diagenetic products are post-dated by calcite cements precipitated from meteoric fluids. Dolomitization probably occurred during the Mississippian and continued into the Pennsylvanian. Pb-Zn mineralization is also interpreted to have occurred during the Pennsylvanian, associated with Variscan tectonism. Overall, the North Wales Platform displays a more complex paragenesis than age-equivalent platforms in the Pennine Basin, owing to multiple phases of burial and exhumation. The study demonstrates the importance of linking burial history to detailed field and petrographical data to understand and predict the spatial and temporal controls on diagenetic processes and products within syn- and post-rift sequences. [ABSTRACT FROM AUTHOR]

The mechanisms of thinning of the lithosphere and destruction of the North China Craton have been debated in recent decades. Their causal link with regional tectonic extension is well exemplified by the exhumation of the Wulian metamorphic core complex (mcc), along the Sulu orogenic belt to the SE of the North China Craton. The Wulian mcc is a Cordilleran type mcc with a northwestward dipping low-angle master detachment fault zone (the Wulian detachment fault zone), an Early Cretaceous supradetachment basin (the Zhucheng Basin) and a lower plate of ultrahigh-pressure metamorphic rocks in the Sulu orogenic belt. Synthetic structural, fabric and thermochronological data suggest that tectonic extension is responsible for the exhumation of the lower plate and triggered syn- and post-tectonic magmatisms. A new cooling path for the lower plate rocks indicates that the lower platewas exhumed at a high rate of 2.0 km Ma-1 from before c. 128 Ma to 123 Ma and at a moderate rate of 0.35 km Ma-1 from 81 to 61 Ma. The rapid exhumation is consistent temporally with the sedimentation of terrestrial deposits of the Laiyang Group in the Zhucheng supradetachment basin. The post-kinematic granitic intrusions are dated as c. 122 Ma, which marks the cessation of rapid exhumation of the lower plate. Vast amount of andesitic volcanic rocks from 120 to 105 Ma in the Qingshan Group in the Zhucheng Basin may be related to the peak of lithospheric thinning in the Wulian area. These data highlight the importance of regional tectonic extension in the formation of the detachment fault zone and the exhumation of the Wulian mcc, and in triggering syn- and post-kinematic magmatisms. The scenario is consistent with the parallel extension tectonics model in which tectonic extension of the lithosphere led to detachment faulting in both the crust and mantle, resulted in the loss of some of the subcontinental roots, gave rise to the exhumation of the mccs, and triggered plutonic emplacement and volcanic eruptions of hybrid magmas. [ABSTRACT FROM AUTHOR]

The Mesozoic and Cenozoic deformations of the North Qiangtang terrane reflect a portion of the collisional tectonics of the Tethys Ocean, involving Late Triassic, Early Cretaceous and Cenozoic intraplate structures of shallow to superficial tectonic levels. The structural mapping of the Permian-Triassic structural layer indicates that the Mesozoic structural style is dominated by Early Cretaceous horizontal contractional deformations characterized by NW-SE-trending thrust faults and flexural-slip folds. These folds and thrusts were superimposed on Late Triassic buckle folds. Structural analysis of deformations of the Neogene and Quaternary sedimentary layers indicates that there was an obvious transition in the Cenozoic tectonic evolution of the North Qiangtang terrane, which can be divided into two deformation stages. In episode I (50-40 to 18 Ma), the crust experienced large-scale north-south horizontal shortening and vertical thickening shown by buckle folds and thrust faults. In episode II (18 Ma-present day), east-west passive extension formed conjugate strike-slip fault systems and pull-apart basins. During episode II, the Qiangtang basin was extruded eastwards, and a number of superficial north-south-trending buckle folds were formed. [ABSTRACT FROM AUTHOR]

Collapse of Antarctic ice shelves in response to a warming climate is well documented, but its legacy in terms of depositional landforms is little known. This paper uses remote-sensing, structural glaciological and sedimentological data to evaluate the evolution of the c. 25000 km2 George VI Ice Shelf, SW Antarctic Peninsula. The ice shelf occupies a north-south-trending tectonic rift between Alexander Island and Palmer Land, and is nourished mainly by ice streams from the latter region. The structure of the ice shelf is dominated by inherited foliation and fractures, and with velocity data indicates a largely compressive flow regime. The formation of a moraine complex at the margin of the ice shelf is controlled by debris entrained within foliation and folds. This englacial debris is of basal origin, and includes both local Mesozoic sedimentary and volcanic lithologies, and exotic crystalline rocks from Palmer Land. Folding of basal ice to a high level in the source glaciers on Palmer Land is required to bring the debris to the surface. These results have implications for understanding flow dynamics of ice shelves under compressive flow, and debris entrainment and moraine formation associated with palaeo-ice shelves. [ABSTRACT FROM AUTHOR]

The spatial and temporal association of post-collisional granites and lamprophyre dykes is a common but enigmatic relationship in many orogenic belts, including the Variscan orogenic belt of SW England. The geology of SW England has long been interpreted to reflect orogenic processes associated with the closure of the Rheic Ocean and the formation of Pangaea. The SW England peninsula is composed largely of Early Devonian to Carboniferous volcano-sedimentary successions deposited in synrift and subsequent syncollisional basins that underwent deformation and low-grade regional metamorphism during the Variscan orogeny. Voluminous Early Permian granitic magmatism (Cornubian Batholith) is considered to be broadly coeval with the emplacement of lamprophyric dykes and lamprophyric and basaltic lava flows, largely on the basis of geochronological data from lamprophyric lavas in Devon. Although published geochronological data for Cornish lamprophyre dykes are consistent with this interpretation, these data are limited largely to imprecise K-Ar whole-rock and biotite analyses, hindering the understanding of the processes responsible for their genesis and their relationship to granitic magmatism and regional Variscan tectonics. 40Ar/39Ar geochronological data for four previously undated lamprophyre dykes from Cornwall, combined with published data, suggest that lamprophyre magmatism occurred between c. 293.6 and c. 285.4 Ma, supporting previous inferences that their emplacement was coeval with the Cornubian Batholith. These data provide insights into (1) the relative timing between the lamprophyres and basalts, the Cornubian batholith and post-collisional magmatism elsewhere in the European Variscides, and (2) the post-collisional processes responsible for the generation and emplacement of lamprophyres, basalts and granitoids. [ABSTRACT FROM AUTHOR]

The West Orkney Basin is a poorly studied Palaeozoic and Mesozoic rift basin that overlies a highly seismicreflective Caledonian orogenic basement terrane. This study presents a novel approach of using 2D seismic data to map single intra-basement reflection packages and their relationship to overlying normal faults in the West Orkney Basin. It is demonstrated that the rift architecture of the West Orkney Basin is more linear with a prominence of relay zones relative to previous interpretations, and that rift structures form complex discordant and concordant relationships with pre-rift Caledonide basement structures. Restoration of basement fabrics to their pre-extensional geometry indicates that the reactivation of basement structures as normal faults has occurred only where the pre-extensional-dip of basement structures is greater than 30°. The relatively high density of relay zones mapped in the West Orkney Basin is proposed to be the result of the rift system forming a partially exploitative relationship with basement structure, where extension has been accommodated between segments that have or have not reactivated basement fabrics. [ABSTRACT FROM AUTHOR]

We propose a two-stage tectonic evolution of SE Afar in Djibouti leading to the complex development of highly asymmetric conjugate margins. From c. 8.5 to c. 2 Ma, an early mafic crust developed, associated in the upper crust with synmagmatic growth faults dipping dominantly to the SW. After an erosional stage, a new detachment fault system developed from c. 2 Ma with an opposite sense of motion (i.e. to the NE), during an amagmatic extensional event. In the Asal area, break-up occurred after c. 0.8 Ma along the footwall of an active secondary detachment fault rooted at depth above the lithospheric necking zone. This evolution suggests that flipflop detachment tectonics is developed during extension at passive margins, in connection with the dynamics of the melting mantle and the associated magma plumbing of the crust. [ABSTRACT FROM AUTHOR]

We present field observations from the Palaeoproterozoic volcano-sedimentary Tampere palaeobasin, where the primary structures have been exceptionally well preserved. We use the observations to construct a new tectonic model for the southeastern margin of the Tampere basin during its inversion and subsequent closure. The observed volcano-sedimentary and structural features suggest a change in the local structural style from thick-skinned inversion to thin-skinned thrusting, to accommodate the crustal shortening during basin closure. Furthermore, it is suggested that there is a genetic relationship between the interpreted palaeothrust and the sulphide-bearing schist horizons in the study area. On a more general note, the results imply that currently subvertical mineralized shear zones may have originally been gently dipping, further suggesting that the mineralized fluids may not necessarily have been sourced from great depths (i.e. from deep within the basement). [ABSTRACT FROM AUTHOR]

Age of Cretaceous rocks of the Maruszyna Succession, Pieniny Klippen Belt, Carpathians, based on calcareous nannoplankton. The age and microfauna of the Maruszyna Succession (Upper Cretaceous-Palaeogene), Pieniny Klippen Belt, Carpathians, Poland. We appreciate the attempts of [19] to investigate the geological structure of the Pieniny Klippen Belt (PKB) by means of seismic-reflection profiling, but in our opinion the authors' main conclusions contradict the results of previous studies without being constrained by the new data. 10a), neither identification of a particular PKB succession (other than the Czorsztyn Succession) in any PKB-derived olistolith, nor discrimination of such olistolith from a tectonic sheet of the Zlatne Succession, is possible in practice. [Extracted from the article]

Geochronology, structural and anisotropy of magnetic susceptibility data from the northern Vosges batholith, which belongs to the Northern Vosges-Mid-German Crystalline Rise arc, show contrasting emplacement modes of southern granodiorites and northern granites. The ENE-WSW-trending fabrics of granodiorites (346-334 Ma) are parallel to the metamorphic cleavage affecting the host rocks developed during regional compression. The NNW-SSE-trending fabrics of younger granitoids (c. 330 Ma) reveal an extensional emplacement mode, associated with a normal shear zone separating the two magmatic suites. Palaeomagnetism shows that the switch from a compressive to an extensional regime coincides with a regional counterclockwise rotation. The 330-325 Ma extension is further supported by palaeomagnetic and seismic data indicating southeastward tilt of the whole batholith. Finally the system is rotated clockwise without any structural overprint. Data from the Early Carboniferous northern Vosges magmatic arc and remote Bohemian Massif suggest that this evolution is valid for the whole eastern branch of the European Variscan belt, for which the following model is proposed: (1) Late Devonian-Early Carboniferous east-west shortening of the Variscides above the Rhenohercynian subduction zone; (2) axial NNW-SSE shortening of the assembled Variscan orogen associated with (3) 'internal' sinistral rotation of inherited Rhenohercynian transform faults and shortening of intervening blocks; (4) east-west extension and dextral 'external' rotation of blocks between dextrally reactivated transforms. [ABSTRACT FROM AUTHOR]

The Uþak-Güre basin is a NE-SW-trending extensional basin located in the northern part of the Menderes Massif, in western Anatolia. The Uþak-Güre basin contains a Lower to Upper Miocene volcano-sedimentary succession that records the unroofing of the metamorphic rocks of the Menderes Metamorphic Core Complex. We propose a new structural mechanism based on geological mapping and detailed kinematic fault analysis from each of the evolutionary phases. We also propose that north- to NE-dipping low-angle detachment surfaces define the basin boundaries and have identified three stages of deformation throughout the Miocene: the Early Miocene deformation phase (D2) is characterized by low-angle normal faulting (Simav detachment fault) in the supra-detachment Uþak-Güre basin, which marks the initiation of the extensional tectonics during the latest Oligocene; the Middle Miocene deformation phase (D3) refers to volcano-tectonic activities during accumulation of the Ýnay Group; the Late Miocene deformation phase (D4) is related to late Miocene tectonic activity widely responsible for deposition of the Asartepe Formations and uplift of the metamorphic rocks in the Uþak basin margin. In addition, we propose that the eastern part of the Menderes Massif was delimited by the 'Uþak-Muðla transtensional transfer zone' from Middle Miocene time throughout the eastern part of the Menderes Metamorphic Core Complex. [ABSTRACT FROM AUTHOR]

The structure of the Eocene Ainsa basin is dominated by kilometre-scale thrusts and folds that have trends at c. 70° to that of the main Pyrenean structures. Late uplift and erosion provide excellent exposure of this fold-and-thrust system and its growth strata. Field observations integrated with 2D seismic and well data support the 3D reconstructions presented in this paper. Structural reconstructions of pre- and syn-growth geometries contribute substantial improvements to the understanding of the structure of the area and provide a unique insight into the timing of Pyrenean structures. This study demonstrates that oblique features in the Ainsa basin can be grouped into two main systems: the La Fueba thrust system, an oblique-lateral ramp to one of the main Pyrenean thrusts, and the kilometre-scale folds of the Sobrabe system, a set of anticlines that grew as part of a relaying system of folds. In this study we propose a chronology of deformation based on the geometry of the basin fill, which has been used to frame the general tectonosedimentary evolution of the Ainsa basin. The relative timing of structures indicates that the La Fueba structures predate the Sobrarbe structures, which originated as orogen-parallel structures, and obliquity developed during the growth of these structures through clockwise vertical-axis rotation. [ABSTRACT FROM AUTHOR]

The evolution of tectonic flow has been studied in an exposed continental subduction system of the Variscan belt, the Malpica-Tui Complex of NW Iberia, where structural data are used to establish the kinematics and flow geometry during the whole deformation history. Structural analysis reveals reorientation of successive lineations by subsequent deformation events, and especially by late strike-slip tectonics. Analysis of the deflection patterns in the lineation map permits us to establish the original trend of lineations. The data expose the role of thrust and nappe tectonics and non-coaxial deformation in the hinterland of a collisional belt showing a dominant orogen-parallel lineation pattern. Following oblique subduction, contractional ductile thrusts transported and emplaced a part of the subduction system onto the adjacent mainland following vectors normal to the orogenic trend. However, the finite stretching lineation in associated recumbent folds is oblique to the orogenic trend and suggests overprinting by dextral shearing, probably owing to lateral components of the Gondwana and Laurussia convergence. Subsequently, extensional structures dismembered the tectonic pile, moving the pieces obliquely with respect to the trend of the collisional belt. Orogen-parallel strike-slip shear zones later produced major reorientation of the pre-existing tectonic fabrics towards their shear planes. [ABSTRACT FROM AUTHOR]

The Sierra Madre de Chiapas evolved in the vicinity of the triple junction between the Cocos, North America and Caribbean plates. The Sierra Madre de Chiapas tectonics reflects positive topographic growth along its main core and a northwards-directed collapse through a free border related to the Gulf of Mexico. Major exhumation and topographic growth occurred during the middle-late Miocene (16-10 Ma). Evidence for this deformational event is provided by fault activity, major stratigraphic unconformities along the Sierra Madre de Chiapas and the Tabasco coastal plain (i.e. southern Gulf of Mexico), major salt-related motion, northward progradation of the sedimentation and northward migration of the buried deformational front. During the Neogene, strike-slip deformation and its related exhumation migrated landwards from the western edge of the Chiapas massif complex to the Chiapas Sierra. Horizontal displacement along the main strike-slip faults in the Chiapas Sierra has been indirectly estimated to be between 30 and 43 km during the last 6-5 Ma, implying 0.5-0.8 cm a-1 of lateral accommodation. These values suggest that a significant amount of the motion transferred by the Caribbean and North American plates is currently being accommodated along the Chiapas area. [ABSTRACT FROM AUTHOR]

Recent studies on shallow-level arcuate intrusions have identified numerous examples of horizontal mineral fabrics. These are commonly interpreted as reflecting considerable lateral flow during magma emplacement, thus querying established 'semi-vertical' ring-dyke models. We question the recent lateral emplacement model proposed for the Palaeocene Slieve Gullion Ring-complex, NE Ireland, where the absence of steep fabrics in parts of the ring-complex has been used to support a shallow, semi-horizontal sheet intrusion mechanism. We argue that such simple flow models cannot be applied to explosive ring-fissure eruptions and that fabric data alone do not warrant rejection of the ring-dyke model. Moreover, the apparent 'absence of steep intrusive contacts' along the intrusion's perimeter is readdressed and we present numerous examples of outcrops (27) with steepsided geometries. The Camlough Breccias are reinterpreted as the product of gas-driven tuffisites injected along the active ring-fault (rather than of purely tectonic origin). Crucially, the porphyritic microgranite and porphyritic rhyolite ring-dyke rocks exhibit geochemical and petrographic signatures of contamination by the geographically restricted Palaeozoic Newry granodiorite and are best explained through crustal interaction vertically beneath the ring-complex. Subsequently, these silicic magmas rose into ignimbrite feeders along a caldera ring-fault system that was emplaced into near-surface vent-filling breccias. [ABSTRACT FROM AUTHOR]

Stratigraphic grain-size trends record tectonic and climatic signals. Here, we show how measurements of sediment calibre and clast lithology can be used to identify changes in accommodation space and sediment budget, using examples from Palaeogene syntectonic clastic deposits in the southern Pyrenees. We identify a mid Eocene interval of rapid grain-size fining, driven by local tectonic subsidence; a late Eocene interval of diminished local accommodation generation; and an Oligocene interval showing order-ofmagnitude lower grain-size fining rates, driven by increased sediment supply. Our results demonstrate that grain-size trends provide a powerful means to explore the tectonic and climatic boundary conditions governing sediment routing systems. [ABSTRACT FROM AUTHOR]

The Cenozoic tectonic history of NW Europe is generally attributed to some combination of three principal controlling factors: North Atlantic opening, Alpine collision and formation of the Icelandic mantle plume. Using constraints from the high-resolution Tellus aeromagnetic survey of Northern Ireland, we show that Palaeogene tectonics can be attributed to approximately north-south Alpine-related compression, forming NNW-SSE-trending dextral and ENE-WSW-trending sinistral conjugate strike-slip faults, with the latter defined by kilometre-scale displacements along reactivated Caledonian or Carboniferous faults. This tectonism was, however, punctuated by pulsed magmatic intrusive and extrusive events, including four distinct dyke swarms that are attributed to NE-SW- to east-west-directed plume-related extension. Although this evidence shows, for the first time, that north-south Alpine compression was periodically overwhelmed by the dynamic stresses and uplift associated with pulsed mantle plume-related deformation, associated strike-slip faulting may have controlled the locus of volcanic activity and central igneous complexes, and the location of sedimentary depocentres. [ABSTRACT FROM AUTHOR]

Geochemical data reveal the contrasting geochemical characteristics of the metasediments in the Jiepailiang and Bizigou formations of the Palaeoproterozoic Zhongtiao Group, North China Craton. High Zr/ Sc and SiO2/Al2O3 values and especially the evolved and uniform nature of Nd(t) values plus detrital zircon U-Pb ages and Hf isotopic signatures for the former are consistent with derivation from an evolved felsic source with sedimentary recycling signs. However, lower values of SiO2/Al2O3 and Zr/Sc, and higher contents of Fe2O3* and MgO for the latter indicate input of more mafic components. These geochemical characteristics, combined with the wide range of Nd(t) values, suggest that these rocks were derived in part from old continental material, dominated by felsic rocks of magmatic origin, and in part from a continental island arc, which accounts for the variable mixture of mafic components. These results suggest that the Zhongtiao Group was deposited after c. 2110 Ma, in a back-arc basin, behind an eastward-directed subduction system. Subsequent deformation and metamorphism reflect closure of the oceanic basin between the Eastern and Western blocks of the North China Craton, along the Trans-North China Orogen, contributing to amalgamation of the supercontinental Columbia. [ABSTRACT FROM AUTHOR]

Palaeogene sedimentary rocks exposed in West Java were derived from local volcanic sources and central Sundaland, the continental core of SE Asia. Detrital zircons from seven sandstone samples contain U-Pb age populations with ages of 50-80 Ma, 74-145 Ma, 202-298 Ma, 480-653 Ma and 723-1290 Ma. Late Cretaceous and Palaeogene zircons in Middle Eocene forearc sandstones are interpreted as derived from two spatially and temporally discrete volcanic arcs located in Java and Sulawesi respectively. In contrast, all other populations have a Sundaland provenance. Most Permian-Triassic zircons were derived from granites of this age in the SE Asian Tin Belt. Mid-Cretaceous zircons in all Upper Eocene and Lower Oligocene formations were derived from the Schwaner Mountains of SW Borneo. The differences in zircon populations reflect changing Sundaland sources with time. In the Middle Eocene, sediment was derived mainly from the Tin Belt. From the Late Eocene onwards a Borneo source became more important. Older zircon ages are from SE Asia basement that once formed part of Gondwana. Zircons also record the timing of microcontinental collision at the Java margin (c. 80 Ma) that halted Cretaceous subduction and probably resulted in the elevation of large parts of continental SE Asia. [ABSTRACT FROM AUTHOR]

Twenty-two wells on the Norwegian continental margin have penetrated underlying basement. We present U-Pb zircon, whole-rock geochemical, and Sm-Nd and Rb-Sr isotopic data from nine wells in the North Sea and Norwegian Sea with relevance to the offshore continuation of the Norwegian Caledonides, and their correlation throughout the Caledonian-Appalachian orogenic belt. Palaeozoic magmatism in the North Sea can be divided into two groups. The older group consists of 460 Ma calc-alkaline granites with evolved isotopic compositions, correlative with similar rocks in the Uppermost Allochthon. The younger group consists of a 430 Ma dacite and a 421 Ma leucogabbro, with less evolved isotopic compositions. In the Norwegian Sea, isotopically evolved granitic magmatism at 437 Ma and more juvenile dioritic magmatism at 447 Ma are correlative with magmatism in the Bindal and Smøla-Hitra Batholiths in the Uppermost Allochthon. Metasedimentary basement rocks from the North Sea and Norwegian Sea, dominated by Late Palaeoproterozoic and Mesoproterozoic grains, resemble rocks found in the Caledonides of Scotland, Greenland and Svalbard. The new data, along with studies elsewhere along the belt, suggest that similar rocks may exist along much of the orogen. [ABSTRACT FROM AUTHOR]

Structural data were collected on 1100 cone sheets and dykes with the aim of reconstructing the geometry of the complex, recognizing emplacement phases, and contributing to understanding this classical area and the evolution of cone sheets in general. Mean sheet dip angles are 40°, 43°, 47° and 50° in four sections transecting the complex. Sheet thickness ranges from a few centimetres to 5 m, with a dominant thickness of 1 m. Intrusion intensity ranges from 1% to 35%, increasing towards the central zone. Initial cone sheet emplacement occurred within a gabbroid pluton that was hot enough to amalgamate the sheets. Dykes striking N155-165° were then emplaced, followed by shallow-dipping cone sheets, dykes striking N135-145°, steepdipping cone sheets, dykes striking roughly east-west and, finally, dykes striking N150-165°. The NW-SEstriking dykes were emplaced during re-establishment of regional stresses, after perturbation by local magmainduced stresses when cone sheets were emplaced, interspersed with magma escaping horizontally from the volcano conduit to feed local dykes. Two successive magma chambers at different depths, with flat geometries and different volumes, may explain sheet architecture and location. The whole cone sheet system consists of a stack of parallel concentric sheets, rather than a model of convergence towards a single focus. [ABSTRACT FROM AUTHOR]

We constrain the timing and kinematics of normal faulting on Sifnos, Cyclades, Greece. Penetrative top-to-the-NE kinematic indicators associated with a shallow dipping foliation occur in the deepest tectonic unit (Greenschist Unit). Combined P-T analysis and Rb-Sr dating indicates that this deformation was under way by 29.4 ± 3.4 Ma at P-T conditions of c. 16 kbar and c. 550 °C, and continued to operate at least until 22.8 ± 0.2 Ma at P-T conditions of c. 8 kbar and c. 400 °C. The later top-to-the-south directed Sifnos Detachment developed at the top of the Greenschist Unit and cuts the top-to-the-NE structures. Zircon fissiontrack ages suggest that deformation on the Sifnos Detachment was largely terminated by about 13-10 Ma. Subsequent extension was accommodated by high-angle normal faults. Regionally the top-to-the-south detachment phase on Sifnos correlates with top-to-the-south extensional faulting on nearby Serifos, which started there at c. 15-13 Ma. Top-to-the-south extensional shearing on Ios to the SE commenced earlier at c. 19-18 Ma, suggesting that top-to-the-south extension propagated westward from Ios to Sifnos and Serifos, or that extension was partitioned into different top-to-the-south detachment systems that operated at different times. Collectively these top-to-the-south detachments are named here the South Cycladic Detachment System, which played a key role in the opening of the Cretan Sea forearc basin. [ABSTRACT FROM AUTHOR]

This work presents a methodological workflow for the 3D reconstruction of geological surfaces at regional scale, based on remote sensing data and geological maps. This workflow was tested on the reconstruction of the Anaran anticline, located in the Lurestan province, Iran. The remote sensing dataset used is a combination of Aster and Spot images as well as a high-resolution digital elevation model. The Aster images were processed using the Optimum Index Factor technique and pansharpened with the Spot technique for an easier 3D mapping. Structural dip data were acquired through analysis of the 3D mapped geological traces and analysed to divide the structure into cylindrical domains. Related plunge line orientation was used to project data along the structure, covering those areas where little or no information was available. Following the dip-domain concept a selected horizon is reconstructed and manually adjusted to the mapped traces. The reconstruction of the Anaran anticline demonstrates the applicability of this workflow when attempting to remotely reconstruct a reliable geological surface. The reconstructed surfaces clearly show the geometry of the Ilam and Asmari top horizons and the main faults affecting the anticline, allowing a consistent structural interpretation of the deeper structures. [ABSTRACT FROM AUTHOR]

Crustal shortening and thickening to c. 70-85 km in the Tibetan Plateau occurred both before and mainly after the c. 50 Ma India-Asia collision. Potassic-ultrapotassic shoshonitic and adakitic lavas erupted across the Qiangtang (c. 50-29 Ma) and Lhasa blocks (c. 30-10 Ma) indicate a hot mantle, thick crust and eclogitic root during that period. The progressive northward underthrusting of cold, Indian mantle lithosphere since collision shut off the source in the Lhasa block at c. 10 Ma. Late Miocene-Pleistocene shoshonitic volcanic rocks in northern Tibet require hot mantle. We review the major tectonic processes proposed for Tibet including 'rigid-block', continuum and crustal flow as well as the geological history of the major strikeslip faults. We examine controversies concerning the cumulative geological offsets and the discrepancies between geological, Quaternary and geodetic slip rates. Low present-day slip rates measured from global positioning system and InSAR along the Karakoram and Altyn Tagh Faults in addition to slow long-term geological rates can only account for limited eastward extrusion of Tibet since Mid-Miocene time. We conclude that despite being prominent geomorphological features sometimes with wide mylonite zones, the faults cut earlier formed metamorphic and igneous rocks and show limited offsets. Concentrated strain at the surface is dissipated deeper into wide ductile shear zones. [ABSTRACT FROM AUTHOR]

The Persian Gulf is part of an asymmetric foreland basin related to the Zagros Orogen. Few published studies of this basin and associated onshore areas include seismic reflection data. We present a seismic-stratigraphic interpretation based on marine 2D seismic data, which reveals the presence of two types of compressional structures within the basin: (1) faulted domes related to salt movement and the offshore trace of a NNE-SSW-trending dextral basement fault (the Kazerun Fault); (2) long-wavelength (16 km), lowamplitude (60 ms two-way travel time) folds relating to the advancing deformation front associated with the orogen. Thinning of age-constrained stratal units across structures related to the offshore trace of the Kazerun Fault implies a distinct pulse of uplift on this fault during the Maastrichtian. The geometry of growth strata across other intra-basin structures suggests a second, later stage of deformation, which began in the Middle Miocene. Thickening and folding of post-Middle Miocene stratal units towards the NE (i.e. towards the Zagros Orogen) is interpreted to reflect rapid loading, subsidence and compression related to southwestwards advance of the orogen. The results of this study have implications for the interaction between pre-existing structures and later compressional events both within the Persian Gulf and elsewhere. [ABSTRACT FROM AUTHOR]

Three crustal geological sections of the Campanian Volcanic Zone (Italy) were reconstructed by integrating basin architecture and deep well stratigraphies. In addition, mapping of the fault system and of large-volume ignimbrites was carried out. A linked fault system has been identified, which was responsible for asymmetric subsidence contemporaneous with the eruption of ignimbrites. Late Quaternary extension is characterized by a WNW-ESE stretching axis, NNE-SSW normal faults and reactivation of inherited structures. Structural, stratigraphic and palaeogeographical analyses reveal evidence for up to 750 m of subsidence, which has occurred at a mean rate of up to 4.9 mm a-1 over the past 154 ka. These rates suggest that extensional tectonics was responsible for the regional subsidence. A 6 km deep seismic reflector was associated with a magmatic reservoir underlying Campi Flegrei. By matching the structural and stratigraphic architecture with published geophysical and geochemical data a crustal tectonomagmatic model was constructed that displays high-angle faults that root into a low-angle detachment, which in turn roots into a deep sill-like magma reservoir. This model suggests the possible role of extensional faults in localizing magmatic activity, as faults controlled magma rise from deep to shallow reservoirs and to the surface during ignimbrite eruptions. [ABSTRACT FROM AUTHOR]

The Late Devonian Svalbardian event relates to the final activity in the Caledonian Orogen, and affected Devonian strata in Spitsbergen by major folding, oblique thrusting and basement uplift. In southern Spitsbergen, the Devonian deformation and the complementary, presumed Mid-Carboniferous Adriabukta event deformation caused uplift of the Sørkapp-Hornsund basement high or horst. This high is fault-bounded by Devonian sandstones and a questionably aged Early or Mid-Carboniferous mudstone unit (Adriabukta Formation). The Adriabukta Formation at Hornsund occurs in the core of a major syncline, with underlying Devonian strata in the west limb, all truncated in the footwall by a steep, east-side-up oblique-reverse fault. Mid- to Late Carboniferous rifting reversed the motion and produced rift-fill deposits, and these strata overlie the deformed Devonian rocks and the Adriabukta Formation with an angular unconformity. A similar basin architecture and major syncline bounded by a reverse fault with lateral movement characterize the Svalbardian deformation in the Mimerdalen-Pyramiden area at Billefjorden farther north. Similarity also exists between a Late Devonian unit (Plantekløfta Formation) at Mimerdalen and the Adriabukta Formation at Hornsund, and we question the previous interpretation of the Adriabukta Formation as Carboniferous. Rather, we suggest that the Adriabukta and Svalbardian deformation events may have been part of the same event. [ABSTRACT FROM AUTHOR]

In the frontal part of the Rhenohercynian fold-and-thrust belt (High-Ardenne slate belt, Germany), two successive types of quartz veins, oriented normal and parallel to bedding respectively, are interpreted to reflect the early Variscan compressional tectonic inversion of the Ardenne-Eifel sedimentary basin. Fracturing and sealing occurred in Lower Devonian siliciclastic multilayers under very low-grade metamorphic conditions in a brittle upper crust. A geometrical and microthermometric analysis of these veins has helped to constrain the kinematic and pressure-temperature conditions of both vein types, allowing the reconstruction of the stress-state evolution in a basin during tectonic inversion. It is demonstrated that bedding-normal extension veins, which developed under low differential stresses and repeatedly opened and sealed (crack-seal) under near-lithostatic fluid pressures, reflect the latest stage of an extensional stress regime. Bedding-parallel veins, which developed at differential stresses that were still low enough to allow the formation of extension veins, cross-cut the bedding-normal veins and preceded the regional fold and cleavage development. These veins show a pronounced bedding-parallel fabric, reflecting bedding-normal uplift and bedding-parallel shearing under lithostatic to supra-lithostatic fluid pressures during the early stages of a compressional stress regime. This kinematic history corroborates that fluid overpressures are easy to maintain during compressional tectonic inversion at the onset of orogeny. [ABSTRACT FROM AUTHOR]

Classically, the North Sea Chalk is interpreted as having been deposited under quiet, homogeneous pelagic conditions with local redeposition in slumps and slides. Recent observations of highly discontinuous reflection patterns on 2D and 3D seismic reflection data from the NW European Chalk Group have led to a revision of some general ideas of chalk deposition, with the suggestion that long-lived, contour-parallel bottom currents exerted a primary influence on the development of intra-chalk channels, drifts and mounds. This study proposes an alternative explanation for the formation of selected intra-chalk seismic and stratal discontinuities, interpreting these as being caused by gravity-driven processes that developed in response to intense syndepositional tectonics. Submarine mass-transport systems identified in the study area include largescale slumps, slides, debris flows and turbidites. The last occur in sinuous channel systems flanked by large master levees, with the channel fill exhibiting well-developed secondary banks and overbanks on the outer bends of the channel thalweg. This first documentation of channelized density-flow deposits in the North Sea Chalk has important consequences for the interpretation and prediction of redeposited chalk units, emphasizing at the same time the strength of detailed 3D seismic discontinuity detection for subsurface sedimentary-systems analysis. [ABSTRACT FROM AUTHOR]

The Pulo do Lobo Zone, which crops out immediately north of the allochthonous South Portuguese Zone in southern Iberia, is classically interpreted as a polydeformed accretionary complex developed along the southern margin of the Gondwanan parautochthon (Ossa-Morena Zone), during the late Palaeozoic closure of the Rheic Ocean. This closure was a major event during the amalgamation of Pangaea. U-Pb laser ablation inductively coupled mass spectrometry dating of detrital zircons from late Palaeozoic Devono- Carboniferous clastic units in the South Portuguese Zone and Pulo do Lobo Zone yield contrasting age populations and attest to the exotic nature of both zones. Detrital zircons from the South Portuguese Zone display populations typical of detritus derived from either Gondwana (Ossa-Morena Zone), or peri- Gondwanan terranes. In contrast, rocks from the Pulo do Lobo Zone contain populations consistent with derivation from Baltica, Laurentia or recycled early Silurian deposits along the Laurentian margin. An example of one such deposit is the Southern Uplands terrane of the British Caledonides. Taken together, these data can be reconciled by a model involving tectonic transport of a crustal fragment that was laterally equivalent to the Southern Uplands terrane between the allochthonous South Portuguese Zone and Gondwana as a result of an early Devonian collision between an Iberian indenter with Laurussia. [ABSTRACT FROM AUTHOR]

Determining detrital zircon U-Pb ages has become the method of choice for single- mineral-based provenance studies focused on the identification of potential source regions of siliciclastic sediments. Advances in microanalytical methods have significantly accelerated the acquisition rate of U-Pb ages, thus allowing for more statistically significant zircon age datasets to be acquired than previously. However, several studies have demonstrated limitations of relying solely on detrital zircon as a provenance proxy. To further assess the utility of this provenance indicator we measured U-Pb ages of detrital zircon derived from modern sediment collected from the French Broad River and its tributaries that drain portions of the Appalachian Orogen in southeastern USA. The results demonstrate that significant detrital zircon age variations occur along the length of the river. The age variations suggest that characterization of entire sedimentary formations by analysis of single samples may be misleading and that a multiple-sample approach is required. In addition, by incorporating high-magnification cathodoluminescence images with Th/U for each detrital grain, a more robust interpretation can be made regarding zircon source. [ABSTRACT FROM AUTHOR]

The origin and kinematic evolution of the Dorood growth anticline, a kilometre-scale fold located in the Iranian NW part of the Persian Gulf on the Zagros front, is discussed based on the geological interpretation of a seismic section and subsequent application of a number of techniques such as depth to detachment estimations, sequential cross-section restoration, estimations of crestal structural relief, shortening, wavelength and fold core area in various stages of fold amplification, and comparison between functions derived from the anticline analysis and functions for theoretical folds. Long-term fold growth rates indicate a slow amplification for c. 88.6 Ma punctuated by two periods of faster growth during the Late Cretaceous and from the Late Miocene to the present day. The kinematic evolution proposed involves vertical push related to reactivation of a basement fault during the oldest amplification event and fold tightening owing to buckling as a consequence of horizontal compression in the youngest event, both causing evaporite motion. Fold amplification took place by a combination of hinge migration and limb rotation. [ABSTRACT FROM AUTHOR]