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The Outer Hebrides Fault Zone is a major ESE-dipping reactivated structure within Lewisian basement gneisses of the Laurentian craton, northwest Scotland. Detailed mapping in South Uist reveals important new evidence that contributes to a better understanding of the kinematic evolution of the fault zone. Large quantities of pseudotachylite which characterize the fault zone on South Uist may in part be lithologically controlled, and therefore of little value in determining areas of greatest deformation and displacement. Only limited evidence is preserved for ductile and brittle thrust-sense movements along this portion of the fault zone. The tectonics of the fault zone on South Uist are dominated by structures associated with several episodes of pervasive top-down-to-the-SE to -ENE brittle extensional deformation, which are progressively overprinted by protophyllonitic and phyllonitic fabrics associated with top-down-to-the-E to -ENE extension. A series of late-stage high-angle normal faults record top-down-to-the-ESE to -ENE extension and cut the phyllonites. Fluid inclusion studies from syntectonic quartz veins constrain the conditions of phyllonite formation at 370 [+ or -] 20 [degrees] C. Field evidence suggests that this section of the Outer Hebrides Fault Zone may have been largely unaffected by sinistral strike-slip reactivation as reported along-strike to the north, suggesting both a varied and compartmentalized tectonic and evolutionary history along the length of the Outer Hebrides Fault Zone.

The Slieve League Peninsula of northwest Ireland lies on the western limb of a major orogenic strike-swing in which regional foliation trends have deviated from the northeast--southwest trends typical of much of Scotland, to west--east orientations. Across-strike coastal exposures on the western tip of the peninsula through Neoproterozoic Dalradian metasediments enable a detailed examination and analysis of the structural evolution of a Caledonian orogenic root zone which has been previously correlated with the Loch Awe Syncline of southwest Scotland. Minor structural development may be evaluated in terms of regional strain profiles and overprinting relationships. Over much of the area, a composite, steep northeast-southwest-trending S2-S3 foliation containing a gently southwest-plunging quartz mineral elongation lineation is the dominant fabric at outcrop, and is associated with MP2 almandine--amphibolite facies metamorphism. F2 folds are isoclinal with curvilinear hinges and similar geometry. They typically plunge steeply towards the southwest and display variable (dextral) or north-directed vergence, whilst minor F3 fold hinges plunge moderately towards the southwest and typically verge (sinistrally) towards the south. Major, composite D1-D3 tectonic slides are developed in the Argyll Group. Structural and stratigraphic relationships indicate that D1 induced large-scale reversals in younging across tectonic slides, resulting in reversals in subsequent F2 and F3 facing patterns. Tectonic sliding is associated with an intensification of strain demonstrated by increasingly intrafolial and curvilinear folding, together with extensional crenulations, sheared quartz pods and metre-scale asymmetric boudinage of metadolerites, all of which indicate dextral (D2) and sinistral (D3) shear. After unfolding subsequent folds (F4), this corresponds to top-to-the-north (D2) and top-to-the-south (D3) translations. D4 results in regionally northwest-verging structures, with minor crenulations and the S4 cleavage transecting fold hinges in an anticlockwise sense, suggesting a dextral component of deformation. The detailed kinematic data indicate that the overall geometry of this western, deep-level arm of the root zone is not a product of the classic mushrooming fountain of nappes model, but rather major interference between consistent northerly directed D2 thrusting and a later phase of southeast-directed (D3) retrocharriage (`back-folding') which intensifies towards the south.

The Karatau Fault System of southern Kazakstan forms a crustal-scale zone of strike-slip dominated transpressional tectonics which has undergone multiple phases and styles of deformation during a protracted history of reactivation from the Neoproterozoic to the Cenozoic. Ductile fabrics associated with dextral kinematic indicators are present in amphibolites along the Main Karatau Fault. The ages of the (possibly ophiolitic) protoliths and the ductile fabrics are not well constrained, but they are plausibly pre-late Riphean. Late Ordovician granites stitch thrusts and folds which deform late Riphean to Llanvirn clastics, preserved beneath a regional Late Devonian angular unconformity. This deformation may be related to a contemporary continental collision NE of the Karatau. Two phases of late Palaeozoic deformation affected the Upper Devonian and Carboniferous carbonate succession. The first phase is related to sinistral transpression along the Karatau Fault System, the second to dextral transpressional reactivation. The combination of these events produced a regional-scale dome-and-basin fold interference pattern. Similar polyphase deformation appears to have affected large areas of Central Asia and was possibly caused by the late Palaeozoic orogenies at Asia's margins, such as the accretion of Tarim and the East European Craton to Asia, and the closure of the Kazakstan Orocline. Normal faults in the Karatau are related to the formation of the Leontiev Graben, South Turgay Basin and the Yarkand-Fergana Basin in the Early to Mid-Jurassic, during renewed dextral slip along the Karatau/Talas-Fergana Fault. Late Cenozoic deformation is minor, and resulted in the uplift and incision of a Cretaceous-Palaeogene peneplain without a major tectonic overprint. Reversals in the sense of strike-slip dominated transpressive deformation across major fault systems results in transpressive inversion. This represents an ideal process with which to generate overprinting orthogonal fold systems, resulting in classic dome and basin interference patterns on a regional scale. Keywords: Central Asia, Kazakstan, Karatau, transpression, folds.

Drag zones are highly strained regions developed adjacent to the flanks of salt diapirs, and are produced when the sedimentary overburden is folded or rotated into steeply dipping attitudes sub-parallel to the diapiric walls. This case study focuses on a diapiric province on Cape Breton Island, Nova Scotia, where five Visean-age salt diapirs penetrate Upper Carboniferous (Namurian-Stephanian) conglomerates, sandstones, shales and coal seams. 2D marine seismic coverage extends over several diapirs thus allowing the drag zones studied onshore to be located relative to the adjacent diapir. The width of diapiric drag zones within the case studies varies from 70 m up to 500 m, with narrow drag zones reflecting the low mean competence of shales and siltstones which may have been shallowly buried and poorly lithified at the onset of diapirism. Broader drag zones are dissected by two sets of extensional fractures together with major faults, suggesting that the overburden was semi-lithified and displayed greater flexural rigidity. Overburden displaying high competency contrasts results in strain localization and partitioning, with pervasive granulation seams and minor faults developed in sandstones and bedding-parallel shears in coal and shale horizons. Drag zones are segmented by steeply outward-dipping faults associated with decametric, asymmetric drag profiles. These faults facilitate the upward movement of material and effectively expand the diapiric process into adjacent overburden via a newly termed process of lateral diapiric accretion. Keywords: Nova Scotia, salt tectonics, deformation.

The gently ESE-dipping Outer Hebrides Fault Zone may be traced for c. 170 km through the Lewisian gneisses of northwestern Scotland and defines broad, arcuate swings in strike from NE-SW to almost north-south. This study evaluates the kinematic evolution of the fault zone within the hinge region of such a strike swing exposed in the small isles north of Barra. New structural mapping of this area has concentrated on the geometry, kinematic significance and the relative age of different structural elements of the fault zone, and provides a comparison with the better known tectonics of the northern portions of the Outer Hebrides Fault Zone. Hitherto unrecognized top-to-the-NW ductile thrusting in this southern portion of the fault zone, coupled with abundant evidence of extensional reactivation and lack of sinistral strike-slip in phyllonites as reported further north, suggests that the present segmented and arcuate geometry is a primary feature of the fault system. The original thrust template governed the subsequent reactivation and relative importance of both late Caledonian strike-slip and extensional collapse components. Inherited structural architectures may thus provide geometric constraints on the nature and patterns of subsequent reactivation and tectonism. Keywords: Outer Hebrides, faults, reactivation, extension, deformation.

The careful recording of fold and fabric geometries permits evaluation of shear zone kinematics. Directions of shearing may be calculated via the Axial-planar Intersection Method (AIM) which incorporates analysis of minor fold vergence with axial-planar rotations. The geometry of sheath fold pairs may also be used to determine shear sense with sheaths closing in the transport direction typically displaying greater hinge-line curvature. Cross sections through the noses of sheath folds display cats-eye folds where the ellipticity of closures increases towards the centre of the eye, and bulls-eye folds where closures become less elliptical towards the centre, and reflect variations in bulk strain type from simple shear to constriction respectively. [ABSTRACT FROM AUTHOR]

Sheath folds are highly curvilinear folds, typically considered to develop by hinge rotation toward the transport direction during intense deformation. Most sheath folds are recognized on the centimeter to meter scale, with very few detailed studies of larger kilometer-scale structures. We here present evidence for a megascale sheath fold superbly exposed in the northern Oman Mountains. The Saih Hatat culmination consists of an exhumed high-pressure subduction zone with deep-level eclogites and garnet blueschists (As Sifah unit), epidote blueschists (Hulw unit) and carpholite-bearing metasediments (part of the ‘Upper plate’). Sheath folds are present at a variety of scales throughout the As Sifah, Hulw, and Upper plate tectonic packages. Curvilinear fold hinges along a 15-km-long profile outline the Wadi Mayh mega-sheath fold, which closes to the SSW and faces to the NNE. It consists of at least four secondary sheath folds with cross-sectional (y-z) eye folds measuring 200 m stacked on top of one another within Permian and Triassic shelf car bonates. These eye folds display highly elliptical geometries (Ryz > 5) and cat's-eye fold patterns consistent with simple/general shear. The sheath fold is enveloped by Ordovician and older rocks that do not show equal amounts of internal deformation. The upper bounding envelope is a detachment that has been subsequently sheath folded. The lower boundary of the sheath fold is the Upper plate-Lower plate detachment, which forms a major high-strain shear zone showing little vertical displacement but significant horizontal displacement. The sheath fold displays a SSW elongation (x axis) of at least 15 km and possibly up to 25 km, coupled with significant amounts of vertical flattening and WNW-ESE shortening. [ABSTRACT FROM AUTHOR]

Characterizing seismites is a key factor in understanding earthquake kinematics, dynamics and resulting hazards. In order to understand the kinematics and dynamics of seismites, we analyzed the anisotropy of magnetic susceptibility (AMS) of various seismite types of known origin, which have formed during paleoseismic activity along the Dead Sea fault (DSF) system. The magnetic lineation (L) and the shape of the AMS ellipsoid (T) of the seismites are presented in a new T versus L plot. Depending on the type of material, the seismites are distinguished according to the following characteristics. Injection structures are characterized by a nonlinear correlation curve; co-seismic fault-related damage zones lie on a common linear correlation curve; earthquake-triggered folds also show a linear correlation with those that have undergone major deformation and have low T and high L values. Breccia layers display a range of T and L values similar to that of primary sedimentary layers, implying that such seismites were formed by material deposited immediately after an earthquake. This new application of AMS provides an effective tool for resolving the kinematics and dynamics of a wide variety of seismites in soft-sediments. We outline a robust procedure to infer the seismite mechanism, which is helpful in recovering paleo seismic records in complex settings. [ABSTRACT FROM AUTHOR]