With the Haute Provence region of the external French Alps the internal zone Embrunais-Ubaye nappes rest with a shallow tectonic contact on the Dauphinois external zone. Beneath the Embrunais-Ubaye nappes, the external zone is deformed by south-west facing folds and by thrust faulting, the importance of which has only recently been recognised. The later emplacement of the Embrunais-Ubaye nappes towards the west into the area is generally thought to have been by gravity gliding. Detailed field studies within both the external zone and the Embrunais-Ubaye nappes has allowed the complex Alpine tectonic evolution of Haute Provence to be resolved. These studies have also shown the external zone deformation to be dominated by piggy-back thrust imbrication. A regional transport direction to the south-west and an overall external zone shortening of some 50% have been identified from the investigation of the three-dimensional geometry of thrust surfaces. The prominent south-west facing folds are found to have developed above a major decollement horizon and to have arcuate hinge lines concentric with the Castellane arc. Folds in general are in close association with thrust faults often developing passively as a response to thrust displacement. The Embrunais-Ubaya nappes consist of a number of thrust bounded structural units which have been emplaced into the region in an overstepping sequence. Detailed local mapping of the internal structure of these units has resulted in the identification of a major south-west directed shortening deformation of the Subbrianconnais zone dominated by thrust faulting. A restoration of Subbrianconnais structures gives an estimated north-east to south-west width for the Subbrianconnais zone of over 100km. Although the final emplacement of the Embrunais-Ubaye structural units may have been a superficial gravity gliding phenomenon, possibly as a result of tectonic uplift in the internal zones, the south-west directed thrust shortening of the external zone and probably the Subbrianconnais is the result of thrust displacements climbing from depth reflecting crustal shortening.

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The Gulf of Corinth, Greece occupies a young continental rift in a forearc setting where~ flank rift uplift has raised fossil shorelines, creating flights of marine terraces. These palaeoshorelines are used as reference markers from which uplift amount is quantified, and associated marine fossils are dated to establish a chronology. These results are analysed to test the proposed mechanism ofuplift in published models ofthe ofthe study region. Minor faults probably network the region with throws of>1 m to <30 m; although not significant in terms of crustal-scale tectonic processes, identification ofthese faults is necessary to prevent erroneous calculations of widespread crustal scale uplift from locally displaced fossil shorelines. The activity status of major faults is examined directly and by drainage analysis and revisions suggested for published work on the activity status ofthe major basin bounding faults; the on-shore Lower Loutraki and Kenchriae faults are inactive whereas the Upper Loutraki and off-shore Heraion are active and contributing up to -1 mm yr-l extension across the Lechaion Gulf. The average uplift rates of shorelines is 0.31 mm yr-l since at least MIS 9 (-340 ka), supporting the model of spatially uniform uplift, but the averaged rate smoothes temporarily variable uplift of 0.0 to 0.49 mm yr-l. There is no apparent correlation between temporal uplift rates and variation in crustal loading from eustatic sea level change and a lithospheric / mantle control on uplift rate is suggested. The basin inversion prior to -400ka suggests a significant change in the kinematics of the Lechaion Gulf at this time. The Perachora peninsula Holocene palaeoshoreline features includes marine notches fronted with level platforms and preservation of delicate shells, interpreted as evidence that uplift is by pulsed events.

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No description available.

Detailed analyses of fracture attributes developed in basement rocks associated with two, crustal-scale faults, have enabled the characteristics and evolution of the fracture system geometry to be documented quantitatively. Data sets of fracture attributes have been collected adjacent to faults within the Møre-Trøndelag Fault Complex (MTFC) in Central Norway, and the Walls Boundary Fault System (WBFS) in Shetland. Both structures are of Palaeozoic origins and contain multiply reactivated fault strands that extend offshore to bound several hydrocarbon-rich sedimentary basins of Mesozoic-Cenozoic age along the North Atlantic margin. Fracture characteristics from the MTFC were measured within one dominant lithology (acid gneiss) and therefore each data set of fracture characteristics is directly comparable. A number of different fracture parameters were measured using either 1-D or 2-D techniques and were collected over four data scales. These data indicate different signatures for the two main faults within the MTFC: the Verran Fault (VF), a highly reactivated structure and the Hitra-Snasa Fault (HSF), which has experienced little reactivation, and also for a smaller, kinematically simple fault, the Elvdalen Fault (EF). The parameters measured are the exponent values from exponentially distributed spacing and length data sets, mean fracture spacing, fracture density, mean fracture length, fracture intensity and fracture connectivity (defined by the numbers of fractures and nodes per cluster, fracture cluster length and the number of nodes per unit area). Based on analyses of these parameters, the VF is characterised by a tall peak in values (or trough for measurements such as mean length and mean spacing), with a wide zone (-500m) of above-background values to the NW of the Verran Fault Plane. The HSF on the other hand is characterised by a tall and narrow zone of above-background values (or below for mean spacing and mean length parameters), which decrease to background levels within 100m either side of the Hitra- Snasa Fault Plane. The EF is also characterised by a narrow but shorter peak in above background values, where the height of the peak is less than half that associated with the VF and HSF. These different signatures are most likely to be related to the differing reactivation histories between the three faults. In addition, the VF shows widespread evidence for multiple phases of fluid-related alteration and mineralisation, suggesting that the fracture network characteristics play an important role in controlling fluid flow in these otherwise relatively impermeable basement rocks. The data sets of fracture characteristics collected adjacent to four faults within the WBFS display general trends consistent with the changes in fracture attributes observed adjacent to faults within the MTFC. However, the results are considered to be less reliable. Firstly, the data sets were collected within seven different lithologies, meaning that the fracture attributes must be considered separately, resulting in small data sets compared to those collected from gneisses within the MTFC. In addition, the four faults studied all have different kinematic histories. The findings of this study show that detailed studies of fractures may potentially be used to fingerprint fault reactivation and enable its' recognition in the subsurface.

It is commonly observed that ancient faults or shear zones can become reactivated again and again, either within the same or even superimposed tectonic episodes, yet millions of years apart. Rocks of the continental crust show such effects particularly well, owing to their longevity, because through their buoyancy, continental rocks resist recycling back into the Earth's mantle over long time-scales. The Møre Trøndelag Fault Complex (MTFC), Central Norway and the Walls Boundary Fault (WBF), Shetland, were studied to elucidate the kinematic, geometric and textural evolution, in order to assess fault linkages, fault-rock preservation styles and the controlling factors on fault reactivation The WBF is a crustal-scale, reactivated fault that separates distinctively different basement terranes; the Caledonian front to the west from Dal radian type rocks to the east. The WBF initiated as a late-Caledonian sinistral strike-slip fault (c.l00-200km offset) associated with the development of mylonites and cataclasites. Dextral strike-slip reactivation (c.65km) in the Permo-Carboniferous related to inversion of the Orcadian Basin and led to the development of cataclasite and fault gouge assemblages. Later dip-slip and finally sinistral strike-slip (c.l5km. Tertiary?) reactivation were localised within earlier formed fault gouges. The ENE-WSW-trending MTFC in Central Norway is a 10-20 km wide, steeply dipping zone of fault-related deformation. The MTFC has a prolonged and heterogeneous kinematic history. The complex comprises two major fault strands: the Hitra-Snasa Fault (HSF) and the Verran Fault (VF). These two faults seem to have broadly initiated as part of a single system of sinistral shear zones during Early Devonian times (409+12 Ma). Sinistral transtensional reactivation (dated as Permo-Carboniferous; 291 + 14 Ma) of the ENE-WSW-trending HSF and VF led to the development of cataclasites and pseudotachylites together with the formation of N-S-trending faults leading to the present-day brittle fault geometry of the MTFC. Several later phases of reactivation were focused along the VF and N-S linking structures during the Mesozoic probably related to Mid- Late Jurassic/Early Cretaceous rifting and Late Cretaceous / Early Tertiary opening of the North Atlantic. Based on apparent offshore trends, it has been suggested that the MTFC and the WBF may have been linked at some stage during their evolution and subsequent reactivation. This is consistent with the present study, as early Devonian movements along both the WBF and the MTFC are sinistral. Differences in the magnitude, dynamics and senses of displacement in the Permo-Carboniferous, however, seem to militate against linkage of these faults in the late Palaeozoic. There is no compelling evidence for direct Mesozoic or Tertiary linkage, although both structures were reactivated to some extent during these times. It seems that the formation and reactivation of the WBF and MTFC were associated with broadly similar regional tectonic processes and therefore, to some extent, share similar kinematics. Although both the MTFC and the WBF show clear proof of repeated reactivated, superficially similar geometries or alignments should not be used as a basis for correlating structures, in the absence of direct kinematic evidence. Displacements along the MTFC and the WBFZ are repeatedly localised along the earlier formed fault rocks, suggesting that these fault rocks are intrinsically weak compared to the surrounding rocks. A complex interaction exists between the geometrical properties of the fault network and fault-zone weakening mechanisms operative within fault rocks around the level of the frictional-viscous transition. Together these factors control fault reactivation in the long term. In the case of reactivated, sub-vertical, strike-slip fault zones the preservation and exhumation of these fault rocks both depend on the architecture and magnitude of later reactivations.

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The timescale and process of magma storage and transportation at continental rifts is not well understood. Extension, fault structures and hydrothermal systems all influence magma storage, volcano deformation and volatile emissions at rift volcanoes. This thesis uses a multidisciplinary approach to study these processes within the Kenyan Rift (KR), combining satellite and ground-based observations of deformation, structure and degassing. Using satellite radar (InSAR) , I show diverse deformation histories exhibited by 5 deforming volcanoes, including: coupled magmatic uplift-hydrothermal subsidence; longterm magmatic subsidence; and hydrothermal subsidence. At individual volcanoes, deformation of discrete magma lenses is connected by a crystal-melt mush, and by studying clustered volcanoes; I place geophysical constraints on its lateral extent at 30 x 15 km. A soil CO2 survey at Longonot volcano shows that passive degassing is controlled by volcanic structures. The total CO2 degassing is magmatic in origin and estimated at 10-1 - 102 t d -1; but emissions are likely modified by a hydrothermal system. By extrapolation, I conclude that restless rift volcanoes may emit globally significant quantities of C02 by passive degassing. The northern and southern segments of the KR are found to be in orthogonal and oblique extension respectively. Southern calderas are aligned NE-SW, lying oblique to recent rift faults but aligned with pre-existing rift faults suggesting that pre-existing structures control the location and dimensions of mid-crustal magma reservoirs, whereas smaller cones and vents tend to be aligned along currently active structures. This thesis demonstrates that pre-existing and currently-active structures influence magma storage, transfer and volatile emissions at varying crustal levels and that isolated crystal-melt mush regions likely exist beneath all volcanoes, but do not extend along the entire rift system. Understanding the magmatic-hydrothermal systems is a key priority for future study and hazard assessment.

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