The emplacement of the end-Cretaceous to Palaeocene magmatic arc in the Precordilleria of Vallenar occurred during a fundamental switch in deformation style of the upper plate of the Andean margin from extension/transtension to contractional deformation. This switch in regional tectonics is shown by combining precise [sup]40 Ar/[sup]39 Ar geochronology with microstructural and structural field observations that demonstrate a direct link between the ages for emplacement, cooling and subsequent deformation of end-Cretaceous to Palaeocene magmatic arc. The emplacement of the Las Campanas pluton during upper plate extension, 70.6 ± 1.3 Ma, was accommodated by a floor-subsidence mechanism that normally reactivated the east-dipping Agua de los Burros extensional growth fault. This generated a steep upper amphibolites-facies, syn-plutonic, brittle-ductile, dip-slip shear zone that is located on the pluton's western side and exhibits a consistent east-down sense of shear. [sup]40 Ar/[sup]39 Ar hornblende and biotite ages from the pluton interior and shear zone are the same, within error, which demonstrates rapid cooling of the pluton. The emplacement of the Chehueque pluton, 69.1 ± 0.62 Ma to 66.75 ± 0.62 Ma was also accommodated by floor-subsidence mechanisms during upper plate extension, but a switch from regional extension/transtension to contraction can be occurred prior to cooling. The Chehueque pluton has an upper-amphibolite facies brittle-ductile shear zone along its western margin, similar to that of Las Campanas. However, this shear-zone is much wider and shows both east-down and east-up sense of shear indicators. This duality in shear sense is attributed to two phases of deformation during the emplacement and subsequent cooling in this part of the Palaeocene magmatic arc. The initial extensional phase is directly linked to floor-subsidence emplacement mechanisms that generated passive down-bending in the host rocks, towards the pluton. This was closely followed by deformation linked to the initial stages of regional contraction that superimposed an east-up sense of shear; these kinematic indicators can be matched between the host rocks and pluton. This difference in syn-plutonic deformation style and the ages of the Las Campanas and Chehueque plutons therefore constrains the time of the switch from regional extension/transtensional deformation to contractional deformation to a period of c. 4 Myr in latest Cretaceous to early Palaeocene time in the Precordillera of Vallenar.

The Eastern Alps are a belt of major deformation formed by the convergence and collision of Europe with the Adriatic microcontinent. A major tectonic boundary can be defined between the dominantly continental Austroalpine domain, which represents the northerly fringe of Adria; and the Pennine oceanic domain, which once lay between the Austroalpine domain and Europe. This boundary is one of the key areas for unravelling the convergent tectonic history of the Eastern Alps. The main emphasis of this thesis is on the deformational behaviour of the Austroalpine domain and its implications for the regional tectonic processes that were instrumental in forming the structure of the Eastern Alps. The data for this work are derived from structural and metamorphic studies in the S.E. Tauern in profiles straddling the boundary, and a review of the published regional geology. The first manifestation of convergence is the development of a broad zone of thickened crust, including both Pennine and Austroalpine units, which underwent Cretaceous burial metamorphism. Postdating this thermal event in the Austroalpine domain, there was a further phase of regional deformation, which caused substantial reduction in the structural thickness. To the south of the Tauern Window, a study of the associated kinematic development gives a minimum estimate of 10km for this thinning, which radiometric dating suggests took place while convergence was still active. A comparable 10km post-metamorphic thinning is suggested throughout the Austroalpine domain in the Eastern Alps by the shortfall in the overburden compared to the depth of burial indicated by the Cretaceous metamorphic conditions. Major extension in a dominantly convergent tectonic setting cannot be accounted for by the paradigm of plate tectonics and implies that body forces acting on the thickened crust of the destructive margin were a major driving force for deformation.

Abrupt lateral changes in thrust geometry occur in many mountain-building fold-thrust belts. Whilst many works have dealt with palinspastic reconstructions and transport-directionparallel balanced cross-sections, far fewer show a full three-dimensional architecture, or examine how lateral variations in thrust architecture can be linked via cross-strike discontinuities or transverse zones. Systematic alignments of lateral structures are suggested to be related to kinematic responses to irregularities generated across pre-existing, sometimes reactivated, sub-décollement basement faults, pre-thrusting cover strata deformation above basement faults, development of duplex structures / antiformal stacks, and / or along-strike variations in mechanical stratigraphy. New cross-strike discontinuity / transverse zone identification methodologies developed within this research incorporating thrust ramp-flat alignment analyses and branch-point, cutoff point and fault-tip point analyses, together with a variety of previously utilised identification techniques, allow spatial alignments of lateral structures to be determined. New methodologies help to better characterise the pre-thrust template and assess that template’s capacity to control subsequent lateral thrust geometries on a variety of scales during allochthon formation within two contrasting fold-thrust belts, the linear Moine Thrust Belt and the oroclinal Cantabrian Thrust Belt. Within the Kinlochewe region of the Moine Thrust Belt, a distinct compartmentalisation is identified across the Loch Maree Fault (LMF). A thrust dominated region of overturned Torridonian / Lewisian, overlying a right-way-up Cambrian succession can be clearly identified on the northern wall of the LMF, compared to a fold-and-thrust dominated section on the southern wall. Compartmentalisation is suggested to be a response to a step in basement that generated a transport-parallel lateral ramp or sidewall during thrusting. A series of potential cross-strike discontinuities / transverse zones are identified within the Cantabrian Thrust Belt. Structural disparities are suggested to have developed as a result of along-strike variations in stratigraphical thickness and regional transport during a multiphase oroclinal development.

Seafloor spreading at mid-ocean ridges is accommodated by a combination of magmatic accretion and tectonic stretching of the lithosphere. Recent investigations of mid-ocean ridges show evidence for large-offset normal faults or detachments that accommodate a significant portion of the plate separation. Once thought of as rarities along the global spreading system, detachment faults are now considered to play an integral role in seafloor spreading at slow- and ultra-slow-spreading ridges. Estimates of the proportion and extent of tectonic spreading however vary widely; some authors suggest as much as 50% of the Mid Atlantic Ridge is underlain by active detachment faults. The lack of consensus is in part a consequence of the difficulty in documenting the extent of tectonic stretching and detachment faulting, especially from surface morphology alone. On the modern seafloor tectonic activity may potentially be greatly under-estimated if lava flows blanket and obscure the faulting below. This thesis addresses the question of whether and how such ‘hidden tectonics’ may be accommodated beneath the seafloor by means of a field-based study of the Troodos ophiolite, Cyprus, which is believed to be a slow-spreading ridge analogue. My interdisciplinary approach utilises structural mapping, palaeomagnetism and geochemistry to investigate the spreading structure and mechanism of accretion of the Troodos upper crust. I document significant extensional faulting and rotation within the crust above a detachment fault at the level of the sheeted dyke complex, yet show that the lavas at the surface are sub-horizontal and unaffected by the deformation beneath. Unconformities in the lava section demonstrate progressively greater rotations deeper in the extrusive pile, controlled by tectonic stretching and tilting of the underlying dykes, rather than rotation by loading and/or subsidence within the lava pile as previously proposed. Ponding of late, primitive, low viscosity lava flows against normal faults on the seafloor thickens the extrusive sequence substantially and obscures the faulting below. The study shows that syn-tectonic volcanism is an effective mechanism for filling active half-grabens at slow-spreading ridges. Tens of percent tectonic stretching at depth may be completely masked at the surface by syn-tectonic lava extrusion. Such ‘hidden tectonics’ may be far more common at modern mid-ocean ridges than commonly supposed.

The aim of this thesis was (i) to develop analytical methodologies and a workflow to identify the ocean-continent transition (OCT) and to locate the continent-ocean crustal and lithosphere boundaries (COCB and COLB) at continental rifted margins and (ii) to apply these methodologies and workflow to six cross-sections of the Northeast Brazilian rifted margin. The six cross-sections were taken from the margin segments Almada-Jequitinhonha, Jacuípe, Sergipe, Alagoas and Pernambuco and were constructed using seismic reflection sections from the borders of sedimentary basins to the oceanic crust. The OCT of the Northeast Brazilian rifted margin is complex due to variable extrusive and intrusive magmatism and antithetic tectonics. COCB locations interpreted on seismic reflection data have been tested with those determined using the analytical methodologies and workflow developed in this study. The workflow comprises: 1) the determination of sediment-corrected basement depth profiles, 2) the analysis of the residual depth anomalies of the oceanic crust and its extrapolation into the rifted margin, 3) the gravity inversion of the Moho with crustal thinning determination and 4) the inversion of lithosphere thinning using subsidence analysis. The calibration of the gravity inversion through the fit of the residual depth anomaly in unequivocal oceanic crust is a new approach to determine the reference Moho depth in areas without seismic refraction data. The Almada-Jequitinhonha OCT corresponds to a region of antithetic faulting and low free-air gravity anomaly. The Jacuípe OCT corresponds to a region of development of normal magmatic addition, expressed in the seismic sections as seaward-dipping reflectors, and has a relatively high free-air gravity anomaly. Although the Jacuípe margin represents a narrow rift, this margin seems to be wider and offshore syn-rift sediments are either not imaged or have been eroded. The Sergipe margin is interpreted as being magma-poor during rifting and evolved to slightly magma rich in the early post-rift. The OCT corresponds to a region of continental crust thinner than the adjacent oceanic crust, with antithetic faulting and a stable free-air gravity anomaly. The Alagoas margin is interpreted as being magma-poor during rifting and evolved to normal magmatic addition in the early post-rift, while the Pernambuco margin is interpreted as being slightly magma-rich. The OCT of both margins corresponds to a region of synthetic and antithetic faulting with a low free-air gravity anomaly. The predicted COCB and COLB locations for each cross-section tend to be similar to each other. Only minor differences between the crustal and lithosphere thinning profiles have been observed. The rifted margin width, measured along the cross-sections, does not vary significantly in the South between Almada-Jequitinhonha and Sergipe North, ranging from 110 to 130 km. While, in the North between Alagoas and Pernambuco it is wider, around 170 km. The Northeastern Brazil margin varies from magma-poor in the Almada-Jequitinhonha region to slightly magma-rich in Sergipe and Pernambuco, both probably affected by the Santa Helena Hot Spot. The workflow developed here can be considered successful in locating the COCB and COLB positions and in identifying the OCT in the cross-sections across the Northeast Brazil margin and can be applied to other rifted margins without seismic refraction data.

The Istria ‘Depression’ or sub-basin of offshore Romania lies at the intersection of the trans-European Tornquist-Teisseyre ‘Zone’ and the Black Sea back arc basin, just outboard of the East Carpathian orogenic welt. Its Late Mesozoic-Cenozoic succession records an extraordinary cpolyphase history of subsidence and sedimentation, interrupted by several quite spectacular 2nd /3rd order erosional unconformities, reflecting the interplay between these teetonic domains. The unconformities divide the succession into a number of stratigraphic sequences. The sub-basin first developed as a transtensional rift in the Triassic-Early Jurassic, evolving into a narrow oceanized trough in later Jurassic. This was tilted west during the Early Cretaceous by uplift and rifting in the Western Black Sea and the residual Late Jurassic topography was filled and buried by a west-facing clastic-evaporite wedge. Late Aptian- Albian post-rift subsidence and spreading in the Western Black Sea imposed a strong easterly tilt, encouraging the partial evacuation of its Early Cretaceous sedimentary fill by gravity-driven mass wastage. The incised valley topography was subsequently buried in the later Cretaceous and Early Cenozoic. During the mid-Late Cenozoic, the Black Sea basin experienced intermittent periods of partial to complete isolation from the world ocean and significant base-level drawdown. The first major sea level fall occurred in the Eocene when the Istria ‘Depression’ was deeply incised, to be healed by Oligocene shales during the subsequent rise. Yet another period of drawdown and exposure occurred in mid-Miocene With extensive shelf margin mass wastage and erosion, followed by reflooding and deposition of a transgressive backstepping sequence in mid-late Miocene. Messinian drawdown in the Mediterranean caused a further period of isolation and falling base level. The shelf margin Was again exposed and experienced widespread mass wastage and slumping. A marine connection was re-established in late Messinian. Rising sea level eroded the earlier slumped sequence and the margin was healed by a lowstand prograding wedge in late Miocene-early Pliocene. This was followed by shelf sedimentation in the Plio-Pleistocene periodically interrupted by canyon incision events, testifying to continued climatically or tectonically- imposed base level fluctuations. Several direct and indirect tectonic factors were responsible for valley/canyon incision within the Istria Depression and erosion of the Romanian Black Sea shelf margin. These include; (1) the local structural framework (2) direct tectonic uplift and tilting and (3) more indirect tectonically imposed isolation encouraging significant base level falls.

Three volumes of seismic data, together with longer 2D lines, well data and regional gravity and magnetic data, have been used to investigate the structure and formation of the Sabratah Basin, thought to be formed as an extensional basin between the Libyan Coastal fault system and South Graben Fault Zone during the Middle to Late Triassic. The study has investigated the crustal structure, subsidence history and structural evolution of the basin. Tectonic subsidence was calculated by assuming 1D Airy isostatic equilibrium using a total of 20 wells. The result shows two rifting events. Rift event 1 started in Middle Triassic and continued until the end of Triassic (228-200Ma). Rift event 2 started in the Upper Cretaceous no earlier than (100 Ma). The depth to the Moho has been calculated by the methods of Airy- Heiskanen model, Warner (1987), 2D gravity model and deep seismic profiles. The result shows crustal thinning under the Sabratah Basin. The two 3D seismic volumes within the northern part of the Sabratah Basin reveal the presence of en-echelon folds aligned ENE-WSW (N75°) and two grabens trending N150° separating the folds. Three trends of faults were recognised in the study area N150°, N110° and N60°. The seismic interpretation suggests that the folds probably developed by dextral transpressional shear during the Alpine compressional phase between Africa and Europe as right lateral movement. This motion was accompanied with E-W transcurrent fault which probably terminated in a horsetail composed of a fan of normal faults in Bouri block. Diapiric phenomena related to Upper Triassic Lower Jurassic salt affected the western part of the study area. The salt structures have distinct E-W trends. Thus, salt movements appear to be associated with E-W trending strike-slip faults. Movement of Upper Triassic Lower Jurassic salt began in the upper Cretaceous and forms a decollement which acts as glide-plane for series of listric faults separating listric extensional structures above from planar extensional structures below the base Jurassic.

This research project uses high-quality seismic data from the Ottar Basin offshore Norway, Espírito Santo Basin offshore Brazil and Taranaki Basin offshore New Zealand. It investigates the geometry of multiple families of extensional faults and the effect(s) of fault growth on their seal competence. The main aims of this thesis are to investigate: a) the relationship between fault growth and deposition, b) the influence of fault reactivation in the compartmentalisation of strata around salt structures, and c) three distinct study areas as potential zones for enhanced fluid migration and seafloor seepage. Structural controls on three distinct petroleum systems were analysed based on the interpretation of the 3D geometry of seismic horizons, the mapping of fault displacements and throw distributions, and by modelling distinct faults taking into account present and past tectonic stresses. The geometry and kinematics of the Samson Dome, offshore Norway, were investigated to propose a new evolutionary model for this salt structure, and to assess the timing(s) of salt uplift, salt collapse, and reactivation of adjacent faults. Faults were investigated using detailed displacement analyses and 3D models. Fault modelling took into consideration present-day in situ stresses, and also relative paleostresses. The results demonstrate an evolution occurring in three distinct stages, which were thoroughly discussed in this thesis. The Samson Dome is a structure where structural compartmentalisation is more important at depth, with dip-linked reactivated faults being preferential paths for fluid migration at shallow depths. However, their seal competence is enhanced 1100 ms below the sea floor, below which fluids can be trapped. iv The geometry of fault families adjacent to distinct salt structures was assessed in the Espírito Santo Basin, offshore Brazil. Halokinesis is recorded from the Late Aptian to the Early Eocene, for four distinct salt structures, and controlled fault geometry and fluid flow patterns. The results in this thesis indicate a decrease in the seal competence of faults generated close to the studied salt diapirs. A conceptual model proposes that salt structures are linked by corridors of reactivated faults, which comprise preferential fluid-flow pathways from the South to the North-Northwest. The Parihaka 3D survey of the Taranaki Basin was used to investigate the geometry of submarine channel systems formed in association with the reactivation of fault segments during the opening of the Northern Graben, a structure with regional expression offshore New Zealand. Three main drainage types were described around the Parihaka Fault. The results in this thesis suggest that the larger displacements observed led to the formation of two depocentres to the NE of the study area, which were progressively filled by submarine-channel and prograding deltaic units. New results from this thesis include the assessment of the evolution of the Samson Dome, SW Barents Sea, and any controls of fault reactivation on the generation of structural compartments above this structure. This approach resulted in the recognition of the Samson Dome as a smaller seepage structure than previously considered in the literature. In the Espírito Santo Basin, faults reactivated by dip-linkage adjacently to salt diapirs and salt walls are the structures most favourable to record fluid leakage. In the Taranaki Basin, submarine channels may not use relay ramps between reactivated fault segments to reach hanging-wall depocentres. The results in this thesis can also be extrapolated to petroleum systems developed on continental margins worldwide.

Understanding fluid flow in fold and thrust belts has the potential to offer enormous insight into hydrocarbon accumulations in regions dominated by such structurally complex settings. Thrusting episodes can be key in creating a complete petroleum system, aiding maturation through burial, developing trapping scenarios, creating pathways for flow though juxtaposition and acting as conduits for flow connecting source to reservoir. The ability to model thrust and fold belts is limited due to the complex nature of threedimensional modelling of thrusts. However recent advancements is structural modelling software have allowed the representation of a stratigraphical surface in two depth locations at a single surface location enabling better realisations of overlain strata in thrust zones. This work simulates the migration of hydrocarbons through fold and thrust zones using new Earth Models of the southern Sub Andean in Bolivia, created from seismic interpretation and well data analysis, and develops a new modelling workflow using multiple geological modelling applications. The migration pathways have been simulated in three dimensions using invasion percolation hydrocarbon migration modelling techniques developed by the Basin Dynamics Research Group at Keele University. These techniques allow the investigation of the relationship of stratal flow properties across thrust blocks. The methodology employed allowed the geological uncertainty of the prospect to be evaluated for hydrocarbon trapping potential, through repeatable simulations where the location point of hydrocarbon source could be controlled. The results of the modelling work provides an insight into the evolution, maturation and potential accumulation of fluids in the Bolivian case study, and has produced a predictive approach to analysing fluid flow and accumulation applicable to other hydrocarbon systems as well as application in other fields considering fluid migration pathways and accumulation.

The collapse of host sediments at the crests of salt anticlines is associated with the devel- opment of hydrocarbon traps in salt overburden rocks, and stratigraphic traps in palaeo- valleys incising salt wall crests. The capacity and integrity of these traps are controlled by complex spatial variations in the geometry of collapse structures, and are difficult to char- acterise using traditional sub-surface datasets. An in-depth understanding of the structural styles that control salt wall collapse, particularly at the ‘sub-seismic’ scale, is essential so that meaningful interpretations of potential prospects can be made based on sub-surface data. The exceptional exposure and preservation of a number of collapsed salt anticlines and re- lated structures within the Paradox Basin, Utah and Colorado, U.S.A., provide an ideal op- portunity to study the geometry and development of salt-related collapse structures. This study combines three-dimensional seismic data from the U.K. Central North Sea with de- tailed structural mapping of exposed structural analogues from the Paradox Basin. The results are used to identify and characterise the range of structural geometries that result from salt anticline collapse, and to elucidate controls on their development. Collapse geometries range from ductile down-warping of the overburden, creating axial synforms, to brittle deformation, creating graben and half-graben structures. Where col- lapse is brittle, half-grabens form the principle structural element of salt anticline collapse structures. Graben-like structures are generated through subsidence of the hanging-wall an- ticlines associated with half grabens, or within areas of interaction between kinematically- linked, oppositely-dipping half-grabens. Accommodation structures between oppositely- dipping half-grabens are associated with structural lows, and contribute to compartmental-isation of potential reservoirs within the overburden. The summary models presented here can be used to guide seismic interpretation within complex, salt-controlled basins, and to identify the potential risks associated with structural traps formed by salt anticline collapse.