Studies have shown that faults exhibit complex geometries that are often highly simplified and cross sections may not be sufficient to highlight the spatial variation of fault surface topography and the complex relationship with the wall rock. The main contributions of this thesis to structural geology are novel methods for investigating links between fault shape and wall rock structure. Curvature plots of sixteen faults show that thrust faults in deepwater Niger Delta exhibit corrugations on a range of wavelength and amplitude. The corrugations are characterized by large-scale anticlastic and synclastic geometries parallel to fault transport direction. The structure of the volumes in the immediate vicinity of the faults was investigated using slices of seismic attribute data sampled parallel and adjacent to thirteen faults. In half of the faults the hanging wall is more disrupted than the footwall, while in the other half the footwall is more disrupted than the hanging wall, implying that thrust zones exhibit complex geometries that existing models have yet to address. In addition, disruptions near fault surfaces may be related to discrete zones of intense fault surface maximum curvature, anomalous surface gradient and change in pattern of anticlastic and synclastic fault Gaussian surface curvature in the fault transport direction. No significant wall rock disruption was observed where fault surface curvature is planar.

A reconnaissance survey of the 1000 Km\(^2\) of Masirah Island, Oman, has revealed a fully-developed ophiolite complex which is believed to represent a fragment of Cretaceous ocean crust and upper mantle generated at a constructive plate margin. The complex consists of mantle serpentinites, plutonic rocks ranging from dunite to trondhjemite, a sheeted dyke complex and pillow lava-sediment sequences, all of which have been chemically and petrographically analysed. Several belts of serpentinite occur within the ophiolite associated with major fault-lines. The serpentinites are clearly derived from depleted harzburgitic mantle and their field relations suggest that some were emplaced in the oceanic environment. The chemistry of the plutonic rocks suggests that they are products of dominantly open-system fractional crystallisation of tholeiitic liquid(s), possibly in several discrete magma chambers. Modelling of trace and RE elements suggests that moderate degrees of mantle peridotite melting were involved in production of the magma chamber parental liquid(s). At a higher crustal level sheeted dyke-massive gabbro relationships are interpreted in a model of roof underplating, which causes a decreasing frequency of dyke injection. Metamorphism of the sheeted dykes and lavas is interpreted as sub-sea floor in origin and its effect on whole-rock chemistry is assessed. The dykes and lavas have a chemistry largely typical of present-day ocean tholeiites and the relative contributions of the processes of partial melting and fractional crystallisation to that chemistry are evaluated. Two localised volcanic groups were identified, which appear to have enriched chemistries compatible with origin at off -axis oceanic islands. A major tectonic zone cross-cuts the ophiolite units and has features reminiscent of the modern oceanic transform faults. The importance of this structure, both in the oceanic environment and during the process of ophiolite emplacement, is assessed. Intrusive into the ophiolite is a granite whose trace and RE element chemistry is alien to the oceanic environment and suggests melting of continental crust Finally, a synthesized model of the former constructive margin is produced and an attempt is made to define the type of spreading centre represented. Comparison of the Masirah Ophiolite with the Semail Ophiolite of the Oman Mountains suggests that their former correlation may be ill founded. An assessment of late Mesozoic -early Tertiary plate motions indicates an origin during Cretaceous sea-floor spreading of an early Indian Ocean. Several features may indicate a slow-spreading, much-faulted, constructive margin.

This thesis presents the results of a multi-proxy analysis of two sediment cores recovered from within the Indian-Atlantic Ocean Gateway (I-AOG). The main focus of this study was on sediment core MD02-2588 which was recovered from the southern Agulhas Plateau. This core was used to produce reconstructions of the paleoceanographic variability of the deep and surface ocean during the past 150 kyr BP. Preliminary paleoceanographic records spanning the past 50 kyr BP are also presented from sediment core CD154-23-16P, recovered off southern Africa. To reconstruct the history of mid-depth ocean circulation on the southern Agulhas Plateau during the past 150 kyr BP, a range of physical and chemical bottom water parameters were derived from the stable isotope, elemental ratio and grain size data from core MD02-2588. These data suggest that, during glacial stages, the southern Agulhas Plateau and the wider mid-depth South Atlantic Ocean came under increased influence of southern-sourced deep waters and experienced an increase in the storage of respired carbon, as CO2 was sequestered from the glacial atmosphere. The associated decrease in the relative volume of northern-sourced deep waters bathing the MD02-2588 core site appears to be counterbalanced by the lower nutrient content of northern-sourced water masses during glacial stages resulting in an overall reduction of nutrient concentrations in the mid-depth South Atlantic. The glacial lowering of seawater nutrient concentration in the mid-depth South Atlantic was possibly also affected by an increase in the formation of lower-nutrient mid-depth waters by open ocean convection in polynyas within the expanded circum-Antarctic sea ice zone. During glacial terminations, mid-depth nutrient concentrations within the I-AOG reach their highest values of the past 150 kyr BP. These increases are interpreted as resulting from the upward mixing of nutrient-rich bottom waters from the deepest and most isolated layers in the Southern Ocean following the deglacial breakdown of stratification in the ocean interior. The increases in mid-depth nutrient concentration recorded during deglaciations occur in tandem with increases in the bottom water carbonate saturation state on the southern Agulhas Plateau and increases of pCO2 in Antarctic ice cores. The covariation of these parameters supports the premise of increased out-gassing of carbon from the deep Southern Ocean during deglaciations. This thesis also examines how the position of the subtropical front (STF) within the I-AOG migrated over the past 150 ky BP and considers how these changes may have impacted the nutrient supply to the surface waters of the southern Agulhas Plateau. The record of bulk sediment nitrogen isotope composition (δ15NBulk) from sediment core MD02-2588 suggests that the northward migration of the STF during glacials is associated with increases in nutrient supply relative to interglacial levels. Enhanced nutrient supply to the surface waters of the southern Agulhas Plateau is thought to be caused by increased northward advection of relatively nutrient-rich Subantarctic surface waters to the MD02-2588 core site, along with weaker upper ocean stratification which facilitated vertical mixing of nutrients from the thermocline. The likeness of the δ15NBulk record from MD02-2588 with analogous records from the eastern equatorial Pacific may suggest that the temporal variability of the isotopic composition of ocean nitrate within these two regions is linked on glacial-interglacial timescales, possibly as a consequence of changes in the position of the Southern Ocean fronts. New data from a set of core-top samples collected around New Zealand were used to assess the utility of the deep-dwelling planktonic foraminifera species Globorotalia truncatulinoides as a recorder of the isotopic composition of dissolved inorganic carbon in seawater. The downcore record of carbon isotopes in this planktonic foraminifera from MD02-2588 displays a correlation with the Antarctic ice core records of the isotopic composition of carbon in the atmosphere during the past 150 kyr BP. The correlation of these records demonstrates the importance of carbon transfer between the Southern Ocean and the atmosphere. Preliminary results of the bulk elemental composition and foraminiferal stable isotope records spanning the past 50 kyr BP are presented from sediment core CD154-23-16P, recovered from the Mallory Seamount off southern Africa. These records are used to reconstruct the terrestrial hydroclimate of southeastern Africa and the hydrography of the Agulhas Current.

Marine Protected Areas (MPAs) are recognised globally as effective tools for protecting valuable and vulnerable marine ecosystems (habitats, species and communities), maintaining the biological diversity, and safeguarding the associated historical and cultural resources. MPAs accommodate local communities and regulate the different uses of the sea, fostering more sustainable use of marine resources. Moreover, MPAs are increasingly being used as environmental laboratories, enabling a greater scientific understanding of marine systems. In the Mediterranean Sea about a hundred of MPAs have been designated during the last decades, all but one of which are in coastal areas. This study develops a new way of using RS techniques tailored for the monitoring and management of Mediterranean MPAs. The advance in satellite Remote Sensing (RS) technologies has made possible to look at the MPAs not only by means of discrete in situ surveys but rather on the basis of a “synoptic” and repeated view. The primary aim of this thesis was to establish how the satellite sensors can be successfully used and whether RS provides reliable tools for monitoring and managing Mediterranean MPAs. The study aimed specifically at describing and identifying, by means of passive remote sensors, the spatial and temporal scale of the bio-physical processes occurring in Mediterranean MPAs. Observations retrieved by ocean colour and thermal infra-red sensors, for a range of MPA study sites, were used to depict system functioning by the analysis of the prevailing spatial and temporal variations of the geophysical parameters and biophysical conditions. The seasonal variations of the ecological indicators (i.e. phytoplankton blooms and thermal trends) were analysed over various MPAs located in different regions of the Mediterranean basin, and different biooptical algorithms were tested in a coastal MPA. The short-term and long-term monitoring (interannual) of the ecological indicators is key to elucidating trends and modifications in the biogeochemical balance of the basin possibly caused by environmental changes which could potentially affect the MPA’s resilience. Consequently it is now possible to monitor MPAs easily and at low cost, by integrating RS with the traditional sampling methodologies to work towards safeguarding of valuable marine habitats and species. RS should be considered as key tool that fosters the ecosystem-based management.