Salt diapirs are some of the most dynamic geological structures in sedimentary basins and vertical rise through their overburdens leads to the development of complex fault systems. Polygonal fault systems constitute a major structural element of fine-grained sediments in sedimentary basins, forming without the requirement of tectonic extension during the early burial phase of sediment compaction and dewatering. These same fine-grained sedimentary overburdens are also deformed by salt diapirs and their associated fault systems in basins such as the Gulf of Mexico, the South Atlantic margins and the North Sea. The aim of this research was to investigate the interactions between salt diapirism and faulting in overburdens deformed by polygonal fault systems using 3D seismic data sets from the Central North Sea and the extensional domain of the Espírito Santo Basin on the SE continental margin of Brazil. In both case studies the regional isotropic planform arrangements of polygonal faults mapped in the post-salt overburden have preferred (radial) orientations around salt stocks, orthogonal alignments with tectonic faults and salt walls, and concentric arrangements in withdrawal basins. Radial faults around salt stocks are invariably layer-bound, conforming to the same discrete layer of stratigraphy as laterally equivalent to layer-bound polygonal fault systems. In the Espírito Santo Basin, the lateral distribution and stacking of polygonal faults is heavily influenced by the distribution of proximal and distal seismic facies. In the Central North Sea spacing, throw and fault length vary as a function of tier thickness. Polygonal and radial faults in the same tier have a similar range of maximum throws and spacing but differ in length and aspect ratios. Radial faults are classified as perturbed members of the basin-wide polygonal fault system which propagate primarily under the influence of compaction and contraction but in an anisotropic stress field. Stacked arrays of layer-bound radial and polygonal faults formed sequentially where upper tier boundaries date the cessation of fault activity. The radial fault zone is between 2-4 stock radii wide. The radial fault zone expanded as salt growth intensified or widened, and contracted as they slowed or became narrower. However, the width of the radial fault zone is not related to the hinge in the domed overburden discrediting arching as mechanism forming the radial faults. Instead, the transition boundary separating zones of radial and polygonal faults in a tier is interpreted to reflect the lateral-extent of hoop stress around salt stocks during faulting. An upward change in the regional polygonal planform and dip polarity of polygonal faults in the Espírito Santo Basin is attributed to a change in the regional stress field during the cessation of thin-skinned extension and gravity gliding and the onset of inversion. The results of this thesis highlight the sensitivity of polygonal fault system to local stress anisotropy and provide a potential route for reconstructing the palaeostate of stress around salt diapirs.

Marine sedimentation from the Adélie Land continental margin of East Antarctica provides unique high resolution records of Holocene environmental change. The subannually resolved sediment cores MD03-2601 (66°03.07’S, 138°33.43’E) and IODP-318-U1357B (66°24.7990′S, 140°25.5705′E) from the Dumont d’Urville Trough,Adélie Land, document atmospheric and oceanic processes impacting on biogenic sedimentation on the Adélie Land continental shelf during the Holocene. Resin embedded, continuous polished thin sections from each core were analysed for diatom content and sediment microfabric using scanning electron microscope backscattered electron imagery. The sediments contained repeating sequences of seasonal diatom-rich laminae which enabled multi-taper method time series analysis. Time series analysis shows that in the Hypsithermal there appears to have been an external (solar) control on interannual sedimentation as well as internal controls (e.g. the southern annular mode, SAM, and El Nino-southern Oscillation, ENSO); whilst in the Neoglacial internal climatic modes exerted a much stronger control. Quasi-biennial (2 – 3 year) peaks commonly occurred in analysis of both Hypsitherml and Neoglacial sequences. The distribution of resting spore-rich laminae in these sections suggests that a multidecadal (>50-years) variation between phasing of the SAM and ENSO systems may exert an important control on interannual environmental variability in the sections analysed. The distribution of diatom-derived biomarker proxies, namely C25 highly branched isoprenoid (HBI) alkenes, was compared to the diatom lamina-based record in core MD03-2601. At the Holocene scale, HBI diene and triene molecules have a positive association to sea ice associated diatom-rich laminae, with greater abundances of both HBI molecules and sea ice associated diatom laminae in the Neoglacial interval. However, at a sub-annual resolution there is no strong association between lamina type and HBI concentrations. This is attributed to a combination of: (i) the HBI alkenes recording a different signal to that of the diatom-rich laminae; (ii) interannual variation in HBI export that is greater than inter-seasonal variation, for which there is little modern data for comparison; (iii) possible diagenetic alteration of the HBI signal.

From 2010 The Flood and Water Management Act has given the Environment Agency and local authorities in the United Kingdom a statutory requirement to manage flooding from groundwater. A robust, long-term groundwater flood risk assessment methodology was developed using the Pang/Lambourn catchment in West Berkshire as a case study. A recharge model based on a soil moisture budget was built in GIS and tested against observations. The timing and mechanism of flow in the vadose zone was also assessed using cross-correlation analysis between rainfall and borehole responses for a better understanding of recharge processes. Regional MODFLOW models were developed for saturated groundwater flow using input from the recharge model. This integrated model was then coupled with a Global Climate Model using a stochastic weather generator to downscale output to the catchment. An ensemble of high and low climate change scenarios suggests there will be between a 5.5% and 27% reduction in recharge over the coming century and mean groundwater levels will lower by up to 3.8%. Land use modification characterised by afforestation and urbanisation resulted in nuanced changes in the spatial distribution of recharge as well as a further mean reduction of 6.8% on top of the climate change impacts. Groundwater flood hazard maps were developed and integrated with a social vulnerability index to identify 1.7 km2 of the Pang/Lambourn at high risk. In the Pang catchment this represents around 1400 properties. Climate and land use change scenarios suggest however that the risk of groundwater flooding in the catchment will decrease considerably (25-98%) over the next century. This reduction in risk is likely to make mitigation through targeted land use modification unnecessary.

Abstract A comprehensive phylogeny of macroperforate planktonic foraminifer species of the Cenozoic Era (~65 million years ago to present) is presented. The phylogeny is developed from a large body of palaeontological work that details the evolutionary relationships and stratigraphic (time) distributions of species-level taxa identified from morphology (‘morphospecies’). Morphospecies are assigned to morphogroups and ecogroups depending on test morphology and inferred habitat, respectively. Because gradual evolution is well documented in this clade, instances of morphospecies intergrading over time have been identified, allowing the elimination ‘pseudospeciation’ and ‘pseudoextinction’ from the record and thereby permit the construction of a more natural phylogeny based on inferred biological lineages. Each cladogenetic event is determined as either budding or bifurcating depending on the pattern of morphological change at the time of branching. This lineage phylogeny provides palaeontologically calibrated ages for each divergence that are entirely independent of molecular data. The tree provides a model system for macroevolutionary studies in the fossil record addressing questions of speciation, extinction, and rates and patterns of evolution. Specifically for this thesis the phylogenies provide a statistically robust framework for testing Cope’s rule (the evolutionary trend towards larger body size along a lineage). Eleven case studies were selected at random from all possible Neogene lineages and the mean areas of ancestor and descendant populations were compared. Over 6000 measurements were taken from 30 lineages and the resulting data show that Neogene macroperforate planktonic foraminifera do not support Cope’s rule with only 48% of the ancestor-descendant population comparisons demonstrating an increase in mean area. The size analysis illustrates that the most robust method for testing Cope’s rule is to compare ancestor-descendant populations from the beginning and end of evolutionary lineages as these are the least affected by temporal sampling biases.

The ‘Silicic Acid Leakage Hypothesis’ (SALH) is a mechanism by which the increased supply of silicic acid to the low latitude ocean allows diatoms (silica producers) to outcompete coccolithophorids (carbonate producers). This would result in a decrease in the export of carbonate, and drawdown of atmospheric CO2 through changes in surface- and whole-ocean alkalinity. Here I test the SALH as a potential cause of CO2 drawdown during glacial Marine Isotope Stage (MIS) 4 (~70-59 ka). Firstly, I measure opal (biogenic silica) accumulation rates in a suite of cores from the equatorial Atlantic, to determine whether the export productivity of diatoms increased during MIS 4. I found that opal accumulation rates increased ~100% in MIS 4 relative to interglacial MIS 5a (~84-77 ka), in agreement with the SALH; however the timing of the changes make the SALH unlikely to be the direct cause of the CO2 drawdown. I then measured the calcium carbonate accumulation rates in the same suite of cores and found that carbonate accumulation decreased in MIS 4 relative to MIS 5a, also in agreement with the SALH. However, I found that this decrease may have been the result of enhanced carbonate dissolution. I also tested the SALH directly by reconstructing changes in the silicic acid concentration of AAIW, by using neodymium and silicon isotopic ratio measurements. I found that AAIW conveyed an increased amount of silicic acid into the western tropical Atlantic during MIS 4, and that the timing of this increase was coeval with increases in both low latitude opal accumulation, and also opal accumulation in the northwest Atlantic. Lastly, I tested the amount of atmospheric CO2 drawdown which could have been attributed to the SALH mechanism during MIS 4 by using a box model, and I estimated that ~35-50 ppmv of CO2 drawdown is achievable.

The Voskhod podiform chromitite is one of more than 30 chromitite deposits that collectively form the Main Ore Field (MOF) within the Kempirsai Massif, in Kazakhstan. The MOF is the largest podiform chromitite ore-field in the world. The Voskhod deposit, encased in a serpentinised dunite halo, is situated within harzburgite units that comprise the mantle sequence of the Kempirsai ophiolite. This study arose from a unique opportunity to work on drill core samples through an un-mined podiform chromite deposit and investigate its internal structure, composition and genesis. The 18Mt ore-body has a strike of 600 m, is 170 m to 360 m wide and has an average thickness of 39 m. It has an immediate dunite halo between 1 m and 5 m thick. The ore body is made up of multiple stacked chromitite layers. Mineralised layers are separated by barren dunite or by weakly disseminated dunite lenses ranging from <1 m to 50 m. The style of mineralization varies throughout the ore body; the central region is dominated by thick (>5 – 45 m) units of massive chromite (>80% chromite), with progression towards the south west disseminated chromite (10 – 40% chromite) becomes increasingly abundant. Drill core logging and cross-section profiling of the internal structure of the ore body has identified an intricately connected network of what appear to be chromite-filled channel-ways. Outside of the halo the host rocks are inter-layered harzburgite and dunite. Accessory chromite in harzburgite has an average Cr# of 0.31 compared to Cr# 0.49 in the dunite. The harzburgites are depleted, having formed from intermediate degrees of partial melting (~15 – 18 %) of a fertile mantle source at a mid-ocean ridge (MOR) setting. The dunite units have transitional geochemical fingerprints that imply they formed from the interaction of MOR mantle harzburgite with both mid ocean ridge baslt-melt and an arc derived-melt. They are not the products of extremely high degrees of partial melting. The encasing dunite halo is extensively serpentinised (>80%). Chromite is only present as an accessory phase having an average Cr# of 0.62. The dunite has a geochemical signature indicating that it formed by reaction between residual harzburgite and a boninite melt in supra-subduction zone (SSZ) tectonic setting. A variety of geochemical fingerprints have been identified; residual MOR harzburgite, reacted-MOR dunite, reacted-SSZ dunite and harzburgite, indicating that the mantle section has had a ii polygenetic tectonic evolution, recording both ocean basin opening (MOR setting) and closing (SSZ setting) events. Trace element and REE whole rock geochemistry of the chromitites and associated host rocks provide evidence of depletion and a later-stage LREE-enrichment event. LREE-enrichment is most intense within and immediately adjacent to the chromitite. Chromites from the ore zone are at the Cr-rich extreme for podiform chromites (Cr# ave. 0.80-0.85) and are TiO2 poor (ave. 0.16 wt%), similar to chromite in boninite worldwide and nearby. Al/Ti ratios have been used to calculate the composition of the parent melts from which the Voskhod podiform chromitite crystallised: compositions that are synonymous with a boninite melt composition. Chemical variation in chromite is systematic and on a much smaller scale than was anticipated. Even variations in a single thin section provide key evidence for different magmatic processes. An apparent melt-rock reaction in harzburgite has been examined in freeze-frame. The chromite chemistry has been investigated at 50 cm, 1 cm and 1 mm scales. Compositional differences were identified on the basis of MgO% and FeO(t)% compositions. Diagrams FeO-Fe2O3 and Cr# - Mg# were used to demonstrate the variations and identify relationships. Broad cryptic layering on a 50 cm scale has been found as well as fine-cryptic layering on a 1 – 8 cm scale. The variations are interpreted to reflect differences in the mineral phases crystallised from the melt; periods when on chromite only crystallised are distinguished from periods when both chromite with olivine crystallised. It seems likely that the deposit is made up of thousands of episodes of chromite accumulation that formed in an intermittently replenished open-system. It also seems likely that the conduit was never a single melt-filled cavity; instead melt flow was focused through the mantle over an extended period. The conduit appears to be comprised of multiple branches, as chromite (± olivine) crystallised from the melt the channel-way became blocked and the melt was forced to deviate and make a new pathway through the mantle. As time elapsed the process resulted in the formation of stacked chromitite lenses, creating an orebody that has an internal arrangement of chromitite and dunite unites which resemble a stacked braided 'delta'.

Many processes involved in the accretion of lower oceanic crust remain enigmatic. To investigate some of these processes, the principal focus of this study is drill core 'CY-4', an unbroken 2.2km long section through sheeted dykes and mafic and ultramafic cumulates of the Troodos ophiolite lower crust, Cyprus. The generally accepted hypothesis states CY-4 intersected an axial magma chamber that was intruded by an off-axis pluton, based on a 'stepped' increase in clinopyroxene titanium content at 1331 m depth. This comprehensive structural, textual and trace element examination throughout CY-4 indicates a single, open system, plutonic sequence. It is comprised of high-level, varitextured gabbros, underlain by foliated gabbronorites and low-level, banded, gabbronorites and ultra mafic cumulates. Steeply inclined planar and linear fabrics were generated by upward migration of magma. Flow was predominantly channelised through the upper cumulates and diffuse through the lower cumulates, with corresponding differences in preserved structures and textures. Channelised flow and magma remobilisation in the rapidly cooled and poorly equilibrated upper cumulates is responsible for the decametre-scale textural and chemical variations. Syn-tectonic porous flow through the slower-cooled banded cumulates led to grain-scale textural and chemical interactions. Any initial mineral co-variations were erased during supra-solidus equilibration and efficient expulsion of incompatible element-rich melts. Any early-formed layering was transposed. A new model of CY-4 accretion is proposed in which a broad range of depleted and boninitic magma compositions were efficiently homogenised in the lower crust to yield the narrower ranges of extruded compositions. Correlations with Troodos Lower an Upper Pillow Lava series may indicate sources within the foliated gabbronorites, and the deeper ultramafic region respectively. The structural resemblance of the CY-4 cumulate series to fast-spreading lower crust can be reconciled with the slow spreading rate calculated for Troodos if CY-4 intersected a ridge axial node of magma upwelling

This thesis compiles the results of a 3D seismic-based study of the geometry and emplacement mechanics of igneous sills and sill complexes intruded into basins along the NE Atlantic Margin. Dolerite sills were intruded into the Upper Cretaceous and Paleocene mud-dominated sediments of these basins during the Paleocene and Early Eocene, approximately synchronous with the onset of seafloor spreading between NW Europe and Greenland. Detailed interpretation of igneous intrusions in four case-study areas has revealed that sills adopt a wide range of geometries, ranging from near-concordant sheet-like forms to complex discordant forms. Detailed mapping illustrates that the traditional definition of a sill as 'a tabular igneous intrusion with concordant surfaces of contact' is inadequate when describing the fully three-dimensional geometry of sills. This has encouraged the development of a new classification scheme for igneous sills that considers their detailed three-dimensional geometry. Many sills have been found to adopt a saucer-shaped geometry and these are interpreted to form through a three-step model involving lateral propagation, inflation and overburden deformation, and intrusion along deformation-related peripheral fractures. 3D seismic mapping has allowed for igneous sill complexes to be imaged in three dimensions for the first time. These complexes are found to form highly interconnected networks that cover many kilometres of vertical section (&sim;8 km). Based on the interpretation a new model for the construction of sill complexes is proposed. In this model a sill complex builds up from deeper to shallower levels with sills intruded at one stratigraphic level acting as feeders for sills intruded at shallower levels. Interpretation of hydrothermal mounds and jack-up structures formed during sill intrusion has allowed for the timing of sill emplacement to be constrained in the four case-study areas. This has revealed that several discrete phases of intrusion took place during the Paleocene and earliest Eocene

The aim of this research is to develop an integrated and cost-effective site investigation approach for slow moving landslides or potentially unstable slopes found within the South Wales Coalfield, an area of complex geology and hydrogeology. The research was based on the use and assessment of a wide range of surface geophysical techniques, supported by GPS and Digital Photogrammetry surveying, and the joint interpretation of the results which such techniques provide. The South Wales Coalfield has one of the highest concentrations of urban landslides in the UK due to its layered Carboniferous geology. Quaternary / Holocene geomorphology, coal mining history and relatively high rainfall. Mynydd yr Eglwys landslide (Ystrad, Rhondda Cynon Taff) was selected as the field study site because it can be considered representative of the active landslides found within the area. In autumn 1998, following an exceptional heavy rainfall period, a new compound deep- seated failure developed in a previously mined hillslope. This deep-seated failure then caused the reactivation of ancient periglacial debris slides downslope creating a serious risk to the modern housing estate located close to the toe. Electromagnetic (GEM-2), self potential, electrical resistivity tomography, seismic refraction tomography, MASW and induced polarization geophysical data were all acquired on the landslide. This combination of techniques provided information on lithology, faulting, degree of rock fracturing/weathering, thickness of displaced material, spatial distribution of areas with high water/clay content and the direction of groundwater flow. The repetition of a few ERT and SP profiles showed the applicability of geophysical monitoring in detecting changes in groundwater content and defining preferential groundwater pathways within the hillslope. Digital Photogrammetry from Helium balloon can provide a 3D landslide topographic model with 10cm-level accuracy. Topcon HiPer Pro GPS+ instrument can be used in RTK mode to monitor movement with 12mm and 15mm horizontal and vertical precision respectively.

The geological and geodynamic processes that have controlled the evolution of the Northumberland Trough Region in Northern England have been investigated to expand understanding of the evolution of continental extensional basins. The region has experienced a number of extensional, compressional and wrench tectonic events throughout Late Palaeozoic, Mesozoic and Cenozoic times. These events have led to a complex subsidence and uplift history. A kinematic model has been developed in two-dimensions to simulate the structural deformation caused by extension by faulting and pure shear, thermal processes and the flexural isostatic due to tectonic loading. The stratigraphy varies across the region between the block and basins, which has been addressed within the modelling by the development of algorithms to simulate palaeobathymetry, compaction and erosion. Extension within the crust was taken up on multiple faults generating an average total heave of approximately 10-15km. Model results indicate there was non-uniform extension of the lithosphere with greater extension below the fault detachment depth where ductile deformation is the principal deformation mechanism. Results generated using a modelling approach that utilises multiple tectonic events generate stratigraphic patterns of syn-rift and post-rift deposition that support extension at multiple time stages within the Northumberland Trough Region during the early-Carboniferous period. Models that reconcile the observed amount of fault-controlled deformation with the magnitude of overall thinning of the crust generate comparable amounts of subsidence to that observed in the basin structures. In contrast, these models over-estimated the amount of subsidence on the block structures. It has been hypothesised that this mismatch was due to the North Pennines Batholith, which acts as a negative load upon the lithosphere. Development of an algorithm to model the isostatic response of the lithosphere to the North Pennines Batholith has provided insights into the influence of igneous intrusions on the post-emplacement structural development of the area. Model results incorporating the batholith indicate the generation of a significant amount of uplift coincident with the presence of the batholith, and show a realistic geometry and upliftsubsidence pattern across the Alston Block and adjacent basins.