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.

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 structures of the lead-free perovskites in the solid solution range (KxNa1-x)0.5Bi0.5TiO3 (KNBT100x) have been investigated using high-resolution x-ray diffraction (XRD) on polycrystalline samples. The room-temperature structure of Na0.5Bi0.5TiO3 (NBT) has been studied, and identified as having monoclinic Cc symmetry, with distortion very close to that of rhombohedral R3c. High-temperature XRD has been used to identify a phase transition between the pseudo-rhombohedral phase and a tetragonal P4bm phase at 300 °C. This transition has been found to occur via a pseudocubic structure, although local variations in transition temperatures lead to the coexistence of both phases, with a hysteresis of ~ 30 °C. The Curie temperature, TC, has been found to lie in the range 450 °C – 530 °C. The room-temperature structures of compositions from NBT to (K0.65Na0.35)0.5Bi0.5TiO3 have been studied, and a phase boundary identified at x ~ 0.2. Compositions from NBT – KNBT20 refine as monoclinic Cc, with pseudo-rhombohedral symmetry, whilst KNBT25-65 were found to have equilibrium phase P4mm, with a stressinduced R3m phase also present. A relationship was observed between the spontaneous tetragonal strain and the proportion of tetragonal phase present in these samples. KNBT10 and KNBT40 did not show evidence of the high-temperature P4bm phase; instead, TC values were found to be ~ 225 °C and ~ 300 °C respectively. Experimental data have been combined with data from published literature to construct a phase diagram of the KNBT system. KNBT synthesised via a hydrothermal method has been investigated. Hydrothermal NBT, once heat-treated, has been found to show similar structure to solid state NBT and undergoes the pseudo-rhombohedral to tetragonal transition at 305 °C, with a hysteresis of ~ 20 °C between heating and cooling. TC was found to be higher, in the range 530 °C – 700 °C. The XRD patterns of non-heat-treated hydrothermal KNBT have broader peaks and a more undulating background, indicative of smaller crystallite size and diffuse scattering from a more disordered material. The proposed source of this disorder is the presence of oxygen vacancies, OH- groups, or A-site clustering. Significant peak splitting was observed in the XRD patterns of hydrothermal K0.5Bi0.5TiO3 (KBT) and tetragonal KNBT. This was not the case for solid state KNBT, showing a greater tetragonal distortion in materials prepared via the hydrothermal method. Heat-treating this material was found to effect a significant structural change, with single peaks remaining after cooling. It is proposed that this could be caused by the release of OH- groups, recrystallisation, and mixing of the A-site species.

In today's North Atlantic, warm and salty surface waters are transported northwards from the subtropics, releasing their heat and eventually sinking to form a deep southward-flowing water mass. This process in the meridional-vertical plane is termed the Atlantic Meridional Overturning Circulation (AMOC). Changes in the strength and structure of the AMOC play a critical role in the Earth’s climate system and have been thought to be implicated in the climate variability of the Late Holocene. In this thesis, two sediment cores RAPiD-35-25B and RAPiD-17-5P recovered from the Eirik Drift (South of Greenland) and the Iceland Basin are used to produce Late Holocene palaeoceanographic reconstructions of some of the main constituents of the AMOC at sub-decadal to multidecadal resolution. Upper water column reconstructions from the Eastern Labrador Sea based on multi-species planktonic foraminiferal δ18O, Mg/Ca and faunal assemblages indicate millennial to centennial variability in the influence of polar waters reaching the Labrador Sea which likely led to reductions in deep water convection in the Labrador Sea. Inferred shifts of Labrador Sea Water formation appear concomitant with climatic anomalies recorded in the North Atlantic region. It is suggested that these climatic oscillations may have resulted from a coupled ocean-atmosphere response to reductions in solar irradiance. The paired δ18O and Mg/Ca composition of the thermocline-dweller G. inflata, shows multi-centennial shifts in the temperature and salinity of the North Atlantic Current during the last millennium with a potential link to solar forcing. The recorded hydrographic variability is explained in terms of the effects of atmospheric blocking events on subpolar gyre dynamics. Sortable silt mean grain size measurements show millennial-scale trends towards slower and faster vigour of the overflows east and west of Iceland during the Late Holocene. Potential upstream and downstream mechanisms are investigated and it is concluded that the millennial-scale variability in the strength of the overflow likely resulted from insolation driven Neoglacial changes in the freshwater budget and atmospheric circulation in the Nordic Seas. Furthermore, an antiphasing relationship between the strength of the two overflows is found, supporting previous predictions from modelling studies.

Hydrothermal systems may have been more widespread in the Hadean due to a greater heat flux. To investigate this possibility, and unravel the mechanism(s) by which the pH of high-temperature vent fluids become acidic and what produces their distinctive black colour, reactions between model seawater and mafic/ultramafic rock were conducted. Results indicated that ancient, medium to high temperature (150-300°C), alkaline hydrothermal fluids would have precipitated carbonates, brucite, and calcite upon re-mixing with cold, slightly alkaline seawater and may have predominated in the Hadean. Acid pH was effected by the loss of magnesium from seawater and calcium loss from mafic rock. Black-smokers were unlikely in the Hadean as the ocean was probably acidic due to high levels of CO2. Water-rock reaction models were constructed to test the possibility that simple amino acids could have been generated in early hydrothermal fluids, and to see how pH and redox conditions affect their distribution (cf. Amend and Shock, 1998). Though concentrations of amino acids produced were negligible, amino acids were stable in low-temperature, alkaline, and reduced hydrothermal fluids and may have concentrated in the colloidal sieve comprising a hydrothermal mound. An extension of the experiment to determine if glycine could be condensed to higher carbon number amino acids (alanine, valine, leucine) under hydrothermal conditions, indicated that condensation may be 'pulled' by a decrease of H2O activity of the fluid. In conclusion, this study improved on previous environmental and reactant constraints by simulating the generation of inorganic prebiotic reactants from the local geochemical hydrothermal environment. Consequently, the quantity of chemical species such as hydrogen and sulfide available for organic synthesis were limited by the local geochemical settings in the model, whereas others have, often admittedly, used reactants in higher concentrations than were probably available when Life emerged.

The ratios of trace metals to calcium in the calcium carbonate tests of benthic foraminifera have been used as palaeoceanographic proxies for several decades and are now routinely used to reconstruct past climate change on a variety of Cenozoic timescales. Recent research, however, reveals gaps in our understanding of the effects of oceanic variables such as temperature and carbonate saturation state on these trace metal ratios, which limits their application as proxies. Additional uncertainties arise because of physiological effects (“vital effects”) and microhabitat of the living foraminifera. Moreover, much of what is known about trace metal uptake into benthic foraminiferal calcite is derived from modern core-top calibrations and laboratory experiments and it is unknown as to what extent our understanding from these models can be applied to the early and mid Cenozoic. This thesis attempts to address some of these questions using a novel depth transect approach and presenting benthic foraminiferal trace metal records across three major Cenozoic climate change events from Ocean Drilling Program (ODP) deep sea core material. The events are: (i) The Eocene-Oligocene transition (EOT), (ii) The Oligocene- Miocene boundary event (Mi-1) and (iii) The Middle Miocene Climatic Transition (MMCT). These records have allowed examination of the validity of the application of current knowledge of benthic foraminiferal trace metal proxies to Cenozoic records, and also the comparison of the records of two different benthic foraminiferal species, which has shed new light on the importance of foraminiferal habitat in the interpretation of the proxy data. The identification of a dissolution effect operating on benthic foraminiferal Mg/Ca in undersaturated waters has allowed a reasonable estimate of cooling (~2-3˚C) to be obtained from deep-sea records across the Eocene-Oligocene Transition. The transient glaciation at the Oligocene-Miocene boundary is estimated to comprise of a deep-sea cooling of ~2°C and a sea level decrease of ~80 metres based on Oridorsalis umbonatus Mg/Ca. Comparison of new Middle Miocene trace metal records across a water depth transect has shed light on the relative interplay of temperature and saturation state on published Mg/Ca records, enabling more accurate estimates of temperature and ice volume change. The new interpretations suggest that deep sea temperatures cooled by ~4.5C, and sea level fell by 70-100 metres between 16.2 and 11.6 Ma. The recently developed paired Mg/Ca-Li/Ca approach to calculating simultaneous variations in bottom water temperature and saturation state has been used to assess inter-basinal differences in water mass composition for the first time. Down-core benthic foraminiferal Li/Ca records from Ceara Rise Sites do not behave as expected, indicating that there may be times when this proxy is affected by an additional environmental parameter. This is tentatively suggested to be a growth-rate related oxygenation signal. U/Ca in benthic foraminifera does not appear to work as a saturation state proxy in these records, again indicating either different behaviour to the observed modern behaviour, or additional factors absent from the modern calibration, such as bottom water oxygenation. Benthic foraminiferal Sr/Ca follows the linear negative water-depth relationship of Lear et al., (2003) suggesting a pressure-related effect. This study demonstrates that benthic foraminiferal trace metal chemistry can be used to provide information about climate events in the Cenozoic, however additional empirical work is required to fully understand the systematics of trace metal incorporation into benthic foraminiferal tests.

The Mg/Ca temperature proxy was applied for the first time to seasonality records in calcitic brachiopod shells, using a laser ablation tracking technique on both Recent and fossil material. Seawater temperature calibrations were established using modern Terebratulina retusa from Scottish waters with annual temperature variations ~7 °C, and Liothyrella neozelanica from a water depth transect (168–1488 m) off New Zealand. Comparison of intra-shell Mg/Ca with shell δ18O confirms a temperature control on brachiopod Mg/Ca. Preliminary temperature calibrations are: T. retusa Mg/Ca=1.76±0.27e(0.16 ± 0.03)T, R2=0.75 L. neozelanica Mg/Ca=0.49 ± 1.27e(0.2 ± 0.11)T, R2=0.32. The Eocene-Oligocene Transition (EOT) is the first time during the Cenozoic that Antarctica was permanently glaciated. Mg/Ca and δ18O of brachiopod calcite from two New Zealand sites, one Late Eocene and one Early Oligocene, were sampled to assess seasonality over the EOT. Mg/Ca data identify no statistically significant change in seasonality in this area over the EOT. A 1.3 ‰ positive excursion in δ18O is identified: 0.6 ‰ is attributed to global change in δ18Oseawater and 0.7 ‰ to regional change in δ18Oseawater. Surface currents remained the same around New Zealand across the EOT. Summer Mg/Ca seawater temperatures (~21-24°C) in New Zealand are similar to temperatures derived from TEX86 (Site 1172). The Silurian Ireviken Excursion (~428 Ma) is a worldwide δ13C and δ18O isotopic excursion. Atrypa from Gotland, Sweden was sampled from before and after this Llandovery/Wenlock excursion. Mg/Ca and δ18O data indicate no significant change in seawater temperature over this excursion, against a shift of 1.29 ‰ in δ13C. Relative temperature changes between summer and winter Mg/Ca suggest seasonality of 3.5–5.4 °C. Estimated seawater temperature ~37 °C agrees with a recent clumped isotope study. High temperatures obtained in another study may be attributable to sampling that incorporated the outer side half of the secondary layer.

In deeply buried petroleum reservoirs, authigenic iron-rich chlorite coats on sand grains act as barriers between silica-rich waters and the host grain and inhibit the generation of authigenic quartz cements leading to anomalously high porosity and permeability in sandstones. The origin and distribution of iron-rich chlorite grain coats in the deep subsurface is poorly constrained. To address this, the formation processes and geographic distribution of potential precursor minerals to authigenic iron-rich chlorite grain coats, such as berthierine, have been investigated in two modern estuarine analogues. Estuarine environments are important locations of soluble iron-loss and mineral flocculation, and links between water geochemistry variation, climate, local geology and clay mineral distributions are here addressed. The two estuaries investigated, in NW Spain and SW Iceland, have contrasting climates and hinterland geology, which are major controls in clay mineral types present in the local soils and within the estuary. The formation and distribution of all minerals present in the estuarine environment have been considered. In NW Spain, kaolinite, illite-muscovite and chlorite are the dominant clay minerals in the fine fraction of both the soils and estuary sediments and are present in the estuary surface sediments in similar bulk ratios to the local soils. In SW Iceland, smectite, vermiculite and chlorite are the dominant clay minerals in the fine fraction of the local soils and estuary sediments. They are also present in similar bulk ratios in both the soils and in-estuary sediments. Precipitation of neoformed carbonate mineral occurs in the lower estuary reaches of the Spanish estuary but is not evident in the Icelandic estuary. Evaporation and the corresponding supersaturation of mixed waters are responsible for carbonate mineral formation, highlighting the significance of climate on mineral type within estuarine systems. Dissolved iron is lost within the estuarine turbidity maximum zone, in the presence of relatively small proportions of seawater in the upper reaches of the two estuaries. In NW Spain, 37% is removed from the water by the upper reaches and 98% is removed by the middle reaches. In SW Iceland, 91% is removed from the water in the upper reaches while all is removed by the middle reaches. The estuarine turbidity maximum zone is responsible for the re-suspension of solid iron phases, resulting in elevated particulate iron in the upper estuary reaches. In NW Spain, particulate iron increases from the riverine input by 54% in the upper reaches while in SW Iceland, particulate iron increases from the river and stream inputs by 242% in the upper reaches of the estuary. Within the surface sediments of both estuaries, there is minor variation in clay mineral distribution of the fine fraction of the surface sediments from the upper reaches to the lower estuary. Provenance is a dominant control on the clay mineral type present in modern environments. Climatic regime and estuarine circulation processes are also factors with regards to clay distribution within the estuarine environment. This study has led to an enhanced understanding of early diagenesis, such as the location of iron loss and deposition in estuaries, the role of provenance, climate and freshwater input in clay mineral type formation and how evaporation may introduce early diagenetic cements into modern estuaries and will lead to future research development and predictive models relative to iron-rich chlorite grain coat distribution.

Ceria nanoparticles (NPs), due to their widespread applications, have attracted a lot of concern about their toxic effects on both human health and environment. Cerium occurs in two oxidation states, Ce (III) and Ce (IV), and has the unique ability to readily switch between these two states. There is a lot of speculation on the redox behaviour of cerium oxide being related to its toxicity but there are large gaps in knowledge of whether Ce (III) or Ce (IV) is responsible for such toxic behaviours, their toxicological mechanism and safety assessment. The aim of this study is to accurately quantify the ratio of Ce (III) and Ce (IV) in synthesised ceria samples using a multi-method approach thus providing an insight in understanding their surface chemistry and hence biological behaviour. Ceria NPs of different shapes and sizes were produced with different strengths of interaction between core and capping agent/no capping agent and with both steric and charge stabilization. The oxidation state of the samples was determined using STEM-EELS and XPS. Later in the study, we investigated the uptake and internalisation of different shapes and sizes of ceria NPs in lung-derived A549 cell lines (Adenocarcinomic human alveolar basal epithelial cells, A549).