The British Tertiary Igneous Province (BTIP) contains several large ‘breccia’ outcrops, classically interpreted as ‘vent agglomerates’ (Harker 1904; Bailey et al. 1924; Richey & Thomas 1930). Re-examination of localities on Ardnamurchan, Mull and Skye provides new evidence that many of these represent mass flow deposits, with implications for the environment and topography of the BTIP at the time of deposition. At Carraig Mhor, east of Carsaig Bay on the south coast of Brolass, Isle of Mull a sequence consisting of ignimbrite, grading vertically into siltstones and sandstones, is overlain by thick, coarse breccias The breccias comprise pale igneous clasts (2cm - 1m) with crenulate, angular and rounded shapes, set within a dark, fine-grained, laminated, sedimentary matrix. Complex inter-relationships between clasts and matrix are interpreted as reflecting magma-sediment-water interactions. The breccias are interpreted as peperites and the sequence below provides evidence of local silicic pyroclastic activity during the early stages of formation of the Mull Lava Field. ‘Breccias’ on the Ardnamurchan Peninsula have previously been interpreted as ‘vent agglomerates’. Within them, distinct ‘Ben Hiant’ and ‘Northern’ vents have been identified (Richey & Thomas 1930). However, there is no evidence for primary pyroclastic or explosive activity forming these deposits, although clasts of ignimbrite indicate earlier silicic pyroclastic activity. The ‘breccias’ are typically conglomerates with clasts ranging from rounded to (less commonly) sub-angular, and from 2 cm up to 3m in size. Shattered ‘megablock’ deposits (up to 30m in length) are present locally. Together, these deposits form a stratified sequence containing numerous sedimentary structures. Analysis of clast/matrix relationships and of distribution patterns provides evidence for debris flow/avalanche deposition with increasing clast size, heterogeneity and roundness away from ‘source’.

Understanding how faults initiate and fault architecture evolves is central to predicting bulk fault zone properties such as fault zone permeability and mechanical strength. The study of faults at the Earth’s surface and at near-surface levels is significant for the development of high level nuclear waste repositories, and CO2 sequestration facilities. Additionally, with growing concern over water resources, understanding the impact faults have on contaminant transport between the unsaturated and saturated zone has become increasingly important. The proposal of a high-level nuclear waste repository in the tuffs of Yucca Mountain, Nevada has stimulated interest into research on the characterisation of brittle deformation in non-welded to densely welded tuffs and the nature of fluid flow in these faults and fractures. The majority of research on the initiation and development of faults has focussed on shear faults in overall compressional stress regimes. Dilational structures have been examined in compressional settings e.g. overlapping faults generating extensional oversteps, or in normal faults cutting mechanical layered stratigraphy. Previous work has shown the affect mechanical stratigraphy has on fault dip angle; competent layers have steeply dipping segments and less competent layers have shallowly dipping segments. Displacement is accommodated by shear failure of the shallow segments and hybrid failure of the steeply dipping segments. As the fault walls of the shear failure segment slip past each other the walls of the hybrid failure segment are displaced horizontally as well as vertically thus forming dilation structures such as pull-aparts or extensional bends. Work on truly extensional faults has been at the kilometre scale of fissure swarms in rift systems where the focus is on fault geometry and direction of fault propagation. This study examines dilational faults with offsets of centimetres to 10’s of meters within moderately and densely welded ignimbrite units on the caldera island of Gran Canaria, Spain. Through the investigation of fault populations within different ignimbrite units I have examined how the fault architecture changes with accumulated displacement, identified the factors controlling fault core evolution and using these observations developed a new model for the initiation and growth of dilational faults in ignimbrites. The faults in this study do not have a linear correlation of increasing fault core thickness with displacement. Fault core width varies along fault dip and the largest offset faults have the narrowest fault cores. Furthermore, the damage zone joint frequency shows a limited increase with increasing displacement and faults and joints are sub-parallel. From these observations I have developed a new model for fault initiation and evolution in which the petrophysical properties of the host rock are the primary control on fault architecture. Faults initiate on existing sub-parallel joints and grow by the incorporation of material from joint surfaces and joint bound slabs. The growth of the fault depends on the joint spacing and the competency of the host rock. In densely welded ignimbrites, joint spacing is controlled by sub-layers within the ignimbrite unit which are formed by flattening and stretching of fiamme. In moderately welded ignimbrites, fiamme and lithic inclusions in the ash matrix act as sites of joint initiation; the greater the abundance of such flaws the higher the joint frequency. Whether fault growth is promoted or inhibited depends to some extent on the competency of the material. Faults cutting ash-rich friable units have narrow fault cores regardless of displacement. This suggests that the material is easily abraded in the fault core inhibiting fracturing of the host rock and incorporation of new material. Hence host rock fabric and composition have an important influence on fault architecture in these ignimbrite units. The other influence on fault evolution is the tensile stress regime in which faulting occurs. The faults in this study form by hybrid failure and so have both vertical and horizontal displacements. The dilation of existing joints causes slip on the joints and allows material to fall into the joint forming a fault core. This work identifies distinct differences between the mechanism of dilational fault initiation and resultant fault architecture compared to that of shear faults. The observations made in this study indicate that the host rock petrophysical properties, stress regime at time of faulting (tensile or compressive) and confining pressure are primary influences on fault architecture and not displacement; contradicting the widely accepted fault thickness-displacement scaling relationship. I suggest that the architecture of dilational faults can be predicted by examining the host rock properties and using the data from this study have developed a framework that illustrates how ignimbrite host rock properties may affect deformation structures. Such frameworks for individual lithologies may be more useful in predicting fault zone properties as opposed to global scaling relationships. The results of this study have implications for conceptual models of fluid flow based on fault architectures predicted using the thickness-displacement relationship.

The phylogeny of the Family Pliomeridae and the Ordovician representatives of the Encrinuridae was investigated using cladistics. This resulted in the diagnosis of seven subfamilies; five of pliomerids (including one erected herein) and two subfamilies of encrinurid: the Cybelinae and Encrinurinae. Some 75 genera and 12 subgenera are also diagnosed on the basis of cladistic analysis of over 180 relatively complete species. This facilitated the placement of numerous incomplete or anomalous species such that the overall analysis allowed the systematic placement of over 300 species including 159 species of pliomerid and 149 species of encrinurid. The phylogenies produced by this analysis are robust, being resistant to disruption by the addition of incomplete taxa and in showing a close match between branching order and stratigraphy. A recurring evolutionary pattern is demonstrated. Very short initial periods of rapid diversification of clades, accompanied by reduced levels of character burden, were followed by steady ramification of the newly developed subclades. This pattern of development is observed to be independent of scale, occurring at all levels of systematic hierarchy. As a result many taxa are expressly paraphyletic which may be the norm in cladistic analyses. The taxa studied provided an excellent geographical and temporal spread for the investigation of Ordovician palaeobiogeography; the Pliomeridae being particularly useful of the early Ordovician, the Encrinuridae for the middle and late Ordovician. The palaeobiogeography was investigated by first elucidating the phylogeny of the clades and subclades through time and then assessing the palaeogeographical distribution of the taxa in the light of their evolutionary relationships. This palaeobiogeographical assessment was made both qualitatively and by means of geographical character optimisation and calculated gain/loss ratios. The two approaches supported each other. In addition to the detailed terrane-by-terrane results for each subclade, the following recurring patterns were observed: During the early Ordovician, Laurentia was juxtaposed to the eastern margin of Gondwana and close to areas of South America. Towards the end of the early Ordovician, Laurentia and Gondwana diverged, and did not subsequently re-approach each other during the Period although the Argentine Precordillera was situated in a position between Laurentia and Gondwana in the Llanvirn. This supports a modified version of the model of Dalziel for the early Ordovician in which Laurentia and Gondwana are close, but not in contact, but that of Scotese & McKerrow and others for the mid- and late Ordovician. Throughout the Ordovician oceanic islands provided stepping stones for faunal migration between the main continental plates.

Glasgow contains many buildings made from local ‘blond’ sandstones that are showing the legacy of 150 years of urban weathering and this decay may accelerate as climate changes in the future. Most of the blond sandstones are Carboniferous in age and comprise of micaceous quartz arenites with varying amounts of diagenetic minerals including ankerite and kaolinite. Chemical decay can be visually identified in the carbonate minerals, but the combination of quantitative X-ray microanalysis (chemistry of mineral) and Raman spectroscopy (structure of mineral) also allows chemical decay to be observed in both kaolinite and muscovite. The Raman spectroscopy shows a variation in the muscovite minerals between the outermost surface and internal region (20 mm depth), demonstrating that structural decay is occurring within the micas and reduces them to an “ionic slurry state” in a relatively short time frame. The impact of microbial colonisation on the stones was also investigated. Using osmium stained polished blocks, complimented by scanning electron microscope imaging, microorganisms were found to be living cryptoendolithically in a few samples but at very shallow depths (<2 mm). Light penetration results revealed that a thin weathered crust (<1 mm) on the surface of sandstone will restrict the transmission of light into the rock, thereby preventing the colonisation of photosynthetic microbes. As a result, most microbial communities are restricted to the stone surface but only where they will not be subjected to photo-oxidative damage, which frequently occurs during summer months. Consequently, the most extensive microbial colonisation is restricted to the sandstone’s surface and during the winter. Using novel internal microclimate monitoring technologies it was found that stone temperature and humidity is decoupled from ambient conditions. During the summer the stone interior is considerably hotter than air temperature, whilst relative humidity is generally comparable to external conditions, whereas in the winter interior temperatures are closely related to ambient conditions and relative humidity is generally much higher. To understand how sandstone buildings will react to a change in climate, current conditions were extrapolated to 2080 using predictive models for the Glasgow region and the impact of these conditions was investigated by accelerated weathering experiments in a climate chamber. Results reveal rapid granular disintegration, the rates of which are independent of grain size. Overall, this study concludes that rates of chemical decay will increase as the climate warms and becomes wetter overall, primarily iii through dissolution, decay and loss of diagenetic minerals, and the extent of microbial activity will change, but these effects will be strongly dependent on local microenvironment. Implications of these findings are that more work on conservation and preservation techniques will be very important to protect the stone-built heritage of Scotland.

The determination of calcareous chlorophyte distributional limits is via temperatures---namely isocrymal limits, because the green algae are very susceptible to cold temperatures. The calcereous green algae are today and were in the past, one of the most sensitive and useful environmental indicators. As well as being useful in distribution analysis, they are a useful part of biotic analysis in general. Calcareous green algae are mostly, but not wholly tropical in nature---they are found in shallow marine environments up to their range extent of just into temperate water masses (12&deg;C isocrymal). The Dasycladales were dominated form of calcareous alga in the Jurassic (today their role has been largely taken over by the Halimidaceae). It can be seen that in the Upper Jurassic (where there are enough datapoints to form a reasonable limit, as opposed to the Lower or Mid Jurassic) that the Halimedaceae appeared to terminate at a line slightly southwards of the Dasycladales (this compares with the modern situation of a shared termination limit). Modern calcareous Chlorophyta distributions can delimit in the 12&deg;C isocrymal water temperature boundary, and this limit can be imposed on the Jurassic Chlorophyta distribution dataset for palaeothermometry purposes. Together with selected isotope values, it is possible to estimate Jurassic isocrymes across Western Europe. This suggests the possibility of creatures such as belemnites (which are used for isotopically derived palaeotemperatures) having recorded summer temperatures in their isotopes rather than annual average. Modern algal temperature value differences (isocrymal versus summer maximum) is by &sim;10&deg;C and this change in values for the Jurassic Chlorophyta produces temperature figures equivalent to a majority of the isotopically derived temperature values.

While the results of the study presented here suggest that the evolution of rooted tracheophytes led to an increase in chemical weathering, this enhancement was relatively small compared with vegetation with small or no below-ground organs. The evolution of rooted tracheophytes during the Middle Devonian may thus have been involved in lowering atmospheric pCO2 levels

Fine-grained lithologies control the rates and pathways of migrating fluids in sedimentary basins, and as such, play an important role in the trapping and sealing of hydrocarbons in the subsurface. However, the capacity for mudstones to retain large hydrocarbon column heights is highly variable and closely linked to grain-size distribution. For petroleum explorers, bedding-scale variations in grain-size distributions diminish the potential capacity of seal units and may be instrumental in compromising otherwise effective sealing sequences. Studies presented here utilise exceptional outcrop exposures and Ocean Drilling Program (ODP) sediment cores to investigate the sedimentology and heterogeneity of mudstone seal analogues. Quantitative data regarding the thickness, interconnectivity and lateral continuity of coarser beds have been collected and evaluated in the context of specific basin settings. Based on these findings, a range of depositional and post-depositional processes which are thought to govern the distribution of coarser material in deep-water environments are discussed. Utilising ODP data archives, the impact of lithological and textural heterogeneities on diagenesis and mechanical compaction of mudstone sequences are also addressed and evaluated from the perspective of seal integrity. Outcrop studies carried out in the UK and Taranaki, New Zealand, have identified heterogeneous slope mudstone facies containing upto 40% coarse thin-beds. These discrete layers of silt and sand are often laterally continuous, ranging in thickness from millimetre- scale laminations to beds commonly 1-4 cm thick, and are shown to be below the resolution of outcrop gamma-ray spectrometry. The examination of over 7000 m of hemipelagic slope sediment from the ODP core archives indicates that discrete coarse thin-beds comprise upto 6% of the 24 sequences examined, and that background sediments vary, reflecting differing proportions of clay, silt, sand, and biogenic material. Data presented from 255 ODP and Integrated Ocean Drilling Program (IODP) wells suggests that lithology - primarily grain-size, plays a significant role in determining the depositional porosities of mudstone sediments and the rates at which they undergo compaction during shallow (<500 m) burial. It is suggested that the use of 'default' initial porosity values for hemipelagic sediments in basin models and decompaction analysis ignores a large range of natural variability, and could lead to significant analytical errors. Porosity profiles of buried slope mudstones also indicate that in shallow sequences, hemipelagic sediments do not consistently conform to trends of exponentially decreasing porosity values with depth. Deviations from well constrained trends often appear to correlate with shifts in bulk lithology, suggesting that the inherent physical properties of particular intervals are responsible for varying porosity values with depth. The diagenetic processes associated with the conversion of volcanic ash during burial are also investigated and proposed as a post-depositional mechanism capable of altering the physical properties of mudstone units. Studies presented here highlight several depositional and post-depositional processes which may be detrimental to mudstone seal quality. This work represents a series of 'pilot studies' which aim to show that a seal evaluation and risking approach which considers these factors, will better predict the character of subsurface mudstone units.

Integrated geophysical, geochemical and hydrogeological modelling techniques have been used in this PhD research study to characterise the ground contamination at four study sites. The primary aim of the research is to study the efficiency of using an integrated approach to study hydrocarbon and heavy metal contamination in the subsurface soil, geology and groundwater systems. Each of the four sites have different industrial legacies (hence types of contamination) and periods of operation. The sites in increasing age are: Bromsgrove landfill, Cathays Railway Depot, Barry Docks and Weston-Super-Mare gasworks. The geophysical methods used in this study are Electrical Resistivity imaging (IRIS) and multifrequency ground conductivity (Gem-2). These techniques can map the electrical properties of the sub-surface in both 2D and 3D. The electrical properties are then compared with independent professional geochemical sampling programmes for both soil and groundwater. The results of this project show that the geophysical methods provide a clear indication of the zones of ground contamination (hydrocarbons and heavy metals) in both 2D and 3D. Electrical resistivity/conductivity mapping using both independent techniques show consistent results. The geophysical results also show a good correlation with the geochemical sampling programmes for soil, water and gas. The results are encouraging in that geophysics could be used more widely in professional contaminated land site investigations to supplement conventional invasive techniques and sampling programmes. The research has also investigated whether geophysical parameters such as electrical conductivity could be used as a groundwater modelling parameter in the Visual Modflow software. The advantage being that geophysics can provide a high intensity of data in 3D and even temporal 4D at a site. The geophysical results can define an accurate spatial distribution of the contaminated area. This can be used to assign a ‘concentration recharge’ in the modelling compared to the normal practice of using chemical data from a small number of discrete sampling points. However this approach will still require chemical data for validation.

This research concentrates on two study areas.&nbsp; A family of blowout pipes from North Namibia imaged in 3D seismic data; and a group of large buried pockmarks and a field of small seabed pockmarks from the Western Nile Deep Sea Fan (NDSF) imaged in ultra high resolution 2D data.&nbsp; The general themes of this research are pipe and pockmark morphology and formation process, their spatial and temporal distribution and the magnitude and frequency of fluid flux through the conduit. A family of blowout pipes from Namibia exhibit a variety of seismic characteristics, with the largest pipes containing a blowout crater and evidence of possible stacked palaeo-pockmarks. Pipe formation is shown to be intermittent and persistent throughout the Neogene. The spatial position of pipes adheres to both basinal and local controls. A group of large buried pockmarks on the NDSF are interpreted to have formed between 15,000 yrs BP and 125,000 yrs BP, the majority of which are believed to have formed at the same time c. 60,000-80,000 yrs BP.&nbsp; These buried pockmarks show evidence for highly focused, episodic fluid flow following burial of the pockmark.&nbsp; The longevity of post formation fluid migration is estimated to be ~50,000-100,000 yrs. A field of > 13,800 small seabed pockmarks (Nile Deep Sea Fan) are interpreted to have formed within the last 1,000 yrs.&nbsp; Spatial statistics identified an exclusion zone or drainage cell surrounding each pockmark which is not penetrated by the formation of any other pockmark.&nbsp; A conceptual model for a drainage cell is proposed whereby pockmark formation dissipates, a radius/area of fluid and overpressure, thereby preventing the formation of another pockmark within that cell.

Few culture-based surveys have been undertaken on methanogens in contrasting marine sediments. This project conducted a comprehensive study of methanogens in a range of marine sediments including tidal-flats, a shallow bay, deep-water mud volcanoes and Guaymas Basin hydrothermal sediments. Nine of the sixteen recognised methanogen genera were cultured ranging from only one methanogen genus at mud volcano sites to eight in tidal-flats. At a number of these sites, culture-independent techniques (16S rRNA and mcrA gene sequences) had either failed to detect the presence of methanogens or had under-estimated the methanogen diversity. Acetate and hydrogen utilizing methanogens (including two strains of the genus Methanococcus) were cultured from marine sediments with high sulphate content. But by far the most abundant genus was Methanococcoides being isolated from seven of the sites investigated, including the deepest (in terms of water depth) non-thermophilic methanogens so far isolated. Study of the isolated Methanococcoides strains has extended the substrate range of the genus by identifying of two new directly utilized methylated substrates (betaine and choline). The substrate range of this genus has been further extended by demonstrating dimethylsulphide utilization, a compound only previously known as a growth substrate in closely related genera. In addition to substrate tests, representative strains from each of the sites investigated were physiology characterized including temperature, pH and Na+ concentration ranges. Members of the genus Methanococcoides are mesophilic/ psychrotolerant, neutrophilic and halotolerant. Their substrates are limited to methylated compounds. For the first time strains of mesophilic methanogens (Methanococcoides) were tested for their ability to grow under elevated hydrostatic pressure, up to 70 MPa. In conclusion, methylotrophic methanogens play an important role in marine sediment methanogenesis with the methylotrophic genus Methanococcoides being widespread. The range of methylotrophic substrates is wider than previously described and further work is required to determine the full extant of methylated compounds as substrates for methanogenesis. Molecular based studies often fail to identify the presence of methanogens that are subsequently detected in culture-based studies.