The key to understanding the future impact of the anthropogenic combustion of fossil fuels on the climate system, is to fully understand the complex feedback loops within the natural Earth system. One natural climate feedback that has been proposed is the Coral Reef Hypothesis whereby significant increases in coral reef growth may have contributed to the deglacial increase in atmospheric CO2 observed in the ice core records. This thesis examines the role of coral reefs in the oceanic carbonate budget and global carbon cycle both spatially and temporally during the Holocene. Using the most comprehensive reef area estimate to date, a conservative estimate of cumulative CaCO3 accumulation within coral reefs globally from 10 kyr BP to present is 7970 Gt. This estimate includes a temporal and spatial view of reef CaCO3 accumulation during the Holocene and represents coral reefs alone, whereas previous budgets have included wider neritic carbonate facies. This mass of reefal CaCO3 accumulation would have made approximately 2100 Gt CO2 available for release to the atmosphere over the Holocene. Radiocarbon dating of coral obtained from new drill cores from Rodrigues (Southwest Indian Ocean), Lizard Island and MacGillivray Reef (Northern Great Barrier Reef (NGBR)), helps to reveal the spatial and temporal pattern of Holocene CaCO3 accumulation within these reefs and contributes to the dataset compiled to calculate the global mass balance of coral reef carbonate. The new data presented here demonstrates that the reefs at Rodrigues, like those at Reunion and Mauritius only reached a mature state (reached sea level) by 2 to 3 ka – thousands of years later than most of the reefs in the Australasian region. The windward margins at Lizard Island and MacGillivray Reef started growing ca 6.7 and 7.6 cal kyr BP respectively directly on an assumed granite basement and reached sea level approximately 4 and 5.6 cal kyr BP respectively. The leeward margin at MacGillivray Reef was initiated by 8.2 cal kyr BP directly on a granite basement, only reaching sea level relatively recently between 260 and 80 cal yr BP. The absence of Pleistocene reefal deposits indicates the possibility that the shelf in this region may have subsided relative to modern day sea level by at least 15 m since the last interglacial (125 ka). The role of the calcareous green alga Halimeda in the marine carbonate budget is still unknown both spatially and temporally for the Holocene. Here a quantification of the carbonate mass within the ribbon reefs and Halimeda bioherms on the outer shelf of the NGBR is presented. It is estimated that Halimeda bioherms contain at least as much (possibly 400 % more) CaCO3 sediment than the adjacent ribbon reefs within the NGBR province.

The Middle Devonian Rousay Flagstone Formation of Orkney is a 200m thick lacustrine succession that contains abundant preserved organic matter. It was deposited into a series of half graben formed by the collapse of over-thickened Caledonian crust. The 14 lake cycles that comprise the Rousay Flagstone Formation (RFF) were correlated across Orkney during 6 months of fieldwork. Two of the lake cycles were sampled in detail for geochemical analysis. This work has enabled an understanding of the sedimentary and tectonic processes that controlled the distribution of facies and the quality of source rocks within the Orcadian Basin during this time. The processes and environments present in Orkney during this time may be compared to the Horton Group in Nova Scotia (Hamblin & Rust 1989). The main finding of this research has been the extent to which the East Scapa Fault (ESF) caused variation in sedimentation. By slowly extending throughout the RFF, the half graben bounding fault caused certain areas of Orkney to experience continued relative uplift. Two aspects of the structure of the half graben were of greatest influence. Firstly the uplifted footwall of the half graben provided an environment away from the influence of inflowing sediment and oxygen rich turbidity currents. The quiescent environment in this area allowed the greatest amount of laminite facies accumulation. It was found that high TOC (total organic carbon), H/C (hydrogen/carbon ratio) and spore numbers were associated with these areas of enhanced laminite deposition. The second area was a transfer zone located at the northern splay of the ESF. The zone acted as a linkage zone between the ESF and a half graben to the north. Because of its location between adjacent half graben depocentres, sedimentation was affected by the relative uplift of the area in a manner similar to the uplifted footwall area to the west ofthe ESF. The main agents that were detrimental to the formation of source rocks were turbidity currents. These currents originated from the three main areas of alluvial fan input in the basin. Turbidity currents carrying sediment and oxygenated water from these fans would bypass the shallower and more uplifted areas and preferentially deposit in the more distal and downthrown areas. The area immediately to the east of the ESF was the main location to have experienced reduction in kerogen quality (TOC, H/C and spore numbers) because of turbidite deposition. The preserved organic matter is predominantly composed of amorphous organic matter, making the main kerogen type Type I. About 40% of each Rousay Flagstone Formation lake cycle contains measurable organic matter, on average about 0.8%. The amount of organic matter is controlled by facies type, with laminite facies having the highest average TOC (1.55%) and grey silts having least (0.3%). Exinite reflectivity and spore colour variation analyses from across Orkney indicate that the thermal maturity of the sediments is within the thermal range of hydrocarbon generation. Additionally the uniform spread of maturity values across Orkney indicates that fault movement was never great enough to cause differential thermal maturity regimes to form across Orkney.

No description available.

The Easdale phyllite at Easdale, Scotland comprises; pyritic dark phyllite (Qtz + ms + chl + ab dol) and calc-phyllite, (Qtz + ms + chl + dol ab). It was deformed by the regional polyphase Caledonian D1-D3 ductile deformation and a weaker D4 phase, that comprised essentially minor crenulation and normal faulting. The S2 foliation dominates, and was accompanied by chlorite-zone, greenschist facies metamorphism and formation of Caledonian quartz veins. Intrusion of Tertiary mafic dykes, has given rise to modifications of Caledonian vein quartz microstructure and the characteristics of trapped fluid inclusions. Three groups of veins: (1) Caledonian quartz + chlorite + muscovite veins (VI), and (2) quartz (chlorite + muscovite) veins (V2), mostly concordant with regional Caledonian S2 foliation and cut by mafic dykes, and (3) post- Caledonian dolomite + calcite quartz veins parallel to sub-parallel to the dykes, occur. By petrographic analysis in a series of traverses (0-150cm) away from dykes of varying width (up to 5m) the veins are shown to contain medium (0.5-2mm) to coarse (>2mm) recrystallized equigranular quartz that becomes more equant nearer to the dykes. Close to dykes the quartz shows a bimodal grain-size distribution and linear fluid inclusion arrays that define healed micro-cracks. Two fluid inclusion populations (Types A & B) are defined based on their nature and occurrence. These are: Type A; isolated inclusions (Al) in clean quartz cores, and inclusion clusters (A2) along grain boundaries representing the initial fluid inclusion populations in the veins. (2) Type B; mostly short, straight intracrystalline trails that represent the secondary fluid inclusion populations. Both populations are aqueous fluids of very low salinity (1.65-5wt% NaCl equivalent). They are dominantly 5-10m in size and inclusions ^O!!! are uncommon. The Type A inclusions re-equilibrated at approximately 250C (219-298C) and Type B at 150C (116-200C) under 0.19-2.17kb hydrostatic pressure and have experienced systematic post-entrapment modifications with increasing proximity to dykes. Intrusion-related static recrystallization occurs and the zone affected varies systematically with dyke thickness. The mean distance of vein overheating to cause fluid inclusion modification is about 5cm from the vein-dyke contacts for thin dykes (<lm thick) and 20-30 cm near thick dykes (>lm thick). Of Type A inclusions >12m diameter, 80-100% decrepitated between 0-30cm in veins intercepted by <lm wide dykes, because overheating was high (>100C), cause overpressuring >1.0kb and induce decrepitation of inclusions in the zone. For veins intruded by 2m and 5m thick dykes the width of the zone is 0-70cm and 0-160cm respectively. This zone represents the maximum width of the veins significantly affected by heat-induced recrystallization and modification of fluid inclusions. It is established that fluid inclusion leakage is systematic and quantifiable in response to heat-induced overpressure due to dyke intrusion. Large- (>12m) and medium-size (5-12m) inclusions leaked and deformed from irregular and ellipsoidal to polygonal forms close to the vein-dyke contact. The leakage produces a decrease in density and degree of fill of early-formed fluid inclusions. This produces a spread of homogenization temperature (Th) values to higher T, such that careful interpretation is needed to avoid serious underestimate of trapping pressures (Pt). This has important implication for the interpretation of metamorphic and mineralisation events.

A continuous and unthrusted 1.2km section of latest Emsian to Frasnian sediments is exposed in the Rio Lajas at Bermejo, Santa Cruz Province, Bolivia. One hundred and forty-five samples were taken from this section to validate the cuttings-based Devonian subsurface palynostratigraphy. Similar palynological trends were identified in the same stratigraphic order as seen in the subsurface. A detailed study of the chitinozoan fauna was undertaken and 36 taxa were identified of which 9 are new but retained in open nomenclature pending formal description. Only 3 of the chitinozoan taxa are cosmopolitan. The palynostratigraphy from Bermejo for the first time is tied to accurate lithostratigraphy and this data was used to revise the Devonian stratigraphy at the Campo Redondo and Cha-Kjeri sections in Chiquisaca Province. Mid Devonian age assignments for the economically important Devonian Huamampampa Formation reservoir are not valid, since the new palynology indicates a mainly Early Devonian (Emsian) age. There is sedimentological evidence in the basal Los Monos Formation for an early Eifelian marine transgression associated with the important acritarch Evittia sommeri. In Bolivia and South America, due to the near/effective absence of conodonts and goniatites, the Devonian Euramerican sea-level curve is relatively untested. However, a possible candidate for the Chotec Event is the basal Los Monos Formation transgression. This is the only major transgressive event during the early Eifelian. Assuming similar stratigraphic trends to Bolivia, attempts were made to find E. sommeri at the Chotec level in Euramerica. A total of 158 Emsian/Eifelian samples were collected and processed for palynology from the Czech Republic, Morocco, Spain and the UK with additional non-Euramerican samples from Russia . E. sommeri was not found. While 2 younger Devonian marine transgressions are recorded in Bolivia (mid-late Givetian and earlyFrasnian), the major flooding event around the Eifelia n/Givetian boundary in Euramerica (Kacák Event) is notably absent. This is important since the Kacák Event has been implicated in the break-up of the high latitude, cool water Malvinokaffric Realm that included Bolivia.

This thesis describes the development of analytical methods for both the bulk determination of 99Tc, and determination of 99Tc in sequential extracts from sediments. These methods have been used to collect data, which, along with trace and major element data have been used to interpret the mechanisms for 99Tc input, migration and accumulation in saltmarshes. The inventory of 99Tc stored in the Thornflatt Saltmarsh, Esk Estuary has also been determined. The routine determination of 99Tc in bulk samples uses 99mTc as a yield monitor. Samples are ignited stepwise to 550C and the 99Tc is extracted using 8M nitric acid. Many contaminants are precipitated with Fe(OH)3 and the Tc in the supernant is pre-concentrated and further purified using anion-exchange chromatography. Final separation of Tc from Ru is achieved by extraction of Tc into 5% TnOA in xylene from 2M sulphuric acid. The yield is determined by ?-spectrometric analysis of 99mTc. Determination of 99Tc is made by liquid scintillation counting. Typical recoveries are in the order of 70-95% and the method has a detection limit of 1.7 Bq/kg for a sample size of lOg. Determination of Tc in sequential extracts uses operationally defined procedures to extract: exchangeable Tc, reducible Tc and oxidisable Tc. An initial water wash is used to extract any occluded Tc and a final leach in 8 M nitric acid is used to dissolve any residual Tc. The isolation of 99Tc uses TEVA resin for Extracts 1-4 and the decontamination procedure developed for bulk analysis for Extract 5. "mTc was used as a yield monitor, and determination of "Tc is by liquid scintillation counting. Limits of detection were dependent on the amount of 99mTc tracer used but were found to be as low as 2.4 Bq/kg for a sample size of 2g. A study was made of the mechanisms responsible for the accumulation and migration of Tc in estuarine sediments using sediments collected from saltmarshes at Thornflatt, Carlaverock and the Ribble Estuary. 99Tc was present at determinable activities in all the sediment cores taken from these sites. Good correlations between Tc and CaO as well as CO3 concentrations and poor correlation between Tc and radionuclides adsorbed to inorganic detritus infer a direct input of 99Tc to marsh sediments. Determination of 99Tc in biota living on the marsh also showed that this was not a significant pathway for input of Tc to the sediments. Sequential extraction data imply sorption to an organic fraction of the sediment. Stable element and sequential extraction data indicates that Tc is readily oxidised and remobilised before reprecipitation where redox conditions are favourable. Data indicate a reduction potential between those of the MnIV to Mn" reaction and the Fe1" to Fe" reaction is necessary for re-accumulation to occur, as suggested by published thermodynamic data. Data collected from reducing sediments imply that similar mechanisms are responsible for the accumulation of Mn (e.g. reduction by sulphate reducing bacteria) and the accumulation of Tc. The inventory of 99Tc held within the Thornflatt saltmarsh is proportionally less than that of 137Cs or 24lAm when compared to discharges from Sellafield. However a higher proportion of 99Tc is transferred from Seliafield and incorporated into saltmarsh sediments than is suggested by previously published standard distribution coefficient data. Saltmarsh sediments are therefore a more important sink of 99Tc than extrapolations made from inventories of other radionuclides would suggest.

No description available.

The earliest Carboniferous deposits, resting with profound unconformity on Lower Palaeozoic rocks, have been mapped across their entire outcrop area on the Askrigg Block. The sediments, comprising approximately half of the thickness of the Dinantian Great Scar Group, have been subdivided into four formations listed in ascending stratigraphlcal order:- the Thornton Force Formation and its lateral equlvalent the Douk Gill Formation, the Raven Ray Formation and finally, the Horton Limestone. Each of these formations has been described in great detail, noting the variations in thickness and the various rock-types contained therein. This data has been used to identify sixteen rock-types which occur in at least one and usually in all of the studied formations. The depositional environment of each of these rock-types has been interpreted by means of palaeoenvironmental analysis of the fossil groups and sedimentary structures present and from the distribution of each of the rock-types. The diagenetic history of the carbonates has been studied by means of staining techniques. The earliest deposits of the Thornton Force Formation were formed in a marginal marine environment. Although beach-nearshore sediments accumulated in an active environment, inundation of the Askrigg Block appears to have been a gradual and gentle process, allowing local preservation of soils and debris flow deposits in more protected pockets and hollows. The ridges of Lower Palaeozoic rock supplied detritus throughout deposition of nearshore shallow subtidal calcarenltes of the formation. The Douk Gill Formation, restricted in outcrop to a local topographic hollow in Ribblesdale, is probably a lateral equivalent of the Thornton Force Formation. A ridge of Lower Palaeozoic rocks provided a protective barrier, allowing clastlc and later carbonate sediments to accumulate in the sheltered environment. Infilling of the lagoon resulted in the formation of tidal flats, and culminated in subaerial exposure and the development of a thin coal. During deposition of the Raven Ray Formation a shelf-edge shoal must have formed, separating the Pennine Basin from the normal marine shelf lagoon of lime mud deposition. Small shoals occasionally developed in the extensive lagoon environment. Shoreline deposits formed around those Lower Palaeozoic rldges which perSisted as islands. The Horton Limestone represents an episode of deposition predominantly of cross-laminated calcarenites formed within surge depth. Eventually, shelf-edge shoals created a barrier which separated the Pennine Basin from a restricted marine, shallow lagoon of lime mud deposition. Gradual infilling of the lagoon led to the creation of a tidal flat environment. Tidal channels were common in this environment. Periodically the barrier shoals were breached and the lagoon-tidal flat environment overwhelmed by carbonate sand. The principal mechanisms controlling sedimentation have been discussed. During the initial stages of inundation, the topography of the pre-Carboniferous rocks exerted a significant but dwindling influence on the rock-types deposited and on their distribution. Burial of the land surface eliminated this effect and the rates of sedimentation and subsidence became the most significant mechanisms controlling the type and distribution of Dinantian sediments.

Late Holocene (c. 2100 yr BP) varved sediments recovered from Saanich Inlet, Ocean Drilling Program Leg 169S, have been analyzed using high resolution scanning electron microscope techniques. The individual centimetre-scale varves comprise two segments: a biogenic varvesegment which consists of up to 19 alternating diatom ooze and diatomaceous mud laminae, which were deposited during spring through autumn; and a terrigenous varve-segment containing up to 6 laminae dominated by silty clay, which were deposited during winter. The laminae within the varves record individual flux events of a few weeks to months duration. Diatom flux typically reached the fjord floor as a mixture of whole/fragmented aggregates and Zooplankton faecal pellets. The diatom succession within the biogenic varve-segment typically comprises: an early spring Thalassiosira spp. bloom, followed by a late spring Chaetoceros spp. -dominated bloom, a late spring/early summer Skeletonema costatum bloom and a series of one to several summer/autumn Chaetoceros spp. -dominated blooms. Interannual variability in diatom sediment flux is typically recorded by the presence/absence of Thalassiosira spp., S. costatum and the number of summer/autumn Chaetoceros spp. - dominated blooms. The varved sediment documents a major increase in the sedimentation rate at approximately 2100 varve yr BP. This represents a transition from a colder/drier climate during the Tiedmann glacial advance when sediment flux was lower, to a relatively warmer/wetter late Holocene climate when sediment flux increased. As glaciers receded, fluvial input increased throughout the year as a result of increased rainfall during winter months and glacial meltwater during spring through autumn months. This increased fluvial input introduced additional terrigenous sediment throughout the year and additional nutrients enhancing diatom production during spring through autumn. The varved sequence is punctuated by centimetre-scale massive intervals originating from low density turbidity currents initiated above the anoxic zone. A tephra laminae containing volcanic glass has also been observed and might originate from Mount St Helens. Spectral analyses of inter-varve variability in sediment fluxes have shown strong periodicities within El Nino Southern Oscillation (ENSO), Quasi-Biennial Oscillation (QBO) and North Pacific Oscillation (NPO) bands. Thalassiosira spp. flourished in the more stable conditions associated with strong La Nina-type phases of the ENSO cycle. S. costatum blooms were associated with El Nino events when winter storms increased levels of ground water storage, which subsequently increased fluvial input of nutrients during the late spring/early summer. The summer/autumn Chaetoceros spp. blooms were dominated by the NPO, as successive years of increased rainfall/snowfall associated with the colder/wetter NPO regime increased long term mean levels of ground water storage and accumulation of snow, which subsequently increased fluvial input of nutrients during summer and autumn months. Winter terrigenous flux was dominated by NPO at Site 1033 and ENSO at Site 1034. Site 1033 which is the most distal to the terrigenous source, records increased/decreased fluvial input associated with the wetter/dryer regimes of NPO. Site 1034, records the effects of El Nino storms which rework nearshore sediments and deposit them in the deeper offshore regions. QBO frequencies are recorded in the overall sediment flux and biogenic sediment flux at Site 1033 and may represent the alternation of a relatively weaker/s"tronger Aleutian Low Pressure System causing consecutive years to be relatively wetter and drier, affecting sediment fluxes. ENSO operated at approximately 3.5 years, with stronger events occurring at approximately 9 year intervals; QBO operated at approximately 2.4 years; and NPO operated at approximately 15 years. Multi-decadal periodicities of 31 and 42 years are also recorded and might represent stronger NPO regimes.

Archaeological investigation of the shallow coastal environment has traditionally been conducted through exclusively marine or terrestrial methods, creating artificial division between sites located in the intertidal and subtidal zones. This thesis demonstrates a successful seamless inter-disciplinary survey methodology, utilising side scan sonar, sub-bottom profilers, aerial photography and archaeological field inspection to establish the correct spatial and contextual relationships of submerged archaeological structures. To facilitate survey of the shallow intertidal zone, a novel catamaran-based platform is developed, which carries side scan and Chirp sub-bottom sonar systems, and is proved operational in water depths greater than 1.3m and 2.4 m respectively. Digital survey technologies offer the potential for post-survey signal enhancement of high-frequency seismic data. Investigation into the characteristics of commercial Chirp and Boomer seismic indicates that Chirp systems offer superior repeatability and vertical resolution, making possible development of a rapid, robust processing flow for high-resolution investigation of sediment structure. Development of shoreface exploitation sites is strongly controlled by interaction between contemporary physical processes and the underlying geomorphology. High resolution seismic techniques are used here to study the drumlins, late-Quaternary seismic stratigraphy and relative sea level history of Strangford Lough, Northern Ireland. Unique seismic sections through submerged late- Midlandian (Devensian) drumlins, parallel to the direction of ice flow, indicate that adjacent drumlins share a common internal structure and are preferentially located over subtle topographic maxima in the underlying substrate. A high-resolution seismo-stratigraphy is developed from Chirp profiles through the northern lough. Correlation with field observations, cores and published RSL data from the Irish Sea suggests that Strangford Lough underwent isolation from the sea during the early Holocene, implying that early Mesolithic settlers were attracted to the area by an exploitable freshwater, rather than marine resource. The intertidal mudflats of the Blackwater Estuary contain an extensive, but largely inaccessible and rarely exposed archaeological resource, including wooden coastal fish weirs dated to Saxon times. Application of side scan sonar to areas previously photographed during aerial reconnaissance has facilitated accurate mapping of six large (100-2000m length) structures, increasing the site record content up to 250%, and improving understanding of the manner in which these structures operated. Structures on the southern shore of the estuary extend into the subtidal zone to c. -2m OD. It is suggested that the lower altitudes of these sites imply a significantly earlier date for development of this fishing technique than presently accepted.