Micromorphological studies of the leaf cuticle in selected laurales

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Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland

Globally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation

Environmental change, trilobite extinction and massive volcanism at the Cambrian Series 2 – Series 3 boundary

The Cambrian Series 2 – Series 3 boundary (~509 Ma) was a dynamic interval marked by a major perturbation to the global carbon cycle; widespread sea level fall (Sauk Supersequences); the eruption of the Kalkarindji large igneous province and the extinction of the dominant trilobites- the olenellids of Laurentia and the redlichiids of Gondwana. This thesis investigates the relative timing of these phenomena from field sites across the Laurentian and Gondwanan palaeocontinents, assessing the severity of environmental change coinciding with extinction. We report that the Redlichiid-Olenellid Extinction Carbon isotope Excursion (ROECE) coincides with the Series 2 – Series 3 boundary in Laurentian sections (NW Scotland, SW USA), though only in the SW USA does ROECE co-occur with the trilobite extinction. Scottish successions of this age are hindered by a lack of fossils, and as such the exact timing of ROECE relative to the extinction is unclear. New evidence presented in this thesis shows a variable record of anoxia at the extinction horizon, the most severe manifestation indicates euxinic conditions during the extinction at Ruin Wash, Pioche Formation, Nevada. Elsewhere in the SW USA and NW Scotland, there is evidence for periodic dysoxia (e.g. basal Ghrudaidh Formation, Durness Group, Scotland and Carrara Formation, SW USA) at the Series 2 – Series 3 boundary and extinction interval. Facies analysis reveals that on Laurentia, ROECE and the extinction horizon occur during the transgressive phase of the Sauk II supersequence. To investigate the temporal relationship between the Series 2 – Series 3 boundary, ROECE, extinction and Kalkarindji eruptions, this thesis presents new Hg data as a proxy for volcanism. On Laurentia the data show an inconsistent relationship between these phenomena, whilst on Gondwana a new preliminary study shows evidence for Hg enrichments at this interval, establishing it as a site to further investigate the sedimentary trace of volcanism

JOHN HARRISON: HIS MAJESTY'S AGENT IN MOROCCO, 1610-1632.

John Harrison, a one time member of the court of Henry, Prince of Wales, was England's agent in Morocco on eight occasions between 1610 and 1632. The author of six books and of many reports on Morocco written for the secretaries of state, he was a committed Protestant and millenarian. He was an unusual choice of agent, becoming best known to posterity for ransoming English captives from slavery. His peers went to the Levant, India and the Far east; their experiences are well known, while Harrison's are not. His considerable relations, written for Charles I and his secretaries of state, are a valuable resource for students of Moroccan history. In my consideration of Harrison's commissions, my thesis will demonstrate that Morocco was a significant area of interest to England, her statesmen and merchants, in the early seventeenth century. An understanding of Anglo-Moroccan relations and Harrison's experiences in Morocco at this crucial time should contribute to our understanding of the evolving nature of the expansionist English engaged in diplomacy, trade, settlement and conversion. My thesis will analyse Harrison's missions with the intention of understanding how his personal beliefs, very deeply held, aligned with national aspirations and the results therefrom. To do this I will consider the political landscape of Europe and Britain's place in it, the expectations attached to his commissions, his successes and failures, and compare his experiences with other English agents, both in Europe and further afield. My chapters will paint a comprehensive picture of Harrison, Anglo-Moroccan relations and site them in the western Mediterranean of the early seventeenth century. I start, in chapter one, with the political, social and religious environment in England in 1610. Chapter two discusses Harrison's publications and their relevance to his personal development and to his missions. Chapters three and four cover Harrison's missions: the first four (1610-1618) in chapter three, during which he identifies the diplomatic boundaries to achieving success in Morocco; the second four (1625-1632) in chapter four during which Harrison has to confront the issues surrounding the situation in Morocco, his lack of support from England and his religious convictions. I conclude that looking at Harrison's work in Morocco contributes to our understanding of how agents abroad worked to extend English influence outside early seventeenth century Europe

Mercury chemostratigraphy across the Cambrian Series 2 – Series 3 boundary: evidence for increased volcanic activity coincident with extinction?

Flood basalt volcanism represented by the Kalkarindji Province (Australia) is temporally associated with a trilobite mass extinction at the Cambrian Series 2 – Series 3 boundary, providing one of the oldest potential links between volcanism and biotic crisis in the Phanerozoic. However, the relative timing of flood basalt volcanism (Kalkarindji Province, Australia) and the trilobite extinctions, first recorded in North America, is not known. Mercury (Hg) enrichment in the sedimentary record provides a potential proxy for volcanism which may facilitate improved chronologies of eruption and extinction. Here we report mercury records for three sections from mid-shelf strata of the Great Basin (western USA) that straddle the Series 2 – Series 3 boundary. One section (Oak Springs Summit, NV) features a Hg enrichment at the start of the extinction interval, but mercury anomalies are also present at lower levels. These older anomalies may record either earlier phases of Kalkarindji volcanism, eruptions in other locations, or may be the result of sedimentary and/or diagenetic processes affecting the Hg record. In the Carrara Formation at Emigrant Pass, CA, the precise extinction horizon is not well defined, but a carbon isotope anomaly (the Redlichiid-Olenellid Extinction Carbon isotope Event; ROECE) provides a stratigraphic tie point to the Oak Springs Summit section. At Emigrant Pass, Hg enrichments precede the ROECE interval and are absent in the inferred extinction zone. The Pioche Formation at Ruin Wash, NV, lacks Hg enrichment at the extinction horizon but contains older enrichments. The inconsistent Hg records between the three sections demonstrate that factors controlling Hg accumulation and preservation in marine sedimentary environments are not yet fully understood. The effects of redox fluctuations may complicate one-to-one association of sedimentary Hg enrichments and massive volcanism at the Cambrian Series 2 – Series 3 boundary and elsewhere in the geologic record

Trilobite extinctions, facies changes and the ROECE carbon isotope excursion at the Cambrian Series 2 - 3 boundary, Great Basin, western USA

The mass extinction of the olenellid trilobites occurred around the Cambrian Series 2 - Series 3 boundary. Like many other crises, it coincided with a negative carbon isotope excursion but the associated palaeoenvironmental changes remain unclear. To investigate the causal mechanism for this event, we report facies changes, pyrite framboid petrography and carbon isotope values from Cambrian Series 2 - Series 3 (traditionally Early - Middle Cambrian) boundary strata of the Carrara 20 Formation (Death Valley region, California) and Pioche Formation (Nevada). These data reveal regionally changing water depths from high-energy, nearshore facies (oolitic grainstone) to more offshore silty marl and finer-grained carbonate mudstone. In the Carrara Formation, the series boundary occurs within a deepening succession, transitioning from high-energy, nearshore facies (oolitic grainstone and oncolitic packstone) to offshore marl, the latter of which contains pyrite framboid populations indicative of low-oxygen (dysoxic) depositional conditions. Intermittent dysoxia persisted below sub-wave base settings throughout the early and middle Cambrian, but did not intensify at the time of extinction, arguing against anoxia as a primary cause in the olenellid trilobite extinction. Within both field areas, the extinction interval coincided with a minimum in d13Ccarb values, which we interpret as the regional manifestation of the Redlichiid-Olenellid Extinction Carbon isotope Excursion (ROECE). The Series 2 - Series 3 boundary is reported to closely coincide with a large-amplitude sea-level fall that produced the Sauk I/II sequence boundary, but the placement of the Series 2 - Series 3 boundary within a transgressive interval of the Carrara Formation shows that this is not the case. The main sequence boundary in the succession occurs much lower in the succession (at the top of the Zabriskie Quartzite) and therefore precedes the extinction of the olenellids and ROECE

Sequence Stratigraphy, Chemostratigraphy and Facies Analysis of Cambrian Series 2 - Series 3 Boundary Strata in Northwestern Scotland

Globally, the Series 2 - Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I - Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive-transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation

New ⁴⁰Ar/³⁹Ar dating of the Antrim Plateau Volcanics, Australia: clarifying an age for the eruptive phase of the Kalkarindji continental flood basalt province

The Kalkarindji flood basalt province of northern Australia erupted in the mid-Cambrian. Today the province consists of scattered volcanic and intrusive suites, the largest being the Antrim Plateau Volcanics (APV) in Northern Territory. Accurate dating of Kalkarindji has proved challenging with previous studies focused on minor volcanics and intrusive dykes in Northern Territory and Western Australia. These previously published data, corrected to the same decay constants, range from 512.8 to 509.6 ± 2.5 Ma [2σ], placing Kalkarindji in apparent synchronicity with the Cambrian Stage 4–5 biotic crisis at 510 ± 1 Ma. This study utilises 40Ar/39Ar dating of basalts from the APV to accurately date the major volcanic eruptions in this province. Results yield an age of 508.0–498.3 ± 5.5 Ma [2σ], indicating the APV is younger than the intrusives. These dates allude to a relative timing discrepancy, where intrusive activity in the North Australian Craton preceded the eruption of the APV as the last magmatic activity in the region. The determination of these largest eruptions to be later than 510 Ma, effectively disassociates Kalkarindji lavas from being a major cause of the 510 Ma biotic crisis, but cannot definitively discount any deleterious effects on the fragile Cambrian ecosystem

Time-lapse imaging of CO2 migration within near-surface sediments during a controlled sub-seabed release experiment

The ability to detect and monitor any escape of carbon dioxide (CO2) from sub-seafloor CO2 storage reservoirs is essential for public acceptance of carbon capture and storage (CCS) as a climate change mitigation strategy. Here, we use repeated high-resolution seismic reflection surveys acquired using a chirp profiler mounted on an autonomous underwater vehicle (AUV), to image CO2 gas released into shallow sub-surface sediments above a potential CCS storage site at 120 m water depth in the North Sea. Observations of temporal changes in seismic reflectivity, attenuation, unit thickness and the bulk permeability of sediment were used to develop a four-stage model of the evolution of gas migration in shallow marine sediments: Proto-migration, Immature Migration, Mature Migration, and Pathway Closure. Bubble flow was initially enabled through the propagation of stable fractures but, over time, transitioned to dynamic fractures with an associated step change in permeability. Once the gas injection rate exceeded the rate at which gas could escape the coarser sediments overlying the injection point, gas began to pool along a grain size boundary. This enhanced understanding of the migration of free gas in near-surface sediments will help improve methods of detection and quantification of gas in subsurface marine sediments

Towards improved monitoring of offshore carbon storage: A real-world field experiment detecting a controlled sub-seafloor CO2 release

Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (∼3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt