ORCID Profile
0000-0003-2399-4194
Current Organisations
University of Bristol
,
Geological Survey of Western Australia
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Publisher: Wiley
Date: 10-05-2013
DOI: 10.1111/JSAP.12081
Publisher: Oxford University Press (OUP)
Date: 31-07-2022
DOI: 10.1093/GJI/GGAC294
Abstract: A blanket of sedimentary and regolith material covers approximately three-quarters of the Australian continent, obscuring the crustal geology below and potential mineral resources within. Sedimentary basins also trap seismic energy increasing seismic hazard and generating noisy seismograms that make determining deeper crustal and lithospheric structure more challenging. The most fundamental question that can first be asked in addressing these challenges is how thick are the sediments? Borehole drilling and active seismic experiments using a controlled seismic source (e.g. vibroseis) provide excellent constraints, but they are limited in geographical coverage due to their expense, especially when operating in remote areas. On the other hand, passive-seismic experiments that involve the deployment of seismic receivers only (i.e. seismometers) are relatively low-cost and portable, providing a practical alternative for initial surveys. Here we utilize receiver functions obtained for both temporary and permanent seismic stations in South Australia, covering regions with a erse sediment distribution. We present a straightforward method to determine the basement depth based on the arrival time of the P-converted-to-S phase generated at the boundary between the crustal basement and sedimentary strata above. Utilizing the available borehole data, we establish a simple predictive relationship between Ps arrival time and the basement depth, which could then be applied to other sedimentary basins with some consideration. The method is found to work best for Phanerozoic sediments and offers a way to determine the sediment–basement interface in unexplored areas requiring only temporary seismic stations deployed for & 6 months.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Wiley
Date: 08-2013
Publisher: Wiley
Date: 24-06-2014
DOI: 10.1111/JSAP.12242
Abstract: Probiotics are frequently used in the treatment of gastrointestinal diseases in pet rabbits based largely on anecdotal evidence of a beneficial effect. However, there has been little work performed to assess any such benefit in health or disease. The aim of this study was to determine the effect of probiotics on faecal levels of four important candidate gastrointestinal bacteria (Bacteroides species, Enterococcus faecium, Fibrobacter succinogenes and Clostridium spiroforme) in pet rabbits. Additional aims were to evaluate the effect of probiotics on bodyweight and faecal weight and diameter. Double-blind triple cross-over study in six healthy rabbits orally administered two probiotic strains, Saccharomyces cerevisiae NCYC Sc47 and E. faecium NCIMB 30183. Levels of bacteria in faecal pellets were subsequently determined by real-time quantitative polymerase chain reaction. Oral administration of probiotic E. faecium NCIMB 30183 was associated with a significant (P = 0 · 042) increase in faecal levels of E. faecium. However, probiotic treatment did not affect faecal levels of Bacteroides species, F. succinogenes or C. spiroforme, bodyweight, or faecal weight and diameter. The inclusion of dietary probiotic supplementation using E. faecium NCIMB 30183 can increase faecal levels of certain bacterial flora of healthy adult rabbits. Further work is required to investigate the effects of probiotics in animals affected with gastrointestinal disease.
Publisher: Elsevier BV
Date: 02-2014
Publisher: Oxford University Press (OUP)
Date: 28-01-2011
Publisher: Oxford University Press (OUP)
Date: 09-08-2018
DOI: 10.1093/GJI/GGY331
Publisher: Oxford University Press (OUP)
Date: 19-04-2018
DOI: 10.1093/GJI/GGY158
Publisher: American Geophysical Union (AGU)
Date: 29-03-2022
DOI: 10.1029/2021JB023325
Abstract: We examine upper mantle anisotropy across the Antarctic continent using 102 new shear wave splitting measurements obtained from teleseismic SKS, SKKS, and PKS phases combined with 107 previously published results. For the new measurements, an eigenvalue technique is used to estimate the fast polarization direction and delay time for each phase arrival, and high‐quality measurements are stacked to determine the best‐fit splitting parameters at each seismic station. The ensemble of splitting measurements shows largely NE‐SW‐oriented fast polarization directions across Antarctica, with a broadly clockwise rotation in polarization directions evident moving from west to east across the continent. Although the first‐order pattern of NE‐SW‐oriented polarization directions is suggestive of a single plate‐wide source of anisotropy, we argue the observed pattern of anisotropy more likely arises from regionally variable contributions of both lithospheric and sub‐lithospheric mantle sources. Anisotropy observed in the interior of East Antarctica, a region underlain by thick lithosphere, can be attributed to relict fabrics associated with Precambrian tectonism. In contrast, anisotropy observed in coastal East Antarctica, the Transantarctic Mountains (TAM), and across much of West Antarctica likely reflects both lithospheric and sub‐lithospheric mantle fabrics. While sub‐lithospheric mantle fabrics are best associated with either plate motion‐induced asthenospheric flow or small‐scale convection, lithospheric mantle fabrics in coastal East Antarctica, the TAM, and West Antarctica generally reflect Jurassic—Cenozoic tectonic activity.
Publisher: Seismological Society of America (SSA)
Date: 31-07-2013
DOI: 10.1785/0120120276
Publisher: American Geophysical Union (AGU)
Date: 11-2019
DOI: 10.1029/2019GC008459
Publisher: Seismological Society of America (SSA)
Date: 07-09-2016
DOI: 10.1785/0220160112
Publisher: Elsevier BV
Date: 07-2019
Publisher: International Federation of Digital Seismograph Networks
Date: 2016
DOI: 10.7914/SN/1D_2016
Publisher: Authorea, Inc.
Date: 08-07-2023
DOI: 10.22541/ESSOAR.168881742.29827772/V1
Abstract: Rapid plate motion, alongside pronounced variations in age and thickness of the Australian continental lithosphere, make it an excellent location to assess the relationship between seismic anisotropy and lithosphere-asthenosphere dynamics. In this study, SKS and PKS shear-wave splitting is conducted for 176 stations covering the transition from the South Australian Craton to eastern Phanerozoic Australia. Comparisons are made with models of lithospheric thickness as well as numerical simulations of mantle flow. Splitting results show uniform ENE-WSW aligned fast directions over the Gawler Craton and broader South Australian Craton, similar to the orientation of crustal structures generated during an episode of NW-SE directed compression and volcanism ~1.6 billion years ago. We propose that heat from volcanism weakened the lithosphere, aiding widespread lithospheric deformation, which has since been preserved in the form of frozen-in anisotropy. Conversely, over eastern Phanerozoic Australia, fast directions show strong alignment with the NNE absolute plate motion. Overall, our results suggest that when the lithosphere is thin ( km), lithospheric contributions are minimal and contributions from asthenospheric anisotropy dominate, reflecting shear of the underlying mantle by Australia’s rapid plate motion above. Further insights from geodynamical simulations of the regional mantle flow-field, which incorporate Australian and adjacent upper mantle structure, predict that asthenospheric material would be drawn in from the south and east towards the fast-moving continental keel. Such a mechanism, alongside interactions between the flow field and lithospheric structure, provides a plausible explanation for smaller-scale anomalous splitting patterns beneath eastern Australia that do not align with plate motion.
Publisher: Cambridge University Press (CUP)
Date: 15-03-2018
DOI: 10.1017/S0954102018000068
Abstract: Measurements of snow accumulation are critical for reliable prediction of future ice mass loss and hence projections of sea level change. However, there are currently very few published in situ measurements of snow accumulation in the Pine Island–Thwaites glacier catchment of the Amundsen Sea Embayment, and none from low elevation sites west of 100.77° longitude. Here measurements of snow accumulation over an 11 month period in 2016 are reported for six sites in the Pine Island–Thwaites glacier catchment. The average accumulation rates of 0.10±0.01 to 1.26±0.22 m w.e. yr -1 are comparable with those derived from airborne radar for the period 1985–2009, suggesting very high rates of snowfall, particularly in the vicinity of the grounding line.
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Geophysical Union (AGU)
Date: 03-2020
DOI: 10.1029/2019JB017823
Abstract: The upper mantle and transition zone beneath Antarctica and the surrounding oceans are among the poorest‐imaged regions of the Earth's interior. Over the last 15 years, several large broadband regional seismic arrays have been deployed, as have new permanent seismic stations. Using data from 297 Antarctic and 26 additional seismic stations south of ~40°S, we image the seismic structure of the upper mantle and transition zone using adjoint tomography. Over the course of 20 iterations, we utilize phase observations from three‐component seismograms containing P , S , Rayleigh, and Love waves, including reflections and overtones, generated by 270 earthquakes that occurred from 2001–2003 and 2007–2016. The new continental‐scale seismic model (ANT‐20) possesses regional‐scale resolution south of 60°S. In East Antarctica, thinner continental lithosphere is found beneath areas of Dronning Maud Land and Enderby‐Kemp Land. A continuous slow wave speed anomaly extends from the Balleny Islands through the western Ross Embayment and delineates areas of Cenozoic extension and volcanism that span both oceanic and continental regions. Slow wave speed anomalies are also imaged beneath Marie Byrd Land and along the Amundsen Sea Coast, extending to the Antarctic Peninsula. These anomalies are confined to the upper 200–250 km of the mantle, except in the vicinity of Marie Byrd Land where they extend into the transition zone and possibly deeper. Finally, slow wave speeds along the Amundsen Sea Coast link to deeper anomalies offshore, suggesting a possible connection with deeper mantle processes.
Publisher: Wiley
Date: 19-07-2022
Publisher: Wiley
Date: 10-2021
Publisher: American Geophysical Union (AGU)
Date: 02-2021
DOI: 10.1029/2020GC009471
Abstract: We have located 117 previously undetected seismic events mainly occurring between 2015 and 2017 that originated from glacial, tectonic, and volcanic processes in central West Antarctica using data recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations. The seismic events, with local magnitudes ( M L ) ranging from 1.1 to 3.5, are predominantly clustered in four geographic regions the Ellsworth Mountains, Thwaites Glacier, Pine Island Glacier, and Mount Takahe. Eighteen of the events are in the Ellsworth Mountains and can be attributed to a mixture of glacial and tectonic processes. The largest event noted in this study was a mid‐crustal (∼19 km focal depth M L 3.5) normal mechanism earthquake beneath Thwaites Glacier. We also located 91 glacial events near the grounding zones of Thwaites Glacier and Pine Island Glacier that are predominantly associated with time periods of significant calving activity. Eight events, likely arising from volcano‐tectonic processes, occurred beneath Mount Takahe. Using Pn travel times from the seismic events, we find laterally variable uppermost mantle structure in central West Antarctica. On average, the Ellsworth Mountains are underlain by a faster mantle lid ( V Pn = ∼8.4 km/s) compared to the Amundsen Sea Embayment region ( V Pn = ∼8.1 km/s). Within the Amundsen Sea Embayment itself, we find mantle lid velocities ranging from ∼8.05 to 8.18 km/s. Laterally heterogeneous uppermost mantle structure, indicative of variable thermal and rheological structure, likely influences both geothermal heat flux and glacial isostatic adjustment spatial patterns and rates within central West Antarctica.
Publisher: Oxford University Press (OUP)
Date: 16-12-2016
DOI: 10.1093/GJI/GGV492
Publisher: Oxford University Press (OUP)
Date: 04-2017
DOI: 10.1093/GJI/GGX133
Publisher: Wiley
Date: 24-01-2013
DOI: 10.1111/JSAP.12007
Abstract: A seven-year-old, ovariohysterectomised female dwarf lop rabbit (Oryctolagus cuniculus) was referred with severe swelling and erythema of the mucocutaneous junctions of the lips, nares and vulva. Bilateral, severe periocular dermatitis was also present. Heavy pure growths of a member of the Staphylococcus intermedius group were cultured from nasal and aural swabs and skin biopsies. Other possible differential diagnoses were eliminated by standard tests. The clinical features and histopathological characteristics of the biopsies were most consistent with mucocutaneous pyoderma, a dermatosis previously reported in dogs but not in rabbits. Treatment of the bacterial infection with oral marbofloxacin and topical ofloxacin eye drops together with supportive therapy resulted in resolution of the lesions. To the authors' knowledge, this is the first report of mucocutaneous bacterial pyoderma, similar to mucocutaneous pyoderma of dogs, in a rabbit.
Publisher: Seismological Society of America (SSA)
Date: 26-12-2018
DOI: 10.1785/0120170180
Publisher: American Geophysical Union (AGU)
Date: 20-07-2018
DOI: 10.1029/2018GL077830
Publisher: American Geophysical Union (AGU)
Date: 05-2020
DOI: 10.1029/2020GC008985
Publisher: Wiley
Date: 08-2013
DOI: 10.1136/VR.101218
Abstract: A retrospective study compared invasive (arterial blood gas analysis) and non-invasive (capnography and pulse oximetry) methods of monitoring respiratory function in conscious rabbits. Arterial s les from 50 healthy dwarf lop rabbits, presenting for routine surgical neutering, were analysed on a point-of-care blood gas analysis machine. Reference intervals were obtained for pH (7.35-7.54), PaCO2 (mm Hg) (25.29-40.37), PaO2 (mm Hg) (50.3-98.2), base excess (mmol/l) (6.7-6.5), HCO3 (mmol/l) (17.96-29.41), TCO2 (mmol/l) (18.9-30.5). SaO2 (per cent) (88.8-98.0), Na (mmol/l) (137.6-145.2), K (mmol/l) (3.28-4.87), iCal (mmol/l) (1.64-1.94), glucose (mmol/l) (6.23-10.53), haematocrit (per cent) (23.3-40.2) and haemoglobin (mg/dl) (7.91-13.63). Pulse oximetry (SPO2) and capnography (ETCO2) readings were taken concurrently. There was no statistically significant relationship between SPO2 and SaO2 with a mean difference between SPO2 and SaO2 of 8.22 per cent. There was a statistically significant relationship between ETCO2 vs PaCO2, but a wide range of ETCO2 values were observed for a given PaCO2. The mean difference between these was 16.16 mm Hg. The study has provided reference intervals for arterial blood gas analysis in rabbits and demonstrated that capnography and pulse oximetry readings should not be relied upon in conscious rabbits as a guide to ventilation and oxygenation.
Publisher: Oxford University Press (OUP)
Date: 30-04-2013
DOI: 10.1093/GJI/GGT135
Publisher: American Geophysical Union (AGU)
Date: 10-2018
DOI: 10.1029/2018GC007730
Publisher: Elsevier BV
Date: 08-2017
Publisher: American Geophysical Union (AGU)
Date: 07-2019
DOI: 10.1029/2019GC008227
Abstract: Three parameters: temperature, hydrogen content, and the presence of partial melt, are the dominant controls on the rheology of the convecting upper mantle. As such, they determine the dynamics that control plate tectonics and continental evolution. Since hydrogen depresses the peridotite solidus temperature, these parameters are strongly linked petrologically. We have developed a genetic algorithm code to statistically assess the likelihood that a section of upper mantle contains partial melt. This code uses magnetotelluric observations and petrological constraints on composition and solidus temperatures and allows for uncertainties in the geotherm and the electrical conductivity structure. We have applied this code to the convecting upper mantle beneath (1) a stable continent (the Superior Craton) (2) a hot spot (Tristan da Cunha) (3) stable, old oceanic lithosphere (the northwest Pacific Ocean) and (4) young oceanic lithosphere (adjacent to the East Pacific Rise). Results show that the volume of melt in the convecting upper mantle is heterogeneous. The highest melt proportions are beneath the hot spot while little to no melt is required in the other regions. All regions show low water contents (generally wt ppm in olivine) in the shallow convecting upper mantle, making it unlikely that water causes a large or sharp viscosity contrast between the lithosphere and the convecting mantle. Results differ significantly for different experimental olivine hydrogen conductivity models, highlighting the importance of reconciling these experimental constraints.
Publisher: Oxford University Press (OUP)
Date: 22-08-2020
DOI: 10.1093/GJI/GGAA398
Abstract: We determine crustal shear wave velocity structure and crustal thickness at recently deployed seismic stations across West Antarctica, using a joint inversion of receiver functions and fundamental mode Rayleigh wave phase velocity dispersion. The stations are from both the UK Antarctic Network (UKANET) and Polar Earth Observing Network/Antarctic Network (POLENET/ANET). The former include, for the first time, four stations along the spine of the Antarctic Peninsula, three in the Ellsworth Land and five stations in the vicinity of the Pine Island Rift. Within the West Antarctic Rift System (WARS) we model a crustal thickness range of 18–28 km, and show that the thinnest crust (∼18 km) is in the vicinity of the Byrd Subglacial Basin and Bentley Subglacial Trench. In these regions we also find the highest ratio of fast (Vs = 4.0–4.3 km s–1, likely mafic) lower crust to felsic/intermediate upper crust. The thickest mafic lower crust we model is in Ellsworth Land, a critical area for constraining the eastern limits of the WARS. Although we find thinner crust in this region (∼30 km) than in the neighbouring Antarctic Peninsula and Haag-Ellsworth Whitmore block (HEW), the Ellsworth Land crust has not undergone as much extension as the central WARS. This suggests that the WARS does not link with the Weddell Sea Rift System through Ellsworth Land, and instead has progressed during its formation towards the Bellingshausen and Amundsen Sea Embayments. We also find that the thin WARS crust extends towards the Pine Island Rift, suggesting that the boundary between the WARS and the Thurston Island block lies in this region, ∼200 km north of its previously accepted position. The thickest crust (38–40 km) we model in this study is in the Ellsworth Mountain section of the HEW block. We find thinner crust (30–33 km) in the Whitmore Mountains and Haag Nunatak sectors of the HEW, consistent with the composite nature of the block. In the Antarctic Peninsula we find a crustal thickness range of 30–38 km and a likely dominantly felsic/intermediate crustal composition. By forward modelling high frequency receiver functions we also assess if any thick, low velocity subglacial sediment accumulations are present, and find a 0.1–0.8-km-thick layer at 10 stations within the WARS, Thurston Island and Ellsworth Land. We suggest that these units of subglacial sediment could provide a source region for the soft basal till layers found beneath numerous outlet glaciers, and may act to accelerate ice flow.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
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