45,370 research outputs found
Late Holocene mud sedimentation and diagenesis in the Firth of Thames: Bentonites in the making
No full textLate Holocene mud sedimentation in the southern Firth of Thames has been described from analysis of a number of shallow marine sediment cores. Three distinct lithofacies are distinguished on the basis of sediment texture and mineralogy. A laterally extensive greenish grey mud, typically bioturbated and massive, with sporadic uncorrelatable interbedded shell layers is termed the Firth of Thames mud facies. Nearer shore sediments are usually coarser and are subdivided into two facies: a siliciclastic sand facies (river mouth sand facies) comprising more prominent interbeds of sand in mud and associated with sedimentation at the mouth of the Waihou River; and a mixed terrigenous-carbonate gravel facies (delta fan gravel facies) associated with deposition on small delta fans adjacent to streams draining the Coromandel Range. The areal distribution of all three facies over the late Holocene has been controlled largely by northward progradation of the coastal Hauraki Lowland associated with the rapid sediment infilling of the Firth of Thames since sea level reached its present height 6500 y B.P. From seismic evidence the Holocene muds are up to 10m thick. The cores in this study penetrated only to 5.5m sub-bottom depth and yielded an oldest radiocarbon age of 5000 y B.P. The age data indicate an average rate of offshore vertical sediment accumulation of 1.5 mm/y.
Up to 15 km of progradation of the southern shoreline of the coastal Hauraki Lowland has occurred over the late Holocene at an average rate of up to 2.5 m/y, notably from 3500 y B.P to 1200 y B.P. Progradation is evidenced by the occurrence of coarsening-upward sequences in nearer shore cores of the Firth of Thames, as well as their changing faunal composition, particularly the upward increase in abundance of the foraminifer Ammonia beccarri, a good indicator of brackish water conditions, which suggests a gradual seaward encroachment of the freshwater influence of the Waihou River over the late Holocene. Basal muds which are similar in composition to marine sediments of the Firth of Thames are overlain by peat dated at 6025 y B.P in a peat core from Kopouatai Peat Bog, and suggest that marine conditions existed in this inland region of the Hauraki Depression prior to 6025 y B.P.
Muds range from silty clays to clayey silts and consist principally of volcanic glass, smectite and halloysite, with smaller amounts of other volcanic-derived siliciclasts and allophane and illite, as well as skeletal carbonate (mainly aragonite) and organic matter. A contemporaneous decrease in the abundance of volcanic glass (55-15 wt % down-core) and an increase in smectite concentration (8-45 wt % down-core) occurs with sub-bottom depth. Specific mineralogical analyses (XRD and IR) and evidence from scanning electron microscopy suggest the smectite is montmorillonitic in composition and authigenic in nature. Moreover, the absence of smectite in the bottom sediments of rivers draining the Hauraki Lowland precludes a detrital origin.
The diagenetic transformation of volcanic glass to smectite in sediments of the Firth of Thames is described by a sequential kinetic model which involves a parabolic dissolution coupled with a first order precipitation of smectite via the formation of an intermediate hydrated glass phase. The rate constant calculated from the sequential kinetic model is 3.35 x 10⁻⁴y⁻¹. The half-life of the glass is 1475 y, implying rapid early diagenetic alteration of volcanic glass to smectite to form late Holocene bentonitic deposits. Thermodynamic stability considerations imply that the first order precipitaion of smectite may be favoured by conditions of pH and Na⁺ activity typical of interstitial fluids having sea water salinity under mildly anoxic conditions
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Killer Whale (Orcinus orca) Occurrence in the Moray Firth, Northeast Scotland: Incidental Sightings,Behavioural Observations, and Photo-Identification
No full textThe article reports on the killer whale, known as Orcinus orca and its occurrence in the Moray Firth, Northeast Scotland. Topics discussed include the incidental sightings of this species, its behavioural observations, and photo-identification. Also being discussed are the white-beaked dolphins called Lagenorhynchus albirostris, and annual pupping season of the common seal called Phoca vitulina
The late holocene evolution of coastal wetlands in Argyll, Western Scotland
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A detailed geochronological and geochemical study has been undertaken on selected sediment cores from four lowland coastal marsh environments in Argyll, Western Scotland. This region of northern Britain has experienced differential crustal uplift and relative sea-level changes throughout the Holocene in response to glacio-isostatic adjustment. The complex interplay between land movements and relative sea-level continues to influence the morphological development of the Scottish coast. The study of lowland inter-tidal sedimentary environments from this region provides an opportunity to investigate the linkages between current estimated crustal movements, regional relative sea-level rise and the evolution of contemporary coastal saltmarshes derived from the record of historical sedimentation. The four sites are located across a ca. 70 km transect extending from the head of Loch Scridain (western Isle of Mull), across the Firth of Lorne to the head of Loch Etive, (mainland Argyll).
Vertical activity distributions of the natural radionuclide 21OPb and anthropogenic isotopes (137Cs and 243Am) have been measured and are used to assess the depositional history of marsh sediment accumulation recorded in the four marsh cores. Down-core activity profiles of radionuclides are only reliable as a means of modelling recent marsh evolution provided no early-diagenetic (redox) reactions have compromised the historical depositional record within the marsh sediments. Solid-phase major and trace element down-core geochemical distributions provide a means of assessing the extent to which post-depositional (redox) reactions may have influenced the reliability of the radiometric dating methods. Marsh sediment geochemistry also serves as a useful proxy for identifying compositional variability over the period of marsh development investigated.
Dating of the Argyll saltmarsh cores indicates that over the period corresponding to mature marsh conditions rates of sedimentation vary significantly across the study area. At Loch Scridain an average rate of 1.1 mm yr-1 corresponding to an historical period of ca. 130
years is recorded. Comparison with estimated rates of regional sea-level rise suggest an established asymptotic relationship between marsh accretion and coastal forcing, implying historical crustal stability at this site.
At sites within the Firth of Lome (Loch Don and Loch Creran) average rates of 2.5 and 3.3 mm yr-1 are recorded for the ca. 70 year period to 1995 with a figure of 2.2 mm yr-1 recorded in the marsh core from the head of Loch Etive. These values are well in excess of estimated relative sea-level rise during the twentieth century suggesting that these marshes may not yet have reached full equilibrium with sea-level. Microfossil analysis of the Loch Etive core helps to identify a more complex depositional history with an underlying trend of marine transgression for the ca. 110 year period of marsh development recorded in these sediments.
Over the most recent period of marsh development (ca. 5 years) a significant increase in the rate of marsh sedimentation at all sites is recorded. This signifies the response of these marshes to a very recent increase in the rate of relative sea-level rise across the region. Comparison with available storm frequency data indicates that the evolution of these marsh environments have not been subject to the influence of significant storm activity over the last in the late Twetieth century. The findings suggest that the more clastic sedimentary composition of the Argyll marshes results in these inter-tidal areas being extremely sensitive to changes in coastal forcing (sea-level rise). The implications of recent relative sea-level rise, current vertical crustal movements and future coastal management are discussed
Enriching Britain: Culture, Creativity and Growth
No full textUn report sul valore della cultura a livello istituzionale in Gran Bretagna, che risulta da una commissione di ricerca e studi, realizzati da professionisti e studiosi. Contiene una serie di raccomandazioni di politica culturale e finanziamento
Surface feeding specialisations recorded during individual focal follows (<i>n</i> = 238) of minke whales in the Moray Firth between 2001 and 2022.
No full textSurface feeding specialisations recorded during individual focal follows (n = 238) of minke whales in the Moray Firth between 2001 and 2022.</p
The east coast of Scotland bottlenose dolphin population : improving understanding of ecology outside the Moray Firth SAC
No full textDissipative solitons in pattern-forming nonlinear optical systems : cavity solitons and feedback solitons
No full textMany dissipative optical systems support patterns. Dissipative solitons are generally found where a pattern coexists with a stable unpatterned state. We consider such phenomena in driven optical cavities containing a nonlinear medium (cavity solitons) and rather similar phenomena (feedback solitons) where a driven nonlinear optical medium is in front of a single feedback mirror. The history, theory, experimental status, and potential application of such solitons is reviewed
Population ecology of bottlenose dolphins (Tursiops truncatus) off the east coast of Scotland
No full textThe population of bottlenose dolphins off the east coast of Scotland has been studied since the late 1980s, initially focused on the inner Moray Firth, where a Special Area of Conservation (SAC) was designated under the EU Habitats Directive. The population has since expanded its distributional range and currently ranges from the Moray Firth to the Firth of Forth. The main aims of this thesis were: (1) to estimate population parameters for this population using a 25 year individual recognition dataset, and (2) to increase knowledge of the distribution and abundance of dolphins in areas outside the SAC, especially to investigate areas of high use in St Andrews Bay. Apparent survival rate for adults and sub–adult dolphins was estimated at 0.946 (SE=0.005) accounting for temporary emigration caused by the population’s range expansion. Sex-specific survival was estimated for males (0.951, SE=0.013) and females (0.956, SE=0.011) using multistate models to minimize bias caused by individuals of unknown sex. Using a newly developed approach, fecundity rate was estimated at 0.222 (95% CI=0.218-0.253) from an expected mean inter-birth interval of 4.49 yrs (95% CI=3.94-4.93). Total population size was estimated as ~200 individuals, after accounting for temporary emigration and for heterogeneity in capture probabilities. In St Andrews Bay, an area used regularly in summer by approximately half the estimated population, habitat use modelling identified the entrance to the Firth of Tay and waters around Montrose as high use areas for dolphins, whose presence was influenced by tidal current speed and direction. The results suggest that the conservation and management plan for this small and isolated population of bottlenose dolphins should be reviewed to adapt it to current knowledge, especially regarding the uncertainty around the potential impacts of offshore renewable energy developments off the east coast of Scotland
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