The Cryogenian arc formation and successive high-K calc–alkaline plutons of Socotra Island (Yemen)     

Y. Denèle  S. Leroy  E. Pelleter  R. Pik  J-Y. Talbot  K. Khanbari 《Arabian Journal of Geosciences》2011,5(5):903-924

The Socotra Island belongs to the southern rifted margin of the Gulf of Aden and occupied in Neoproterozoic times a key position to constrain the age and the nature of the largely hidden Neoproterozoic rocks of the Arabian plate. Our integrated field, petrographic, geochemical and geochronological study in the Neoproterozoic rocks recognises three main successive events: (a) high-temperature ductile deformation and metamorphism forming probably in a compressive or transpressive regime; (b) mafic to intermediate intrusions as vertical sheets, kilometre-scale gabbro laccoliths, mafic dike swarm and lavas which present mainly a depleted arc signature with some evidences of evolution from an enriched-arc signature; (c) felsic intrusions mainly composed of highly potassic calc–alkaline and pinkish granites dated between 840 and 780 Ma. Relationships between the various petrographic types and U–Pb data suggest that these events occurred during a relatively short time span (80 Ma at max). Earlier high-temperature–low-pressure metamorphism stage as well as geochemical signature of mafic rocks show that development of Cryogenian formations of Socotra were controlled successively by an Andean-arc and a back-arc setting. These features cannot be easily reconciled with those of the Arabian–Nubian shield to the west of Socotra and of the Mozambique Belt to the south. We propose that the Socotra basement was developed at an active margin close to the India block in Cryogenian times.  相似文献   

Socioeconomic Vulnerabilities and Housing Reconstruction in Puerto Rico After Hurricanes Irma and Maria     

Talbot  Jessica  Poleacovschi  Cristina  Hamideh  Sara 《Natural Hazards》2022,110(3):2113-2140

Natural Hazards - Hurricanes Irma and Maria caused widespread destruction in Puerto Rico in 2017. In the absence of government recovery support and denial of assistance based on ownership, many...  相似文献   

A framework to estimate sediment loads using distributions with covariates: Beaurivage River watershed (Québec,Canada)     

A. Mailhot  A. N. Rousseau  G. Talbot  P. Gagnon  R. Quilbé 《水文研究》2008,22(26):4971-4985

A framework to estimate sediment loads based on the statistical distribution of sediment concentrations and various functional forms relating distribution characteristics (e.g. mean and variance) to covariates is developed. The covariates are used as surrogates to represent the main processes involved in sediment generation and transport. Statistical models of increasing complexity are built and compared to assess their relative performance using available sediment concentration and covariate data. Application to the Beaurivage River watershed (Québec, Canada) is conducted using data for the 1989–2004 period. The covariates considered in this application are streamflow and calendar day. A comparison of different statistical models shows that, in this case, the log‐normal distribution with a mean value depending on streamflow (power law with an additive term) and calendar day (sinusoidal), a constant coefficient of variation for streamflow dependence and a constant standard deviation for calendar day dependence provide the best result. Model parameters are estimated using the maximum likelihood estimation technique. The selected model is then used to estimate the distribution of annual sediment loads for the Beaurivage River watershed for a selected period. A bootstrap parametric method is implemented to account for uncertainties in parameter values and to build the distributions of annual loads. Comparison of model results with estimates obtained using the empirical ratio estimator shows that the latter were rarely within the 0·1–0·9 quantile interval of the distributions obtained with the proposed approach. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Book reviews     

Alan N. Baker  Charles Mitchell  Talbot Murray  Warwick F. Vincent 《新西兰海洋与淡水研究杂志》2013,47(4):625-628

Behavioural biology of killer whales. Editors: C. Kirkevold and J. S. Lockard. Zoo Biology Monographs, Volume 1. Alan Liss Inc., New York, 1986. 457 p. ISBN 0–8451–3100–1. Price: US$79.50.

Aquaculture of Cyprinids. Editors: R. Billard and J. Marcel. Institut National de la Recherche Agronomique, 1986. 504 p. Price FF150.00. Available from INRA Publications, Route de St Cyr, 78000 Versailles, France.

The Peruvian anchoveta and its upwelling ecosystem: three decades of change. Editors: D. Pauly and I. Tsukayama. Institute) del Mar del Peru (IMARPE); Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ); International Center for Living Aquatic Resources Management (ICLARM) 1987.351 p. ISBN 971–1022–34–6, ISSN 0115–4389. Price US$17.50 surface; US$36 airmail. Available from ICLARM, MCP.O. 1501, Makati, Metro Manilla, Philippines.

The freshwater planktonic blue‐greens (Cyanophyta/Cyanobacteria) of New Zealand: a taxonomic guide. By M. K. Etheredge and R. D. Pridmore. Published for the National Water and Soil Conservation Authority, 1987. 122 p, including 93 figures. ISSN0110–4705. Price $38.50. Available from DSIR Publishing, P.O. Box 9741, Wellington, New Zealand.  相似文献   

Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes     

Josef ?urech  Mikko Kaasalainen  David Dunham  Josef Hanuš  John Talbot  Brian D. Warner  Adrián Galád 《Icarus》2011,214(2):652-670

Asteroid sizes can be directly measured by observing occultations of stars by asteroids. When there are enough observations across the path of the shadow, the asteroid’s projected silhouette can be reconstructed. Asteroid shape models derived from photometry by the lightcurve inversion method enable us to predict the orientation of an asteroid for the time of occultation. By scaling the shape model to fit the occultation chords, we can determine the asteroid size with a relative accuracy of typically ∼10%. We combine shape and spin state models of 44 asteroids (14 of them are new or updated models) with the available occultation data to derive asteroid effective diameters. In many cases, occultations allow us to reject one of two possible pole solutions that were derived from photometry. We show that by combining results obtained from lightcurve inversion with occultation timings, we can obtain unique physical models of asteroids.  相似文献   

Results from the adaptive optics coronagraph at the William Herschel Telescope     

S. J. Thompson  A. P. Doel  R. G. Bingham  A. Charalambous  R. M. Myers  N. Bissonauth  P. Clark  G. Talbot 《Monthly notices of the Royal Astronomical Society》2005,364(4):1203-1210

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Photochemistry in the Arctic Free Troposphere: Ozone Budget and Its Dependence on Nitrogen Oxides and the Production Rate of Free Radicals     

Craig Stroud  Sasha Madronich  Elliot Atlas  Christopher Cantrell  Alan Fried  Brian Wert  Brian Ridley  Fred Eisele  Lee Mauldin  Richard Shetter  Barry Lefer  Frank Flocke  Andy Weinheimer  Mike Coffey  Brian Heikes  Robert Talbot  Donald Blake 《Journal of Atmospheric Chemistry》2004,47(2):107-138

Local ozone production and loss rates for the arctic free troposphere (58–85° N, 1–6 km, February–May) during the TroposphericOzone Production about the Spring Equinox (TOPSE) campaign were calculated using a constrained photochemical box model. Estimates were made to assess the importance of local photochemical ozone production relative to transport in accounting for the springtime maximum in arctic free tropospheric ozone. Ozone production and loss rates from our diel steady-state box model constrained by median observations were first compared to two point box models, one run to instantaneous steady-state and the other run to diel steady-state. A consistent picture of local ozone photochemistry was derived by all three box models suggesting that differences between the approaches were not critical. Our model-derived ozone production rates increased by a factor of 28 in the 1–3 km layer and a factor of 7 in the 3–6 kmlayer between February and May. The arctic ozone budget required net import of ozone into the arctic free troposphere throughout the campaign; however, the transport term exceeded the photochemical production only in the lower free troposphere (1–3 km) between February and March. Gross ozone production rates were calculated to increase linearly with NO_x mixing ratiosup to 300 pptv in February and for NO_x mixing ratios up to 500 pptv in May. These NO_x limits are an order of magnitude higher thanmedian NO_x levels observed, illustrating the strong dependence ofgross ozone production rates on NO_x mixing ratios for the majority of theobservations. The threshold NO_x mixing ratio needed for netpositive ozone production was also calculated to increase from NO_x 10pptv in February to 25 pptv in May, suggesting that the NO_x levels needed to sustain net ozone production are lower in winter than spring. This lower NO_x threshold explains how wintertime photochemical ozone production can impact the build-up of ozone over winter and early spring. There is also an altitude dependence as the threshold NO_x neededto produce net ozone shifts to higher values at lower altitudes. This partly explains the calculation of net ozone destruction for the 1–3 km layerand net ozone production for the 3–6 km layer throughout the campaign.  相似文献   

The Late Pleistocene - Holocene palaeolimnology of Lake Victoria, East Africa, based upon elemental and isotopic analyses of sedimentary organic matter   总被引：1，自引：0，他引：1  

Michael R. Talbot  Tine Lærdal 《Journal of Paleolimnology》2000,23(2):141-164

Three piston cores from Lake Victoria (East Africa) have been analysed for organic carbon (TOC) and nitrogen (TN) content, stable isotopes (¹³C and ¹⁵N), and Hydrogen Index (HI). These data are combined with published biogenic silica and water content analyses to produce a detailed palaeolimnological history of the lake over the past ca. 17.5 ka. Late Pleistocene desiccation produced a lake-wide discontinuity marked by a vertisol. Sediments below the discontinuity are characterised by relatively low TOC and HI values, and high C/N, ¹³C and ¹⁵N, reflecting the combined influence of abundant terrestrial plant material and generally unfavourable conditions for organic matter preservation. A thin muddy interval with lower ¹³C and higher HI and water content indicates that dry conditions were interrupted by a humid period of a few hundred years duration when the lake was at least 35 m deep. The climate changed to significantly more humid conditions around 15.2 ka when the dry lake floor was rapidly flooded. Abundant macrophytic plant debris and high TOC and ¹³C values at the upper vertisol surface probably reflect a marginal swamp. ¹³C values decrease abruptly and HI begins to increase around 15 ka BP, marking a shift to deeper-water conditions and algal-dominated lake production. C/N values are relatively low during this period, suggesting a generally adequate supply of nitrogen, but increasing ¹⁵N values reflect intense utilisation of the lake's DIN reservoir, probably due to a dramatic rise in productivity as nutrients were released to the lake from the flooded land surface.An abrupt drop in ¹³C and ¹⁵N values around 13.8-13.6 ka reflects a period of deep mixing. Productivity increased due to more efficient nutrient recycling, and ¹³C values fell as ¹²C-rich CO₂ released by bacterial decomposition of the organic material was brought into the epilimnion. A weak drop in HI values suggests greater oxygen supply to the hypolimnion at this time. Better mixing was probably due to increased wind intensity and may mark the onset of the Younger Dryas in the region.After the period of deep mixing, the water column became more stable. TOC, C/N, ¹³C and HI values were at a maximum during the period between 10 and 4 ka, when the lake probably had a stratified water column with anoxic bottom waters. A gradual decrease in values over the last 4000 yrs suggest a change to a more seasonal climate, with periodic mixing of the water column. Rising sediment accumulation rates and a trend to more uniform surface water conditions over the last 2000 yrs are probably a result of increased anthropogenic impact on the lake and its catchment.Following a maximum at the time of the rapid lake-level rise during the terminal Pleistocene, ¹⁵N has remained relatively low and displays a gradual but consistent trend to lower values from the end of the Pleistocene to the present. TN values have risen during the same period. The lack of correlation between ¹³C and ¹⁵N, and the absence of any evidence for isotopic reservoir effects despite the rise in TN, suggests that the atmosphere, rather than the lake's dissolved nitrogen pool has been the principal source of nitrogen throughout the Holocene. The importance of atmospheric N fixation to Lake Victoria's nitrogen cycle thus predates by a very considerable margin any possible anthropogenic eutrophication of the lake.  相似文献   

Rip current charactersitics and their role in the exchange of water and surf diatoms between the surf zone and nearshore     

M. M. B. Talbot  G. C. Bate 《Estuarine, Coastal and Shelf Science》1987,25(6)

Photogrammetric measurements of dye dispersion in a high-energy surf zone provided semi-quantitative measurements of the pattern and flux of water exchange between the surf zone and nearshore. The intensity of current flow, the rip morphology and its position within the surf zone have important ecological implications for the surf zone and nearshore biota. A variety of water-movement patterns was found, ranging from currents which remained confined to the beach terrace to those which involved substantial exchange across the breaker line. In considering rips as exchange mechanisms, two rip types are recognized. Depending on the exchange of water across the breaker line, a rip may be classified as ‘exchange’ or ‘non-exchange’. The ecological significance of these current types is discussed and a classification scheme for rip currents is proposed. Offshore fluxes across the breaker line by rip currents ranged from negligible to 80 m³s⁻¹ rip⁻¹. The estimated maximum flux per running meter of the Sundays River Beach was calculated as 0·0.32m ³ s⁻¹. The half-residence period of surf-zone water ranged from as little as 22 min t0 5 days, averaging 3·6 h.A dichotomy of current patterns found between the water column and surface layers is used to explain the build up of a concentration gradient in cell numbers of the surf diatom Anaulus birostratus within the surf zone despite extensive flushing by surf circulation.  相似文献   

The structural geology of boulby (potash) mine, Cleveland, United Kingdom     

C.J. Talbot  C.P. Tully  P.J.E. Woods 《Tectonophysics》1982,85(3-4)

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