U–Pb geochronology and petrology of the late Paleozoic Gil Marquez pluton: magmatism in the Variscan suture zone,southern Iberia,during continental collision and the amalgamation of Pangea     

Evan R. Gladney  James A. Braid  J. Brendan Murphy  Cecilio Quesada  Christopher R. M. McFarlane 《International Journal of Earth Sciences》2014,103(5):1433-1451

The origin of plutonic complexes that stitch suture zones developed during collision is not well understood. In southern Iberia, the Pulo du Lobo suture zone (PDLZ) is intruded by the syn- to postcollisional Gil Marquez pluton (GMP), thought to be part of the Sierra Norte Batholith. U–Pb (LA-ICPMS, zircon) data on various phases of the GMP yield from oldest to youngest: (1) a 354.4 ± 7.6 Ma unfoliated gabbro; (2) a 345.6 ± 2.5 Ma foliated intermediate phase; (3) a 346.5 ± 5.4 Ma unfoliated porphyritic granite; (4) a 335.1 ± 2.8 Ma unfoliated biotite granite. This sequence is consistent with cross-cutting relationships observed in the field. The range in ages is consistent with interpretations that the GMP is part of the composite (ca. 350–308 Ma) SNB. Inherited ages preserved in the GMP intermediate and felsic phases indicate that its magmas traversed through South Portuguese Zone and PDLZ crust during emplacement. The ca. 345 Ma emplacement of the late kinematic foliated intermediate phase constrains the age of late-stage strike slip deformation within the PDLZ, and the lack of a foliation in the older gabbro indicates that is was not proximal to a shear zone neither at the time of emplacement, nor during its subsequent history. The unfoliated porphyritic granite and unfoliated biotite granite cut the foliation of the intermediate phase indicating emplacement during the waning stages of collision, while the ca. 335 Ma biotite granite intrudes the Santa Ira Flysch, thereby providing a tight constraint for the latest stage of deformation in the PDLZ.  相似文献   

Nitrogen loading to Pleasant Bay, Cape Cod: application of models and stable isotopes to detect incipient nutrient enrichment of estuaries   总被引：1，自引：0，他引：1  

Carmichael RH  Annett B  Valiela I 《Marine pollution bulletin》2004,48(1-2):137-143

To test and refine methods to detect nutrient enrichment and resulting eutrophication, we applied the Waquoit Bay nitrogen loading model (NLM) and Estuarine loading model (ELM) to estuaries of Pleasant Bay that receive increasing but low N loads (25-199 kg N ha(-1) yr(-1)) from land. Contributions of wastewater to these estuaries increased from 7% to 63% as N loads increased, and modeled estimates of dissolved inorganic nitrogen in the water were within approximately 27% of measured values. N isotopic signatures in suspended and benthic organic matter and in tissue of quahogs increased as wastewater contributions to N loads increased, with clams approximately 4 per thousand heavier than organic matter, indicating that even at these low N loads, N from land-derived sources moved detectably up the food web. These results extend the application of NLM and ELM to detect incipient levels of N enrichment and demonstrate that these models can be used in conjunction with isotope measurements as the basis for food web analyses in a system exposed to relatively lower N loads than previously studied.  相似文献   

Spectroscopic observations of the intermediate polar EX Hydrae in quiescence     

N. Mhlahlo  D. A. H. Buckley  V. S. Dhillon  S. B. Potter  B. Warner  P. A. Woudt 《Monthly notices of the Royal Astronomical Society》2007,378(1):211-220

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Mid-Holocene vertebrate bone Concentration-Lagerstätte on oceanic island Mauritius provides a window into the ecosystem of the dodo (Raphus cucullatus)     

Kenneth F. Rijsdijk  Julian P. Hume  Frans Bunnik  F.B. Vincent Florens  Claudia Baider  Beth Shapiro  Johannes van der Plicht  Anwar Janoo  Owen Griffiths  Lars W. van den Hoek Ostende  Holger Cremer  Tamara Vernimmen  Perry G.B. De Louw  Assenjee Bholah  Salem Saumtally  Nicolas Porch  James Haile  Mike Buckley  Matthew Collins  Edmund Gittenberger 《Quaternary Science Reviews》2009,28(1-2):14-24

Although the recent history of human colonisation and impact on Mauritius is well documented, virtually no records of the pre-human native ecosystem exist, making it difficult to assess the magnitude of the changes brought about by human settlement. Here, we describe a 4000-year-old fossil bed at Mare aux Songes (MAS) in south-eastern Mauritius that contains both macrofossils (vertebrate fauna, gastropods, insects and flora) and microfossils (diatoms, pollen, spores and phytoliths). With >250 bone fragments/m² and comprising 50% of all known extinct and extant vertebrate species (n_s = 44) of Mauritius, MAS may constitute the first Holocene vertebrate bone Concentration-Lagerstätte identified on an oceanic volcanic island. Fossil remains are dominated by extinct giant tortoises Cylindraspis spp. (63%), passerines (～10%), small bats (7.8%) and dodo Raphus cucullatus (7.1%). Twelve radiocarbon ages [four of them duplicates] from bones and other material suggest that accumulation of fossils took place within several centuries. An exceptional combination of abiotic conditions led to preservation of bones, bone collagen, plant tissue and microfossils. Although bone collagen is well preserved, DNA from dodo and other Mauritian vertebrates has proved difficult. Our analysis suggests that from ca 4000 years ago (4 ka), rising sea levels created a freshwater lake at MAS, generating an oasis in an otherwise dry environment which attracted a diverse vertebrate fauna. Subsequent aridification in the south-west Indian Ocean region may have increased carcass accumulation during droughts, contributing to the exceptionally high fossil concentration. The abundance of floral and faunal remains in this Lagerstätte offers a unique opportunity to reconstruct a pre-human ecosystem on an oceanic island, providing a key foundation for assessing the vulnerability of island ecosystems to human impact.  相似文献   

3-D seismic exploration data and the study of shallow marine geology     

Francis Buckley 《Geology Today》2007,23(1):18-23

In 2005, Geology Today carried an article (v.22, n.5) describing how 3D exploration seismic data are being used to map sub-surface structure and stratigraphy, in fine detail, over hundreds and even thousands of square kilometres of the sea bed. The article in question was concerned primarily with the various ways in which 3D seismic data are applied to the study of stratigraphy and basin analysis. However, the potential uses of 3D exploration data for investigating other kinds of geological phenomena are many and varied, and significant advances may be made in our understanding of the geological past using such data. The present article describes how 3D seismic data can be used to investigate aspects of the upper Tertiary and Quaternary geology of marine areas, drawing on examples from the Central North Sea and West Shetland Slope. These originally came to light in the course of conducting geo-hazard surveys on behalf of the hydrocarbons industry.  相似文献   

Optical studies of two Large Magellanic Cloud X-ray transients: RX J0544.1–7100 and RX J0520.5–6932     

M.J. Coe  I. Negueruela  D.A.H. Buckley  N.J. Haigh  S.G.T. Laycock 《Monthly notices of the Royal Astronomical Society》2001,324(3):623-627

We report observations that confirm the identities of the optical counterparts to the transient sources RX J0544.1–7100 and RX J0520.5–6932 . The counterparts are suggested to be B-type stars. Optical data from the observations carried out at ESO and SAAO, together with results from the OGLE data base, are presented. In addition, X-ray data from the RXTE All-Sky Monitor are investigated for long-term periodicities. A strong suggestion for a binary period of 24.4 d is seen in RX J0520.5–6932 from the OGLE data.  相似文献   

Modelling submillimetre spectra of the protostellar infall candidates NGC 1333–IRAS 2 and Serpens SMM4     

D. Ward-Thompson  H.D. Buckley 《Monthly notices of the Royal Astronomical Society》2001,327(3):955-983

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Reducing emissions from deforestation—The “combined incentives” mechanism and empirical simulations     

Bernardo Strassburg  R. Kerry Turner  Brendan Fisher  Roberto Schaeffer  Andrew Lovett 《Global Environmental Change》2009,19(2):265-278

Despite accounting for 17–25% of anthropogenic emissions, deforestation was not included in the Kyoto Protocol. The UN Convention on Climate Change is considering its inclusion in future agreements and asked its scientific board to study methodological and scientific issues related to positive incentives to reduce emissions from deforestation. Here we present an empirically derived mechanism that offers a mix of incentives to developing countries to reduce emissions from deforestation, conserve and possibly enhance their ecosystem's carbon stocks. We also use recent data to model its effects on the 20 most forested developing countries. Results show that at low CO₂ prices (～US$ 8/t CO₂) a successful mechanism could reduce more than 90% of global deforestation at an annual cost of US$ 30 billion.  相似文献   

Unraveling the sequence and structure of the protein osteocalcin from a 42 ka fossil horse     

Peggy H. Ostrom  Hasand Gandhi  Angela K. Walker  Joseph Leykam  Robert L. Kelly  Mike Buckley 《Geochimica et cosmochimica acta》2006,70(8):2034-2044

We report the first complete amino acid sequence and evidence of secondary structure for osteocalcin from a temperate fossil. The osteocalcin derives from a 42 ka equid bone excavated from Juniper Cave, Wyoming. Results were determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-MS) and Edman sequencing with independent confirmation of the sequence in two laboratories. The ancient sequence was compared to that of three modern taxa: horse (Equus caballus), zebra (Equus grevyi), and donkey (Equus asinus). Although there was no difference in sequence among modern taxa, MALDI-MS and Edman sequencing show that residues 48 and 49 of our modern horse are Thr, Ala rather than Pro, Val as previously reported (Carstanjen B., Wattiez, R., Armory, H., Lepage, O.M., Remy, B., 2002. Isolation and characterization of equine osteocalcin. Ann. Med. Vet.146(1), 31-38). MALDI-MS and Edman sequencing data indicate that the osteocalcin sequence of the 42 ka fossil is similar to that of modern horse. Previously inaccessible structural attributes for ancient osteocalcin were observed. Glu₃₉ rather than Gln₃₉ is consistent with deamidation, a process known to occur during fossilization and aging. Two post-translational modifications were documented: Hyp₉ and a disulfide bridge. The latter suggests at least partial retention of secondary structure. As has been done for ancient DNA research, we recommend standards for preparation and criteria for authenticating results of ancient protein sequencing.  相似文献   

Hornblende dehydration reactions during magma ascent at Soufrière Hills Volcano, Montserrat   总被引：1，自引：1，他引：0  

V. J. E. Buckley  R. S. J. Sparks  B. J. Wood 《Contributions to Mineralogy and Petrology》2006,151(2):121-140

Hornblende phenocrysts in recent andesites of the Soufrière Hills Volcano display reaction rims of microcrystalline plagioclase, pyroxene, Fe-oxides and interstitial glass, formed by decompression during magma ascent. Mass balance calculations give the following reactions with mineral proportions in agreement with modal abundances: These reactions require an open chemical system with exchange of selected components with surrounding melt. Volatiles, TiO₂ and alkalis are expelled and SiO₂ and FeO^T are consumed. Matrix glasses fall into two compositional groups. Glasses in pumice are relatively rich in CaO and poor in K₂O and Na₂O compared to glasses in dome samples. The former glasses formed by moderate amounts of groundmass crystallisation of plagioclase, associated with rapid magma ascent in explosive eruptions. The later glasses evolved in response to hornblende breakdown, groundmass crystallisation and mixing of melts from different levels during slow magma ascent and extended residence time in the dome. Interstitial glass compositions in reaction rims reflect the compositions of the surrounding matrix glasses, but show variable compositional differences mostly consistent with the proposed open-system reactions.  相似文献