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1.
Lance B. Morrissey Philippe Janvier Simon J. Braddy John P. Bennett Susan B. Marriott Peter R. Tarrant 《Geology Today》2006,22(2):66-67
Armoured jawless fish, or 'ostracoderms', lived 450–360 million years ago, and display unusual morphologies, unlike any modern fish group. Since they left no living descendants, their mode of swimming has, until recently, remained speculative, although this is a crucial question as the first true pectoral fins evolved within the 'ostracoderms'. The discovery of the oldest-known fish trails, from the Early Devonian (400 million year old) 'Lower Old Red Sandstone' of south-east Wales offers new insights into the swimming behaviour of these early fish, notably the osteostracan 'ostracoderms' (or cephalaspids), whose horseshoe-shaped head and paddle-shaped pectoral fins have remained a functional riddle. 相似文献
2.
Significance of post‐peak metamorphic reaction microstructures in the ultrahigh temperature Eastern Ghats Province,India 
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下载免费PDF全文 David E. Kelsey Laura J. Morrissey Martin Hand Chris Clark Renee Tamblyn Adrian A. Gaehl Sarah Marshall 《Journal of Metamorphic Geology》2017,35(9):1081-1109
Ultrahigh temperature (UHT) granulites in the Eastern Ghats Province (EGP) have a complex P–T–t history. We review the P–T histories of UHT metamorphism in the EGP and use that as a framework for investigating the P–T–t history of Mg–Al‐rich granulites from Anakapalle, with the express purpose of trying to reconcile the down‐pressure‐dominated P–T path with other UHT localities in the EGP. Mafic granulite that is host to Mg–Al‐rich metasedimentary granulites at Anakapalle has a protolith age of c. 1,580 Ma. Mg–Al‐rich metasedimentary granulites within the mafic granulite at Anakapalle were metamorphosed at UHT conditions during tectonism at 960–875 Ma, meaning that the UHT metamorphism was not the result of contact metamorphism from emplacement of the host mafic rock. Reworking occurred during the Pan‐African (c. 600–500 Ma) event, and is interpreted to have produced hydrous assemblages that overprint the post‐peak high‐T retrograde assemblages. In contrast to rocks elsewhere in the EGP that developed post‐peak cordierite, the metasedimentary granulites at Anakapalle developed post‐peak, generation ‘2’ reaction products that are cordierite‐absent and nominally anhydrous. Therefore, rocks at Anakapalle offer the unique opportunity to quantify the pressure drop that occurred during so‐called M2 that affected the EGP. We argue that M2 is either a continuation of M1 and that the overall P–T path shape is a complex counter‐clockwise loop, or that M1 is an up‐temperature counter‐clockwise deviation superimposed on the M2 path. Therefore, rather than the rocks at Anakapalle having a metamorphic history that is apparently anomalous from the rest of the EGP, we interpret that other previously studied localities in the EGP record a different part of the same P–T path history as Anakapalle, but do not preserve a significant record of pressure decrease. This is due either to the inability of refractory rocks to extensively react to produce a rich mineralogical record of pressure decrease, or because the earlier high‐P part of the rocks history was erased by the M1 loop. Irrespective of the specific scenario, models for the tectonic evolution of the EGP must take the substantial pressure decrease during M2 into account, as it is probable the P–T record at Anakapalle is a reflection of tectonics affecting the entire province. 相似文献
3.
New Zealand fur seals in the Kaikoura region breed near a town with expanding tourist and fishing industries and commonly come ashore entangled in nets and plastic debris. However, the rate at which entanglement occurs was previously unknown. A decade of Department of Conservation seal callout data was analysed to determine the level of entanglement in the region and the most common debris type. Monitoring of adult female fur seals released from entanglement provided information on the potential for serious wounds to heal and survivorship of released individuals. Entanglement rates of pinnipeds in Kaikoura are some of the highest reported world-wide (average range: 0.6-2.8%) with green trawl net (42%), and plastic strapping tape (31%) together contributing the most to debris types. Nearly half of the reported entangled seals are successfully released (43%) and post-release monitoring shows that with appropriate intervention the chance of an individual surviving even with a significant entanglement wound is high. Our study demonstrates that while entanglement in the region is high, a successful intervention protocol may help reduce the potential for entanglement-related mortality in the region. 相似文献
4.
Karyn Morrissey Graham Clarke Dimitris Ballas Stephen Hynes Cathal O'Donoghue 《Area》2008,40(3):354-364
This paper analyses the effect accessibility has on General Practitioner (GP) utilisation rates at the sub-national level for Ireland. Specifically, the aim of this paper is to estimate whether there is an urban–rural differential in GP utilisation rates. We do this by simulating micro-level healthcare data. Using this synthetic data, simple logit models are employed to estimate the likelihood that individuals in different jurisdictions will attend a GP surgery. These individual logit estimates are then inputted into a spatial interaction model to highlight areas with low GP accessibility given their health status. The policy implications of these results are discussed in relation to both the healthcare literature and current Irish healthcare policy. 相似文献
5.
Phase equilibria modelling constraints on P–T conditions during fluid catalysed conversion of granulite to eclogite in the Bergen Arcs,Norway 下载免费PDF全文
下载免费PDF全文 K. Bhowany M. Hand C. Clark D. E. Kelsey S. M. Reddy M. A. Pearce N. M. Tucker L. J. Morrissey 《Journal of Metamorphic Geology》2018,36(3):315-342
Exhumed eclogitic crust is rare and exposures that preserve both protoliths and altered domains are limited around the world. Nominally anhydrous Neoproterozoic anorthositic granulites exposed on the island of Holsnøy, in the Bergen Arcs in western Norway, preserve different stages of progressive prograde deformation, together with the corresponding fluid‐assisted metamorphism, which record the conversion to eclogite during the Ordovician–Silurian Caledonian Orogeny. Four stages of deformation can be identified: (1) brittle deformation resulting in the formation of fractures and the generation of pseudotachylites in the granulite; (2) development of mesoscale shear zones associated with increased fluid–rock interaction; (3) the complete large‐scale replacement of granulite by hydrous eclogite with blocks of granulite sitting in an eclogitic “matrix”; and (4) the break‐up of completely eclogitized granulite by continued fluid influx, resulting in the formation of coarse‐grained phengite‐dominated mineral assemblages. P–T constraints derived from phase equilibria forward modelling of mineral assemblages of the early and later stages of the conversion to eclogite document burial and partial exhumation path with peak metamorphic conditions of ~21–22 kbar and 670–690°C. The P–T models, in combination with existing T–t constraints, imply that the Lindås Nappe underwent extremely rapid retrogressive pressure change. Fluid infiltration began on the prograde burial path and continued throughout the recorded P–T evolution, implying a fluid source that underwent progressive dehydration during subduction of the granulites. However, in places limited fluid availability on the prograde path resulted in assemblages largely consuming the available fluid, essentially freezing in snapshots of the prograde evolution. These were carried metastably deeper into the mantle with strain and metamorphic recrystallization partitioned into areas where ongoing fluid infiltration was concentrated. 相似文献
6.
Efforts to measure the rate of nitrogen recycling in natural waters have depended on estimates of ammonium production using the 15N isotope dilution method. This technique requires the removal of dissolved ammonium from the water sample for analysis of the 15N content. Steam distillation or micro-diffusion methods have been most commonly used, but these techniques are labor intensive and time consuming. We have attempted to simplify the measurement of the planktonic regeneration of ammonium by presenting a mercury precipitation technique which is simple, practical, and easily used at sea. 相似文献
7.
Summary An algorithm for estimating rainfall (based upon scattering of upwelling radiation at 85 GHz) using the Special Sensor Microwave Imager (SSM/I) 85 GHz sensor data has recently been developed at the National Oceanographic and Atmospheric Administration's Office of Research and Applications (NOAA ORA). Spatial and temporal variability in the differences between simple areal-averaged rainfall estimates from a raingage and satellite-derived estimates are examined. These initial comparisons provide insight into the nature of the differences; however, due to substantial amounts of spatial sampling error in the raingage spatial averages, this approach is ineffective at identifying statistically significant differences.Thus, rainfall estimates for this algorithm are examined over the tropical Pacific using a statistical technique, called the noncontiguous raingage method (NCR), which minimizes spatial sampling error so that the statistical significance of relationships may be determined. The results indicate that, adjusted with calibration coefficients, the ORA algorithm could produce unbiased estimates of areal rainfall for the tropical Pacific region examined in this study.With 8 Figures 相似文献
8.
Cytochrome P-450 isozymes in salmonids determined with antibodies to purified forms of P-450 from rainbow trout 总被引：1，自引：0，他引：1
D.E. Williams R.C. Bender M.T. Morrissey D.P. Selivonchick D.R. Buhler 《Marine environmental research》1984,14(1-4)
Purification of cytochromes P-450 from liver microsomes of β-naphthoflavone (BNF)-fed rainbow trout yielded three apparently homogeneous forms. The major form (LM4b)* appears to be a P-448 type of cytochrome. A minor form (LM4a), having properties very similar to LM4b, was also obtained. In addition, a P-450 form (LM2) was isolated, with properties quite different from LM4a or LM4b, including a high rate of aflatoxin B1 (AFB1) metabolism (Williams & Buhler, 1983c). Antibodies to all three forms were obtained from rabbits. The IgGs prepared against LM4a and LM4b both cross-reacted (forming lines of identity) equally well with both antigens on Ouchterlony plates. Rat P-448 cross-reacted (without lines of identity) with both LM4a- and LM4b-IgG. LM4b-IgG was much more effective than LM4a-IgG for inhibition of LM4a or LM4b reconstituted benzo[a]pyrene (BP) hydroxylase, suggesting that these two antibodies recognize different antigenic sites. The LM2-IgG did not cross-react with any of the other rat or trout cytochromes P-450 examined. Levels of LM2 and LM4b in microsomes from untreated, polychlorinated biphenyl (PCB), phenobarbital (PB) or BNF-treated trout were estimated with an immunological technique involving electrophoresis on SDS-PAGE, followed by transfer to nitrocellulose and staining with either LM 2 - or LM4b -IgG. The ratio of
in microsomes from PCB- or BNF-treated rainbow trout was much higher than 1, whereas the reverse was true with microsomes from untreated rainbow trout. These results are consistent with previous observations (Vodicnik et al., 1982) that pretreatment with BNF induced the synthesis of a P-448 type cyytochrome, presumably responsible for the great increase in the metabolism and activation of BP seen in these fish. Conversely, pretreatment with PB did not affect the levels of either LM2 or LM4b. This specific immunological technique should make it possible to assay the levels of these P-450 and P-448 isozymes in various strains of rainbow trout and other species of fish. In addition, the effect of age, sex, diet and exposure to P-450 and P-448 inducers could be examined and, perhaps, utilized to predict the relative risk of certain populations to pollutants activated by these different isozymes. 相似文献
9.
A curious case of agreement between conventional thermobarometry and phase equilibria modelling in granulites: New constraints on P–T estimates in the Antarctica segment of the Musgrave–Albany–Fraser–Wilkes Orogen 下载免费PDF全文
下载免费PDF全文 The Windmill Islands region in Wilkes Land, east Antarctica, preserves granulite facies metamorphic mineral assemblages that yield seemingly comparable P–T estimates from conventional thermobarometry and mineral equilibria modelling. This is uncommon in granulite facies terranes, where conventional thermobarometry and phase equilibria modelling generally produce conflicting P–T estimates because peak mineral compositions tend to be modified by retrograde diffusion processes. In situ U–Pb monazite geochronology and calculated metamorphic phase diagrams show that the Windmill Islands experienced two phases of high thermal gradient metamorphism during the Mesoproterozoic. The first phase of metamorphism is recorded by monazite ages in two widely separated samples and occurred at c. 1,305 Ma. This event was regional in extent, involved crustally derived magmatism and reached conditions of ~3.2–5 kbar and 690–770°C corresponding to very high thermal gradients of >150°C/kbar. The elevated thermal regime is interpreted to reflect a period of extension or increased extension in a back‐arc setting that existed prior to c. 1,330 Ma. The first metamorphic event was overprinted by granulite facies metamorphism at c. 1,180 Ma that was coeval with the intrusion of charnockite. This event involved peak temperatures of ~840–850°C and pressures of ~4–5 kbar. A phase of granitic magmatism at c. 1,250–1,210 Ma, prior to the intrusion of the charnockite, is interpreted to reflect a phase of compression within an overall back‐arc setting. Existing conventional thermobarometry suggests conditions of ~4 kbar and 750°C for M1 and 4–7 kbar and 750–900°C for M2. The apparent similarities between the phase equilibria modelling and existing conventional thermobarometry may suggest either that the terrane cooled relatively quickly, or that the P–T ranges obtained from conventional thermobarometry are sufficiently imprecise that they cover the range of P–T conditions obtained in this study. However, without phase equilibria modelling, the veracity of existing conventional P–T estimates cannot be evaluated. The calculated phase diagrams from this study allow the direct comparison of P–T conditions in the Windmill Islands with phase equilibria models from other regions in the Musgrave–Albany–Fraser–Wilkes Orogen. This shows that the metamorphic evolution of the Wilkes Land region is very similar to that of the eastern Albany–Fraser Orogen and Musgrave Province in Australia, and further demonstrates the remarkable consistency in the timing of metamorphism and the thermal gradients along the ~5,000 km strike length of this system. 相似文献
10.
In order to assess the potential role of organic sulfur compounds in hydrothermal systems, we use recent advances in theoretical geochemistry to estimate the standard partial molal thermodynamic properties and parameters for the revised Helgeson-Kirkham-Flowers equation of state for aqueous straight-chain alkyl thiols. Thermodynamic properties are used to determine the potential for thiol formation in both modern and Archean hydrothermal systems. We conclude that organic sulfur compounds may hold the key to the organic chemistry that led to the origin of life in hydrothermal settings. These results may also explain the presence of sulfur in a number of biomolecules present in ancient thermophilic microorganisms. 相似文献