Geochronological and petrological constraints from the evolution in the Saxon Granulite Massif,Germany, on the Variscan continental collision orogeny     

Jochen Rtzler  Martin J. Timmerman 《Journal of Metamorphic Geology》2021,39(1):3-38

Controversy over the plate tectonic affinity and evolution of the Saxon granulites in a two‐ or multi‐plate setting during inter‐ or intracontinental collision makes the Saxon Granulite Massif a key area for the understanding of the Palaeozoic Variscan orogeny. The massif is a large dome structure in which tectonic slivers of metapelite and metaophiolite units occur along a shear zone separating a diapir‐like body of high‐P granulite below from low‐P metasedimentary rocks above. Each of the upper structural units records a different metamorphic evolution until its assembly with the exhuming granulite body. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths during high‐P amphibolite facies metamorphism in the mid‐ to late‐Devonian and thermal overprinting by the exhuming hot granulite body in the early Carboniferous. A correlation of new Ar–Ar biotite ages with published P–T–t data for the granulites implies that exhumation and cooling of the granulite body occurred at average rates of ~8 mm/year and ~80°C/Ma, with a drop in exhumation rate from ~20 to ~2.5 mm/year and a slight rise in cooling rate between early and late stages of exhumation. A time lag of c. 2 Ma between cooling through the closure temperatures for argon diffusion in hornblende and biotite indicates a cooling rate of 90°C/Ma when all units had assembled into the massif. A two‐plate model of the Variscan orogeny in which the above evolution is related to a short‐lived intra‐Gondwana subduction zone conflicts with the oceanic affinity of the metaophiolites and the timescale of c. 50 Ma for the metamorphism. Alternative models focusing on the internal Variscan belt assume distinctly different material paths through the lower or upper crust for strikingly similar granulite massifs. An earlier proposed model of bilateral subduction below the internal Variscan belt may solve this problem.  相似文献   

The perceptions of local fishermen towards a hotel managed marine reserve in Vietnam     

Patrik Svensson  Lynda D. Rodwell  Martin J. Attrill 《Ocean & Coastal Management》2010,53(3):114-122

Marine Protected Areas (MPAs) often fail to meet ecological, social or economic objectives due to lack of effective management by government institutions. Partly in response to this failure, a number of marine reserves managed by the private sector, Hotel Managed Marine Reserves (HMMRs), have recently been established. In this study, we investigate changes to the social and economic conditions faced by local fishermen, following the establishment of two small reserves adjacent to a hotel in Vietnam, as well as their perceptions of the reserves' ability to produce spillover. The findings are used to gauge management performance and effectiveness of the HMMRs. Two surveys with different survey designs, targeting fishermen with different fishing techniques, produced conflicting results. Fishermen mainly dependent on beach seining mostly opposed the HMMRs and the prospect of more protected areas being established. Fishermen using other fishing techniques were generally in favor of the HMMRs, welcoming more protection and confirming spillover of fish, including large food fishes.  相似文献   

A systematic evaluation of the Zr-in-rutile thermometer in ultra-high temperature (UHT) rocks     

Jonas Pape  Klaus Mezger  Martin Robyr 《Contributions to Mineralogy and Petrology》2016,171(5):44

  相似文献   

Variability in bedform morphology and kinematics with transport stage          下载免费PDF全文

Jeremy G. Venditti  C.‐Y. Martin Lin  Moslem Kazemi 《Sedimentology》2016,63(4):1017-1040

Bedform geometry is widely recognized to be a function of transport stage. Bedform aspect ratio (height/length) increases with transport stage, reaches a maximum, then decreases as bedforms washout to a plane bed. Bedform migration rates are also linked to bedform geometry, in so far as smaller bedforms in coarser sediment tend to migrate faster than larger bedforms in finer sediment. However, how bedform morphology (height, length and shape) and kinematics (translation and deformation) change with transport stage and suspension have not been examined. A series of experiments is presented where initial flow depth and grain size were held constant and the transport stage was varied to produce bedload dominated, mixed‐load dominated and suspended‐load dominated conditions. The results show that the commonly observed pattern in bedform aspect ratio occurs because bedform height increases then decreases with transport stage, against a continuously increasing bedform length. Bedform size variability increased with transport stage, leading to less uniform bedform fields at higher transport stage. Total translation‐related and deformation‐related sediment fluxes all increased with transport stage. However, the relative contribution to the total flux changed. At the bedload dominated stage, translation‐related and deformation‐related flux contributed equally to the total flux. As the transport stage increased, the fraction of the total load contributed by translation increased and the fraction contributed by deformation declined because the bedforms got bigger and moved faster. At the suspended‐load dominated transport stage, the deformation flux increased and the translation flux decreased as a fraction of the total load, approaching one and zero, respectively, as bedforms washed out to a plane bed.  相似文献   

Back Analysis of Rock Mass Displacements Around a Deep Shaft Using Two- and Three-Dimensional Continuum Modeling     

Hossein Rafiei Renani  C. Derek Martin  Richard Hudson 《Rock Mechanics and Rock Engineering》2016,49(4):1313-1327

  相似文献   

Assessment of climate variations in temperature and precipitation extreme events over Iran   总被引：1，自引：0，他引：1  

M. Soltani  P. Laux  H. Kunstmann  K. Stan  M. M. Sohrabi  M. Molanejad  A. A. Sabziparvar  A. Ranjbar SaadatAbadi  F. Ranjbar  I. Rousta  P. Zawar-Reza  F. Khoshakhlagh  I. Soltanzadeh  C. A. Babu  G. H. Azizi  M. V. Martin 《Theoretical and Applied Climatology》2016,126(3-4):775-795

  相似文献   

Convective and stratiform precipitation characteristics in an ensemble of regional climate model simulations   总被引：1，自引：0，他引：1  

Jan Kyselý  Zuzana Rulfová  Aleš Farda  Martin Hanel 《Climate Dynamics》2016,46(1-2):227-243

We apply a recently proposed algorithm for disaggregating observed precipitation data into predominantly convective and stratiform, and evaluate biases in characteristics of parameterized convective (subgrid) and stratiform (large-scale) precipitation in an ensemble of 11 RCM simulations for recent climate in Central Europe. All RCMs have a resolution of 25 km and are driven by the ERA-40 reanalysis. We focus on mean annual cycle, proportion of convective precipitation, dependence on altitude, and extremes. The results show that characteristics of total precipitation are often better simulated than are those of convective and stratiform precipitation evaluated separately. While annual cycles of convective and stratiform precipitation are reproduced reasonably well in most RCMs, some of them consistently and substantially overestimate or underestimate the proportion of convective precipitation throughout the year. Intensity of convective precipitation is underestimated in all RCMs. Dependence on altitude is also simulated better for stratiform and total precipitation than for convective precipitation, for which several RCMs produce unrealistic slopes. Extremes are underestimated for convective precipitation while they tend to be slightly overestimated for stratiform precipitation, thus resulting in a relatively good reproduction of extremes in total precipitation amounts. The results suggest that the examined ensemble of RCMs suffers from substantial deficiencies in reproducing precipitation processes and support previous findings that climate models’ errors in precipitation characteristics are mainly related to deficiencies in the representation of convection.  相似文献   

Assimilating continental mean temperatures to reconstruct the climate of the late pre-industrial period     

Anastasios Matsikaris  Martin Widmann  Johann Jungclaus 《Climate Dynamics》2016,46(11-12):3547-3566

  相似文献   

Developing an early warning system for a very slow landslide based on displacement monitoring   总被引：2，自引：0，他引：2  

Renato Macciotta  Michael Hendry  C. Derek Martin 《Natural Hazards》2016,81(2):887-907

  相似文献   

Anthropogenic impacts on nitrogen fixation rates between restored and natural Mediterranean salt marshes          下载免费PDF全文

Serena Moseman‐Valtierra  Lisa A. Levin  Rose M. Martin 《Marine Ecology》2016,37(2):370-379

To test the effects of site and successional stage on nitrogen fixation rates in salt marshes of the Venice Lagoon, Italy, acetylene reduction assays were performed with Salicornia veneta‐ and Spartina townsendii‐vegetated sediments from three restored (6–14 years) and two natural marshes. Average nitrogen fixation (acetylene reduction) rates ranged from 31 to 343 μmol C₂H₄·m^?2·h^?1 among all marshes, with the greatest average rates being from one natural marsh (Tezze Fonde). These high rates are up to six times greater than those reported from Southern California Spartina marshes of similar Mediterranean climate, but substantially lower than those found in moister climates of the Atlantic US coast. Nitrogen fixation rates did not consistently vary between natural and restored marshes within a site (Fossei Est, Tezze Fonde, Cenesa) but were negatively related to assayed plant biomass within the acetylene reduction samples collected among all marshes. Highest nitrogen fixation rates were found at Tezze Fonde, the location closest to the city of Venice, in both natural and restored marshes, suggesting possible site‐specific impacts of anthropogenic stress on marsh succession.  相似文献