JAIME AMOROCHO     

E. H. Lloyd 《水文科学杂志》2013,58(3)

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Ice marginal dynamics during surge activity,Kuannersuit Glacier,Disko Island,West Greenland     

David H. Roberts  Jacob C. Yde  N. Tvis Knudsen  Antony J. Long  Jerry M. Lloyd 《Quaternary Science Reviews》2009,28(3-4):209-222

The Kuannersuit Glacier surged 11 km between 1995 and 1998. The surge resulted in the formation of an ice cored thrust moraine complex constructed by subglacial and proglacial glaciotectonic processes. Four main thrust zones are evident in the glacier snout area with phases of compressional folding and thrusting followed by hydrofracture in response to the build-up of compressional stresses and the aquicludal nature of submarginal permafrost and naled. Various types of stratified debris-rich ice facies occur within the marginal zone: The first (Facies I) comprises laterally continuous strata of ice with sorted sediment accumulations, and is reworked and thrust naled ice. The second is laterally discontinuous stratified debris-rich ice with distinct tectonic structures, and is derived through subglacial extensional deformation and localised regelation (Facies II), whilst the third type is characterised by reworked and brecciated ice associated with the reworking and entrainment of meteoric ice (Facies III). Hydrofracture dykes and sills (Facies IV) cross-cut the marginal ice cored thrust moraines, with their sub-vertically frozen internal contact boundaries and sedimentary structures, suggesting supercooling operated as high-pressure evacuation of water occurred during thrusting, but this is not related to the formation of basal stratified debris-rich ice. Linear distributions of sorted fines transverse to ice flow, and small stratified sediment ridges that vertically cross-cut the ice surface up-ice of the thrust zone relate to sediment migration along crevasse traces and fluvial infilling of crevasses. From a palaeoglaciological viewpoint, marginal glacier tectonics, ice sediment content and sediment delivery mechanisms combine to control the development of this polythermal surge valley landsystem. The bulldozing of proglacial sediments and the folding and thrusting of naled leads to the initial development of the outer zone of the moraine complex. This becomes buried in bulldozed outwash sediment and well-sorted fines through surface ablation of naled. Up-ice of this, the heavily thrust margin becomes buried in sediment melted out from basal debris-rich ice and subglacial diamicts routed along thrusts. These mechanisms combine to deliver sediment to supraglacial localities, and promote the initial preservation of structurally controlled moraines through insulation, and the later development of kettled dead ice terrain.  相似文献   

Thermal structure and tectonic evolution of the Scandian orogenic wedge,Scottish Caledonides: integrating geothermometry,deformation temperatures and conceptual kinematic‐thermal models     

J.R. Thigpen  R.D. Law  C.L. Loehn  R. A. Strachan  R.J. Tracy  G.E. Lloyd  B.L. Roth  S.J. Brown 《Journal of Metamorphic Geology》2013,31(8):813-842

In the Caledonides of northwest Scotland, two independent geothermometers (Fe‐Mg exchange and quartz c‐axis fabric opening angle) are used to characterize the thermal structure of the lower part of the Scandian (435–420 Ma) orogenic wedge within the Moine, Ben Hope and Naver‐Sgurr Beag thrust sheets. Traced from west (foreland) to east (hinterland), Fe‐Mg exchange thermometry yields peak or near‐peak temperatures ranging from 484 ± 50 °C to 524 ± 50 °C in the immediate hangingwall of the Moine thrust to 601 ± 50 °C in the immediate hangingwall of the Ben Hope thrust, to 630 ± 50 °C in the Naver thrust sheet. Preserved metamorphic facies and textural relationships are consistent with thermometric estimates. Deformation temperatures calculated from quartz c‐axis fabric opening angles across two similar orogen‐perpendicular transects also yield systematic increases (Glen Golly – Ben Klibreck, 520–630 °C; Ullapool‐Contin, 465–632 °C) traced towards the Naver and Sgurr Beag thrusts. In addition, deformation temperatures show a pronounced increase along the leading edge of the Moine thrust sheet moving south towards the Assynt window, which is interpreted to reflect deeper exhumation of the thrust plane above the Assynt footwall imbricate stack. Because temperatures calculated from metamorphic assemblages are within error of the quartz fabric‐derived deformation temperatures that are of demonstrably Scandian age, the metamorphic sequence between the Moine and Naver‐Sgurr Beag thrusts is interpreted to have developed during the Scandian orogeny. Integration of our results with previous 2D thermal‐mechanical studies allows development of new conceptual thermal‐kinematic models of Scandian orogenesis that may be broadly applicable to other collisional systems. Furthermore, it highlights the critical nature of coupling between orogen kinematic and thermal evolution.  相似文献   

High-speed knots in the hourglass-shaped planetary nebula Hubble 12     

N. M. H. Vaytet  A. P. Rushton  M. Lloyd  J. A. López  J. Meaburn  T. J. O'Brien  D. L. Mitchell  D. Pollacco 《Monthly notices of the Royal Astronomical Society》2009,398(1):385-393

We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and long-slit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1-m San Pedro Mártir telescope. We reveal, for the first time, the presence of end caps (or knots) aligned with the bipolar lobes of the planetary nebula shell in a deep [N  ii ]λ6584 image of Hb 12. We measured from our spectroscopy radial velocities of  ∼120 km s⁻¹  for these knots.
We have derived the inclination angle of the hourglass-shaped nebular shell to be ∼65° to the line of sight. It has been suggested that Hb 12's central star system is an eclipsing binary which would imply a binary inclination of at least 80°. However, if the central binary has been the major shaping influence on the nebula, then both nebula and binary would be expected to share a common inclination angle.
Finally, we report the discovery of high-velocity knots with Hubble-type velocities, close to the core of Hb 12, observed in Hα and oriented in the same direction as the end caps. Very different velocities and kinematical ages were calculated for the outer and inner knots showing that they may originate from different outburst events.  相似文献   

内蒙古西拉沐伦成矿带碾子沟钼矿床成矿流体地球化学特征   总被引：7，自引：3，他引：4  

张作伦  刘建明  段晓侠  陈伟军 《岩石学报》2010,26(5):1375-1385

碾子沟钼矿床是内蒙古西拉沐伦钼多金属成矿带中石英脉型钼矿床的典型代表,矿体以石英大脉形式产于燕山期中粗粒黑云母二长花岗岩内,受断裂构造控制。流体包裹体研究发现包裹体均为气液两相,按照相比不同,可进一步分为WL型(5%～20%)和WV型(20%～50%)。Ⅰ阶段流体为低温(89.3～245.2℃)、中低盐度(2.07%～17.96%NaCleqv)流体;Ⅱ阶段流体具有中低温(134.4～458.8℃,峰值170℃～240℃)、中低盐度(0.53%～19.92%NaCleqv)特征;Ⅲ阶段流体为低温(134.9～202.4℃)、中低盐度(4.96%～14.97%NaCleqv)流体。流体成分均以H2O为主(96.1mol%),含少量挥发份CO2、N2、CH4、C2H6、Ar、H2S,阳离子以Na+为主,阴离子以SO42-、Cl-为主,属NaCl-H2O体系。各阶段成矿热液氢、氧同位素特征为:δ18OH2O介于-5.75‰～-1.90‰、δD介于-128.821‰～-109.234‰,说明成矿流体是岩浆热液与古大气降水混合而成。开放的断裂体系为流体混合创造了条件,流体的混合作用是造成碾子沟辉钼矿沉淀成矿的主要原因。这与斑岩型钼矿床的高盐度流体以及以沸腾为主的矿石沉淀机制具有显著区别。  相似文献   

Seismic stratigraphy records the deglacial history of Jakobshavn Isbræ, West Greenland     

Kelly A. Hogan  Justin K. Dix  Jerry M. Lloyd  Antony J. Long  Carol J. Cotterill 《第四纪科学杂志》2011,26(7):757-766

Jakobshavn Isbræ is one of the largest ice streams in the Greenland Ice Sheet, presently draining c. 6.5% of the Inland Ice. Here we present high‐resolution Chirp and Sparker sub‐bottom profiles from a seismic survey conducted just outside of the Jakobshavn Isfjord, which provides detailed insight into the glacimarine sedimentary history of the Jakobshavn ice stream during the Holocene. We observe acoustically stratified and homogeneous sediments that drape an irregular substratum and were deposited between ～10 and c. 7.6k cal a BP. The stratified lower units are interpreted as the product of ice‐proximal glacimarine sedimentation deposited rapidly when the grounded ice margin was located close to depositional basins on topographic highs. The upper acoustically homogenous units reflect suspension settling of fine‐grained material and gravitational flows that were extruded from an increasingly unstable ice margin as the ice retreated into the fjord. Proximity to the ice margin and bedrock topography were the dominant controls on sediment accumulation during deglaciation although the 8.2‐ka cooling event probably influenced the position of the ice margin at the fjord mouth. The post‐glacial sedimentary record is characterized by glacimarine and hemipelagic rainout with an increased ice‐rafted detritus fraction that records sedimentation following ice stream retreat into Jakobshavn Isfjord sometime after c. 7.8k cal a BP. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Studies on groundwater recharge characteristics at a reclaimed land site with an equatorial climate using time‐series and spectral analyses     

Stephen Boon Kean Tan  Eng Ban Shuy  Lloyd Hock Chye Chua  Woon Kang Yee 《水文研究》2007,21(7):939-948

Groundwater recharge studies are essential for investigating the feasibility of using the reclaimed lands in Singapore for subsurface storage and recovery of water. Through time‐series and spectral analyses, net recharge percentages and stress‐filtering characteristics at the reclaimed land were found to depend strongly on the stress transfer velocity, which was a combined function of rainfall pattern and vadose zone thickness. Based on stress transfer velocity, a theory was established to provide logical explanations for the rainfall–recharge relationship, the observed stress‐filtering characteristics and the recharge percentage characteristics at the unconfined sandy aquifer. Although the reclaimed land site has a lithollogically homogeneous soil profile, a non‐uniform recharge pattern was observed to be influenced pronouncedly by the uneven density distribution of bush grasses. Under a bare soil condition, significantly lower recharge percentages were observed for areas under the influence of offshore tides. The unconfined sandy aquifer appears to dampen out the wave propagation of offshore tides rapidly within a short distance from the tidal source, though it has a fairly straight shoreline and is created from highly compacted sand fills. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Progress in understanding of land surface/atmosphere exchanges at high latitudes     

R. J. Harding  S.-E. Gryning  S. Halldin  C. R. Lloyd 《Theoretical and Applied Climatology》2001,70(1-4):5-18

Summary  This paper summarises some of the key results from two European field programmes, WINTEX and LAPP, undertaken in the Boreal/Arctic regions in 1996–98. Both programmes have illustrated the very important role that snow plays within these areas, not only in the determination of energy, water and carbon fluxes in the winter, but also in controlling the length of the summer active season, and hence the overall carbon budget. These studies make a considerable advance in our knowledge of the fluxes from snow-covered landscape and the interactions between snow and vegetation. Also some of the first measurements of greenhouse gas fluxes (carbon dioxide and methane) are reported for the European arctic and sub-arctic. The measurements show a considerable variability across the arctic, with very high instantaneous values from sub-arctic birch and fen areas and extremely low fluxes reported from the polar desert in the high arctic. The overall annual budgets are everywhere limited by the very short active season in these regions. The heat flux over a high latitude boreal forest during late winter was found to be high. At low solar angles the forest shades most of the snow surface, therefore an important part of the radiation never reaches the snow surface but is absorbed by the forest. This indicates that in areas with sparse vegetation and low solar angles, absorption of direct solar radiation is due to an apparent vegetation cover, which is much greater than the actual one. The first steps are taken in using these measurements to improve models, both point soil/vegetation/atmosphere transfer schemes and 3D meteorogical models. The results are encouraging; increasing the realism progressively improves the representation of the fluxes. A start is made in developing landscape, or catchment scale models. There seems to be some hope that comparatively simple relationships between evaporation and photosynthesis and leaf area may be sufficiently robust to allow the use of remotely sensed images to investigate the areally averaged exchanges. It is suspected that high latitude regions will experience considerable climatic and environmental change in the coming decades. A well found prediction of how these regions will respond requires a comprehensive knowledge of how vegetation will respond and how the changed vegetation will interact with the snow cover and the atmosphere. The studies from the LAPP and WINTEX programmes presented in this volume are an important contribution to this understanding and provide a useful foundation for future research. Received March 6, 2001  相似文献   

On the physical controls of the carbon dioxide balance at a high Arctic site in Svalbard     

C. R. Lloyd 《Theoretical and Applied Climatology》2001,70(1-4):167-182

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Hydrochemistry and Ground-Water Mixing in Part of the Lincolnshire Limestone Aquifer, England   总被引：1，自引：0，他引：1  

Adrian R. Lawrence  John W. Lloyd  J. Marcus Marsh 《Ground water》1976,14(5):320-327

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