台湾东北部黑潮表层水入侵东海陆架的季节变化规律   总被引：1，自引：1，他引：0  

赵瑞祥  刘志亮 《海洋科学》2015,39(7):118-123

基于1998～2011 年进入台湾东北部的WOCE-SVP(World Ocean Circulation Experiment -Surface Velocity Programme)计划的Argos 浮标运行轨道数据, 分析了台湾东北部的环流特征、黑潮表层水入侵东海陆架的季节变化规律。结果表明: 在春夏季, 黑潮表层水入侵仅限于陆架外缘, 而在秋冬季, 黑潮表层水可深入东海陆架或进入台湾海峡。自黑潮区入侵至100 m 和150 m 等深线的浮标数量在秋冬季较多, 春夏季较少。台湾海峡的浮标轨迹在春夏季几乎皆为北向, 在秋冬季皆为南向。在秋季, 东海中部和南部陆架会在黑潮西侧出现逆流和涡旋。可见, 台湾东北部环流具有显著的季节特征; 黑潮表层水入侵东海陆架在秋冬季较强, 春夏季较弱。本研究采用最新的Argos 浮标数据, 揭示了台湾东北部黑潮入侵东海陆架的季节变化规律。  相似文献   

基于Argo浮标的西北太平洋环流特征分析     

张志春  袁东亮  李博 《海洋科学》2015,39(7):93-102

基于2004 年1 月～2009 年12 月月平均Argo(Array for Real-time Geostrophic Oceanography)温盐格点资料, 结合P-vector 方法重构了西北太平洋绝对地转流, 重点分析了西北太平洋环流时空变化特征。结果表明, 基于Argo 资料西北太平洋三维结构特征与以前的研究结果是一致的。与WOA09(World Ocean Atlas 2009)计算的纬向流相比, Argo 资料计算的纬向流要偏大。北赤道逆流(NECC)、北赤道流(NEC)、黑潮再生流(KCC)和黑潮延伸体(KE)都有明显的季节和年际变化。NECC 和NEC 基本上呈现春强秋弱的季节变化特征, KCC 和KE 的季节特征与NECC 和NEC 存在反相关系。NECC 和NEC 表现出周期为1～2 a 的年际信号, KCC 和KE 为非周期性的年际信号。表层NEC 流核所在位置以及NEC南边界位置都有南移的趋势。另外, NEC、KCC 和KE 的流量也呈逐渐增大的趋势。  相似文献   

吕宋海峡浮标轨迹的拉格朗日拟序结构分析   总被引：2，自引：0，他引：2       下载免费PDF全文

黄高龙  韦惺  詹海刚 《热带海洋学报》2015,34(1):15-22

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Geodynamic evolution of the Vulcan Sub‐basin,Timor Sea,northwest Australia: A pre‐compression New Guinea analogue?     

G. Chen  K. C. Hill  N. Hoffman  G. W. O'Brien 《Australian Journal of Earth Sciences》2013,60(4):719-736

The Vulcan Sub‐basin lies immediately inboard of the incipient arc‐continent collision in the Timor Sea and comprises part of the Bonaparte Basin system, the northernmost basin on Australia's North West Shelf. Given the high level of preservation of its extensional fabric, the region can provide important analogues for the likely pre‐orogeny architecture of New Guinea, which enables a better understanding of the onset of, and response to, orogenesis. Structural restoration of regional, depth‐converted 2–D seismic lines shows that although the Late Jurassic Swan Graben is significant and contains a thick source‐rock section, the principal phase of crustal extension took place in the Triassic to Middle Jurassic. Within the Vulcan Sub‐basin, the southern Tilted Fault Block Domain records ～10% Triassic to Middle Jurassic extension, whereas <5% upper crustal extension has been measured in the northern Hourglass Domain. Similarly, while Jurassic extension in the Tilted Fault Block Domain is both deep and focused, the Hourglass Domain is expressed as a broad sag to the northeast, indicating a strong underlying basement influence on compartmentalisation. The Vulcan Sub‐basin shows four principal stages of evolution: (i) regional, evenly spaced crustal faulting and subsidence in the Triassic ‐ Middle Jurassic; (ii) focused faulting in the Late Jurassic that created grabens with uplift of the shoulders; (iii) regional subsidence from the Middle Valanginian; and (iv) minor extensional and contractional reactivation in the Mio‐Pliocene. The measured brittle extension is much less than that suggested by modelling of lithospheric subsidence, which suggests long wavelength distribution of strain in the ductile lower crust, with upper crustal extension mainly focused along the continent‐ocean boundary. Along the North West Shelf and on a smaller scale within the Vulcan Sub‐basin per se, the obvious, basement‐involved, rectilinear compartments defined by prominent offsetting of both extensional fault systems and abyssal plains have important implications for the development of the New Guinea orogen. Similar scale compartments are recognised in New Guinea and display different structural styles and hydrocarbon prospectivity. The transfer zones separating the compartments are the sites of the major copper‐gold deposits in New Guinea. Using the Vulcan Sub‐basin ‐ Timor area as an analogue, it can be seen that an arc could originally collide with a promontory, such as what is now Timor, and reactivate the lineaments allowing local extension and mineralisation. In addition, interpretation of the structure of the New Guinea Fold Belt may be aided by considering the effects of compression on the geometry of the Vulcan Sub‐basin and of the similar Carnarvon Basin and adjacent extended and broken Exmouth Plateau.  相似文献   

Peak‐temperature patterns of polyphase metamorphism resulting from accretion,subduction and collision (eastern Tauern Window,European Alps) – a study with Raman microspectroscopy on carbonaceous material (RSCM)     

A. Scharf  M. R. Handy  M. A. Ziemann  S. M. Schmid 《Journal of Metamorphic Geology》2013,31(8):863-880

Raman microspectroscopy on carbonaceous material (RSCM) from the eastern Tauern Window indicates contrasting peak‐temperature patterns in three different fabric domains, each of which underwent a poly‐metamorphic orogenic evolution: Domain 1 in the northeastern Tauern Window preserves oceanic units (Glockner Nappe System, Matrei Zone) that attained peak temperatures (T_p) of 350–480 °C following Late Cretaceous to Palaeogene nappe stacking in an accretionary wedge. Domain 2 in the central Tauern Window experienced T_p of 500–535 °C that was attained either within an exhumed Palaeogene subduction channel or during Oligocene Barrovian‐type thermal overprinting within the Alpine collisional orogen. Domain 3 in the Eastern Tauern Subdome has a peak‐temperature pattern that resulted from Eo‐Oligocene nappe stacking of continental units derived from the distal European margin. This pattern acquired its presently concentric pattern in Miocene time due to post‐nappe doming and extensional shearing along the Katschberg Shear Zone System (KSZS). T_p values in the largest (Hochalm) dome range from 612 °C in its core to 440 °C at its rim. The maximum peak‐temperature gradient (≤70 °C km^?1) occurs along the eastern margin of this dome where mylonitic shearing of the Katschberg Normal Fault (KNF) significantly thinned the Subpenninic‐ and Penninic nappe pile, including the pre‐existing peak‐temperature gradient.  相似文献   

Development of a SWAT extension module to simulate riparian wetland hydrologic processes at a watershed scale     

Yongbo Liu  Wanhong Yang  Xixi Wang 《水文研究》2008,22(16):2901-2915

Using a mass balance algorithm, this study develops an extension module that can be embedded in the commonly used Soil and Water Assessment Tool (SWAT). This module makes it possible to assess effects of riparian wetlands on runoff and sediment yields at a watershed scale, which is very important for aquatic ecosystem management but rarely documented in the literature. In addition to delineating boundaries of a watershed and its subwatersheds, the module groups riparian wetlands within a subwatershed into an equivalent wetland for modelling purposes. Further, the module has functions to compute upland drainage area and other parameters (e.g. maximum volume) for the equivalent wetland based on digital elevation model, stream network, land use, soil and wetland distribution GIS datasets. SWAT is used to estimate and route runoff and sediment generated from upland drainage area. The lateral exchange processes between riparian wetlands and their hydraulically connected streams are simulated by the extension module. The developed module is empirically applied to the 53 km² Upper Canagagigue Creek watershed located in Southern Ontario of Canada. The simulation results indicate that the module can make SWAT more reasonably predict flow and sediment loads at the outlet of the watershed and better represent the hydrologic processes within it. The simulation is sensitive to errors of wetland parameters and channel geometry. The approach of embedding the module into SWAT enables simulation of hydrologic processes in riparian wetlands, evaluation of wetland effects on regulating stream flow and sediment loading and assessment of various wetland restoration scenarios. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Crustal thickening and ductile extension in the NE Greenland Caledonides: a metamorphic record from anatectic pelites   总被引：1，自引：0，他引：1  

K. A. Jones  & R. A. Strachan 《Journal of Metamorphic Geology》2000,18(6):719-735

Caledonian orogenesis in NE Greenland resulted from the collision of Laurentia and Baltica during the Ordovician–Silurian. Anatectic pelites within the metasedimentary Smallefjord Sequence record a clockwise P – T  path, the result of early crustal thickening at c . 445–440 Ma and subsequent exhumation of the high-grade metamorphic core by a combination of ductile extension and tectonic denudation. The early prograde segment of the path followed a shallow, near-isothermal trajectory and attained a metamorphic peak of c . 9.0–10.0 kbar at >790 and <850 °C. Prograde metamorphism initiated anatexis of pelites in the kyanite stability field and continued with sillimanite stable. Inclusion trails in the garnet cores are textural remnants of early deformation, which occurred either before or during prograde metamorphism. The peak metamorphic conditions are anomalously high in the context of thermal models and P – T  paths for continental collision zones. The additional heat input required to promote migmatization may have been provided by advection as lower crustal high-pressure rocks and the uppermost mantle were uplifted following lithospheric thinning at an early stage in the orogeny. The prograde path was interrupted by the development of retrograde extensional shear fabrics defined by biotite+sillimanite and associated with garnet breakdown. Field observations indicate that ductile extension was accompanied by melt extraction, transport and emplacement of intracrustal granites dated at c . 430 Ma. Regional ductile extension and exhumation probably resulted from the development of gravitational instabilities within the overthickened crust during continental collision.  相似文献   

Does a detachment level exist beneath the Ceraunius Fossae? Insights from graben mapping and lost-area balancing analysis     

F. Borraccini  L. Lanci  F.C. Wezel 《Planetary and Space Science》2006,54(7):701-709

We took advantage of the close relationship between graben width and rheology of the involved materials (e.g., number, thickness and spacing of rheological layers, presence of mechanical discontinuities of different nature) and attempted to obtain information about the mechanical stratigraphy of the Ceraunius Fossae area (Northern Tharsis Region). The possible existence of detachment levels beneath the Ceraunius Fossae area were investigated using the lost-area balancing method and a topographic profile derived from Mars Orbiter Laser Altimeter (MOLA) data. Results suggest a marked difference in structural style between the western and eastern sectors of the study area, which is interpreted as a result of different mechanical stratigraphies. On the western sector the maximum depth reached by grabens is well localized within 1000 m from the topographic surface suggesting the existence of a detachment level, which we interpret as a weak horizon at the base of the Late Hesperian-Early Amazonian units. The ductile behaviour of this horizon could be favoured by the presence of volatile reservoir or ice. In the eastern sector of the profile (HNf and Hf units) the maximum depth reached by the grabens is scattered and does not support the existence of clearly defined detachment horizons suggesting that Noachian Fractured Rocks are mechanically homogeneous. A maximum depth, however, could be established.  相似文献   

ADI BAROTROPIC OCEAN MODEL FOR SIMULATON OF KUROSHIO INTRUSION INTO CHINA SOUTHEASTERN WATERS     

方越  方国洪  于克俊 《中国海洋湖沼学报》1996,(4)

In this numerical model for simulating the Kuroshio intrusion into the East and South China Seas,vertically averaged marine hydrodynamic equations governing ocean currents and long-period waves areapproximated by a set of two-time-level semi-implicit finite difference equations. The major terms in-cluding the local acceleration, sea-surface slope, Coriolis force and the bottom friction are approxi-mated with the Crank-Nicholson scheme, which is of second order accuracy. The advection terms are app-roximated with the Leith scheme. The difference equations are split into two sets of alternating directionimplicit quations, each of which has a tridiagonal matrix and can be easily solved. The model reproduces a major Kuroshio intrusion north of Luzon Island, one north of Taiwan Island, andone west of the Tokara Strait. The model shows a current system running from the Luzon Strait to the coastof Vietnam and Hainan Island, through the Taiwan Strait and then into the Tsushima Strait. The summerand winter monso  相似文献   

Pressure–temperature–time evolution of the Central East Greenland Caledonides: quantitative constraints on crustal thickening and synorogenic extension     

A. P. White  K. V. Hodges 《Journal of Metamorphic Geology》2003,21(9):875-897

Whereas geologists have known for three‐quarters of a century that there was significant crustal thickening in the central East Greenland Caledonides, the crucial role of extensional faulting during Caledonian orogenesis has only been recognized during the past decade. In this paper, new petrographic and thermobarometric observations are presented from migmatitic metasedimentary gneisses of the Forsblad Fjord region (c. 72.5°N). Samples of the Krummedal Sequence, collected from the footwall of the upper of two significant splays of the main extensional fault system in the region—the Fjord Region Detachment (FRD)—enable us to establish a relative sequence of metamorphism. Our pressure (P)–temperature (T) results imply a clockwise loop in P–T space. As recorded by mineral assemblages in the Krummedal gneisses, prograde metamorphism involved a net increase of c. 4 kbar and 250 °C, with peak conditions of c. 10.5 kbar at 785 °C. Early burial and heating was followed by near‐isothermal decompression of 4.5 kbar, a process which is attributed to roughly 18 km of tectonostratigraphic throw on the upper splay of the FRD. Combining data reported here with the published data, it is estimated that the approximate tectonostratigraphic throw along the lower splay of the FRD was c. 16 km. In situ U–Th–Pb‐monazite electron microprobe dating suggests that the earliest phase of metamorphism recorded in the Krummedal Sequence gneisses of Forsblad Fjord occurred during the Caledonian orogeny. Furthermore, the combination of our new data with existing conventional TIMS U‐Pb and ⁴⁰Ar/³⁹Ar data imply that: (1) movement along the uppermost splay of the FRD (c. 425–423 Ma) occurred at maximum time‐averaged slip‐rates equivalent to c. 9 mm of vertical displacement per year; and (2) that the final stages of metamorphism occurred prior to c. 411 Ma, although part of this denudation was likely accommodated on overlying extensional structures that may have been active more recently. There is close agreement between our data and results from the Krummedal Sequence north of the field area (72.5°?74°N), and rocks of the Smallefjord Sequence (75°?76°N) that are suggested to correlate with the Krummedal Sequence. This leads us to infer that the events recorded in the Forsblad Fjord region are of orogen‐scale significance.  相似文献