冲绳海槽西部陆坡第四纪沉积地层划分   总被引：1，自引：0，他引：1  

董刚  蔡峰  闫桂京  李清  梁杰  孙运宝  骆迪  李昂 《地质学报》2018,92(12):2550-2560

冲绳海槽西部陆坡是认识深海斜坡沉积的重要区域。通过对高分辨率地震资料的精细解释,结合已有的研究成果,在冲绳海槽西部陆坡海底以下识别出4个主要的地震层序界面,相应地划分出四个主要地震层序,各层序分别对应全新世沉积层(Q4)、晚更新世沉积层(Q3)、中更新世沉积层(Q2)和早更新世沉积层(Q1)。从陆坡上部往下由斜交前积反射结构过渡到杂乱的反射结构,在地震剖面上可识别出杂乱的丘形反射单元,是滑塌体和重力流沉积的典型地震反射特征,反映出一种高能的、极不稳定的沉积环境。海槽轴部以平行-亚平行的地震反射特征为主,显示了稳定的深海-半深海的沉积环境。地震反射结构的多样性反映了冲绳海槽西部陆坡沉积环境的复杂性和沉机作用类型的多样性,沉积地层结构是多种因素共同作用的结果。东海陆架和冲绳海槽发育相同的第四纪地层垂向序列,同时冲绳海槽西部陆坡与东海陆架第四纪沉积层在层序界面、沉积层厚度、变形程度和产状等方面存在着差异,单靠地震资料来进行两个地区的地层对比存在着不确定性。  相似文献   

贵州铜仁一次罕见暴雪过程分析          下载免费PDF全文

冉仙果 《中低纬山地气象》2020,44(6):1-8

本文将利用常规探测资料、NCEP再分析资料和多普勒雷达资料,对2018年12月29～30日铜仁市暴雪过程的环流形势特征与成因进行分析,结果表明：此次暴雪过程发生在高空南支槽、多波动槽东移、700hPa西南暖湿急流输送及850hPa东北回流冷垫的环流背景下,表现出持续时间长、范围广、强度大、积雪深的特征;强降雪阶段对流层低层有来自孟湾的源源不断的水汽输送,湿层厚度增强,且有较强的水汽辐合;700hPa较强的垂直上升运动及对流层中低层较强的垂直风切变利于暴雪天气的发生;强降雪时刻暴雪区800hPa以上位于高层冷平流、低层暖平流的叠加区域,为不稳定大气;此次降雪具有对流性和持续性特征,雷达反射率回波云团具有列车效应。  相似文献   

Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa Trough) behind Ryukyu Arc：A review   总被引：9，自引：2，他引：7  

YAN Quanshu  SHI Xuefa 《海洋学报(英文版)》2014,33(4):1-12

Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc–Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to indicate the relationship between the subduction sources(input) and arc or back-arc magmas(output) in the Philippine Sea Plate–Ryukyu Arc–Okinawa Trough system(PROS). The results obtained showed that several components were variably involved in the petrogenesis of the Okinawa Trough lavas: sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt(MORB)-type mantle, and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies the primitive mantle wedge beneath the Ryukyu and subcontinental lithospheric mantle(SCLM) beneath the Okinawa Trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the "seafloor spreading" process in the southwest segment, "rift propagation" process in the middle segment, and "crustal extension" process in the northeast segment, and a nascent ocean basin occurs in the southwest segment.  相似文献   

冲绳海槽中段沉积物物源识别及其热液活动指示     

魏杰瑞  黄朋 《海洋科学》2021,45(12):8-17

冲绳海槽中段热液活动区表层沉积物的主、微量和稀土元素分析结果表明:区内沉积物主要由陆源物质与热液源物质组分组成,Hg、Au、Sb、Cu、Pb、Zn、Ba、As、Fe和Co等微量元素富集;沉积物的化学风化程度中等,A-CN-K图解表明其暂未受到钾交代影响,且其母岩成分接近花岗闪长岩;北美页岩标准化稀土配分模式曲线整体较为平坦,轻重稀土分馏较弱,部分样品具有与热液流体类似的明显正铕异常.受热液活动影响,部分沉积物中的Fe、Cu、As、Pb和Zn显著富集,结合样品所处站位,整体显示含金属沉积物-过渡沉积物-正常沉积物的空间分配模式.结合(La/Sm)N、(La/Yb)N比值指示区内沉积物的陆源物质主要来自于黄河与台湾岛河流.  相似文献   

Effects of topography on the sub-tidal circulation in the southwestern Huanghai Sea (Yellow Sea) in summer   总被引：1，自引：0，他引：1  

WANG Bin  LI Yao  YUAN Dongliang 《海洋学报(英文版)》2013,32(3):1-9

A nested circulation model system based on the Princeton ocean model(POM) is set up to simulate the currentmeter data from a bottom-mounted Acoustic Doppler Profiler(ADP) deployed at the 30 m depth in the Lunan(South Shandong Province,China) Trough south of the Shandong Peninsula in the summer of 2008,and to study the dynamics of the circulation in the southwestern Huanghai Sea(Yellow Sea).The model has reproduced well the observed subtidal current at the mooring site.The results of the model simulation suggest that the bottom topography has strong steering effects on the regional circulation in summer.The model simulation shows that the Subei(North Jiangsu Province,China)coastal current flows northward in summer,in contrast to the southeastward current in the center of the Lunan Trough measured by the moored currentmeter.The analyses of the model results suggest that the southeastward current at the mooring site in the Lunan Trough is forced by the westward wind-driven current along the Lunan coast,which meets the northward Subei coastal current at the head of the Haizhou Bay to flow along an offshore path in the southeastward direction in the Lunan Trough.Analysis suggests that the Subei coastal current,the Lunan coastal current,and the circulation in the Lunan Trough are independent current systems controlled by different dynamics.Therefore,the current measurements in the Lunan Trough cannot be used to represent the Subei coastal current in general.  相似文献   

Declining nutrient concentrations in the northeast Atlantic as a result of a weakening Subpolar Gyre     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

Between 1996 and the mid-2000s the upper waters (200–700 m) of the Rockall Trough became warmer (+0.72 °C), saltier (+0.088) and reduced in nitrate and phosphate (−2.00 µM and −0.14 µM respectively). These changes, out-with calculated errors, can be explained by the varying influence of southern versus subpolar water masses in the basin as the Subpolar Gyre weakened and contracted. Upper water properties strongly correlate with a measure of the strength of the Subpolar Gyre (the first principal component of sea surface height over the Subpolar North Atlantic) prior to the mid-2000s. As the gyre weakens, the upper layers of the trough become warmer (r−0.85), more saline (r−0.86) and reduced in nitrate and phosphate (r+0.81 and r+0.87 respectively). Further the proportion of subpolar waters in the basin decreases from around 50% to less than 20% (r+0. 88). Since the mid−2000s the Subpolar Gyre has been particularly weak. During this period temperatures decreased slightly (−0.21 °C), salinities remained near constant (35.410±0.005) and phosphate levels low and stable (0.68±0.02 µM). These relative lack of changes are thought to be related to the maximum proportion of southern water masses within the Rockall Trough having been reached. Thus the upper water properties are no longer controlled by changes in the relative importance of different water masses in the basin (as prior to the mid-2000s), but rather a different process. We suggest that when the gyre is particularly weak the interannual changes in upper water properties in the Rockall Trough reflect changes in the source properties of the southern water masses. Since the early-2000s the Subpolar Gyre has been weaker than observed since 1992, or modelled since 1960–1970. Hence upper waters within the Rockall Trough may be warmer, saltier and more depleted in nitrate and phosphate than at any time in the last half century.  相似文献   

冲绳海槽中部A7孔沉积物地球化学记录及其对古环境变化的响应   总被引：4，自引：0，他引：4  

李军 《海洋地质与第四纪地质》2007,27(1):37-45

对取自冲绳海槽中部的A7孔沉积物进行了元素地球化学的测试与分析,配合高分辨率测年和氧同位素数据,探讨了冲绳海槽中部18000年以来的元素地球化学变化特征及其控制因素。使用R型因子分析方法,将分析的20种常量与微量元素分为4个主要的因子:因子I主要由Al、Ti、Th、Rb、Mg、U和Zn等元素组成,代表了陆源物质有关的元素组合,可作为陆源物质输入的指示因子;因子II主要由Ca、Sr、Ba、P等元素组成,代表了与生物作用有关的元素组合,可作为古生物生产力指示因子。根据各元素及其组合随时间的变化特征,整个A7孔沉积物可明显分为4段:18-15 kaBP(Ⅰ),15-8 kaBP(Ⅱ),8-2 kaBP(Ⅲ)和2 kaBP以来(Ⅳ),前3段中都表现出陆源物质先增加再减少的变化趋势,古生物生产力的变化相对复杂,规律性不强,但总体表现出与陆源物质输入相反的变化趋势;第4段中则表现出2 kaBP年以来陆源物质的输入有一定的加强,而古生产力则没有大的变化。在7.3 kaBP左右发生的火山物质快速堆积事件对柱状沉积物的地球化学特征产生了较大的影响,也使陆源物质输入和古生物生产力急剧降低。自18 kaBP年以来,元素地球化学组成的变化主要受温度、海平面变化、黑潮水的“摆动”的影响,而火山沉积也造成了一定的影响。  相似文献   

南海南沙海槽深部热状态及其构造意义     

任自强  施小斌  王晓芳  赵鹏  谌永强 《热带海洋学报》2021,40(4):98-109

南沙海槽是古南海俯冲消亡、南沙地块与婆罗洲碰撞的关键区域, 其构造演化史记录了南海前世今生的重要信息。为深入认识对其构造变形有重要影响的南沙海槽深部热状态, 本文首先利用热传输方程分析了滑坡体快速堆积的热披覆效应对海槽底部深水区海底观测热流的影响, 然后利用磁异常的频谱分析技术获取南沙海槽及其邻区的居里面深度。结果表明, 受沉积物快速堆积的影响, 南沙海槽底部深水区文莱滑坡范围内现今海底热流测量值仅为深部背景热流的60%~77%, 推测该区深部背景热流约为77~98mW·m^-2; 南沙海槽内居里面深度一般小于16km, 比位于其北侧的南沙岛礁区居里面深度(18~24km)小。现今南沙海槽区深部具有较高的背景热流, 该区较高的热状态与其地壳强烈减薄特征对应, 是华南陆缘裂陷和南海形成演化的结果。  相似文献   

冲绳海槽火山岩地球化学特征及岩浆源区地幔性质探讨     

张宇蛟  翟世奎 《海洋学报》2021,43(1):44-54

冲绳海槽是因菲律宾海板块俯冲于欧亚板块之下,在陆壳上发育起来的一个初始的弧后盆地,是研究弧后扩张作用早期盆地演化、岩浆作用和壳幔过程的天然实验室.尽管迄今对冲绳海槽已经做了大量的调查研究工作,但仍存在一些颇有争议或亟待解决的科学问题,如:冲绳海槽酸性浮岩与基性玄武岩之间的成因联系,冲绳海槽不同区段构造背景对岩浆作用的控...  相似文献   

Late Ordovician (Sandbian) brachiopods from the Mweelrea Formation,South Mayo,western Ireland: stratigraphic and tectonic implications     

David A. T. Harper  Matthew A. Parkes  Brian J. McConnell 《Geological Journal》2010,45(4):445-450

A Late Ordovician (Sandbian), Scoto‐Appalachian brachiopod fauna from the Mweelrea Formation in western Ireland confirms a location for the South Mayo Trough adjacent to the Laurentian margin, characterized at this time by a succession of marine excursions over fluviatile environments. The new, younger biostratigraphical data help to constrain the timing of late Grampian folding of this part of the South Mayo Trough. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献