Origin of Taiwan Canyon and its effects on deepwater sediment     

Shang Xu  YingMin Wang  XueChao Peng  HuaYao Zou  Yan Qiu  ChengLin Gong  HaiTeng Zhuo 《中国科学:地球科学(英文版)》2014,57(11):2769-2780

The continental slope of the Taiwan Shoal, which has cultivated numerous submarine canyons, is located in a passive continental margin environment. However, the trend of the Taiwan Canyon, with its 45° intersection angle, is obviously different from that of the erosion valley downward along the continental slope. A distinct break is present in the lower segment of the Taiwan Canyon, which then extends from west to east parallel to the continental slope until finally joining the Manila Trench. By utilizing multiple-beam water depth data, high-resolution seismic data, and sediment cores, this study describes the topographic characteristics of the Taiwan Canyon and provides a preliminary discussion on the origin of the Taiwan Canyon and its effect on deepwater sediment. The terrain, landform, and sediment of the Taiwan Canyon exhibit segmentation characteristics. The upper segment is characterized primarily by erosion, downward cutting with a V shape, and wide development of sliding, slumping, and other gravity flow types. The middle segment is characterized mostly by U-shaped erosion-sedimentation transition and development of an inner levee. The lower segment is characterized primarily by sedimentation and development of a sediment wave. The bottom current has a significant reworking effect on the interior sediments of the canyon and forms reworked sands. The formation and evolution of the Taiwan Canyon is closely related to sediment supply, gravity sliding(slumping), faulting activities, and submarine impaling. Given the sufficient terrigenous clastic supply, the sediments along the continental shelf edge continuously proceed seaward; gliding and slumping in the front edge provide driving forces for the formation of the canyon. Faulting activities result in stratum crushing, and the gravity flow takes priority in eroding the relatively fragile stratum. Thus, the direction of the extension of the canyon crosses the surrounding erosion valley obliquely. Seamounts are formed through submarine impaling. Owing to seamount blocking, the lower segment of the canyon is turned toward the east–west direction. Large amounts of sediments overflow at the turning, forming sediment waves.  相似文献   

湖南娄底市旅游生态足迹趋势分析     

刘辛田  高玉泉  刘加林 《冰川冻土》2014,36(3):751-758

生态足迹分析方法是近年发展起来的一种用生产性土地面积来定量衡量人类对自然资源利用程度和可持续发展能力的新方法. 旅游业对生态环境的影响程度和可持续发展能力可以用旅游生态足迹定量反映出来. 以生态足迹理论为基础,以湖南娄底市为实证对象,对2005-2012年旅游生态足迹、旅游生态承载力变化趋势进行分析. 结果表明：2005-2012年娄底市旅游生态足迹和旅游生态承载力都逐年增加,但二者增幅差异大,2010年是旅游生态盈余转为生态赤字的拐点,当前娄底市旅游发展以生态环境的退化为代价,是一种不可持续的旅游发展状态. 从旅游消费结构看,娄底市旅游生态足迹的7项分足迹中,以交通和餐饮生态足迹相对较大,而住宿、游览、娱乐、购物和废弃物排放产生的生态足迹相对较小. 实现娄底市旅游可持续发展对策：发展低碳旅游,提高资源利用率,合理控制旅游生态足迹的需求;保护旅游生态环境,提高旅游生态承载力;加强旅游生态安全控制,建立生态补偿机制.  相似文献   

三峡库区黄陵背斜形成机理及与滑坡群关系     

王孔伟  张帆  邱殿明 《吉林大学学报(地球科学版)》2015,45(4):1142-1154

黄陵背斜、秭归向斜是三峡地区构造地质研究热点之一,前人将其划归于秦岭造山带的组成部分,认为是东西向构造后期改造的结果;分布于此区的仙女山断裂是否穿越长江也是争论的焦点问题之一.这些问题的解决对澄清研究区地质灾害分布特征具有重要意义.笔者在前人研究的基础上,从沉积学、构造地质学角度,在大量野外地质研究工作的基础上,提出了新的看法:黄陵背斜、秭归向斜、当阳向斜、仙女山断裂同属统一的构造体系,其形成和演化与中国东西部构造格局的变迁一致,黄陵背斜具有断层相关褶皱的特点,秭归向斜具有前陆挠曲型盆地构造属性;仙女山断裂形成之初具有传递断层的属性,后期又经历了引张、挤压演化过程,不存在跨越长江向北延伸的问题;受秭归向斜沉降幅度以及东西向构造与南北向构造复合影响,在研究区形成3个滑坡聚集区,分别为贾家店滑坡聚集区、八字门向家店滑坡聚集区、兴山县城附近滑坡聚集区.  相似文献   

华北板块北缘中段早石炭世构造属性:察哈尔右翼后旗高分异Ⅰ型花岗岩地球化学的制约     

刘群  王挽琼  邱殿明  白新会  张金凤  王新 《吉林大学学报(地球科学版)》2015,45(4):1121-1131

察哈尔右翼后旗二长花岗岩岩体位于华北板块北缘中段.岩体富SiO₂、富K、富碱、低Ca和P、贫Fe和Mg,w(P₂O₅)与w(SiO₂)呈负相关,铝指数(A/CNK)为0.96~1.15,分异指数为90.36~92.96;主要造岩矿物为条纹长石、斜长石和石英,其铁镁矿物主要为黑云母,未出现碱性铁镁矿物和富铝矿物,副矿物为锆石、磁铁矿、磷灰石、榍石和钛铁矿;可见察哈尔右翼后旗二长花岗岩属高分异钙碱性I型花岗岩类.结合较低的w(∑REE)((46.8~94.4)×10^-6)、w(Th)((1.74~2.39)×10^-6)、w(U)((0.27~0.39)×10^-6)和微量元素判别图解,二长花岗岩岩浆源区可能为下地壳,源岩可能为岩石圈地幔.岩石轻重稀土分馏较强 ((La/Yb)_N= 6.52~28.39),δEu以正异常为主(0.83~3.51),富集大离子亲石元素(LILEs,Cs、Rb、Ba和K),亏损高场强元素 (HFSEs,Nb、Ta、P和Ti).地球化学特征反映了二长花岗岩具有火山弧岩石特征,且岩体侵入新元古界埃迪卡拉系什那干群,表明岩体形成于活动大陆边缘弧环境,其侵位反映了古亚洲洋的俯冲岩浆事件.  相似文献   

Effects of hypoxia on biofilms and subsequently larval settlement of benthic invertebrates     

S.G. Cheung  C.Y.S. Chan  B.H.K. Po  A.L. Li  J.Y.S. Leung  J.W. Qiu  P.O. Ang  V. Thiyagarajan  P.K.S. Shin  J.M.Y. Chiu 《Marine pollution bulletin》2014

Biofilms on submerged surfaces are important in determining larval settlement of most marine benthic invertebrates. We investigated if exposure of biofilms to hypoxia would alter the larval settlement pattern and result in a shift in benthic invertebrate community structure in the field. Biofilms were first exposed to hypoxia or normoxia in laboratory microcosms for 7 days, and then deployed in the field for another 7 days to allow for larval settlement and recruitment to occur. Using terminal-restriction fragment length polymorphism of the 16S rRNA gene, this study showed that hypoxia altered the biofilm bacterial community composition, and the difference between the hypoxic and normoxic treatments increased with the time of exposure period. This study also demonstrated significantly different benthic invertebrate community structures as a result of biofilm exposure to hypoxia and that the hypoxic and normoxic treatments were dominated by Hydroides sp. and Folliculina sp., respectively.  相似文献   

Evaluating Mean Magnetic Field in Flare Loops     

Jiong Qiu  Dale E. Gary  Gregory D. Fleishman 《Solar physics》2009,255(1):107-118

We analyze multiple-wavelength observations of a two-ribbon flare exhibiting apparent expansion motion of the flare ribbons in the lower atmosphere and rising motion of X-ray emission at the top of newly-formed flare loops. We evaluate magnetic reconnection rate in terms of V _r B _r by measuring the ribbon-expansion velocity (V _r) and the chromospheric magnetic field (B _r) swept by the ribbons. We also measure the velocity (V _t) of the apparent rising motion of the loop-top X-ray source, and estimate the mean magnetic field (B _t) at the top of newly-formed flare loops using the relation 〈V _t B _t〉≈〈V _r B _r〉, namely, conservation of reconnection flux along flare loops. For this flare, B _t is found to be 120 and 60 G, respectively, during two emission peaks five minutes apart in the impulsive phase. An estimate of the magnetic field in flare loops is also achieved by analyzing the microwave and hard X-ray spectral observations, yielding B=250 and 120 G at the two emission peaks, respectively. The measured B from the microwave spectrum is an appropriately-weighted value of magnetic field from the loop top to the loop leg. Therefore, the two methods to evaluate coronal magnetic field in flaring loops produce fully-consistent results in this event.  相似文献   

江苏省年最大风速的时空分布及突变分析   总被引：5，自引：2，他引：3  

陈兵  邱辉  赵巧华 《气象科学》2010,30(2):214-220

根据江苏省34a年最大风速资料,用EOF、REOF方法研究了江苏省年最大风速的空间分布形式和长期变化趋势。结果表明:(1)34a年最大风速基本在11m/s以上,其中最大值区位于盐城的南部和南通的北部,在15m/s以上。近34a来具有明显的波动,整体上呈减小的趋势。(2)EOF分解的第一特征向量场空间分布绝大部分为正值,说明其变化具有极好的一致性,第一时间系数的变化相当于年变化。但是各特征向量场之间的特点相差明显。(3)REOF分析方法表明其可以被分为5个区,分别为西北区、西南区、东南区、中部地区、东北区,各个区域的年最大风速均呈现减小的趋势,但是减小的程度各不相同。突变特征各个区域表现也不同。  相似文献   

演播稿质量与提升地市级天气预报节目的探讨   总被引：1，自引：1，他引：0  

丘良  陈阳 《气象研究与应用》2010,31(1):110-112

从节目内容的策划、气象资料的选择、节目框架的排版、画面图像的设计、演播稿的构思等方面来分析当前广西地市级《天气预报》演播稿存在的问题,找出地市级天气预报演播稿的撰写与提升节目相应对策。  相似文献   

闽北烤烟移栽期的预报   总被引：1，自引：0，他引：1  

黄廷炎  杨善恭  周博扬  魏入圣  江彩英  邱晓光 《广西气象》2010,(1):57-59,62

用对比分析和相关分析相结合的方法选取预报因子,分析得出移载日期与前期冷空气活动有关,且冷空气活动存在一定韵律关系。用逐步回归建立的预报方程效果好,且对移栽期特迟和特早有较好的预报能力。  相似文献   

2008年台风“凤凰”的移动过程及对江苏降水的影响   总被引：4，自引：1，他引：3  

王龙  周伟灿  倪东鸿  彭丽霞  丘文先 《气象与减灾研究》2009,32(4):25-31

分析了2008年08号台风“凤凰”的移动过程及其对江苏降水的影响。由其移动路径和移动过程中副热带高压的变化,以及影响江苏降水环流形势的演变可以发现,“凤凰”的移动路径主要受强大而稳定的副热带高压引导;西南季风和副热带高压南侧的东南风为台风降水输送了丰富的水汽,给江苏地区强降水提供了有利的环境场;冷空气的侵入也是台风“凤凰”登陆后造成江苏持续性降水的主要原因之一,但同时冷空气的入侵也破坏了台风的暖心结构,加快了台风的消亡。  相似文献