First Report of Avian Tracks from the Cretaceous of Tibet, China     

Xing Li  Chou Chunyong  Martin G. LOCKLEY  Yangchen Dolkar  Chen Xingru  Ma Xinghong  Zhou Wenjun  Xu Hantian 《《地质学报》英文版》2017,91(6):2312-2313

<正>Objective Despite a large number of bird fossils in the Jehol Biota,Mesozoic bird records from other parts of China are dominated by tracks.Late Cretaceous bird tracks are rarely found in China.Reliable reports so far include a Dongyangornipes and Koreanaornis assemblage of early Late Cretaceous age from Dongyang City,Zhejiang Province,China(Azuma et al.,2013).Buckley et al.  相似文献   

生态模型在渔业管理中的应用   总被引：2，自引：1，他引：1  

张崇良  陈勇  韩东燕  邢磊  任一平 《海洋学报》2017,39(10):1-18

随着人们对于海洋生态的认识逐渐深入,渔业等人类活动的影响受到了更多的关注,"基于生态系统的渔业管理"（EBFM）这一概念被越来越多的研究者和国际组织所接受。生态模型为EBFM的实践提供了科学的评估方法和技术工具。与单鱼种评估模型相比,生态模型更多地考虑了系统内的各种生态过程和作用机制,栖息地等环境条件的变化,以及生态系统整体的结构和功能等,依此来反映生态系统的动态变化。由于生态模型是多样化的,关注和涉及不同的目标对象、机制过程、模型结构和参数,本文按照生态模型所关注的生态层次和组分将其分为多物种模型、群落结构模型和生态系统模型3个类型,分析了各类模型的优劣点。本文进一步阐述了生态模型在渔业管理中的应用领域,以管理策略评估为中心的应用方式,以及实践中模型选择和构建所需要注意的问题,还探讨了生态模型中降低不确定性和提高预测能力的方法。  相似文献   

冬季黑潮延伸体海表温度对阿留申低压活动的双周期响应   总被引：1，自引：1，他引：0  

余沛龙  张立凤  刘虎  刘星  朱娟 《海洋学报(英文版)》2017,36(9):1-9

Based on our previous work, the winter sea surface temperature(SST) in the Kuroshio Extension(KE) region showed significant variability over the past century with periods of ~6 a between 1930 and 1950 and ~10 a between1980 and 2009. How the activity of the Aleutian Low(AL) induces this dual-period variability over the two different timespans is further investigated here. For the ~6 a periodicity during 1930–1950, negative wind stress curl(WSC)anomalies in the central subtropical Pacific associated with an intensified AL generate positive sea surface height(SSH) anomalies. When these wind-induced SSH anomalies propagate westwards to the east of Taiwan, China two years later, positive velocity anomalies appear around the Kuroshio to the east of Taiwan and then the mean advection via this current of velocity anomalies leads to a strengthened KE jet and thus an increase in the KE SST one year later. For the ~10 a periodicity during 1980–2009, a negative North Pacific Oscillation-like dipole takes2–3 a to develop into a significant positive North Pacific Oscillation-like dipole, and this process corresponds to the northward shift of the AL. Negative WSC anomalies associated with this AL activity in the central North Pacific are able to induce the positive SSH anomalies. These oceanic signals then propagate westward into the KE region after 2–3 a, favoring a northward shift of the KE jet, thus leading to the warming of the KE SST. The feedbacks of the KE SST anomaly on the AL forcing are both negative for these two periodicities. These results suggest that the dual-period KE SST variability can be generated by the two-way KE-SST-AL coupling.  相似文献   

浙江海域MASNUM海浪模式在台风“达维”“海葵”及“布拉万”过程的波浪数值模拟          下载免费PDF全文

吴欢  汪一航  滕涌  江兴杰  孙宝楠  梅秋莹 《应用海洋学学报》2017,36(2):249-259

利用MASNUM海浪模式、ECMWF高分辨率风场对2012年8月份台风过程下的浙江海域的海浪状况进行了数值模拟,与近岸观测站的风、浪资料进行了对比检验和误差分析,最后针对8月份"达维""海葵"及"布拉万"3个台风过程对浙江海域的影响进行了对比分析.风速验证结果显示2个站点ECMWF风速和观测风速的偏差分别为0.18、-0.34 m/s,平均绝对误差则为2.57、1.96m/s,均方根误差为3.40、2.65 m/s,与观测风速有较好的一致性.海浪验证结果显示8月份有效波高的相关系数在0.84以上;8月份发生的"达维""海葵"及"布拉万"3个台风期间的有效波高、波周期的模拟值与观测值的均方根误差分别介于0.19~0.37 m、0.88~1.28 s,波向的平均绝对误差介于19.39°~37.65°,表明MASNUM海浪模式能够较好的再现浙江海域台风期间的海浪状况,能够较好模拟出浙江近海的最大波高.在数值模拟和实际观测的基础上,进一步的对比分析表明:"海葵"台风期间,浙江外海有效波高的最大值达7.6 m,而"达维"和"布拉万"台风期间,数值显示最大有效波高分别为4.4、5.4 m.  相似文献   

塔里木盆地夏河南层状玄武岩的岩石地球化学特征及地质意义   总被引：1，自引：0，他引：1  

余星  杨树锋  陈汉林  厉子龙  励音骐  丘志力 《岩石学报》2017,33(6):1729-1740

塔里木盆地夏河南玄武岩露头以水平层状分布为最大特征,其玄武岩层和沉积夹层保持了较原始的产状,是研究塔里木盆地二叠纪多期次玄武质岩浆活动的理想场所,是对比盆地内其他玄武质岩浆活动的最佳剖面。本文通过详细的野外和遥感解译工作,报道了夏河南玄武岩的野外产状、岩相学特征和各层玄武岩的地球化学特征,探讨了夏河南玄武岩的岩浆源区和岩浆演化过程。研究认为夏河南玄武岩质岩浆来源于富集的岩石圈地幔,为尖晶石-石榴石二辉橄榄岩经历低程度部分熔融的产物,各层玄武岩的成分差异与部分熔融程度有关,单一层内玄武岩的岩浆演化以分离结晶为主,地壳混染程度较小。夏河南各层玄武岩来源于同一岩浆源区,其特征与柯坪玄武岩相似,可对应于柯坪地区开派兹雷克组的6层玄武岩。研究进一步明确了塔里木盆地早二叠世玄武岩的空间分布特征,证实塔里木早二叠世大火成岩省的玄武质岩浆作用可从柯坪地区延伸到夏河南、塔中、塔西南等地。  相似文献   

Salinization of porewater in a multiple aquitard-aquifer system in Jiangsu coastal plain,China   总被引：1，自引：0，他引：1  

Jing Li  Xing Liang  Yanian Zhang  Yan Liu  Naijia Chen  Alhassan Abubakari  Menggui Jin 《Hydrogeology Journal》2017,25(8):2377-2390

Chemical and isotopic compositions were analyzed in porewater squeezed from a clayey aquitard in Jiangsu coastal plain, eastern China, to interpret the salinity origin, chemical evolution and water-mass mixing process. A strong geochemical fingerprint was obtained with an aligned Cl/Br ratio of 154 in the salinized aquitard porewater over a wide Cl^? concentration range (396–9,720 mg/L), indicating that porewater salinity is likely derived from a mixing with old brine with a proportion of less than 20%. Very small contributions of brine exerted limited effects on water stable isotopes. The relationships between porewater δ¹⁸O and δD indicate that shallow and intermediate porewaters could be original seawater and were subsequently diluted with modern meteoric water, whereas deep porewaters with depleted stable isotopic values were probably recharged during a cooler period and modified by evaporation and seawater infiltration. The cation–Cl relationship and mineralogy of associated strata indicate that porewater has been chemically modified by silicate weathering and ion-exchange reactions. ⁸⁷Sr/⁸⁶Sr ratios of 0.7094–0.7112 further confirm the input source of silicate minerals. Numerical simulations were used to evaluate the long-term salinity evolution of the deep porewater. The alternations of boundary conditions (i.e., the third aquifer mixed with brine at approximately 70 ka BP, followed by recharge of glacial meltwater at 20–25 ka BP, and then mixing with Holocene seawater at 7–10 ka BP) are responsible for the shift in porewater salinity. These timeframes correspond with the results of previous studies on ancient marine transgression-regression in Jiangsu coastal plain.  相似文献   

Experimental and numerical investigations of a catastrophic long-runout landslide in Zhenxiong,Yunnan, southwestern China   总被引：2，自引：1，他引：1  

Yueping Yin  Aiguo Xing  Gonghui Wang  Zhen Feng  Bin Li  Yao Jiang 《Landslides》2017,14(2):649-659

On 11 January 2013, a catastrophic landslide of ～0.2 million m³ due to a prolonged low-intensity rainfall occurred in Zhenxiong, Yunnan, southwestern China. This landslide destroyed the village of Zhaojiagou and killed 46 people in the distal part of its path. The displaced landslide material traveled a horizontal distance of ～800 m with a vertical drop of ～280 m and stopped at 1520 m a.s.l. To examine the possible mechanism and behavior of the landslide from initiation to runout, the shear behavior of soil samples collected from the sliding surface and runout path was examined by means of ring shear tests. The test results show that the shear strength of sample from the sliding surface is less affected by shear rate while the shear rate has a negative effect on the shear strength of runout path material. It is suggested that the source and runout path materials follow the frictional and Voellmy rheology, respectively. Post-failure behavior of the landslide was modeled by using a DAN-W model, and the numerical results show that the selected rheological relationships and parameters based on the results of ring shear tests may provide good performance in modeling the Zhenxiong landslide.  相似文献   

Characteristics and numerical runout modelling of a catastrophic rock avalanche triggered by the Wenchuan earthquake in the Wenjia valley,Mianzhu, Sichuan,China   总被引：3，自引：0，他引：3  

Aiguo Xing  Xiaoyi Yuan  Qiang Xu  Qihua Zhao  Heqing Huang  Qiangong Cheng 《Landslides》2017,14(1):83-98

The 2008 Wenchuan earthquake triggered more than 100 rock avalanches with volumes greater than 10 million cubic metres. The rock avalanche with the longest runout amongst these destructive landslides occurred in the Wenjia valley, Mianzhu, Sichuan, China. The landslide involved the failure of about 27.5 million cubic metres of sandstone from the source area. The displaced material travelled about 4,170 m with an elevation descent of about 1,360 m, equivalent to a fahrböschung of 16.9° and covered an area of 1.5 million square metres, with the final deposited volume of approximately 49 million cubic metres. The catastrophic event destroyed the village of Yanjing, killed 48 people and buried some houses at the mouth of the Wenjia valley. On the basis of a detailed field investigation, we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in two run-ups and a superelevation along the runout path, and downslope enlargement due to the entrainment of path materials. A numerical model (DAN3D) is used to simulate the post-failure behaviour of the rock avalanche. By means of trial and error, a combination of the frictional model and Voellmy model is found to provide the best performance in simulating this rock avalanche. The simulation results reveal that the rock avalanche had a duration of about 240 s and an average velocity of 17.4 m/s.  相似文献   

Numerical analysis of the seismic inertial and kinematic effects on pile bending moment in liquefiable soils     

Rui Wang  Xing Liu  Jian-Min Zhang 《Acta Geotechnica》2017,12(4):773-791

In an effort to study the seismic pile moment induced by the combined structure–pile inertial and soil–pile kinematic effects for single piles and pile groups in liquefiable ground, an extensive series of 3D finite element simulations are conducted in this paper. The roles that lateral inertial and kinematic interactions play on the pile moment are found to differ in different soil–pile–structure systems. Inertial structure force and kinematic soil displacement of the same direction could cause pile head moments of the same or opposite directions depending on the rotational constraint at the pile head. Kinematic interaction has a dominating influence on the pile moment for pile foundations with pile head rotation constrained by the existence of a pile cap, while inertial interaction is strongly influential for free-head piles. The coupling of inertial and kinematic interactions depends on the soil–pile–structure system configuration and the magnitudes of the inertial structure force and the kinematic soil displacement. Many current pseudo-static methods for calculating the seismic pile moment through summing a percentage of the kinematic induced moment with another percentage of the inertial induced moment could produce very inaccurate results under certain conditions.  相似文献   

An experimental study on controlling post-earthquake debris flows using slit dams     

Xing Lin  Miao Huo  Jia-wen Zhou  Tian Cao  Feng-rong Yang  Hong-wei Zhou 《Environmental Earth Sciences》2017,76(22):780

Post-earthquake debris flows often break out in groups frequently, which are usually caused by the abundant loose solid materials that produced by earthquake. Slit dams represent a practical and effective kind of countermeasure for controlling the post-earthquake debris flow. Flume experiments were carried out to study the interaction mechanism and the effect of slit dams on the post-earthquake debris flows. The results showed that affected by the slit dams, some certain types of deposits formed on the upstream. The steeper the flume slope, as well as the greater the width and the density of slits, the easier the lateral deposit became “V” shaped. Otherwise, the lateral deposit was more likely to be “–?” shaped. When the flume slopes were 12°, 16° and 20°, the profiles of the deposits would be long-shallow type, short-thick type and short-shallow type, respectively. The slope of the deposition first decreases and then increases with the flume slope increasing within a certain range. The slit dam can trap the coarse sand and discharge the fine sand. The maximum attenuation rate can reach 44.4%. The effect of this capacity gradually weakens as the flume slope is increased. When the width or the density of slits is smaller, the greater the rate of decrease in peak sand discharge and the greater the effect of peak cutting will be. The reduction in the sediment storage rate is likely due to the increase in the width and the density of the slits. With the increase in flume slope, the sediment storage rate first increases, then decreases, which reaches a maximum value when the flume slope is 16°.  相似文献