Permian/Triassic Boundary and Its Correlation in the Daxian-Xuanhan Area, Northeastern Sichuan Province, China

There are different opinions about the Permian/Triassic boundary and its correlation in the Daxian-Xuanhan area because of lacking typical lithological symbols and fossil criterions. Especially, it is very hard to determine the Permian/Triassic boundary in the Daxian-Xuanhan buried areas. This brings many difficulties to geological research and oil and gas exploration. Based on field investigation and studies of well cores, newly found fossils, lithological characteristics and well log analyses, the authors discussed the Permian/Triassic boundary in the Daxian-Xuanhan area and brought forward a specific scheme for its determination and regional correlation.     

东昆仑大干沟火山岩SHRIMP 锆石U-Pb测年及其地质意义

东昆仑大干沟以北地区造山后形成的牦牛山组磨拉石建造不整合覆盖于前泥盆系之上,其形成时代对限定柴达木盆地加里东造山作用的结束时间及晚古生代裂解作用的开始时间具有重要意义。应用单颗粒锆石离子探针质谱仪（SHRIMP）方法,对牦牛山组上部火山岩段的样品进行精确的锆石U-Pb测年。结果表明,牦牛山组上段火山岩样品DG01和DG02中的岩浆锆石206Pb/238U平均年龄分别为403.6±5.1Ma和409±3.4Ma。综合前人研究认为,造山后牦牛山组伸展型磨拉石的形成时代为晚志留世—早泥盆世,限定了晚古生代裂解的开始时间,也意味着早古生代加里东造山运动在晚志留世—早泥盆世之前已经结束。     

Defining megathrust tsunami source scenarios for northernmost Cascadia

Natural Hazards - Disaster insurance is an effective way in reducing and sharing natural disaster risk. In this paper, a special risk management model based on the cooperative insurance among the...     

西南喀斯特地区石漠化综合治理:成效、问题与对策

西南喀斯特地区石漠化与贫困问题相互交织,是该区域社会经济可持续发展的瓶颈。近二十年来,通过实施植被恢复、水土保持、生态移民等一系列治理措施,石漠化整体扩展的趋势得到初步遏制,由过去持续扩展转变为净减少,西南喀斯特地区生态状况呈良性发展态势,但防治形势仍很严峻,迫切需要寓经济发展于生态治理之中。本文在分析石漠化综合治理成效、存在问题的基础上,探讨了基于民生改善的石漠化防治对策。认为今后应在系统梳理和总结一期治理经验和不足的基础上,进一步加强石漠化演变规律及其关键驱动因子、喀斯特关键带结构与功能变化、植被与水文过程相互作用等基础研究,将植被恢复与生态服务提升、民生改善有机结合,健全“造血”功能,培育和发展与生态治理方向相适应的生态衍生产业,助力扶贫攻坚,实现生态治理与脱贫致富双赢,促进该区域社会经济协同发展及西南生态安全屏障建设。      

基于拉格朗日方法的一次南疆西部特大暴雨水汽来源分析

利用新疆自动气象站资料、NCEP/NCAR再分析资料、GDAS数据,基于拉格朗日方法的气流轨迹模式（HYSPLITv4.9）,对2018年5月16—22日南疆西部特大暴雨过程的水汽源地和输送路径进行了分析。此次HYSPLIT后向轨迹模拟结果表明,暴雨水汽源于巴伦支海、喀拉海、挪威海和地中海,两地的水汽先分别沿西北气流和偏西气流向下游地区输送。水汽轨迹在哈萨克丘陵汇聚后进入北疆,再绕过天山东侧到达罗布泊地区后随低层的偏东急流抵达暴雨区上空。虽然从巴伦支海、喀拉海、挪威海出发的水汽轨迹略多于地中海,但两地的水汽贡献率分别占62%和38%。因此,巴伦支海、喀拉海、挪威海的水汽对于此次暴雨起到明显的增强作用。另外,后向轨迹模拟结果中并未出现从孟加拉湾出发的低层东方路径水汽,说明该区域的水汽并不是构成南疆西部暴雨水汽的必要条件。北极挪威海、巴伦支海、喀拉海地区海表温度异常偏高,有利于水汽源地蒸发增强和上升气流背景场的形成,北极海域的温度异常对于区域气候变化有很好的指示意义。     

Confidence levels for tsunami-inundation limits in northern Oregon inferred from a 10,000-year history of great earthquakes at the Cascadia subduction zone

To explore the local tsunami hazard from the Cascadia subduction zone we (1) evaluate geologically reasonable variability of the earthquake rupture process, (2) specify 25 deterministic earthquake sources, and (3) use resulting vertical coseismic deformations for simulation of tsunami inundation at Cannon Beach, Oregon. Maximum runup was 9–30 m (NAVD88) from earthquakes with slip of ~8–38 m and M _w ~8.3–9.4. Minimum subduction zone slip consistent with three tsunami deposits was 14–15 m. By assigning variable weights to the source scenarios using a logic tree, we derived percentile inundation lines that express the confidence level (percentage) that a Cascadia tsunami will not exceed the line. Ninety-nine percent of Cascadia tsunami variation is covered by runup ≤30 m and 90% ≤16 m with a “preferred” (highest weight) value of ~10 m. A hypothetical maximum-considered distant tsunami had runup of ~11 m, while the historical maximum was ~6.5 m.     

贵州省安顺市西秀区旧州(西部)煤层综合对比分析

本文通过贵州省安顺市西秀区旧州(西部)煤炭普查项目的具体实施,对勘查区含煤岩系的地层岩性、物性特征、地层组合特征等进行了综合对比分析,阐述了该区煤层对比的研究方法。     

湘黔桂交界区贵州省从江县黎家坡南华系剖面新观察——一条良好的南华大冰期沉积记录剖面

从江县黎家坡南华系剖面位于黔桂交界处,交通尚便,是一条地层发育良好、厚度巨大、沉积连续、层序完整、顶底界线清楚的剖面。内部岩石地层单位由下至上依次为:长安组、富禄组和黎家坡组,其划分标志清楚,易于识别和掌握,并可进行区域对比。在剖面上,南华系与下伏青白口系下江群隆里组和上覆震旦系陡山沱组均为整合接触。该剖面较完整而连续地记录了该区南华大冰期(包括长安冰期、富禄间冰期和南沱冰期)的沉积演化史,是研究雪球事件的良好场所之一。     

Impacts of land use and land cover changes upon organic productivity values in Karst ecosystems: a case study of Northwest Guangxi, China

Karst areas are one of the most fragile regions in the world. The Karst environment is very common in southwest China with severe poverty and environmental degradation. Therefore, it is necessary to monitor the Karst ecosystem and its ability to provide goods and services for society. In this paper, we analyzed the spatial distribution of organic productivity values (OPV) in Northwest Guangxi, China in 1985, 1990, 2000, and 2005 using remote sensing and geographic information system techniques. OPV showed a decreasing trend in the last 20 years though there were fluctuations. OPV was 184.85, 117.53, 163.66 and 177.25 million Yuan in 1985, 1990, 2000 and 2005, respectively. Woodland and shrub were the two largest contributors to total OPV. They accounted for 70.51%, 69.13%, 73.92% and 66.23%, respectively, in those four years. Conversely, OPVof residential and barren rock was low with a percentage of 0.70%, 0.56%, 0.57% and 0.90%, respectively. Spatially, OPVis higher in the west than in the east. However, OPV increased in typical Karst areas but decreased in non-Karst areas. Our study indicates that ecosystem conditions in Karst areas had improved because of the application of rocky desertification control policies.