内蒙古银额盆地哈日凹陷下白垩统碎屑锆石U-Pb测年及其物源意义*

前人认为银额盆地下白垩统物源主要来自凹陷周缘的造山带或凸起区,但对于下白垩统的物源具体属于何套地层、确切源区位置等问题,并未开展过相关研究。笔者以哈日凹陷为例,通过对该凹陷下白垩统8个沉积岩样品开展地球化学和碎屑锆石U-Pb年代学研究,以期解决以上问题。研究结果表明: (1)碎屑锆石按年龄可以分为三叠纪锆石、二叠纪锆石、石炭纪锆石和古老锆石4类,对应的年龄分别为$237.9\pm3.2\pm-238.3\pm8.4$ Ma, $255.0\pm9.7-285.9\pm4.3$ Ma, $307.0\pm23.0-330.0\pm3.0$ Ma and $434.0\pm4.0-2584.0\pm14.0$ Ma 。(2)微量元素和锆石年龄组成特征表明,下白垩统以二叠系和石炭系物源供给为主,包括二叠纪和石炭纪侵入岩和沉积岩。(3)锆石年龄分布指示哈日凹陷下白垩统物源具有多源区的特征,凹陷西北部的洪格尔吉山、南部的宗乃山和东部的切刀山对其均有物源贡献。(4)3个物源区对巴音戈壁组和苏红图组的物源贡献率具有一定的差异,如宗乃山地区对苏红图组有较大的物源贡献率,这种差异可能由沉积物迁移距离、源区地质体剥蚀速率、构造运动等原因所致。下白垩统物源特征的确定,对于恢复哈日凹陷早白垩世原型盆地、建立早白垩世沉积古地理模型等均具有重要的意义。     

河南夏季高温日数的时空分布特征及500hPa环流型

对河南省40个代表站1961-2005年夏季≥35℃高温日数进行经验正交函数(EOF)展开分析,结果显示,前3个典型场基本能反映河南夏季高温日数分布的主要特征,前3个模态的累积方差贡献率达85%。据此,得出河南夏季≥35℃高温日数的时空分布类型为全省一致型、西北至东南差异型和西南至东北差异型。第一模态对应的时间系数序列的变化幅度最大,第二模态对应的时间系数序列的变化幅度比前一个时间序列要小。第一模态的时间系数演变显示,河南夏季高温日数平均呈减少趋势,且存在2~4 a、8~14 a的周期变化,目前河南夏季高温日数正处于偏多状态中。应用逐日20时500 hPa ECMWF北半球格点资料,对1991-2005年河南典型的大面积持续高温下的环流形势进行普查、分类,分别求各种类型下的环流平均场,从而得到河南省高温的两种环流型,即贝加尔湖高压型和副热带高压型。     

一次1月山东半岛东部极端海效应暴雪的发生机制分析

利用海上浮标站、自动站、多普勒天气雷达、L波段雷达探空、NCEP/NCAR再分析逐6 h和降水等观测资料,结合EVAP雷达风场反演获得的水平风场资料,对2018年1月9—11日一次渤海海效应暴雪过程的产生机制进行了分析。结果表明:此次海效应暴雪过程是一次极端降雪事件,具有强降雪持续时间长、降雪量大、暴雪分布近γ中尺度等特征。暴雪发生前后受两次强冷空气影响,渤海和山东半岛地区持续降温,850 hPa温度降至-18～-16℃,是产生强海效应降雪的有利条件;此次冷空气明显强于12月渤海海效应暴雪,1月产生海效应暴雪的850 hPa温度中位数较12月低约5℃。受强冷空气影响时,海气温差明显增大,海洋向低层大气输送的最大感热通量可达226.8 W·m~(-2),低层大气高湿饱和,导致大气层结不稳定,不稳定局限于850 hPa以下,为浅层对流。雷达反射率因子图上具有明显的"列车效应"。造成窄带回波的原因在于出现了低层切变线,即在山东半岛北部沿海的小范围区域内出现了东北风及西西南风,形成了西北风与东北风、西西南风与东北风的切变线,触发暴雪产生。而东北风达到的高度不超过1.2 km,多在0.6 km以下。通过此次极端暴雪过程的综合观测资料分析,揭示了较少出现的1月海效应暴雪的特征,其形成的环流形势、热力不稳定、动力条件等与常见的12月海效应暴雪基本类似,主要差异在于冷空气强度较12月偏强,这可成为1月海效应暴雪的首要预报着眼点;海上浮标站、雷达风场反演技术是定量揭示海效应暴雪中尺度特征的良好资料和方法。     

单桩复合地基静载荷试验系统的设计与应用研究

复合地基是通过褥垫层的调整作用,充分发挥桩间土的承载作用,使桩土共同承担荷载的地基。基于复合地基的实际工况,设计了一种单桩复合地基静载荷试验系统,既体现了褥垫层的调整作用,又可测得复合地基中桩体、桩问土、复合地基的荷载与其相应的沉降,同时可得出复合地基受力过程中桩土荷载分配过程与桩土应力比,提示了复合地基工作机理。通过工程实例测试,探讨了复合地基的工作机制,为复合地基的科研、设计与检测提供了依据。     

Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea)

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. The eastern Korean margin is rimmed by fundamental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau that is a continental fragment extended and partially segmented from the Korean Peninsula. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and considerably symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions for rifting are recognized: the Onnuri and Hupo Basins were rifted in the east-west direction; the Bandal Basin in the east–west and northwest–southeast directions, suggesting two rift stages. We interpret that the east–west direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated southeastward repeatedly from the Japan Basin toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed the direction to the south, resulting in east–west extension to create the rift basins at the Korean margin. The northwest–southeast direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the Korea Plateau; after breakup the southwestern Japan Arc separated in the southeast direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the northwest direction. No significant volcanism was involved in initial rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.     

增强气候诊断及预测程序通用性的一种方法

针对现有气候统计诊断与预测程序在通用性方面的不足,以线性趋势估计的源程序为例,介绍了在微机平台上,利用Fortran 90的动态数组特性,通过增加参数控制文件增强该程序通用性的思路和方法,并利用V isualBasic语言对改进后的程序进行可视化设计,增强了程序的易用性。     

Spectral nudging sensitivity experiments in a regional climate model

In this study, the scale selective bias correction (SSBC) method described by Kanamitsu et al. (2010) is further examined by considering the full wind nudging and the vertically weighted damping coefficient. The 2001 June?CJuly?CAugust RSM simulation over a relatively large domain covering much of the Asian continent, the northern part of Australia, and the Indian and western Pacific oceans was the main focus. The full wind nudging shows wind fields closer to the driving global analysis. However, it leads to significantly distorted fields (e.g., temperature and geopotential height) aloft, accompanying excessive precipitation over the western Pacific. The gradual reduction of vorticity nudging from the model top to the ground surface improves rainfall patterns without a discernible distortion of large-scale fields. Further evaluation of a 10-year-summer simulation over East Asia confirmed that this revised SSBC method improves the monsoonal rainfall against the method of Kanamitsu et al. It is therefore concluded that vorticity nudging alleviates largescale errors by maintaining the near geostrophic balance between mass and winds. The reduction of this nudging factor in the lower troposphere allows the ageostrophic component of wind to develop as in nature, which leads to the improvement of precipitation.     

Decoupling of the East Asian summer monsoon and Indian summer monsoon between 20 and 17 ka

Marine Oxygen Isotope Stage (MIS) 2, with its profound environmental and climatic changes from before the last glacial maximum (LGM) to the last deglaciation, is an ideal period for understanding the evolution of the East Asian summer monsoon (EASM) and Indian summer monsoon (ISM), two Asian monsoon sub-systems. With 875 stable oxygen isotope ratios and 43 ²³⁰Th dates from stalagmites in Sanxing Cave, southwestern China, we construct and interpret a new, replicated, Asian summer monsoon (ASM) record covering 30.9–9.7 ka with decadal resolution. δ¹⁸O records from this site and other reported Chinese caves display similar long-term orbitally dominated trends and synchronous millennial-scale strong and weak monsoonal events associated with climate changes in high northern latitudes. Interestingly, Sanxing δ¹⁸O and Arabian Sea records show a weakening ISM from 22 to 17 ka, while the Hulu and Qingtian records from East and Central China express a 3-ka intensifying EASM from 20 to 17 ka. This decoupling between EASM and ISM may be due to different sensitivities of the two ASM sub-systems in response to internal feedback mechanisms associated with the complex geographical or land-ocean configurations.     

Evaluation of Hydraulic Properties of Aquitards Using Earthquake‐Triggered Groundwater Variation

The hydraulic properties of aquitards are not easily obtained because monitoring wells are usually installed in aquifers for groundwater resources management. Earthquake‐induced crust stress (strain) triggers groundwater level variations over a short period of time in a large area. These groundwater anomalies can be used to investigate aquifer systems. This study uses a poroelastic model to fit the postseismic variations of groundwater level triggered by the Chi‐Chi earthquake to evaluate the hydraulic properties of aquitards in the Jhoushuei River alluvial fan (JRAF), Taiwan. Six of the adopted eight wells with depths of 70 to 130 m showed good agreement with the recovery theory. The mean hydraulic conductivities (K) of the aquifers for the eight wells are 1.62 × 10^?4 to 9.06 × 10^?4 m/s, and the thicknesses are 18.8 to 46.1 m. The thicknesses of the aquitards are 11.3 to 42.0 m. Under the isotropic assumption for K, the estimated values of K for the aquitards are 3.0 × 10^?8 to 2.1 × 10^?6 m/s, corresponding to a silty medium. The results match the values obtained for the geological material of the drilling core and those reported in previous studies. The estimated values were combined with those given in previous studies to determine the distribution of K in the first two aquitards in the JRAF. The distribution patterns of the aquitards reflect the sedimentary environments and fit the geological material. The proposed technique can be used to evaluate the K value of aquitards using inverse methods. The inversion results can be used in hydrogeological analyses, contaminant modeling, and subsidence evaluation.     

用于地质科学计算的一种绘图方法

为了配合我院编制的“岩石化学计算系统”,我们采用RHT·BAS绘图程序,试验的效果较好,既洁简、又方便。对其它图件的整理、绘制也是一项较好的工具。