Syn‐rift sequence development in a fault‐controlled embayment (Early Permian Irwin River Coal Measures,Northern Perth Basin,Western Australia)

Stratigraphic patterns and sequence development in tectonically active extensional basins remain poorly documented in comparison with passive‐margin settings. Rift basin fills are generally characterized by coarsening‐upward trends in response to the rapid creation of accommodation by extensional faulting, and the progressive filling of graben during more quiescent periods. The Early Permian Irwin River Coal Measures in the Northern Perth Basin (Western Australia) record a complex stratigraphic arrangement of conglomerate, sandstone, mudstone and coal, and have been attributed to delta plain depositional environments that developed in a cool–temperate climatic setting during syn‐rift activity. Sedimentary analysis of outcrop and core data from the fault‐bounded Irwin Terrace is used to distinguish nine facies associations reflecting deposition in braided rivers, fixed‐anastomosed channel belts, tide‐influenced coastal environments and storm‐affected distal bays. The broader depositional system is interpreted as a morphologically asymmetrical tide‐dominated embayment with a fluvial and wave influence. The stratigraphic architecture of the Irwin River Coal Measures was strongly influenced by the evolving rift basin margin. Fault reactivation of the major basin‐bounding Darling Fault in the early syn‐rift phase caused footwall uplift and the inception of transverse palaeo‐valleys occupied by braided fluvial systems. Fault block subsidence during the subsequent balanced, backstepping and drowning phases resulted in a dominantly retrogradational stacking pattern indicating progressive flooding of marginal‐marine areas and culminating in deposition of distal marine elements. In the active rift basin, it is proposed that preservation of a shallow‐marine syn‐rift sequence was promoted by the geomorphological confinement of the embayed system increasing tidal current acceleration and hampering transgressive ravinement. The proposed sequence model demonstrates that transgressive successions can develop in the early syn‐rift phase in response to footwall uplift and tectonic subsidence. The syn‐rift sequence recording the filling of an embayment on a rift basin margin may be applied in similar tectonic and/or depositional contexts worldwide.     

Facies pattern of the middle Permian Barren Measures Formation, Jharia basin, India: The sedimentary response to basin tectonics

In the Lower Gondwana succession of the Jharia basin of eastern India, the Barren Measures Formation is characterized by the cyclic disposition of fine-grained lacustrine deposits and relatively coarse-grained fluvial deposits. The cyclic variation in the rate of coarse clastic input is attributed to the sedimentary response to basin tectonics. The sandstone-shale alternations of the Barren Measures succession can be correlated with the tectonic cyclothems developed on the hangingwall dip-slope and adjoining trough in a continental half-graben setting. Enhancement of the gradient of the hangingwall dip-slope during reactivation of the basin margin faults led to progradation of the existing fluvial system towards the half-graben trough and deposition of the coarser clastics on the fine-grained lacustrine deposits of the trough. Peneplanation of the hangingwall slope and slow increase in the lake level caused lacustrine transgression and retrogration of the fluvial system on the hangingwall block. The fluvial sediments were onlapped by the fine-grained lacustrine deposits. Episodic rejuvenation of the basin margin faults thus caused development of tectonic cyclothem on the hangingwall block. The paleocurrent pattern indicates that a persistent northward paleoslope was maintained during Barren Measures sedimentation. The inferred depositional settings were much more extensive than the present limit of the outcrop. The faults, presently defining the northern limit of the Barren Measures Formation, were possibly emplaced after Barren Measures sedimentation. The final movement along these fault planes caused preservation of the downthrown hangingwall block and the Barren Measures sediments on the footwall block were eroded during subsequent denudation. The Southern Boundary Fault came into existence after the deposition of the Barren Measures sediments.     

钻孔灌注断桩事故产生原因及处理措施

简要介绍在钻孔灌注桩施工中发生的断桩事故的原因和处理措施。     

A newly-discovered coal measures marine band in billinge beacon quarry,lancashire, and its stratigraphical significance

A thin band yielding conodonts and Foraminifera and therefore demonstrably marine, has been found in mudstone lying immediately above the uppermost coal horizon in Billinge Beacon Quarry. The existence of this newly recognized horizon, which is very likely to be the Langley Marine Band at the top of the Lenisulcata Chronozone, much strengthens the correlation of the Billinge Beacon sandstones with the regionally developed Crutchman Sandstone. An alternative correlation of the Billinge Beacon sandstones with the Dyneley Knoll Flags of Burnley, which was recently proposed by F. M. Broadhurst, is not supported by the new evidence, nor by the evidence of boreholes, since it appears that the Dyneley Knoll Flags die out some distance to the north of Billinge.     

世寿街滑坡发生机理与防治对策

世寿街滑坡位于沱江下游河口段右岸。形成的主要因素是斜坡体内广布极易滑的粉质粘性土层、江水周期性的浸泡、冲刷、以及人为加载和生产、生活活动。呈现牵引推动的复合发生机理。由于滑坡区为综合房地产开发之用 ,滑坡防治不仅要考虑滑坡本身的稳定 ,而且还要考虑滑体上各种建筑物的安全运行。采取了主要因素控制法。     

大厂铜坑矿区鲁塘尾矿库地质灾害危险性评估

鲁塘尾矿库为单斜构造,由石炭系、二叠系灰岩组成。崩塌、滑坡地质灾害危害小,岩溶、地面塌陷及地下水污染危害性中等。对各种灾害提出针对性防治措施。     

地下水科学调控与增效利用

地下水参与自然界的水分循环,同时又独立参与自身的补给、径流、排泄小循环,具有再生性.只要把握地下水资源的客观规律,充分利用地下含水空间和多年调节功能,准确调控地下水资源开发利用的尺度,地下水将会发挥更大的效益.从地下水循环机理的层面上,阐明地下水超采区是动态的,是某一时期的产物,阐述地下水科学调控的合理水位标限,提出了增效利用的措施.     

昆明滇池盆地新近纪象类化石

记述滇池盆地含煤层中首次发现的上新世剑齿象化石,包括脊棱齿象属的一个新种昆明脊棱齿象(Stegolophodon kunm ingensissp..nov.)、似元谋剑齿象(Stegodonaff.yuan-m ouensis)、玉溪剑齿象、师氏剑齿象等。这一剑齿象化石组合的发现,对研究新生代象类和滇池盆地的演化史,重新划分盆地煤系地层具有重要意义。     

数字观测仪器机房保温措施

介绍了朝阳地震台根据公皋井的实际情况，按照《规范》对前兆数字仪器设备工作环境的要求所采取的机房防寒保温的方法和措施。