江西德兴中生代盆地红层时代研究

德兴盆地大体上是一个岩层向北倾斜的单斜式断陷盆地。盆地北缘最高层位过去认为是“早白垩世”石溪组或火把山群。本文根据采得的轮藻化石证实为晚白垩世晚期红层。看来江西一些大型中生代红盆地沉降较早(早白垩世晚期开始沉积);而德兴这样的小型红盆地则沉降较晓,直到晚白垩世晚期才接受沉积。     

震前声—振动与动物行为反应关系的反演研究(Ⅰ)

本文对不同介质的受击空气声(SABS)、界面固体声(SSBSB)和沙层固体声(SSBSS)进行了测量,并与某些动物的感觉特性相比较。脆硬介质(Ⅰ)的SABS的主峰频率和幅值都明显高于低硬介质(Ⅱ)和含断面的低硬介质(Ⅲ)。可见,震前宏观地声的音色和强度的地区差异和某些动物的听觉效应与局部地区的介质特性有关。冲击能量(SE)为3×10~5尔格时,介质Ⅰ的SSBSB和SSBSS可被鸽、猫和某些昆虫觉察到,但介质Ⅱ猫觉察不到,介质Ⅲ只有某些昆虫可觉察到。SE为1.6×10~6尔格时,介质Ⅱ和Ⅲ的SSBSB和SSBSS可被鸽、猫、鼠和某些昆虫觉察到。相当于某些强震前一级左右的小震能量传至地表衰减7个数量级所激起的SSBSB和SSBSS仍有可能被这些动物觉察到,并与局部地区的介质特性有关。     

第四纪气候旋回孢粉植被动态组合探讨

通过对中纬区完全孢粉植被动态组合规律的分析,可以推导出某一地区沉积剖面中第四纪冷暖气候旋回的孢粉植被动态组合,其方式是:冷期孢粉动态组合,以比该区更北(平原)或更高位(山地)的孢粉植被为中间层,其上下依次对称出现比中间层更南(平原)或更低位(山地)的孢粉植被组合;暖期孢粉植被动态组合,以比该区更南(平原)或更低位(山地)的孢粉植被为中间层,其上下依次对称出现比中间层更北(平原)或更高位(山地)孢粉植被组合。     

再论震积岩及震积不整合——以川西-滇西地区为例

震积岩是“灾变事件岩”的典型代表,震积岩一般由原地相的地震扰动层与上覆的滑来震积层组成,无论后者是否发育,震积不整合都是存在的。伸展构造环境下形成的区域性震积不整合,属于伸不整合,地震扰动层可以进一步分为软沉积及液化变形段,半固结变形的微褶皱和微断层段、脆性变形的震碎角砾岩段及韵律断层段等序列;群震型（多震旋回）剖面也可划分出出前震、主震、后震等序列。地震扰动序列对识别震积岩很关键,群震型剖面及化     

水平动载下饱和砂土地基液化区扩展

对一侧受沿深度分布的水平振动载荷时 ,半无限饱和砂土地基液化区域的扩展进行了数值分析。结果表明 :在水平振动载荷作用下 ,砂土地基液化区域从载荷端由近到远逐渐发展 ;随载荷强度和频率的增加 ,以及土体模量的减小 ,液化发展逐渐加快。在考虑的频率范围内 ,随着载荷频率的增加 ,土体表面的变形和土中的孔隙压力上升速度增加。     

Shear modulus and damping ratio of grouted sand

An experimental comparative study of three different grouted sands in terms of their effects on the values of two dynamic properties is presented. The dynamic properties studied are the shear modulus and the damping ratio which are determined with resonant column tests and cyclic triaxial tests. The behaviour of a pure Fontainebleau sand is compared with the behaviour of a Fontainebleau sand grouted with a silicate grout, a micro-fine cement grout and a mineral grout. The effects of the grouting treatment, the type of grout, the confining pressure, and the strains, on the shear modulus and the damping ratio are studied. The test results have shown that grouting improves the stiffness of the sand especially for small strains. Whatever the type of material, confining stress improves the shear modulus whereas it has a negligible effect on the damping ratio. When strain increases, the shear modulus decreases and the damping ratio increases.     

20世纪90年代以来机械防砂技术的新进展

防砂对于出砂油藏有着重要意义，防砂的成功与否直接关系到油气藏是否能够正常开发。随着新科技和新材料的不断发展和完善，机械防砂技术也获得了日新月异的进展。特别是20世纪90年代以来各种新的防砂技术在油田现场应用均取得了良好的效果。论述了20世纪90年代以来机械防砂技术的现状及发展趋势。     

Geochemistry and Genesis of the Pampean and Post-Pampean Formations (Late Pleistocene-Holocene), Central and Northern Argentina Pampas and Its Adjacent Region-An Approaching Case Study

Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional conformable horizontal regolithic mantle-rock bed derived from them (the Pampean and Post-Pampean Formations), were geochemically analyzed. The focus of this study is placed on the application of geochemical parameter and signature analyses related with the aforementioned geological units, which are of subcontinental extension into South America. The encountered results show an outstandingly similar geochemical behaviour between them. The main conclusion is that regolithic mantle-rock beds were derived from the littoral shallow marine mudstone (silty-argillaceous) beds. This is in oposition to previous aeolian processes proposed early in the 50's and later. These mudstone beds constitute important sections of the littoral shallow marine sequence beds (outcropping HST parasequence). Such regolitization proposed for the Pampean and Post-Pampean Formations predominantly developed in-situ during the Late Pleistocene and Holocene. The main erosional and mobilized agents were the surface free water (pluvial, fluvial and laminar water sheets) and vadose water. So, the wind flows and/or the immense air flow hurricanes are of insignificant sedimentological influence. Otherwise, there is not a proved appropiate sandy-silty reservoir for a reasonable support of the "aeolian hypothesis", as well as clear aeolian structures settled in the regolithic mantle-rock bed. In spite of these lines of equality textural-structural evidence, the geochemical values for both major elements and trace elements, demonstrate that the Miocene heterolithic marine succession was the mother rock of the overlying regolithic mantle-rock bed, which was formed as an in-situ mantle-rock bed.     

The causes of bedload pulses in a gravel channel: the implications of bedload grain‐size distributions

Unsteady bedload transport was measured in two c. 5 m wide anabranches of a gravel‐bed braided stream draining the Haut Glacier d'Arolla, Switzerland, during the 1998 and 1999 melt seasons. Bedload was directly sampled using 152 mm square Helley–Smith type samplers deployed from a portable measuring bridge, and independent transport rate estimates for the coarser size fractions were obtained from the dispersion of magnetically tagged tracer pebbles. Bedload transport time series show pulsing behaviour under both marginal (1998) and partial (1999) transport regimes. There are generally weak correlations between transport rates and shear stresses determined from velocity data recorded at the measuring bridge. Characteristic parameters of the bedload grain‐size distributions (D₅₀, D₈₄) are weakly correlated with transport rates. Analysis of full bedload grain‐size distributions reveals greater structure, with a tendency for transport to become less size selective at higher transport rates. The bedload time series show autoregressive behaviour but are dif?cult to distinguish by this method. State–space plots, and associated measures of time‐series separation, reveal the structure of the time series more clearly. The measured pulses have distinctly different time‐series characteristics from those modelled using a one‐dimensional sediment routing model in which bed shear stress and grain size are varied randomly. These results suggest a mechanism of pulse generation based on irregular low‐amplitude bedforms, that may be generated in‐channel or may represent the advection of material supplied by bank erosion events. Copyright © 2003 John Wiley & Sons, Ltd.