Hydraulic properties and scale effects investigation in regional rock aquifers,south-western Quebec,Canada

This paper reports on the characterization of hydraulic properties of regional rock aquifers carried out within a groundwater resources assessment project in the St. Lawrence Lowlands of south-western Quebec. To understand the aquifer behavior at both the fracture level and at field scale, hydraulic investigations were carried out using various aquifer tests. The groundwater flow at the local scale is controlled mostly by the fracture system. Results of the constant-head injection tests show a weak decreasing trend of hydraulic conductivity with depth indicating that a major part of the groundwater flow occurs in the first meters of the rock sequence. At the regional scale, the equivalent porous media approach is applicable. The hydraulic conductivity measurements were correlated to the scale of the aquifer tests expressed with the investigated aquifer volume. A simple interpolation procedure for the hydraulic conductivity field was developed based on the distance between field measurements and the tested aquifer volumes. The regional distribution of the hydraulic conductivity for the major fractured aquifer units indicates that dolostone is the most permeable whereas sandstone and crystalline rocks are the least permeable units.

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Resumen Este artículo trata de la caracterización de las propiedades hidráulicas en acuíferos regionales rocosos, la cual se llevó a cabo dentro del proyecto de evaluación de los recursos de agua subterránea en St. Lawrence Lowlands al suroeste de Quebec. Para entender el comportamiento del acuífero tanto a nivel de fractura como a escala del campo, se ejecutaron investigaciones hidráulicas usando varias pruebas de acuífero. El flujo del agua subterránea a escala local está controlado principalmente por el sistema de fracturas. Los resultados de las pruebas de inyección con cabeza constante muestran una tendencia decreciente débil de la conductividad hidráulica con la profundidad, indicando que la mayor parte del flujo de agua subterránea sucede en los primeros metros de la secuencia rocosa. A escala regional se puede aplicar la aproximación equivalente de medios porosos. Las medidas de la conductividad hidrálica fueron comparadas con la escala de las pruebas del acuífero, expresadas con el volumen investigado del acuífero. Se desarrolló un proceso de interpolación simple para la conductividad hidráulica de campo, con base en la distancia entre las medidas de campo y los volúmenes probados del acuífero. La distribución regional de la conductividad hidráulica, para las unidades acuíferas fracturadas mayores, indica que la dolomita es más permeable mientras que la arenisca y las rocas cristalinas son las unidades menos permeables.

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Résumé Larticle présente les propriétés hydrauliques dun aquifère régional rocheux qui ont été mesurées dans le cadre dun projet concernant lestimation de la ressource en eau de la plaine de St. Lawrence située dans la partie sud-ouest de Quebec. Affin de comprendre le comportement de l› aquifère tant à l› échelle de fracture qu› à l› échelle régionale on a mené des investigations hydrauliques en utilisant des essais differents. À l› échelle locale lécoulement est déterminé en principal par le système des fractures. Les résultats des essais dinjection au niveau constant ont montré une tendence de décroissance de la conductivité hydraulique avec la profondeur ce qui indique que l› écoulement ait lieu en principal dans les premiers mètres de la structure rocheuse. À l› échelle règionale on peut appliquer lapproche de milieux poreux equivalent. Les mesures de conductivité hydraulique ont été corrélées avec l› échelle des essais de pompage exprimée en termes de volume investigué de l› aquifère. On a mis au point une méthode simple dinterpolation pour le champ de la conductivité hydraulique basée sur la distance entre les essais in situ et les volume investigués de l› aquifère. La distribution règionale de la conductivité hydraulique montre que pour la majorité des unités de roche fracturé les plus perméable sont les roches dolomitiques alors que les grés et les roches cristalines presentent la plus faible perméabilité.

     

Geochemical characteristics of sediments from the COMRA registered pioneer area (CRPA), equatorial northeastern Pacific Ocean

I\TRODUcrIO\Most substances that enter the oceans are ultimately kept as sediments. ffefore settingdOwn, they experienced vdrious complex biological and chebocal cycles and interactions, whichinvolve sorne substances more than others. The interactlons continue after deposition. Sedl-ments do not lie passive]y on the sea--floor until they are buried: deeP--sea animals disturb thesediments as they forage fOr fdri, and some sediments may experience erosion and resuspensionby bottom currents. …     

台湾海峡西部海域第四纪晚期沉积速率的变化

本文利用台湾海峡西部海域第四纪晚期沉积物的沉积速率，研究了沉积速率随环境和年代不同而变化的规律，指出第四纪晚近时期沉积物沉积速率上升的趋势和原因，说明人类的活动，尤其是不合理的开发是引起学积物沉积速率与日俱增的重要原因，应当引起足够的重视。     

Vertical Variations of Core Sound Velocity: Evidence of Paleooceanographic History Since the Pleistocene Epoch

The vertical variations in the borehole core sound velocity (Cp) of the submarine sediments are related to the events of marine transgression and regression in the geologic history. This article establishes the vertical variation of Cp curve for the borehole sound velocity in the northern South China Sea continental shelf and the East China Sea continental shelf, thus providing evidence for revealing at least (3) sedimentary cycle events of marine transgression and regression occurring in the west Pacific marginal sea since the Pleistocene Epoch. The sound velocity of marine sediments brought in the course of marine transgression is lower (1450-1510 m/s) while that of continental sediments formed in the course of marine regression is higher (1650-1720 m/s).     

滦河现代三角洲演变的几何学特征

滦河三角洲位于渤海湾北岸，是1915年滦河改造进入现今位置入海之后形成的一个典型的扇状三角洲，在三角洲发育过程中，人类河流水利工程对其演变产生了巨大的影响，三角洲大致经历了堆积前展、相对稳定和侵蚀衰亡3个阶段，不同阶段扇状三角洲表现出不同的几何学特征。作者在野外调查基础上，以1932年以来不同时期地形图和TM遥感数据为依据，对三角洲演变的几何学特征进行了研究，从而为认识扇状三角洲的发育阶段和三角洲海岸演化的预测研究提供了一种数学方法。     

胜利油区原油和沉积岩中稀土元素组成特征及其意义

文中利用稀土元素在原油运移中良好的续承性,初步探讨了在济阳坳陷内的东营凹陷和沾化凹陷原油中稀土元素的赋存特征以及它们的来源方式,并指出两凹陷不同的物源性质是造成原油稀土赋存特征差异的主要原因。     

黄河、长江和珠江三角洲近代沉积物的沉积化学特征

黄河、长江和珠江是我国直接入海的三条最大河流，流域面积之和占我国直接入海主要河流流域面积的90%。三大河三角洲近代沉积物的沉积化学特点是：黄河三角洲CaO含量高，而A12O3、TiO2和有机质含量均较低；长江三角洲的MgO、MnO含量略高；珠江三角洲的Fe2O3、TiO3含量高，CaO含量低。这种沉积化学特征的差别，是由于沉积化学成分受地带性的生物气候及河口地球化学环境制约的结果。     

The Laptev Sea Rift

In north-eastern Siberia the active mid-ocean Gakkel Ridge interacts with the continental shelf of the Laptev Sea. Extension has affected the shelf since at least the Early Tertiary and has resulted in the formation of a complex horst and graben system. We present new seismic data from the Laptev Sea including deep seismic soundings.The most prominent rift basin is the Ust' Lena Rift with a minimum E–W width of 300 km at latitude 75°N and a Cenozoic infill up to 13 km in thickness. The asymmetric shape of the basin and conclusive evidence for a detachment imply a simple-shear geometry. The suggested rift model combines a ramp and flat geometry for the detachment with ductile stretching beneath the detachment. A major west-dipping, hingeline, listric fault separates the Ust' Lena Rift from the Laptev Horst.The 100–150 km wide Laptev Horst is subdivided into three units by narrow rift grabens. Another prominent rift graben is the Anisin Basin, which is located in the northern shelf area.Though the Laptev Sea Rift formed in interaction with an active mid-oceanic ridge, there are indications that the Laptev Sea rift is of the ‘passive rift’ type. The rift was developed east of a SW–NE trending transfer zone which links the Gakkel Ridge to the Laptev Sea Rift.     

南黄海灵山岛附近残留沉积及其沉积环境分析

在灵山岛东南水深大于25m海域的表层,发现大片砂砾、砾砂类沉积。根据对此类沉积物特征、成熟度、粒度分布、概率累积曲线、粒度参数、贝壳种类和沉积物展布特征的分析,发现此类沉积与现今海洋动力环境和海相沉积特征不相符合,推知此类沉积可能为残留沉积,其沉积环境为陆相洪积扇沉积。     

台西南盆地晚新生代地质演化分析

通过对构造沉降、断裂活动、岩浆活动、构造应力场等分析，认为台西南盆地晚新生代地质演化存在两个旋回，即渐新世－中中新世受南海扩张控制、陆缘主动裂陷－沉降旋回和晚中新世－第四纪受台湾弧－陆碰撞影响、陆缘被动拉张－活化旋回。