ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00627.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00628.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe last 10–15 years have produced a considerable amount of research into the geological disposal of radioactive wastes. This has had some very beneficial spin‐offs for the geosciences. There are, however, a number of areas where it is difficult for earth scientists to provide quantitative information required for the types of long‐term safety assessment being performed at present. With the likely increased stringency with which we may begin to treat other industrial wastes, much is to be learned from the radioactive waste experience. This article reviews some of the geological issues in constraining long‐term predictions, discusses how geological data are used, and questions exactly what it is that we are trying to achieve in the management of these wastes and in the regulations concerning their d

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00629.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThere are considerable, well‐recognized difficulties involved in the investigation of very low permeability rocks by conventional measurements of water potentials and spatial distribution of hydrological parameters such as permeability and effective porosity. Therefore, most studies of predictive behaviour are based on models which, when unconstrained by data, are often worse than no model at all. Geochemistry and environmental isotope geochemistry are techniques well suited for hydrological investigations of potential sites of nuclear waste isolation and for constraining predictive models.Stable isotopes constitutive of the water molecule (2H and18O) may give information on the origin of the water, especially2H which is practically uninvolved in isotope exchange with rock‐forming minerals. Variations in stable isotope contents can be related to palaeohydrological and palaeoclimatic conditions whereas3H is indicative of recent recharge.The13C content of dissolved carbon is related to its origin(s) and the14C activity gives a time‐scale. However, the initial carbon isotope contents can be modified by various diagenetic effects such as precipitation/dissolution of secondary calcite and oxidation of reduced carbon. The heavy isotope content of the Total Dissolved Inorganic Carbon (TDIC) cannot be interpreted without a detailed knowledge of the carbon chemistry and of the mineralogy and isotope contents of secondary carbonates. Species of Dissolved Organic Carbon (DOC), with high molecular weights (HMW) can generally be attributed to soil derived compounds. Their14C content may be measured by AMS (Accelerator Mass Spectrometry) thus providing an estimate of the time elapsed since recharge took place.Chlorine‐36 is an interesting potential tool for dating old ground waters because of its long half‐life (301 kyr) and its hydrophilic behaviour. It can be also producedin situin significant amount if the rocks are rich (some tens of ppm) in U and Th. In such cases, this time dependent build‐up provides a more systematic radiochronometer of CI‐residence time in the rock than the decay of cosmic input36CI, provided no Cl‐is leached from the rock.The isotopic composition of aqueous sulphur compounds depends on their origin and on their diagenetic evolution. The redox reactions of SO2‐4reduction or of S2‐oxidation are marked by strong isotope effects especially when generated by bacteria. Sulphate reduction by organic matter is a potential source of dissolved inorganic carbon and may thus interfere with14C age interpretations.After discussion of the possible age and origin of waters and solutes, some scenarios of evolution of local and regional palaeohydrological conditions are proposed.Examples are given with special emphasis on detailed results from the Fennoscanian shield (Stripa project), and from n

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00630.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTIn the past two decades, several publications have been presented concerning the recent and active fault geometry, kinematics and geodynamics of the Aegean Region and particularly of the northern sector. Data and results are often contradictory and because of the complexity of the area most hypotheses and models should be considered carefully.The right‐lateral movement of the North Anatolia Fault continues into some branches of the North Aegean fault system. There, strike‐slip motion along NE–SW trending faults coexists with dip‐slip E–W trending faults in the frame of an extensional regime related to N–S crustal stretching.If we take into account the geodynamic environment of the region, several mechanical problems arise. To the east, the Aegean is compressed by the westward convergence of Anatolia, while to the south and west along the Hellenic Arc, a hemiradial compression occurs due to subduction. Although the North Anatolia–North Aegean Trough fault system resembles a restraining bend, the whole area is in fact affected by pure extension and local transtension, along NE–SW trending structures. Accordingly, the major paradox of the area and especially in the western sector (fault termination?) is the occurrence of extension where compression should regionally, or at least local

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00631.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTA combined seismic and gravimetric interpretation in the Northern Apennines area (Italy) is presented. To the knowledge of the authors, this is one of the few attempts to apply tomographic methodology to a seismic refraction profile. This procedure, together with the classical interpretation for defining lower reflectors, led to the formulation of quite an accurate model of the upper crust. A gravity analysis was performed concurrently taking into account the seismic results at different depths which correspond to different frequency domains in the gravity signal. While the medium‐ and high‐frequency patterns have been solved by trial‐and‐error, the regional trend has been modelled applying the collocation procedure to the gravi

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00632.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe 1356 Basel earthquake was the strongest event to have shaken NW Europe in the last thousand years. The peculiar location of this historical event makes it possible to relate it to normal faulting along the edges of the Rhine Graben, as well as to reverse faulting along the Jura frontal thrust or to fault reactivation within the Hercynian basement. Alternate hypotheses are discussed and their implications compared taking into account available structural data and results of the morphotectonic study performed in the epicentral area. This study combines field observations with the analysis of SPOT satellite imagery, aerial photographs, and detailed topography. It is concluded that the Basel earthquake most probably reactivated a basement fault (reverse or wrench fault) beneath the shallow‐depth aseismic detachment that underlies the Jura Mountain

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00633.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe nodular limestones and red marls of the Ankara region, deposited during the early to middle Jurassic, show similar palaeontological and sedimentological characteristics to those of the red nodular limestones form the Northern Alps (Adnet limestones) and from the Southern Alps (Ammonitico Rosso).The nodular limestones appear to be hardground breccias drowned into the red marly limestones due to the instability of the bottom. The association of sponge spicules, crinoid fragments, small ostracods, benthic foraminifers, shell debris and common micrite matrix suggests a subtidal environment. The subsequent formation of red marly limestones consists of the partial dissolution of the shells; this suggests that a low sedimentation rate and/or sedimentological breaks took place during the precipitation of the ammonite‐bearing marls.The nodular limestones (hardground breccias) and the Ammonitico Rosso‐type facies of the Ankara Jurassic succession were formed in a deeper subtidal environment and/or deeper shelf extending into the basin. The hardground layers drowned into the Ammonitico rosso were likely formed on a local carbonate shelf, that deepened increasingly through the early to middle Jurassic. Development of a local submarine clastic fan within the carbonate succession of the Ankara Jurassic basin indicates an irregular bottom topography induced by the syn‐sedimentary f

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00634.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTRegional mapping of a section across the Eastern Ghats Mobile Belt (EGMB) north of the Godavari graben in Eastern Peninsular India by using Landsat Thematic Mapper data enables recognition of a number of shear zones, lineaments, and structural domes and basins. A conspicuous megashear occurs at the western boundary of the granulite facies rocks of the EGMB adjacent to the Archean granite‐greenstone craton. The confinement of a suite of alkaline igneous rocks to this shear zone is a notable feature. The strike extensions of this shear belt extend through to the Elchuru alkaline complex, Prakasam District, Andhra Pradesh, and the syenite plutons of Koraput district, Orissa. The contrasting lithologies, metamorphism and structural history on either side of the shear zone suggests that it might be a Precambrian suture zone.The mesoscopic structural features in the EGMB include prominent foliation with moderate to steep dips, folds, faults/shears, S‐C fabrics, pinch and swell structures and other linear fabric elements. These observations favour the consideration of drastic crustal shortening and thickening and a complex deformational sequence. The major rock units in this part of EGMB comprise garnetiferous sillimanite gneisses, quartzites and calc‐granulites forming the khondalitic suite of rocks and a wide variety of charnockitic rocks. The contact of the two rock units is generally sheared and often migmatised.The structural fabric suggests two major tectonic events: an essentially horizontal tectonic regime resulting in thrust systems and associated structures, subsequently followed by strike‐slip tectonics characterized by high shear strains. Features such as westward‐verging thrusts, large‐scale recumbent folds, major shear zones, structural domes and basins, indications of tectonic crustal shortening, extensive calc‐alkali magmatism and widespread migmatization in the region are attributed to collisional processes during Proterozoic times. The spatial disposition of the EGMB and its linkage with the distribution of similar rock units during the late Precambrian time in a global tectonic scenario

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00635.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe Nepal region, between the Ganges plain and the Tibetan Plateau, shows the great effects of the orogenetic deformation which started between 40 and 55 Ma, following the collision between the Indian and Asiatic continental plates. Today the Himalayan chain and the Tibetan plateau are some of the best manifestations of the collision process.Data from a geodetic network in Eastern Nepal were employed to study the motion of the crust in this recently evolved area. The data were collected by means of the Global Positioning System; this geodetic space technique can achieve a centimetric resolution in coordinate definition and baseline computation for observation sites, even those located at long distances away and it provides a powerful new tool for the comprehension of the dynamics of active tectonic regions.

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00636.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY