ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00464.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTA sequence of digitized observations on short‐normal resistivity determinations seems to show trend from higher to lower values. An appropriate statistical model proves it to have less range than expected on the distribution of its successive increments. On a two‐tailed statistical procedure for testing deviations from a random walk, the series tends towards ‘stasis’ rather than trend. The random walk model is shown to be plausible for the problem con

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00465.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTIt is useful to differentiate between thrust belts that are related to east(E)‐dipping or west(W)‐dipping subduction. More precisely, these either follow or resist the overall ‘eastward’ mantle flow detected by the hot‐spot reference frame. Because of the overall ‘westward’ drift of the lithosphere we find in E‐dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks. With W‐dipping subduction, however, we find that the basal decollement of the eastern plate is warped as well as subducted. Consequently thrust belts related to E‐ (or NE‐) dipping subduction show conspicuous structural and morphologic relief, involve deep crustal rocks, and are associated with shallow foredeeps. On the other hand, thrust belts related to W‐ (or SW‐) dipping subduction show relatively low structural and morphological relief, involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back‐arc extension. The accretionary wedge‐foredeep‐back‐arc basin association is visualized as an overall eastward propagating tectonic wave. The accretionary wedge forms in the frontal parts and generally below sea‐level. This is followed by forward migrating extension that cuts the earlier accretionary wedge. Typically such a system occurs in the context of overall W‐dipping subduction and is characterized by an arcuate shape (e.g. Carpathians, Apennines, Barbados, etc.). Along the branches of the arc external transpression and internal transtension co‐exist but with different sense (i.e. sinistral transpression contrasting with dextral transtension).We also observe that with W‐dipping subduction the tangent to a pre‐ deformation marker is descending into the foredeep at an angle in the range of 1–10° while with E‐(or NE‐)dipping subduction the same marker would rise towards the hinterland with typical angles of about 5–10°.Foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to E‐(or NE‐)dipping subduction and by the roll‐back of the subduction hinge in accretionary wedges due to W‐dipping subduction. Subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different, providing different P‐T‐t paths in the two geodynamic realms. The present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing th

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00466.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTMicrotectonic study of brittle structures in the József Hill Cave, Budapest, highlights the connection between different phases of fracturing and cave formation. E‐W trending dextral faults (second order Riedels) and NW‐SE oriented tension fractures developed in a ENE‐WSW trending dextral shear zone as a result of WNW‐ESE directed compression. Ascending thermal water dissolved cave galleries and created barite veins along these fractures. The first stage of cave formation as inferred from timing of fracturation from the regional stress field was Oligocene‐Early Miocene. Between the Middle Miocene and Quaternary new N‐S to NE‐SW trending normal faults were formed by ESE‐WNW extension. Pleistocene differential uplift resulted in the reactivation and enlarging of fault zones, dominantly the E‐W trending older Riedels. These recent tectonic events enhanced the originalen echelongeometry of the ol

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00467.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe stibnite ore deposits of the French Palaeozoic basement are spatially related to major Late Variscan strike‐slip faults. They occur as small discontinuous veins mostly hosted in epizonal or catazonal siliciclastics. Stibnite crystallizes in the final stage of a polymetallic paragenesis from an antimony‐bearing solution, which deposits a first discrete Fe‐As assemblage at 300–400°C and 0.5–0.8 Kbar. Experimental data have shown that antimony solubility drastically decreases on cooling. Characterization of the Late Variscan antimony‐bearing fluids enables us to predict the temperature range ‐ 270/150°C ‐ under which stibnite was precipitated. Since the latter coincides with the fluid inclusion homogenization temperature range, the pressure at which stibnite crystallized can be estimated from vapour pressure data to have been around 0.1 Kbar.Extensional brittle shear zones, developed at the end of the Late Variscan orogeny (probably at the Westphalian/Stephanian boundary), drained the hydrothermal fluids near to the surface (c.1000 m ?) reaching the critical P‐T conditions for stibn

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00468.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00469.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00470.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTMicropalaeontological, microscopic and mineralogical investigations of the ductily deformed and greenschist‐facies metamorphic Hochstegen Marble in the Tauern Window shed new light on its stratigraphy and fades.New radiolarian and sponge spicule discoveries have been made in cherty limestone marbles. They confirm previous age assignments and permit for the first time a more exact micropalaeontological age determination ofearly Tithonianfor the upper parts of the marble. Forty morphotypes of radiolarians could be distinguished; in one sample a Fisher diversity index of 6 is reached indicating deeper marine conditions. The spicule fauna is also diverse and shows affinity to the S‐German Malm. In respect to all the data it can be presumed that carbonate sedimentation of the Hochstegen Marble took place in a deeper marine environment at the southern margin of the European continent (Helvetic realm) during the whole Late Juras

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00471.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTUntil recently, only fossils of Caradoc to Carboniferous age have been reported from the Northern Greywacke Zone/Eastern Alps. New medium‐preserved and diversified acritarch assemblages from the Lower Wildschönau Formation indicate a Lower Ordovician (Tremadoc and Arenig) age. These fossil spectra define a well‐constrained time interval for a lower section of the Northern Greywacke Zone for the first

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00472.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTStatistical analysis of mainly mid to deep‐shelf Ordovician brachiopod faunas from localities within and marginal to the Appalachian‐ Caledonian Orogen reveals biogeographical patterns not entirely consistent with those presumed for the progressive orthogonal closure of the Iapetus Ocean. Correspondence analysis of faunas of late Arenig‐early Llanvirn, late Llandeilo‐earliest Caradoc and late Ashgill age emphasize the importance of marginal and island faunas, the role of regressions and transgressions on faunal distributions and the effects of climatic change in the definition of biogeographical trends during the Ord

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1992.tb00473.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY