Tectonic Dislocations Research Articles

Spectral features of elastic vibrations close to tectonic dislocations in coal seams

Spectral features of elastic vibrations close to tectonic dislocations in coal seams

Die Altpleistozänen Terrassen Der Mittelmosel Überlegungen Zur ”Horizontalkonstanz” Der Terrassen Der ”Rheinischen Hochscholle”

Revision of the Old-Pleistocene river terraces in the Middel-Moselle-Area verified the results of Kremer (1954) refuting the objections by Birkenhauer (1971). Corresponding to the findings in the Middle-Rhine-Area (Bibus & Semmel 1977) five, sometimes six Pleistocene river terraces which show neither tectonic dislocations nor a distinct longitudinal gradient can be traced above the narrow Moselle-Valley. Differences in the altitude of equivalent terraces of the Middle-Moselle-Area (e.g. t4 = ± 265 m NN) and the Middle-Rhine-Area (tR4 = ± 220 m NN) and the almost rectangular course of the both rivers indicates that the explanation for the ”missing gradient” (Bibus and Semmel, 1977, Birkenhauer, 1979) cannot only be found by a stronger postsedimentary uplift in the northern area of the ”Rhenish shield”. Die Neubearbeitung der altpleistozänen Terrassen der Mittelmosel bestätigte entgegen den Einwänden von Birkenhauer (1971) die Terrassengliederung nach Kremer (1954). Analog den Befunden im Mittelrheingebiet (Bibus & Semmel 1977) treten oberhalb des Engtales der Mosel fünf, z.T. sechs pleistozäne Terrassen auf, die weder tektonische Verstellungen noch ein deutliches Gefälle erkennen lassen. Differenzen in der absoluten Höhenlage der äquivalenten Niveaus von Mittelmosel (z.B. t4 = ± 265 m NN) und Mittelrhein tR4 = ± 220 m NN) und der nahezu rechtwinklige Verlauf beider Flußsysteme zeigen, daß die Erklärung der ”Horizontalkonstanz” (Bibus and Semmel, 1977, Birkenhauer, 1979) nicht allein in einer Schrägstellung des ”Rheinischen Schildes” gefunden werden kann.

Space geological maps and their importance for mineragenic constructions

V.N. Bryukhanov and A.L. Stavtsev Ob ‘edinenie “Aerogeologia”, Ministry of Geology ofthe USSR, Moscow, USSR Space geological maps are now being constructed in the USSR. These maps present specific features of the Earth’s crust which are exhibited by topographic features identified from apace imagery. The maps depict only those elements which are identified on apace images. The geological interpretation of the elements is based upon known geological, geophysical, geochemical and geomorphological data. Space geological maps, like other geological maps, contain areal and linear information. Areal details of space geological maps correspond to mineral—structural complexes, i.e. rock types and associated tectonic dislocations. The mineral—structural complexes also include intrusive, volcanic and protrusive formations characterised by certain rock types and. shapes of bodies. Mineral—structural complexes are looked upon as whole indivisible features of the Earth’s crust which integrate material composition of rocks with their dislocations. It is these characteristics which determine peculiarities of photographic representation of areal objects on apace imagery. But if in folded regions the character of representation of mineral—atructuzal complexes on space images depends, prima—

Regional tectonics and sulphide ore localisation in Delhi-Aravalli belt, Rajasthan, India—Use of LANDSAT imagery

Interpretation of the LANDSAT imagery has brought to light several transverse and longitudinal tectonic dislocation zones in the Delhi-Aravalli belt. The multimetal sulphide deposits of Khetri, Pur-Banera and Zawar belts conform to longitudinal lineaments and exhibit little affinity towards transverse features. These observations are in conformity with the prevalent ideas of syngenetic-remobilized origin of these deposits and could be helpful in planning further exploration strategy.

Isotopic dating of the emplacement of the ultramafic masses in the Serrania de Ronda, Southern Spain

A Rb-Sr analysis of suites of samples from a small intrusion of cordierite-bearing alkali granite into the peridotite of the Sierra Bermeja (Serrania de Ronda) yields an age of 22± 4 Ma (λ = 1.42×10−11 a−1): Late Oligocene/Early Miocene. It is believed that the intrusion was derived from contact-anatectic melts produced along the hot ultramafic mass during and/or directly following its tangential, tectonic dislocation from a mantle diapir. Its age can thus be taken as dating the termination of the hot emplacement of the ultramafic masses. K-Ar dates of biotites and Rb-Sr dates of biotite/whole-rock pairs in contact-metamorphic wall rocks along the ultramafics mostly lie between 19.5 and 18.5 Ma. This probably indicates that about 19 Ma ago the contact-zones of the ultramafic masses had cooled down to the blocking temperature of biotite to Rb-Sr and K-Ar.

The zonal pattern of metamorphism in the Scottish Highlands and the displacement along the Great Glen Fault: discussion of paper by G. A. Chinner

SummaryThe zonal pattern of metamorphism in the Scottish Highlandsis more complex than that suggested by Chinner. It has been disrupted by major tectonic dislocations and cannot be interpreted as a simple thermal anticline. Retrogression and inversion of zones seen in NW Scotland may resulteither from structural perturbation or the interference effects of superimposed metamorphism. A sinistral displacement of the Great Glen Fault still seems to match the metamorphic patterns in the opposing blocks, even if allowance is made for a major downthrow to the SE.

Correlation of metamorphic fabrics and the age of Lewisian metasediments near Loch Maree

Synopsis Various views have been expressed concerning the age of the Lewisian metasediments and associated basites (Gleann Tulacha metasediments and Beinn Airigh Charr basite) near Loch Maree. Interpretation of their chronological status is complicated by:– (i) the absence of Scourie dykes intrusive in the metasediment-basite association. (ii) tectonic dislocation between the metasediment-basite outcrops and the surrounding gneissose complex. Fabric analysis, with particular emphasis on shape-fabric anisotropy, shows that two NW–SE foliation-producing events in the gneissose complex were separated by Scourie-dyke emplacement. These foliations (coded S5 and S6) are respectively correlated with Late Scourian (Inverian) and Early Laxfordian structures elsewhere in the Lewisian. Fabric and structural sequences in the metasediment-basite association are compared with those of the gneisses. It is concluded that Late Scourian metamorphism and deformation have affected the metasediments and associated basites. Similar findings were obtained from a narrow tract of metasediments and basites near Gruinard Bay (the Gruinard metasediment-basite association). These Gruinard rocks are probably the stratigraphical equivalents of the Loch Maree Group and contain S5 foliation cut by members of the Scourie-dyke swarm. Absence of high grade Early Scourian (Badcallian) fabrics and structures in both the Gruinard and Loch Maree metasediment-basite associations is considered to be indicative of their post-Badcallian origin. It is thus concluded that the metasediments near Loch Maree represent a post-Badcallian supracrustal cover which experienced penetrative metamorphism and deformation prior to Scourie-dyke emplacement.

The sillimanite zones of the Huntly-Portsoy area in the north-east Dalradian, Scotland

SummaryThe distribution of andalusite, kyanite and sillimanite in an important part of the NE Dalradian is mapped. Sillimanite represents a late episode overprinted on the regional Andalusite and Kyanite Zones. The spatial distribution of sillimanite confirms that the heat source for the sillimanite-grade metamorphism in this area was the Newer (or Younger) Basic magma. The sillimanitic aureole of the Newer Basic intrusives is divisible into a Sillimanite Zone and a higher-grade Sillimanite—potash feldspar Zone. Relict andalusite is common in the Sillimanite Zone. Coarse muscovite replacing other minerals is primary in both zones, and should not be confused with late retrograde effects. Electron-probe analytical data on the Sillimanite–potash feldspar zone paragenesis of muscovite are presented. In this, its type area, the so-called ‘Boyne Line’ does not exist; the concept of such a tectonic dislocation arose through misinterpretation of the metamorphic effects.

Note sur la geologie des environs d'Arcy-sur-Cure et de Saint-More (Yonne)

Abstract The abrupt change in dip of Rauracian (Jurassic) deposits in the vicinity of Arcy-sur-Cure and Saint-More in Yonne, France, is not due to tectonic dislocation but to differences in the dip of the terminal zone of a Rauracian reef and that of the surrounding marls.

Sur les accidents tectoniques de la bordure occidentale du bassin de Paris et, en particulier, sur ceux du Perche et du Haut-Maine

Abstract Discusses the structural relations and orientation of tectonic dislocations along the western border of the Paris basin, France, with special reference to deformation in the Perche-upper Maine region.

Low Levels of the Mediterranean Sea during the Pleistocene Glaciation

The difficulties which arise in the course of a study of the oscillations of Pleistocene shore-lines are well known (see Daly 1934, Wright 1937). Epeirogenic movements and tectonic dislocations and flexures on the one hand, and eustatic and isostatic oscillations, which are more directly connected with glacial and interglacial periods, on the other, have affected the positions of Pleistocene shore-lines around all oceans. Each littoral region has reacted differently to these factors, according to the character of its structure, the degree of its tectonic stability, and its geographical position in relation to the inlandeis . Even the traces of eustatic oscillations of sea-level, which, undisturbed, would show a constant elevation on all littoral regions, are actually found at different heights above the present sea-level, because tectonic and isostatic movements have interfered with their formation and sometimes altered their original position. In the Mediterranean, the shores of which have not undergone isostatic movements comparable with those of northern Europe, the Pleistocene shore-lines can be traced at levels which appear to have been determined by local eustatic and tectonic oscillations. Issel, Gignoux, de Lamothe, Depéret, and others have pointed out the approximate constancy, right round the Mediterranean, of the levels of some of these shore-lines. Depéret has even correlated them with the Atlantic shore-lines of western Europe. Some of these investigations have been based only on morphological evidence and altimetry; in others, these methods have been supplemented by palaeontological and stratigraphical research. Only the latter class can furnish a reliable basis for the

Problems in the geologic interpretations of the Earth's major magnetic anomalies

The writer assumes that the magnetic field along the Earth's surface would correspond mainly to the field of a magnetized sphere and that the magnetic axis of this sphere would coincide with the rotational axis, if it were not for the varying chemism and the tectonic dislocation within the magma‐zone and rock‐zone of the Earth. From the total Earth's magnetic field is deducted an inner portion. The remaining field contains major, continental, regional, and local anomalies, which are classified first theoretically and second empirically. The empirical major anomalies are represented in the form of magnetic vectors. The main high and low magnetic trends as indicated by these vectors show a striking parallelism with the main trends of the alpine orogeny. The small secular variations of the declination of the circum‐Pacific stations as compared with circum‐Atlantic stations are explained by the general conception that the basement of the Pacific is more stable than the basement of the Atlantic.