Showing papers in "Geological Magazine in 1965"
TL;DR: In this paper, it was suggested that the fold and fault structures in Israel and adjacent areas are drag effects along this strike slip fault. But this was not the case in the case of the Dead Sea.
Abstract: The rifting of the Red Sea, the folding of the Zagros-Taurus range (in Turkey and Iran), and the development of the structures in and near Israel appear to have resulted from a northward anti-clockwise rotational movement of Arabia, which occurred in several phases during upper Cretaceous to Pleistocene times. The sinistral strike slip fault of the Dead Sea fault system participated in this movement. It is hereby suggested that the fold and fault structures in Israel and adjacent areas are drag effects along this strike slip fault.
256 citations
TL;DR: In this paper, it is argued that rocks commonly occur which show a variation in fabric from place to place similar to the whole or part of the possible variation in shape of the deformation ellipsoid.
Abstract: According to the symmetry principle the fabric of a tectonite reflects the symmetry of the deforming movements. Where the symmetry of the deformation varies from place to place this should be reflected in a similar variation in the fabric. The possible variation in homogeneous strain is best shown by the range of variation possible in the deformation ellipsoid. It is argued in the paper that rocks commonly occur which show a variation in fabric from place to place similar to the whole or part of the possible variation in shape of the deformation ellipsoid. It is concluded that such rocks have deformed by homogeneous strain. This conclusion is supported by the shapes and orientations of pebbles in deformed conglomerates.
211 citations
TL;DR: In this paper, a revised Stratigraphical scheme based on numerous measured sections and extensive mapping is proposed for the Carboniferous and Permian sequences of Spitsbergen and Bjornoya, the important Arctic archipelago, in order to provide an up-to-date framework for future work there.
Abstract: A revised Stratigraphical scheme based on numerous measured sections and extensive mapping is proposed for the Carboniferous and Permian sequences of Spitsbergen and Bjornoya, the important Arctic archipelago, in order to provide an up-to-date framework for future work there. New data on the fusulinid zones is summarized and the age of the sequence discussed. A brief Stratigraphical interpretation with four maps showing outcrops, thicknesses, active faults, and main lithological boundaries is given and recent published and unpublished work is reviewed.
145 citations
TL;DR: In this paper, a late-Caledonian metamorphic event at about 422 million years in the Highlands and the relationship of this to previous metamorphisms is discussed and new potassium-argon age determinations are presented for rocks ranging in age from Lewisian to Tertiary.
Abstract: New potassium-argon age determinations are presented for rocks ranging in age from Lewisian to Tertiary. A late-Caledonian metamorphic event at about 422 million years is very important in the Highlands and the relationship of this to previous metamorphisms is discussed. Newer Granite emplacement took place about 400 million years ago and the Moine thrust movement also took place at about this date. Lower Carboniferous basalts yield, by whole rock methods, ages compatible with the time scales of Kulp (1960) and Holmes (1959). Volcanic activity in Mull is confirmed as Palaeocene or Eocene in age.
90 citations
TL;DR: A formation composed of unbedded scaly bentonitic clay containing abundant scattered exotic blocks, boulders, pebbles, and smaller fragments is described from eastern Timor.
Abstract: A formation composed of unbedded scaly bentonitic clay containing abundant scattered exotic blocks, boulders, pebbles, and smaller fragments is described from eastern Timor. It is proposed to call this formation the Bobonaro Scaly Clay. This formation is compared closely with the Argille scagliosa of the northern Apennines. Its origin is ascribed to submarine sliding of an unstable clay mass from the area north of Timor under the influence of gravity, closely associated with the emplacement of large overthrust slices of strata that marked a climax of the mid-Tertiary orogeny in Timor. The discovery of this formation has helped to bring about a radical revision of the published views of the stratigraphy and structure of Timor.
46 citations
TL;DR: Miller and Brown as discussed by the authors showed that the K/Ar ages determined for rocks of the Strathspey complex, Scotland, are at variance with geologic evidence, and they proposed a method to correct the variance.
Abstract: Conclusions drawn by J. A. Miller and P. E. Brown on the basis of K/Ar ages determined for rocks of the Strathspey complex, Scotland, are shown to be at variance with geologic evidence.
46 citations
TL;DR: In this article, three sub-provinces are recognized in the volcanics of the southern half of Kenya as follows: (a) the Miocene phonolite sub-province, (b) the Mount Kenya phonolites/basanites sub-Province, and (c) the Rift Valley trachyte/olivine basalt subprovince.
Abstract: Three sub-provinces are recognized in the volcanics of the southern half of Kenya as follows:—(a) the Miocene phonolite sub-province, (b) the Mount Kenya phonolite/basanite sub-province, and (c) the Rift Valley trachyte/olivine basalt sub-province. Mela-nephelinitic lavas in the two phonolitic sub-provinces are shown to differ significantly in mineralogy, chemistry, and associated volcanics. The type of volcanic association likely to be related to carbonatite occurrences is briefly discussed.Areas of exposed Miocene phonolite and Plio-Pleistocene trachyte are much greater than those of associated basic lavas, while intermediate types are almost lacking. Calculations show that assimilation of gneissic basement rocks by basanite (or olivine mela-nephelinite) and by olivine basalt may contribute to the development of phonolite and trachyte respectively. Available supporting evidence is discussed, both from Kenya and from similar volcanic provinces elsewhere. The additional amount of salic derivatives “which can be produced in this way is small, however, relative to the volume of basic parent involved.
29 citations
TL;DR: In this article, the felsites and granophyres of a small area of central Rhum (Scotland), forming the eastern part of the northern edge of the Tertiary igneous complex of the region, are essentially similar chemically and mineralogically, indicating crystallization from the same parent magma.
Abstract: Although they are contrasting types of acid rocks, the felsites and granophyres of a small area of central Rhum (Scotland), forming the eastern part of the northern edge of the Tertiary igneous complex of the region, are essentially similar chemically and mineralogically, indicating crystallization from the same parent magma. Differences in texture are attributed to crystallization in different environments. Rapid loss of volatiles in the environment of a cauldron subsidence fracture zone occupied by explosion breccia caused chilling of the melt to a glass whose devitrification resulted in formation of the felsites. The granophyres were formed in an environment in which loss of volatiles was less rapid and supercooling was not as great. Both the degree of supercooling and the composition of the magma are critical in the production of the granophyric texture. A composition lying on the cotectic line for the relevant water vapor pressure and a degree of supercooling in the region of the maximum rates of nucleation and crystal growth are prerequisites for the development of the granophyric texture.
27 citations
TL;DR: Graphite was deposited in and around a diabase intruded along post-Borrowdale Volcanic, pre-Bala faults about 4,000 feet above the Skiddaw Slate and Bala boundary as mentioned in this paper.
Abstract: Graphite was deposited in and around a diabase intruded along post-Borrowdale Volcanic, pre-Bala faults about 4,000 feet above the Skiddaw Slate-Borrowdale Volcanic boundary. Associated copper-lead-zinc mineralization follows faults of the same trend, and is isotopically dated at 470 million years (mid-Ordovician). The breakdown of carbon monoxide in the magmatic gases was promoted by substances (notably pyrite, iron oxides, iron silicates, and quartz) which catalysed the Boudouard reaction 2CO CO 2 + C. The PT conditions of deposition of the graphite and associated minerals are estimated at P approximately 1,000 bars, T approximately 120 degrees to 600 degrees C. Possible occurrences of natural interlamellar compounds of graphite are discussed.
27 citations
TL;DR: In this paper, it was shown that the Umkondo system was broadly continuous in structure and metamorphism during the important orogeny c. 500 m·y and the possibility that the mobile belts were active considerably earlier than 500m·y is discussed.
Abstract: Reconnaissance work carried out in north-east Southern Rhodesia has shown that the Umkondo System, previously known in the Mozambique Belt, extends into the Zambesi Belt. It is further demonstrated that the two belts were broadly continuous in structure and metamorphism during the important orogeny c . 500 m·y. The possibility that the mobile belts were active considerably earlier than 500 m·y. is discussed.
27 citations
TL;DR: Sediments of late Pre-Cambrian age mapped in the Kimberley Region of Western Australia have all the characteristics of tillite, and their glacial origin is confirmed by: the presence of very large polished and striated erratics, the great diversity of megaclasts, their regional extent, and presence of striated, grooved, and polished quartzite bedrock directly beneath the tillite as mentioned in this paper.
Abstract: Sediments of late Pre-Cambrian age mapped in the Kimberley Region of Western Australia have all the characteristics of tillite, and their glacial origin is confirmed by: the presence of very large polished and striated erratics, the great diversity of megaclasts, their regional extent, and the presence of striated, grooved, and polished quartzite bedrock directly beneath the tillite. Faceted and flat-iron-shaped pebbles are rare or absent; most megaclasts tend towards an ellipsoidal shape—an observation in agreement with recent theories of glacial abrasion.
TL;DR: A structural analysis of the cliffs and one pit section in Pleistocene deposits at Weybourne has shown one major phase of ice movement only as discussed by the authors, which caused the disturbance of the upper part of the Chalk and the deformation and deposition of a chalkyboulder-clay, thought to be equivalent to the Lowestoft till.
Abstract: A structural analysis of the cliffs and one pit section in Pleistocene deposits at Weybourne has shown one major phase of ice movement only. Ice moving from approximately 210 degrees caused the disturbance of the upper part of the Chalk (together with the overlying Weybourne Crag) and the deformation and deposition of a chalky-boulder-clay, thought to be equivalent to the Lowestoft till.
TL;DR: In this paper, a clear distinction is made between biostratigraphic units (bodies of rock strata characterized by certain palaeontological features and bounded by the limits of known occurrence of such features) and chronostratigraphy units (BSTs) characterized by representing the rocks formed during certain time-spans of earth history and bounded above and below by isochronous surfaces.
Abstract: Comments are given on a number of papers dealing with principles and procedure in stratigraphic classification which have appeared in British journals during 1963–65. It is emphasized that a clear distinction should be made between biostratigraphic units—bodies of rock strata characterized by certain palaeontological features and bounded by the limits of known occurrence of such features—and chronostratigraphic units—bodies of rock strata characterized by representing the rocks formed during certain time-spans of earth history and bounded above and below by isochronous surfaces. Biostratigraphic zones and the chronostratigraphic terms chronozone and stage are discussed.
TL;DR: In this article, a subphase of the 9Langkawi folding phase is identified, which has caused a deformation of the slaty cleavage in the areas showing slight regional metamorphism and a cross-folding in areas which have only suffered flexure folding, and a lowangle overthrust has been developed during post-Permian and pregranitic time.
Abstract: Cleavage folding, flexure folding, and intrusion of granite sills in Cambrian and Ordovician-Silurian sediments are a result of the 9Langkawi folding phase9. This folding phase is dated as late Silurian-Devonian in age. A subphase can be discerned which has caused a deformation of the slaty cleavage in the areas showing slight regional metamorphism and a cross-folding in the areas which have only suffered flexure folding. The presence of an unconformity between Silurian and Carboniferous strata in Thailand and the presence of only a few scattered outcrops of Devonian strata in Malaya suggest that the Langkawi folding phase was not only active in the Langkawi islands but must have had a wider sphere of influence. A low-angle overthrust has been developed during post-Permian and pre-granitic time. This thrust is later arched by the granite intrusion during the Pacific orogeny.
TL;DR: In this article, it was shown that the local magnetic anomalies observed from measured magnetic properties of pyroxenites of the marginal ultrabasic and basic rocks of the Loch Ailsh alkaline intrusion in the Assynt district of northwest Scotland are not reconcilable with the hypothesis that the intrusion is a stratified laccolith.
Abstract: Large local magnetic anomalies observed from measured magnetic properties of pyroxenites of the marginal ultrabasic and basic rocks of the Loch Ailsh alkaline intrusion in the Assynt district of northwest Scotland are not reconcilable with the hypothesis that the intrusion is a stratified laccolith. Rather than a low-angle structure, the intrusion is a steeply dipping sheet at the contact between syenite and limestone country rock. By analogy, similar locally developed anomalies along the southern margin of the Loch Borralan complex are interpreted as due to steeply dipping rocks occupying the same general position between limestone and syenite.
TL;DR: The Coniston grits east of Lune valley occur in a thick series of Ludlovian turbidites that is widely developed in south Westmorland and northwest Yorkshire, England.
Abstract: The Coniston grits east of Lune valley occur in a thick series of Ludlovian (Silurian) turbidites that is widely developed in south Westmorland and northwest Yorkshire, England. Contrary to the conclusion that the grits were derived from a land mass composed of the Borrowdale volcanic series (Ordovician) dividing the Lake District from southern Scotland, it is suggested that the Ballantrae series of the Cockburn land mass traversing the Southern Uplands from northeast to southwest was the source of the grit materials.
TL;DR: A modified version of the hypothesis that the ultrabasic and basic gneisses are metamorphosed intrusive sill-like masses within a migmatite complex now represented by the layered acid Gneiss is proposed in this article.
Abstract: Ultrabasic and basic gneiss masses exposed in the early Lewisian (Precambrian) complex, near Scourie and Drumbeg, Sutherland, Scotland, have been defined as metamorphosed and disrupted layered igneous intrusions. This interpretation is considered incompatible with the field relationships, mineralogy, and geochemistry of the rocks. A modified version of the hypothesis that the ultrabasic and basic gneisses are metamorphosed intrusive sill-like masses within a migmatite complex now represented by the layered acid gneiss is proposed, incorporating the concept that the ultrabasic gneisses represent ultrabasic intrusive rocks which were tectonically emplaced among rocks that subsequently became the layered acid gneisses.
TL;DR: The conglomerate band exposed in the Gullet quarry (Malvern hills, England) occurs above Malvernian (Precambrian) rock and contains a layer of shelly limestone in which corals, brachiopods, and other organisms are incorporated as mentioned in this paper.
Abstract: The conglomerate band exposed in the Gullet quarry (Malvern hills, England) occurs above Malvernian (Precambrian) rock and contains a layer of shelly limestone in which Malvernian rock fragments and remains of corals, brachiopods, and other organisms are incorporated. The mode of occurrence and characteristics of the conglomerate suggest formation in a nearshore environment of carbonate deposition that was supplied with clastic material from sea-stacks in front of a retreating cliff. Conodonts represented in the fauna of the conglomeratic limestone are assigned to nine genera and species. They are described and in conclusion it is noted that they indicate an earlier Llandoverian (Silurian) age than has previously been assigned to the conglomerate.
TL;DR: Joint or fracture cleavage surfaces in the Paleozoic rocks of the Armorican deformation belt of south Pembrokeshire, Wales, intersect bedding surfaces parallel to adjacent fold axes and form acute angles with stratigraphically higher bedding surface, closing toward adjacent anticlinal hinges as discussed by the authors.
Abstract: Joint or fracture cleavage surfaces in the Paleozoic rocks of the Armorican deformation belt of south Pembrokeshire, Wales, intersect bedding surfaces parallel to adjacent fold axes and form acute angles with stratigraphically higher bedding surfaces, closing toward adjacent anticlinal hinges. They are characteristically interrupted at bedding surfaces and vary in frequency with lithology. Calcareous concretionary rods that are now oriented parallel to the axial trace-fractures, and at right angles to fold axes, are considered to have been originally normal to depositional surfaces. The fractures are interpreted as having formed immediately before or at the beginning of Armorican folding and to have been rotated and sheared during the folding.
TL;DR: In this paper, the position of the Siluro-Devonian boundary is reviewed in the light of recent studies in both shelly and graptolitic facies in Europe and elsewhere, and it is suggested that a position at the base of the Monograptus uniformis zone might prove the most widely satisfactory solution.
Abstract: The positioning of the Siluro-Devonian boundary is reviewed in the light of recent studies in both shelly and graptolitic facies in Europe and elsewhere. A case can be made for retaining the present position at the base of the Ludlow Bone Bed; but international opinion may demand a new standard section in the graptolitic facies, for example in central Europe. In this event, it is suggested that a position at the base of the Monograptus uniformis zone might prove the most widely satisfactory solution.
TL;DR: The pattern of punctae in dalmanelloids does not differ in its basic geometry from that of the terebratuloids and can be defined by the same parameters and this also holds for the punctate spiriferoids and the punctates orthotetid genus Streptorhynchus.
Abstract: A geometric model is proposed to explain the quincunx pattern of punctae which characterizes most terebratuloids. This model gives the two parameters d and g, which together express the density of punctae. The pattern of punctae in dalmanelloids does not differ in its basic geometry from that of the terebratuloids and can be defined by the same parameters. This also holds for the punctate spiriferoids and the punctate orthotetid genus Streptorhynchus. The pattern of pustules in the taleolate brachiopods differs from that of the model for the quincunx pattern of punctae, but can still be expressed in terms of d and g. In this case d corresponds to the wavelength of the costellae. Both punctae and pustules are morphologically and numerically related to the marginal setae.
TL;DR: Although Bacon mentioned the shape of the continents in his Novum Organum (1620), there was no reference to the so-called jig-saw fit of the west coast of Africa with the east coast of South America as discussed by the authors.
Abstract: Although Bacon mentioned the shape of the continents in his Novum Organum (1620), there was no reference to the so-called jig-saw fit of the west coast of Africa with the east coast of South America. Instead the similarities of both east coasts and both west coasts were noted. The beginnings of the concept of continental drift can therefore not be attributed to Bacon.
TL;DR: In this paper, the Torridonian rocks seen on the islands of Fladday, Raasay, and Scalpay are described, where Breccias and grits, believed to be subaerial in their lower part, are overlain or pass laterally into grey shales and sandstones of lacustrine or shallow water marine origin.
Abstract: The succession of the Torridonian rocks seen on the islands of Fladday, Raasay, and Scalpay is described. Three lithological fades indicative of three distinct sedimentary environments are recognized. Breccias and grits, believed to be sub-aerial in their lower part, are overlain, or pass laterally into, grey shales and sandstones of lacustrine or shallow water marine origin. These are succeeded by red fluviatile sandstones and shales, which, except near the base, are coarse grained and pebbly throughout much of the succession. Three cases of lateral facies variation are described and their significance discussed with regard to the Torridonian succession elsewhere in the Inner Hebrides and on the mainland.
TL;DR: A microscopic study of sandstones of Old Red Sandstone and Carboniferous ages along a part of the North Crop of the South Wales coalfield reveals that the rocks are extensively fractured as discussed by the authors.
Abstract: A microscopic study of sandstones of Old Red Sandstone and Carboniferous ages along a part of the North Crop of the South Wales coalfield reveals that the rocks are extensively fractured. The fractures occur in the quartz grains and are often filled with bubble-like inclusions. These planes of inclusion were studied in specimens over a wide area, and are related to the directions of faulting and jointing. The consistency in trend between the macro and microstructures suggests a homogeneity of the deforming stresses.
TL;DR: In this paper, the parent magma was close to a biotite pyroxenite in composition and possibly the hybrid product of assimilation of peridotite by granite.
Abstract: Leucite tephrite, leucite basanite, and potassic ankaramite are the rock types recognized in the highly potassic undersaturated volcanic rocks forming gravitatively differentiated lava flows in north Johore, Malaysia. The flows are intruded by thin shoshonitic dikes and a large undifferentiated shonkinite sill. Both the lavas and hypabyssal intrusions are probably Tertiary in age. Modal and chemical analyses are presented. It is concluded that the parent magma was close to a biotite pyroxenite in composition and possibly the hybrid product of assimilation of peridotite by granite.
TL;DR: In this article, it is suggested that an unresolved problem still exists in the naming of the beds above the British Ludlovian stage which are now brought within the Silurian.
Abstract: A discussion and appreciation of a paper by C. H. Holland (see preceding abstract). It is suggested that an unresolved problem still exists in the naming of the beds above the British Ludlovian stage which are now brought within the Silurian. It is proposed that the Ludlovian be extended to include the beds in question.
TL;DR: Round and oval lapilli occur in bands of fine-grained siliceous sediment of the Haimaraka formation (Precambrian) outcropping in the Mazaruni river valley, Guyana as discussed by the authors.
Abstract: Round and oval lapilli occur in bands of fine-grained siliceous sediment of the Haimaraka formation (Precambrian) outcropping in the Mazaruni river valley, Guyana. The lapilli-bearing bands are associated with sandstones and volcanic sandstones exhibiting unmistakable sedimentary features. In structure the lapilli are very similar to those from terrigenous airfall tuff material of volcanic activity in both historic and geologic time that was characterized by eruption of dense clouds of ash accompanied by large amounts of steam. The lapilli in the Haimaraka formation are therefore interpreted as products of redistribution of material derived from ash deposited on land. Deposition of the land-derived material is considered to have occurred near the flank of a geosynclinal trough.
TL;DR: The evidence presented for the supposed continuation of the Southern Uplands fault in north-east Ireland is critically examined and found to be less convincing than recent statements imply by as mentioned in this paper.
Abstract: The evidence presented for the supposed continuation of the Southern Uplands fault in north-east Ireland is critically examined and found to be less convincing than recent statements imply.
TL;DR: Conjugate folds consisting of a system of paired monoclinal flexural folds have been observed in association with shear joints and lamproschists in rocks of the Moine nappe in the Ben Klibreck area, central Sutherland, Scotland as mentioned in this paper.
Abstract: Conjugate folds consisting of a system of paired monoclinal flexural folds have been observed in association with shear joints and lamproschists in rocks of the Moine nappe in the Ben Klibreck area, central Sutherland, Scotland. They occur some 15 miles east of the Moine thrust zone. Spatial relationships and structural evidence indicate that formation of the joints and flexures was closely related in time and took place after emplacement of the Newer Granites and before Old Red Sandstone sedimentation. Correlation with events in the thrust zone shows that thrust movements occurred in lower Old Red Sandstone time and were contemporaneous with rapid isostatic uplift of the axial zone of the Caledonian orogen.