bluuebunny/crossref_metadata_2025_split huggingface dataset:
The movements of island arcs
Authors: Brouwer H. A. 
Published: October 2009

Summary
Through geological time successive orogenic belts have shifted outward from central nuclei. Island arcs of the geosynclinal stage have often moved large distances in a horizontal direction. In the active zones of today movements continue, especially in association with the arcuate structure of the Pacific region, where the highest seismicity is reached.
There has been difference of opinion as to whether faulting or folding is the dominant structural feature in island arcs. Both are very important. The age of the faults may be considerable. Periods of thrusting have been genetically connected with tear-faulting and may have been followed by normal faulting. Relative horizontal displacements, which were not simultaneous or in the same direction, are supposed to have changed the position of areas of higher stability. Older strikes are often cut obliquely by the present coast-lines. There is continuity of structural control but the locus of tectonic activity has shifted. Definite conclusions as to the possible extension and maximum depth of the Tertiary seas cannot be derived from geological evidence.
The recent and earlier phases of deformation show different stages of growth. A number of non-homologous types can be distinguished. The future development of island arcs will be a complex process. Some arcs front toward the oceans and others toward continental areas, and the Pacific arcs do not all front with their convex sides toward the Pacific basin. Growth-stages of the present island arcs are discussed.
The pre-Torridonian metamorphic history of the Loch Torridon and Scourie areas in the North-West Highlands, and its bearing on the chronological classification of the Lewisian
Authors: Sutton John , Watson Janet 
Published: October 2009

Summary
The paper describes the metamorphic history of two areas of Lewisian gneiss in the North-West Highlands of Scotland. Metamorphosed sedimentary rocks are described for the first time from the Loch Torridon area. It is shown that both in the Loch Torridon and the Scourie districts the gneisses have been produced in two separate periods of metamorphism, migmatization and deformation. These two metamorphic episodes, which are named the Scourian and Laxfordian episodes, are separated in time by a period of uplift and tension during which a series of uniform dolerite dykes was intruded. Since a very great interval of time appears to have elapsed between the two metamorphic episodes, it is suggested that the rocks produced during these episodes should be regarded as members, not of a single formation as heretofore, but of two distinct chronological units.
Llandovery brachiopods from Wales with special reference to the Llandovery district
Authors: Williams Alwyn 
Published: October 2009

Summary

The paper is intended primarily as a palaeontological supplement to the stratigraphical studies of the Llandovery rocks in the type area (O. T. Jones 1925, 1949). The systematic revision is therefore based on collections obtained from the Llandovery district but material, in certain instances, has also been described from the Llandovery rocks of Meifod and Haverfordwest. Thus the basal beds (A
x
) of the Llandovery district are unfossiliferous, whereas the equivalent rocks in Meifod and Haverfordwest are richly fossiliferous and so provide important links between the Llandovery and the Ordovician brachiopods. Furthermore, some forms, especially those from the prolific Gasworks Sandstone of Haverfordwest, are better preserved than contemporaneous ones from Llandovery and have been used for specific descriptions.

The systematic study includes emended descriptions of nine species and the erection of two new genera, one new subgenus, eleven new species and fourteen new subspecies. Such a revision may seem radical, but it must be borne in mind that the fauna has received little attention in the past, and actually this work is intended only as the beginning of a much fuller investigation.
The paper concludes with a faunal list to show the stratigraphical distribution of Llandovery brachiopods. The chart emphasizes the fact that each of the lithological divisions established for the Llandovery district contains a diagnostic faunule.
The migmatites and felspar-porphyroblast rock of Glen Dessarry, Inverness-Shire
Authors: Harry William Trevelyan 
Published: October 2009

Summary
In Glen Dessarry, Inverness-shire, the core of a sharp anticline affecting regionally injected Moine rocks is occupied by a hornblendic inlier petrographically comparable with the Lewisian of North-West Scotland and chiefly composed of a series of felspathic gneisses, with subordinate pyroxene-amphibole rocks originally sediments, later metasomatized, and abundant pink pegmatite. The felspathic gneisses include basic, dioritic and syenitic types, the last occupying the centre of the inlier. They are considered to have resulted from migmatization of pyroxene-amphibole rocks by pegmatitic material and constitute an evolutionary sequence of decreasing basicity. Movements within the gneisses during their formation impressed steeply inclined directional structures upon them, and are believed to be of post-Moine age.
With the decline of the stresses that accompanied migmatization the felspar mosaic of some gneisses recrystallized to form larger alkali-felspars of good outline, originating a series of porphyroblastic gneisses of varying basicity. The most striking of these is a rock with the appearance and chemical composition of a syenite, almost wholly composed of randomly orientated, large, grey alkali-felspars, and termed “felspar-porphyroblast rock”. The dominant factors in the formation of this rock are believed to have been stress decline, elevated temperatures and the promoting action of interstitial fluids residual from migmatization.
The Fuller's Earth of the Cotswolds, and its relation to the Great Oolite
Authors: Arkell William Joscelyn , Donovan Desmond Thomas 
Published: October 2009

Summary
Lateral changes in the Fuller' Earth formation along the 50 miles of strike from the Avon valley at Bath to the Vale of Moreton at Stow-on-the-Wold are investigated by means of six-inch mapping of five selected areas.
It is shown that the Fuller' Earth Rock of the Bath district when traced northwards into the southern part of the South Cotswolds becomes two distinct rock bands separated by up to 30 feet of clay, so that there are two Fuller' Earth Rocks and three Fuller' Earth Clays.
In passing farther northwards, first the upper clay wedges out near Horton, then the upper rock passes laterally into Great Oolite “ White Limestone ” near Tresham, and false-bedded oolites come in below it; next the middle clay (which is the Upper Fuller' Earth of the northern part of the South Cotswolds and of the mid-Cotswolds) wedges out on approaching Nails worth; next the lower rock passes laterally into Great Oolite “ White Limestone ” near Nympsfield, and at the same time the false-bedded oolites of Minchinhampton come in below it; and finally the Lower Fuller' Earth Clay wedges out towards Stow-on-the-Wold and Burford and is at least partly replaced by the Chipping Norton Limestone.
The paper shows in detail that S. S. Buckman's correlation fifty years ago of the Fuller' Earth Rock of Somerset with part of the Great Oolite of Gloucestershire, made on the strength of the ammonites, was correct.
The lateral changes and alternations of facies are summarised in horizontal sections (Pl. XVI).
The results of a gravity survey in the country between the Clee Hills and Nuneaton
Authors: Cook Alan Hugh , Hospers Jan , Parasnis Dattatraya Shripad 
Published: October 2009

Summary
Gravity observations have been made in te country between the Clee Hills and Nuneaton. It is found that the change of anomaly over the Warwickshire Coalfield is closely correlated with the thickness of Coal Measures, and over the Forest of Arden it is less closely correlated with the thickness of Trias. The corresponding differences of density agree with densities of rocks measured at the surface. Data are insufficient to establish definite correlations elsewhere.
The remaining anomalities indicate a considerable thickness of rather light rocks, probably Coal Measures, amounting to 4000 feet below the Trias in the Forest of Arden and a considerable thickness of Trias, about 2500 feet with perhaps also some Coal Measures, at Kidderminster.
The succession and structure of the north-eastern area of the South Wales Coalfield
Authors: Blundell Cecil Robert Knight 
Published: October 2009

Summary

The paper deals with that portion of the South Wales Coalfield lying between Pontypool, Blaenavon and Tredegar : that is, the northern part of the East Crop and the eastern part of the North Crop. Although of much smaller thickness than farther west, the Coal Measures in the area have previously been regarded as constituting a full succession. It is now found that nowhere in the area is there a complete succession, the topmost beds of the Lower Coal Series and the lowermost beds of the Pennant Series being absent as a result of a major unconformity of Morganian age. The overlap and overstep developed by this unconformity increases in magnitude eastwards where the gradual disappearance of successive strata have been mapped; the major marine horizons of the Lower Coal Series have also been located and mapped across the area. The palaeontological evidence shows that the highly coloured beds below the Tillery Vein coal seam belong, not to the Lower Coal Series as previously thought, but to the Middle Pennant Group. The palaeontological and mapping evidence further shows that within the present area the Lower Pennant Group is completely absent along the East Crop, and in the south the Middle Pennant Group rests on the basal part of the upper
similis-pulchra
Zone of the Lower Coal Series.

The Coal Measures in the area have been affected by at least two periods of earth-movements, an earlier period of Morganian age and a later Hercynian (Armorican) period. Nevertheless, the folding due to these movements is very gentle, the strong monoclinal folding found in the south-eastern region of the coalfield being absent in the present area. The faults trend mainly in a north-westerly direction and are all tensional structures. They are regarded as accommodation fractures initiated and developed during Coal Measures times.
A Contribution to the Geology of the Kavirondo Rift Valley
Authors: Shackleton R. M. 
Published: October 2009

From
Mr. J. Hospers :—

In Professor Shackleton's paper, as well as in Dr. Dixey's paper (1946) on “ Erosion and Tectonics in the East African rift system,” mention is made of Dr. Bullard's gravity measurements (Bullard 1946). Bullard found that the plateaus surrounding the rift valleys are very nearly isostatically compensated, but that over the rift valleys large negative isostatic anomalies occur. Not only are these rift valleys uncompensated, but there is even more light matter under them than if they were simply cut out of the plateau, leaving the compensation unchanged. Under the rift valley there is therefore an excess of light matter and the upward hydrostatic forces will, according to Bullard, exceed the downward pull of gravity; the floors of the rift valleys will therefore rise unless held under by some other force. Consequently, this settles the argument in favour of the compression theory, a wedge-shaped block (widening downwards) being forced down between reversed faults.
The crucial point in this reasoning is that if a part of the crust is not in isostatic equilibrium (that is, if the isostatic anomalies are not zero or very small) it cannot be in hydrostatic equilibrium.
This is true only for rectangular and not for wedge-shaped blocks. When wedge-shaped crustal blocks float on a denser substratum there is no isostatic equilibrium in the sense that the isostatic anomalies are zero, even though the block may be in hydrostatic equilibrium. In a recent paper F. A. Vening Meinesz (“ Les ‘ graben
The tectonics of the sub-Himalayan fault zone in the northern Potwar region and in the Kangra district of the Punjab
Authors: Gill William Daniel 
Published: October 2009

Summary
The paper defines three major zones of deformation across the Nimadric (Tertiary freshwater) geosyncline between the foreland and the autochthonous folded belt in the North-West Himalaya:—
(1) A zone of open folding, affected to a varying degree by fold-faulting.
(2) A fault zone, displaying a number of reversed faults of steep northerly hade and great lateral extent with open folds between them in the west and, in places, gently dipping monoclines in the east.
(3) A zone with closely spaced strike-faults and severely compressed folds, referred to in the Potwar area as the isoclinal zone, terminating at the main boundary fault which forms the general northern limit of Nimadric rocks.
This succession of structural zones has a superficial resemblance to progressive deformation of the Jura type towards the nappe zone, and previous workers have regarded the tectonic pattern as reflecting tangential pressures from the north.
The author seeks to demonstrate that such an interpretation is denied by the evidence of the structures themselves. Two areas are chosen to illustrate in adequate detail the tectonics of all three zones, and in particular the crucial fault zone. In the west, the Jhamat-Khushalgar area of western Potwar typifies the fault zone of the area between the Indus and the Jhelum rivers. In this area there is clear evidence of the steep hade of the great strike-faults at the surface, and also important evidence of their continued steep hade in depth from the results of boreholes drilled by the Attock Oil Company. Analysis of the relationship of the faults to the fold structures leads to the conclusion that the faults have no genetic relationship to the fold axes. They are considered to be fractures due to shearing stresses principally with a vertical orientation, whilst the folding reflects the subsidiary compressive force. The Nadaun Dun area of Kangra district is some 200 miles to the southeast of the Potwar area, but lies across similar structural zones and typifies the relationships of the anticlinal zone and the fault zone in the region east of the Jhelum River. In this area the Gumber fault is seen to present all the features of the great strike-faults of the fault zone in the Potwar and is an upthrust structure produced by quasi-vertical movement. A feature not present in the Potwar is the marked contrast between the gently dipping monocline to the north of the fault and the strongly folded country to the south, providing a clearer distinction between the influence of tangential and vertical forces. It appears that the fault movement provided a block-line against which tangential forces from the south were directed. Important evidence of tangential pressure from the south is provided by the Barsa fault, which typifies the most common form of fold-fault in the anticlinal zone throughout the region. Gravity collapse structures are recorded in the form of severely overturned “ flaps ” of sandstone on the south side of the Sola Singhi ridge.
Lower Cretaceous ammonites in marine intercalations in the "Nubian Sandstone" of the Eastern Desert of Egypt
Authors: Attia Mahmoud Ibrahim , Murray George William 
Published: October 2009

In 1910, the late Dr. W. F. Hume, Director of the Geological Survey of Egypt, reported Cretaceous fossils from limestones intercalating the “ Nubian Sandstones ” at the head of Wadi Qena, about 205 kilometres (128 miles) north of the town of that name in the Nile Valley. He divided the strata into three typical sandstone beds, namely (1) an upper Nubian at the base of the Campanian, (2) a middle Nubian above the Turonian ammonite bed, and (3) a lower Nubian below the Cenomanian strata and closely related to them (Hume 1911).
During the season 1950–51, while a topographical survey expedition was mapping an area lower down the same Wadi Qena, one of us (G. W. M.) noted a considerable extension of the fossiliferous limestones intercalating the Nubian Sandstones and brought in a good collection of specimens from them to the Geological Survey of Egypt.
The area covered by this note lies between latitudes 27° 00' and 27° 30' and longitudes 32° 35' and 32° 52'. The Nubian Sandstone in this area outcrops as a narrow stretch running roughly N.-S. and is overlaid on the west by Middle and Upper Cretaceous limestones etc., and rests in the east on granites etc. forming the Red Sea hills.
Fossils were collected from eight separate localities, four of which were near the base of the Nubian Sandstone where it rests on the granite while the rest were from higher horizons.
The four localities near the base yielded :—

Diplopodia cf. variolaris
The structural history of Norway and its relation to Great Britain
Authors: Holtedahl Olaf 
Published: October 2009

Summary
The rocks of Norway do not seem to afford evidence of any close geological relation to Great Britain during Archaean time. The birth of the Caledonian geosyncline initiated a fairly intimate connexion, especially with Scotland. A similarity in sedimentary facies and in volcanicity is especially marked in the Ordovician. The " Eocambrian " or " Sparagmite Formation " of Norway has been found to be of great importance in the history of the Caledonian zones of the North Atlantic region. This sedimentary complex, which consists principally of sandstones, with a tillite in its upper part, is stratigraphically and tectonically closely related to the Cambro-Silurian sediments, and equivalent formations are significant in the geology of Scotland. The unassorted " boulder-beds " of the Dalradian in Islay and at Schichallion in Perthshire may well be tillites of corresponding age. There appears to be a natural correlation, too, between the Moinian and the highly metamorphic Eocambrian rocks of Norway.
Old Red sediments of the coastal districts of southern Norway have been subjected to very strong compressive movements : this suggests that the Fennoscandian area at that time existed as a large, rigid block along the border of which broke the " waves " of this posthumous folding.
The structure of the igneous complexes of the Oslo region, of Permian age, with ring fractures as a dominant characteristic, show similarities to both Devonian and Tertiary plutonic centres of Scotland. The faulting just outside the plutonic masses of the Oslo region evidently has close genetic connexion with magmatic processes. The Tertiary uplift of the Scandinavian land-mass is discussed in connexion with submarine relief features off the Norwegian coast, believed to bear witness to marginal fracture-lines.
The supposed Lewisian inlier Of Scardroy, Central Ross-Shire, And its relations with the surrounding Moine rocks
Authors: Sutton John , Watson Janet 
Published: October 2009

Summary
The Scardroy area lies east of the Moine thrust in central Ross-shire and is composed predominantly of metamorphosed sediments. Over considerable areas the rocks are gneissose in appearance, and these gneisses, together with associated striped hornblende-granulites and basic and ultrabasic minor intrusions, were regarded by the Geological Survey as representatives of the basement on which the sediments of the Moine Series were laid down, and were correlated with the Lewisian gneisses west of the Moine thrust.
The present paper brings forward evidence to show that the gneissose rocks were formed by recrystallization and felspathization of siliceous, semi-pelitic, calcareous and hornblendic rocks which are integral parts of the Moine Series. Detailed mapping shows that certain horizons can be traced continuously across the supposed line of unconformity.
Movements accompanying the metamorphism of the Moine rocks led to the production of an anticline and syncline, overturned towards the east and pitching east of south. The minor structures and the axes of quartz girdles determined by fabric analysis pitch in the same direction. On every scale, the same structural pattern characterizes both the Moine and the supposed Lewisian rocks, and no traces of older structures have been detected in the latter.
A tentative stratigraphical succession, established with the aid of sedimentary structures, suggests that the rocks hitherto regarded as Lewisian are younger than a belt of undoubtedly Moinian semi-pelitic granulites.
In view of the facts given above, the writers conclude that the rocks of the Scardroy area belong to a single series and that no rocks of Lewisian age are present.
Some features of Provençal tectonics
Authors: Bailey Edward B. 
Published: October 2009

Summary
It is suggested that criticism of Marcel Bertrand's interpretations of Provençal tectonics has in certain cases overshot the mark. Besides the Beausset klippes the following items seem trustworthy : the Toulon thrust, the Ste. Baume thrust passing under Nans, and the Allauch window.
Notes on Gibraltar and the northern Rif
Authors: Bailey Edward , Muir-Wood Helen M. , Spath Leonard Frank , Chatwin Charles P. 
Published: October 2009

Summary
Gibraltar consists of a Limestone and a Shale Group. Brachiopods long known in the Limestone Group are placed by Choffat and Dubar in the Lower Lias. Ammonites found in the passage beds of the Shale Group are determined as of Middle Liassic age. Radiolarian cherts found in the Shale Group suggest the Upper Jurassic. Since the Limestone Group has been found to overlie the Shale Group there appears to be a great inversion. The present paper revives an interpretation advanced by Gentil and Kober that Gibraltar is a nappe and argues also for an extension of the thrusting already recognized by Fallot in the Rif.
The geology of the Llandello district, Carmarthenshire
Authors: Williams Alwyn 
Published: October 2009

Summary

The Ordovician and Silurian rocks of the Llandeilo area form the flanks and core of the Towy anticline. The oldest beds exposed are the
D. bifidus
Shales which pass upwards into a variable set of sediments, ashes and rhyolite lavas. These beds, with the Ffairfach Grit at the base, have hitherto been classified as Lower Llandeilo, but it now seems probable that they represent a facies variation of the
D. murchisoni
graptolitic shales and should be included in the Upper Llanvirn. The Llandeilo Flags are locally divisible into faunal and lithological units and are followed, with profound lithological and faunal change, by the
N. gracilis
Shales. The
Dicranograptus
Shales are poorly exposed but include towards the top the Crûg Limestone, apparently equivalent to the Robeston-Wathen Limestone of South-West Wales.

Important folding and faulting movements occured before the deposition of the Ashgillian rocks and resulted in the elevation of an important geographical barrier, the Towy anticline. Ashgillian deposition was limited to a basin west of the anticline, where at least 5000 feet of mudstones accumulated. The barrier persisted throughout most of the Silurian, but was breached by transverse troughs during Llandovery times and was subjected to sporadic sea invasions from the north-east, so that the Llandovery and Wenlock mudstones are involved in uncomformable overlaps and oversteps. The Towy anticline continued to exercise this geographical control until Upper Wenlock times, when it was completely inundated and buried in mudstones which were laid down far beyond the limits of the older Silurian rocks.