bluuebunny/crossref_metadata_2025 huggingface dataset:
A Rhyolitic Injection-Breccia in Tuff near Allt Slapin, Strath, Skye, Scotland
Authors: Ray P. S.
Published: May 2009

A rhyolitic breccia-body is emplaced within an indurated mafic tuff which outcrops along the south-western margin of the Beinn na Caillich granophyre mass in the Isle of Skye. The breccia provides evidence of two distinct processes in operation during and prior to emplacement. The tuff which includes felsic rock debris has an intrusive near-vertical junction with the Liassic sediments. It is believed that the tuff was emplaced within a pre-existing volcanic channel. The sequence of post-Liassic eruptive activity in this area ended with the emplacement of the granophyre.
Petrography and Geochemistry of Some Basic Sills and Dykes from Southern Rhenish Schiefergebirge
Authors: Schulze E. G. , El-Hinnawi Essam E.
Published: May 2009

The petrographical and geochemical characteristics of some basic sills and dykes from Southern Rhenish Schiefergebirge are described. The dykes are generally more altered than the sills and are classified into two types according to their relation to the lead-zinc veins found in the area. The distribution of some trace elements in the sills and dykes is given and the nature and mechanism of alteration are discussed.
The Highest Fossils in the World
Authors: Odell N. E.
Published: May 2009

In his splendid volume Geology of the Himalayas (1964; reviewed in this Number, p. 86), Professor Augusto Gansser refers (p. 164) to the rock specimens brought back from the summit of Mount Everest by the successful Swiss climbers in 1956, and also by the American team in 1963. All the various summit specimens, Professor Gansser states, are lithologically quite identical. They consist of fine-grained, thin-bedded grey calc-schists or platy limestones. The calcites are elongated conformably with the schistosity, which seems to parallel the bedding. The detrital grains are mostly quartz, acid plagioclases and some microline, together with fine sericite lamellae, paralleling the calcites. Gansser continues: “Of special interest is the fact that both samples contain crinoidal fragments. Their large uniform calcite crystals contrast with the otherwise much finer crystalline matrix. In one elongated stem-fragment the segmentation is visible (Photo. 46), while one small plate still shows the well-preserved perforation (Photo. 47).” Moreover, he observes: “These remnants, representing the highest fossils in the world, are unfortunately not sufficiently well-preserved to allow an age-determination of the top Everest limestone. They do, however, support rather than contradict the Carboniferous (to Lower Permian) age generally assigned to the Everest limestones, on the grounds that they are overlain by the (Upper) Permian Lachi Series (Odell, 1943; Wager, 1939).”
Symposium on the Precambrian—Cambrian Boundary
Authors: Cowie J. W.
Published: May 2009

At the International Geological Congress held in Sydney, Australia, in August 1976 a Symposium of papers and discussion on ‘The Precambrian–Cambrian Boundary Problem’ was organized by the author in his capacity as Project-Leader/Chairman of the international Project 29 Working Group on the Precambrian–Cambrian Boundary. The following seven papers arose from this symposium. Project 29 is part of the current research under the auspices of the International Geological Correlation Programme (I.G.C.P.). which is sponsored jointly by the United Nations Educational. Scientific and Cultural Organization (U.N.E.S.C.O.) and the International Union of Geological Sciences (I.U.G.S.).
Plateau lavas and diabase dikes of northwestern Newfoundland
Authors: Strong D. F.
Published: May 2009

Thin undeformed tholeiitic plateau lavas and associated diabase dikes occur intermittently along the western margin of the Appalachian mountain system, and are clearly exposed at its northern extremity in northwestern Newfoundland. In Newfoundland there are consistent chemical differences between the diabase dikes and the plateau lavas which indicate that they were derived from different primary magmas. These differences, along with apparent age discrepancies, could be taken as supporting suggestions of several periods of continental rifting, but such an interpretation is not favoured by the present author.
Ipswichian mammalian fauna from the Beeston Terrace at Boulton Moor, near Derby
Authors: Jones P. F. , Stanley M. F.
Published: May 2009

Mammalian remains are reported from a Pleistocene terrace deposit in the lower Derwent Valley near Derby, which is a correlative of the Beeston Terrace of the nearby River Trent. The faunal assemblage is characteristic of the Ipswichian interglacial and compares favourably with previous finds at other Ipswichian sites in southern Britain. The discovery is significant as it provides the strongest evidence so far for a dating of the Beeston Terrace which is critical to the Pleistocene chronology of the region.
The Late Quaternary history of east-central Ireland
Authors: McCabe A. M. , Hoare P. G.
Published: May 2009

The drift succession in east-central Ireland is the result of a series of ice movements spreading from major centres of dispersion within theIrish Sea Basin and over the north-central Irish plain, and from local mountain sources. These glaciations have produced laterally and vertically complex sequences of deposits. The large-scale events influenced almost the entire area; problems of correlation emerge when considering episodes of relatively restricted extent such as those associated with upland ice-caps in the S and the hitherto unreported readvances which interrupted the withdrawalof ice-sheets across the northern part of the region under examination. Thetask of assigning the older units to particular Quaternary cold stages is frustrated by the absence of interstratified organic horizons. Two possible models of glaciation are considered: one may be regarded as ‘traditional’; the other requires a much shorter period of time by assuming that the stratigraphy records differences in the relative strengths of essentially contemporaneous ice-masses.
High-potassium granites in the Masirah ophiolite of Oman
Authors: Abbotts I. L.
Published: May 2009

Masirah Island lies off the SE coast of Oman and comprises a fully developed, though tectonically disturbed ophiolite, unconformably overlain by early Tertiary limestone. The ophiolite consists of harzburgites, cumulate gabbros, a sheeted dyke complex, and pillow lavas with sediment intercalations. Within the ophiolite occur granites the geochemistry of which, particularly their high K2O and Rb, and low Zr and Zr/Nb, ismore typical of a continental crust environment and suggests that at the time of their formation continental crust existed beneath or immediately W ofthe Masirah Ophiolite.
The zonal pattern of metamorphism in the Scottish Highlands and the displacement along the Great Glen Fault: discussion of paper by G. A. Chinner
Authors: Winchester J. A.
Published: May 2009

The 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.
A new Lampadosocrinus from the Upper Carboniferous of Oklahoma, U.S.A.
Authors: Strimple H. L.
Published: May 2009

The rare cladid inadunate crinoid genus Lampadosocrinus is presently known from 2 species, L. minutus (Peck) and L. obtusus Strimple and Koenig, of lower and middle Mississippian age (Tournaisian, Lower Carboniferous). Lampadosocrinus frustulum sp.nov. is described from the Lower Pennsylvanian (Namurian B or C. Upper Carboniferous) of Oklahoma, U.S.A. Some difficulties encountered in orientation of the theca of microcrinoids presently classified as cladid inadunates are discussed.
Theoretical considerations on mechanical parameters of joint surfaces based on studies on ceramics
Authors: Bahat Dov
Published: May 2009

Morphological features of brittle fracture in glass, ceramics and rocks include fracture origin, mirror plane, mist, hackle, radial striations and concentric undulations. The plume structure which characterizes many joint surfaces is analogous to striations or ‘grainy steps’ developed on fracture surfaces of ceramics. Joint surfaces with plumose structures result essentially from tensile failure, but may also be affected by shear stresses. The ellipticity of the plumose structure commonly observed reflects a region of secondary tensional strain parallel to bedding developed due to anisotropic elastic properties of the rock as a result of formational loading. Striations and hackles may have similar orientations. A distinction between them is important since hackles on a joint surface indicate a rapid fracture whereas striations can result from a slow fracture. Intense undulations without hackling may indicate a slow fracture. A smooth mirror plane on a joint surface indicates that while the fracture had been formed, stresses had reached a certain maximum and then subsided. On the other hand, a joint surface that shows a mirror plane with hackle around its boundaries indicates that no decrease of stresses occurred during fracture, and fracture was possibly produced under a constant stress. Since AH is a material property, the fracture stress σfresponsible for a rapid fracture may be calculated following a determination of the mirror constant AH of the rock by σfrH½=AH
Contrasting cinder cones on the flanks of Mount Etna, Sicily
Authors: Hammill M.
Published: May 2009

Paired eruptive complexes consisting of a symmetrical and an asymmetrical cinder cone are described from Mount Etna. The contrasts in shape and fumarolic activity and the temporal relations of the cones are ascribed to the level of magma in the underlying conduit.
The geology of Kong Karls Land, Svalbard
Authors: Smith D. G. , Harland W. B. , Hughes N. F. , Pickton C. A. G.
Published: May 2009

The only substantial descriptions of the small, generally ice-bound archipelago in eastern Svalbard were from an expedition led by Nathorst in 1898 which landed in Kong Karls Land for fourteen days. Our paper amplifies those findings, from work with a helicopter-borne expedition in 1969. The easternmost of the three main islands, and all the small islands, are formed of basic igneous rocks of Cretaceous age. Two of the main islands, Svenskøya and Kongsøya, are formed of latest Triassic to early Cretaceous strata, protected by caps of Cretaceous lava that determine their shape and the general topography. The third, Abeløya, is basaltic throughout.
Amplification of the Wolstonian Stage of the British Pleistocene
Authors: Shotton F. W.
Published: May 2009

The lithostratigraphical division of the Wolstonian Stage of the British Pleistocene is reviewed in the light of borehole records along the line of the M 69 motorway. The Wolston Clay is divided into 5 members. The evidence from the M 69 shows that 2 periods of glacier advance were separated by a major period of recession of the order of 104 years, in which most of the sediments of Glacial Lake Harrison were deposited. It is argued that this recession was interstadial rather than interglacial.
Radioelement concentrations in British Tertiary Granites
Authors: Tammemagi H. Y.
Published: May 2009

The radioelement concentrations of K, U, and Th have been determined for 9 samples of granite from the Western Red Hills, Isle of Skye, Scotland, and for 10 granite specimens from the Mourne Mountains, Ireland, and are compared to 2 published results for Lundy Island granite. The concentrations are distinctly different for each of the 3 centres, and although the data do not provide conclusive proof, they favour generation of the granites by fractional crystallization of basic magmas.
Retiolitids from the Llanvirn and Darriwillian
Authors: Crowther P. R. , Jenkins C. J.
Published: May 2009

A new record of an early retiolitid,Reteograptussp., from the topmost Llanvirn strata of Abereiddi Bay, South Wales, is described and figured. An approximately contemporaneous upper Darriwillian form from Gisborne, Victoria,Orthoretiolites? speciosus(Harris) is redescribed and shown to differ radically from bothReteograptussp. andR. geinitzianusHall, the type species of the genus.
NW-SE trending monoclines in the Dalradian of Banffshire, Scotland
Authors: Hewitt R. A.
Published: May 2009

The Durn Hill Quartzite of Redhythe Point, near Portsoy, can be divided into an eastern shear zone and a western foliated zone. The latter region is typical of most quartzites between the coast and Keith. NW-SE trending flexures, pure shear folding and wrench faults, interfere with the dominantly NE-SW trending folds of the steep limb of the Boyndie Syncline. Possible large scale NW-SE trending monoclines were identified at Redhaven, Aberchirder and Rothes. Such structures bring down the older fold axial traces and isograds towards the NE.
Evaluation of a New Zealand Tremadocian trilobite
Authors: Wright A. J.
Published: May 2009

Dionide hectoriReed, 1926, is shown on the basis of new collections from the type area in New Zealand to be a Tremadocian ceratopygide close toHysterolenus. The species was placed inTaihungshaniaby Kobayashi (1941). It was provisionally retained in the Taihungshaniidae by Lu (1975) who madehectoritype species of a new genusHectoria(nonHectoriaTrechmann, 1918). Ruapyge nom.nov. is proposed here for the reception ofhectori. The original length/width ratio is determined by Wellman's method, with little consistency in results. Data from the strain ellipses constructed by Wellman's method are then used to calculate values for the attitude of the line of no finite longitudinal strain. The values obtained graphically do not agree with those derived from a formula given by Ramsay (1967); this contradictory situation is in need of explanation.
Danubian deviations and mantle diapirism: a possible origin of the Carpathian Arc
Authors: Crawford A. R.
Published: May 2009

Mantle diapirism centred in Transylvania is suggested as the explanation of the Carpathian Arc and the Pannonian Depression, deviation of the Danube from a formerly straight course, and the trends of the Eastern Alps and horsts and troughs in the Bohemian Massif and Poland. Central location in Transylvania is at the crossing-point of deep fractures, parts of great circles, most conspicuously displayed in Transcaucasia and along the Zagros Main Thrust line. Mantle diapirism extended westward from Transylvania along each lineament in Hungary. Pannonian deep lithosphere may be a subcrustally thinned extension of the Bohemian Massif, with a relict unthinned fragment appearing as the Dobrogean Massif. This extended massif would originally have lain almost parallel to the western boundary of the Russian Platform and to the present Dinaride belt.
Volcanic pebbles from Pleistocene gravels in Norfolk and Essex
Authors: Hey R. W. , Brenchley P. J.
Published: May 2009

In the pre-Anglian Pleistocene of East Anglia and Essex are unfossiliferous gravels with pebbles of flint, quartz, quartzite, chert and volcanic rocks. All appear to belong to the Kesgrave Sands and Gravels of Rose & Allen (1976), which are largely or wholly fluviatile and probably of Beestonian age. Forty-six of the volcanic pebbles, from three different localities, have been examined microscopically. Almost all are fine-grained acid igneous rocks or vitric tuffs, evidently derived from a single suite. Various possible source-areas are considered, of which North Wales, with its Ordovician volcanics, is thought to be the most likely.
Differentiated dyke rocks of Mer Mundwara, Rajasthan and their metallogenic significance
Authors: Viswanathan Sivaramasubramania
Published: May 2009

The differentiated dyke rocks of Mer Mundwara comprise a subalkaline series which includes basalts and dolerites, and an alkaline series which includes theralites, porphyritic alkali syenites and nepheline syenites. These intrude into the coarse grained Precambrian granites which, in their turn, are subjacent bodies in the Aravalli system of metamorphic complex of archaean age. Absolute age of basic volcanics is 56±8 Ma, thus relating their emplacement to Deccan Trap volcanism in the Cretaceo-Eocene times in Central and Western India. Petrochemical characteristics of the basic rocks exemplify an alkaline character and so indicate that the basaltic magma of Mer Mundwara is tectonically and genetically different from the Deccan basalts which are in the main tholeiitic. The geological setting, petrography and major and minor element chemistry (Na > K and abundance of Nb, Co, Sn and V) relegate the dyke rock suite to the alkaligabbroic formations of Borodin (1974) with their parent magmatic source in the upper mantle. The alkaline igneous rocks of Mer Mundwara strongly suggest a possible occurrence of rare earths, niobium, zirconium and fluorine in industrial concentrations and also thorium and phosphorus.
Middle Ordovician facies and trilobite faunas in N America
Authors: Shaw F. C. , Fortey R. A.
Published: May 2009

The generic composition of trilobite faunas around the perimeter of North America during the Medial Ordovician is related to the regional palaeogeography deduced from field evidence. Major divisions into shelf, shelf-edge (biohermal mounds) and slope (upper and lower) can be recognized. The Caradoc immersion of the N American plate resulted in landward invasion of pre-adapted slope forms. Some of these genera had European origins and their appearance is due to migration in deeper water facies accompanying closure of the Proto-Atlantic ocean. There is no obvious repeat of Cambrian biomere patterns in the Ordovician although some later Ordovician trilobites, especially shelf inhabitants, had their origins in earlier Ordovician biohermal or slope communities. The origin and composition of the Remopleuridid faunal Province is briefly discussed.
On some quartz-plagioclase veins in the Connemara schists, Ireland
Authors: Yardley B. W. D.
Published: May 2009

Quartz-plagioclase veins in staurolite schists often have margins depleted in the vein minerals. In some cases vein formation has simply involved recrystallization of groundmass grains into large vein grains in a closed system. The driving force for this process is reduction of strain energy and surface free energy. It is suggested that the veins initiate when grain boundaries have been opened up by hydraulic fracturing during medium grade metamorphism. The segregation process can be explained by a model of local equilibrium between grains and a continuous pore fluid similar to that commonly applied to metasomatic reactions; however, no phase change occurs.
Wave effect on sea grasses in the West Indies: the formation of the bare sand zone
Authors: Mitchell-Tapping H. J.
Published: May 2009

An examination of narrow zones of bare sand, usually averaging 10 m in width, situated between the patch reef and the sea grass beds (Thalassia and Cymodocea), shows that they appear to be primarily the result of wave action. Experiments were conducted in the U.S. Virgin Islands over a period of 5 years, which show the effect of subsurface interference of wave patterns in the forming of these bare sand zones. It is thought by the present author that these sand zones are a major factor in the equilibrium balance of sand quantity necessary for on and offshore transportation, and also in the balance of sand retained behind the patch reefs of the West Indies.
Dating post-metamorphic hydrothermal mineralization in the Lizard complex, Cornwall
Authors: Seager A. F. , Fitch F. J. , Miller J. A.
Published: May 2009

Two new total degassing argon-40/argon-39 age determinations are quoted for crystals of adularia from hydrothermal veins within gabbro of the Lizard, Cornwall. The apparent ages of 147±3 Ma and 201±4 Ma obtained suggests the presence of at least two phases of hydrothermal mineralization long after the close of metamorphism.
Further notes on the strontium contents of unaltered fossil cephalopod shells
Authors: Hallam A. , Price N. B.
Published: May 2009

A likely example of biochemical evolution in the nautiloids is demonstrated, based on X-ray fluorescence analysis of the Sr content of unaltered shells.
Rumanian graptolites from boreholes on the Moesian Platform
Authors: Rickards R. B. , Iordan M.
Published: May 2009

Recent collections of graptolites from the Călărasi, Ianca-Berlescu and Tăndărei boreholes have helped to refine the stratigraphy of Silurian (Wenlock, Ludlow) and Devonian rocks of the Moesian Platform. Fourteen species are recorded for the first time from Rumanian strata, others are left under open nomenclature, whilst well-preserved specimens of the following species provide additional information on their detailed morphology and hence upon their relationships and evolution: Monocliniacis sp., Holoreriolites (Balticograptus) cf. balticus Eisenack, Saetograptus cf. rams (Teller), Monograptus kolihai Bouček, ?Cyrtograptus sp., Barrandeograpus pulchellus (Tullberg), and ?Neodiversograptus ex gr. nilssoni(Barrande).
Trace-element and isotopic data and their bearing on the genesis of Precambrian spilites from the Athapuscow aulacogen, Great Slave Lake, Canada
Authors: Olade M. A. D.
Published: May 2009

The nature and timing of ‘spilitization’, and the original composition of ‘spilitized’ Precambrian lavas fron the Athapuscow aulacogen, Great Slave Lake (Canada) are investigated, using geochemical and Rb/Sr isotopic methods. Relationships and abundances of trace elements of petrogenetic significance suggest that the spilites were not derived from alkaline basaltic magmas, but show petrogenetic affinity with tholeiitic basalts from continental or volcanic island environments. This new interpretation conforms well with the supposed tectonic and geologic environment in which the lavas and pyroclastics were erupted. Assuming an ‘open system’ behaviour for Rb and Sr during intense metasomatism, the isochron age of 1872 Ma obtained for the lavas is considered as the time of ‘spilitization’. This age, when compared with geochrono metric data obtained by other techniques, suggests that the time interval between initial volcanism and subsequent ‘spilitization’ event was brief, and probably related to diagenesis or burial metamorphism during rapid subsidence and sedimentation commonly associated with rifting within aulocogens. A relatively low initial 87Sr/86Sr ratio of 0.7018±0.0005 obtained for the lavas either reflects the low Sr isotope values characteristic of diagenetic pore fluid in Precambrian seas, or suggests that the original ‘primitive’ initial ratio was not adversely affected by the ‘spilitization’ process.
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Observations on the Kaiserstuhl loess
Authors: Smalley I. J. , Krinsley D. H. , Vita-Finzi C.
Published: May 2009

Examination of Kaiserstuhl loess material by scanning electron microscopy reveals fine material adhering to the major particles, fracture features, carbonate overgrowths and signs of particle weathering; all of which appear typical of loess material. The carbonate overgrowths included discrete rhombic crystals, which are possibly dolomite. Alpine and Northern glaciers could have provided fine quartz material for the Kaiserstuhl loess; an Alpine source seems more likely, with perhaps some fluvial transportation involved.
Conodonts from horizons with Goniatites crenistria Phillips in North Wales and the Isle of Man
Authors: Austin R. L. , Aldridge R. J.
Published: May 2009

Carboniferous conodonts are reported from knoll limestones of B2 age in North Wales and of P1a age in the Isle of Man. The faunas from both localities are associated with Goniatites crenistria Phillips and other diagnostic goniatites. The faunas are closely similar and indicate a correlation with the Avonian conodont zone of Mestognathus beckmanni–Gnathodus bilineatus.
The early Tertiary deep-water sandstones near San Sebastian, Spain; some aspects of diagenesis
Authors: Knox G. J.
Published: May 2009

Near San Sebastian, northern Spain, are outcrops of a system of deep-water fans deposited beyond the mouth of a submarine canyon from southward flowing currents. The sandstones consist of mixed siliciclastic detritals and carbonate fragments. The latter includes a derived heterogeneous marine fauna. Carbonate content varies and has played a major part in diagenesis. Early cementation by limited quartz and to a greater extent calcite involved local expansion. Later compaction has led to prominent pressure-solution phenomena of calcite and quartz with formation of microstylolites. Leaching owing to weathering has led to removal of some carbonate and formation of kaolinite from micas.
Pyroclastic flow deposits in the Adrano area of Mount Etna, Sicily
Authors: Duncan A. M.
Published: May 2009

Activity on Etna is predominantly effusive with eruption of lavas of Hawaiitic composition. However, near Adrano some pyroclastic flow deposits outcrop among prehistoric lavas. The chemistry of the pumiceous fragments in these pyroclastic flows suggests they were erupted from magma of benmoreitic composition. This represents some of the most evolved and differentiated magma that has been produced by Etna. The presence of these deposits indicates that in the past Etna has displayed much more explosive activity than has been observed in historic times.
Brecciated lavas from County Limerick, Ireland, and their significance
Authors: Strogen P.
Published: May 2009

Field relations of Carboniferous lavas in Limerick indicate that flow took place in shallow water in many cases. A possible flow mechanism is proposed for these lavas. Brecciation of the flows took place after emplacement due to steam release from underlying limestones, which frequently became thixotropic and injected upwards into the denser lava.
A Possible Extension of the Ratagan Igneous Complex, Wester Ross and Inverness-shire
Authors: Dhonau T. J.
Published: May 2009

An intrusion associated with the Ratagan Complex (Nicholls, 1950) outcrops in Glen Lichd, east of the main omplex. It is separated from the main complex by the Strathconon fault. The intrusion consists of red medium-grained leucocratic granodiorite and adamellite.
New Light on the Dawros Peridotite, Connemara, Ireland
Authors: Leake Bernard E.
Published: May 2009

It is established that the Dawros peridotite of north Connemara contains basic plagioclase mainly in a gabbroic layer in the peridotite but occasionally as rare crystals in the peridotite itself. Carlsbadalbite twin extinction angles indicate that the composition of this feldspar is similar to that in the adjoining Currywongaun-Doughruagh intrusion and that in the ultrabasic rocks of the Cashel-Lough Wheelaun intrusion and the Roundstone intrusion of south Connemara. As all these feldspars are extremely heavily saussuritized because of metamorphism it is difficult to determine their precise composition and so an exceptionally fresh plagioclase from an anorthosite in the Currywongaun-Doughruagh intrusion has been chemically analysed. It is An91·5Ab6·8Or1·7. This is in close agreement with the composition given by measuring 2θ(131)–2θ(131), the refractive indices and 2V while the extinction angles of Carlsbadalbite twins give only a slightly too anorthitic result (An95). The particularly calcic nature of the plagioclase is strong evidence that all the ultrabasic bodies in Connemara are genetically related. Some new structural ideas on the Dawros body are suggested which integrate the structure, petrography and cryptic variation.
Carbonate Tuff Cones in Northern Tanganyika
Authors: Dawson J. B.
Published: May 2009

The carbonate matrix of several pyroclastic tuff rings and cones in the Monduli-Arusha area of northern Tanganyika, is believed to be of volcanic carbonatitic origin. One of the pyroclastic tuff rings contains ejected blocks of ultrabasic composition which are minera-logically similar to the cognate xenoliths found in kimberlite pipes.
Significance of the Radiometric Ages of the Nchanga and Lusaka Granites, Northern Rhodesia
Authors: Drysdall A. R. , Garrard P.
Published: May 2009

The similarity between the “whole-rock” ages of the Nchanga and Lusaka granites, 755 m.y. and 725 m.y. respectively, is misleading. The field evidence indicates that the Lusaka granite, although syntectonic, intrudes Katanga metasediments, whereas the Nchanga granite is overlain unconformably by basal Katanga conglomerate and arkose. The age of the Lusaka granite thus sets a younger limit to the age of the Katanga metasediments of the Central Province and dates the waning phases of the Lufilian orogeny. The radiometric age of the Nchanga red granite is too young for a pre-Katanga intrusive, and it is suggested that it has been modified by subsequent metasomatism.
Current Directions from Folded Strata
Authors: Cummins W. A.
Published: May 2009

In current direction studies, when unfolding strata to their original horizontal attitude, plunge is usually allowed for on the assumption that it was acquired by rotation about horizontal axis at right-angles to the fold axis. Errors resulting from plunge correction on this assumption, if mistaken, are examined
The Relations Between Folds and Late-Formed Joints in South Pembrokeshire
Authors: Hancock P. L.
Published: May 2009

The late-formed joint sets in the Armorican belt of south Pembrokeshire are younger than both the folds and wrench faults of the region. On fold limbs these joint sets are oriented normal to bedding surface and symmetrically about axial-traces. Lens-belts and joint-drags parallel to the joint sets indicate a shearing pattern parallel to stratification planes. The orientations of fractures in collapsed blocks of Carboniferous Limestone, in Triassic breccias, show that the late joints were formed before the end of the Triassic. The term kathetal-joints is used for those which always remain normal to bedding surfaces.
A Correlation of Some Devonian Limestones of New South Wales and Victoria
Authors: Philip G. M. , Pedder A. E. H.
Published: May 2009

A sequence of 11 tetracoral and conodont faunas, ranging from early Gedinnian to late Givetian, is recognized in the Lower and Middle Devonian limestones of New South Wales and Victoria. These faunas are not only important stratigraphically in eastern Australia, but also provide a basis for the correlation of the Australian Devonian with overseas stages. A table of correlation is given for the principal Devonian limestone sequences of New South Wales and Victoria.
Stone Orientation and Other Structural Features of Tills in East Yorkshire
Authors: Penny L. F. , Catt J. A.
Published: May 2009

Macrofabric (stone orientation) and microfabric studies of the four tills exposed in the coastal areas of East Yorkshire indicate that the regional direction of ice movement during both the Saale and Weichsel Glaciations was from north-east to south-west. The Saale (Basement) Till was considerably modified by the advance of ice during the Weichsel Glaciation; in particular, the stones in the Basement were reorientated so that their long axes now lie at right angles to the direction of movement of the Weichsel ice sheet. The fabrics of the three Weichsel tills (Drab, Purple and Hessle) are alike, and it is suggested that all three were deposited from one composite ice sheet. The relationship of vertical joints in the Basement and Drab Tills to directions of ice movement is discussed; those in the Basement possibly originated as ac tension joints inherited from the parent ice, whereas some of those in the Drab are probably conjugate shear joints formed during post-depositional deformation of the till.
The Structure of the Marumbe Ring-Complex, Nuanetsi Igneous Province, Southern Rhodesia
Authors: Johnson R. L.
Published: May 2009

The Marumbe complex is a small ring-intrusion consisting essentially of a plug of nordmarkite separated from the basalt country rocks by a later ring-dyke and roof-sheet of granite. The lower and upper surfaces of a screen of basalt, which lies between the top of the nordmarkite body and the base of the granite roof-sheet, correspond to successive horizontal fractures which permitted blocks limited by ring-fractures to subside as the nordmarkite and granite magmas were intruded. A series of sheets of granite are developed locally in the hanging-wall of the above-mentioned ring-dyke, and further granite ring-dykes cut the nordmarkite and the country rocks.
A section through the Llandovery of N.E. Bavaria, Germany
Authors: Stein Volker
Published: May 2009

A section through the Llandovery of the Frankenwald, in North-East Bavaria, has been described and the fauna of each of the graptolite zones contained therein has been presented. The succession of the graptolites corresponds to that known from Great Britain.
X-ray Examination of some Clays from the London Platform
Authors: Tank R. W.
Published: May 2009

X-ray analyses of Kimmeridgian clays recovered from the Warlingham Number 1 Borehole indicate that illite and kaolinite are the dominant clay minerals present. Illite, chlorite, and kaolinite, are present in the Devonian clays recovered from the Willesden Number 1 Borehole. The relationships between the clay minerals of the Kimmeridgian and Devonian clays and the clay mineral assemblage of the English Wealden is discussed.
Porphyroblastic and Augen Gneisses in the Bartica Assemblage, British Guiana
Authors: Cannon R. T.
Published: May 2009

Textural differences in the occurrence of microcline define augen gneisses, subhedral porphyroblastic gneisses and euhedral porphyroblastic gneisses within the Bartica Assemblage, British Guiana. The introduction of microcline is metasomatic and the nature of the porphyroblasts appears to be a reflection of tectonic control during their development.
Pre-Cambrian Geochronology of Nagpur-Bhandara-Drug, India
Authors: Sarkar S. N. , Gerling E. K. , Polkanov A. A. , Chukrov F. V.
Published: May 2009

On the basis of stratigraphic, tectonic, and metamorphic studies in certain critical Pre-Cambrian areas of Nagpur-Bhandara-Drug region and twenty-six K-Ar age data of representative samples, the authors have suggested a new generalized succession and correlation of the dated orogenic cycles and phases, and have drawn the following conclusions:-

(a) Amgaon cycle closed during the period 1444–1730 m.y.

(b) Sakoli cycle (I phase) closed at 1330 m.y., and during Sausar orogeny (864–996 m.y.) the north-western part of Sakoli syn-clinorium was deformed and metamorphosed (862–950 m.y.).

(c) Sausars and Sakolis, both post-Amgaon in age, were deposited in separate basins and had different tectonic histories.

(d) Nandgaon folding phase (< c. 1200 m.y.) affecting Bijli rhyolites is younger than Sakoli (I phase), and Chattisgarh Cuddapahs are younger than Khairagarh phase (< c. 600 m.y.).

(e) In Bastar area Bailadila cycle closed at c. 2100 m.y.
Cordierite in the Pre-Cambrian Rocks of the South Savannas, British Guiana
Authors: Singh S.
Published: May 2009

The mineral cordierite occurs in Pre-Cambrian gneisses, granulites, and granites of the Guyana Shield in British Guiana. In the Acid Biotite Gneisses and Acid Granulites forming the Kanuku Group, the mineral was formed during regional metamorphism. Considerable enrichment of cordierite occurs in the contact aureole around the South Savanna Granite. Cordierite of xenocrystal origin also occurs in the South Savanna Granite and its apophyses. The 2V and optic sign of the mineral varies widely, and no definite pattern in relation to the paragenesis of the mineral is recognized. Untwinned cordierites are predominant in regionally metamorphosed rocks while lamellar, interpenetration and sector twins are characteristic of cordierites in contact hornfelsed aureole rocks.
The Caledonian Dykes associated with the north-eastern end of the Newry complex, County Down, Northern Ireland
Authors: Grant N. K.
Published: May 2009

The Caledonian dykes fall into two age groups, one older than the Newry complex and the other younger, and these have been compared with the Older and Younger Series of Caledonian dykes from the Ards Peninsula (Reynolds, 1931), which are older and younger respectively than the cleavage movements affecting the Silurian sediments. The suggestion is therefore made that the emplacement of the Newry complex and the cleavage movements in the Ards Peninsula were temporally associated events.

The Caledonian dykes are older than the joints in both the complex and the sediments, while the Tertiary dykes are younger.
Review of some species of Favistina, Nyctopora, and Calapoecia (Ordovician corals from North America)
Authors: Jull R. K.
Published: May 2009

Material from the H. A. Nicholson collection, University of Aberdeen, provides information on three of Nicholson's species. Syntypes of Favistina calicina are described and the lectotype designated. Topotypes of Nyctopora billingsii are compared with an earlier description of the type thin sections. Columnopora cribriformis is considered synonymous with Calapoecia huronensis Billings, itself a poorly understood species; redescription of the type of the latter species shows it to be separate from C. canadensis Billings. Calapoecia ungava Cox is reinterpreted with a lectotype designated, and Nicholson material is placed with this species. All specimens are from eastern North America and of Upper Ordovician age excluding the Middle Ordovician N. billingsii and C. canadensis.
A note on the structure and succession at Abereiddy Bay, Pembrokeshire
Authors: Waltham A. C.
Published: May 2009

A study of the Ordovician rocks on the northern side of Abereiddy Bay has revealed that the succession is locally overturned. Consequently the stratigraphic levels of two horizons are reassessed—the Castell Limestone is placed above the Dicranograptus Shale, and the Llanrian Volcanic Series is allocated to the Lower Llanvirnian.
Some features of the Mesozoic vulcanicity in the Lebanon
Authors: Roberts John L.
Published: May 2009

Dykes of limestone breccia, brecciated masses of limestone within vents, and intrusive relations between basalt and limestone are described as features of interest within a short distance of Beirut.
Petrography and age of the rocks of Bulland Hill, Kirana Hills, Sarghoda District, West Pakistan
Authors: Davies R. G. , Crawford A. R.
Published: May 2009

Petrographic and geochronological studies of the rocks of Bulland Hill, an inlier of basement in the Punjab alluvium, are reported. Acid and basic pyroclastic and high-level intrusive types give an Rb–Sr isochron age of 870±40 million years. The previous correlation with the Malani Rhyolite Series of north-western India must be abandoned.

A porphyry boulder from the Permo-Carboniferous boulder bed, probably a tillite, in the Salt Range has the same age as the Bulland Hill rocks.
The buried channels of the Exe
Authors: Durrance E. M.
Published: May 2009

Seismic refraction surveys of the buried channels of the Exe near Exmouth indicate the presence of an early period of channelling into New Red Sandstone breccias to a base in excess of −52 m* followed by a period of gravel infilling of these channels and then their partial re-excavation to a base in excess of −30 m. Terraces formed during stillstands within the early regression occur at depths of −25, −31·4, and −36 m and within the later regression at −5·8, −10.4, −13.7, −17·1, −22 and −27·1 m. Control of the orientation of the channels by fault planes within the New Red Sandstone is also indicated. Correlation of the periods of channelling with early and late Weichselian sea-level lows is suggested, indicating a middle Weichselian (Paudorfian) age for the gravels. Similarities with buried channels occurring in Southern Ireland are noted and wider correlations attempted.
Thomacystis, a unique new hemicosmitid cystoid from Wales
Authors: Paul C. R. C.
Published: May 2009

Although Thomacystis is clearly a hemicosmitid cystoid, it cannot be included within existing families, and the new family Thomacystidae is therefore proposed to accommodate it.
Structural observations on the Carboniferous Limestone of the North Wales coast
Authors: Nichols R. A. H.
Published: May 2009

Outcrops of Carboniferous Limestone were examined along the coast of North Wales around Penmon in Anglesey, and Great Orme's Head, Gloddaeth and Llanddulas in Caernarvonshire and Denbighshire.

Tectonic forces have folded, jointed and faulted the Limestone, but each area has reacted differently. The differences are discussed and the effects on the different limestone units illustrated.

Caledonian structures adjacent to the areas are briefly discussed. Variation in fold strike from north to east or south-east in the Carboniferous rocks is a reflection of the change in strike in the Lower Palaeozoic rocks, as is the northwest to north strike of the faults.

It is postulated that folding and faulting of the Carboniferous Limestone areas during the Hercynian orogeny was totally guided by Pre-Cambrian and Caledonian structural trends in Anglesey and on the mainland coast, and that the southern compression during the orogeny only accentuated pre-existing trends.
The thecal form of some slender Llandovery Monograptus
Authors: Rickards R. B. , Rushton A. W. A.
Published: May 2009

The thecal form of Monograptus argutus Lapworth and M. leptotheca Lapworth is similar to that of M. incommodus Törnquist, the type species of Pribylograptus Obut & Sobolevskaya; their thecae are geniculate and have introverted and laterally expanded apertures, and M. leptotheca has in addition apertural hoods. The relationships of these species are discussed.
Mullion and Boudinage Structure in Coryton Slate Quarry, near Okehampton, Devonshire
Authors: Dearman W. R.
Published: May 2009

Bedding mullions have been produced by compression parallel to bedding in the hinge region of a large recumbent fold. Geometrically, the mullions are a combination of parasitic folding, with characteristic gadrooned profile, and cleavage planes. The cleavage is not an axial plane structure, but where fully developed produces a perfect slate fabric in rocks of appropriate lithology. The mullions are found on both sides of a bed of inferior slate sandwiched between two beds of good roofing slate. Boudinage structure results where the mullions are exactly back to back, and the planes of separation provided by the cleavage are infilled with coarse calcite. The slates are interbedded and interlaminated with limestone.

Such boudins are unusual in that they occupy the hinge region of a fold and result from compression parallel, rather than at right angles, to the bedding.
Zones of Progressive Regional Metamorphism Across the Western Margin of the Mozambique Belt in Rhodesia and Mozambique
Authors: Vail J. R.
Published: May 2009

Investigations of the sedimentary rocks of the Umkondo System have enabled six zones of eastwardly increasing metamorphic grade to be delineated on the basis of index mineral assemblages in pelite horizons.

Chlorite, garnet (almandine), staurolite, kyanite, and sillimanite isograds have been recognized over a distance of 500 km. along the eastern border of Southern Rhodesia and are plotted on a map. More detailed reconnaissance work has been confined to the Barué highlands north-east of Inyanga. In addition, a “zone of intermediate isotopic age measurements” is proposed to the west of the lowermost chlorite zone. The isograds lie parallel to the structural edge of the north-south trending Mozambique orogenic belt and can be joined with those of similar metamorphic rocks in the east-west trending Zambesi orogenic belt, suggesting contemporaneity of thec. 500 m.y. regional tectono-thermal event in these two belts.
The Distribution of Punctae on the Brachiopod Shell
Authors: Cowen R.
Published: May 2009

The model recently proposed by Kemežys for the distribution of punctae on the brachiopod shell is examined and found to be insufficient. An alternative model is proposed: punctae appear to conform to a hexagonal close-packing pattern on the shell surface. A hypothesis to account for this is introduced, and further implications are discussed.
Intrusive Tholeiites of the Western Cuillin, Isle of Skye
Authors: Hutchison Robert
Published: May 2009

Certain amygdaloidal tholeiitic rocks and associated volcanic breccias are intrusive into the Cuillin gabbro (sensu lato) and are not xenolithic as Harker believed. Six tholeiites have been analysed and their compositions compared with the non-porphyritic central magma type of Mull. It is postulated that the ultrabasic rocks close to some tholeiitic intrusions were contaminated by the tholeiitic magma.
An Olivine-bearing Sagvandite from Berneray, Outer Hebrides
Authors: Livingstone A.
Published: May 2009

Petrographic and chemical data are presented and a possible means of derivation from an ultrabasic rock is discussed.
A Modification of the Geosyncline and Tectogene Hypothesis
Authors: Wyllie Peter J.
Published: May 2009

Intersections may exist between a zone of chemical discontinuity (basalt—feldspathic periodtite or eclogite—garnet peridotite) and a phase transition zone (basalt—eclogite or feldspathic peridotite to garnet peridotite) at about the depth of the continental M-discon-tinuity. Variations in depth to the chemical discontinuity and in the positions of isogeotherms produce flexibility in erogenic models. Intersections between the two zones at depth could be reflected at the surface by major fault zones separating large structural blocks of different elevations. The effects of such intersections on the conventional hypothesis for the development of tectogenes, geosynclines, and mountains are considered. The intersections could provide a beginning and an end to the more vigorous changes in surface level occurring during an orogenic cycle.
A Correlation Between Cleavage-fan Angle and Bed Thickness
Authors: Bayly M. B.
Published: May 2009

A chevron-folded phyllite composed of well contrasted quartzose and micaceous layers was examined. The false cleavage in the mica layers is of fan type and measurements show a correlation between the angle of the fan and the thickness of the layer in which it forms. Such a correlation is to be expected if the folds formed by buckling under lateral compression.
The Evidence for the Southern Uplands Fault in North-east Ireland
Authors: Anderson T. B.
Published: May 2009

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.
The Graphite Deposit of Seathwaite in Borrowdale, Cumberland
Authors: Strens R. G. J.
Published: May 2009

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 ⇌ CO2 + C. The PT conditions of deposition of the graphite and associated minerals are estimated at P ~ 1,000 bars, T ~ 120° to 600° C. Possible occurrences of natural interlamellar compounds of graphite are discussed.
On the Correlation of the Torridonian Between Rhum and Skye
Authors: Stewart A. D.
Published: May 2009

A new correlation of the Precambrian Torridonian sediments of Rhum and Skye is suggested which equates the Bagh na h-Uamha Shale of Rhum with the upper part of the Kinloch Formation in Skye and with the Diabaig Formation on the mainland. The Rudha na Roinne Grit, Loch nan Eala Arkose, and Guirdil Arkose of Rhum are correlated with the Applecross Formation. The occurrence of sedimentary cycles at the base of the Applecross in Rhum and Skye is noted. The strata beneath the Kinloch Formation in Skye are not represented either in Rhum or elsewhere on the foreland and do not belong to the Diabaig.