bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Light on the Dawros Peridotite, Connemara, Ireland
Authors: Leake Bernard E. 
Published: May 2009

AbstractIt 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

AbstractThe 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

AbstractThe 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.
The Relations Between Folds and Late-Formed Joints in South Pembrokeshire
Authors: Hancock P. L. 
Published: May 2009

AbstractThe 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

AbstractA 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

AbstractMacrofabric (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

AbstractThe 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.
X-ray Examination of some Clays from the London Platform
Authors: Tank R. W. 
Published: May 2009

AbstractX-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

AbstractTextural 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

AbstractOn 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

AbstractThe 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

AbstractThe 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

SummaryMaterial 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

SummaryA 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.
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

SummaryPetrographic 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

SUMMARYSeismic 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.
Structural observations on the Carboniferous Limestone of the North Wales coast
Authors: Nichols R. A. H. 
Published: May 2009

SUMMARYOutcrops 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

SUMMARYThe 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

AbstractBedding 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

AbstractInvestigations 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

AbstractThe 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

AbstractCertain 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.
A Modification of the Geosyncline and Tectogene Hypothesis
Authors: Wyllie Peter J. 
Published: May 2009

AbstractIntersections 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

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

AbstractGraphite 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

AbstractA 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.
Petrology of an Irregular-Nodule Bed, Lower Carboniferous, Anglesey, North Wales
Authors: Nichols R. A. H. 
Published: May 2009

AbstractSome of the nodules described are similar to trace-fossils described by Donaldson and Simpson and some ichnofossils described by Seilacher, but many appear to be structures produced by sedimentary boudinage. These do not seem to be a result of organic or concretionary action. It is suggested that currents deposited thin bioclastic calcarenites with interbeds of calcite silt, and that crinoids and coral patches developed only sporadically during deposition. A few scavengers reworked the bioclastic calcarenites and calcite silt layers thus forming the trace-fossils; many of the irregular-nodules, however, were probably formed by differential compaction and segregation in the calcite silt beds, and may represent sedimentary boudins, which are relicts of former layers.
Upper Palaeozoic and Lower Mesozoic stratigraphy of south-western Nordaustlandet, Spitsbergen
Authors: Lowell James D. 
Published: May 2009

SUMMARYUpper Palaeozoic (Permian and possibly Carboniferous) basal sandstones and carbonate rocks rest with angular unconformity on Hecla Hoek rocks in the south-western part of the island of Nordaustlandet, Spitsbergen. Upper Palaeozoic rocks are in turn disconformably overlain by Lower Mesozoic (Triassic and possibly lowermost Jurassic) shales, siltstones, and minor sandstones. The Upper Palaeozoic-Lower Mesozoic sequence thins by sedimentary convergence north-eastward from more basinal areas in Vest-spitsbergen to a stable shelf in Nordaustlandet.
Five Viséan conodont horizons in the north of England
Authors: Austin Ronald L. 
Published: May 2009

SUMMARYFive faunal lists of conodonts recovered from isolated Viséan outcrops in the north of England are presented. The fauna of the Bowland Shale at Burnsall, Yorkshire, and that of theOrionastraeaBed at Bordley, Yorkshire, are representative of theGnathodus mononodosusAssemblage Zone. The fauna of theBollandoceras hodderenseBed (B1), and that of a limestone near the top of the Worston Shale Group (B2) at Little Mearley, Lancashire, represent theMestognathus beckmanni-Gnathodus bilineatusAssemblage Zone. The presence of conodonts in the reef limestone of Swinden, Yorkshire, is also noted.
A large temporary exposure in the Lower Silurian of Shropshire
Authors: Cocks L. R. M. , Walton G. 
Published: May 2009

SUMMARYFresh information on the ecology, sedimentology and structure of the Lower Silurian (Llandovery) Purple Shale of Shropshire has emerged as a result of large-scale excavations. The griestoniensis Zone is proved, and correlated by shelly fossils with the C5 substage of the type Llandovery area. Current directions indicate a source area up-slope to the south-east. Most of the fauna constitutes a Clorinda community, but towards the top of the sequence a Clorinda/Stricklandia mixture is developed.
The Evolution of the Earliest Llandovery monograptids
Authors: Hutt Jana , Rickards R. B. 
Published: May 2009

AbstractThe incommodus, atavus and cyphus monograptid groups appear more or less simultaneously in the atavus Zone. The atavus and cyphus groups are related, one of these probably giving rise to the later tenuis group of monograptids, Possible roots of these groups and relationships with later monograptids are discussed. Monograptus strachani sp. nov. is proposed to replace the name M. incommodus sensu Elles & Wood.