bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of Lower Pleistocene Crag at depth in Suffolk
Authors: Beck R. B. , Funnell B. M. , Lord A. R. 
Published: May 2009

SummaryThe stratigraphy of the early Pleistocene marine deposits erected from a borehole at Ludham, Norfolk, based on pollen and foraminifera, is extended to another borehole at Stradbroke, Suffolk. Pollen analyses from argillaceous parts of the sequence at Stradbroke show a Pre-Ludhamian pollen zone, overlain by the Ludhamian. Foraminiferal evidence indicates that the Pre-Ludhamian is equivalent to part of the Red Crag, thus providing the first direct evidence as to the relative ages of the Red Crag and the Ludhamian. Palaeomagnetic investigations indicate a normal polarity and, by comparison with the Netherlands sequence, an age of at least 1.60 m.y. for the deposition of the Pre-Ludhamian.
Hollow apatites in a layered basic intrusion, Norway
Authors: Gardner P. M. 
Published: May 2009

SummaryCumulate apatite crystals with infilled tube-like cavities parallel to the c-axis are described from a layered gabbro intrusion in Northern Norway. These are considered to be skeletal crystals produced by rapid growth in the supercooled roof zone of the magma chamber. At least two stages of growth are suggested on the basis of the morphology of the apatites. The interiors of the crystals contain phases representing the trapped magma or the cumulus mineral phase within which they are enclosed. Recirculation of the apatite primocrysts by convection currents is indicated by the interrupted form of some of the tubes.
Computation of the values of the finite strains in the Molare region, Ticino, Switzerland, using stretched tourmaline crystals
Authors: Thakur V. C. 
Published: May 2009

SummaryThe stretched crystals of tourmaline occur in the Orange Group gneisses of the Lucomagno massif and in the quartzite of Piano Croce Group in the Molare region, Ticino, Switzerland. They were stretched as a result of an extension acting in the plane containing the tourmaline crystals by the tectonic strain of F3 phase of deformation. The crystals show extension parallel to the F3 fold axes. The computation of the values of the finite strain from stretched tourmaline crystals indicates a constriction-type ellipsoid for the tectonic strain of F3 phase of deformation.
Ignimbrite in Central Kelantan, Malaya
Authors: Aw P. C. 
Published: May 2009

AbstractThe presence of ignimbrite is described for the first time in Malaya. The field relations and a detailed study of the petrography support the interpretation that the 15-mile ridge outcropping in Central Kelantan, Malaya, is a thick “dyke” of ignimbrite which plugs an old feeding fissure. The Temangan Ignimbrite has a texture which is intermediate between tuff and rhyolite lava. The evidence suggests that the Temangan ignimbrite was emplaced as a tuff flow.
A Gravity Investigation of the Pickwell Down Sandstone, North Devon
Authors: Al-Sadi Hamid Nassar 
Published: May 2009

AbstractThe area to the north of Barnstaple (North Devon) was covered by a detailed gravity survey. The main gravity gradient of the Bouguer anomaly map (estimated to be 1·2 mgals per mile) confirmed the conclusions drawn by Bott et al. (1958), who attributed it to a basin of possibly Carboniferous sediments and/or Old Red Sandstone, about 4 miles thick, separated from the outcropping Devonian rocks by an assumed thrust plane.A negative residual gravity anomaly is located over the outcrop of the Pickwell Down Sandstone. Analyses of the anomaly show that it is caused by the southwards dipping belt of sandstone and that the angle of dip of the formation decreases with depth. At a depth of about 2 miles the formation becomes nearly horizontal. Alternatively, it may terminate against an assumed thrust plane underlying the whole outcropping Devonian.The aeromagnetic map of the area shows an elongated magnetic “high” following the outcrop of the Morte Slates. The anomaly is probably caused by near surface, highly magnetized rocks in association with the Morte Slates.
Quartz-Carbonate Veining and Deformation in Namurian Turbidite Sandstones of the Crackington Measures, North Cornwall
Authors: Mackintosh David M. 
Published: May 2009

Turbidite sandstones interbedded with argillites are cut by veins composed of quartz and ankerite derived from host sandstones during successive phases of deformation.The existence of the oldest phase of deformation (F1) is established by the presence of its widespread vein system, which is folded by the F2 folds and cut by quartz veins of the later deformation phases.The nature of the veining, its mode of origin and regional significance are considered.
Secondary Gypsum in Middle Carboniferous Rocks of Spitsbergen
Authors: Holliday D. W. 
Published: May 2009

AbstractPorphyroblastic and alabastrine secondary gypsum from the Middle Carboniferous sequence of Central Vestspitsbergen is described. Evidence is presented to show that the earliest alabastrine gypsum formed from anhydrite by rapid, near-surface, volume for volume hydration, contrary to some previous explanations for similar secondary gypsum elsewhere.
Metamorphic zones and fault displacement in the Scottish Highlands
Authors: Chinner G. A. 
Published: May 2009

SummarySchemes of Scottish Caledonian metamorphic zonation involving the Thermal Anticline have traditionally been used for reconstructing movement on the Great Glen Fault. Interpretation of the highland zonal pattern in terms of inverted zones severally parallel to the Moine Thrust and to the Highland Border Fault, representing perturbation of isotherms by under-thrusting, can be fitted to either sinistral or dextral models of transcurrent motion.
The lithostratigraphical correlation of the uppermost Rhaetic and lowermost Liassic strata of the W Somerset and Glamorgan areas
Authors: Whittaker A. 
Published: May 2009

SummaryRichardson's (1911) detailed correlations of the Upper Rhaetic and Lower Lias strata of W Somerset are in need of revision; he wrongly identified the basal Langport Bed as the Cotham Marble at Blue Anchor and Lilstock. Likewise, his correlations of the Upper Rhaetic and Lower Lias strata between W Somerset and Glamorgan are erroneous; the lower parts of his Glamorgan Langport Beds were equated with the upper part of his W Somerset Cotham Beds. The greater part of the W Somerset Watchet Beds are, in the hand specimen, lithologically similar to Liassic shales and not to the White Lias ‘marly’ beds of Lavernock as he stated. The matter is important because the W Somerset coast is the recommended type area for the base of the Jurassic System, and Richardson&s classification of the strata is taken as the starting point for fixing this horizon.
The Precambrian–Cambrian boundary beds in Morocco (Preliminary Report)
Authors: Sdzuy K. 
Published: May 2009

SummaryIn the Anti-Atlas, trilobites occur below the zone of Fallotaspis tazemmourtensis of Hupé (1953) and even somewhat below the first archaeocyathids of the region. Most of them are opisthoparions (Hupetina gen.nov is described), and the olenellid Eofallotaspis gen.nov. probably is ancestral to Fallotaspis. The age is concluded not be younger than the lower Atdabanian of the Siberian platform. In the High Atlas, in the area called Ounein, a complete succession of trilobites from the low Lower Cambrian through the Middle Cambrian is being studied. The oldest trilobites encountered here are referred to the new genus Lemdadella. Correlation with the Anti-Atlas or other regions is uncertain.
Stromatolites from the Tiout section, Precambrian–Cambrian boundary beds, Anti-Atlas, Morocco
Authors: Schmitt M. 
Published: May 2009

SummaryStromatolites of the groups Linella, Tungussia and Tifounkeia in association with thrombolites occur in abundance throughout the whole Lie de Vin Series, the middle part of the Adoudounian Group which consists of Calcaire lnférieur, Lie de Vin Series and Calcaire Supérieur. A Late Precambrian age is suggested for these stromatolites.
The Precambrian–Cambrian boundary in parts of Scandinavia and Greenland
Authors: Poulsen Valdemar 
Published: May 2009

SummaryThe discovery of Ediacara type faunas and later the Tommotian fauna at levels below the supposed first appearance of trilobites has brought new life to the discussion of the formal position of the Precambrian–Cambrian boundary. The oldest shelly faunas are apparently restricted to a few favoured areas, whereas transition beds developed as quartz sandstones, mostly unfossiliferous apart from trace fossils, seem to have a much larger regional distribution. The sequences of quartz sandstones overlie a Precambrian crystalline basement of a much greater age or clastic sediments, in part tillites, and are in turn overlain by a variety of rocks containing olenellacean trilobites.The lowering to the Cambrian boundary makes the correlation of the widespread marine sandstones below levesl with trilobites highly pertinent. The correlation of some such sandstones in Greenland and Scandinivia is discussed below. In this account the Tommotial Stage is regarded as the basal Cambrian stage.
The Precambrian–Cambrian boundary problem: magnetostratigraphy of the Amadeus Basin, Central Australia
Authors: Kirschvink J. L. 
Published: May 2009

SummaryA magnetostratigraphic study of Upper Proterozoic to early Cambrian sediments at 4 localities in Central Australia reveals the presence of a magnetic polarity pattern composed of 2 long quiet intervals, first of reversed then of normal polarity, which is then succeeded by a long mixed interval. Lithologic comparisons suggest that this pattern is a reflection of the behaviour of the geomagnetic field at that time, and probably is not a result of varying sedimentation rates. Two sampled sections in the Arumbera Sandstone separated by 80 km both contain the long normal interval followed by the interval of mixed polarity, the detailed comparison of which demonstrates that the Arumbera-Box Hole boundary is unconformable. Elements from the late Precambrian Mt Skinner fauna in the Arumbera Sandstone indicate that the long normal interval is entirely pre-Cambrian, and that the base of the Cambrian occurs within the interval of mixed polarity.A comparison with an additional site sampled across a fossil occurrence in the Central Mount Stuart Formation at Central Mount Stuart indicates that at least 1 of the Upper Proterozoic fossils, Hallidaya brueri, has a considerable vertical distribution in time.If used properly, the magnetic polarity pattern discussed herein offers the possibility of precise intercontinental correlations of stratigraphic sequences near the base of the Cambrian. It is suggested that a stratotype sequence for the base of the Cambrian be chosen in such a manner that the boundary position corresponds to a geomagnetic reversal.
Coexisting silimanite and mullite
Authors: Cameron W. E. 
Published: May 2009

SummayIn three assemblages of widely differing paragenesis, sillirnanite and mullite have been found in apparently stable coexistence. This is interpreted as evidence for the presence of a miscibility gap between the two phases. A fourth occurrence, remini-scent of the early hydrothermal syntheses, is metastable.
Isostatic uplift and glacial history in northern Spitsbergen
Authors: Boulton G. S. , Rhodes M. 
Published: May 2009

SummaryThe pattern of crustal warping in northern Spitsbergen as a result of widespread deglaciation is plotted. This is facilitated by the occurrence on ancient strandlines of pumice fragments at 4 major horizons14C dated at 6500 (A), 6200 (B), 4100 (C) and 2200 yearsb.p.(D). Trace element analyses indicate an origin for the pumice in the Jan Mayen area. At least 2 pumice horizons are thought to be contemporaneous with eruptions at 6500 and 4100 yearsb.p.
Fission track ages of biotites from crystalline rocks of Khammam district, Andhra Pradesh, India
Authors: Nagpal M. K. , Powar K. B. , Nagpaul K. K. 
Published: May 2009

SummaryA modified fission track technique has been used for datingbiotite flakes from crystalline rocks of Khammam district in Andhra Pradesh, India. The recorded fission track ages of 368±15 Ma to 616±20 Ma, with a mean of 475±90 Ma, correspond to the period of the Indian Ocean cycle. The data suggest an average cooling rate of about 0.6 °C per million years for the closing phase of this cycle.
An outcrop of pre-Silurian rocks near Bishop's Castle (S of the Shelve inlier) Salop, England
Authors: Davies J. H. 
Published: May 2009

SummaryA previously undescribed series of outcrops which lies nearBishop's Castle, 3.2 km S of the Longmynd-Shelve Area of Salop (Shropshire), displays a relationship between the Western Uriconian tuffs, WentnorSeries ashy turbidites (both Pre-Cambrian) and Ludlow Series siltstones. This throws further light on the structure of the Pontesford-Linley Disturbance, indicating that, in the vicinity of the outcrops, a component of its movement may have been post Ludlow in age.
Time Scale and Ice Accumulation During the Last 125,000 Years as Indicated by the Greenland 018 curve
Authors: Mörner N. A. 
Published: May 2009

SummaryThe 18 curve from the 1390 m long ice core from Camp Century, Greenland, shows climatic changes that are easily correlated with known glacial and non-glacial events of North America and north Europe and are thus indirectly dated. With a known chronology, the glacial dynamic changes of the Greenland Ice Sheet can be calculated for the last 125,000 years. It is concluded that the dynamics of the Greenland Ice Sheet have changed drastically during this period and that these changes are directly related to major changes of climate and extension of the Wisconsin and Weichselian glaciations. Logarithmic time scales earlier applied to this curve must therefore be incorrect.
Myrmekites of Exsolution and Replacement Origins
Authors: Ashworth J. R. 
Published: May 2009

SummaryMyrmekite in a two-feldspar migmatite suite has two distinct modes of occurrence: (i) marginally embaying potash feldspar, and (ii) in replacement aggregates after that mineral, the other major constituent of the pseudomorphs being a muscovite-quartz intergrowth. Electron-probe data give quartz proportionalities agreeing with the predictions of existing theories. It is shown that these theories, which refer to either exsolution or small-scale metasomatism, share a common foundation of kinetic impediment to AlSi diffusion. In neither case need one assume the presence of ‘Schwantke's molecule’ as a component of potash feldspar. The two myrmekite occurrences here described are interpreted in terms of essentially simultaneous exsolution and hydrative replacement processes operating as regional metamorphic temperatures began to decline from their climactic values. The existence of exsolution myrmekites of ideal quartz proportionality is not in itself evidence for the existence of ‘Schwantke's molecule’.
On a varcus Zone conodont fauna from the Ilfracombe Slates (Devonian, North Devon)
Authors: Orchard M. J. 
Published: May 2009

SummarySeveral conodont faunas from the Ilfracombe Slates are described and their age discussed. One is referred to the conodont zone of Polygnathus varcus (late Givetian-early Frasnian). The conodonts, the first from the Devonian of North Devon, indicate that, in terms of the German standard, the uppermost Ilfracombe Slates are no younger than basal Manticoceras Stufe in age. The position of the Middle/Upper Devonian boundary within the North Devon sequence is discussed with reference to the limestones of the Combe Martin Slates (the ‘Ilfracombe limestones’), which are regarded here as Middle Devonian in age.
Pahoehoe and pillow lavas from the Suguta Trough, South Turkana, Kenya
Authors: Truckle P. H. 
Published: May 2009

SummaryThe pahoehoe and pillow lavas described show many common features of morphology. A finger-like or digital flow mechanism adequately accounts for the similarities although the growth mechanism of individual lobes is by markedly different processes. An important distinction is the time taken to develop a rigid crust and its subsequent expansion by fracturing and auto intrusion. This is rapidly achieved in pillow lavas but only occurs at a late stage in the pahoehoe forms. The main factors controlling the formation of these features are the environment of eruption, the volume of erupted material and the rate of eruption.
A displaced Tibetan massif as a possible source of some Malayan rocks
Authors: Crawford A. R. 
Published: May 2009

SummaryExplanations (Burton, 1970; Ridd, 1971) of the westerly origin of the sediments now forming the rocks of northwest Malaya, by deriving them from an India which once lay contiguously against Malaya are unacceptable because of the complexity of the movement of Gondwanic India and the known history of the Indian Ocean. The effects of the movement of India into Asia were such that the Tibetan part of the orogen which continues south through Yunnan into Malaya was distorted. Before the arrival of India the Tibetan massif also may have lain still further away from the rest of Asia and moved towards the Siberian Platform by sea-floor spreading in the Tethys, so that its erosion could have provided material now forming part of Malaya. The Tibetan–Yunnan–Malay orogen has a complex and probably sutured form.
The ultramafic—mafic complex at North Cape, northernmost New Zealand
Authors: Bennett M. C. 
Published: May 2009

SummaryThe ultramafic—mafic complex at North Cape lies in a Mesozoic—Lower Tertiary tectonic belt linking New Zealand with New Caledonia and Papua New Guinea. The complex is faulted against Cretaceous submarine tholeiites and contains (1) serpentinized harzburgite and lherzolite of probable cumulus origin (and intruded by more Fe-rich wehrlitic veins and dykes), overlain by (2) layered olivine- and orthopyroxene-gabbro subvolcanic cumulates which are themselves host for (3) a sheeted dyke swarm of mainly quartz-diorite composition. It is suggested that the complex was emplaced with the Cretaceous volcanics by obduction of Mesozoic oceanic crust during the Lower Tertiary.
Garnet-biotite relationships in high grade metamorphic rocks at Broken Hill, Australia
Authors: Plimer I. R. 
Published: May 2009

SummaryGarnets and biotites from pelitic, psammitic and quartzofeldspathic rock enclosing the Broken Hill orebodies are sensitive to syn and post high grade metamorphic metasomatism associated with orebody-wall rock reactions but the overall garnet—biotite partitioning relationships remain unchanged. KMg-FeDgarnet-biotite and metamorphic grade calculations increase from NW to SE over the 1000 m section examined which is in accord with the regional grade variation.
Radiometric age of the Monograptus cyphus graptolite zone in Southeastern Alaska — an estimate of the age of the Ordovician—Silurian boundary
Authors: Lanphere M. A. , Churkin M. , Eberlein G. D. 
Published: May 2009

SummaryK—Ar age measurements on Esquibel Island, southeastern Alaska yield a minimum age of about 433±3 Ma for the Zone of Monograptus cyphus of the Lower Silurian. An age of approximately 435—437 Ma is estimated for the Ordovician—Silurian boundary.
Temporary exposure of the Middle Cambrian, Warwickshire, England
Authors: Cook A. F. 
Published: May 2009

SummaryA temporary exposure of the Abbey Shales at Vernons Lane, Nuneaton, yielded a lower Paradoxides davidis fauna. The absence of the upper Paradoxides davidis fauna confirms the southerly overstep of the Abbey Shales by the overlying Mancetter Grits and Shales. Well-preserved fragments of Clarella impar (Hicks) and Tomagnostus gracilis (Illing) are illustrated.
Volume increase serpentinization in Archaean quench texture ultramafic rocks near Kalgoorlie, Western Australia
Authors: Moeskops P. G. 
Published: May 2009

SummaryTextural and chemical data on altered ‘spinifex’ (i.e. quench texture) ultramafic rocks from Corsair, near Kalgoorlie, Western Australia, have indicated that serpentinisation of contained olivine phenocrysts involved a volume increase of some 60%, due to the addition of both SiO2 and H2O.
The Triassic-Jurassic boundary in Great Britain
Authors: Poole E. G. 
Published: May 2009

SummaryIt was recently proposed that the base of the Jurassic system be taken at the base of the Blue Lias in the Watchet area of Somerset thus including the underlying White Lias in the Triassic System. The mapped base of the Blue Lias however is a diachronous horizon ranging from pre-planorbis Beds age in Somerset to Schlotheimia angulata Zone age in Warwickshire. No certain chronological correlation is possible between the base of the Blue Lias in the Watchet area and any limestone or other horizon in the pre-planorbis Beds elsewhere nor is there even a palaeontological separation associated with this horizon. This paper reiterates established Geological Survey practice of taking the Triassic-Jurassic boundary in Great Britain at the top of the Cotham Beds and thus including the White Lias limestones in the Lower Lias. The White Lias limestones are regarded as a local shallow-water facies of the pre-planorbis Beds since they both contain similar non-ammonitiferous marine macrofossil assemblages;the Cotham Beds provide palaeontological separation since they divide theseassemblages from the different marine macrofossil assemblages found in the Lower Rhaetic Westbury Beds and also contain the boundary between the Rhaetipollis and Heliosporites miospore zones. The lacustrine or lagoonal Cotham Beds are similar in lithology to the Tea Green Marl and also include reddened beds of mudstone like those of the Keuper Marl; they are therefore better contained in the continental Triassic system rather than the marine Jurassic system.
Microstructures in titanomagnetites as guides to cooling rates of a Swedish intrusion
Authors: Price G. D. 
Published: May 2009

SummaryIron-titanium oxides from Taberg in Sweden exhibit under the electron microscope several microstructural features not visible when studied by optical microscopy, including homogeneous nucleation of magnetitess from ulvöspinelss, and the spinodal decomposition of magnetitesss. Such microstructures have promise as indicators of cooling rates.
The tectonic significance of basalts and dacites in the Wagwater Belt, Jamaica
Authors: Jackson T. A. , Smith T. E. 
Published: May 2009

SummaryThe Wagwater Belt is a fault-bounded structural unit in which more than 3000 m of early Tertiary sedimentary and volcanic rocks are exposed. Geochemical analyses of the volcanic rocks show that they comprise a bimodal suite of plateau-type tholeiitic basalts and calcalkaline dacites. The extrusion of these volcanics is associated with the development of an interarc basin, the Wagwater Basin, at the beginning of the Cenozoic Era. The Wagwater Basin formed as a result of the splitting of a mature late Cretaceous volcanic arc into a frontal and third arc represented by the Blue Mountain Massif and the Clarendon Block respectively. This model for Jamaica can be correlated with tectonic events occurring in the NW Caribbean during the early Tertiary. The creation of the Wagwater Basin and the eruption of the basalts is related to the initial opening of the Cayman Trough. The cessation of dacite volcanic activity in Jamaica signified the separation of the Caribbean Plate from the East Pacific Farallon Plate.
The debated age of the ammonoid Durvilleoceras Waterhouse
Authors: Waterhouse J. B. 
Published: May 2009

SummaryAlthough the ammonoid Durvilleoceras is apparently very close in its morphology to early Triassic genera, it comes from a formation that underlies formations with early Triassic and late Permian faunas, and appears to be of late Middle Permian age. New occurrences of the ammonoid support this thesis. Conjecturally, the genus may have inhabited deep cold waters of the southern hemisphere during the Permian Period, before giving rise to genera found in shelf deposits of the early Triassic. Alternatively, if really Triassic in age, Durvilleoceras indicates a major low-angle thrust, previously unsuspected, that has repeated Triassic sequences for a length of over 450 km before disruption by the Alpine Fault. No evidence is yet known to support this alternative.