bluuebunny/crossref_metadata_2025 huggingface dataset:
The analysis of en-échelon veins
Authors: Hancock Paul L.
Published: May 2009

Measurements of en-échelon veins cutting small chevron folds in Carboniferous greywackes, near Hartland in Devon, allow the following new conclusions about naturally occurring second-order fractures to be stated. 1. Veins may be initiated between 10° and 46° to the shear zone in which they occur. Previous studies of en-échelon fractures have generally classified them as either tension gashes formed at 45° to an array, or Riedel shears at 15° to an array. 2. Veins at about 20° to 40° to an array probably occupy surfaces which are transitional between shear and extension fractures. 3. Proof of a component of shear, in addition to dilation, on many of the veins at less than 40° to an array is provided by crystal fibres at acute angles to vein margins, and third-order en-échelon veins in arrays which are parallel to and part of a set of second-order veins.
Correlation of Lower Pleistocene Crag at depth in Suffolk
Authors: Beck R. B. , Funnell B. M. , Lord A. R.
Published: May 2009

The 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.
Polyphase deformation structures in the Welsh Caledonides near Aberystwyth
Authors: Fitches W. R.
Published: May 2009

Various small-scale tectonic structures which deform the first, regional folds and cleavages are described. The strain sequence in the rocks near Aberystwyth is shown to resemble that established elsewhere in the paratectonic Caledonides.
Hollow apatites in a layered basic intrusion, Norway
Authors: Gardner P. M.
Published: May 2009

Cumulate 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

The 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

The 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

The 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

Porphyroblastic 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

Schemes 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

Richardson'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

In 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

Stromatolites 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

The 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.
Late Precambrian to early Cambrian stratigraphy of the SW Georgina Basin, Australia
Authors: Walter M. R.
Published: May 2009

The area to the N and NE of the Amadeus Basin in central Australia is currently being studied by the Bureau of Mineral Resources as part of a detailed investigation of the Georgina Basin. This has led to the recognition of numerous rock units within a previously undifferentiated latest Precambrian to early Cambrian sequence, and preliminary correlations with the Amadeus Basin are possible. The sequence starts with the lower of the 2 late Precambrian tillites, and includes stromatolitic carbonates and ichnofossiliferous sandstones. These outcrop on the Hay River, Tobermory and Huckitta 1:250000 sheet areas. No early Cambrian carbonates are yet known from the eastern region, but occur on Huckitta in the Mount Baldwin Formation and in the Amadeus Basin in the Todd River Dolomite. These contain early Cambrian shelly fossils. It is tentatively suggested that the late Precambrian–early Cambrian sediments of the SW Georgina Basin are the platform equivalents of the basinal sediments of the Amadeus Basin, with fully marine sediments of this age occurring in the Georgina Basin only in NW–SE trending grabens that cut across the platform.
The Precambrian–Cambrian boundary problem: magnetostratigraphy of the Amadeus Basin, Central Australia
Authors: Kirschvink J. L.
Published: May 2009

A 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

Summay

In 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.
The formation of rift valleys and their zigzag fault patterns
Authors: Freund R. , Merzer M.
Published: May 2009

The formation of a rift valley and its zigzag fault patterns is simulated by a model experiment. A stress analysis of the model shows how the rift valley and its fault pattern are formed on two oppositely inclined boundaries in the stress field.
Isostatic uplift and glacial history in northern Spitsbergen
Authors: Boulton G. S. , Rhodes M.
Published: May 2009

The 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

A 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

A 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

The 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

Myrmekite 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

Several 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

The 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

Explanations (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

The 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

Garnets 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

K—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

A 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

Textural 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

It 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

Iron-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.
John Woodward; ‘A Droll Sort of Philosopher’
Authors: Porter Roy
Published: May 2009

[The following is the text of a lecture delivered in Cambridge on 19 October 1978 to mark the 250th anniversary of the founding of the Woodwardian Chair.]
The tectonic significance of basalts and dacites in the Wagwater Belt, Jamaica
Authors: Jackson T. A. , Smith T. E.
Published: May 2009

The 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

Although 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.
Description in the geological sciences and the Lithostratigraphic Descriptive System, LSDØ2
Authors: Odell John
Published: May 2009

A discussion of geological description and an account of the Descriptive System LSDØ2 are given. It is shown that by examination of the aims of description and of its main instrument, the geological observer, a set of principles and objectives may be established in order to design descriptive systems. The application of these principles is demonstrated by an account of the theory and practical aspects of the Lithostratigraphic Descriptive System LSDØ2.
A quantitative analysis of an Upper Westphalian fluviodeltaic succession and a comparison with earlier Westphalian deposits in the Kent Coalfield
Authors: Read W. A.
Published: May 2009

The Upper Westphalian succession in the National Coal Board's Eastling Wood Borehole, 1976 ‘TR 6303 1472’ has been analysed in terms of upward-fining and upward-coarsening semicycles, transition probabilities and entropies. This analysis confirms that the succession can be divided into a lower coal facies, which like the earlier Westphalian deposits of Kent was laid down dominantly in deltas but which includes numerous channel-fills, and an upper channel facies laid down in a more upstream fluvial environment.
Chloritoid-staurolite assemblages from Barrow's Zones in Central Perthshire, Scotland
Authors: Atherton M. P. , Smith R. A.
Published: May 2009

Chloritoid-biotite- and chloritoid-staurolite-bearing rocks occur around Blair Atholl, Perthshire. Textures suggest staurolite to be produced from chloritoid by a prograde ionic reaction involving muscovite. Chloritoid rocks are aluminous, lying above the muscovite-chlorite join, and staurolite formation involves the breakdown of chloritoid and muscovite. Their presence indicates that the chloritoid-biotite zone of Stonehaven continues as far SW as Central Perthshire, although its occurrence is severely limited by a lack of aluminium-rich rocks. The use of the chloritoid outcrop in the NE as an indication of pressure decrease to the SW is therefore queried.
The inadunate crinoid genus Cryphiocrinus Kirk
Authors: Strimple Harrell L.
Published: May 2009

Cryphiocrinus Kirk is a genus which may possess a delicate stem, or may lose the stem as an adult, making it essentially eleutherozoic. C. girtyi Kirk, type species, is documented with certainty from Chesterian rocks of Oklahoma and Arkansas for the first time. C. rotundus Kirk is reported from the Renault Formation of Illinois and a possible occurrence in the Pride Mountain Formation of Alabama is noted. The genus has previously been recognized in Chesterian, Upper Mississippian, (Lower Carboniferous), strata exposed in West Virginia, Kentucky and Oklahoma, U.S.A. Possible affinity with Hosieocrinus Wright from the Lower Limestone Group (Visean) in Scotland is discussed.
The Wolf Rock, Cornwall: new chemical, isotopic age and palaeomagnetic data
Authors: Harrison R. K. , Snelling N. J. , Merriman R. J. , Morgan G. E. , Goode A. J. J.
Published: May 2009

By systematic sampling (including the drilling of orientated cores) new data are presented on the chemistry, petrography, mineralogy, K/Ar isotopic age and remanent magnetism of the Wolf Rock, Cornwall. The overall homogeneity of the Rock is confirmed as a fine-grained fluxioned microporphyritic phonolite. Major joints strike NNW–SSE and NNE–SSW and there is a pronounced floor jointing. New whole-rock and probe analyses of the constituent minerals are given. Nosean, previously recorded, is found to be replaced by analcime, cancrinite and other minerals. K–Ar determinations on nepheline and K-feldspar give mean ages of 112±2, and 130±6 Ma respectively. The mean pole position of 70° N, 6° E, suggests that the 130 Ma pole for stable Europe may have been somewhat closer to Europe than previously supposed. The significance of this Lower Cretaceous magmatism in the context of Mesozoic volcanism in Southern England and European alkaline provinces is discussed.
The basic rock series in batholithic associations
Authors: Mullan H. S. , Bussell M. A.
Published: May 2009

Basic rocks from the West Mexican Batholith and the Coastal Batholith of Peru are described. These are considered representative of the whole range of basic rocks in batholiths and their crystallization and subsequent history is related to the fluid pressure of the magma. Their role in batholithic evolution is discussed.
Origin of montmorillonite in the early Jurassic shales of NW Scotland
Authors: Amiri-Garroussi K.
Published: May 2009

Clay mineral analysis of shales in the early Liassic Lower Broadford Beds of the Hebrides reveals the presence of abundant quantities of montmorillonite whereas the Upper Broadford Beds contain illite, kaolinite and subordinate mixed layer minerals together with chlorite. Montmorillonite enrichment of the Lower Broadford Beds as a consequence of recent weathering contamination by doleritic sills can effectively be ruled out. It is argued that the montmorillonite may have been derived from the weathering of basic igneous rocks exposed in the sediment source area during Late Triassic times. By Upper Broadford Beds times, the igneous source was either eroded away or transgressed by the early Liassic sea.
K–Ar and Rb–Sr isotopic age studies on the Wolf Rock nosean phonolite, Cornwall
Authors: Mitchell J. G. , Macintyre R. M. , Pringle I. R.
Published: May 2009

Potassium–argon and rubidium–strontium isotopic age studies of the Wolf Rock phonolite of SW England confirm its age as 131 Ma, with an initial87Sr/88Sr ratio of 0.703. The existence of a Mesozoic volcanic province of this age on the margin of the Labrador–Biscay rift is discussed with special reference to its implications for the early evolution of the N.Atlantic Ocean, and the general relationship of alkaline igneous activity to major periods of plate reorientation.
Rocks of unusual chemistry in the charnockitic terrains of India, and their geological significance
Authors: Viswanathan S.
Published: May 2009

The paper reports the occurrence in the 2.9–3.1 B.Y. old charnockitic terrains of Southern India of some basic charnockites that are strikingly similar, chemically, to basaltic komatiite from the 3.4 B.Y. old Barberton greenstone belt of Southern Africa, and suggests that the pre-metamorphic evolution of Archaean charnockitic terrains followed the same trends that characterized the development of Archaean greenstone belts. The main events in the evolution of one such terrain, the ‘Madras granulite belt’, before it was subjected to granulite facies meamorphism some 2.6 B.Y. ago, is outlined in Table 2.
Tectonic control on the formation of some fibrous quartz veins, Mid-Wales
Authors: Garth Raybould J.
Published: May 2009

Protoquartzites outcropping in a small anticline in the Plynlimon area of mid-Wales contain numerous flat-lying and low-angle, fibrous quartz veins, which are subparallel to the ab plane of the fold. The quartz crystals are elongated at a high angle to the vein walls, and in some cases exhibit a curvature which is thought to have been adopted as the crystals grew. The orientation and internal structure of the veins suggest that they formed on fractures initiated during compression and extended by hydraulic fracture, the crystal curvature being a result of shearing during syntectonic crystal growth. Pore water was important both in bringing about the critical effective stresses required for fracturing and as a carrier of locally remobilized free silica.
A Cretaceous laterite in the Negev Desert, southern Israel
Authors: Singer A.
Published: May 2009

Kaolinite is the major mineral in the saprolite of a fossil laterite, found intercalated amid basalt flows from the Lower Cretaceous in the Negev desert. The kaolinite was produced by pseudomorphic alteration of plagioclase. Haematite is a secondary product and accumulated in a ferruginous soil horizon. In the saprolite Sr, Mn and Cu were strongly depleted, Zn and Ni were slightly depleted, whereas Co and Cr accumulated. In the ferruginous horizon, Sr, Mn, Cu and Zn were severely depleted, while Cr and Ni accumulated. The lateritic formation is evidence for the possible existence of tropical or intertropical conditions during the Lower Cretaceous in the Negev.
Textural patterns at porphyroblast margins and their use in determining the time relations of deformation and crystallization
Authors: Ferguson C. C. , Harte B.
Published: May 2009

Textural patterns characteristic of supposed pre-, post- and to a lesser extent syn-tectonic porphyroblasts are reviewed. Difficulties of interpretation arise where anSi(internal schistosity) is absent, andSe(external schistosity) behaviour adjacent to porphyroblast margins is the only available criterion; examples may be found showing truncation ofSeby pre-Seporphyroblasts. Truncation and/or deflection textures are not by themselves sufficient criteria for determining the time relations of particular phases of deformation and crystallization.
Protosuchus, Proterochampsa, and the origin of phytosaurs and crocodiles
Authors: Walker A. D.
Published: May 2009

Study of casts ofStegomosuchus, a small reptile from the Upper Trias of the Connecticut Valley, hitherto regarded as a pseudosuchian thecodont, suggests that the skull ofProtosuchusincludes two pairs of supraorbital bones, and as a consequence the narrow interorbital region indicates a closer relationship to the South African genusNotochampsathan has previously been thought. These three genera of late Triassic crocodilians are placed in the family Stegomosuchidae von Huene, 1922.Proterochampsa,from the Ischigualasto Formation of Argentina, described by Reig (1959) and Sill (1967) as an ancestral crocodile, is considered to be an extremely primitive phytosaur.
The stratigraphy of a geosynclinal succession in western Sierra Leone, West Africa
Authors: Allen P. M.
Published: May 2009

The Rokel River Series of Sierra Leone is re-defined, and subdivided into the Rokel River Group and the Taban Formation. The Rokel River Group consists of six formations which represent the development and infilling of an eugeosyncline, and has been mildly metamorphosed and folded at least three times. The Taban Formation contains fluvial sediments deposited after orogenesis.
Drumlin measurements: a test of the reliability of data derived from 1:25000 scale topographic maps
Authors: Rose J. , Letzer J. M.
Published: May 2009

Measurements have been made on drumlins from the Glasgow district and eastern Westmorland, using 1:25000 topographic maps and direct field mapping. Comparison of the results suggests that topographic maps provide data which varies in accuracy with the clarity of the drumlin pattern depicted by the map, and the character of the particular descriptive parameter. Dimensionless parameters such as elongation ratio, tapering value (k), and stoss-point ratio are most accurately estimated, but size, spacing and density are consistently inaccurate, and the number of drumlins recognized is, at best, only 50 % of the number of drumlins that exist in the field. It is suggested that topographic maps fail to give information at the precision level required for the analysis of this type of glacier bedform.
The stratigraphy of Barbuda, West Indies
Authors: Brasier M. D. , Mather J. D.
Published: May 2009

The geology of Barbuda, a low-lying island in the Lesser Antilles, is reexamined and the stratigraphy is revised. The oldest rocks are limestones of the Highlands Formation, a Middle Miocene accumulation of fore-reef facies. This is overlain successively by the Pleistocene Beazer and Codrington Formations, limestone accumulations of reefal, lagoonal and dune facies. The Holocene Palmetto Point Formation is comprised of extensive beach ridge and dune limestones. From this, the Barbuda Bank (which includes Antigua) is considered to have had a geological history like the neighbouring Anguilla and Guadeloupe Banks.
The morphology and systematics of ‘Didymograptus’ spinosus Ruedemann, 1904, and allied species from the Lower Ordovician
Authors: Archer J. B. , Skevington D.
Published: May 2009

The first European occurrence of ‘Didymograptus’ spinosus Ruedemann, 1904, is reported. A re-description of this species is provided, based on the lectotype and new material from the West of Ireland. ‘D.’ spinosus is shown to possess the essential characteristics of the genus Holmograptus Koztowski, 1954, to which it is accordingly referred.

Didymograptus nodosus Harris, 1926, and Tylograptus regularis Mu, 1957, together with certain other species of Tylograptus described by Mu (1957), are junior synonyms of Holmograptus spinosus. Holmograptus Kozlowski, 1954, is a senior synonym of Tylograptus Mu, 1957.
The greenschist facies assemblages of the lower Kumaon Himalaya
Authors: Das B. K.
Published: May 2009

The mineral assemblages of the pelitic rocks of the chlorite and biotite zones of the Kumaon Himalaya are characteristic of the quartz–albite–muscovite–cnlorite and quartz–albite–epidote–biotite sub-facies of the greenschist facies. The appearance of garnet in the sericite–chlorite pelites is due to bulk composition which plots above the muscovite–chlorite join in the AKF diagram. The variation in composition of coexisting sericite and chlorite is related to bulk composition of the rock.
An Upper Mesozoic island-arc–back-arc system in the southern Andes and South Georgia
Authors: Suárez M. , Pettigrew T. H.
Published: May 2009

The Upper Jurassic–Lower Cretaceous strato-tectonic belts of the southern Andes and South Georgia, 2000 km apart, can be correlated and explained as the products of an island-arc–back-arc system. From the Pacific Ocean to the Atlantic, these belts, which exhibit structural and metamorphic differences, are: (1) a pyroclastic belt developed on an ensialic volcanic arc; (2) a back-arc flysch sequence underlain in the southern Andes by a basic complex with oceanic affinities; this was intruded into continental crust as a result of sea-floor spreading which created a marginal basin; (3) a slate sequence deposited on a continental shelf. The pyroclastic and marginal basin belts and the adjacent part of the continental shelf were folded and uplifted during the early Upper Cretaceous, whereas the foreland part of the continental shelf assemblage underwent deformation during the early Tertiary.
Rock composition, density and a variation diagram
Authors: French W. J.
Published: May 2009

The relationship between silicate rock density and composition has been investigated and empirical formulae have been obtained that give a factor equivalent to a ‘normative’ density. Comparison between this factor and measured density may provide useful diagrams assisting the interpretation of metamorphic petrogenesis. The factor itself is a viable differentiation index aiding comparison between the compositions and liquidus temperatures of volcanic suites.
The significance of the melting interval of basaltic magmas at various pressures
Authors: Maaløe S.
Published: May 2009

The melting intervals of basaltic magmas are investigated in detail at various pressures, as the size of the interval has an important bearing on the genesis of igneous rocks. Tholeiitic magmas do not have a more pronounced four phase proximity at low pressures than at higher ones. This result seems to oppose the generally accepted low pressure character of these magmas; but as there is a general decrease in melting intervals with increasing pressure, the four phase proximity is nevertheless sustained. The melting intervals of alkaline rocks decrease rapidly with increasing pressure. Small variations in the temperature may therefore generate large variations in the composition of the liquids developed at high pressures.
The Garnedd-wen Formation (Ashgillian) of the Towyn-Abergynolwyn district, Merionethshire
Authors: James D. M. D.
Published: May 2009

A lithostratigraphy is described and related to that in the adjacent Corris-Machynlleth district. Thickness of the Formation is estimated to be c. 500 m near Towyn rather than c. 1000 m as generally accepted, although poor exposure precludes accurate determination. Palaeocurrent data are given for a prominent interval of turbidite arenites, here termed the Llyn Barfog Member. Sedimentary facies are interpreted as slope-base and deep basinal deposits and are consistent with control of sedimentation by the Bala and Corris ‘basement faults’.
Aschemonella longicaudata sp. nov. from the Permian of Derbyshire, England
Authors: Anderson F. W.
Published: May 2009

A foraminiferal fauna in the Lower Permian Marls of the Lowpit Lane Borehole, Derbyshire, included numerous examples of a new species of the genus Aschemonella Brady. This is described as Aschemonella longicaudata sp. nov. and the possible growth form of the genus is discussed.
Ostracoda of the Genera Eucytherura and Cytheropteron from the Speeton Clay
Authors: Kaye Peter
Published: May 2009

Nine species of ostracoda belonging to the genera Eucytherura and Cytheropteron are described from the Speeton Clay at its type locality. Eight of these species are described for the first time; the ninth species is recorded for the first time from Europe.
Faulting of the sub-Carboniferous Surface in Eastern Murrisk, Co. Mayo
Authors: McManus John
Published: May 2009

The presence of pre- and post-Carboniferous structures in Murrisk is noted. Warping of the sub-Carboniferous surface in the eastern part of the Partry Mountain area is ascribed to NE-trending normal faults.
Differential Retrogressive Metamorphism in Granulites of the Karasuk Group, Karamoja, Uganda
Authors: Clark Lewis
Published: May 2009

The Karasuk Group comprises a series of meta-sedimentary rocks of the amphibolite facies with localized areas of granulites. The granulites have been subjected to retrogressive metamorphism, and acid granulites are much more retrograded than associated basic granulites. It is suggested that this differential retrogression of the granulites is related to differing susceptibilities of the two types to the penetrative deformation to which they have been subjected.
Tholeiite and Tholeiitic Series
Authors: Tilley C. E. , Muir I. D.
Published: May 2009

The restrictions proposed by Jung (1958) on the definition and use of the term tholeiite, and the more recent drastic proposal for its abandonment (Chayes, 1966) are considered. Both proposals are rejected and re-emphasis given in support of the broad use of the term both as a rock and magma type, and as a progenitor of an igneous rock series.
Sections in the Beach-plain Deposits of Dungeness, Kent
Authors: Hey R. W.
Published: May 2009

Recent excavations on Dungeness have provided excellent sections through the deposits of its late Holocene beach-plains. The material at the surface is loose shingle, but at a depth of a few feet this passes down into gravel packed with sand. The gravel in turn rests upon almost stoneless sand with marine shells, the contact between the two deposits falling from - 13 feet O.D. in the most northerly section to - 24 feet in the most southerly.

It is confirmed that the more pebbly deposits were laid down on an actively prograding foreshore, as has generally been supposed. Problems are raised, however, by the low levels of their base and by some of their structural and lithological features. These are discussed, and explanations are offered where possible.
Sedimentary Infillings of Fossils and Cavities in Limestone at Treak Cliff, Derbyshire
Authors: Broadhurst F. M. , Simpson I. M.
Published: May 2009

Observations of partial and complete sedimentary infillings of fossils and rock cavities at two localities on Treak Cliff, Castleton, Derbyshire, lead to the conclusion that at these localities the present dip of the limestones is largely or entirely depositional in origin. This conclusion agrees, more or less, with claims made in previous publications but, so far as the authors are aware, this is the first time that direct evidence of high initial dips at Treak Cliff has been recorded.
Order of Abundant Crystal Nucleation in a Natural Magma
Authors: Hawkes D. D.
Published: May 2009

Rhythmic layering in the Freetown Complex and in some other layered intrusions may be due to the different powers of nucleation of the primary minerals from an undercooled magma. It is suggested that, in slowly cooled intrusions, the total number of crystals per cm3 in a rock (whole rock index) is a measure of the amount of undercooling; rocks with a low whole rock index crystallized at or near the equilibrium temperature while rocks with a high index crystallized under conditions of undercooling. If this is so, then it is possible to determine the order of abundant nucleation of the primary minerals by graphical means. Only a slight amount of undercooling, perhaps of the order of 4 or 5° C, is necessary to produce marked changes in the order of separation of the minerals from the magma.
The Jurassic and Cretaceous Sequence in Spitsbergen
Authors: Parker J. R.
Published: May 2009

The Jurassic and Cretaceous sequence of Spitsbergen, Svalbard archipelago, is described and a revised lithostratigraphical scheme, of four formations, is proposed. The main episode of tectonic activity, together with dolerite intrusion, was in late Jurassic-early Cretaceous times and is represented by a non-sequence and local unconformity between the two lower formations. The faunal succession is also discussed.