bluuebunny/crossref_metadata_2025_split huggingface dataset:
An outline of the stratigraphy and palaeontology of the Ordovician rocks of Central Portugal
Authors: Mitchell W. I. 
Published: May 2009

SummaryWell-preserved brachiopod faunas collected from four Ordovician horizons range in age from Upper Llanvirn to Lower Caradoc. The generically restricted Upper Llanvirn and Lower Llandeilo assemblages are associated with diagnostic graptolites. In contrast the Upper Llandeilo and Lower Caradoc assemblages are more diverse and correlate well with faunas from the more precisely dated Chrustenice Substage in Bohemia. Two new brachiopod genera Apollonorthis and Cacemia are described.
A contribution to the geology of the western margin of the Afar Depression, Ethiopia
Authors: Brooks D. J. 
Published: May 2009

SummarySatellite imagery provides additional support for the published geology of the eastern escarpment of the Ethiopian plateau. However, of greater interest is that inspection of the imagery reveals aspects of the regional geology that have gone unnoticed. The most obvious are used to extend fault lines discussed by Kazmin & Garland (1973).
Discovery of a Tin-tungsten Mineralization in Northern Khartoum Province, Sudan
Authors: Almond D. C. 
Published: May 2009

AbstractA primary deposit of tin and tungsten has been discovered in association with granites of the Cambrian (?) sub-volcanic igneous complex at Sabaloka, on the Nile north of Khartoum. Wolfram and cassiterite occur in a stockwork of quartz veins which also contain minor amounts of sulphide minerals. The stockwork centres around a small intrusion of primary greisen lying on the contact of a porphyritic microgranite ring-dyke but the greisen and mineralizing solutions are believed to have originated from a nearby mass of biotite-muscovite granite. The deposit has many features in common with the primary tin veins associated with the Younger Granites of northern Nigeria and other parts of northern Africa.
A Photometric Method for the Determination of Preferred Orientation in Thin Sections of Crystal Aggregates
Authors: Durrance E. M. 
Published: May 2009

AbstractPhotometric recording of the variation in intensity of light transmission by the analyser of a petrological microscope whilst the polarizer is rotating at a rate sufficient to eliminate the periodic output from the photocell as the polars cross and uncross, and a thin section of a crystal aggregate is slowly rotated upon its stage, is found to yield information on the direction and degree of development of any preferred optical orientation that may be present in the section. The theory of the method is considered and an equation derived for the representation of any preferred optical orientation in terms of a direct percentage of areal extent. The direction of the preferred orientation is found to be parallel to the plane of polarization of the stationary analyser when the section is rotated to a position of minimum intensity of light transmission. It is suggested that the method has potential applications in the study of any fabric which is displayed in terms of an optical orientation.
Possible higher pressure relics within titaniferous augites in a basic sill
Authors: Gibb F. G. F. , Henderson C. M. B. 
Published: May 2009

SummaryAn unusual type of mottled area is described from titaniferous augites in the Dippin sill, Isle of Arran. These are characterized by abundant magnetite inclusions, irregular embayed outlines and distinctive chemical compositions. The possibility that these are due to zoning, especially sector zoning, is examined and discarded. They probably represent partly resorbed relics of pyroxene which crystallized at depth prior to the emplacement of the sill. As such they could have considerable petrogenetic implications both with regard to the sill itself and to alkaline basic magmas in general.
Lava trees and tree moulds as indicators of lava flow direction
Authors: Lockwood J. P. , Williams I. S. 
Published: May 2009

SummaryLava trees and tree moulds are common in many areas where fluid basaltic lava has moved rapidly over forested terrain. Lava trees are formed only by thin flows, but tree moulds are preserved in both thin and thick flows. Both structures may indicate the direction of flow of the lava in which they are preserved. The usefulness of lava trees in this regard is limited to recent flows; tree moulds, however, have been described in rocks as old as middle Tertiary. Features commonly well preserved on the inner walls of moulds indicate the local flow direction. When found in sufficient number, tree moulds provide information on the palaeoslope and vent location.
Archaeocyathid fauna of the lowest fossiliferous levels of Tiout (Lower Cambrian, Southern Morocco)
Authors: Debrenne F. , Debrenne M. 
Published: May 2009

SummaryThe oldest archaeocyathid fauna from Tiout (Anti-Atlas, Morocco) contains 15 species belonging to 11 genera. The following species: Aldanocyathus cribratus, Neoloculicyathus magnus, Coscinocyathus primus, C. secundus, C. fasciola, Tumulifungia marocana, Gordonifungia cowieiare new. The biostratigraphy of this archaeocyathid fauna demonstrates that the lower boundary of the Amouslekian stage should be moved downwards to within the ‘Calcaires Supérieurs’ of the Adoudounian (Assadassian or equivalent Ouneinian). One or perhaps more archaeocyathid and trilobite zones may yet be found beneath this boundary at Tiout. The uppermost ‘Calcaires Superiéurs’ may be dated, on the basis of Archaeocyatha, as equivalent to the Atdabanian stage, but not to the lowest part of it. The underlying fossiliferous horizons should be equivalent to all or part of the lower Atdabanian. The Precambrian–Cambrian boundary in Morocco can be looked for lower in the succession and defined on the basis of other fossil groups.
Silurian fossils from western Spitsbergen
Authors: Scrutton C. T. , Horsfield W. T. , Harland W. B 
Published: May 2009

SummarySilurian fossils have been identified from Oscar II Land, western Spitsbergen. They are the first Silurian fossils recorded from Spitsbergen, and throw new light on regional correlations and the dating of Palaeozoic orogenic events in the region.
Emplacement of an epizonal granodiorite pluton λ by vertical block elevation
Authors: Leitch E. C. 
Published: May 2009

SummaryThe Carrai Granodiorite is an intrusive magmatic pluton with steeply dipping margins surrounded by a well-developed contact metamorphic aureole. Emplacement of the body was accompanied by little distortion of neighbouring rocks and involved vertical displacement of pre-existing material. Scarcity of country rock blocks, and the presence of numerous dioritic xenoliths indicate that stoping was unimportant, and the pluton was accommodated in the upper crust by vertical uplift of earlier rocks (‘block elevation’). A close relationship existed between faulting and granodiorite emplacement. Deep shears possibly account for the generation of the linear zone of plutons in which the Granodiorite is located.
A note on the sulphurization of Fe-Tremolite
Authors: MacRae N. D. , Grant M. , Kullerud G. 
Published: May 2009

SummaryCharges of Fe-tremolite, sulphur and water sealed in gold capsules and run at 600°C and 1 kb confining pressure for one month yielded talc, anhydrite, pyrite and quartz as principal mineral phases. It is concluded that in a S-rich environment talc is stabilized rather than diopside by the strong preference of Ca to form anhydrite.
Ecologic significance of post-Palaeozoic green calcareous algae
Authors: Elliott Graham F. 
Published: May 2009

SummaryThe palaeoecologic significance of post-Palaeozoic green calcareous algae is evaluated with what is known of the environments of comparable living algae. Here requirements and tolerances of temperature, bottomsediment, salinity and water-energy may be observed; depth is apparently significant only as it influences these. In the extinct algae, only a minority show clear taxonomic relationship to living algae, in palaeo-environmentsdeduced from independent evidence. Codiaceae and Dasycladales seem to have had environmental preferences like their living descendants, with preferredmicroenvironments in some genera.
Middle Pleistocene drainage in the Thames valley
Authors: Gibbard P. L. 
Published: May 2009

SummaryStratigraphical investigations in the Finchley depression (Middlesex depression) are summarized and show that a gravel, laminated deposits and till sequence is present. Compositional study of the gravels indicates that they were derived from S of the present Thames valley. Gravel patches in North Surrey can be subdivided into two terrace fragments formed by a Mole-Wey south bank Thames tributary. The upper unit is correlated with the gravel at Finchley. The lower unit terrace can be shown to grade into the Thames Black Park Terrace Gravel, and the latter is extended through London to Dartford and Chatham. The events leading to the diversion of the Mole-Wey tributary by the Anglian chalky till ice parallel those of the Thames in the Vale of St Albans and suggest that similar events may also have occurred in other S bank tributary valleys to the E.
Mesozoic stratigraphy of Eastern Svalbard: a discussion
Authors: Edwards M. B. , Bjærke T. , Nagy J. , Winsnes T. S. , Worsley D. 
Published: May 2009

SummaryThis paper proposes an alternative to the complex stratigraphical nomenclature introduced in recent descriptions of the stratigraphy of Eastern Svalbard. We believe that the platform nature of the Mesozoic succession in Svalbard enables recognition of individual stratigraphical units over very wide areas. Our principal conclusions are that the Wilhelmøya Formation can be recognized as the upper formation of the Kapp Toscana Group and occurs throughout Eastern Svalbard. It overlies the De Geerdalen Formation on Hopen and Wilhelmøya. The Janusfjellet and Helvetiafjellet Formations can be recognized on Kong Karls Land.
K-Ar ages from the ore deposits and related rocks of the Isle of Man
Authors: Ineson P. R. , Mitchell J. G. 
Published: May 2009

SummaryThirty-seven new K-Ar isotopic ages are reported from the Isle of Man. Thirty clay mineral concentrates from vein gouges and altered wallrocks when interpreted with the remaining seven whole rocks and mineral ages indicate that at least five periods of metasomatism have affected the rocks. It is argued that these can be identified with episodes of ore deposition. The earliest phase, N of the Foxdale area, occurred at 310–320 Ma and appears to be the most extensive of the episodes recorded. In the S of the island, mineralization occurred later at c. 285 Ma and again at c. 250 Ma. Minor Triassic activity is expressed by a cross-course on the Foxdale lode, and a single locality displaying Tertiary mineralization was recognized. The conformity of these ages to the general episodic pattern of ore deposition in the British Isles is demonstrated.
Mg–Fe distribution between coexisting garnet and biotite, and the status of fibrolite in the andalusite–staurolite zone of the Mt Lofty Ranges, South Australia
Authors: Fleming P. D. 
Published: May 2009

SummaryThe distribution of Fe and Mg between coexisting garnet and biotite from andalusite-staurolite zone rocks of the Mt Lofty Ranges is briefly discussed. The average value of the corresponding distribution coefficient, and those of some related parameters, are compared with the values proposed by a number of authors as being characteristic of certain metamorphic grades. From these comparisons it is concluded that despite their occurrence in a terrain in which fibrolite commonly occurs, the rocks have probably only experienced P-T conditions corresponding to those of the andalusite phase field, and that fibrolite has formed under similar conditions.
Isotopic age determinations on clay minerals from lavas and tuffs of the Derbyshire orefield
Authors: Ineson P. R. , Mitchell J. G. 
Published: May 2009

SummaryEpisodic hydrothermal mineralization has previously been recognized in the northern section of the Pennine orefield. Igneous rocks from the southern section (the Derbyshire orefield) have yielded isotopic ages, some of which are thought to represent ages of hydrothermal metasomatism (deuteric or subsequent). In order to ascertain whether epicyclic hydrothermal events gave rise to the Derbyshire mineral deposits, samples of highly altered doleritic lava and pumice tuff were collected adjacent to areas of mineralization. Clay-mineral concentrates from 34 samples were dated by the potassium–argon method. The conclusions drawn from these analyses support a hypothesis of repeated hydrothermal alteration of the clay minerals, reflecting at least two episodes of mineralization, one about 270 m.y., the other about 235 m.y. The geo-chronological significance of these and other results is considered.
Crescumulate layering in a gabbroic body on Seiland, northern Norway
Authors: Robins B. 
Published: May 2009

SummaryThe cumulates and crescumulates in the Crescumulate Zone of the Rognsund gabbro are described. The olivine and olivine-clinopyroxene crescumulates contain large dendritic crystals of olivine due to rapid upward growth from cumulus nucleii on the temporary floor of the magma chamber. Crescumulate growth was accompanied by the bottom accumulation of primocrysts, some of which were enlarged by the normal adcumulus process. The crescumulates are thought to have originated when cumulus crystals sank from a labile environment near the roof of the body into a metastable environment on the floor.
Single whole rock K—Ar isochrons
Authors: Fitch F. J. , Miller J. A. , Hooker P. J. 
Published: May 2009

SummaryConventional K—Ar age determinations are frequently discrepant. A major factor is the failure of rocks to conform to the basic simplifying assumptions made in the total fusion method. Many rocks incorporate initial argon with an isotopic composition different from the present atmosphere and others have not remained closed systems.By careful sampling and the application of isochron geochronometry more reliable and geologically acceptable K-Ar ages can be obtained. K-Ar step heating isochrons from Kenyan Miocene volcanic sanidines are used to illustrate the accumulating evidence for the presence in ancient rocks of initial argon with an isotope ratio unlike that of the modern atmosphere. Single whole rock total fusion K-Ar isochrons from the Olduvai basalt, Tanzania and the Upper basalts of Antrim are presented to illustrate a new version of the K-Ar isochron technique. Special circumstance multiple rock K-Ar isochrons from the Belfast section of the Antrim basalts and from an ignimbrite-ash flow unit in Bed I, Olduvai Gorge, are used in a further discussion of the general applicability and usefulness of K-Ar isochrons.
Reinterpretation of ceratitic ammonoids from the Greville Formation, New Zealand
Authors: Furnish W. M. , Glenister B. F. , Kummel B. , Spinosa C. , Sweet W. , Teichert C. 
Published: May 2009

SummaryCeratitic ammonoids from the Greville Formation in the Nelson Regional Syncline, South Island of New Zealand, were described as a new genus and species of the Ophiceratidae, Durvilleoceras woodmani, and dated as ‘late Middle Permian’ (Waterhouse, 1973). In fact, Durvilleoceras differs from all known Permian ammonoids in both conch form and sutural pattern, but closely resembles lower Triassic ceratites. Structural and sedimentologic complexities within the Nelson Syncline are such that stratigraphic interpretations are questionable, and the fauna of both the Greville and adjacent formations is sparse. Consequently, we consider that Durvilleoceras is best interpreted as a middle Scythian ceratite of the family Flemingitidae.
Variation in lens packing ofPhacops(Trilobita)
Authors: Fortey R. A. , Morris S. F. 
Published: May 2009

SummaryPhacops turcoaff.praecedensHaas, from the Devonian (Eifelian) of Morocco, varies in the type of lens packing in the eye. Cubic close packing in trilobite eyes is described for the first time.
A Liassic palaeofault from Dorset
Authors: Jenkyns H. C. , Senior J. R. 
Published: May 2009

SummaryEvidence is presented for Liassic (Toarcian) faulting at Watton Cliff in coastal W Dorset. This movement is inferred from the abrupt changes in thickness of the Junction Bed and contiguous strata given that the contact with the overlying shale and clay is horizontal. Further evidence for synsedimentary movement is manifested by the presence, in the palaeofault zone, of numerous calcilutite-filled fissures penetrating a coarser, more sandy matrix. These neptunian dykes and sills contain abundant ammonites of the middle to late Toarcian, presumably the time of fault movement. This onshore Jurassic palaeofault broadens the known extent of such features from Sutherland (Brora—Helmsdale Fault) and Yorkshire (Peak Fault) to include southern Britain.
Numerical methods for the reconstruction of fossil material in three dimensions
Authors: Doveton J. H. 
Published: May 2009

SummaryDistances measured between homologous reference points on fragmentary fossil material can be used to recover a three-dimensional framework by operations of standard matrix algebra. A procedure that combines both linear and non-linear algorithms is described and illustrated in a simple reconstruction of Waptia fieldensis. The approach attempts to provide a modelling process in which a palaeontologist can explore the geometrical consequences of fossil measurements through continuous interaction with programmed reconstructions.
Stratigraphical inversion in the Sulitjelma Area, Central Scandinavian Caledonides
Authors: Boyle A. P. , Griffiths A. J. , Mason R. 
Published: May 2009

SummaryMajor stratigraphical inversions are recognized in two parts of the Sulitjelma area, on the border of Norway and Sweden. In the Otervatn area, inversion is directly demonstrated by way-up structures in pillow lavas of the Sulitjelma Amphibolite Group. The porphyritic amphibolites of the group belong to a penecontemporaneous sheeted intrusive complex which originally underlay the pillow lavas. The other inversion, S of Sorjusjaure, is proposed in order to simplify the stratigraphical succession of the area. The inversions are both thought to belong to the inverted limb of the Gasak Nappe, which is the upper tectonic unit at Sulitjelma. Folding associated with the inversion could cause tectonic repetition of the strata-bound Sulitjelma ore horizon.
Diagenetic concretions from the Ribband Group sediments of County Wexford, Ireland
Authors: Shannon P. M. 
Published: May 2009

SummaryAn occurrence of small diagenetic siderite concretions is described. They occur towards the top of a postulated shallowing sequence of cleaved Lower Palaeozoic siltstones and shales. The concretions occur as lenses and aggregates associated with horizontal grazing trails, and also as diffuse bands apparently unrelated to the latter. The concretions are compared with other similar structures described elsewhere, and an origin by diagenetic growth beneath the sediment–water interface in a marine environment is postulated.
Precambrian stratigraphic scale of the USSR
Authors: Keller B. M. 
Published: May 2009

SummaryA new stratigraphic scale of the USSR Precambrian officially adopted by the All-Union Precambrian Meeting in Ufa (1977) and approved by the National Stratigraphic Committee (1978) is discussed. Archean and Proterozoic have been distinguished in the Precambrian, the boundary between being 2600 Ma. Proterozoic is subdivided into the Lower- and Upper-Proterozoic with the boundary between them 1650 Ma. Riphean and Vendian are distinguished in the Upper Proterozoic. More detailed subdivisions of the Upper Proterozoic are Burzyanian, Yurmatian, Karatavian, Kudashian and Vendian. Lithological and palaeontological characteristics of these subdivisions and their radiometric age are given.
Fission track dates from two Galloway granites, Scotland
Authors: Hurford A. J. 
Published: May 2009

SummaryPrevious radiometric age determinations for the Criffell–Dalbeattie and Cairnsmore of Fleet Newer Granite intrusions are briefly reviewed. Thirteen fission-track dating results are presented for the co-existing accessory minerals sphene, zircon and apatite separated from the two granites. The mean sphene apparent age of 401±10 Ma and single zircon apparent age of 389±26 Ma are interpreted as the age of initial post-intrusion cooling of the granites. Results from apatite are discordant with those of sphene and zircon. Four determinations give a mean Upper Cretaceous apparent age of ∼ 80 Ma which is not readily interpreted. A single apatite determination upon a sample located adjacent to a basaltic dyke yielded a Tertiary age.
The occurrence of large scale kink bands in Campanian chalk at the Gulf of Elat (‘Aqaba) rift zone
Authors: Shirav (Schwartz) M. 
Published: May 2009

SummaryThree sets of kink bands occur in Campanian chalk, near the coast of the Gulf of Elat. The kink bands can be traced by a system of vertical joints, intersecting the chalk and filled with secondary crystalline calcite. The geometry and the development of these structures are described, suggesting a change of the stress regime during the opening of the rift along the studied area.
Geology of Hopen, Svalbard
Authors: Smith David G. , Harland W. B. , Hughes N. F. 
Published: May 2009

SummaryHopen (Hope Island) in the Svalbard archipelago is difficult of access and only recently has reliable geological information become available. Published information is reviewed and combined with new observations.The island, 37 km long and no more than 2.5 km wide or 370 m high is structurally simple with flat-lying arenaceous strata which are described with three measured sections. Three new local stratal units are defined: Iversenfjellet Formation (325 m, base not seen); Flatsalen Shale Formation (55 m); and Lyngefjellet Sandstone Formation (80 m, top not seen).From a few ammonite, bivalve, saurian and plant megafossil occurrences and 30 palynomorph taxa (newly recorded) the marine and fluviatile facies range in age from possibly late Karnian, through Norian, Rhaetian and possibly into early Jurassic. The Rhaetian flora, well established palynologically, is the first clear evidence of rocks of this age in Svalbard. Associated Sirenites extends the range of this ammonite and suggests that Svalbard may yield significant new evidence for this span of Earth history.
Ultramafic nodules and their host rocks from Auckland, New Zealand
Authors: Rodgers K. A. , Brothers R. N. , Searle E. J. 
Published: May 2009

SummaryUltramafic and mafic nodules are abundant inclusions in Cainozoic alkali basalts at 7 localities in the Auckland Province. Nodule types show a gradation from dunites and pyroxenites through periodotites to eucrites. Bulk chemical variations in the nodules show a wide range in MgO/ΣFeO with a tendency for Al2O3, ΣFeO, CaO and Na2O + K2O to increase as this ratio decreases. These chemical trends, together with published data on the nodules mineralogy and fabric, are consistent with their being interpreted as fragments of the upper mantle.
Epidotic calc-silicates of Arnipol Type—a widely distributed minor sedimentary facies of the Moinian assemblage, Scotland
Authors: Winchester J. A. 
Published: May 2009

SummaryIn the Moinian rocks of Scotland, epidote-bearing calc-silicates, distinct from the commoner garnet-zoisite-bearing calc-silicates, occur at several widely scattered locations. The major element geochemistry of the two types of calc-silicate is very similar, and their somewhat different petrology and trace element geochemistry may be explained by the preservation of grains of detrital epidote and heavy minerals in the epidotic calc-silicates. These grains were concentrated in the original sediment and remained stable under greenschist and epidote-amphibolite metamorphic facies conditions. While the garnet-zoisite bearing calc-silicates may be derived from calcareous marls, the epidotic calc-silicate bands are probably derived from epidotic grits similar to those recorded in the Torridonian.