bluuebunny/crossref_metadata_2025 huggingface dataset:
Stratigraphic classification and nomenclature of the Precambrian–Cambrian transition
Authors: Glaessner M. F.
Published: May 2009

Relevant points of general principle and special application to the problem under discussion are quoted selectively from the recently published time scale by Harland et al. (1982) and critically considered. Most of the principles and the resulting names for divisions of the Precambrian–Cambrian transition used in it are accepted. The unique significance of the transition from dominantly chronometric to dominantly chronostratic boundaries based on the ‘biostratigraphic sequence’ is an additional justification for the higher ranks previously given to the Vendian (Era) and its constituent divisions: Varangian (or Varangerian) and Ediacaran (or Ediacarian) Periods. The historic transition begins with the latest of the Proterozoic glaciations (the earlier ones started about 950 m.y. ago) and ends with the exponential diversification of the Metazoa. The causal linkage of the two events is hypothetical. Their stratigraphic sequence is demonstrable on the East European platform where the type section of the Vendian is located, and on the Yangtse platform. Normative, operationally designated boundaries are required for the stratigraphic divisions. The history of life in which there are no sharp initial and terminal boundaries shows clearly a rapid transition from widespread but generally rare occurrences of Vendian, particularly Ediacaran, fossils to ubiquitous, generally ‘shelly’ Palaeozoic (initially Cambrian) faunas of unquestioned biostratigraphic importance. This biohistoric transition is the beginning of the Phanerozoic division of a unique historic process. For the Eon of the stratigraphic scale comprising Palaeozoic to Cainozoic Eras the new term Holozoic is therefore proposed.
Research on the isotopic age of the Sinian–Cambrian boundary at the Meishucun section in Jinning County, Yunnan Province, China
Authors: Xiaofeng Xue
Published: May 2009

In this paper the author describes the results of the Rb-Sr isotopic dating of black shale at the Sinian (Precambrian)–Cambrian boundary at the Meishucun section, Jinning County, Yunnan Province, China. The Sinian and Cambrian strata in eastern Yunnan are well developed, the Sinian–Cambrian boundary section in the vicinity of Meishucun Village in Jinning County being representative. These well developed strata provide excellent conditions for research on the radiometric age of the Precambrian–Cambrian boundary. An Rb-Sr isochron age of 579.7 ±8.2 Ma has been obtained on black shale from the Badaowan Member of the Early Cambrian Qiongzhusi Formation, which occurs at 20 m above the Sinian–Cambrian boundary. So an inferred age of 610±10 Ma is given for the Sinian (Precambrian)–Cambrian boundary.
The use of silicone rubbers in the preparation of casts from natural fossil moulds
Authors: Kelly S. R. A. , McLachlan A.
Published: May 2009

Techniques are described for the preparation of flexible casts of macrofossils preserved as natural moulds. Materials are discussed and the choice of two high-cost silicone rubbers justified.
Surface structures formed by wind activity on a sandy beach
Authors: Vortisch W. , Lindström M.
Published: May 2009

Sandy beaches in humid climate zones can have several structures that may be preserved if covered by aeolian sand. Many structures are caused by humidhesion. This new term is coined for the fixation of sand by wetness in the aeolian sedimentary environment. Humidhesion results in relative firmness of the sand, mimicking cementation. Erosive and accretionary humidhesion structures are described.
Role of lava tubes in flows from the Observatory Vent, 1971 Eruption on Mount Etna
Authors: Guest J. E. , Underwood J. R. , Greeley R.
Published: May 2009

The role of tubes in aa flows may be more important than previously recognized. On Etna they are commonly found in the near-vent areas of aa flows. A study of tubes associated with the 1971 Observatory Vent on Etna suggests that ephemeral boccas on the flow surface downslope of the main vent were fed by tubes.
Dedolomitization of Lower Carboniferous Dolostone in the Wirksworth area, Derbyshire, England
Authors: Munn D. , Jackson D. E.
Published: May 2009

Lower Carboniferous secondary dolostones are shown to be affected by dedolomitization. The crystals of dolomite most affected are those occurring around calcite-filled rhombohedral pores within the dolostones. Dedolomitization of dolomitized crinoid ossicles also occurs. This is thought to be caused by their greater susceptibility to dedolomitization due to dolomicritization. Dedolomitization and subsequent dissolution, giving an enhanced porosity to the dolostones, are believed to be related to the present-day weathering surface.
Sedimentary stratigraphy of Eocene sheetflood deposits, Southern Pyrenees, Spain
Authors: van der Meulen S.
Published: May 2009

The Eocene Monllobat Formation of the southern Pyrenees accumulated under continental (non-marine) conditions. The total thickness of 180 m consists of seven cycles, defined by coarse member concentrations (often sheets) at the bases. The lateral extent of the sheets defines the fixed positions of eight parallel-trending alluvial systems, separated by narrow zones of fine sediment.

Sheetflooding dominated the sedimentation of these eight contemporaneous alluvial systems. The sediment was supplied from the rising axial zone of the Pyrenees. The cycles were caused by variations in tectonic activity. The positions and forms of coarse members were locally determined by contemporaneous faulting and folding of the alluvium.
A new Carboniferous trilobite from Spitsbergen
Authors: Ruitang Wu
Published: May 2009

Two Carboniferous trilobites, Ditomopyge convexa sp.nov. and Paladin (Paladin) sp.ind., are described from the Nordenskiöldbreen Formation in Spitsbergen. The new material is of considerable interest as it extends the known distribution of Carboniferous trilobites and provides further information on palaeobiogeography.
Geochemical compositions and depositional conditions of Upper Jurassic and Lower Cretaceous Yorkshire clays, England
Authors: Dypvik H.
Published: May 2009

Fifty-three samples from the Oxford, Kimmeridge and Speeton Clays of the Yorkshire area have been analysed petrographically and geochemically, by X-ray diffraction, X-ray fluorescence, atomic absorption and combustion (TOC). Major elements and the following trace elements have been determined: Rb, Sr, Ba, Cr, V, Co, Ni, Cu, Zn and Mo. P2O5, Rb, Ba, Cr and V show positive correlation to the clastic fraction (quartz, feldspar and clay minerals). CaO, MnO, and Sr and to a lesser extent Ni, Cu and Zn seem to be positively correlated to calcite, while Fe2O5, MnO, MgO and Co are linked to siderite. Stratigraphical variations of element/element ratios have been used to obtain sedimentological information from the petrographical and geochemical data.

The Oxford Clay, with its coarse and immature clays, was deposited in a regressive development. An upwards shallowing with ventilated deposition of more mature and altered clastic material took place throughout the unit. During deposition of the Kimmeridge Clay more reducing conditions existed and finer grained, smectite-rich sediments were formed. The fine grained Speeton Clay was deposited during changing depositional conditions, varying ventilation in a generally regressive development. Several sedimentological breaks characterize the unit.
The Jurassic transgression and the mid-late Jurassic succession in Milne Land, central East Greenland
Authors: Callomon J. H. , Birkelund T.
Published: May 2009

New ammonite finds indicate that the sea transgressed over the crystalline basement of Milne Land, East Greenland, in Boreal Bathonian time and not in Middle Oxfordian as previously thought. A coral (Enallocoenia callomoniBeauvais) occurring in the transgressive Upper Bathonian deposits is the first hermatypic coral known from the Boreal Middle Jurassic. The unusually complete Boreal Upper Callovian–Oxfordian–Kimmeridgian ammonite succession is described; the faunas include remarkable occurrences of submediterranean genera (Hibolithes, Pachypictonia, Streblites). Finally, the sedimentary and tectonic evolution of Milne Land and adjacent areas in Jurassic time is outlined. It is shown that the area was characterized by gentle block-faulting.
Weichselian (Late Quaternary) ostracods from the Sandnes Clay, Norway
Authors: Lord A. R.
Published: May 2009

Boreholes drilled at Sandnes, SW Norway penetrated Quaternary (Weichselian) marine interstadial sediments which contained ostracods. The ostracods, which are analysed and discussed, were found to be indicative of cool, probably sub-arctic, shallow-water conditions. Some evidence of faunal mixing is attributed to the effects of glacial meltwater input into a shallow marine environment.
Arumberia Glaessner & Walter, a review of its potential for correlation in the region of the Precambrian–Cambrian boundary
Authors: Bland B. H.
Published: May 2009

Arumberia is a large impression fossil which may be allied to the Ediacaran fossils Ernietta and Pteridinium. New finds and published evidence suggest that it was restricted to very shallow, possibly non-marine, environments, and to rocks of latest Precambrian to Lower Cambrian age. Well-preserved material from the Longmyndian shows that it was associated with numerous small spherical structures. At present it is only of broad stratigraphic use, but as the wide range of characters observed becomes better understood it may prove more valuable, especially as it occurs in otherwise poorly fossiliferous environments.
Thrust tectonics: a personal view
Authors: Butler Robert W. H.
Published: May 2009

The structure of fold and thrust belts has been studied for just over one hundred years and has been the subject of a recent international conference at Toulouse, in May 1984. This article reviews some of the recent advances in thrust tectonics from a personal viewpoint, in the light of the Toulouse meeting. Key tools in correctly interpreting thrust systems are the use of balanced (restorable) cross-sections and the resolution of three dimensional fault systems. These analytical methods are now being widely developed and applied to numerous orogenic belts with many surprising results. While our understanding of foreland thrust belts is now probably better than any other structural environment, there is still great uncertainty as to the emplacement-driving mechanisms of these belts. Future work will try to solve these and other outstanding problems and apply the new analytical methods to the interior parts of thrust belts in efforts to restore entire orogens.
Depositional history of southern Tunisia and northwestern Libya in Mid and Late Jurassic time
Authors: Walley C. D.
Published: May 2009

The good exposures of virtually undeformed Callovian and Oxfordian strata along the Djeffara escarpment of southern Tunisia and northwestern Libya have allowed analysis of regional depositional history during this time.

A number of lithostratigraphic problems are considered. In Tunisia, the Foum Tatahouine Formation is subdivided into members and in Libya some of the stratigraphic issues are clarified. A correlation between the two sequences is proposed. The widely claimed aeolian origin for the Libyan Chameau Mort Sandstone is rejected.

The depositional patterns of the Callovian and Oxfordian strata are described in the context of Mid and Late Jurassic sedimentation in the eastern Ghadames basin of the African craton. After a regressive Bathonian sequence, transgressive conditions commenced in Early Callovian time. In a series of continental–marine cycles, this transgressive sequence culminated in widespread shallow, restricted-marine micritic deposition. A regression in Late Callovian time resulted in emergence marked by a thin but widespread calcrete horizon. In Mid? Oxfordian time a renewed transgression brought in open marine, high-energy, shallow-water carbonates. Later, regressive conditions returned, leading to increasing restriction, and latest Jurassic time saw the first signs of the fluvio-deltaic deposition that was to dominate the region in Early Cretaceous time.
The origin of granite erratics in the Pleistocene Patella beach, Gower, South Wales
Authors: Jenkins D. G. , Beckinsale R. D. , Bowen D. Q. , Evans J. A. , George G. T. , Harris N. B. W. , Meighan I. G.
Published: May 2009

Rare pebbles of granite have been discovered in the raised Patella beach at Butterslade, Gower, South Wales. Their petrography, trace element geochemistry and the Rb/Sr whole rock age of 55 ± 5 Ma confirm that they are derived from the Lundy granite which is about 49 km to the southwest of Gower. Amino acid analyses of fossil gastropods in the Patella beach have provided an age of 210000 years. Various hypotheses of transportation of pebbles from Lundy and Pembrokeshire to Butterslade are considered. Erratics from Pembrokeshire were probably transported by Pleistocene ice into the area while clasts of Lundy granite were moved by progradation of beach deposits northeastwards towards Gower during glacio-eustatic marine transgressions in the Pleistocene.
The Aristarchus impact event and the effects of target material
Authors: Guest John E. , Spudis Paul D.
Published: May 2009

The relatively well preserved, 42 km diameter lunar impact crater Aristarchus was excavated across the boundary between the Aristarchus Plateau and the mare plains. Previous geological mapping of the different ejecta facies associated with Aristarchus has shown that there are distinct morphological differences between ejecta emplaced on either side of the fault scarp that separates the plateau from the mare. One explanation of this observation is that ejecta behaved in different ways on emplacement depending on the original lithology of the excavated material. To test this proposal, we examine the pre-Aristarchus regional stratigraphy and identify the spectral signatures of each of the material's units. By comparing these data with analysis of the geology and spectral characteristics of the ejecta units, we are able to show the provenance of each of the mappable ejecta facies. The conclusions are consistent with the concept of the crater ejecta asymmetry being related to bedrock characteristics. Using geological mapping, spectral interpretation and present understanding of the impact cratering process, we reconstruct the impact event and suggest how such techniques could be used further to interpret the Moon's composition and history.
Protremaster, a new Lower Jurassic genus of asteroid from Antarctica
Authors: Smith Andrew B. , Tranter T. H.
Published: May 2009

A new and well-preserved.asteroid, Protremaster uniserialis (gen. & sp.nov.) is described from the Lower Jurassic (Sinemurian) of Antarctica. This find extends the fossil record of the family Asterinidae and the subfamily Tremasterinae considerably and lends support to the idea that asteroids underwent an important morphological diversification in the late Triassic-early Jurassic.
A note on the age and pyroxene chemistry of the igneous rocks of the Shelve Inlier, Welsh Borderland
Authors: Lynas B. D. T. , Rundle C. C. , Sanderson R. W.
Published: May 2009

Geological survey, electron microprobe analyses of clinopyroxenes and isotopic age determinations have revealed that the intrusive dolerites and basic–intermediate lavas of the Shelve Ordovician Inlier are part of a co-magmatic suite which show transitional affinities between tholeiites and alkali basalts. The ages of most of the intrusives are shown to be mid-Ordovician.
Structure and eruptive mechanisms at Surtsey Volcano, Iceland
Authors: Moore James G.
Published: May 2009

Glassy basalt tuff was the primary material cored in 1979 from a 181 m deep drill hole on the east tuff ring of Surtsey volcano. Despite the fact that the hole extends 122 m below sea level all the core is similar to the exposed tephra composing the two tuff rings of the island. The tuff includes abundant accretionary lapilli and tuff vesicles, indicating that it was all deposited subaerially. During the growth of the tuff rings, repeated hydromagmatic explosion cycles began with a series of intermittent tephra-finger explosions leading up to continuous uprush explosions which lasted for several minutes to several hours. This nozzle-like continuous activity produced eruption columns 100–250 m in diameter and 500–2000 m in height which probably quarried several hundred metres below the ground surface. The continuous-uprush explosion type provides a reasonable mechanism to excavate a diatreme from the top down. During construction of the tuff rings, concentric faults repeatedly downdropped a funnel-like structure (400–800 m in diameter) several hundred metres, thus accounting for the presence of subaerially deposited tephra in the drill core far beneath sea level. Ring dykes later intruded upward along these faults and fed small lava flows. Heat in the surface tephra probably originated primarily from these shallow intrusions.
Form and mode of life of Dicellograptus (Graptolithina)
Authors: Henry Williams S.
Published: May 2009

The majority of Dicellograptus species have stipes which spiralled to a greater or lesser extent; this explains continuous variation of axial angle found in several species and many anomalous features of flattened or partially flattened specimens. The effects of variation in thecal style along the stipe are distinguished from those produced by variable orientation of the rhabdosome during flattening and by later tectonic distortion. It is concluded that Dicellograptus probably lived with stipes pointing upward and that the rhabdosome rotated in a horizontal plane due to eddies created by the non-directional ciliary activity of radially dispersed zooids in order to improve feeding efficiency.
Evolution and classification of some Ordovician Calymenina (Trilobita)
Authors: Henry J.-L.
Published: May 2009

The classification of the generaPlaesiacomiaHawle & Corda, 1847,KerfornellaHenry, 1976,ColpocorypheNovák in Perner, 1918,SalterocorypheHammann, 1977 andNeseuretusHicks, 1873, is discussed.PlaesiacomiaandKerfornellaare attributed to the Homalonotidae (sub family Kerfornellinae nov.), whileColpocoryphe, Salterocoryphe, andNeseuretusare regarded as belonging to the Calymenidae. The author's opinion is mainly based on the morphology and evolution of the coaptative devices, and on the morphology of the hypostoma.
Secondary faulting, a consequence of a single continuous bifurcation process
Authors: Bahat Dov
Published: May 2009

Fracture propagation in the crust under post-critical conditions (rapid propagation), and possibly in some instances even under sub-critical conditions (slow propagation) can produce fracture-branching in a single continuous process. Later local or regional stresses result in displacements along the fractures and secondary faulting develops. This concept can explain various secondary features like conditions of branching, branching-angle and shallow secondary faults. The splaying of the Hope Fault in New Zealand is primarily a result of early fracture bifurcation and later minor displacements.
How should igneous rocks be grouped?
Authors: Rock N. M. S.
Published: May 2009

Despite their importance and frequency of usage, ‘grouping terms’ in petrology such as Association, Family, Lineage, Province, Series and Suite appear to lack established meanings. Partly by analogy with the recently standardized stratigraphic nomenclature, hierarchies of such terms are suggested to cover petrographic classification (rock-names), petrological classification (rock-names extended to magma-types), geographic classification (igneous provinces) and tectono-genetic classification (rock assemblages characteristic of particular tectonic regimes). Used in this way, the exact implications of each term become clearer. Again by analogy with stratigraphy, ‘Super-’ and ‘Sub-’ groupings are suggested in a few cases: ‘Subprovince’ for example can differentiate distinct rock assemblages related to separate parent magmas within one well-defined Province (e.g. nephelinite-carbonatite and basalt-trachyte assemblages in the East African Rift), and ‘Superprovince’ can be used to group coeval Provinces now separated by opened oceans, etc. (e.g. Thulean Superprovince composed of Hebridean, East Greenland, etc., Provinces). The term ‘Province’ itself carries several ambiguities; it is best confined to cases where the ages of the spatially associated igneous rocks fall within a narrow range (e.g. Oslo Province); ‘Belt’ is suggested for those where the age-range is more substantial (e.g. Jurassic-Tertiary magmatism of Southeast Brazil).
Variation of metamorphic grade in Lower Strathspey
Authors: Winchester J. A.
Published: May 2009

The mineral assemblages in calc-silicates collected from Ballindalloch and Bridge of Avon suggest that the grade of metamorphism is lower than in the areas to the E and W. Mild post-metamorphic warping may be responsible for the production of an apparent ‘thermal anticline’ in the Monadhliath Mountains and the complementary ‘thermal syncline’ in Lower Strathspey.
The Devonian System in China
Authors: Shih-Pu Yang , Kiang P'an , Hung-Fei Hou
Published: May 2009

The Devonian System of China occurs in the Tianshan–Hingan* Geosyncline of North China, the Yangtze Paraplatform of South China and in the geosynclinal areas of West China. Devonian formations are entirely absent from the Sino-Korean Paraplatform and the Tarim Platform, but along the border of the Tarim Basin and the slopes of Qilianshan (Chilienshan) are continental sequences rich in vertebrate and plant fossils. On the basis of differences in biostratigraphic characteristics the Devonian is divisible into 8 regions: 1. Junggar–Hingan (Dzungar–Khingan), 2. South Tianshan (South Tienshan), 3. Qilianshan (Chilienshan), 4. Longmenshan (Lungmenshan), 5. South China, 6. South-eastern China, 7. West Sichuan–North Xizang (West Szechuan-North Tibet), 8. Himalaya–West Yunnan.

Using both lithology and fossil content, five principal facies (types) may be further differentiated: 1. Hingan type (eugeosynclinal facies), 2. Baoxin type (miogeosynclinal facies), 3. Xiangzhou type (platform near-shore facies), 4. Nandan type (platformal off-shore facies), 5. Cuifengshan (Chuifeng shan) type (continental facies).

The Devonian of South China occurs in various facies, but has a well-defined principal stratotype. It has been divided by Chinese geologists into eight stages, two in the Upper Devonian, two in the Middle Devonian and four in the Lower Devonian.

The Devonian sequences of the geosynclinal regions of West China are characterized by facies which contain graptolites and tentaculites, and have largely been affected by regional metamorphism. The Devonian biota of the Junggar–Hingan Region is essentially an endemic one, but it is associated with a few European and North American elements. Marine pyroclastics are the principal rocks. General stratigraphical columns of those regions are given with a correlation with other parts of China. The continental Devonian of China is unique especially in the light of its vertebrate content. Red sandstones are widespread in the Lower Devonian, and intercalated with argillaceous limestone and mudstone. This sequence is rich in endemic East Asiatic faunal elements including agnatha (Galeaspida, Polybranchiaspida), Antiarchi, etc. Middle and Upper Devonian lithostratigraphic units consist principally of light coloured quartzose sandstone formations in Southeastern China, with some red beds in South and North China, while their fauna and flora are cosmopolitan in character. Their exact geological ages vary, however, as clearly shown in the South China region, especially towards the top of the Upper Devonian (with Asterolepis) and in the early Middle Devonian (with Bothriolepis).
Displacement of sand grains in sandy gypsum crystals
Authors: Shearman D. J.
Published: May 2009

Sand grains enclosed in gypsum crystals which grew in otherwise uncemented sand commonly, either float in the gypsum, or, are arrayed in sand-bearing and sand-free zones in a manner which indicates that they were displaced during growth of the gypsum. Corroborative evidence of displacement of included sand grains is found in some sandy gypsum crystals from coastal sabkhas in Abu Dhabi, U.A.E. In these crystals, dust particles which formerly coated the sand grains are strung out as festoons behind the grains and thus record the directions and extent of the displacement. The direction of displacement was outwards, normal to the traces of what had been former crystal faces. The displacement also involved some pivoting of elongate grains which now lie with their long axes in the direction of movement.
The structure and shape of the Jimberlana Intrusion, Western Australia, as indicated by an investigation of the Bronzite Complex
Authors: McClay K. R. , Campbell I. H.
Published: May 2009

The structure of the partly exposed lower section of the Jimberlana Intrusion has been determined by combining the geophysical evidence with the available geological and diamond drill hole data. The results have been added to the wellknown upper section to show that Jimberlana is not a dyke-like body as had previously been thought, but is a horizontal pipe-like intrusion 180 km long, 2.5km wide and 5.5 km deep, with a V-shaped cross-section. A marginal series with ‘reversed’ fractionation and high primary dips, similar to the marginal series of the Muskox Intrusion, occupies the lower part of the intrusion. The rocks of this series display rhythmic layering and a variety of cumulate textural types indicating that cumulate processes can take place during deposition on near-vertical dipping surfaces.
The significance of a mid-Cretaceous cobble conglomerate, Beer District, south Devon
Authors: Ali M. T.
Published: May 2009

A mid-Cretaceous cobble conglomerate in the Beer district, south Devon, is interpreted as a Lower Cenomanian beach deposit.
Vermiforichnus borings from the Ordovician of central Wales
Authors: Pickerill R. K.
Published: May 2009

The epizoan Vermiforichnus Cameron (1969b) from the Upper Ordovician (Caradoc) of the Berwyn Hills and the Welsh Borders is host-specific, occurring in association with the strophomenid Macrocoelia and the orthid Heterorthis. The spionid polychaete probably responsible for the production of the Vermiforichnus borings inhabited both live and dead individuals. In live individuals Vermiforichnus was located at the anterior margin and oriented perpendicular to the commissure, this position affording both a means of protection and a more efficient feeding position. In dead individuals population density was lower and the borings were randomly oriented. Vermiforichnus was restricted to inner—outer sublittoral environments and, as such, is a useful palaeoenvironmental guide.
Carbonate ball and pillow structures
Authors: Weaver J. D. , Jeffcoat R. E.
Published: May 2009

A liquefaction layer displaying ball and pillow structures occurs within the back reef facies of the Cawdor Limestone (P2 zone) near Wirksworth. This layer consists of pillow-shaped masses of coarse biosparite within a biomicrite matrix. The pillows are 0.6–0.8 m thick and 1.5–4.0 m across. Experiments using layers of calcareous sand above calcareous mud have demonstrated that such structures may be produced by subjecting saturated sediments to seismic shocks. These Viséan carbonate ball and pillow structures are attributed to loading, resulting from liquefaction of underlying calcareous mud during the passage of earthquake shock waves associated with the Gulf Fault.
Silurian trilobites from NE Queensland and the classification of effaced trilobites
Authors: Lane P. D. , Thomas A. T.
Published: May 2009

A trilobite fauna of Llandovery/Wenlock age is described. Five species are represented:Rhax polllnctrixgen. et sp. nov. (Scutelluidae), a warburgelline?,Sphaerexochussp.,Encrinurus?sp., and a calymenid. The morphology ofR. pollinctrixsupports the view thatBumastusis a scutelluid, and consequently that the Illaenidae, as presently conceived, is polyphyletic.
An ultramafic rock in the precambrian of eastern Sinai
Authors: Beyth M. , Grunhagen H. , Zilberfarb A.
Published: May 2009

Two small outcrops of harzburgite and asbestos-bearing serpentinite, occurring S of Di Zahav in eastern Sinai are the first record of ultramafic rocks from the Sinai Precambrian massif.
Oligocene alkaline igneous activity in NE Mexico
Authors: Bloomfield K. , Cepeda-Davila L.
Published: May 2009

Potassium-argon age determinations on rocks from the Sierra de San Carlos, State of Tamaulipas, México, which are petrographically very similar to other bodies in north-eastern México and the south-central U.S.A., indicate that a NW-trending zone of alkaline complexes, at least 1,400 km in length, stretches from the Gulf coast to southern New Mexico. This zone may be structurally related to the parallel, but somewhat younger, Rio Grande rift.
The control of the whole-rock content of CaO and Al2O3 on the occurrence of the aluminium silicate polymorphs in amphibolite facies pelites
Authors: Winchester J. A.
Published: May 2009

The contents of CaO and Al2O3 in pelites from areas subjected to amphibolite facies metamorphism have been plotted in order to discover the compositional limit of the stability field of the aluminium silicate minerals. Rocks containing kyanite or sillimanite fall within a well-defined field, while rocks plotting outside this field are devoid of aluminium silicate minerals, irrespective of metamorphic grade. With the trace of the curve bounding this field known, the position of the kyanite isograd may be more easily plotted in areas where kyanite or sillimanite are rare.
Some migmatite types and their origins, from the Barousse Massif, Central Pyrenees
Authors: Harris N. B. W.
Published: May 2009

Observations on the structure, fabrics, mineral assemblages and distributions of plagioclase compositions from migmatites of the Barousse Massif, Central Pyrenees, are related to the mode of differentiation of leucosome from melanosome. It is concluded that the majority of these migmatites have formed from recrystallization of sedimentary horizons, often accompanied by metamorphic differentiation, although some migmatites appear to have formed from anatexis or magmatic injection.
Three-dimensional isograds from the Lukmanier Pass, Switzerland, and their tectonic significance
Authors: Fox J. S.
Published: May 2009

Four mineralogical zones, corresponding to the following ‘maximum’ metapelitic assemblages

zone 1: chloritoid-chlorite-kyanite

zone 2: staurolite-chloritoid-chlorite-kyanite

zone 3: biotite-staurolite-chloritoid-chlorite-kyanite

zone 4: biotite-staurolite-garnet-chlorite-kyanite

have been mapped in the Ultrahelvetic rocks of the Lukmanier area in Switzerland. Petrographic study suggests that, despite the ubiquity of ‘disequilibrium’, the zone boundaries accord with the simple univariant equilibria

chloritoid+kyanite = staurolite+chlorite+quartz+H2O

chloritoid+chlorite+muscovite = staurolite+biotite+quartz+H2O

and chloritoid+muscovite+quartz = staurolite+garnet+biotite+H26

Using structural contours, minimum isogradic dips of 35° north have been obtained.

The Lukmanier parageneses require the Lepontine phase of Alpine metamorphism to have had a geotherma! gradient distinct from both Alpine blueschists and the Bergell contact metamorphites. The high minimum value for isograd and isotherm orientation here points to a convective heat source for the Lepontine event.
Monticules in a Jurassic Cyclostomatous Bryozoan
Authors: Taylor P. D.
Published: May 2009

Structures similar to the monticules of Palaeozoic trepostomatous Bryozoa which occur in the Jurassic cyclostome Reptomultisparsa incrustans are described. They are interpreted as having a function analogous to that inferred for monticules. A smaller proportion of zooecia open on the monticules than between them, and, of these a higher proportion are occluded.These observations lend support to the theory proposed by Banta, McKinney & Zimmer (1974) that monticules functioned as regions of exhalant current chimneys on the zoarial surfaces of Bryozoa.
Mineralogy of Precambrian Gneiss from the Bighorn Mountains, Wyoming
Authors: Heimlich R. A. , Nelson G. C. , Malcuit R. J.
Published: May 2009

Precambrian rocks throughout most of the southern part of the Bighorn Mountains, Wyoming, are dominated by a biotite-bearing plagioclase–quartz gneiss containing hornblende-rich or microcline-rich layers locally. Compositional and/or optical data are presented for plagioclase, biotite, and hornblende as well as optical and X-ray data for microcline and preliminary morphologic data for zircon in the gneiss. These data, supplemented by field and petrographic observations, suggest that the gneiss was formed under conditions of the low amphibolite facies, that late-occurring potash metasomatism accompanied the metamorphism, and that the gneiss was derived from a relatively chemically uniform parent rock.
Evolution of the granulites and sub-division of the granulite facies in Ceylon
Authors: Hapuarachchi D. J. A. C.
Published: May 2009

Three subfacies of the granulite facies are recognized: garnet–diopside–quartz subfacies; pyroxene–granulite subfacies; and hornblende–granulite subfacies The erection of a garnet–diopside–quartz subfacies follows De Waard's suggestion (1965) of a garnet–clinopyroxene subfacies. Two major divisions of the hornblende–granulite subfacies are now recognized, (i) garnet–biotite division, (ii) cordierite division. Three sub-divisions of the former are suggested on the basis of critical basic assemblages. Since wollastonite has been found to have a limited areal occurrence within the latter, a two-fold sub-division of the cordierite division is suggested on the basis of the assemblages, (a) calcite–quartz, (b) wollastonite. A seven-fold sub-division of the granulite facies is thus proposed for Ceylon rocks. An attempt is made to trace briefly the major events in the metamorphic history of the rocks supported by available geochronological evidence.
Late Pleistocene chronology and the glacial–interglacial cycle
Authors: Evans P.
Published: May 2009

Alternative time-scales differing by 25% have been proposed for the climatic sequence revealed by deep-sea cores. Both scales are based on radiometric data. Recent evidence which is here summarized favours the time-scale which gives the smaller values for the ages of late Pleistocene events; it supports the estimate of 40 ka rather than 50 ka for the average length of the principal climatic cycle.
The Greenland O18 curve: time scale and ice accumulation
Authors: Mörner N.-A.
Published: May 2009

None of the time scales hitherto applied to the Greenland O18 curve is considered reliable. The logarithmic time scales were based on the false assumption of constant glacial dynamics. The latest time scale, based on a supposed constant 2400- years cycle, seems to be based on another false assumption of constant cycles. A chronology based on indirect dating therefore seems superior.
The Porphyroclast Minerals of the Peridotite-Mylonites of St. Paul's Rocks (Atlantic)
Authors: Tilley C. E. , Long J. V. P.
Published: May 2009

Analyses, determined with the electron-probe, are given of the porphyroclast minerals of the peridotite-mylonites of St. Paul's Rocks.
The Analysis of Core Samples and a Sparker Profile from The Wash, England
Authors: Dingle R. V.
Published: May 2009

A microfaunal analysis of four Mesozoic core samples from The Wash is discussed, together with an interpretation of a continuous reflection profile. The profile demonstrates an expanded Lower Cretaceous succession compared with Norfolk and Lincolnshire and the clay facies of the Valanginian Hundleby Clay is shown to extend at least to the middle of The Wash. The other core samples are proved to be of Kimmeridgian, Barremian and Upper Albian age. Two Chalk samples are also plotted.
The Variation of Some Trace Elements in the Rosses Granite Complex, Donegal
Authors: Hall A.
Published: May 2009

The distribution of Ba, Mn, Nb, Rb, Sr and Zr has been studied in the granites of the Rosses complex. Their variation is interpreted in terms of a process of magmatic evolution involving the formation of granite magma by progressive partial fusion, and its modification during emplacement by the partial assimilation of displaced country rocks. Several greisens from the Rosses complex have also been analysed, and the changes in concentration of trace elements during greisenization are related to observed changes in mineralogy.
Geochronology of the Tristan da Cunha Group of Islands
Authors: Gass I. G.
Published: May 2009

A geological synopsis of the three main islands of the Tristan da Cunha group is given and their rate of growth by volcanic processes, and their subsequent erosion, are examined in the light of recent radiometric age data. These data, though few as yet, suggest that each island has a “life cycle” consisting of a brief constructional volcanic phase lasting less than 1,000,000 years, followed by an erosional phase of some 20,000,000 years. The possibility that other oceanic islands have had comparable histories is discussed.
Discoasters of the Blue Clay (Middle Miocene) of Malta and Gozo
Authors: Hojjatzadeh Minoo
Published: May 2009

Twenty-three species of the Family Discoasteraceae Vekshina, 1959 recovered from 18 samples of the Blue Clay at Fort Chambray, Gozo, and 31 samples from Fomm-Ir-Rih Bay, Malta, have been studied under light and scanning electron microscopes. Fourteen Middle Miocene species are reviewed, their stratigraphical ranges and importance as marker species discussed. Nine species are described as new. On the basis of the discoaster species present, a Middle Miocene age (NN.6 Discoaster exilis Zone – NN.7 Discoaster kugleri Zone) for the Blue Clay in Malta and Gozo is suggested.
Late Precambrian–Early Cambrian stratigraphic and faunal succession of eastern California and the Precambrian–Cambrian boundary
Authors: Nelson C. A.
Published: May 2009

The Late Precambrian and Early Cambrian strata in eastern California and Nevada can be divided into 3 facies – the eastern Craton, the White-Inyo, and the Death Valley. These 3 facies supply evidence of 3 trilobite zones – the Fallotaspis, the Nevadella and the Bonnia-Olenellus; the inter-relationships are outlined. Correlations with the Siberian Platform successions are discussed and the Precambrian–Cambrian boundary is tentatively placed within the beds of the upper Reed Dolomite in the White-lnyo Range.
The Precambrian–Cambrian boundary problem in Siberia and some general problems of stratigraphy (Preliminary Report)
Authors: Savitsky V. E.
Published: May 2009

Two regions are considered to be the best for the definition of the Cambrian lower boundary in Siberia – in Yakutia (the middle course of the Aldan River), in Western Prianabarye (at the Kotuikan and Kotui). The stratigraphical relationships in these 2 regions are described. Some general problems of stratigraphy are then raised (a) the need to use lithologic-facies, palaeogeography and biostratigraphy together, (b) the boundary stratotype method of delimiting chronostratigraphical subdivisions and (c) the earliest trilobite zones, the Ediacara fauna and geochronology.
The Ordovician Bryozoan (Ectoproct) Diplotrypa from Central Burma
Authors: Maw U Ba , San U Bo , Ross J. R. P. , Ciochon R. L.
Published: May 2009

New stratigraphic data for the Ordovician ectoproct Diplotrypa cf. D. westoni in the Shan Plateau region of Central Burma indicates correlation with the Trentonian of New York State.
The composition and age of basalts dredged from the Blackstones igneous centre, western Scotland
Authors: Mitchell J. G. , Jones E. J. W. , Jones G. T.
Published: May 2009

A collection of basaltic rocks has been dredged from part of the Blackstones igneous centre, a major offshore intrusion situated about 50 km SW of Mull. The basalts are mainly olivine tholeiites and are closely similar to transitional basalts found on the Inner Hebrides. The mean of four concordant K—Ar dates obtained from the lavas indicates an age of 57.1 (± 0.9) Ma. The Blackstones complex thus appears to be coeval with other Tertiary centres of the area.
A probable glacio-marine deposit of Late Ordovician—Early Silurian age from the north central Newfoundland Appalachian Belt
Authors: McCann A. M. , Kennedy M. J.
Published: May 2009

Conglomerate beds occur in an Upper Ordovician—Lower Silurian clastic sequence on the northeastern side of the Newfoundland Central Paleozoic Mobile Belt. They contain scattered pebbles and cobbles dispersed in a finely laminated sandstone and siltstone matrix. Laminations are generally 5–20 mm thick and the clasts 10–300 mm across. The laminations are locally disrupted by the clasts. These laminations have subsequently been tectonically flattened into augen around the clasts and locally disrupted by boudinage. It is concluded that these conglomerate beds represent icerafted glacio-marine deposits interbedded with turbidites which were probably deposited in a locally restricted marine environment. The deposits are interpreted on the basis of scattered fossil localities as being of Late Ordovician–Early Silurian age. They are compared with deposits of similar age elsewhere in the North Atlantic region.
Hornblende–garnet Granulites from Hatton, Ceylon
Authors: Cooray P. G.
Published: May 2009

Quartz–microperthite–hornblende–garnet–plagioclase granulites belonging to the Highland Series of Ceylon are described. The invariable presence of accessory graphite suggests their metasedimentary origin and their chemical composition indicates a possible derivation from feldspathic sandstones. Although the mineral assemblage of these granulites is diagnostic for the upper almandine–amphibolite facies, they are interlayered with orthopyroxene-bearing charnockites of the granulite facies. It is concluded that PHO was initially higher in the sandstones than in the surrounding rocks, and that it remained so during metamorphism under granulite facies conditions, thereby retarding the dehydration reactions that took place elsewhere in the vicinity.
New records of fertile Rhyniophytina from the late Silurian of Wales
Authors: Edwards D. , Rogerson E. C. W.
Published: May 2009

Whitcliffian and Downtonian macroplants of rhyniophyte morphology are described from Capel Horeb Quarry, Powys, Wales. Both floras contain Hostinetla Stur, Cooksonia Lang and Steganotheca Edwards. They are briefly compared with others of similar age, and the contribution, particularly of the Whitcliffian assemblage, to our knowledge on the early colonisation of the land by vascular plants is discussed.
The significance of potassium–argon ages in the vicinity of the charnockitic Ernabella Adamellite, Australia
Authors: Wilson A. F. , Green D. C.
Published: May 2009

Potassium–argon dates from hornblende-bearing pyroxene granulites in a large xenolith near the margin of the charnockitic Ernabella Adamellite, central Australia, are interpreted in the light of oxygen isotype studies of associated mineral phases which give a detailed thermal history of the Adamellite and associated rocks.
The trilobite genusPlacopariafrom the Ordovician of the Valongo area, North Portugal
Authors: Romano M.
Published: May 2009

The three species ofPlacoparia; P. (Placoparia) cambriensisHicks,P. (Coplacoparia) tournemini(Rouault) andP. (Coplacoparia) borniHammann have been recognized from the Ordovician of North Portugal. New subspecies ofP. (Placoparia) cambriensishave been established on the basis of differences in the pygidium and suggests the presence of two, broadly coeval, populations in western Europe during the Llanvirn. Quantitative analyses have provided information on growth patterns.
Ordovician echinoderms from Greenland
Authors: Paul C. R. C.
Published: May 2009

Ordovician echinoderms from Greenland include:Glyptocystites groenlandicussp.nov. which is distinguished from otherGlyptocystitesby a very coarse slit spacing in its pectinirhombs (1 slit per 0.365 mm) and by its ambulacral structure; ?Macrocystellasp.;Cheirocystellasp and ?Carabocrinussp. A variety of unidentified stem and cup plates of crinoids is described and illustrated.
A greenstone belt—basement relationship in the Tanganyika shield
Authors: Haidutov I. S.
Published: May 2009

An Archaean greenstone belt, occupied by rocks of the Nyanzian System, rests apparently unconformably on a basement composed of the metamorphites of the Dodoman System in the central part of the Tanganyika shield. The latter were originally metamorphosed in granulite facies. Two episodes of migmatization were imposed on this earlier crust producing two complexes of anatectic granitoids (Puma and Ikungi) which locally have a charnockitic character. Differences in structural setting suggest that they were developed in connection with two major tectonic events. A basin-like structure was built up during the second – Ikungi – in which the Nyanzian System occurs. The Nyanzian rocks are not migmatized and their juxtaposition with the migmatites suggests that they are of younger age. Another tectonism took place after deposition of the greenstones as a result of which they were intensely deformed. Two types of intrusive granites were emplaced in the greenschists upgrading them to hornfelses during this tectonism. An interesting feature is the coincidence of the general tectonic axes of these three events. For the successively established metamorphic processes in this Archaean nucleus a gradual downgrading of metamorphic facies is characteristic, showing its irreversible development.
An erosional structure in a layered dolerite dyke, West Greenland
Authors: Williams H. R.
Published: May 2009

A vertical channel structure within a layered dolerite dyke resulted from differential magmatic flow. Layering in both dyke and channel is formed of more feldspathic dolerite attributed to fluctuations in water vapour pressure and supercooling during crystallization.
Preservation and abundance of palynomorphs in Svalbard
Authors: Hughes N. F. , Harland W. B. , Smith D. G.
Published: May 2009

A summary is given of the preservation and general abundance information on palynomorphs of post-Silurian age in Svalbard. An explanation of the distribution of successful and unsuccessful palynomorph extraction is attempted, with a conclusion that varying burial history under other sediment was the principal controlling factor.
A gravity survey of Islay, Scotland
Authors: Durrance E. M.
Published: May 2009

The results of a gravity survey of Islay indicate that, with respect to a local Bouguer anomaly datum of 260 g.u., a positive anomaly of 100 g.u. occurs over the Lewisian gneiss of the Rhinns of Islay, and, immediately to the E, a negative anomaly of —120 g.u. occurs S of Bowmore. Both anomalies trend N—E to S—W. The negative anomaly is interpreted as due to the presence of a structural basin occupied by a maximum 4600 m of Bowmore Sandstones and Dalradian meta-sediments. The boundary between the Lewisian gneiss and this basin is the Loch Indaal fault. At the head of Loch Indaal this fault bifurcates, one branch continuing north-eastwards as the Bonahaven fault, the other trending northwards as the Loch Gruinart fault, All the faults are considered to possess transcurrent components. The stratigraphic position of the Bowmore Sandstones is similar to that of the supposed Torridonian sediments of western Islay.
Labechia aldonensis sp.nov.; an Ordovician stromatoporoid from Scotland
Authors: Webby B. D.
Published: May 2009

A new Ordovician stromatoporoid species, Labechia aldonensis, is described and illustrated from the Stinchar Limestone (Barr Group) of the Girvan District, Scotland.