bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stratigraphy of the Upper Devonian argillite successions in north Cornwall
Authors: Beese A. P. 
Published: May 2009

AbstractSome 880 m of grey, green and purple argillites are estimated to be present in complexly deformed Upper Devonian successions which occur in several overlapping coastal sections. Four lithostratigraphical formations are formally defined, in order of decreasing age: the Marble Cliff Limestone; Longcarrow Cove Slate; Harbour Cove Slate; and Polzeath Slate Formations. Improved correlation and biostratigraphical control is available for the two younger formations which are studied in detail. The formations range in age from lowest Frasnian to mid Famennian. Despite the intense deformation there are no major structural breaks in the successions.
Ordovician nautiloid faunas of Central and Southern Thailand
Authors: Stait B. A. , Burrett C. F. 
Published: May 2009

AbstractNautiloids from the shallow water Ordovician carbonates of Central and Southern Thailand can be grouped into five broad assemblages. 1. The Middle Ibexian fauna of indeterminate endocerids from Tarutao Island. 2. Hardmanoceras chrysanthimum (Kobayashi) of the Upper Ibexian age strata on Tarutao Island. 3. The Upper Ibexian Manchuroceras nakamense sp.nov. from Ron Phibum, Southern Thailand. 4. Wutinoceras sp., Chaohuceras? sp. of Lower to Middle Whiterockian age strata from Satun Province. 5. Wutinoceras sp., Armenoceras chediforme Kobayashi and Georgina sp. of Lower-Middle Whiterockian age strata from Kanchanaburi, Central Thailand. All of these genera occur in Australia and China.
Assemblages of calcareous algae near the Precambrian/Cambrian boundary in Siberia and Mongolia
Authors: Riding Robert , Voronova Larisa 
Published: May 2009

AbstractCalcareous algae make their first appearance near the base of the Tommotian. The oldest confirmed occurrences are of ?Gemma, Obruchevella and Renalcis in the Nemakit-Daldyn Horizon and late Yudomian of Siberia. A little higher in the sequence, in the Aldanocyathus sunnaginicus Zone of the earliest Tommotian, Angulocellularia, Bajanophyton, Batenevia, Botomaella, Girvanella, Hedstroemia, Korilophyton, Proaulopora, Subtifloria, and Tarthinia appear. Immediately above this, in the Dokidocyathus regularis Zone of the middle Tommotian, Chabakovia appears with the epiphytacean genera Epiphyton, Gordonophyton and Tubomorphophyton. There are only minor subsequent additions to this flora before the end of the Atdabanian. Kordephyton appears in the Dokidocyathus lenaicus Zone of the late Tommotian and Razumovskia in the early Atdabanian.These fossils constitute three calcareous algae assemblages (CAA 1, 2, 3) characteristic of the Nemakit-Daldyn Horizon/late Yudomian, early Tommotian, and middle Tommotian/Atdabanian respectively. Most of the genera are long-ranging, but their rapid appearance and diversification near the base of the Tommotian repesents an important event in the history of calcareous algae and augments faunal data concerning evolution and biostratigraphy near the Precambrian/Cambrian boundary.
The Precambrian–Cambrian boundary problem and its prospects, Northwest Himalaya, India
Authors: Kumar G. , Raina B. K. , Bhargava O. N. , Maithy P. K. , Babu R. 
Published: May 2009

AbstractThe Precambrian–Cambrian boundary problem is being studied in an areno-argillaceous sequence in the Kashmir and Spiti Valley, Northwest Himalaya, India. In Kashmir, a rich and diversified microbiota – cryptarchs and algae of the Late Precambrian, and low Lower Cambrian trace fossils are recorded. In the Spiti Valley, the yield of microbiota is poor and the trace fossils are late Lower Cambrian.
Sand-wave immobility and the internal master bedding of sand-wave deposits
Authors: Allen J. R. L. 
Published: May 2009

SummarySand waves are such comparatively immobile transverse bedforms because they occur in tide-induced oscillatory bottom boundary layers typified by a steady velocity-component that generally is small compared to the amplitude of the periodic part. Consequently, the net bed-material transport rates, responsible for the long-term translation of the sand waves, typically are very small compared with the larger of the instantaneous rates. Sand waves should, therefore, be marked internally by series of erosional or, under restricted circumstances, non-depositional master bedding surfaces, each such surface, together with an associated comparatively thin sediment increment, being attributable to one sand-driving tide. Studies of modern sand waves, and investigations in the stratigraphic record, lend support to this conclusion. A further consequence of the regime of intense reworking under which sand waves exist is that their component grains should be in all ways more mature, other things being equal, than particles transported the same net distance by rivers.
Hertzian fracture, a principal mechanism in the emplacement of the British Tertiary intrusive centres
Authors: Bahat Dov 
Published: May 2009

SummaryIn the British Tertiary intrusive centres emplacement of cone-sheets, ring-dykes and related magmatic bodies followed in shape and sequence the pattern of Hertzian fracture produced in the country rock by the magmatic diapir. In Ardnamurchan doming of the country rock, conic fracture and intrusion of cone-sheets started the development of the intrusive centre. Following that, pressure was reduced and strain relaxation occurred which resulted in arcuate and median fractures. These fractures were later on intruded by magma, hence ring-dykes (curved flanges) were formed. Resumption of pressure initiated the second cycle of cone fractures (and inner cone-sheets of centre 2).
The ontogeny of Failleana and the origin of the Bumastinae (Trilobita)
Authors: Ludvigsen R. , Chatterton B. D. E. 
Published: May 2009

SummaryThe metaprotaspid of the bumastine Failleana calva is similar to protaspids of scutelluids, whilst late meraspids and early holaspids of F. calva are similar to fully mature styginids. This suggests that the bumastines were derived from the styginids in the Early Ordovician and that the bumastines later gave rise to the scutelluids. Bumastus and similar Silurian trilobites are phyletic derivatives of Ordovician bumastines and not effaced scutelluids as claimed recently by Lane & Thomas. Revised diagnoses of Illaeninae and Bumastinae are presented.
Revised stratigraphy of the Mesozoic rocks of southern Cyprus
Authors: Swarbrick R. E. , Robertson A. H. F. 
Published: May 2009

SummaryRecent resurgence of interest in the Mesozoic rocks of SW and southern Cyprus necessitates redefinition of the Mesozoic sedimentary and igneous rocks in line with modern stratigraphical convention. Two fundamentally different rocks associations are present, the Troodos Complex, not redefined, a portion of late Cretaceous oceanic crust, and the Mamonia Complex, the tectonically dismembered remnants of a Mesozoic continental margin. Based on earlier work, the Mamonia Complex is divided into two groups, each subdivided into a number of subsidiary formations and members. The Ayios Photios Group is wholly sedimentary, and records the evolution of a late Triassic to Cretaceous inactive continental margin. The Dhiarizos Group represents Triassic alkalic volcanism and sedimentation adjacent to a continental margin. Several other formations not included in the two groups comprise sedimentary mélange and metamorphic rocks. The Troodos Complex possesses an in situ late Cretaceous sedimentary cover which includes two formations of ferromanganiferous pelagic sediments, radiolarites and volcaniclastic sandstones. The overlying Cainozoic calcareous units are not redefined here.
A geomagnetic investigation of Carboniferous igneous rocks at Tickenham, County of Avon
Authors: Kearey P. , Allison J. R. 
Published: May 2009

SummaryA geomagnetic survey indicates that the Carboniferous igneous rocks in the Tickenham area are more extensive than previously recognized. Inversions of the magnetic anomalies suggest the causative basaltic body is tabular in form, conforms to the regional dip and has a coplanar magnetization. The magnetization vector orientation indicates emplacement during a period of magnetic field reversal and thus at a time different from other Carboniferous igneous rocks in the region.
S-type characteristics of the Hercynian granitoids of the Central Palaeozoic Massif, Morocco
Authors: Mahmood A. , Bennani A. 
Published: May 2009

AbstractThis petrographic and chemical study of the Hercynian granitoids of the Central Palaeozoic Massif of Morocco covers the Zaër, Ment, Oulmès, and Moulay Bouazza plutons. These plutons are formed of biotite or two-mica, quartz-rich granodiorites and monzogranites containing reddish-brown, inclusion-rich biotites as the only essential mafic mineral; zoned plagioclase; and perthitic K-feldspar. The modal contents of micas and K-feldspar are highly variable. The granitoids are generally medium to coarse grained, massive; however foliated varieties are also commonly found, particularly at the contact of the' plutons with sedimentary rocks.The strongly peraluminous character of the granitoids is shown by high normative corundum and high molar Al2O3/(CaO + Na2O + K2O) ratio, and is reflected by the occasional presence of aluminosilicates.The mineralogical and chemical characteristics of the granitoids are similar to those of the S-type granites, and were inherited from the crustal source of the granitic magmas which are thought to have been generated by partial equilibrium fusion of the sandy argillaceous sediments of the Massif. The heat source for the fusion might have been provided by intrusion of mantle-derived material.
On the Bathonian (Middle Jurassic) ammonites Micromphalites Buckman and Gracilisphinctes Buckman from Kachchh, Western India
Authors: Jaitly A. K. , Singh C. S. P. 
Published: May 2009

AbstractSystematic descriptions of specimens collected from Pachchham ‘Island’, Kachchh, Western India, belonging to the genera Micromphalites Buckman and Gracilisphinctes Buckman are given. Their affinities with the different forms belonging to the above genera are discussed and described as Micromphalites aff. hourcqui Collignon and Gracilisphinctes cf. arkelli Collignon respectively. The distribution of these two genera in other regions is also briefly discussed.
Garnet and associated minerals in the southern margin of the Menderes Massif, southwest Turkey
Authors: Ashworth J. R. , Evirgen M. M. 
Published: May 2009

AbstractAssemblages with muscovite + quartz show a regular increase in grade from the Chlorite Zone at the base of the Lycian Nappe Complex to the Garnet Zone within the structurally underlying Menderes Massif. Biotite enters before garnet, which precedes oligoclase. Garnet-bearing assemblages in pelites are compared with those in re-equilibrated quartzofeldspathic gneisses, where garnet is unusually calcic (in one case approaching Gross50Alm50). Local retrograde effects are noted but no evidence is found for a polymetamorphic record in the mineral compositions. Garnet zoning, with Mn decreasing outwards, is interpreted as growth zoning; Ca decreases outwards in pelite garnets but shows the reverse effect in the gneisses. Chloritoid is common but rarely coexists with biotite, and garnet + chlorite + paragonite is found rather than chloritoid + albite. Garnet-biotite geothermometry, corrected for the effect of Ca in garnets with up to 29 mole % grossular, indicates temperatures of 530±5O°C near the garnet isograd. As in other areas, an attempt at muscovite-paragonite geothermometry gives an anomalous result. Metamorphic pressure isconsidered in the light of (i) Mn/Fe partition between garnet and biotite, (ii) Ca content of garnet coexisting with plagioclase + muscovite + biotite, (iii) Na in actinolite coexisting with albite + chlorite + magnetite, and (iv) celadonite content of muscovite which, however, shows variation due to disequilibrium within a specimen and does not provide an accurate geobarometer. Comparisons with published studies indicate a strong similarity to the Barrovian Dalradian of Scotland and lead to a tentative pressure estimate of approximately 5 kbar.
Tufted microbial (cyanobacterial) mats from the Proterozoic Stoer Group, Scotland
Authors: Upfold R. L. 
Published: May 2009

AbstractUpward-thinning stellate and polygonal carbonate structures are described and compared to modern and ancient stromatolites. Although tufted microbial mats are common in modern settings they have rarely been described from ancient rocks owing to their poor preservation potential. The preservation of these from the Stoer Group is due to early replacement by calcite before their original tufted relief could be obliterated by compaction. Associated limestones with some similar features are interpreted as flat to mamillated microbial mats.
Polymetamorphism in the Dalradian of the central Scottish Highlands
Authors: Dempster T. J. , Harte B. 
Published: May 2009

AbstractSystematic variations in both timing and conditions of metamorphism are observed in the Dalradian rocks of Central Perthshire, Scotland. Early (D2–D3 and syn-D3) relatively low-pressure metamorphism (550 °C, 7 kb) occurs in the Flat belt rocks of the Tay Nappe to the south, and later (post-D3) higher-pressure conditions (550 °C, 9 kb) dominate the Steep belt to the north. The latter appear to be superimposed on earlier low pressure assemblages (chloritoid–biotite) with the pressure increase probably relating to formation of the Tummel Steep Belt, possibly near 460 Ma. This polymetamorphism, in addition to the generally high pressures of Barrovian metamorphism throughout Perthshire, may account for the poor development of the metamorphic zonal pattern in this region compared to the eastern Dalradian.
The tectonic evolution of the Abitibi greenstone belt of Canada
Authors: Ludden John , Hubert Claude , Gariépy Clement 
Published: May 2009

AbstractBased on structural, geochemical, sedimentological and geochronological studies, we have formulated a model for the evolution of the late Archaean Abitibi greenstone belt of the Superior Province of Canada. The southern volcanic zone (SVZ) of the belt is dominated by komatiitic to tholeiitic volcanic plateaux and large, bimodal, mafic-felsic volcanic centres. These volcanic rocks were erupted between approximately 2710 Ma and 2700 Ma in a series of rift basins formed as a result of wrench-fault tectonics.The SVZ superimposes an older volcanic terrane which is characterized in the northern volcanic zone (NVZ) of the Abitibi belt and is approximately 2720 Ma or older. The NVZ comprises basaltic to andesitic and dacitic subaqueous massive volcanics which are cored by comagmatic sill complexes and layered mafic-anorthositic plutonic complexes. These volcanics are overlain by felsic pyroclastic rocks that were comagmatic with the emplacement of tonalitic plutons at 2717 ±2 Ma.The tectonic model envisages the SVZ to have formed in a series of rift basins which dissected an earlier formed volcanic arc (the NVZ). Analogous rift environments have been postulated for the Hokuroko basin of Japan, the Taupo volcanic zone of New Zealand and the Sumatra and Nicaragua arcs. The difference between rift related ‘submergent’ volcanism in the SVZ and ‘emergent’ volcanism in the NVZ resulted in the contrasting metallogenic styles, the former being characterized by syngenetic massive sulphide deposits, whilst the latter was dominated by epigenetic ‘porphyry-type’ Cu(Au) deposits.
Some remarks on the continental margins in the Aquitaine and French Pyrenees
Authors: Boillot G. 
Published: May 2009

AbstractFrom the Triassic to the Late Eocene, the Iberian Peninsula underwent three successive rotations with respect to the stable European plate, (a) Prior to the Late Aptian, a nearly 150 km southwestward motion resulted in stretching and thinning of the continental crust beneath the North Pyrenean zone, the Aquitaine Basin and the Bay of Biscay continental margins (rifting). Distensive structures trended 90° N to 130° N, and were shifted by 30° N to 50° N transform faults. (b) During the Late Aptian to Santonian interval, an approximately 400 km southeastward motion resulted in the opening of the Bay of Biscay and sinistral slipping of Iberia along the North Pyrenean transform zone (drifting), (c) During palaeocene–Eocene time, a 150 km northwestward convergent motion resulted in limited subduction of the oceanic crust of the Bay of Biscay beneath the Iberian plate, and folding of the Pyrenean chain. The folded belt resulted from squeezing of the former European and Iberian margins (rifted or transform margins, depending on the segment considered).
Palaeogene evolution of deformation in the northeastern Iberian Peninsula
Authors: Guimerá Joan 
Published: May 2009

AbstractDuring the Palaeogene Alpine compression three units were differentiated in the studied area (south of the Ebro Basin): the Catalan Coastal Range, dominated by NE–SW major basement faults with a sinistral movement; The Iberian Range, where the important basement faults have a NW–SE direction and a reverse movement (often with a dextral component); the Linking Zone, between these two ranges, where an E–W dominant structural direction is marked by an array of folds and thrusts (with a northward vergence) in the Mesozoic cover.From the analysis of both these major structures and the small-scale structures, it can be deduced that the compression in the studied area has evolved from a NW–SE direction (lower-middle Eocene) to a N–S direction and to a NE–SW one (uppermost Oligocene). The major structures are due to the N–S compression. Later, the stress-field progressively changed to a distensive regime.We suggest a relation between the compressive phases and the displacement direction of the Iberian Plate with reference to the European Plate.
Subsidence history of the Aquitaine basin determined from subsidence curves
Authors: Brunet Marie-Françoise 
Published: May 2009

AbstractThe subsidence history of the Aquitaine basin has been determined from deep exploratory well data. The contribution of sediment loading to the subsidence has been evaluated and removed, including corrections for effects of compaction, water depth and changes of sea-level but not of flexural rigidity of the lithosphere. The tectonic subsidence curves obtained indicate that the basin underwent two periods of subsidence acceleration in the Trias–Early Lias and Late Jurassic–Early Cretaceous. They are interpreted in relation to the displacements of Iberia with respect to Europe as two periods of extension followed by periods of passive subsidence due to conductive cooling of the lithosphere; the formation of the ‘flysch trough’ in the southern part of the basin is then discussed.
Carboniferous North Atlantic palaeogeography: stratigraphic evidence for rifting, not megashear or subduction
Authors: Haszeldine R. S. 
Published: May 2009

AbstractThree theories have been proposed for the origin of Carboniferous basins in Britain: megashear; tension from Rheic Ocean subduction; tension from rifting of the North Atlantic. The first two hypotheses are rejected because they do not explain the Carboniferous volcanism, Stephanian dyke swarm, Boreal marine transgressions during the late Carboniferous and Permian, Carboniferous sedimentary basin histories, basin types or basin orientations.Carboniferous volcanics were rift-related due to crustal thinning, which also resulted in the formation of sedimentary basins in the British Isles and a marine transgression of Tethyan faunas. Newly formed Carboniferous fracture lines and basin orientations showed that tension varied between east–west and northwest–southeast. Crustal fracturing in the latest Dinantian, possibly due to collision of microcontinents in the closing Rheic and Phoibic oceans with North America, led to the synchronous initiation of rift basins in East Greenland, elevation of source areas for the Millstone Grit of the British Isles, and formation of transform fault zones near Svalbard and North Spain. The narrow, rapidly subsiding, quickly changing ‘fosse’ basins which formed in these transcurrent fault zones contrast with the coeval stable, slower subsiding rift-parallel ‘saucer’ basins of the British Isles. Variations of subsidence rates in all these basins allow interpretations of crustal stress history. Brittle fracturing in the Westphalian C formed the first oceanic crust, but free oceanic spreading from Spain to southwest of the Faeroes only occurred after Stephanian dyke intrusion and crustal thinning at the Faeroes. The Norwegian Sea underwent continental crustal thinning. Ocean spreading and crustal thinning ceased in latest Stephanian times.Boreal marine transgressions advanced down the newly thinned Norwegian Sea, firstly along its northern part and then reaching the North Sea basins and Germany in the Rotliegendes and Zechstein. Synsedimetary ore deposits formed during early tensional fracturing of the crust; thick coal sequences formed in rift-parallel basins during clastic source decay of elevated rift margins; oil source rocks formed along narrow oceanic or continental rifts from the Westphalian C onwards.
Geochemical evidence for loss of Na and K from Moinian calc-silicate pods during prograde metamorphism
Authors: Tanner P. W. G. , Miller R. G. 
Published: May 2009

SummaryA total of 111 major element analyses have been made of impure calcareous rocks from the Late Precambrian Moinian sequence in NW Scotland. Samples were collected along a 36 km traverse from three stratigraphic horizons which are repeated by folding and vary in metamorphic grade from lower to upper amphibolite facies. Anorthite content of the plagioclase, which increases progressively from albite to anorthite, was assessed by X-ray diffraction measurement of 2θ (131–11); this value is used as a ‘metamorphic index’ for rocks with a CaO/Al2O3 (wt. %) ration of 0.3–0.7 and Na2O/Al2O3, < 0.35. Na2O/Al2O3 and K2O/Al2O3 ratios plotted against this index, together with the spatial relationship between metamorphic/chemical isograds and stratigraphic boundaries show that both Na (0.24–4.82% Na2O) and K (0.01–3.28% K2O) are lost from the calc-silicate rocks during prograde metamorphism. These chemical changes result in a variation of the stable mineralogy with increasing metamorphic grade and take place through the medium of the intergranular fluid.
The fenitized aureole of the Newania carbonatite, Rajasthan
Authors: Viladkar S. G. 
Published: May 2009

SummaryThe Newania carbonatite is mainly ferruginous rauhaugite with subordinate ankeritic carbonatite and dykelets of sovite. In a zone of fenitization the surrounding granite-gneiss country rock has been converted into syenitic fenite, composed mainly of feldspar and ferri-eckermannite with small amounts of albite, anorthoclase and accessory apatite.
A note on the formation of fulgurites
Authors: Williams D. J. , Johnson W. 
Published: May 2009

SummaryA phenomenon similar to the sand tube fulgurite has been observed in experimental work carried out to compact and sinter metal powders using high voltage discharges. The sand tube fulgurite is a fused quartz tube formed by the passage of a lightning discharge. Further experiments, in which a high voltage discharge was passed from a pointed electrode held above a large volume of copper powder, through to an earthed plate, give a copper product with the characteristic fulgurite morphology. This result suggests that the quartz sand can behave as a good conductor in the lightning discharge, perhaps due to conducting coatings on the surface of the sand particles.