bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pleistocene non‐marine molluscs from Cala Salada, Ibiza
Authors: Paul C. R. C. 
Published: July 2010

AbstractA 20 m Pleistocene section at Cala Salada, Ibiza, exposes three eolianites with interbedded silts and gravels. The basal eolianite has steep cross beds and represents a migrating dune, the upper two lack steep cross beds but contain abundant rhizomorphs and represent calcareous sand trapped by vegetation. Internal moulds of non‐marine molluscs occur only in the lower silts and the base of the middle eolianite. Within the lower silts are two cycles of upwards increasing diversity and abundance followed by local extinction, which probably reflect local ecological changes rather than major climatic fluctuations.The fauna contains eleven species, including Tudorella ferruginea hitherto known only from the eastern Balearics, and an extremely small form of Rumina decollate.
Historical valley alluviation in mid‐Wales
Authors: Lewin J. , Bradley S. B. , Macklin M. G. 
Published: July 2010

AbstractRecent developments on a floodplain reach of the Afon Ystwyth are analysed with the aid of five sets of maps and ten of air photographs covering the period since 1800. The area has been subjected to around 3 m of aggradation and then incision in association with historic metal mining. Analysis of sediment texture and metal concentrations allows subdivision of the mining‐associated sediments; C/M plots and shape analyses allow a distinction between proglacial, mining aggradation, and wandering river phases. The distinctive style of aggradation, involving overbank gravel splays and interfingering fines, and the lagged response of channel and sedimentation, relate largely to alterations in sediment supply rates. This has relevance for the interpretation of Quaternary fills and river terraces and for contemporary river management.
The petrology and geochemistry of intrusive alkaline rocks of Elchuru, Prakasam District, Andhra Pradesh, India
Authors: Nag S. , Chakravorty P. S. , Smith T. E. , Huang C. H. 
Published: July 2010

AbstractThe Elchuru alkaline igneous intrusion is an arcuate‐shaped ring complex, approximately 16 km2in area, cropping out in the Eastern Ghats high grade metamorphic series. It is part of an alkaline province composed of a number of intrusions which range from ijolite‐melteigite to alkali gabbro (viz. malignite, melalusitanite, shonkinite) and then to hypersolvus nepheline syenite followed by subsolvus nepheline syenite. The complex is cut by late lamprophyric dykes. A nephelinized alkaline gneiss, within the investigated complex, is the only deformed rock type and is regarded as an older unit not related to the comagmatic series. The remainder of the complex was emplaced post‐tectonically. Sovitic carbonatite is a conspicuous Iithologic unit associated with the complex.Chemical analyses of 19 selected samples for 13 major oxides and 5 trace elements (Rb, Ba, Sr, Zr and Nb) are presented to establish a geochemical model for the investigated complex.The mineralogy, petrography and geochemistry of the rocks of the Elchuru Alkaline Complex suggest that it was formed by differentiation of an initially alkali‐rich ijolitic magma as reflected in the crystallization of nepheline, kaersutitic amphibole and alkali feldspar. With progressive increase in alkali feldspar content (volume percentage) the ijolite passes to malignite and then nepheline syenites. Amphibole shows sodic enrichment from a dominant calcic variety. Pyroxene, likewise, shows sodic enrichment following the scheme salite‐ferrosalite to aegirine‐augite. The igneous cycle closes with the intrusion of biotite lamprophyre.There is a systematic increase in total alkalies (Na2O+K2O) and decrease in CaO from the early mafic rocks to the syenitic rocks. The alkali‐lime index of the complex is 48 indicating its strongly alkaline nature (Peacock 1931), and they are miaskitic in character (agpaicity index <1, Currie 1976). Such miaskitic complexes are associated with carbonatites (Heinrich 1966).
A late Devensian glaciolacustrine fan‐delta at Rhosesmor, Clwyd, North Wales
Authors: Thomas G. S. P. 
Published: July 2010

AbstractGlacigenic sediments exposed at Rhosesmor, Clwyd, North Wales, were deposited in a small proglacial lake ponded by the stagnating margin of the Late Devensian Irish Sea icesheet. Three major fades assemblages are identified and show a prograding sequence of topset, foreset, and bottomset deposits associated with two Gilbert‐style deltas stacked one above the other. The lower delta is associated with a lake level at c. 180 m OD. A subsequent ice‐marginal readvance raised the lake to c. 192 m OD, drowned the lower delta and caused the growth of a second delta by an iceward shift of facies. It is estimated that the life of the lake was of the order of 90 years during which average sediment in‐fill amounted to some 4±104 m3 per annum.
The ecological, significance of variation in the generic composition of Rawtheyan (late Ordovician) trilobite faunas from North Wales, U.K.
Authors: Price D. , Magor P. M. 
Published: July 2010

AbstractContemporaneous trilobite faunas from Rawtheyan rocks forming the local base to the Ashgill Series change in their generic composition along the outcrop between Bala and Corris. The change, although overall a very marked one, is progressive and is held to reflect original ecological control along a depth gradient between a locally elevated area around Bala and the deeper central part of the Welsh Basin. Along this intrabasinal slope three distinctive trilobite generic associations–the Ceraurinella‐Encrinuroides Association, the Nankinolithus‐Opsimasaphus Association and the Novaspis‐cyclopygid Association–succeeded each other in gradually deeper water. Faunas of all three associations differ markedly from contemporaneous faunas of shallower shelf environments.
The Westphalian D floral biostratigraphy of Saarland (Fed. Rep. Germany) and a comparison with that of South Wales
Authors: Cleal C. J. 
Published: July 2010

AbstractThe fossil plant distribution in the Carboniferous of Saarland indicates that the base of the Westphalian D is in the upper Luisenthal Formation. Two distinctive changes in the middle Westphalian D floras are noted in the Heiligenwald Formation, very similar to those reported in the Upper Pennant Measures of South‐Wales. These changes in the floras, recognizable in two distantly separated coalfields, are made the basis of a threefold biozonation of the Westphalian D. This is the most detailed biostratigraphical resolution presently available for non‐marine strata of this age.
Triassic sequences in turkey
Authors: Öunder Fuat 
Published: July 2010

AbstractIn general, Triassic rocks throughout the studied areas are dominated by limestones locally containing foraminifers and conodonts. Interbedded terrigenous clastics are present in the Lower Triassic wherever it occurs, but otherwise are restricted to the Upper Triassic sections of Hadim. The Lower‐Middle Triassic rocks of Hadim were deposited in a persistent tidal lagoon, invaded from time to time by marine faunas when the enclosing barrier shoal was breached. At other times, the lagoon became very shallow and hypersaline but never dried out completely. Occasionally the lagoon was filled with clastics deposited by sheet‐floods from the land. At the beginning of the Upper Triassic, tectonic uplift of the hinterland resulted in a massive supply of terrigenous gravels and sand to the marginal lagoon. When this supply ceased, marine influence reasserted itself, forming a semi‐enclosed sea.
The stratigraphy of the arenig series in the Aberdaron to Sarn Area, Western Llŷcn, North Wales
Authors: Beckly A. J. 
Published: July 2010

AbstractA new interpretation of the Arenig succession in the Aberdaron area is presented based on biostratigraphical correlation. A lithostratigraphy based on section correlation is presented, and three subareas are identified, each with a different stratigraphy.The Sarn Formation comprises the basal ‘flaggy’ sandstone unit in all three areas but is diachronous: in the south it underlies a Moridunian fauna whilst north of the Bryncroes fault it comprises the majority of the Arenig succession and is probably Fennian in age. The Aberdaron Formation is restricted to the south and is dominated by laminated siltstone. The Wǐg Member, a mudstone unit at the base with a Mordunian fauna is found only to the east of the Wǐg–Nefyn fault, whilst the breccio‐conglomerate Porth Meudway Member, at the top of the formation, is restricted to the west of the fault and is probably Fennian in age. The Arenig–Llanvirn boundary is approximately marked throughout the area by a tufaceous unit termed the Carw Formation.The new correlations require the repetition of the succession by a previously unrecognized NNE–SSW trending fault. The junction with the Mona Complex west of Aberdaron is considered to be predominantly faulted.The two subareas south of Bryncroes are sufficiently similar to suggest both belonged to the same deepening basin, probably initiated in the Moridunian. The absence of the Aberdaron Formation and the development of contemporary shallower water facies to the north is taken to indicate this area lay on the footwall of a normal fault bounding the basin to the northwest.
The clew bay group: A displaced terrane of highland border group rocks (Cambro‐ordovician) in Northwest Ireland
Authors: Max Michael D. 
Published: July 2010

AbstractMarine turbidites, tuffs, black mudstones and conglomerates of the Cambro‐Ordovician Clew Bay Group, were deposited in the E–W elongate transtensional Clew Bay Graben that is centred on Clew Bay, NW Ireland. The group is characterized by extensive sedimentary deformation and mass movement on slides; olistostromes, autoclastic breccias and course proximal turbidites are interbedded with apparently less disturbed but often overturned sediments.The Clew Bay Group lies structurally above serpentinized dunite/harzburgite breccias, schistose carbonate peridotites, and other basic and ultrabasic igneous rocks that have ophiolitic geochemical affinities; the sediments may have been in part deposited upon oceanic crust. Ophiolites and sediments that now rest on the Clew Bay Thrust abut Silurian shallow water strata in which the main tectonothermal history, associated with sinistral transcurrent faulting along the thrust zone, is dated at about 410 Ma. The sole thrust dips northward and coalesces with a major deep structure along the Fair Head‐Clew Bay Line (FCL) that is the western continuation of the Highland Border Fault of Scotland. Blueschist relics in the Dalradian immediately to the north of the FCL indicate that subduction was active early in the history of the late Cambrian–early Ordovician Grampian orogeny. The Clew Bay Thrust was a sinistral, transpressional shear zone late in its history, but it probably originated as an obduction complex.The Clew Bay Group cannot be traced into sedimentary, metamorphic or structural continuity with the adjacent Dalradian to the north or Ordovician and Silurian rocks in the South Mayo Trough to the south. It should be considered as a distinct terrane (Clew bay Terrane) or a subterrane of Highland Border‐type rocks along the southern margin of the Grampian Terrane.
Revised and supplemented data on Gibbs' free energies of substances at the parameters of the Earth's mantle
Authors: Ostrovsky I. A. 
Published: July 2010

AbstractNew (revised) data on thermodynamic properties of 60 substances are calculated by extrapolating their compressibilities and calorific properties up to 4000 K and 1 Mbar. Stability of pyrrhotite throughout the mantle supports Goldschmidt's idea about a sulphide zone between the mantle and the core. Such a zone could serve as a primary source of ores. Volatile H2O and H2S are stable throughout the mantle. Some hydrocarbons decompose into a mixture of methane and carbon over a wide range of pressures and temperatures. Natural oil may be regarded as a mixture of metastable hydrocarbons. FeO does not dissociate into a mixture of Fe2O3and Fe at high pressure and temperature. Alkali‐free carbonate magmas may arise in the mantle. The greater the proportion of iron‐silicates in the mantle, the more probable is the existence of a ferrous‐ferric garnet zone at great depth.
Environmental changes in the Hirnantian (upper Ordovician) of the Prague Basin, Czechoslovakia
Authors: Brenchley P. J. , Štorch P. 
Published: July 2010

AbstractSedimentary sequences through the uppermost Ordovician (Hirnantian), Kosov Formation, are described. The Kosov Formation is a shale‐dominated formation with two thin horizons of sandy diamictites near the base and two ‘flysch’ units separated by shales forming the main part of the formation, which is overlain abruptly by Silurian graptolitic shales. The diamictites are interpreted as of glaciomarine origin, probably deposited from coastal winter ice. The flysch units have many beds with hummocky cross‐stratification and wave‐ripples indicating deposition from storm generated currents above storm wave‐base. The shales between the two flysch units have thin interbedded sandstones and siltstones with mainly unidirectional current structures, but also some wave‐ripples, suggesting deposition around storm wave‐base.The sequence shows clear evidence of two regressive phases, the second of which is the more pronounced, followed by rapid transgression near the Ordovician/Silurian boundary. The regressions and subsequent transgression are interpreted as being caused by Hirnantian glacioeustatic changes rather than being tectonic in origin.The importance of the glaciomarine diamictites is that they record the onset of cold climatic conditions in the region as being early Hirnantian. The disappearance of most of the fauna at about the same time might reflect the influence of low temperatures on faunal diversity, and could have significance for the end Ordovician extinction.
Diagenesis of the Gully Oolite (Lower Carboniferous), South Wales
Authors: Searl Alison 
Published: July 2010

AbstractDeposition of the Gully Oolite was locally interrupted by emergence and a regionally extensive palaeosol is present at the top of the unit. Early diagenetic phases include isopachous, fibrous submarine cements, nonluminescent vadose cements, and mixing zone dolomite. Subsequent nonferroan phreatic cements are non‐ to dully luminescent and in restricted vertical intervals predate significant compaction. More usually, however, phreatic cements postdate extensive overpacking of allochems. Ooid isotopic composition (δ18O=‐7·80° to ‐3·10° and δ13C = ‐2·38° to +3·28°) is similar to that of associated phreatic cements and the data suggest that the bulk of ooid stabilization and cementation occurred within meteoric groundwaters. The extensive allochem overpacking appears to have occurred during the first few tens of metres of burial and intergranular macroporosity was eliminated prior to deep burial. Fracturing of the Gully Oolite during the Hercynian Orogeny and subsequent post‐orogenic uplift led to localized dolomitization, several generations of calcite veins, and the restricted occurrence of 18O depleted cements in inter‐ and intragranular microporosity. Some of the veins clearly relate to Triassic exhumation of the Carboniferous Limestone, but others may be related to post‐Mesozoic uplift and erosion of South Wales. Fracture‐associated dolomitization may have occurred within a large‐scale post‐orogenic groundwater system, with Mg2+ being supplied through the release of deeply buried diagenetic brines.
Provenance of late Ashgill (Hirnantian) fine‐grained sediments and pebbles in the Welsh Basin: A ND and SR isotope study
Authors: Leng M. J. , Evans J. A. 
Published: July 2010

AbstractThe isotope characteristics of interbedded fine‐grained sedimentary rocks and pebbles from an Ashgill sequence in the Welsh Basin show that they have different provenance. Gondwana‐derived continental crustal material dominates the Nd‐Sr isotope signatures of the fine‐grained rocks whereas the pebbles sample the Avalonian basement. Detritus from Gondwana and Avalonia accounts for the isotopic composition of most of the lower Palaeozoic sedimentary rocks of Southern Britain and this suggests that any contribution from the reworking of Lower Palaeozoic volcanic rock is minimal.
Petrology of basic and intermediate orogenic granitoids from the Sila Massif (Calabria, southern Italy)
Authors: Caggianelli A. , Moro A. Del , Piccarreta G. 
Published: July 2010

AbstractHercynian gabbroic, dioritic and tonalitic rocks crop out in the neighbourhood of Rovale (Sila Grande, Calabria). They make up a crude rectangular outcrop with the western part consisting of gabbroic rocks and the eastern of dioritic and tonalitic rocks. They come into contact with medium to high grade metapelites on the western side and with heterogeneous granodiorites on the other sides. In the gabbroic body both opx ± ol bearing cumulates and amphibole differentiates occur and are characterized by the widespread presence of brown pargasite. Sporadic magmatic to subsolidus corona textures between olivine and plagioclase or orthopyroxene and plagioclase can be observed and their preservation clearly suggests a post‐tectonic emplacement for the gabbroic magma. Diorites and tonalites display hypidiomorphic textures free of olivine and orthopyroxene and bearing green Mg‐hornblende. The granitoids, on the basis of chemical data, display orogenic features of the continent‐continent collision type. The gabbroic rocks have high Al tholeiitic composition and fractionation of orthopyroxene and plagioclase played an important part in their evolution.The Rb/Sr isochron method did not give a precise emplacement age for the granitoids as a whole. Initial 87Sr/86Sr ratios (at 290 Ma) are higher in the gabbroic body (0.7091–0.7095) than in diorites and tonalites (0.7083–0.7092). Thus gabbroic rocks appear more displaced than diorites and tonalites towards crustal isotopic composition. The eNd data seem to confirm this feature, thus suggesting that the gabbroic rocks and diorites derived from distinct mantle magma batches. Interestingly, small isotropic gabbroic masses occur within the diorites and show general features that allow them to be considered as possibly parental with respect to the host diorites. The evolution to the dioritic composition might have occurred through fractionation and minor mixing with a more acidic component such as the northern granodiorites.Geochemical, Sr and Nd isotopic data indicate a scenario of a composite plutonic body formed by distinct magma batches of mixed crust and mantle origin.
Freshwater tufa stromatolites in the basal Purbeck Formation (Upper Jurassic), Isle of Portland, Dorset
Authors: Perry Christopher T. 
Published: July 2010

AbstractRecent interpretations of the tufaceous limestones from within the ‘Caps Beds’ on the Isle of Portland have suggested a depositional environment of intertidal flats and lagoons with typically higher than normal marine salinity levels, a stark contrast with earlier ideas of a freshwater origin. However, evidence is presented in this paper to show that these deposits are indeed most likely to be freshwater in origin. The micro‐fabrics observed are typical of those seen in freshwater tufas forming at the present day, and contrast with those observed within intertidal/subtidal stromatolites. Furthermore, the Portland deposits lack syndepositional evaporite deposits, they lack recognizable intertidal deposits, and any lagoonal sediments observed are depositionally distinct from the tufas. Finally, the soil horizons observed are clear evidence of periodic subaerial exposure and isolation from marine influences.Four facies types are identified on Portland: (1) tufaceous limestone; (2) littoral grainstones; (3) subaerial stromatolites; and (4) paleosols. Each facies is repeated a number of times through the sequence, and evidence is presented to show that these formed in a marginal marine setting as a response to a series of minor transgressive (soils to freshwater lakes/lagoon to saline marine/lagoonal) and regressive events (saline marine/lagoonal to soils).The tufa stromatolite deposits themselves, which are often developed around cylindrical holes (representing former tree trunks and branches), are shown to have developed seasonally, by the precipitation of carbonate, due to microbial activity within the freshwater lake environment. Precipitation appears to have been most intense around tree bases (and any associated vegetation), where an active biofilm developed on the underlying soil substrate. Two distinct textures are recognized in this material: (1) micro‐porous and (2) macro‐porous. These developed together in a crudely laminated, semi‐concentric pattern around the holes and together may represent a seasons growth of tufa.
Contrasting sediment gravity flow processes in the late Llandovery, Rhuddnant Grits turbidite system, Welsh Basin
Authors: Clayton Chris J. 
Published: July 2010

AbstractThe Rhuddnant Grits turbidite system was deposited within an elongate, fault‐bounded trough in the late Llandovery (Telychian) Welsh Basin. Two groups of sandstones are identified within the system: high‐matrix sandstones and laminated sandstones. The high‐matrix sandstones are medium to very thick bedded, fine to very coarse‐grained muddy sandstones. The high‐matrix sandstone beds are almost entirely structureless and have several features indicative of deposition from high density turbidity currents, probably undergoing late stage debris flow behaviour (e.g. grain size discontinuities, inverse grading, floating clasts). The laminated sandstones are thin to very thin bedded, fine‐grained and have a distinctive mud/silt lamination. Tractional structures and convolution are common in these beds. They were probably deposited by slow moving, dilute turbidity currents. Dissimilar palaeocurrent vectors and estimates of flow properties from the two types of sandstone support the contrasting nature of the depositing flows. A coarsening and thickening upwards trend is identified in the laminated sandstones of the Rhuddnant Grits Formation. This trend is not reflected in the high‐matrix sandstone beds. Although the high‐matrix sandstones appear in packets or groups within the laminated sandstone background, they were otherwise deposited in an entirely random manner throughout the exposed system. This may suggest that the two types of sandstone are the result of different triggering mechanisms at source, or of contrasting flow properties developed early in the flow histories.
Diagenesis of diatomite from the Kolubara Coal Basin, Baroševac, Serbia
Authors: Obradović J. , Hein James R. , Djurdjević J. 
Published: July 2010

AbstractDiatomite associated with the Kolubara Coal Basin was studied to better understand early stage silica diagenesis of shallow water deposits. The Kolubara Basin consists of Neogene siliciclastic rocks, diatomite, marlstone and rare carbonates. Palaeozoic metamorphic and Mesozoic sedimentary and igneous basement rocks are transgressively overlain by Upper Miocene sandstone, siltstone, shale and mudstone. This Upper Miocene section is transgressively overlain by the Pontian section, which contains diatomite and coal beds.White and grey diatomite forms beds 0.7‐2.2 m thick that are continuous over an area of about 2 km2. Siliceous rocks vary in composition from diatomite (81‐89 per cent SiO2) to diatom‐bearing shale (58‐60 per cent SiO2). Siliceous deposits are laminated in places, with the laminae defined by variations in clay minerals, organic matter and diatoms. Diatomite shows only incipient diagenesis characterized by the fragmentation of diatom frustules, the minor to moderate corrosion of frustules and the formation of minor amounts of opal‐A' (X‐ray amorphous inorganic opal) cement. The low degree of diagenesis results from the young age of the deposits, low burial temperatures and possibly also from the presence of abundant organic matter and the dissolution of kaolinite. The presence of only weak diagenesis is also reflected by the characteristically poor consolidation of the rocks and low rank of the associated coal.