bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ordovician rocky shoreline deposits–the basal Trenton Group around Quebec City, Canada
Authors: Harland T. L. , Pickerill R. K. 
Published: July 2010

AbstractAround Quebec City the lowest Trenton Group sediments rest directly upon a highly irregular Precambrian surface and represent the deposits of a high‐energy, irregular, rocky shoreline which developed as the Ordovician sea onlapped a major positive topographic feature known as Montmorency Promontory. The complicated lithofacies mosaic developed along this shoreline consists of: (1) Arkosic sandstones, representing reworked regolith and marginal marine elastics; (2) Solenopora gravels, which comprise partly reworked colonies from the bare rock substrate and partly reworked algal maerls; (3) Fine‐grained limestones, which were deposited in low energy environments between and in the lee of numerous islands and shoals; (4) Skeletal limestones, representing island fringing shoals and ephemeral beaches, with extensive thickets of the ramose bryozoan Hallopora; (5) Bryozoan liméstones, which represent low‐energy, subtidal deposits with abundant delicate bryozoans; and (6) Coquina limestone lenticles, which accumulated in channels cut into the subtidal Bryozoan limestones. The absence of older Ordovician and Cambrian sediments in the vicinity of Quebec City indicates that Montmorency Promontory at the time of deposition of these Trenton deposits was probably manifested as a rugged archipelago. This represented the remnant of large‐scale topographic highlands which had developed at the continental margin during the late Precambrian in association with extensional rifting, transform faulting, and the inception of the Iapetus Ocean. Gradual subsidence of this topographic high and the development of the rocky shoreline relates to the subsequent development of a compressional system and initiation of ocean closure in the early Middle Ordovician.
Petrogenesis of the gabbros from Mt. St. Hilaire, Quebec, Canada
Authors: Greenwood R. C. , Edgar A. D. 
Published: July 2010

AbstractMt. St. Hilaire occurs as a small funnel‐shaped intrusion in the Monteregian petrographic province of Quebec and consists of alkali gabbros and later nepheline syenites. Based on field relations, petrography, and geochemistry, five types of gabbro are recognized. In order of intrusion these are: leucogabbro, foliated gabbro, kaersutite‐biotite gabbro, kaersutite gabbro, and a gabbro‐melagabbro series. Based on analyses of the early‐forming ilmenite‐titanomagnetite, the gabbros crystallized under high fO2 conditions which lead to subsequent crystallization of olivines with high MnO contents. Fractionation of ilmenite and titanomagnetite was a major control on the Ti and A[TV]concentrations in the clinopyroxenes. Plagioclase compositions in the gabbros became richer in Ab contents in the sequence gabbro‐melagabbro to leucogabbro. Whole‐rock analyses suggest that the parental magma of alkali basaltic composition was fairly evolved prior to emplacement. Lack of olivine in the cumulate gabbro‐melagabbros and low Ni and Cr in all gabbros may reflect either extreme olivine fractionation and/or a very low olivine content in the source material for these basalts. Differentiation of the gabbros occurred both pre‐ and post‐emplacement, probably by a process of crystal‐liquid fractionation at depths between 3‐5 and 8 km. This is in accordance with geophysical measurements for other Monteregian intrusions. A model is presented for the mechanism of emplacement.
Age of the Lough Talt and Easky adamellites in the central Ox Mountains, N.W. Ireland, and their structural significance
Authors: Long C. B. , Max M. D. , O'Connor P. J. 
Published: July 2010

AbstractThe Lough Talt and Easky adamellites in the north‐central Ox Mountains inlier were originally regarded as being nearly synchronous in age of emplacement with the more strongly deformed c. 480 Ma Ox Mountains granodiorite. They are now shown by Rb‐Sr whole‐rock dating to be significantly younger at c. 400 Ma. This recognition of the emplacement of late Silurian/early Devonian Newer Caledonian granites in the central Ox Mountains inlier indicates that the thermal overprinting by the adamellites of the regionally metamorphosed Ox Mountains succession is not an early Ordovician event. Earlier interpretations, using deformationai events and igneous intrusions, advanced by others to suggest that the Ox Mountains succession is pre‐Caledonian are now greatly weakened since the deformationai sequence in the Ox Mountains succession is now known to span a longer period of time, ranging from Grampian (late Cambrian to early Ordovician) to Caledoniansensu stricto, and therefore leaves fewer events to have occurred prior to the early Ordovician emplacement of the Ox Mountains granodiorite.
Ordovician and Silurian coronates (echinodermata) from Czechoslovakia
Authors: Paul C. R. C. 
Published: July 2010

AbstractCoronates form a small but distinctive group of lower Palaeozoic echinoderms, most closely related to eublastoids. The coronate fauna of Czechoslovakia includes Mespilocystites bohemicus Barrande 1887 from the Lower and Middle Caradoc, characterized by a conical theca, coronal processes which diverge markedly upwards, and distinctly angled radial furrows; Stephanoblaslus mints (Barrande 1887), from the Wenlock, typified by an elongate bud‐shaped theca with three radiating keels at the base and a very narrow stem; and ‘Stephanocrinus’ gemmiformis (Hall 1852) from the Ludlow, with a cup‐shaped theca and low coronal processes. ‘S.’ gemmiformis has not previously been reported from outside North America or above the Wenlock.
The geometry of ductile conjugate fold systems in the Ardnamurchan Moine, Scotland
Authors: O'Brien Brian H. 
Published: July 2010

AbstractFour ductile phases of superimposed deformation are regionally mappable in the Ardnamurchan Moine in the Western Highlands of Scotland. These deformations are recognized on the basis of their individual geometrical characteristics and are named, in ascending order, the Kentra phase (D1), the Ardtoe phase (D2), the Glenmore phase (D3), and the Claish phase (D4). Non‐systematic earlier structures (pre‐D1), possibly coeval with the climactic metamorphism, are locally observable. Folds and fabrics produced by the D2, D1, and D4 deformations, however, developed as conjugate sets.There is a significant spatial variation in the distribution and intensity of each of the D1‐D4 phases. The regional deformation of the Moine schists is notably inhomogeneous due to the nature of the D1‐D4 incremental strains. In the areas affected by large finite strains, pervasive, normally composite LS‐fabrics are developed. In the areas that persistently suffered negligible strain increments, right‐way‐up rocks commonly display several mineral foliations lying at various angles to bedding. The conjugate systems of folds and fabrics appear to be related to the evolution of a ductile shear belt in Ardnamurchan.
Optimized similarity matrices applied to the study of carbonate rocks
Authors: Hennebert Michel , Lees Alan 
Published: July 2010

AbstractThe primary and early diagenetic components of carbonate rocks are commonly arranged systematically in a sort of ‘relay’ along a gradient formed by one or several environmental factors. Such a relay, if present, can be revealed by the optimization of a matrix of similarity coefficients. The technique presented uses presence/absence data and is simple and rapid. An illustration is given using data from some Dinantian limestones in southwest Britain.
Facies variation in a Late Pleistocene supraglacial outwash sandur from the Isle of Man
Authors: Thomas G. S. P. , Connaughton M. , Dackombe R. V. 
Published: July 2010

AbstractThe Orrisdale Outwash Member was deposited during retreat of the Late Devensian Irish Sea ice‐sheet in a series of diachronous marginal sandur formed on an unstable, ice‐cored supraglacial topography. Sedimentation was controlled by dead‐ice ridges running parallel to the ice‐margin but as buried ice melted the topographic constraints diminished and individual sandur systems widened and coalesced. The sediments are characterized by very rapid lateral and yertical facies variation caused by channel migration, abandonment, and adjustment to a rapidly‐changing ice and sediment substrate. Facies assemblages consequently show marked lateral transition from high energy, laterally impersis‐tent, gravel dominated longitudinal bar sequences to extensive, low‐energy overbank flood basin successions.
The Late Devensian glaciation along the border of northeast Wales
Authors: Thomas G. S. P. 
Published: July 2010

AbstractThe glacigenic succession along the border of northeast Wales records the advance, coalescence and subsequent uncoupling of Welsh and Irish Sea ice‐sheets during the Late Devensian cold stage. During coalescence, extensive basal tills were deposited and considerable diversion of pre‐existing drainage was accomplished by subglacial meltwater. Analysis of borehole data and quarry exposure indicates that a complex assemblage of ice‐contact, proglacial fluviatile and lacustrine environments was developed during uncoupling and subsequent retreat. Neither of the previously proposed models for the formation of the so‐called Wrexham ‘delta‐terrace’ are adequate to explain the wide variety of sedimentary successions observed and the feature is a complex, diachronous structure that reflects rapidly changing depositionai conditions, including ice‐front alluvial fans, sandar and proglacial and ice‐contact lakes, formed at the margin of a retreating ice‐sheet.
INTAL–an expert system for the identification of igneous rocks in the hand specimen
Authors: Hawkes Donald D. 
Published: July 2010

AbstractINTAL is an expert system which will identify igneous rocks in the hand specimen on the basis of a description given to the computer by an inexperienced geologist. It assumes only that the user can identify the common rock‐forming minerals and has a rudimentary knowledge of the jargon of an igneous petrographer. The computer has no control over the user's initial description, which is freely written in English, and only partial control over any subsequent interactive dialogue. INTAL is programmed in BASIC and may be used on a small microcomputer. The program works by repetitively scanning all user input for significant keywords until the attributes of a production rule are assembled and the rock is identified.
The Courceyan stratigraphy of the Pallaskenry Borehole, County Limerick, Ireland
Authors: Somerville Ian D. , Jones Gareth L. I. 
Published: July 2010

AbstractThe Pallaskenry Borehole, Co. Limerick, Ireland provides an almost complete Courceyan (Dinantian) succession from Old Red Sandstone facies up to Waulsortian limestones. A revised lithostratigraphic‐al nomenclature for this succession is presented. Examination of the conodont and coral faunas in the borehole has enabled biozones to be defined which can be recognized throughout the Limerick Province. Biostratigraphical correlations are made with Courceyan successions at Hook Head, Co. Wexford, in the Mendip Hills and in Knap Farm Borehole in the Southwestern Province of Britain. Conodont taxa show a clear distinction betweeen the shelf faunas of the Limerick Province, Hook Head and eastern Mendip, and distal shelf faunas from south Cork, Knap Farm and Dinant, Belgium, which probably reflect their different palaeogeographical positions.Acknowledgements. The authors wish to express their thanks to Professor G. D. Sevastopulo, Drs. R. L. Austin, J. R. Nudds and P. Strogen and Mr. M. Mitchell for constructive criticism of the manuscript. We would also like to thank Dr. T. R. Reilly, Mr. C. McDermot and Dr. A. Sleeman of the Geological Survey of Ireland, and Dr. M. E. Philcox for fruitful discussion on the Iithostratig‐raphical nomenclature. G. LI. Jones was a Research Fellow at Trinity College, Dublin during the period of this work. He was funded through the Upper Palaeozoic Atlas of Ireland (UPAIR) Project, financed by the Department of Energy and administered through the Geological Survey of Ireland and Trinity College. He gratefully acknowledges the organization and supervision provided by Professors C. H. Holland and G. D. Sevastopulo and Dr. D. Naylor; and the assistance with conodont processing given by Ms. B. Thornbury. Thanks are also extended to Mr. J. Kennedy and Mr. P. Moffat for assistance with the diagrams.
The shipway limestone of gower: Sedimentation on a storm‐dominated early carboniferous ramp
Authors: Faulkner T. J. 
Published: July 2010

AbstractA detailed sedimentary study of the Lower Carboniferous (Courceyan) Shipway Limestone Formation at Three Cliffs Bay on the Gower Peninsula (South Wales) has shown that the bioclastic limestones represent a storm‐dominated sequence that contains the storm‐related sedimentary structure hummocky cross‐stratification (HCS). Conformably overlying the Shipway Limestone is a cross‐stratified oolitic sandbody with evidence of subaerial exposure. Six sedimentary lithofacies are identified in these two formations which record a distal to proximal, shallowing‐upward trend that passes from beneath mean wave‐base to above fairweather wave‐base.The shallow marine facies model constructed by Wu (1982) from his study of the Lower Carboniferous limestone sequences of South Wales is re‐evaluated. Modifications proposed for the model include the addition of two distal tempestite facies and a proximal oolite sand body. The Shipway Limestone and Brofiscin Oolite record the first major, basin‐wide, shallowing‐upward phase of the Lower Carboniferous in South Wales.
Pedogenic dolomites from the oolite group (Lower Carboniferous) South Wales
Authors: Searl Alison 
Published: July 2010

AbstractWithin the Lower Carboniferous Oolite Group of South Wales dolomites occur as 0.1 to 3 m thick stratiform bodies, sharply bounded against both underlying and overlying limestones. They contain rootlets and other plant remains and are often laterally equivalent to calcrete horizons. The dolomites are interbedded with thin coals and organic‐rich shales. In thin section a fine‐grained, xenotopic, slightly ferroan, inclusion‐rich ‘early’ dolomite forms a matrix to scattered moulds after ooids, shells, and evaporite minerals. The moulds are filled with ferroan calcite, early dolomite, and ‘late’ strongly ferroan saddle dolomite. The early dolomite is highly subzoned under cathodoluminescence whilst the late dolomite is nonluminescent. Whole rock analyses have δ18O = −5.95%, to −0.80%, and δ13C = +0.50%, to +2.80%. The early dolomite is believed to have precipitated from low sulphate, low Eh fluids within the waterlogged soil of a schizohaline coastal swamp. The late dolomite may also have formed within the pedogenic environment as a precipitate from highly evolved swamp waters, heavily enriched in organically‐derived compounds. Alternatively the later dolomite may have a hydrothermal origin as is more commonly associated with saddle dolomite.
High‐level peperitic sills in the English Lake District: Distinction from block lavas, and implications for borrowdale volcanic group stratigraphy
Authors: Branney Michael J. , Suthren Roger J. 
Published: July 2010

AbstractCriteria by which such sills can be distinguished from block lavas include discordance and fault‐controlled geometry, vesiculation and homogenization of sediments adjacent to upper contacts, and the presence of pillows or peperites at upper contacts. Because sills do not always show these characteristics in the field, an extrusive origin for a sheet should be demonstrated and not assumed. However, it is not always possible to make the distinction, in which case the non‐genetic termsheetcan be usefully applied.Field studies suggest that a substantial part of the Borrowdale Volcanic Group is composed of sills. Thus previously erected lithostratigraphic schemes may not correctly indicate the sequence of magmatic events, and the correlation of locally defined stratigraphies will not be possible until the regional importance of high‐level intrusive bodies has been established.
The North cotentin shear‐zone (Normandy‐France): Variscan mobilization of the cadomian basement and its palaeozoic cover
Authors: Dissler E. , Gresselin F. 
Published: July 2010

AbstractDetailed structural analysis of the northern part of the Cotentin Peninsula provides evidence for major Variscan reworking of Proterozoic structures. Two stages in the regional evolution of the Variscan orogeny are distinguished: the Palaeozoic Siouville Syncline was formed before the development of a south‐facing ductile overthrust. This latter stage is dated as Carboniferous in age from its relationship with the synkinematic intrusion of the Barfleur granitic pluton.
The Distribution of Chadian and earliest Arundian strata in North Wales: Implications for Dinantian (Carboniferous) lithostratigraphy and palaeogeography
Authors: Davies J. R. , Riley N. J. , Wilson D. 
Published: July 2010

AbstractThe late Chadian Foel Formation, previously thought to be confined to the Dyserth area of North Wales, forms a poorly exposed but persistent basal unit to much of the Dinantian crop east of the Clwydian Range, necessitating a revision of the local lithostratigraphy. The formation comprises a peritidal heterolith which, together with the lowest few metres of the overlying Llanarmon Limestone, yields microfossil assemblages diagnostic of the Eoparastaffella Cf4α Subzone. Succeeding strata, containing the lowest archaediscid foraminifera, provide the first record of Cf4β assemblages from North Wales and establish an early Arundian age for these beds.The Foel Formation was deposited as an aggradational sequence on the northern flank of St. George's Land during a pulsed transgression which began in late Chadian times. The widely recognized basal Arundian transgression is represented by the contact between the Foel Formation and overlying platform carbonates. The latter overlap the Foel Formation in the southernmost part of the Clwydian crop demonstrating, for the first time, southwards onlap on the northern side of the Bala–Bryneglwys Fault System.
Wrench faults, pull‐apart basins, and volcanism in central Oregon: A new tectonic model based on image interpretation
Authors: Gutmanis J. C. 
Published: July 2010

AbstractA tectonic study of the Newberry Crater region of central Oregon has been based on the interpretation of Landsat Thematic Mapper imagery. Two major faults, the Brothers‐Tumalo and Eugene‐Denio Faults, pass NW‐SE through the region and step to the right at the eastern margin of the Cascades Range. Dextral wrench faulting on these structures during the Tertiary controlled the formation of the La Pine Basin, a pull‐apart structure containing Tertiary and Quaternary sediments and volcanics. Tertiary wrench faulting appears to have been associated with rotations of crustal blocks at a plate margin, but was superseded in the Quaternary by extensional faulting of the Basin and Range province. Newberry Crater and other major bimodal volcanic centres in the NW Cordillera (Crater Lake, Medicine Lake, Mt. St. Helens) seem to have a similar tectonic setting in crustal pull‐aparts. A relationship between magma type and fault trend at Newberry and Medicine Lake is suggested.
Palaeoecology and significance of barnacles in the mid‐Pliocene Balanus Bed of Tobago, West Indies
Authors: Donovan Stephen K. 
Published: July 2010

AbstractThe Balanus Bed of the Rockly Bay Formation (mid‐Pliocene) of Tobago is a sequence of orange‐brown sands with laterally equivalent muds. The invertebrate macrofauna is dominated by the balanid barnacle Megabalanus tintinnabulum (Linnaeus) sensu lato, with associated oysters, pectinaceans, gastropods, bryozoans, regular echinoids, and rare crabs and sharks. Vertical burrows in muddier substrates are good evidence that this assemblage was living littorally or shallowly sublittorially. Previous analyses of the Rockly Bay Formation of the type area have erroneously suggested that it represents a lenticular deposit. It is now recognized to be a transgressive unit, unconformable on the underlying Mesozoic basalts. The sediment of the Balanus Beds was derived from the in situ weathering of basalts, producing a gradation from sandy (near shore) to muddy substrates. Balanids grew singly on the weathering basalt, but suitable substrates for attachment in the muddy environment were rare, so barnacles are found clustered in close association. The primary substrates for attachment in the muddy environment were disarticulated balanid plates, mollusc valves and small pebbles. Although the base of the Formation is not seen in Rockly Bay, a basal conglomerate overlain by a horizon of dissociated valves of the large ark Anadara patricia (Sowerby) is exposed in nearby Little Rockly Bay. Apart from the two fossiliferous horizons mentioned, the Formation is barren of marine microinvertebrates. The Rockly Bay Formation appears to have formed in response to the mid‐Pliocene rise in sea level. Horizons dominated by balanids may be useful indicators of sea‐level rise, at least in the Neogene, Darwin's ‘Age of Barnacles’.
Magmatic evolution of the Løkken SSZ Ophiolite, Norwegian Caledonides: Relationships between anomalous lavas and high‐level intrusions
Authors: Grenne Tor 
Published: July 2010

AbstractThe Lower Ordovician Løkken ophiolite fragment shows a tripartite subdivision of its thick volcanic sequence into: (1) an Upper Volcanic Member (UVM) of transitional MORB/IAT character, comprising basalts or, in a related, thrust‐bounded sequence, a bimodal basalt‐rhyolite assemblage; (2) a Middle Volcanic Member (MVM) derived from widely variable, generally MORB‐related magmas; and (3) a Lower Volcanic Member (LVM) of N‐type MORB basalts which locally passes into an underlying sheeted dyke complex. The UVM and LVM were fed from relatively deep‐seated magma chambers, and lavas were erupted at moderate flow rates to form predominantly pillow lavas. The whole sequence is interpreted as having formed in a marginal basin setting.The MVM is characterized by abundant voluminous sheet basalts thought to have been erupted at high flow rates. The volcanites had their source, through extensive dyke swarms, in high‐level magmas which intruded the sheeted dyke complex and parts of the LVM, possibly in a near‐axial seamount setting. The magmas differentiated to form plagiogranitic melts, with a wide range of conjunctive, mafic to intermediate cumulates. This plutonic assemblage, possibly in crystal mush form, was subsequently intruded by new, mafic magma, leading partly to large‐scale remelting or assimilation of cumulus phases. These processes are reflected in the MVM by common hybrid flows, as well as local intermediate lavas having the geochemical characteristics of cumulates, erupted during a period of intense faulting. Major tapping of the primary, mafic magma occurred toward the end of the period of MVM volcanism. A predominance of voluminous, apparently fluid, massive flows in the MVM is mainly ascribed to the shallow depth of magma reservoirs.