bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relationship between light hydrocarbons and carbonate petrology—a study from the Mendip Hills
Authors: Goodman S. 
Published: February 2007

AbstractAnomalously high values of light hydrocarbons (C1–C4) have been detected in carbonate rocks hosting base metal mineralization, and have a potential use in mineral exploration. Development of an exploration method based on such anomalies requires an understanding of the controls on the hydrocarbon content of the rocks, other than by mineralization, i.e. the hydrocarbons present in background areas. This study uses gas chromatography to investigate the light hydrocarbons present in rocks from such a background area, the Carboniferous Limestone of the Mendip Hills, in order to determine the extent to which different carbonate lithologies affect the quantity and nature of hydrocarbons present. It appears that the lithological effects are minimal when compared to the anomalous values from mineralized areas. The limited effects are due to variations in the depositional and diagenetic regimes of the original sediments.
Sediment dynamics of early Carboniferous ramps: A proposal
Authors: Wright V. P. , Faulkner T. J. 
Published: February 2007

AbstractIn this paper we contend that the widespread development of carbonate ramps, in preference to carbonate shelves, during the early Carboniferous was a consequence of the different style of carbonate production during that period. Not only was the overall rate of biogenic production probably slightly lower than at most other times in the Phanerozoic but its distribution was also different. The marked differential carbonate productivities between shallow and deeper water, a key factor in forming accretionary shelf margins, was not as strongly developed during the early Carboniferous. Benthic biotas, especially reef builders, were partly impoverished following the late Devonian extinctions and were also affected by oceanographic and climatic changes taking place during the Tournaisian, including possible anoxic phases.
Controls on alluvial architecture by synsedimentary faults in the Coal Measures of South Wales
Authors: Hartley Adrian , Gillespie Paul 
Published: February 2007

AbstractA series of small‐scale gravity induced synsedimentary faults are described from the Middle Coal Measures (Westphalian B) of the South Wales Coalfield. The synsedimentary nature of the faults is indicated by abrupt changes in sediment thickness across faults, eroded fault scarps and the restriction of faulting to 8·75 m of sediment bounded by laterally persistent black shales above and a seatearth below. Evidence for the non‐tectonic origin of the faults is given by the presence of passive footwalls.Channel sandstone bodies occurring within the hanging walls of individual faults were deposited by discrete overbank flood events. Drainage patterns during flood events were controlled by topographic lows adjacent to the faults such that palaeocurrent data within the channel sandstone bodies indicate a S/SW transport direction parallel to fault strike.Synsedimentary fault movements resulted in the diagonal stacking of successively younger sandstone bodies adjacent to the faults, and an increase in tilt of the bodies with depth from 0 → 26°. The architecture of channel sandstone bodies was controlled by (1) the amount of fault movement and (2) fault block dimensions (or fault spacing). The interaction of these controlling factors resulted in deposition of symmetrical channel sandstone bodies over narrow fault blocks (12 m wide) with large fault displacements (7 m), asymmetrical sandstone bodies over wide fault blocks (30 m) with large fault displacement (7.5 m), and limited channel sandstone body development over fault blocks with small fault displacements (1.5 m).Synsedimentary faulting is thought to have been initiated by either seismic shock and/or overpressuring of pore fluids within buried mudstones.
Granite magmatism and extensional tectonics in Southern Greenland
Authors: Harrison T. N. , Brown P. E. , Dempster T. J. , Hutton D. H. W. , Becker S. M. 
Published: February 2007

AbstractThe southernmost part of the early Proterozoic Ketilidian mobile belt (1·9–1·7 Ga) of southern Greenland comprises a thick series of largely flat‐lying migmatitic metasediments and metavolcanics of upper amphibolite to lower granulite facies. Regional tectonics are extensional and there is little structural evidence for earlier crustal thickening. Several episodes of granite magmatism are recorded, culminating in the late‐ to post‐orogenic rapakivi granites, which are associated with with a coeval suite of norites. These were emplaced at ca. 1740 Ma, roughly synchronously with the peak of regional metamorphism (2–3·5 kbar, 650–800°C). The rapakivi granites have been emplaced into major crustal‐scale extensional shear zones and have ramp‐flat geometries. ‘Black’ and ‘white’ rapakivi granites are found. The mineralogy of the black granites is dominated by orthopyroxene–amphibole assemblages with rare fayalite. In the white granites, biotite and amphibole are the only Fe–Mg silicates. All Fe–Mg silicates have high Fe/(Fe+Mg) ratios. In terms of bulk chemistry, the suite is bimodal. Both norites and granites are strongly fractionated and have Fe/(Fe+Mg) ratios of 0·50–0·65 (norites) and 0·65–0·90 (granites). REE modelling shows that the granites can be derived from 40 per cent partial melting of a metasedimentary protolith. The sequence of magmatic events in this region reflects the progressive metamorphism and dehydration melting of juvenile sediments in an extending basin. The heat source for melting may have come from the underplating of olivine tholeiite melts generated during lithospheric extension.
Acid magmatism and related metallogenesis in the Erzgebirge
Authors: Tischendorf G. , Förster H.‐J. 
Published: February 2007

AbstractIn the Erzgebirge two post‐collisional Hercynian granitoid complexes are developed: an older one, monzogranitic, moderately specialized, Sri = 0·7064–68, εTNd = ‐1·8 to ‐6·2, 1g fO2 < −13 ± 1, 1g fHF/fH2O = ‐3·9 ± 0·2, S‐type, 340–325 Ma in age, and a younger one, monzo‐ to albitegranitic, highly specialized in Li, Rb, Cs, Sn, and W, Sri disturbed by strong autometasomatic influences, εTNd = −3·8 to −6·0, 1g fO2 < −17 ± 1, 1g fHF/fH2O = ‐3 ± 0·3, I‐type, 310–295 Ma. Postplutonic volcanics (rhyolite, rhyodacite, latite, kersantite–minette) in each case complete the magmatic sequences.Muscovite–wolframite–molybdenite–pyrite–quartz association is locally related to the older complex, but numerous centres of cassiterite–wolframite–zinnwaldite (or muscovite) deposits are related to the younger one. Both mineralizations are of orthomagmatic origin and underwent strong physicochemical control. Thus, the granites genetically related to the tin‐free older association are conditioned by medium fO2 but low fHF/fH2O, the tin‐bearing younger association, in contrast, is controlled by low fO2 coupled with high fHF/fH2O.Vertical compositional zonation in magma chambers caused enrichment of compatible elements such as Zn, Pb, Mg, Ca, Ba, Sr, in deeper parts of the chamber and their transition into residual solutions which then may form base metal mineralization as cross‐cutting veins. Mineralization events last up to the Triassic. Probably elements in the later stages were derived either from deep‐originated residual solutions or, increasingly, by leaching of specialized magmatites.
Site selectivity of a lower carboniferous boring organism infesting a crinoid
Authors: Donovan Stephen K. 
Published: February 2007

AbstractThe position of a boring in a cup of the disparid crinoid Synbathocrinus conicus Phillips from Clitheroe, England, suggests various inferences concerning the ecology of the pit‐forming organism. The crinoid cup shows a growth deformity, indicating it must have been alive when infested. The boring is at a triple suture between the E and A ray radials and the EA interray basal, presumably one of five equally weak points on the cup. This site is well removed from the anus and would have been an ideal point of attachment for a filter feeding organism, being well elevated, upcurrent and protected.
Regional sedimentological variations in lower triassic fluvial conglomerates (budleigh salterton pebble beds), southwest england: Some implications for palaeogeography and basin evolution
Authors: Smith Simon A. , Edwards Richard A. 
Published: February 2007

AbstractThe Budleigh Salterton Pebble Beds (BSPD) are a 20–30 m thick formation of conglomerates and subordinate sandstones which crop out along the western margin of the Wessex Basin. The formation has previously been interpreted as representing a major conduit for southerly‐derived (Armorican) detritus and as signalling the start of early Triassic rifting. In this paper the role of the BSPB in the evolution of the Wessex Basin is reassessed.In the south of the outcrop, the lower portions of the BSPB are dominated by extensive (> 50m) sheets or narrow lenses of planar cross‐bedded conglomerate (sets 1–3m thick). This reflects deposition from linguoid‐shaped bars whose downstream margins were bounded by slipfaces. These accreted at anabranch confluences and as bank‐attached bars in relatively confined and channelized gravel‐bed streams. Most of the rest of the BSPB consists of couplets of horizontally‐bedded conglomerate overlain by large‐scale trough cross‐bedded sandstone. This style of accretion represents deposition from relatively low‐relief gravel bars and large sand dunes in substantial but poorly confined channels. Towards the top of the BSPB in the central parts of the outcrop, there is a change to thinner‐bedded units with more lenticular and ribbon‐like geometries. This represents deposition in smaller and more flashy streams.The BSPB was deposited either on a braidplain or by an antecedent ‘wet’ alluvial fan. In both settings, the BSPB streams were exotic, draining basins to the south of the Wessex Basin. This implies that the BSPB did not necessarily develop in response to differential subsidence and rifting within the Wessex Basin.
Allocycles in the upper part of the limestone coal group (pendleian, E1) of the glasgow‐stirling region viewed in the light of sequence stratigraphy
Authors: Read W. A. , Forsyth I. H. 
Published: February 2007

AbstractSequence stratigraphy has produced a number of new concepts and terms which have been described and defined in the Wilgus et al. (1988) volume. Many of these concepts and terms can be applied to the two orders of allocycles present in the non‐autocyclic parts of the Limestone Coal Group. The longer‐period allocycles responsible for major Namurian marine transgressions correspond in their duration to ‘sequences’. The shorter‐period allocycles of the distal facies association in the upper part of the Limestone Coal Group correspond in their duration to ‘parasequences’. However, they include deeply incised fluvial channels similar to those cut into shelf sediments at ‘Type 1 sequence boundaries’, and are best regarded as unusually short‐period depositional sequences. The deep fluvial channels, which relate to lowstands, were incised when the rate of fall in sea level (probably glacial‐eustatic) exceeded the local rate of tectonic subsidence.The bulk of the distal facies association belongs to the ‘highstand systems tracts’ and ‘transgressive systems tracts’ of sequence stratigraphy. Lowstand deposits are poorly represented. Erosional breaks within two‐storey sheet sandstones probably reflect scouring by fluvial channels in the prograding ‘highstand systems tracts’ during the early stages of eustatic falls. Coals mostly relate to the rising water table conditions associated with ‘transgressive systems tracts’ and each seam may be preceded by a depositional hiatus. Extensive penecontemporaneous lowstand deposits may be found in the turbidite‐fronted deltas of the Pennine Millstone Grit.
Pleistocene gravels in the lower wye valley
Authors: Hey R. W. 
Published: February 2007

AbstractThe fluviatile Pleistocene of the lower Wye valley, below the Devensian glacial limit near Hereford, consists almost entirely of coarse gravels, situated both above and below the level of the modern flooplain. Those above the floodplain are largely composed of pebbles from the Ordovician and Silurian of east‐central Wales. Around Hereford they are associated with well‐preserved terraces; further downstream they are fragmentary and have also undergone some displacement. It is suggested that the high‐level gravels comprise remants of four distinct aggradational units. Correlations are proposed with the Severn valley Pleistocene sequence, from which it is concluded that the lower Wye gravels represent a series of cold, perhaps glacial, periods ranging in age from pre‐Hoxnian to Devension. This confirms the pre‐Hoxnian age of fragmentary glacial deposits in northeast Herefordshire. Relations between the gravels and some geomorphological features are discussed, with special attention to abandoned incised meanders.
A revision of the stratigraphy of the longmyndian supergroup, welsh borderland, and of its relationship to the uriconian volcanic complex
Authors: Pauley John C. 
Published: February 2007

AbstractMajor revisions are proposed to the stratigraphy of the late Precambrian Longmyndian Supergroup of the Welsh Borderland. The stratigraphic relationship between it and the adjacent, late Precambrian Uriconian volcanic complex is reviewed and reinterpreted. Contrary to previous belief it is proposed that the Wentnor Group of the Longmyndian Supergroup does not overlie the Stretton Group unconformably. An apparent unconformity is interpreted as the result of post‐Longmyndian tectonism. The Ragleth Tuff Formation, previously included with the Uriconian volcanic complex, is argued to be part of the Longmyndian Supergroup. The Helmeth Grit Member, previously thought to be the base of the Longmyndian Supergroup, is incorporated within the Ragleth Tuff Formation. These modifications necessitate a revision of the previously held belief that the Helmeth Grit Member is the base of the Longmyndian Supergroup which overlies the ‘Ragleth Tuffs’ of the Uriconian volcanic complex unconformably. The Ragleth Tuff Formation and the Stretton Shale Formation are thought to be faulted against the Eastern Uriconian, and the Wentnor Group is thought to be faulted against the Western Uriconian. Juxtaposition of the Longmyndian Supergroup with the Uriconian volcanic complex across faults is the result of strike‐slip movements along the Church Stretton and Pontesford‐Linley fault systems. Lithological and petrographical evidence suggests that the Longmyndian Supergroup is partly coeval with, and partly younger than, the Uriconian volcanic complex, which acted as a source. The Willstone Hill conglomerate, previously thought to be interbedded with the Eastern Uriconian, may be a representative of the Wentnor Group which overlies the Eastern Uriconian unconformably. As such, it may represent a late onlap of Longmyndian sediments onto the Eastern Uriconian at the margins of the Longmyndian basin. A new formation, the Linley Formation, is recognized. This occurs as fault‐bounded slivers and lenses within the Pontesford‐Linley fault system, and correlation with the rest of the Longmyndian is uncertain.
Trilobite trace fossils and their stratigraphical significance in the Cambrian sequence of the Holy Cross Mountains, Poland
Authors: Orłowski Stanisław 
Published: February 2007

AbstractAbundant and varied trilobite trace fossils are recognized and described in the Cambrian sequence of the Holy Cross Mountains.CruzianaandRusophycusare stratigraphically significant and some of the described traces may be used as local index fossils. The first recognition of theCruziana barbataichnozone in Poland is made and it occurs in the uppermost Middle Cambrian. A new position for the Middle/Upper Cambrian boundary is established. Three new ichnospecies are described:Cruziana magna, C. regularisandRusophycus crebus.
Palaeomagnetic, geochronological and geological constraints on the tectonic evolution of the Mejillones Peninsula, northern Chile
Authors: Hartley Adrian J. , Turner Peter , Rex David C. , Flint Stephen 
Published: February 2007

AbstractPalaeomagnetic and geochronological data from an Early Palaeozoic high grade metamorphic complex (Jorgina Formation) and Jurassic layered basic intrusion (Moreno Complex) are reported from the Mejillones Peninsula of northern Chile (23–23°30'S). 40Ar–39Ar dates from the Lower Palaeozoic Jorgina Formation and the Moreno Complex are between 170 and 158 Ma, coincident with a phase of emplacement of the north Chilean coastal batholith. This suggests that intrusion and magnetization of the Moreno Complex and the metamorphism and remagnetization of the Jorgina Formation were related to batholith emplacement. Extracted stable components of magnetization from all units (17 sites) define site‐mean directions with a scattered distribution. The scatter in site‐mean directions is interpreted as being due to minor, localized, non‐uniform, block‐fault related (normal or strike‐slip, or both) rotation after 158 Ma. The palaeomagnetic and geochronological data indicate that no significant large‐scale latitudinal translation of crustal blocks has taken place in this part of northern Chile since the Late Jurassic. In addition, they indicate that the uniform clockwise rotation after the mid‐Cretaceous which affected the adjacent Cordillera de la Costa either did not extend into the Mejillones Peninsula or took the form of localized block‐fault rotations. The restriction of palaeomagnetically defined styles of rotation to discrete areas within the north Chilean forearc indicates that forearc wide block‐fault rotation models are not applicable to the Pacific margin of northern Chile.
Late Caledonian sinistral strike‐slip displacement across the Leannan Fault system, northwest Ireland
Authors: Alsop G. I. 
Published: February 2007

AbstractThe Leannan Fault of north‐west Ireland is a sinistral strike‐slip fault system which juxtaposes Dalradian metasediments of differing structural trends and metamorphic grades. It probably represents a south‐west splay of the Great Glen Fault of Scotland. The recognition and tracing of the Foyle Synform across the fault zone, together with the correlation of regional Dalradian strike swings, lateral sedimentary facies variation and metamorphic grades, suggest a sinistral displacement of 34 km across the fault. Members of the Leannan Fault system displace a Lower Devonian (about 397 Ma) granite, but are overlain by Viséan (about 352 Ma) sandstones, thus constraining major late Caledonian sinistral motions to the Middle to Upper Devonian.
Early to mid‐Viséan shallow water platform buildups, north Co. Dublin, Ireland
Authors: Somerville Ian D. , Pickard Neil A. H. , Strogen Peter , Jones Garethli 
Published: February 2007

AbstractA number of carbonate buildups in north Co. Dublin, long assigned to the late Viséan (Asbian), are shown on the basis of coral, foraminiferal and algal evidence to be early to mid‐Viséan (late Chadian to Holkerian) in age. They are equivalent in age to beds ranging from the upper part of the Lane Formation to the top of the Holmpatrick Formation.The buildups are poorly exposed and relatively small, probably only a few tens of metres across at most. Buildup sediments are massive to crudely bedded and dominated by peloidal, clotted and dense uniform micrites displaying lime mudstone and bioclastic wackestone textures. Dasycladacean algae are common in the buildups and cryptalgal fabrics are locally important. Cavities in the buildups are generally small (< 5 cm) and lined with inclusion‐rich radiaxial calcite cements. Micritization of bioclasts and cements is ubiquitous. Enclosing off‐buildup limestones are skeletal and intraclastic grainstones possessing sedimentary structures indicative of deposition in moderate to high energy environments. Fossil and petrographic evidence from the buildups also indicate a shallow water origin for the north Co. Dublin buildups.Compared with the slightly older Tournaisian (Courceyan to early Chadian) Waulsortian buildups which developed extensively in the Dublin Basin, these younger platform buildups are smaller and more isolated and possess a diverse suite of algal components and cryptalgal fabrics. Nevertheless, components in the north Co. Dublin buildups most closely resemble the shallowest phase D Waulsortian buildups, particularly in the presence of abundant peloids and micritized cements.The north Co. Dublin buildups developed on a carbonate platform (the Milverton Platform), adjacent to the Dublin Basin, whereas the Waulsortian developed in a deeper ramp setting. Following the demise of the Waulsortian in early Chadian time carbonate buildups established themselves on the shallow platforms. It is suggested that the microbial communities responsible for these buildups may have ‘evolved’ from older phase D Waulsortian communities and that he north Co. Dublin platform buildups represent the shallow water end of a spectrum of Viséan buildups.
Sedimentology and early diagenesis of the Broadford Beds (Lower Jurassic), Skye, north‐west Scotland
Authors: Searl Alison 
Published: February 2007

AbstractThe Broadford Beds comprise a basal carbonate‐dominated unit overlain by dark muddy sandstones and an upper cross‐bedded sandstone unit. The limestones include coralliferous and oolitic lithologies and the sandstones include pisolitic berthierine ironstones and abundant phosphate nodules. The Broadford Beds have a maximum thickness of 140 m and can be subdivided into 17 parasequences, each initiated by an approximately 20 m rise in relative sea level. Marine flooding surfaces are most readily recognized in the lower parts of the succession, where diagenetic data can be utilized to locate emergence surfaces. There is no diagenetic evidence of early emergence in the upper parts of the sequence, but a variety of sedimentological data can be used to identify parasequence boundaries. Deposition of the Broadford Beds occurred largely around the shores of a number of islands in the northern Hebridean area. These islands partly isolated the Skye–Applecross area from a deeper marine basin to the west, and this may have enhanced the formation of authigenic phosphates and iron silicates. It is possible to use the regional variability of parasequence thicknesses to investigate the role of active local tectonism in governing differential subsidence and sediment supply.
Progressive deformation and the rotation of contemporary fold axes in the Ballybofey Nappe, north‐west Ireland
Authors: Alsop G. I. 
Published: February 2007

AbstractInternal regions of orogenic belts may be characterized by an alignment of fold axes with mineral elongation lineations. This relationship is commonly interpreted as representing progressive tightening and rotation towards the shear direction of early buckle folds, the hinges of which were initiated orthogonal to this direction. Detailed structural analysis of lower amphibolite facies Dalradian metasediments of the Ballybofey (fold) Nappe, north‐west Ireland, shows that an intense S3 schistosity is developed axial planar to mesoscopic and minor F3 folds. In areas of low D3 strain, F3 fold axes plunge gently towards the north‐east, whereas in regions of greater strain plunges are towards the south‐east subparallel to the constant mineral lineation. Minor folds which initiated at angles of 70–80° from the mineral lineation subsequently rotated towards the shear direction in a consistent clockwise sense. Progressive and variable non‐coaxial deformation oblique to the original mean F3 orientation has resulted in a unimodal distribution pattern of fold axes. Analysis of the angular rotation of fold axes enables estimates of the bulk shear strain to be evaluated and models of progressive deformation to be assessed.