bluuebunny/crossref_metadata_2025_split huggingface dataset:
The postcranial skeleton of the Middle Devonian lungfishDipterus valenciennesi
Authors: Ahlberg Per Erik , Trewin Nigel H. 
Published: November 2011

AbstractThe axial skeleton and fin supports of the Middle Devonian lungfishDipterusare described from a range of specimens from the Orcadian Basin of Scotland. The axial skeleton of the trunk region consists of intercentra, relatively short ribs, and neural arches bearing two rows of supraneural spines; posteriorly, the intercentra are replaced by haemal arches. The notochord seems to have been essentially unconstricted. There may have been two pairs of cranial ribs. In general terms the vertebral column resembles that ofNeoceratodusbut is more fully ossified. The only known paired fin support ofDipterusis an archipterygial structure resembling those ofNeoceratodus, with at least seven mesomeres and jointed pre- and postaxial radials. The pectoral fin is rotated as in modern lungfishes. The median fin supports all consist of basal plates supporting radials. In the posterior dorsal fin support the posterior radials form a branched structure. The heterocercal tail is supported by segmental radials. A new body reconstruction is presented.The characters possessed byDipterusoffer support for a lungfish–porolepiform sistergroup relationship. All known lungfishes fit into a single cumulative series of postcranial morphologies. The evidence for a paedomorphic trend in lungfish phylogeny is interesting but inconclusive.
Conodont Colour Alteration Index (CAI) values for the Carboniferous of Scotland
Authors: Dean Mark T. , Turner Nicholas 
Published: November 2011

AbstractConodont elements from Scottish Carboniferous rocks have been reviewed for Colour Alteration Index(CAI) data, and most values range between 1 and 1·5. Assuming a local average geothermal gradient similar to that of today, the observed and predicted CAI values generally fit well. Only a few of the samples analysed were influenced by local igneous intrusives. The CAI range shown lies within the immature (early dry gas) to mature (perhapsmid-oil window) stages of hydrocarbon generation, and this suggests that burial maturation (where CAI values are 1-5) could account for locally generated oil, where this occurred away from igneous intrusions. Alkali-dolerite and tholeiitic intrusives are, however, widespread in the Midland Valley of Scotland, and an understanding of their thermal effects has implications for both coal and petroleum exploration. The insensitivity of conodonts to low temperatures is noted, and the relevance, application and potential of various other palaeothermometers is discussed. Locally, the qualitative study of spore colour (SCI) appears useful.
Ontogeny of the Carboniferous trilobitePaladin eichwaldi shunnerensis(King 1914)
Authors: Clarkson Euan N. K. , Xi-guang Zhang 
Published: November 2011

ABSTRACTThe Carboniferous trilobitePaladin eichwaldi shunnerensis(King 1914), at its type locality in northern England is exceptionally well-preserved, and shows all stages of growth from the degree 0 meraspis onwards. The post-protaspid ontogenyis described here with particular reference to the development of cuticular sculpture. On the dorsal surface of the smallest specimens a polygonal network of raised ridges (cell polygons) is apparent. With size increase, granules progressively appear amongst the polygons, which in turn change into large tubercles as the polygonal network fades. As the trilobite grows into an adult, the tubercles become relatively smaller, and pits, the openings of cuticular canals, appear amongst them. Marginal terrace lines become pronounced. On the hypostome, however, terrace lines become effaced centrally, while large pits develop. In the early meraspis the eyes are “schizochroal”, but the lenses rapidly become closely packed and contiguous and the eye is soon of “holochroal” type. The meraspid phase is passed through very rapidly. Whereas the earlymeraspis could not enroll, its pygidium could be bent down vertically, and this facility might have allowed the larva an escape reaction.
Biostratigraphy of late Llandovery (Telychian) and Wenlock turbiditic sequences in the SW Southern Uplands, Scotland
Authors: White Dennis E. , Barron Hugh F. , Barnes Robert P. , Lintern Byron C. 
Published: November 2011

ABSTRACTIn the SW part of the Southern Uplands of Scotland the relatively thin Moffat Shale Group (late Ordovician–early Silurian) is succeeded by a thick development of Silurian greywackes, of variable turbiditic facies. This includes late Llandovery (Telychian) quartzose greywackes with interbedded thin graptolitic shales of theturriculatusandcrispusbiozones, in the upper part of the Gala Group, a sequencewhich is laterally equivalent to the basal part of the Hawick Group. The age of the finer-grained calcareous Hawick Group, which here includes 1. the Ross Formation, ranges from late Llandovery (turriculatusBiozone) to early Wenlock (riccartonensisBiozone). The Riccarton Group, which contains thick units of thinly-bedded siltstones and mudstones, is of Wenlock age (riccartonensistolundgrenibiozones). Within this sequence, all the biozones of the standard graptolite zonal scheme have been recognised in the area, with the exception of thecrenulataBiozone of the late Llandovery (Telychian Stage) and themurchisoniandellesaebiozones of the Wenlock (Sheinwoodian Stage). Details of the graptolite biostratigraphy areclosely comparable with those of the markedly thinner sequences of northern England. Acritarchs occur throughout the sequence but are most numerous and best preserved in the Gala Group. Poorly preserved chitinozoa and spores are also present, the former occurring sporadically throughout the succession but the latter become common only in the Riccarton Group.
The first zosterophyll from the Lower Devonian Rhynie Chert, Aberdeenshire
Authors: Lyon A. G. , Edwards Dianne 
Published: November 2011

ABSTRACTFragmentary remains of a vascular sporophyte from the Rhynie Chert are described as a new genus and species, Trichopherophyton teuchansii. The plant, which is characterised by the possession of unicellular spinous hairs, exarch xylem and laterally attached, marginally dehiscent sporangia, is assigned to the Zosterophyllophytina, but lack of information on the arrangement of sporangia prevents its more precise positioning within the subdivision. Unusual features include the combination of circinate tips to axes with almost terete xylem strands, and the lack of a thick-walled outer cortical zone. Associated axes, lacking spinous hairs, but having papillate or rhizoid-like epidermal emergences, are interpreted as likely rhizomes of Trichopherophyton. Features, such as unicellular spinous hairs, rhizoid-like emergences, circinate tipsand parenchymatous cortex are considered in relation to the functioning and growth of aplant inhabiting an early Devonian wetland.
Revision and subdivision of the polyphyletic ‘Leonaspis’ (Trilobita)
Authors: Ramsköld Lars , Chatterton Brian D. E. 
Published: November 2011

ABSTRACTA phylogenetic analysis is performed on all species previously assigned to the odontopleurid trilobite genusLeonaspis. The PAUP analysis shows this genus, as conventionally defined, to be polyphyletic, composed of four groups of equal taxonomie rank.Leonaspis(s.s.) is here restricted to one of these groups only, a monophyletic set of species characterised by ‘four-spined’ pygidia (i.e. with four spines between the major border spines) and a thorax of nine segments.Kettneraspisis recognised for the largest of these four groups, and is composed of ‘two-spined’ species with nine thoracic segments.LeonaspisandKettneraspisbelong to the Odontopleurinae. A third group of previous ‘Leonaspis’ species constitute a new genus of the Acidaspidinae. Its species are characterised by being ‘four-spined’ and having ten thoracic segments. For these the new genusExallaspisis erected, with type speciesE. bufo. A fourth group of ‘Leonaspis’ species, being ‘four-spined’ with nine thoracic segments, belongs toEoleonaspis, an Ordovician odontopleurine genus.LeonaspisandExallaspisare temporally and spatially non-overlapping,Leonaspisbeing exclusively Gondwanan post-Wenlock, whereasExallaspisis restricted to areas north of the Rheic Ocean and ranges from basal Llandovery to Ludlow.Kettneraspisis pandemic. The condition of five epiborder spines and ten border spines on the free cheek is proposed as plesiomorphic for odontopleurids, and the border spines are shown to originate as two separate rows with alternating spines. A shift in position of the facial suture is shown to transfer the genal spine from the cranidium to the free cheek inKettneraspismeraspides of degree 1 or 2, and the previously suggested co-occurrence of a fixigenal and librigenal spine in these stages is refuted. Earlier proposed dimorphism is rejected, and two mechanisms for reduction in the number of pygidial border spines are proposed.Kettneraspis reetaesp. nov. is described.
Evolution of Ordovician terranes in western Ireland and their possible Scottish equivalents
Authors: Williams D. M. 
Published: November 2011

ABSTRACTIn the W of Ireland the Ordovician rocks of South Mayo and Clew Bay are now juxtaposed but a comparison of the sedimentary histories of these two sequences shows that they accumulated in basins which were probably separated during most of their history. The large amount of terrigenous detritus present in the Arenig to Llanvirn elements of the South Mayo succession is not manifest in that of Clew Bay until the Llandeilo/Caradoc, by which time sedimentation in South Mayo had ceased. A comparison of the South Mayo Ordovician with that of Girvan in Scotland demonstrates that both sequences had a similar provenance. This source contained an ophiolite, granites and some (probably pre-Dalradian) metamorphic rocks. Sediment dispersal directions for the two sequences are opposite in sense, being primarily northward in South Mayo and southward at Girvan. The two stratigraphies indicate that basement subsidence behaviour in South Mayo was virtually the opposite of that at Girvan where initial shallow water sedimentation was rapidly succeeded by deep water environments at the end of the Llanvirn. The two basins may thus have been marginal to a single Ordovician arc complex. One reason for the opposite sense of basin subsidence may lie in the suggested reversal of subduction polarity during the Ordovician. In this scenario the South Mayo basin may be envisaged as lying to the N of a northward-facing arc during the early Ordovician. A new, northward, subduction direction instigated during the Llanvirn, resulted in a fore-arc basin at Girvan complemented by a closing back-arc basin in South Mayo.
The structure and petrogenesis of the Trallval and Ruinsival areas of the Rhum ultrabasic complex
Authors: Volker J. A. , Upton B. G. J. 
Published: November 2011

ABSTRACTDetailed mapping of the Trallval-Ruinsival area of the ultrabasic complex of Rhum has revealed the relationship between the intrusive peridotites, which form a major part of the complex, and the layered ultrabasic rocks. The layered rocks on Trallval are correlated with Units 8 to 15 of the Eastern Layered Series as seen on Hallival and Askival, and part of an additional unit, Unit 16, has also been identified. The layered rocks of Ruinsival and the western part of Trallval form part of the Central Series and have been subdivided into six cyclic units. They are associated with four sets of intrusive breccia zones which converge towards a central region. Four cylindrical plugs of intrusive peridotite occur within the area of outcrop of the Central Series. Criteria are listed for the distinction of intrusive peridotite from conformable peridotites formed in situ. Distinctive textures and structures are described; these include vertical feldspathic streamers, which are interpreted as direct evidence for the upward expulsion of interstitial fluid, and loading structures at the contact between a peridotite layer and underlying allivalite are ascribed to the intrusion of a peridotite sill. A comparison of the Eastern Layered Series and the Central Series suggests that three stages were involved in the formation of the ultrabasic rocks: (i) the accretion of rhythmically layered unconsolidated olivine cumulates; (ii) the upward expulsion of intercumulus liquid; and (iii) the formation of either allivalite (as in the Eastern Layered Series) or ultrabasic breccia zones (as in the Central Series) from the expelled intercumulus liquid, depending on whether the tectonic environment was quiescent or extensional.
Glacial and volcanic geomorphology of the Chimborazo-Carihuairazo Massif, Ecuadorian Andes
Authors: Clapperton Chalmers M. 
Published: November 2011

ABSTRACTThe Chimborazo (6,310 m)–Carihuairazo (5,102 m) massif is one of the largest ice-capped central volcanic complexes in the northern Andes. Combined evidence from volcanic and glacial landforms and sediments suggests cyclical evolution during the Pleistocene. Effusive eruptions of mixed high-silica andesite (SiO2%wt c. 60) predominated and built the bulk of the edifice. Explosive activity developed as the parental magma evolved to dacite-rhyolite (SiO2%wt 64–74), culminating with cone collapse and large-scale debris avalanching. Post-collapse activity evolved from the production of high-silica andesite to terminate with monogenetic eruptions of basic andesite (SiO2%wt 54–56) from flank fissures. The last eruption occurred before 11,000 yBP.The interstratification of volcanic and glacial deposits shows that glaciers expanded and contracted several times during the later Pleistocene, while the volcanic edifices were evolving. Glaciers expanded to altitudinal limits of 3,400–3,600 m during the early last glaciation and reached similar limits sometime after 33,000 yBP; an intervening interstadial interval lasted for 10,000 y. By 20,000–18,000 yBP, glaciers receded slightly because of decreased precipitation, but later readvances culiminated at 12,000–10,000 yBP and during the last 5,000 y. Glacier reconstruction and estimation of former equilibrium line altitudes suggest that the mean annual temperatures during the full glacial, late-glacial and Neoglaciation intervals were lower than now by c. 5–6°C, 2–3°C and 1°C, respectively, but these may be underestimates because of the assumption that precipitation was constant.
Wenlock (Silurian) graptolites, Cape Phillips Formation, Canadian Arctic Islands
Authors: Lenz A. C. , Melchin M. J. 
Published: November 2011

Twenty six of the more important species of monograptids (s.l.), retiolitids andCyrtograptus(from a total fauna of 52 species) are described from Wenlock strata of the Cape Phillips Formation, Canadian Arctic Archipelago. Of this fauna, eight new species or subspecies,Monograptus firmus festinolatus, M. instrenuus, M. opimus, M. testis incomptus, Cyrtograptus falcatus, C. hamatus brevis, C. kolobusandC. pseudomancki, are described and illustrated.Wenlock biostratigraphic zones comprise theCyrtograptus centrifugus-C. insectusZone (earliest Wenlock),M. instrenuus-C. kolobusZone, tentatively divisible into lower and upper subzones,C. perneri-M. opimusZone possibly divisible into lower and upper subzones, C.lundgreni-M. testisZone divisible into a lowerM. testis incomptusSubzone and an upperM. testis testisSubzone, and thePristiograptus ludensisZone (latest Wenlock).
Black sandstones in the Midland Valley of Scotland: thermally metamorphosed hydrocarbon reservoirs?
Authors: George Simon C. 
Published: November 2011

ABSTRACTCarboniferous sandstones from within the thermal aureoles of igneous intrusions in the Midland Valley of Scotland sometimes have a strong, black colour and are termed ‘black sandstones’. Tait (1926) concluded that the black sandstones are the products of the thermal metamorphism of petroliferous sandstones, a theory which is discussed here in the light of modern petrological and geochemical techniques.The black colour of the sandstones is due to an amorphous, opaque bitumen which usually coats illitic clays, fills porosity and was mostly emplaced at a fairly late diagenetic stage. This solid bitumen has a low reflectance (c. 0·15% R0), no fluorescence under blue-light excitation, is insoluble in organic solvents, is isotopically heavy and has a very low H/C atomic ratio. These data, together with the field relationships of the black sandstones and igneous intrusions, suggest that the bitumen was formed by the thermal alteration of hydrocarbons, as described by Tait (1926), rather than by other possible mechanisms such as the deasphalting of an oil, or the generation of hydrocarbons from organic-rich rocks heated by igneous intrusions, followed by fractionation during migration. This conclusion suggests that by the time of emplacement of the quartz-dolerite intrusions, and some of the alkali-dolerite sills, there had been widespread generation and migration of hydrocarbons which possibly could have been preserved to the present day where not thermally altered.
The ratio of mechanical to chemical denudation in alluvial systems, derived from geochemical mass balance
Authors: Stewart A. D. 
Published: November 2011

ABSTRACTMass balance equations are derived which link the ratiosTs/(suspended load/dissolved load from chemical weathering) andTb/Ts(bed load/suspended load), with any two geochemical components present in the source rock and the alluvial system. If the dissolved load is unknown the ratios can be estimated from the relatively insoluble silica and alumina. The ratioTs/, which for large river basins depends on climate and relief, can thus potentially be determined from ancient alluvial sequences.The equations help define the source composition of a group of 13 modern rivers for whichTs,and alluvial geochemistry are known. These rivers together drain 27% of the continental surface. For a source area with the average continental sandstone to shale ratio of 0·6 the observed average value ofTs/is obtained when limestone, sandstone and shale are present in the proportions 6·7:21·6:35·7. The figure of 64% sediment in the source area is very similar to the 66% determined by Blatt and Jones (1975) from geological maps of the continents. The equations also show that average bed load transport rate into these 13 basins is about 27% of total transport, and into the Amazon basin about 37%. Bed load transport rates out of the basins, into the sea, are relatively very small.
The geological setting of the southern Bathgate Hills, West Lothian, Scotland
Authors: Smith R. A. , Stephenson D. , Monro S. K. 
Published: November 2011

ABSTRACTThe southern Bathgate Hills, in the eastern part of the Midland Valley basin of Scotland, were the site of a volcanic rise during late Dinantian to early Silesian times and a sequence of basaltic lavas and tuffs up to 600 m thick accumulated. The volcanic pile interrupted the regional sedimentary deposition, which involved a cyclical sequence of marine limestones and mudstones followed by estuarine, lagoonal and deltaic clastic deposits. During the Brigantian Stage of the Dinantian, freshwater terrestrial environments developed locally on the volcanic rise between eruptive phases, but later in the Brigantian the rise was transgressed by marine limestones. Intermittent basaltic eruptions continued into the Amsbergian Stage of the Silesian, accompanied by intrusion of high-level alkaline doleritic sills and associated with strata-bound Zn—Pb mineralisation. Folding later in the Silesian was followed by the intrusion of a suite of quartz-dolerite sills and dykes. These latter were commonly intruded along penecontemporaneous E—W trending faults. The intrusion of the quartz-dolerites may have resulted in remobilisation of earlier strata-bound mineralisation into epigenetic veins.
Carbonate spherules and botryoids as lake floor cements in the East Kirkton Limestone of West Lothian, Scotland
Authors: Walkden Gordon M. , Irwin J. Roddy , Fallick Anthony E. 
Published: November 2011

ABSTRACTThe East Kirkton Limestone is typically a carbonate/organic laminite characterised at many levels by abundant radial-fibrous calcite (RFC) spherules and by less common larger stromatolite-like accretions of laminated botryoidal RFC. The spherules are mostly c. 1 mm in diameter and have cyanophyte and chlorophyte inclusions. Some spherules enclose parallel bundles of complete cyanophyte fibres and probably grew within a living cyanophyte mat. The botryoidal accretions were commonly seeded upon wood and other exposed organic remains such as bone, and they completely enclose twigs and branches where these were held above the sediment surface. Botryoidal accretions commonly contain the remains of a benthos of cyanophytes, chlorophytes and ostracods.Both types of calcite have carbon and oxygen stable isotope values similar to those of known fresh-water precipitates. Their stable isotope and trace element geochemistries are consistent with precipitation on the floor of a tropical fresh-water lake within a volcanic setting, but removed from the influence of any hot-spring activity. Spherules and botroids are mineralogically closely similar and, whilst precipitation may have been biogenically mediated, they are regarded as passive lake floor cements.The carbonate laminae are dominated by rhombohedral calcite. Many of these laminae may have originated as calcite suspensoids which settled to the lake floor during relatively brief precipitation events, blanketing the normally richly organic substrate, smothering the cyanophyte mats, and leading to the preservation of individual organic laminae. Crystals later became enlarged and intergrown within the sediment, but this occurred early and prior to significant compaction, because detail of fragile and degradable organic constituents is commonly preserved. The likely source of the carbonate is through leaching of the local basic volcanic terrain. The precipitation of two types of calcite implies regular fluctuations in the chemistry of the lake waters, or in the factors controlling precipitation, which may have been a biogenic and/or seasonal effect.
Scottish Carboniferous fresh-water limestones in their regional setting
Authors: Whyte Martin A. 
Published: November 2011

ABSTRACTThe East Kirkton Limestone is one of a number of horizons within the Scottish Carboniferous sequence which have commonly been referred to as ‘fresh-water’ limestones. The stratigraphy and distribution of these non-marine carbonates is reviewed and discussed in terms both of Carboniferous palaeogeography and of the interaction between sedimentation, volcanism and tectonics within the Midland Valley graben. Particular attention is given to late Viséan horizons of broadly similar age to the East Kirkton Limestone. The range of carbonate facies and faunas found in these limestones is described and their environmental significance is discussed.