bluuebunny/crossref_metadata_2025 huggingface dataset:
Echinoderms from the Ordovician of the Girvan district, Scotland, with the description of two new species
Authors: Regnéll Gerhard , Paul C. R. C.
Published: November 2011

Two new species of Ordovician echinoderms are described:Pleurocystites mitratusfrom the Kiln Mudstones (Caradoc) at Craighead, andHomocystites beggifrom the Starfish Bed (Ashgill) of Threave Glen. Description of the former necessitated a review of the composition and status of the family Pleurocystitidae. The genus Dipleurocystis Jaekel 1918 and the subgeneraPleurocystites s.s.andPleurocystella Paul, 1967 are rejected. The number and type of pectinirhombs; size of the periproct, composition of its border and nature of its covering plates (periproctals), and the ornament of the thecal plates and proximal columnals, are the most useful taxonomic criteria within the Pleurocystitidae.Pleurocystites mitratusis characterized by three conjunct pectinirhombs, a symmetrical theca without a rectal lobe and small periproctals each with a central pit.Homocystites beggiis distinguished from the closely relatedH. constrictusby strong granular ornament on the thecal plates.

Other echinoderm remains include plates of a cheirocrinid cystoid from the Kiln Mudstones.
The pelmatozoan fauna of the High Mains Formation (Ordovician: Hirnantian) of the Craighead Inlier, Strathclyde
Authors: Donovan S. K. , Harper D. A. T.
Published: November 2011

Faunas of disarticulated ossicles, particularly columnals, are a potentially important source of data for helping to elucidate the patterns of evolution and extinction shown by pelmatozoans in the late Ordovician. The columnal fauna of the Hirnantian High Mains Formation, Craighead Inlier, Strathclyde, includes the following morphotaxa:Cyclocyclicus(col.)foraminosussp. nov.;Cyclocyclicus(col.)periogmossp. nov.;Hypsinomocrinus(col.)lewisigen. et sp. nov.;Tetragonotetragonalis(col.)girvanensissp. nov.; andPentagonopentagonalis(col.) sp. This is the first Hirnantian columnal fauna to be described from the North American province; it is distinctly different from Hirnantian columnal biota described from Wales and Kazakhstan.
Basement–cover relationships in the East Greenland Caledonides: evidence from the Eleonore Bay Supergroup at Ardencaple Fjord
Authors: Soper N. J. , Higgins A. K.
Published: November 2011

The Eleonore Bay Supergroup (EBG) is a 16 km-thick shallow-water sequence of Neoproterozoic age that is preserved within the East Greenland Caledonides in several tracts, surrounded by crystalline gneisses and schistose supracrustal rocks. The apparent downward transition from non-metamorphic EBG into gneiss gave rise to the classic ‘stockwerke’ hypothesis, in which all the metamorphism was regarded as Caledonian, and differences in grade were ascribed to the ascent of a migmatite front to different levels within the orogen. Field and isotopic studies in the 1970s however revealed that the underlying gneisses and schists had undergone orogenic reworking in mid-Proterozoic time; the EBG–basement contact was then interpreted as an approximately bedding-parallel décollement with apparent lag geometry, that is with EBG cover rocks in its hangingwall.

Recent work in the northernmost EBG tract, at Ardencaple Fjord, has shed light on the problems posed by the basal relationships of the EBG, and together with regional structural and stratigraphic data leads to the following interpretation. There are two regionally important basement-cover interfaces within the East Greenland Caledonides. The earlier one is between Archaean/early Proterozoic gneisses and early Proterozoic supracrustal rocks, which were pervasively deformed in mid-Proterozoic time and form the basement to the Neoproterozoic Eleonore Bay cover sequence. This was deposited on a vast, continually subsiding shelf that is now preserved in East and NE Greenland and Svalbard, and contains Grenville detritus. EBG deposition was terminated by major extensional faulting of Vendian age; the succeeding Tillite Group is interpreted as a syn-rift sequence, presumably associated with the opening of Iapetus.

The EBG–basement contacts that are not late faults are inferred to be extensional shear zones of Vendian age. These were reactivated in compression during the Caledonian orogeny in the Silurian, with metamorphic and fabric convergence, which accounts for the apparent downward transition from sedimentary rocks through schists into gneisses. Caledonian shortening was not large; inversion of the Vendian grabens was incomplete, so that the marginal shear zones retained their lag geometry and large tracts of low grade Eleonore Bay sediments are preserved at the present erosion level, surrounded by Proterozoic basement rocks, within the Caledonian belt of East Greenland.
A Lower Devonian sporomorph assemblage from the Midland Valley of Scotland
Authors: Wellman Charles H.
Published: November 2011

A sporomorph assemblage recovered from the Sandy's Creek Beds, which constitute a diminutive fault bounded inlier on the west coast of the Midland Valley of Scotland, is described. Four species of trilete spore and the genus Fustisispora, a monospecific cryptospore genus, are proposed as new. The sporomorph assemblage is attributed an early Devonian, late–early to early–late Lochkovian age, and is interpreted as accumulating in a continental environment. The Sandy's Creek Beds are correlated herein with the upper part of the Arbuthnott Group which crops out in the north-east of the Midland Valley. Comparison with other sporomorph assemblages of similar age indicates that minor regional variation exists. It is suggested that this is related to small-scale regional variation in the composition of vegetation.
The Lower Ordovician brachiopod genusLamanskyaand the Family Elkaniidae
Authors: Holmer Lars E.
Published: November 2011

The Lower Ordovician (Oeland Series) type species ofLamanskya, L. splendensMoberg & Segerberg 1906, was described originally as an articulate brachiopod, but it is here redescribed and referred to the lingulid Family Elkaniidae.L. splendensranges from the late Tremadoc to the early Arenig in Baltoscandia (Norway, Sweden, Estonia, and the St Petersburg district of Russia).Aulonotreta kuraganicaAndreeva 1972 from the Lower Ordovician of the Ural Mountains is also redescribed and referred toLamanskya. The genusDictyobolusWilliams & Curry 1985, from the Lower Ordovician of Ireland, is a junior synomym ofLamanskya. All species of the genus are strongly biconvex, and have a well-developed ornamentation of elongate lenticular pits. The problematic GenusVolborthiavon Moller 1870 is also considered tentatively to belong within the Elkaniidae.
Depositional and geotectonic history of the Gala area, eastern Southern Uplands, Scotland
Authors: Kassi A. M. , Weir J. A.
Published: November 2011

The Ordovician and Silurian successions between Falahill and Galashiels encompass six flysch-dominated formations: the Upper Ordovician Portpatrick and Shinnel Formations representing the Leadhills Group, the Llandovery Mindork, Garheugh, and Buckholm Formations together comprising the Gala Group, and a formation indeterminate of age within the Hawick Group. Southward ensialic andesitic volcanic arc and northward low- to medium-grade sialic sources contributed sediment, whilst ophiolitic and subduction-related sources made minor contributions. Deposition took place firstly, in a SE-migrating back-arc basin bordering the northerly source, the Laurentian continent. Subsequent NW-directed underthrusting led to formation out of the back-arc basin of an imbricate thrust stack which migrated southeastwards. Ultimately a foreland successor basin formed ahead of the rising thrust stack.

Flysch units are typically associated with linear outcrops of Moffat Shales which are the loci of major steep SE-translating reverse faults, two of which participate in a late-stage sinistral strike–slip duplex with large-scale imbrication. The faults divide the succession into a sequence of tectonostratigraphic blocks, successively younger to the SE. At least six of the ten blocks customarily recognised in the Southern Uplands, Blocks 3–8, are represented, some of which coincide with single or complete formations.
Revision and definition of the C. wilsoni graptolite Zone (middle Ordovician) of southern Scotland
Authors: Williams S. Henry
Published: November 2011

Critical collecting, measurement of sections and taxonomic reassessment through the Climacograptus wilsoni Zone (basal Lower Hartfell Formation) of the southern Scottish graptolite zonal sequence suggests that, although only locally developed, it is an easily recognisable and useful biostratigraphic interval. The North Cliff of Hartfell Spa is defined as type section for both the base of the Lower Hartfell Formation and that of the C. wilsoni Zone. The zonal assemblage is figured and described, with particular emphasis being placed on the distinctive species C. wilsoni which has not been redescribed since the beginning of this century.
The dykes and sills of the Early Tertiary Faeroe Island basalt plateau
Authors: Hald N. , Waagstein R.
Published: November 2011

The Early Tertiary basalt plateau of the Faeroe Islands is cut by dykes and sills. Chemical analyses show a two-fold division of the intrusive rocks into a group of low-TiO2(0·73–1·93%), MORB-type tholeiitic basalts and a group of high-TiO2(2·09–3·90%) tholeiitic basalts. The low-TiO2group comprises about 15% picrites and olivine-phyric basalts and 85% plagioclase-phyric basalts, and shows a chemical range largely explicable in terms of low-pressure fractional crystallisation of olivine ± plagioclase ± clinopyroxene. The high-TiO2group is strongly dominated by plagioclase-phyric basalts with only few olivine-phyric compositions. The chemical trends are less regular than those formed by the low-TiO2basalt dykes and a number of subgroups may be identified on the basis of bulk rock chemistry. Dykes belonging to a specific subgroup were probably fed from the same magma chamber.

Petrographically and chemically the dykes and sills are clearly related to the upper 2·5 km of the lava sequence. Field evidence suggests that some of the dykes were contemporaneous with the exposed lavas, while other dykes and the sills were intruded in response to a slight doming of the plateau during the final stages of volcanic activity. Our investigations demonstrate that high-TiO2and low-TiO2magmas were both emplaced until the very end of magmatism, with the latter being mainly concentrated in the northern part of the archipelago. We briefly sketch a possible relationship between the supposed NE-Atlantic mantle plume, the distribution of the various magma types and the location of the Early Tertiary continental splitting zone north of the islands.
Reply to comments by J. H. Bédard and R. S. J. Sparks
Authors: Volker J. A. , Upton B. G. J.
Published: November 2011

Bédard and Sparks' (BS) comments are very much appreciated as they giveus the opportunity to emphasise certain aspects of our observations which, in turn, mayclarify the discussion on the petrogenesis of the Rhum ultrabasic rocks. BS raised two questions which we answer below.
The Silurian myodocope ostracodeEntomozoefrom the Pentland Hills, Scotland: its taxonomic, ecological and phylogenetic significance and the affinity of the bolbozoid myodocopes
Authors: Siveter David J. , Vannier Jean M. C.
Published: November 2011

The monotypic ostracodeEntomozoe(pro Entomis) (Superorder Myodocopa) from the Silurian of Scotland, type genus of the Entomozoidae, is revised for the first time since being established in 1861. Based on the type and new collections ofEntomozoe tuberosa(Jones, 1861), the genus shows affinity to bolbozoid myodocopes rather than to forms hitherto universally considered as ‘typical’ entomozoid myodocopes. The families Entomozoidae and Bolbozoidae are considered synonymous. In the interests of stability of nomenclature, in particular to preserve the traditionally understood usage of the taxon Entomozoidae, a case must be made to the International Commission on Zoological Nomenclature to set aside any previous designations and to establish a new type-species forEntomozoe.

Entomozoe, from the Llandovery Series, is the earliest known myodocope in the fossil record. It occurs as part of a low diversity, shallow water, nearshore assemblage. In contrast to other, but younger, Silurian bolbozoid myodocopes, it is probably a benthic form. The differences in the anterior shell morphology of Silurian bolbozoid taxa possibly reflect changes both in soft-part morphology and from benthic to pelagic lifestyles within the group.

Both bolbozoid and ‘entomozoid’ myodocopes are assigned to the Order Myodocopida rather than to the Order Halocypridida, though the taxonomic affinity of the ‘entomozoids’ is, at best, uncertain.
MAVIS: Geophysical constraints on the structure of the Carboniferous basin of West Lothian, Scotland
Authors: Dentith M. C. , Hall J.
Published: November 2011

The results of recent seismic refraction profiling across the Carboniferous West Lothian basin are described. Data from two 90-km refraction lines within the Midland Valley are combined with short–medium range, c. 30 km, profiles recorded using quarry-blast sources. Integration of seismic, gravity and structural data suggest thin-skinned deformation with at least two levels of detachment. Major faults mapped at the surface define domains comprised of thin flakes deformed into dome and basin structures. The data are interpreted in terms of a dextral strike-slip linked fault model for the region.
A reappraisal of the Dinantian floras at Oxroad Bay, East Lothian, Scotland. 1. Floristics and the development of whole-plant concepts
Authors: Bateman Richard M. , Rothwell Gar W.
Published: November 2011

Re-investigation of species-rich late Tournaisian floras at Oxroad Bay reveals eight plant-bearing exposures that represent four distinct stratigraphic levels. The allochthonous megafossil assemblages vary in degrees of disarticulation, modes of preservation and taxonomic composition. Within-site stratigraphic distributions are presented for 43 anatomically-preserved organ-species; of these, 12 are new to science, 18 have not previously been recorded at the locality, 21 are illustrated from the locality for the first time and 19 are currently considered endemic. Another six have been recorded in error from unprovenanced water-worn blocks. Nineteen adpressed organ-species are also described. Methods and concepts of whole-plant reconstruction are reviewed. At least 11 whole-plant species occur at Oxroad Bay. The lycopsids comprise an enigmatic plant with anAsteroxylon-like stele and two morphologically- and ecologically-distinct species ofOxroadia. A new species ofProtocalamitesdemonstrates the earliest evidence of heterospory and tuberoid stem-bases in the sphenopsid clade.CladoxylonandStauropterisrepresent the pteropsids. At least five lyginopterid pteridosperm species are present. They include both trees (Eristophyton, Bilignea) and shrubs/pseudoherbs (e.g.Tetrastichiaand theTriradioxylon–Calathopteris–Oxroadopteris–‘Tristichia’ plexus), suggesting a range of life strategies. Their diversity has complicated attempts to reconstruct whole-plants, though attachment is demonstrated between several ovules and cupules, and several ovules and pollen-organs are correlated using shared microspores. Elements of particular evolutionary significance include the ‘megacupule’Calathospermumand a structurally similar pollen-organ aggregate, a bisexualPullarithecacupule, and a complete ontogenetic sequence ofHydraspermaovules. Comparable Dinantian floras are reviewed.
A reappraisal of the Dinantian floras at Oxroad Bay, East Lothian, Scotland. 2. Volcanicity, palaeoenvironments and palaeoecology
Authors: Bateman Richard M. , Scott Andrew C.
Published: November 2011

The classic late Tournaisian plant-bearing locality at Oxroad Bay was investigated by detailed field mapping, lithological logging, studies of clast orientation, thin-section petrography and analyses of bulk geochemistry. The lithologically and structurally complex,c. 45 m-thick succession includes eight plant-bearing exposures (each consisting of up to 16 phytofossiliferous horizons) that have yielded 43 anatomically-preserved organ-species and 19 adpressed organ-species. All floral assemblages are allochthonouss.l.and demonstrate a wide range of preservation states. They occur in five successive facies (braided flood-plain, shallow volcanigenic lacustrine, terrestrial mass-flow/base-surge, shallow biogenic lacustrine, dominantly terrestrial reworked ashes) that reflect increasing influence of several basaltic tuff-ring volcanoes on an ocean-marginal lowland bordering the Southern Uplands Massif. The variable local climate reflected proximity to the proto-North Sea and eruptive seeding of the atmosphere with ash particles. Base-surges, seismically-initiated mass-flows and volcanically-induced wildfires restricted the development of mature soils and of edaphic climax communities. These disturbances created a sequence of mosaic palaeocatenas that supported a wide range of sub-communities at any one moment in time. At least some of the relativelyk-selected species that occupied the preceding, fluvially-dominated terrain were extirpated by the persistent volcanism, yielding to immigrants that were better pre-adapted to the unstable environment. Low levels of competition allowed non-adaptiven-selection, enhancing the establishment potential of evolutionary innovations.
Laxfordian structure, strain distribution and kinematic interpretation of the Kenmore Inlier, Loch Torridon: anatomy of a major Lewisian shear zone
Authors: Niamatullah M. , Park R. G.
Published: November 2011

The Kenmore inlier exposes the most intensely deformed part of a major Laxfordian shear zone whose NE margin occurs at Diabaig, N of Loch Torridon. The Laxfordian (post-Scourie dyke) deformation commences with two very intense deformations D1 and D2, producing LS fabrics in dykes and gneisses associated with heterogeneous, locally very large, and typically prolate strains under amphibolite-facies metamorphism. D2 also produced widespread mesoscopic folds. The finite strain was measured at 135 localities using grain-aggregate shapes in Scourie dykes. The combined D1-D2 elongation lineation plunges gently to NW or SE, and the planar fabric appears to have been sub-horizontal before the D3 deformation, which produced NW-SE upright folds under retrogressive metamorphism.

The D1-D2 structure is attributed to a major sub-horizontal shear zone with a top-to-NW movement, a minimum vertical width of 2·5 km and estimated minimum displacement of c. 19 km. The upper (NE) wall of the shear zone at Diabaig exhibits dextral-normal (NE-down) D1 movements. The D2 structures are attributed to superimposition of sub-horizontal movements on earlier inclined D1 fabrics as the shear zone evolves. The D3 refolding reflects a change to a dextral transpressive regime.
Sensory field maps of proetide trilobites
Authors: Wilmot Nadine V.
Published: November 2011

The sensory fields of four Wenlock trilobitesProetus (Proetus) concinnus, Warburgella (Warburgella) stokesii, Warburgella (Warburgella) scutterdinensis, andHarpidella (Harpidella) mauraare described and found to be species specific. Certain features, such as the small cell polygon size, and prismatic layer comprising about one tenth of the cuticle thickness are characteristic of Order Proetida. Intraspecific variation is related to ontogenetic development, most markedly in the field of the free cheek ofP. (P.) concinnus.The proetid occipital pustule may have functioned as a light-sensitive organ. The tropidiumW. (W.) stokesiiis a ridge with a central canal or groove, rather than a tubular structure, and probably contained a sensory receptor rather than a circulatory system. Despite microstructural distribution being species specific, it is of limited practical value in taxonomy as the fine details are easily lost during diagenesis.
Location of trace elements in soil profiles: total contents of particle-size separates
Authors: Berrow M. L. , Mitchell R. L.
Published: November 2011

Total contents of 21 trace elements were determined in particle size separates from the horizons of four profiles, two freely drained and two very poorly drained, of Scottish soils on drifts of basic igneous and granitic origin. Trace elements, including Co, Cu, Li, Mn, Ni, V, Zn and also Fe contained in the more easily weathered ferromagnesian minerals, tend to accumulate in the clay and silt. Elements such as Ti and Zr and also La and Y contained in resistant minerals accumulate in the silt or fine sand. Ti and Zr are mobilised to some extent, however, as these elements are present in the clay separates and in some cases show enrichment therein.

The alkali metals Li and Rb accumulate in the silt and clay particularly in the granitic soils, while the alkaline earth metals Ba and Sr occur in greatest concentrations in the sands due to their being held largely in resistant feldspar minerals. On release these elements are not strongly adsorbed by the clay.

Very poor pedological drainage leads to increased weathering and release of such elements as Co, Cu, Ni, V and Zn from the coarse or fine sands with correspondingly greater enrichment of the associated silt and clay. Weathering and enrichment of the fine fractions takes place largely in situ, there being little evidence of downward translocation due to leaching.
The Order Adelospondyli: Carboniferous lepospondyl amphibians
Authors: Andrews S. M. , Carroll R. L.
Published: November 2011

The Order Adelospondyli, an isolated group of amphibians from the Carboniferous of the Edinburgh area, is redescribed and distinguished from other early tetrapods. Although systematics of genera and species is unsatisfactory, the group seems monophyletic, since as far as they are known, all conform to a single overall structural plan. There is an entire skull roof with a reduced complement of bones in an unique pattern, a highly characteristic marginal dentition, a massive hyoid apparatus, at least 70 holospondylous trunk vertebrae, and (like some other Lower Carboniferous tetrapods) a shoulder region with a heavy dermal girdle but no trace of ossified limbs or endochondral girdle. Adelogyrinids show no special affinity with other Palaeozoic amphibians: the vertebral characters in which they resemble microsaurs, lysorophids, aïstopods, and nectrideans may have evolved more than once among early tetrapods, and the shoulder girdle and neural arch characters shared with labyrinthodonts are probably primitive. The adelogyrinids thus illustrate the more general problems of establishing interrelationships among early tetrapods. Their way of life is discussed.
Microfossil analyses and radiocarbon dating of depositional sequences related to Holocene sea-level change in the Forth valley, Scotland
Authors: Robinson Marie
Published: November 2011

Microfossil (pollen and diatom) evidence is presented from sites in the Forth valley, south-central Scotland, where alternating organic and estuarine minerogenic deposits record the influence of the changing Holocene sea level. Radiocarbon dating confirms the age of the Main and Low Buried Beaches, and of the Main Postglacial Transgression, in different parts of the Forth valley. Radiocarbon dates on shells from beds in the carse sediment and a Mesolithic shell midden near Grangemouth relate to the falling sea level in the 4th and 5th millennia BP. Sea-level curves are constructed for the western and eastern Forth valley.
Geophysical surveys of the East Kirkton Limestone, Viséan, West Lothian, Scotland
Authors: Doody Jonathan J. , McGill Rona A. R. , Darby David , Smythe David K.
Published: November 2011

Magnetic and resistivity geophysical surveys conducted across the only known exposure of the East Kirkton Limestone have produced new information upon its extent. This is important to determine because of its unique faunal assemblage and possible hot spring deposition, suggesting a potential for precious metal mineralisation. Magnetic anomalies are attributed to basalts within the Bathgate Hills Volcanic Formation. Modelling of the magnetic data demonstrates a general dip to the west of about 25°, and the presence of significant local faulting. Modelling of vertical electrical sounding data shows the East Kirkton sequence (the limestone and associated beds) to be a low resistivity layer within the more highly resistive volcanic sequence. The East Kirkton sequence is seen to deepen to the west, and also to the north probably by faulting. Therefore the present exposure is the only near surface occurrence of the East Kirkton Limestone locally, but within the area of the survey no lateral limits to the formation are observed.
Volcanogenic sediments of the East Kirkton Limestone (Viséan) of West Lothian, Scotland
Authors: Durant Graham P.
Published: November 2011

Volcanogenic sediments form a significant part of the East Kirkton Limestone, with thin tuff units occurring at several levels and pyroclastic fragments being an important constituent of the coarser clastic limestone units.

The tuffs have been extensively altered during diagenesis but recognisable pseudomorphs after olivine and plagioclase phenocrysts confirm the basaltic nature of the volcanism. The considerable lateral variations in thickness of the tuff horizons in conjunction with the poorly sorted and lithologically heterogeneous nature of the tuffs indicate an epiclastic origin for the volcanogenic sediments. Well-rounded volcanic rock fragments—products of erosion—occur with angular fragments within the tuffs. Blocky tuffs in the lower part of the formation contain charred wood fragments, rip-up clasts of limestone and disarticulated amphibian bones. Graded bedding at several horizons and the presence of ostracods within some tuffs confirms subaqueous deposition.

The findings are consistent with the usual, dominantly epiclastic products of basaltic volcanism, in an equatorial, continental, humid environment, with assorted debris being washed from the flanks of a volcano into a shallow lake.
Regional setting of Carboniferous volcanism in the Midland Valley of Scotland
Authors: Upton B. G. J.
Published: November 2011

In the early Carboniferous, the portion of continental crust that now constitutes Scotland lay within the hinterland of a large continent that extended westwards to what is now the western parts of North America, eastwards to what is now the Urals and northwards towards what is now Arctic Canada, Greenland, Scandinavia and Russia. Open ocean probably lay at between 600 and 1000 km to the south. Whereas mountainous terrane lay to the north of the Highland Boundary fault, the Scottish Midland Valley, like the Northumberland Trough further south, was a region of low relief subject to periodic marine incursions.

A period of block faulting and concomitant basaltic volcanism commenced at the beginning of the Carboniferous at c. 350 Ma. This had manifestations in various regions of the British Isles from the south-west of England to the west of Ireland and as far north as the Midland Valley (Francis 1978, 1991; Upton 1982; Cameron and Stephenson 1985).
Arborescent gymnosperms from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Galtier Jean , Scott Andrew C.
Published: November 2011

Plants of gymnospermous affinities are the most important component of the flora at East Kirkton. Four genera of anatomically preserved gymnosperm stems with well developed secondary xylem are interpreted as arborescent. The largest specimens (trunks up to 50 cm in diameter) are attributed to the genus Pitus. Features of the wood, including ray size, are characteristic of the species Pitus withamii Lindley & Hutton which has long been described from the Strathclyde (former Oil-Shale) Group of Scotland. Decorticated axes of Eristophyton fasciculare are more common; their study has enlarged our concept of the species with regard to maximum diameter, internode length and phloem organisation. Similarly, the decorticated specimens of Bilignea solida Kidston found at East Kirkton exceed in diameter the original material described from Ayrshire. The fourth taxon is Stanwoodia recently described by Galtier and Scott (1991). In all these plants, features of leaf traces suggest that leaves were relatively large and densely borne on ultimate branches. These leaves were shed ultimately, prior to a later phase of wood development; they certainly correspond to (? most of) the compression foliage commonly found in association: Sphenopteridium, Adiantites and Spathulopteris.
Actinopterygian and acanthodian fishes from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Coates M. I.
Published: November 2011

Forty-one specimens of acanthodians and actinopterygians were examined from Units 26 to 38 of the Geikie Tuff, Little Cliff Shale and East Kirkton Limestone of the Viséan East Kirkton Limestone sequence. The results yielded six actinopterygian species including a platysomid and two probable juveniles of uncertain affinities, and three acanthodians including two acanthodidids and a climatiid-like denticle. Most specimens consist of isolated bones and scales, but articulated remains of an acanthodian and actinopterygians were found in Units 37 and 38 of the East Kirkton Limestone. The faunal composition is characteristically Oil-Shale in aspect and resembles that of Broxburn (Pumpherston). The presence of deep-bodied and juvenile fishes in the same strata combined with the mode of preservation indicate a palaeohabitat with limited current action and a soft substrate.
Coprolites from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Sumner Daphne
Published: November 2011

Coprolites are most common in the transition zone between the East Kirkton Limestone and the Little Cliff Shale. One hundred and twenty five samples are classified in five groups on the basis of size and shape. Within these groups distinctive subgroups are described. Many of the coprolites are believed to have been produced by fish, but some could have been produced by eurypterids and aquatic tetrapods.
The Hamilton Konservat-Lagerstätte: Stephanian terrestrial biota in a marginal-marine setting
Authors: Schultze Hans-Peter , Maples Christopher G. , Cunningham Christopher R.
Published: November 2011

The Stephanian Konservat-Lagerstätte of Hamilton, Kansas, deposited in a marine-estuarine environment preserves a mixture of terrestrial, fresh-water, and marine fossil organisms. The marine component is the most diverse taxonomically, whereas one ostracod species, commonly interpreted as a fresh-water form, together with vascular plant debris dominates volumetrically. Well-preserved terrestrial and aquatic vertebrates and arthropods were embedded in rapidly deposited calcareous mud conducive to microbial early-diagenesis of vertebrate soft tissues in a tidal estuarine setting. Many vertebrate fossils show no evidence of preburial decay or disarticulation. Dark-coloured body silhouettes (‘skin preservation’) are composed of calcitic bacteria, calcite crystals and organic material, and have been interpreted to reflect preservation under saline conditions. The aquatic vertebrates had a broader tolerance of salinity than today. The fishes were perhaps migratory (anadromous or catadromous), and some used the estuarine environment for spawning. The tetrapods (dissorophid amphibians) retained their tolerance to salinity from their marine ancestors and were able to spawn in near-shore environments. The terrestrial biota was dominated by the conifer Walchia and was subjected to forest fires, as evidenced by preserved charcoal fragments.
XIII.—Crystal Growth of Forsteritic Olivine in Magmas and Melts
Authors: Drever H. I. , Johnston R.
Published: November 2011

Synopsis

One of the writers' main aims has been to help to prepare the way for a new approach to problems in which the natural occurrence of forsteritic olivines is a vital factor. Variation in their shapes and textural relations in minor intrusions, lavas and melts is examined and the historical development of concepts of their growth and resorption, particularly in magmas, is traced. Particular attention is focused on the olivines of picritic, minor intrusions. It is concluded that in the interpretation of olivine shapes there has been discrimination in favour of magmatic resorption rather than skeletal crystallization. From a wide and detailed survey of forsteritic olivines it is established that they tend to grow rapidly and that their phenomenal variation in habit and shape is probably due to a specific growth sensitivity to slight environmental differences. Concepts of the physical conditions leading to skeletal crystallization are briefly reviewed and discussed.
Variations in magnetic properties of Unit 10, Eastern Layered Intrusion, Isle of Rum, Scotland: implications for patterns of high temperature hydrothermal alteration
Authors: Housden J. , O'Reilly W. , Day S. J.
Published: November 2011

An in situ magnetic susceptibility survey of Unit 10 of the Eastern Layered Intrusion of the Isle of Rum, in a line perpendicular to the strike, was carried out as a guide to selecting sampling sites for subsequent laboratory magnetic studies. These laboratory studies indicate that the dominant magnetic phase is magnetite. An effective particle size of the magnetite was derived from the magnetic data: it was found that high concentrations (∼0·3%) of magnetite in the perioditites were achieved by the presence of fewer but larger particles. The regions of lower magnetite concentration (∼0·01%), which are mainly in the plagioclase-rich rocks, contain more abundant but smaller particles.

The variations in magnetic properties correlate with the abundance and inferred temperatures of formation of hydrothermal alteration minerals in the rocks. Petrographic observations indicate temperatures of alteration of 500–800°C in the olivine-rich peridodites in the lower part of the Unit, but of the order of 300°C in the plagioclase-rich rocks at the top of the Unit.

These relationships between magnetic mineralogy and hydrothermal alteration suggest that the magnetite was produced by olivine oxidation during hydrothermal alteration. It is proposed that variations in the magnetic properties of layered cumulate rocks may be used to map out variations in the temperature and intensity of hydrothermal fluid flow. The variations in the Unit 10 rocks studied are interpreted as indicating control of high-temperature hydrothermal fluid flow through them by contrast in permeability between brittle peridotites and quasiplastic plagioclase-rich rocks.
Ascent mechanism of felsic magmas: news and views
Authors: Weinberg Roberto Ferrez
Published: November 2011

Diapirism has been discredited as a transport mechanism for magmas partly because diapirs seem to be unable to bring magmas to shallow crustal levels (<10km) and partly because recent developments in the theory of dyke propagation have shown that sufficiently wide dykes are able to efficiently transport felsic magmas through the crust. However, it is still unclear how felsic dykes grow to widths that allow them to propagate faster than they close by magma freezing. Ultimately, it may be the ability of felsic dykes to grow within the source that controls which mechanism dominates ascent.

The ability of dykes to propagate, from the top of rising diapirs depends among other factors on the changing temperature gradient of the wall rocks. The steep gradient around rapidly rising diapirs in the low viscosity lower crust will cause dykes to freeze. As diapirs rise to colder stiffer crust and decelerate, heat diffuses further from the diapir, resulting in shallower temperature gradients that favour dyke propagation. The mechanism may thus swap, during ascent, from diapirism to dyking. Calculations of the thermal evolution of diapirs and their surroundings show that basaltic diapirs may never form because they would be drained by dykes at a very early stage; felsic diapirs may be unable to give rise to successful dykes, whereas diapirs of intermediate magmas may propagate dykes during ascent.
Experimental constraints on the compositional evolution of crustal magmas
Authors: Nekvasil Hanna , Carroll William
Published: November 2011

Recent water-undersaturated phase equilibrium data on the subsystems of the granite-H2O system have provided important new constraints on the topology of the cotectic surfaces and hence on the compositional evolution of felsic magmas. The effect of water on phase relations can be deduced from a comparison of anhydrous and H2O-saturated data or from data obtained in the presence of a CO2-bearing fluid. However, although new experimental evidence indicates that the silica enrichment of evolving H2O-undersaturated, H2O-unbuffered melts during the co-precipitation of quartz and feldspar is as previously thought for orthoclase-rich compositions, it suggests that such a trend is considerably less for Ab-rich compositions. For water-poor trachytic melts, the newly recognised strong destabilisation of the sanidine melt component relative to the anorthite melt component with increasing water content indicates that the co-precipitation of two feldspars will result in saturation of the melt with ternary alkali feldspar at an earlier stage (i.e. higher melt anorthite content) than previously thought. This, in turn, implies that the melt differentiation path will have a greater component of anorthite depletion during the equilibrium co-precipitation of ternary feldspars and that the melt will remain in the peritectic region of the two feldspar plus liquid surface over a greater interval of crystallisation, thereby enhancing the possibility that the resoption of plagioclase during the early stages of equilibrium with alkali feldspar may go to completion. Comparison of CO2-free and CO2-bearing haplogranitic phase equilibrium data suggests that CO2 may be playing an independent part in the modification of phase equilibria and may induce a significant destabilisation of the orthoclase melt component.
Monzonite suites: the innermost Cordilleran plutonism of Patagonia
Authors: Rapela C. W. , Pankhurst R. J.
Published: November 2011

In Patagonia a Triassic-Early Jurassic Cordilleran interior magmatic belt preceded the widespread eruption of Middle Jurassic syn-extensional rhyolites. Two plutons (La Calandria and La Leona) represent the easternmost plutonic rocks of this belt, > 750 km east of the present oceanic trench. They define a high-K calc-alkaline monzonite series in contrast with the main Andinotype arc magmatism of the Pacific margin: they are enriched in large ion lithophile elements (K, Rb, Ba, Sr and Th), LREE and P2O5and depleted in HREE and Y, with low FeO*/MgO ratio. The range of observed compositions (56-76% SiO2) resulted from high-level fractionation of plagioclase, hornbleńde, biotite, K-feldspar and accessories (sphene, apatite and zircon).

Initial87Sr/86Sr ratios, average εNdtand mean depleted-mantle Nd model ages of the two plutons are 0·70487, -0·5 and 1050 Ma for La Calandria and 0·70509, -1·4 and 1125 Ma for La Leona, respectively. They are thus isotopically more primitive than the Middle Jurassic rhyolites, previously attributed to partial melting of Mesoproterozoic mafic lower crust. The preferred model for the origin of the monzonites is remelting of an amphibole- + garnet-bearing, plagioclase-poor, high-K mafic source (?underplating). This occurred in a distal sector of a dying oblique subduction regime, immediately preceding the extensional silicic volcanism.
Non-linear dynamics, chaos, complexity and enclaves in granitoid magmas
Authors: Flinders James , Clemens John D.
Published: November 2011

Most natural systems display non-linear dynamic behaviour. This should be true for magma mingling and mixing processes, which may be chaotic. The equations that most nearly represent how a chaotic natural system behaves are insoluble, so modelling involves linearisation. The difference between the solution of the linearised and ‘true’ equation is assumed to be small because the discarded terms are assumed to be unimportant. This may be very misleading because the importance of such terms is both unknown and unknowable. Linearised equations are generally poor descriptors of nature and are incapable of either predicting or retrodicting the evolution of most natural systems. Viewed in two dimensions, the mixing of two or more visually contrasting fluids produces patterns by folding and stretching. This increases the interfacial area and reduces striation thickness. This provides visual analogues of the deterministic chaos within a dynamic magma system, in which an enclave magma is mingling and mixing with a host magma. Here, two initially adjacent enclave blobs may be driven arbitrarily and exponentially far apart, while undergoing independent (and possibly dissimilar) changes in their composition. Examples are given of the wildly different morphologies, chemical characteristics and Nd isotope systematics of microgranitoid enclaves within individual felsic magmas, and it is concluded that these contrasts represent different stages in the temporal evolution of a complex magma system driven by nonlinear dynamics. If this is true, there are major implications for the interpretation of the parts played by enclaves in the genesis and evolution of granitoid magmas.
Mafic-silicic layered intrusions: the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers
Authors: Wiebe R. A.
Published: November 2011

Plutonic complexes with interlayered mafic and silicic rocks commonly contain layers (1–50 m thick) with a chilled gabbroic base that grades upwards to dioritic or silicic cumulates. Each chilled base records the infusion of new basaltic magma into the chamber. Some layers preserve a record of double-diffusive convection with hotter, denser mafic magma beneath silicic magma. Processes of hybridisation include mechanical mixing of crystals and selective exchange of H2O, alkalis and isotopes. These effects are convected away from the boundary into the interiors of both magmas. Fractional crystallisation aad replenishment of the mafic magma can also generate intermediate magma layers highly enriched in incompatible elements.

Basaltic infusions into silicic magma chambers can significantly affect the thermal and chemical character of resident granitic magmas in shallow level chambers. In one Maine pluton, they converted resident I-type granitic magma into A-type granite and, in another, they produced a low-K (trondhjemitic) magma layer beneath normal granitic magma. If comparable interactions occur at deeper crustal levels, selective thermal, chemical and isotopic exchange should probably be even more effective. Because the mafic magmas crystallise first and relatively rapidly, silicic magmas that rise away from deep composite chambers may show little direct evidence (e.g. enclaves) of their prior involvement with mafic magma.
Hydrodynamics of magmatic and meteoric fluids in the vicinity of granitic intrusions
Authors: Hanson R. Brooks
Published: November 2011

Numerical models that account for fluid flow, magmatic and metamorphic fluid production, topography and thermal expansion of the fluid following emplacement of a granitic magma in the upper crust reveal controls on the distribution of magmatic fluids during the evolution of a hydrothermal system. Initially, fluid pressures are close to lithostatic in and near an intrusion, and internally generated magmatic and metamorphic fluids are expelled. Later, fluid pressures drop to hydrostatic values and meteoric fluids circulate throughout the system. High permeabilities and low rates of fluid production accelerate this transition. Fluid production in the magma and wallrocks is the dominant mechanism elevating fluid pressures to lithostatic values. For granitic intrusions, about three to five times as much magmatic fluid is produced as metamorphic fluid. Continuous fluid release from a granitic magma with a vertical dimensions of 10 km produces a dynamic permeability of up to several tens of microdarcies.

Near the surface, topography associated with a typical volcano acts to maintain a shallow meteoric flow system and drive fluids laterally. The exponential decay with depth of the influence of topography on fluid pressures results in a persistent zone of mixing at a depth of 1-2 km between these meteoric fluids and magmatic fluids despite variations in the strength of the magmatic hydrothermal system. However, in shallow systems where fluid release is episodic, dramatic changes in the region of mixing are still possible because fluid pressure is sensitive to variations in the rates of fluid production. At depth, high rates of metamorphic fluid production in the wallrocks and low permeabilities (< 1 μD) produce elevated fluid pressures, which hinder the lateral flow of magmatic fluids. Together, these patterns are consistent with the distribution and evolution of skarns and hydrothermal ore deposits around granitic magmas.
Intrusive metallogenic provinces in eastern Australia based on granite source and composition
Authors: Blevin Phillip L. , Chappell Bruce W. , Allen Charlotte M.
Published: November 2011

Ore element ratios in intrusion-related mineralisation are in part a function of the relative oxidation state and degree of fractionation of the associated granite suite. A continuum from Cu-Au through W to Mo dominated mineralisation related to progressively more fractionated, oxidised I-type magmas can be traced within single suites and supersuites. Such systematic relationships provide strong evidence for the magmatic source of ore elements in granite-related mineral deposits and for the production of the observed ore element ratios dominantly through magmatic processes. The distribution of mineralised intrusive suites can be used to define a series of igneous metallogenic provinces in eastern Australia. In general, there is a correlated evolution in the observed metallogeny (as modelled based on the compatibility of ore elements during fractionation) with increasing degree of chemical evolution of the associated magmatic suite. This is from Cu-Au associated with chemically relatively unevolved magmas, through to Sn and Mo-rich mineralisation associated with highly evolved magmas that had undergone fractional crystallisation. Provinces recognised in that way do not necessarily correlate with the tectonostratigraphic boundaries defined by the near-surface geology, indicating that the areal distribution of some granite source regions in the deep crust is unrelated to upper crustal geology.
Control of redox state and Sr isotopic composition of granitic magmas: a critical evaluation of the role of source rocks
Authors: Pichavant Michel , Hammouda Tahar , Scaillet Bruno
Published: November 2011

The current underlying assumption in most geochemical studies of granitic rocks is that granitic magmas reflect their source regions. However, the mechanisms by which source rocks control the intensive and compositional parameters of the magmas remain poorly known. Recent experimental data are used to evaluate the ‘source rock model’ and to discuss controls of (1) redox states and (2) the Sr isotopic compositions of granitic magmas.

Experimental studies have been performed in parallel on biotite-muscovite and tourmaline-muscovite leucogranites from the High Himalayas. Results under reducing conditions ( = FMQ – 0·5) at 4 kbar and variable suggest that the tourmaline-muscovite granite evolved under progressively more oxidising conditions during crystallisation, up to values more than four log units above the FMQ buffer. Leucogranite magmas thus provide an example of the control of redox conditions by post-segregation rather than by partial melting processes.

Other experiments designed to test the mechanisms of isotopic equilibration of Sr during partial melting of a model crustal assemblage show that kinetic factors can dominate the isotopic signature in the case of source rocks not previously homogenised during an earlier metamorphic event. The possibility is therefore raised that partial melts may not necessarily reflect the Sr isotopic composition of their sources, weakening in a fundamental way the source rock model.