bluuebunny/crossref_metadata_2025 huggingface dataset:
The syntectonic foxdale‐archallagan granite and its metamorphic aureole, isle of man
Authors: Simpson Alexander
Published: February 2007

The small exposed granite at Foxdale is merely part of a much larger intrusion, the Foxdale‐Archallagan granite, which underlies the country‐rock of Manx Slate Series at shallow depth. The granite is post‐F1 in age. It is a syn‐tectonic intrusion and was emplaced during the second (F2) movementphase in the Caledonian tectonic chronology of the Isle of Man. Its final consolidation was achieved during the following F2‐F3 static interval.

The aureole metasediments consist of porphyroblastic contact phyllites and schists similar to those produced by regional metamorphism. A textural study has demonstrated that the para‐crystalline movement responsible for the directional fabric in these rocks is of tectonic origin and F2 in age.

Despite the penetrative, syn‐crystallization F2 deformation of its envelope, the granite itself is little affected though a mild F2 shearing is visible on its southern fringe. Post‐crystalline deformation of the cooled aureole by S3 and F3 crumples took place during the third movement‐phase. Suggestions are made concerning the form of the Foxdale‐Archallagan intrusion in depth. The temporal relationship of the pluton to other syn‐tectonic F2 acid intrusions in the Isle of Man is considered.
Influence of tectonics and palaeoenvironment on late cretaceous clay sedimentation in the upper benue trough, Nigeria
Authors: Enu E. I.
Published: February 2007

The Late Cretaceous sedimentary sequence in the Upper Benue Trough consists of seven formations. Outcrop samples from the type localities of these units were analysed by X‐ray diffraction for their day mineral content. The composition and distribution of the clay minerals are influenced by tectonics, relief and water depth. Three main depositional phases are recognizable on the basis of clay mineral assemblages, two of which are associated with tectonic movements. The first phase, characterized by the presence of chlorite, illite, kaolinite and mixed‐layer clays is common to Albian‐Cenomanian sediments. This phase is succeeded by mixed‐layer clays and smectite‐rich, Turonian‐Early Santonian sediments.

The re‐occurrence of chlorite and illite in association with kaolinite and mixed‐layer clays in the Post‐Santonian sediments constitutes the third depositional phase.

These clay mineral assemblages are indicative of two periods of tectonism (Albian and Late Santonian) and an intervening Turonian‐Early Santonian period of quiescence in the Upper Benue Trough.
New evidence for the relative age of the Ercall Granophyre and its bearing on the Precambrian‐Cambrian boundary in southern Britain
Authors: Cope John C. W. , Gibbons Wes
Published: February 2007

Recent extension of the Ercall Quarry, Shropshire, has revealed an unconformable contact between the Ercall Granophyre and overlying Lower Cambrian sediments. Five metres of basal conglomerate with rare granophyre clasts overlie a weathered granophyre surface and precludes the possibility that the granophyre is intrusive into the quartzite. The age of the Cambrian quartzite is reviewed and is considered to be most probably late Tommotian. The granophyre is therefore pre‐late Tommotian, but has been radiometrically dated as 533 ± 13 Ma (Rb‐Sr WR, Patchett et al. 1980) and 531 ± 5 Ma (U‐Pb zircon, Compston et al. in Cowie and Johnson 1985). If these independent dating methods are recording the age of granophyre intrusion, then the absolute ages of both the Comley Series Lower Cambrian faunas, and therefore the Precambrian‐Cambrian boundary, are younger than is generally recognized.
The stratigraphy, structure and regional significance of the Moine Rocks of Mull, Argyllshire, W. Scotland
Authors: Holdsworth R. E. , Harris A. L. , Roberts A. M.
Published: February 2007

Two right‐way‐up Moine lithostratigraphic units—the Shiaba (older) and Assapol (younger) Groups—are distinguished in the Ross of Mull. These were intruded in the west by the post‐tectonic, Ross‐of‐Mull granite complex at 414 ± 3 Ma. Apparently undisturbed inclusions of Moine metasediments within the granite permit the boundary between the lithostratigraphic units to be followed westward almost to the supposed trace of the Moine thrust in the Sound of Iona. The Shiaba and Assapol Groups which have a transitional, albeit attenuated, stratigraphic contact are correlated with the Morar and Glenfinnan Divisions of Inverness‐shire, the Sgurr Beag ductile thrust (slide) normally found at the Morar/Glenfinnan Division boundary being absent. This implies that the stratigraphic relationship between these two divisions, which is elsewhere obscured by the thrust, is uniquely preserved on Mull.

Within a local, D1‐D4 sequence, D2 and D3 structures are dominant. Originally subhorizontal D2 folds are intensely curvilinear on all scales about an originally flat‐lying, NNW‐SSE trending stretching lineation (L2). In sections parallel to L2, D2 minor folds display a constant sense of vergence throughout the Ross‐of‐Mull Moine Rocks, overturning generally NW‐NNW. The present day structure is dominated by the almost upright, SSW‐plunging D3 Assapol synform which overprints all earlier structures. Tentative correlation of the deformation sequence with that of Inverness‐shire, suggests that the D1‐D2 structures of Mull, with accompanying moderate‐to‐high‐grade metamorphism, may be Precambrian, while the D3 Assapol synform may be Caledonian.

The presence of migmatites of kyanite grade means that metamorphic grade, established during MS1‐MP2, is anomalously high for Moine rocks lying close to the supposed Caldonian front. This suggests that they may lie within one of the higher Caledonian thrust nappes of the North Highland Moine—possibly the Knoydart nappe, where metamorphic grade is comparable. The greenschist facies metamorphism and single phase of deformation affecting the ‘Torridonian’ rocks of Iona presents a significant contrast to the Moine rocks of the Ross of Mull. A major fault in the Sound of Iona is implied, but the Moine thrust itself probably does not outcrop.
A Fissure‐Controlled Acidic Volcanic Centre (Ordovician) at Yr Arddu, North Wales
Authors: Howells M. F. , Campbell S. D. G. , Reedman A. J. , Tunnicliff S. P.
Published: February 2007

The Yr Arddu Tuffs (Ordovician) are a sequence of predominantly welded acid ash‐flow tuffs in the outlier centred on Yr Arddu (North Wales). The tuffs accumulated above a NNE‐trending fracture, the Yr Arddu Fracture, which had previously influenced sedimentation. The heterogeneity of the tuffs and their restricted development suggest that they represent proximal accumulations from small or suppressed (boiling‐over) eruption columns. The eruptions and emplacement developed, at least in the initial stages, in a submarine environment. Lithological, geochemical and palaeontological evidence indicates that the tuffs represent the earliest eruptive phase of the Lower Rhyolitic Tuff Formation. They were later intruded by comagmatic rhyolite domes, whose alignment reflects the continued influence of the early fracture.
The pre‐Caledonian Inishkea Division of northwest Co. Mayo, Ireland: Its geochemistry and probable stratigraphic position
Authors: Winchester J. A. , Max M. D.
Published: February 2007

The dominantly metasedimentary schists and gneisses of the Inishkea Division of the Erris Complex form a distinct rock group, structurally overlying the Grenvillian Annagh Division orthogneisses and underlying Dalradian metasediments, in the northwest County Mayo metamorphic inlier. A regression line for the Inishkea Division schists, defined by Rb–Sr whole rock analysis, suggests a metamorphic age of about 800 Ma, with a provenance age of about 1000–1300 Ma. The major and trace element chemistry is distinct from both the Annagh Division and Dalradian rocks, although sometimes similar to that of the Erris Group, and it suggests that the Inishkea Division originated as greywackes with associated intrusives. Local variations of the chemistry exist, but no systematic subdivision of the Division has been made. Amphibolite pods within the schists are metamorphosed and deformed tholeiite dykes, which are similar in chemistry to the younger metadolerites seen in the Annagh Division. While the geochemistry suggests that the Inishkea Division rocks are similar to both the Moine Assemblage and Grampian Group rocks of Scotland, the isotopic data suggest that they may have been deposited and then initially metamorphosed during the interval between the Grenville metamorphism of the Moine Assemblage and the onset of Dalradian and Erris Group deposition.
The nature and field relations of the Ordovician Maumtrasna Formation, County Mayo, Ireland
Authors: Graham John R.
Published: February 2007

The nature and field relationships of the Maumtrasna Formation of the Partry Mountains, Co. Mayo, show that the formation underlies the regionally mappable Glenummera Formation, which is of Llanvirn age, and it is laterally equivalent to the Rosroe and Derrylea Formations, also of Llanvirn age. The formation rests unconformably on two different volcanic domains, the basic volcanics of the Bohaun Volcanic Formation to the northwest (of unknown age) and the largely acidic volcanics and sediments of the Tourmakeady Volcanic succession to the southeast (Arenig). It is not the youngest formation in the Ordovician succession of the South Mayo Trough, as was previously thought.

This largely conglomeratic unit forms a coarsening upward sequence deposited on alluvial fans which were inundated by a marine transgression at the base of the Glenummera Formation. Clasts in the conglomerates are mainly of granite and porphyry with a minor metamorphic component. The source is interpreted as an arc rooted on a metamorphic basement which lay to the south and east. The suggestion that this area was present day Connemara finds little support. This area may expose some of the ‘hidden’ geology of the Midland Valley of Scotland.
The relationship between light hydrocarbons and carbonate petrology—a study from the Mendip Hills
Authors: Goodman S.
Published: February 2007

Anomalously 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

In 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

A 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

The 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

In 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

The 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

The 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

Sequence 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

The 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

Major 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

Abundant 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

Palaeomagnetic 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

The 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

A 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

The 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

Internal 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.
Ripple/dune to upper stage plane bed transition: Some observations from the ancient record
Authors: Chakraborty Chandan , Bose Pradip K.
Published: February 2007

In two Proterozoic sandstones, of the Indian shield cross‐stratification and cross‐lamination are observed to grade continuously into parallel‐laminations often bearing parting lineations. These are interpreted as having resulted from a gradual transition from ripple/dune to upper stage plane bed structures. During the transition the inclination of the cross‐strata diminishes and their shape changes from concave‐up to sigmoidal. The sigmoidal cross‐strata are characterized by well defined topsets, foresets and toesets and the topsets bear parting lineations. In the course of the transition sigmoidal cross‐strata may give way either to horizontal parallel‐lamination or inclined parallel‐lamination. In the former the toesets of the successive sigmoidal cross‐strata thicken and the thickness of the cross‐strata beyond the brink point (the junction between the topset and foreset) tends to become uniform until a plane‐bed state is reached and horizontal parallel‐laminations are formed. In the latter the topset of the successive sigmoidal cross‐strata increases in length at the expense of the foreset and toeset until the brink point ceases to exist so that only the topset laminations prevail and appear as inclined parallel‐laminations. These transitions presumably result from a gradual increase in flow intensity beyond the stability limits of ripples/dunes. The progressive morphological changes of the cross‐stratification over the transition are attributed to changing fallout patterns on the lee face of the bedforms in response to increasing flow intensity. Preservation of the records of such transitions suggests an abundant supply of sand grade sediments from suspension during the transition, shaping the sediment concentration profile over the bedforms and facilitating turbulence suppression. The variation in the pattern of transition from sigmoidal cross‐stratification to parallel‐lamination may be the result of different rates of sediment feed from the prevailing suspended sediment load in the two instances.
Loch lomond stadial glacier at Fan Hir, Mynydd Du (Brecon Beacons), South Wales: Critical evidence and palaeoclimatic implications
Authors: Shakesby Richard A. , Matthews John A.
Published: February 2007

The c. 1·2 km long, up to c. 25 m high ridge east of the almost north‐south aligned Fan Hir scarp, Mynydd Du, South Wales has been regarded as a remarkable protalus rampart formed in the Loch Lomond Stadial (c. 11–10000 years BP). New data are presented which indicate that it is a moraine. The main points supporting this glacigenic origin are: its curved plan form at the lower, southern end; its scale and the ample depth for snow to glacier ice transformation; the presence of subsidiary ridges interpreted as recessional moraines; the exceptional rate of rockwall retreat required if it were a protalus rampart; and, most importantly, the presence in the ridge of matrix‐supported abraded clasts, up to 20% of which are striated. Useful criteria for differentiating moraines and protalus ramparts are thereby proposed and a sound basis is provided for palaeoclimatic reconstruction. Palaeoclimatic inferences imply that the glacier owed its existence to the combined effect of a mean July temperature of c. 8·5°C and topographically enhanced accumulation, nearly half of which was from wind‐blown snow.
A rigid‐bodied Ediacaran Biota from Upper Cambrian strata in Co. Wexford, Eire
Authors: Crimes T. P. , Insole A. , Williams B. P. J.
Published: February 2007

Two typical representatives of the Ediacaran biota, Ediacaria booleyi n.sp. and Nimbia occlusa have been found in deep‐water turbidites within the Upper Cambrian Booley Bay Formation at Booley Bay in Co. Wexford, Eire. The examples of E. booleyi were transported over short distances by the turbidity currents and then impacted, in some instances at high angles, into the ocean floor muds where they formed moulds but, as their bodies decayed, these were filled by casting sand from the overlying turbidite. They preserved fine detail during transportation and impaction, thereby indicating the existence of a rigid body wall. The three‐dimensional nature of their preservation allows reconstruction, which shows that Ediacaria had a discoid form with prominent relief, particularly on its dorsal side, which was divided into three main concentric zones with thin radial features, more evident at the periphery. The ventral side had lower relief, with alternate areas of coarse and fine concentric markings and numerous fine radial lines, some also thicker at the periphery.

Nimbia occlusa are disc‐like bodies of low relief and occur in profusion on one sole. Some show a circular outline indicating that they were preserved flat on the bedding plane, but others occur as semicircular reliefs oriented in the palaeocurrent direction. This indicates that they too were moved by the turbidity current, but their abundance and excellent preservation indicate that transport distances were short. There is no evidence in either genus for the coelenterate characteristics of a mouth and a two‐layered body wall enclosing a single cavity. This, and the evidence for a rigid outer wall, adds to recent doubt on the concept of the world‐wide Ediacaran fauna as dominated by soft‐bodied coelenterates.
Revision of the Carboniferous cystoporate bryozoan Fistulipora incrustans (Phillips, 1836), with remarks on the type species of Fistulipora M'Coy, 1849
Authors: Bancroft Adrian J. , Jackson Patrick N. Wyse
Published: February 2007

The type species of the Palaeozoic cystoporate bryozoan genusFistuliporaM'Coy, 1849 is redescribed.Fistulipora minorM'Coy, 1849 is the type species, and was the first species described under the genusFistulipora.Quantitative assessment of type and figured specimens ofCalamopora incrustansPhillips, 1836 andF. minorhas shown them to fall within the range of morphological variation exhibited by abundant comparative material collected at several horizons and they are referable to one morphologically variable taxon.F. minoris the junior subjective synonym ofC. incrustansand the form can be quoted asF. minorM'Coy, 1849 =C. incrustansPhillips, 1836 with a valid name ofF. incrustans(Phillips, 1836). However, this does not alter the name of the type species, which isF. minorM'Coy, 1849. The type specimen ofBerenicea megastomaM'Coy, 1844 has also been examined, and this form is also conspecific withF. minorM'Coy, 1849 =C. incrustansPhillips, 1836. Examination of the type specimen ofF. majorM'Coy (1849) has shown it to be referable to the tabulate coral genusChaetetes.A lectotype and paralectotypes are designated forF. minorand the status of the type specimens ofF. incrustansis clarified.
Petrographic evidence for diachronous metamorphism of the Skaiti Supergroup, Köli Nappe Complex, Arctic Scandinavian Caledonides
Authors: Westhead R. K. , Boyle A. P.
Published: February 2007

The Skaiti Supergroup is the uppermost major tectono‐stratigraphic unit of the Koli Nappe Complex, which comprises Precambrian to Lower Palaeozoic rocks immediately north of the Arctic Circle in Scandinavia. This complex was derived from within the lapetus Ocean and emplaced during the Scandian phase of the Caledonian Orogeny. Petrographic evidence along a hinterland to foreland traverse of the Skaiti Supergroup demonstrates that garnet, staurolite and kyanite porphyroblastesis was diachronous with respect to fabric development, becoming later towards the hinterland. The hinterland rocks experienced two discrete phases of heating, whereas the foreland rocks only experienced one. These observations are consistent with a recent tectonic model for diachronous burial and exhumation of the Koli Nappe Complex during emplacement.
Inverted metamorphic zonation in a basement‐derived nappe sequence, eastern margin of the Bohemian Massif
Authors: Štípská Pavla , Schulmann Karel
Published: February 2007

Inverted metamorphic zonation is developed in the basement‐derived nappe sequence at the eastern margin of the Bohemian Massif. Mineral reactions and geothermometry reveal an increase in temperature from 580–600°C to 650°C and an increase in pressure from 6 to 10 kbar from the bottom to the top of the nappe pile. Kinematic data and syntectonic crystallization of minerals indicate that the peak conditions were diachronously attained during a slow oblique underthrusting of the Brunovistulian basement. Geochronological data reveal about 20 Ma between granulite facies metamorphism of the upper plate and mineral cooling ages in lower plate, precluding perturbation of the geotherm by underthrusting. A model is suggested showing a progressive break‐up of the deepest part of the underthrust Brunovistulicum and subsequent migration of the intraplate to the base of the basement‐derived thrust sheet. The uplift of this unit led to its decompression while the rest of the basement was subject to continuous underthrusting. The inverted metamorphic zonation within a single unit is explained using a model of heterogeneous deformation of upward transported units and passive inversion of initially subhorizontal isograds.
Stabilities of negative correlations between blood oxygen level‐dependent signals associated with sensory and motor cortices
Authors: Tian Lixia , Jiang Tianzi , Liang Meng , Li Xiaobo , He Yong , Wang Kun , Cao Bingli , Jiang Tao
Published: February 2007

Compared with positive correlations, negative correlations of blood oxygen level‐dependent (BOLD) signals (NCOBSs) have been much less studied. In most related studies, the NCOBSs have been accepted as stable without further consideration. To investigate the stabilities of NCOBSs associated with the auditory, motor, and visual cortices, we evaluated the negative correlation maps of each brain region under different “task‐backgrounds” within the same subject‐group, as well as within different subject‐groups during a conscious resting state. These “task‐backgrounds” refer to tasks not expected to activate the specific ROI under consideration and are in some sense analogous to “resting states.” We found that the negative correlation maps of the motor and visual cortices were quite variable between either different task‐backgrounds or different subject‐groups, whereas those of the auditory cortex exhibited some similarities. These results indicate that the NCOBSs associated with the motor and visual cortices were unstable both under task‐backgrounds and during the conscious resting state. The auditory cortex tended to have stable NCOBSs during these “resting states” (but scanner noise could make the auditory cortex “less resting”). This study highlights the importance of paying attention to the influence of the stabilities of NCOBSs in related studies and establishes the need for further studies on NCOBSs. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
Neural correlates of verbal feedback processing: An fMRI study employing overt speech
Authors: Christoffels Ingrid K. , Formisano Elia , Schiller Niels O.
Published: February 2007

Speakers use external auditory feedback to monitor their own speech. Feedback distortion has been found to increase activity in the superior temporal areas. Using fMRI, the present study investigates the neural correlates of processing verbal feedback without distortion. In a blocked design, the following conditions were presented: (1) overt picture‐naming, (2) overt picture‐naming while pink noise was presented to mask external feedback, (3) covert picture‐naming, (4) listening to the picture names (previously recorded from participants' own voices), and (5) listening to pink noise. The results show that auditory feedback processing involves a network of different areas related to general performance monitoring and speech‐motor control. These include the cingulate cortex and the bilateral insula, supplementary motor area, bilateral motor areas, cerebellum, thalamus and basal ganglia. Our findings suggest that the anterior cingulate cortex, which is often implicated in error‐processing and conflict‐monitoring, is also engaged in ongoing speech monitoring. Furthermore, in the superior temporal gyrus, we found a reduced response to speaking under normal feedback conditions. This finding is interpreted in the framework of a forward model according to which, during speech production, the sensory consequence of the speech‐motor act is predicted to attenuate the sensitivity of the auditory cortex. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
Prefrontal cortex activity is reduced in gambling and nongambling substance users during decision‐making
Authors: Tanabe Jody , Thompson Laetitia , Claus Eric , Dalwani Manish , Hutchison Kent , Banich Marie T.
Published: February 2007

Objective: Poor decision‐making is a hallmark of addiction, whether to substances or activities. Performance on a widely used test of decision‐making, the Iowa Gambling Task (IGT), can discriminate controls from persons with ventral medial frontal lesions, substance‐dependence, and pathological gambling. Positron emission tomography (PET) studies indicate that substance‐dependent individuals show altered prefrontal activity on the task. Here we adapted the IGT to an fMRI setting to test the hypothesis that defects in ventral medial and prefrontal processing are associated with impaired decisions that involve risk but may differ depending on whether substance dependence is comorbid with gambling problems. Method: 18 controls, 14 substance‐dependent individuals (SD), and 16 SD with gambling problems (SDPG) underwent fMRI while performing a modified version of the IGT. Result: Group differences were observed in ventral medial frontal, right frontopolar, and superior frontal cortex during decision‐making. Controls showed the greatest activity, followed by SDPG, followed by SD. Conclusion: Our results support a hypothesis that defects in ventral medial frontal processing lead to impaired decisions that involve risk. Reductions in right prefrontal activity during decision‐making appear to be modulated by the presence of gambling problems and may reflect impaired working memory, stimulus reward valuation, or cue reactivity in substance‐dependent individuals. Hum Brain Mapp, 2007. © 2007 Wiley‐Liss, Inc.