bluuebunny/crossref_metadata_2025 huggingface dataset:
Basement massifs in the Appalachians: their role in deformation during the Appalachian Orogenies
Authors: Hatcher Robert D.
Published: July 2010

Basement is constituted of rocks which belong to a previous orogenic cycle which have been reactivated and incorporated into a younger cycle. Basement massifs may be classified according to their relative position in an orogen as external or internal massifs. They may also be categorized according to their role in deformation, as thrust‐related, fold‐related and composite massifs.

All Appalachian external massifs were transported following their removal from the overridden edge of the ancient North American continental margin. Most of the internal massifs are also probably transported, but several (Pine Mountain and Sauratown Mountains) may be present as windows exposing parautochthonous basement beneath the main thrust sheet. The latter reside immediately west of the low (west) to high (east) gravity gradient which probably outlines the old edge of Grenvillian crust. Reactivated crustal material generated during early Palaeozoic orogeny plays the same mechanical role in reactivation as basement from the previous Grenville cycle. The domes of the Bronson Hill anticlinorium cored with Ordovician or older gneisses illustrate this behaviour.

Basement (Grenville) massifs are distributed throughout the Appalachians as a belt of external massifs (Blue Ridge, Reading Prong, Hudson and Berkshire Highlands, Green Mountains, and Long Range Mountains) along the western edge of the crystalline metamorphic core. Additionally, internal massifs are also present (Pine Mountain belt, Tallulah Falls and Toxaway domes, Sauratown Mountains anticlinorium, State Farm gneiss dome, Baltimore Gneiss domes, Mine Ridge anticline, and Chain Lakes massif).

Basement internal massifs probably served to localize thrusts by causing them to ramp over and around the massifs. Their antiformal shape may in part be as much related to thrust mechanics as to folding.
Basement‐cover relations in the Appalachian fold and thrust belt
Authors: Thomas William A.
Published: July 2010

The external massifs along the Appalachian orogen include Precambrian basement rocks with attached cover. To the northwest (cratonward), in the Appalachian foreland fold and thrust belt, Palaeozoic sedimentary rocks, but no basement rocks, are exposed; that belt was the subject of the classic debate about thin‐skinned (deformed cover rocks detached from undeformed basement) and thick‐skinned (basement deformed with attached cover) structural styles. Presently available data indicate detached cover rocks and thin‐skinned style in the fold and thrust belt: large‐scale thrusting occurred late in the orogenic history. In the external basement massifs, late Precambrian graben‐fill sedimentary and volcanic rocks indicate early basement faults; and within the craton, steep basement faults bound graben blocks of Cambrian age. Distribution of known basement faults suggests that basement rocks beneath the fold and thrust belt may also be faulted. Local episodic synsedimentary structural movement through much of the Palaeozoic is documented by stratigraphy in the fold and thrust belt. Axes of early synsedimentary structures are approximately coincident with axes of late folds and thrust fault ramps, but stratigraphic data show that magnitude of the early structures was much less than that of the late structures. These relations suggest the interpretation that early low‐magnitude structures formed in cover rocks over basement faults and that the early structures, or the basement faults, significantly influenced the geometry of later detachment structures during large‐scale horizontal translation.
Observations and speculations on the northeast Towy ‘axis’, mid‐Wales
Authors: James D. M. D.
Published: July 2010

Late Ashgill and Llandovery sedimentation across the Towy ‘axis’ southeast of Rhayader is interpreted within the context of the rapid southeasterly thickening of the upper portion of the Ashgill best demonstrable in the Chwefru valley. This thickening sequence overlies deep‐water middle‐fan arenites and is interpreted as a northwest prograding shelf/slope association. The slope eventually became non‐depositional and was onlapped by the basinal facies of the Llandovery during relative sea‐level rise. The non‐depositional slope and associated major slump‐scars at the shelf‐edge explain many of the non‐sequences‐ in the region previously ascribed to erosion related to episodes of tectonism. The regional strain history is thus simplified.
A Pleistocene succession from beneath Chelford Sands at Oakwood Quarry, Chelford, Cheshire
Authors: Worsley P. , Coope G. R. , Good T. R. , Holyoak D. T. , Robinson J. E.
Published: July 2010

A thin sequence of in situ fossiliferous gravels and silts overlain by a glacigenic bed is described from a temporary exposure in a working silica sand quarry. The sequence directly overlies unweathered Mercia Mudstone. Locally the bedrock surface forms a shallow palaeovalley some 15 m deep and almost 1 km wide. The sequence in question lies close to the valley axis. The silts, pollen, plant macrofossils, Mollusca, Coleoptera, and Ostracoda assemblages each suggest a similar environment of sedimentation: a shallow pool within a treeless open landscape. Much of the bedrock within the working quarry appears to be draped by the Oakwood till and this unit is co‐extensive with the glacigenic sediments over the silts and gravels. In parts at least, the till has been subject to redeposition and its upper surface has scattered ventifacts. Above this wind‐deflation horizon lies the Chelford Sands Formation, in the middle of which is the Chelford Interstadial stratotype, the Farm Wood member. The biota preserved in the gravels and silts suggest a stadial prior to the Early Devensian Chelford Interstadial. This is the first unambiguous stratigraphic evidence from Cheshire of a glacial event antedating the Chelford Interstadial.
Discovery of Arundian and Holkerian faunas from a Dinantian platform succession in North Wales
Authors: Somerville Ian D. , Strank Angela R. E.
Published: July 2010

For the first time Arundian and Holkerian faunas have been recognized from the lower part of the Dinantian succession in North Wales. These limestones and sandstones, hitherto regarded as Asbian, have a macrofauna and microfauna confirming their older age, and this discovery' has necessitated a revision of the palaeogeography in the North Wales region. Biostratigraphical correlations have been made with contemporaneous platform successions in the Central, Northern, and Southwest Provinces of Britain. A new genus and species of foraminifer, Groessensella moldensis, is described.
A re‐examination of the type Arenig Series
Authors: Zalasiewicz J. A.
Published: July 2010

The stratotypc of the Arenig Series (Ordovician System) and its boundaries are critically re‐examined. The lithostratigraphy and biostratigraphy of the Tremadoc, Arenig, and Llanvirn age rocks at Arenig Fawr, North Wales that were constructed by Feamsides in 1905 are amended. The Arenig Series at Arenig is represented by the Camedd Iago Formation which was established by Lynas (1973) in the Migneint area. Examination of the sparse graptolite faunas indicates that the type Arenig Series is incomplete, only the extensus Zone having been recognized with certainty. There is a possible unconformity at the base and a probable unconformity at the top, and on present knowledge the succession cannot be correlated precisely with what are considered to be Arenig sequences elsewhere. It therefore may prove necessary to redefine the Arenig Series at a more useful type section. It is suggested that the Carmarthen district may provide a suitable stratotype.
Fluvial to marine transition in the Ordovician of Ireland–A humid‐region fan‐delta?
Authors: Pudsey C. J.
Published: July 2010

The Mweelrea Group (Llanvirnian) in the South Mayo Inlier, western Ireland, consists mainly of coarse shallow‐water sandstones with minor slates, cobble conglomerates, and ignimbrite tuffs. The Glenummera Formation at the base (up to 600 m), dominantly well‐cleaved slates with some slump features, was deposited in a slope to deep marine shelf environment. A coarsening upward sequence at its top reflects the interaction of fluvial and marine processes, coarse clastic sediments having prograded from the southeast. The rest of the Mweelrea Group (2100 m in the northwest) is dominated by coarse trough cross‐bedded sandstone with little evidence for channelling. Three lenticular marine slates (Glendavock, Uggool, and Glenconnelly Formations), up to 200 m thick, wedge out to the southeast. A humid alluvial fan‐fan‐delta model can explain many features of the Mweelrea Group. Fans built out to the northwest into a relatively small basin with negligible tides and moderate wave energy. Marginal sediments were reworked by waves, occasional storms, and a burrowing fauna.
The stratigraphy and sedimentology of the Ordovician Partry Group, southeastern Murrisk, Ireland
Authors: Williams D. M.
Published: July 2010

The uppermost part of the Ordovician succession in southeastern Murrisk, western Ireland, consists of coarse‐grained sedimentary rocks and tuffs, the Partry Group, hitherto subdivided into the Mweelrea Formation, unconformably overlain by the Maumtrasna Formation. The age of the lower part of the succession is late Llanvirn whilst that of the upper part is unknown. Evidence is presented to show that the two formations are lateral equivalents. Consequently the Mweelrea Formation is redefined and the Maumtrasna Formation becomes redundant. The revision of the stratigraphy enables a coherent sedimentological model for the group to be proposed. The sediments of the Mweelrea Formation were deposited on alluvial fans and distally‐equivalent alluvial plains and delta fans. The direction of sediment transport was towards the north and northwest.
The recognition of the Asbian/Brigantian boundary fauna and marker horizons in the Dinantian of North Wales
Authors: Somerville Ian D. , Strank Angela R. E.
Published: July 2010

For the first time the stratigraphically important brachiopod Davidsonina septosa (Phillips) has been located in thickly bedded pale grey, late Asbian limestones in North Wales. Above these limestones are thinly bedded dark grey Brigantian limestones, which have yielded a rich and diverse coral‐brachiopod fauna, including Lonsdaleia floriformis (Martin). The Girvanella Nodular Bed is recorded for the first time in this region, some distance above the base of the Brigantian. The boundary between the two major lithofacies is marked by a prominent palaeokarstic surface and coincides with a significant faunal change, both in the macrofauna and microfauna that serves to identify the boundary between the Asbian and Brigantian Stages. The discovery within late Dinantian successions of certain diagnostic corals, brachiopods, and algae outside their accepted restricted stratigraphical ranges, casts doubt on their reliable use as Asbian or Brigantian zone fossils.
Lower Palaeozoic lithostratigraphical classification in the English Lake District
Authors: Moseley F.
Published: July 2010

In the English Lake District lithostratigraphical classification has not kept pace with either the international and national codes or the code of the Geological Society (Holland et al. 1978). Probelms arise, firstly, from acceptance by several of those working in the area, of terms used in by‐gone days, such as ‘Borrowdale Volcanic Series’, and secondly, and more importantly, because individuals have specialized on certain parts of the sequence (the Skiddaw Slates, the Coniston Limestone, etc.), and have erected classifications for these rocks without reference to other parts of the succession. These classifications are examined and modified in such a way that the lithostratigraphical subdivisions are consistent for the whole of the Lower Palaeozoic sequence of the Lake District, and also relate to the international code as it is applied in other regions. The basic Lake District stratigraphical terminology of the last century is, however, retained in all its essentials.
Peritidal carbonate facies models: A review
Authors: Wright V. P.
Published: July 2010

Existing facies models for peritidal carbonates are limited in number and do not reflect the wide spectrum of possible types. The major depositional processes in peritidal carbonate environments are reviewed in order to stress the complex nature of the systems. The tidal channel model is critically discussed and it is suggested that channel deposits may be of minor importance in typical shoaling‐up sequences. The possible causes of multiple asymmetrical sequences are reviewed.
Production of multi‐décollement folding by pressure release in the formation of a microbreccia at Lough Doon, Donegal, eire
Authors: Holder M. T.
Published: July 2010

An unusual matrix‐supported microbreccia of Caledonian age is described from the Dalradian rocks of Donegal. Field and textural relationships indicate that the breccia formed ‘in situ’ by a non‐dilational mechanism during regional deformation. The presence of breccia veins of low competancy during this deformation caused multi‐décollement folds to be formed adjacent to the breccias. A cyclical mechanism of formation of these breccias is proposed in which fluctuations in the overpressuring of pore fluids escaping from an adjacent crystallizing appinite mass caused periodic excursions from ductile to brittle deformation during the regional folding.
Generic identification of fragmentary Quaternary molluscs by amino acid chromatography: A tool for Quaternary and palaeontological research
Authors: Andrews J. T. , Miller G. H. , Davies D. C. , Davies K. H.
Published: July 2010

The amino acid signature of fourteen genera of Mollusca, both Bivalvia and Gastropoda, was determined on over 300 individual valves. Examination of eight specific sets of amino acid ratios (for example: aspartic acid/glutamic acid, leucine/valine) indicates that these 14 genera (Patella, Littorina, Nucella, Buccinum, Turritella, Macoma, Scrobicularia, Mytilus, Cerastoderma, Arctica, Gtycymeris, Venus, Mya, and Hiatelld) can be distinguished one from another with a high degree of certainty.

Discrimination between genera can be based on quantitative assessment of the probability of an individual analysis belonging to a specific genus. We conclude that the amino acid signature is sufficiently distinct that small shell fragments can be assigned to a genus on the basis of the amino acid chromatography. In some instances, for example Littorina, it may even be possible to identify fragments to specific species.
The Ludlow‐Downton transition at Kington, Herefordshire
Authors: Holland C. H. , Williams E. M.
Published: July 2010

Biostratigraphy and lithostratigraphy of some exposures of upper Ludlow and lower Downton rocks near Kington, Herefordshire are described in detail. Temporary exposures created during the construction of the new Kington by‐pass are particularly informative. One small exposure of Lower Whitcliffe Formation is recorded. The Upper Whitcliffe Formation is well displayed in characteristically fossiliferous shelly siltstones. The Downton succession begins with the Ludlow Bone Bed Member. This and the succeeding Platyschisma Shale Member complete the local development of the Downton Castle Sandstone Formation.
Regional variations in cleavage and fold development in North Wales
Authors: Campbell S. D. G. , Reedman A. J. , Howells M. F.
Published: July 2010

The arcuate pattern of the main Caledonian cleavage and associated fold axial plane traces in North Wales is due partly to NW‐SE compression with tectonic transport to the southeast against the concealed crop of the Tan y grisiau Microgranite. Low‐angle cleavage close to the microgranite is shown to be a local variant of the regional cleavage formed during the main deformation and not an earlier phase as previously supposed. Transcurrent movements along several major fault systems are also related to compression around the microgranite and the Harlech Dome block.
The intrusion and deformation of Tertiary minor sheet intrusions, west Suardal, Isle of Skye, Scotland
Authors: Nicholson R
Published: July 2010

The arcuate Broadford anticline of south‐central Skye folds a sequence of strata ranging in age from late Precambrian to Jurassic. The Ordovician carbonate rocks of the core of the anticline are strongly extended parallel to bedding and deformation at some localities reaches up into unconformable Mesozoic strata. Three classes of Tertiary minor intrusion are recognized in the deformed sediments. The younger two are post‐kinematic. The effect of deformation on discordant sheets of the oldest class is obvious, as they are folded. It now seems, however, that the boudins previously reported (Nicholson 1970; Longman and Coward 1979) are sections through finger‐like igneous bodies (Farmin 1941; Pollard et al. 1975). Stiff in relation to the carbonate country rock, the latter retained igneous textures and chilled margins when deformed. Deformation probably took place as the main period of plateau‐lava eruption ended and the succeeding phase of shield volcanoes and major intrusive centres began. As deformation is restricted to the core of an arcuate fold forming part of a volcanic complex, it may speculatively be suggested that the deformed rocks lie above an arcuate diapir, formed in an acid magma body subjected to volcanic load.
The brachiopod fauna of the Meadfoot Group (Lower Devonian) of the Torbay area, south Devon
Authors: Evans K. M.
Published: July 2010

The lithology and sedimentology of the Meadfoot Group around Torbay are briefly discussed. The brachiopod fauna is tabulated, with ranges, and is considered to indicate an Emsian age. The fauna and environment of deposition of the Meadfoot facies (Lower‐Upper Emsian) and the Staddon facies (Upper Emsian) are discussed and are interpreted as representing Outer Shelf and Inner Shelf positions respectively.
Facies variation in Waulsortian buildups. Part 2; Mid‐Dinantian buildups from Europe and North America
Authors: Lees Alan , Miller John
Published: July 2010

Using detailed petrographic analysis and a new method of handling similarity coefficients, samples from over 30 Mid‐Dinantian (Upper Tournaisian‐Lower Viséan) carbonate buildups from Europe and North America are compared with the Waulsortian facies of Belgium. The same component types are present and they bear very similar relationships to. one another. This is very significant because the assemblages of components in Belgium have recently been interpreted in terms of water depth (Lees et al. 1985).

Four Waulsortian Phases are recognized, corresponding to the Belgian depth‐related assemblages. They represent growth in a range of marine environments from fairly deep, aphotic (probably more than 300 m) through to the photic zone (less than 120 m).

Logging and mapping of phases allows growth patterns of individual buildups and buildup complexes to be interpreted as products of changing depositional environments. The very existence of the phases provides new information on the origin of the buildups. It also reveals that there was a fundamental growth mechanism independent of the preserved biota.
The deep structure of Derbyshire
Authors: Smith K. , Smith N. J. P. , Holliday D. W.
Published: July 2010

Pre‐Carboniferous basement beneath Derbyshire is disposed in two southwest‐dipping tilt blocks (Eyam and Woo Dale Blocks), which are separated by a major north‐dipping growth fault (the Bakewell Fault). The surface expression of the Bakewell Fault is largely concealed by late Dinantian carbonate shelf sediments, but its position and trend, which can be inferred from borehole and geophysical evidence, have exerted a control upon mineralization and volcanism in Derbyshire. During the Holkerian, the Bakewell Fault acted as the axis of a broad anticlinal fold or drape structure, which subsequently influenced the position of the overlying Asbian carbonate shelf. Tilt blocks are arranged symmetrically beneath the southern Pennine Basin, with north‐dipping blocks, such as the Askrigg Block, at the northern margin mirrored by south‐dipping blocks beneath Derbyshire in the south.
The Dinantian biostratigraphy of a deep borehold near Eyam, Derbyshire
Authors: Strank Angela Ft E.
Published: July 2010

Detailed micropalaeontological analysis of the Eyam Borehole is presented. Dinantian strata of Upper Tournaisian to ‘middle’ Brigantian age have been recognized lying unconformably on top of Ordovi‐cian (?Llanvirn) basement beds (Dunham 1973). The early Tournaisian and late Brigantian beds are missing probably due to non deposition and erosion respectively. Throughout the Dinantian a shallow shelf environment is represented by a thick series of anhydrites and dolomites in the Upper Tournaisian. The new name Middleton Dale Anhydrite Series is proposed for these lowest Dinantian beds. The chronostratigraphy erected is compared with that outlined for Eyam by Dunham (1973) and for the Woo Dale Borehole by Strank (in press).
Tectonic deformation of a channel sandstone
Authors: Tringham M. E.
Published: July 2010

An investigation has been made of a structural complex in southwest Wales. The complex comprises a zone of folds and faults within Upper Carboniferous rocks of the Variscan fold belt, interpreted to have formed by tectonic deformation of a large channel sandstone. Sedimentary features include basal and internal erosion surfaces, an onlapping channel fill, lens‐shaped beds of mudstone with slumped layers, and discontinuous conglomerate and coal beds. These features strongly influenced ensuing tectonism, with the channel axis now coincident with a composite anticline. Some bedding discontinuities acted as surfaces of decollement, and lens‐shaped beds were folded disharmonically. This example will provide an analogy for use in other deformed sedimentary terrains, where channels may occur.

Acknowledgements. I wish to thank Drs M. C. Cooper, R. M. Tucker and B. P.J. Williams for their valuable comments on the manuscript. I also acknowledge receipt of a NERC studentship held at the University of Bristol, supervised by Dr P. L. Hancock.
Non‐axial planar cleavage and Caledonian sinistral transpression in eastern Ireland
Authors: Murphy Finbarr C.
Published: July 2010

Transected F1 fold structures in eastern Ireland are associated with subhorizontal stretching in the S1, cleavage whereas axial planar cleavage contains a vertical elongation direction. This suggests that the non‐axial planar cleavage was influenced by a distributed strike‐slip ductile shear.

A major NE‐SW trending F1 syncline is described in which the minor F1 folds show systematic variations in cleavage transection parameters. On the steep limb of the major syncline the cleavage transects the minor F1 folds in a consistently clockwise sense, whereas on the normal limb anticlockwise transected folds are seen. Axial planar cleavage occurs at the core of the major syncline.

Fold profile analysis indicates that the buckling of the layers began before the initiation of the cleavage. Open, parallel folds at the major synclinal hinge zone are progressively ‘flattened’ on the steep limb towards a major D1 sinistral transcurrent fault. The angular transection, A, attains a maximum of 15° clockwise which diminishes to <5° at higher strains adjacent to the major fault. Incremental fibre growth in pressure shadows show a two‐stage tectonic strain superposition of vertical pure shear followed by sinistral transcurrent simple shear during the development of the clockwise transecting cleavage. Anticlockwise transected folds were influenced by local dextral strike‐slip on the southern margins of a rigid terrane. As a regional feature, the clockwise transection is explained by a sinistral transpressive deformation of end‐Silurian age.
A peridotitic komatiite from the Dalradian of Shetland
Authors: Flinn Derek , Moffat D. T.
Published: July 2010

Komatiite lavas occur in the Dunrossness Spilitic Group in southeast Shetland in the Cunningsburgh area. This metavolcanic group is the easternmost member of the East Mainland Succession of Shetland and probably the youngest. It overlies a thick succession of deep‐water metasediments and metavolcanic rocks probably forming part of an extensional basin and has been correlated with a part of the upper Dalradian of Scotland. Komatiites are not common in rock sequences as young as this. Their eruption is thought to require tectonic and thermal conditions which have been unusual since Archean times. Such conditions could arise when the crust beneath an extensional basin splits to form a constructive margin.
Structure, petrology and geochemistry of the Abu Dom alkaline ring‐complex, Bayuda Desert, Sudan
Authors: O'Halloran D. A.
Published: July 2010

The Abu Dom complex is one of a cluster of Younger Granite ring‐complexes piercing the Proterozoic gneisses of the Bayuda Desert of Sudan. Intrusive rocks predominate and range from early metaluminous syenites to later peralkaline syenites and granites. They are disposed as ring‐dykes, nested intrusions, and cone‐sheet swarms. Field evidence and geochemical variation indicate that the peralkaline rocks evolved from a metaluminous syenitic parent magma as a result of high‐level fractionation. The suite carries a clear within‐plate signature exemplified by marked enrichments in HFS elements such as Zr and Nb.
Pre‐Caledonian basement in Ireland and its cover relationships
Authors: Max M. D. , Long C. B.
Published: July 2010

Pre‐Caledonian basement is exposed in three areas within the Irish orthotectonic Caledonides: 1. In northwest County Mayo the Erris Complex comprises the Annagh Division, which is largely Grenvillian but includes older gneisses, and the Inishkea Division, which is probably equivalent to the older Moines of Scotland. 2. In the northeast Ox Mountains, Rosses Point and Lough Derg inliers there is a granulite fades, dominantly metasedimentary basement which is probably late Grenville in age. 3. Laxfordian and probably older gneisses are seen in the Inishtrahull Platform northeast of Malin Head, County Donegal.

In addition, some gneisses within the belt of ‘Connemara migmatites’ in south Connemara may be fragments of allochthonous basement and some high grade metamorphic rocks in the Tyrone Central inlier have been referred to as pre‐Caledonian basement, but there is at present no conclusive support for these suggestions. The Ox Mountains succession seen in the Clew Bay region and the southwest and central Ox Mountains is probably not pre‐Caledonian basement.

Basement in the paratectonic Caledonides is confined to the Cadomian and possibly pre‐Cadomian Rosslare Complex (older than 625 Ma) and the nearby late Precambrian (to early Cambrian ?) Cuilenstown Formation in southeast County Wexford. In addition, an unseen block of basement defined by magnetics immediately to the north of the Dingle peninsula of County Kerry is probably of Rosslare Complex affinity. Granulite facies xenoiiths recovered from volcanic rocks of Carboniferous age about 70 km to the west of Dublin, indicate the character of basement there, though its age is not proven.

All contacts between basement and Lower Palaeozoic Caledonian cover in the orthotectonic Caledonides are synmetamorphic slide zones and faults and in the paratectonic Caledonides the contacts are either faults, which are often rooted in older mylonites, or are unexposed and presumed to be major structural breaks.
Heterogeneous deformation and mylonitization of a granulite complex, jotun‐valdres nappe complex, Central South Norway
Authors: Koestler Andreas G.
Published: July 2010

The Helgedal Zone is the Caledonian, heterogeneously deformed base of the Jotun Complex, within the Jotun‐Valdres Nappe Complex (Sognefjell, South Norway). It consists of an anastomosing system of shear zones isolating lozengeshaped lenses of less deformed rocks. Structural and geometrical features are described to define the type of deformation and to evaluate the tectonic significance of this zone. Granulitic gabbros and pegmatitic dykes are deformed together in the highly strained mylonitic zones. Microtextural investigations indicate that the quantitative relation between mafic and felsic minerals and the content of quartz determine the different behaviour of the two rock types during deformation.
Sediments in the estuarine environment of the tigris/euphrates delta; Iraq; Arabian Gulf
Authors: Darmoian S. A. , Lindqvist Kristian
Published: July 2010

Studies on surface water characters of the estuarine environment of Iraq, northwestern Arabian Gulf, define three subdivisions of salinity: oligohaline, polyhaline, and euhaline. Textural analysis reveals that surface sediments covering the bottom are composed of six distinct classes: silty clay, clayey silt, sand‐silt‐clays, clayey sand, silty sand and sand. Five physiographic subdivisions are identified and described fluvial‐estuarine, tidal mud flats (subtidal flat, lower intertidal flat, upper intertidal flat, supratidal flat), sand bars, Abdallah‐Shetana channel and submerged estuarine distributary channel and bar systems.

The content of organic matter in the sediments ranges from 0.24‐3.69 per cent by weight. High values were recorded from the Abdallah‐Shetana channel while lower values are confined to sand bars and submerged estuarine distributary channel and bar systems.

Carbonates, quartz, feldspar, and halite are the main mineral constituents of the non‐clay grade sediments; carbonates are present mainly as low‐magnesium calcite followed by dolomite and high‐magnesium calcite. Aragonite is present only in trace amounts. Both detrital and biogenic sources are suggested for low‐magnesium calcite. A detrital source for dolomite and a biogenic source for high‐magnesium calcite and aragonite are proposed.
Evidence for dextral oblique‐slip faulting in the shelve ordovician inlier, welsh borderland: Implications for the South British Caledonies
Authors: Lynas B. D. T.
Published: July 2010

Recent work in the Shelve Ordovician Inlier has produced a variety of evidence for a period of deformation dominated by a braided system of dextral oblique‐slip faults of pre‐upper Llandovery age. Displacement amounts along individual fault strands are generally less than 2 km, but the aggregate displacement across the whole Inlier up to and including the Pontesford‐Linley Fault, must have been much greater. The fault structures found in other parts of Wales are compared to those of the Shelve Inlier, and it is concluded that this style of faulting was of importance in Wales, though it was mostly of pre‐Silurian age. The significance of the fault systems in terms of the late Precambrian to early Caledonian structural framework of Southern Britain is discussed with reference to examples from other parts of the world.
Sedimentary environments and facies of the subtropical mgeni estuary, Southeast Africa
Authors: Cooper J. A. G.
Published: July 2010

The Mgeni Estuary is situated on the subtropical, mainly microtidal Natal coast. Modern sedimentary environments in the estuary comprise two groups. Barrier‐associated environments include inlet channel, inlet beachface, tidal delta, washover fans, transverse intertidal bars and aeolian dunes. Estuarine environments include subtidal channels, interidal bars, back‐barrier lagoon, tidal creek, tidal creek side‐attached bars, creek mouth bar, mangrove fringe and supratidal mudflats. Each sedimentary facies is described in terms of grain‐size, sedimentary structures, and sedimentary processes. The distinctive flora and fauna play an important role in facies recognition. Vertical sequences produced by infilling of the estuary and subsequent coastal erosion are discussed. The facies are considered sufficiently distinct to warrant recognition in the geological record.
Processes of alluvial fan sedimentation, basal rozel conglomerate formation, la têcte des hougues, Jersey, Channel Islands
Authors: Went D. J. , Andrews M. J. , Williams B. P. J.
Published: July 2010

The Rozel Conglomerate Formation, a coarse alluvial fan deposit, overlies the Bouley Rhyolite Formation beneath the headland called La Tete des Hougues, on the north coast of Jersey, Channel Islands. Here the rhyolites form an exhumed palaeotopography which in places is smoothly, but irregularly, eroded. Locally however, there is preservation of a deep Lower Palaeozoic weathering profile. Breccia is preserved spalled from these weathered profiles as a fossil scree deposit, which has subsequently been hydraulically reworked in a palaeotopographic low.

Overlying the breccia is a prograding succession of alluvial fan sediments. A 4m thick, upwards‐coarsening sequence of silty sandstones and fine pebble conglomerates is succeeded by the incision of a 3m deep channel. This is overlain by a 28m thick, upwards‐fining sequence of coarse debris flow and streamflood conglomerates. The lower unit is interpreted as a prograding fan sector of reworked fan material, whilst the upper unit is thought to reflect the avulsive initiation and gradual abandonment of a fan lobe sourced from a northern hinterland.
Lithostratigraphy and structure of the old red sandstone of the Northern Dingle Peninsula, Co. Kerry, Southwest Ireland
Authors: Todd S. P. , Williams B. P. J. , Hancock P. L.
Published: July 2010

The lower part of the Old Red Sandstone in the Dingle Penisula has been previously assigned to one lithostratigraphic group (Dingle Group) despite marked variations in sedimentary facies. However the apparently oldest non‐marine sequence in the northwest of the peninsula has sedimentary and lithological attributes that contrast strongly with those of the late Silurian‐early Devonian Dingle Group to the south. This northern sequence, here renamed the Smerwick Group, evolved independently of the Dingle Group in a separate basin of deposition. Field relationships between the two groups in the north of the peninsula are interpreted as indicating that the Smerwick Group overlies, with angular unconformity, a normal Dingle Group succession. Similarly, it is argued that the Smerwick Group overlies, with angular unconformity, the Dingle Group in the northwest of the peninsula, but there the Dingle Group is attenuated, represented only by a conglomerate unit some 10 m thick. In the absence of biostratigraphic evidence the age of the Smerwick Group is poorly constrained. Nevertheless, we propose a tectonic model that suggests that the Smerwick Group evolved within a small extensional half‐graben on the northern margin of the Munster Basin. This model accounts for the stratigraphic and structural relationships observed, and implies that the Smerwick Group is of Late Devonian age.
The carboniferous lithostratigraphy of Southeast County Limerick, Ireland, and the origin of the shannon trough
Authors: Strogen Peter
Published: July 2010

The Carboniferous succession in southeast County Limerick, on the southeastern margin of the Shannon Trough, is Courceyan to mid‐Namurian in age and over 1900 m thick. The lithostratigraphy is described in detail. Its most important aspect is the presence of two thick volcanic sequences, a Chadian one of the alkali basalt to trachyte suite and one of Asbian age dominated by limburgites and ankaramites. The associated Dinantian carbonates are of shelf or ramp facies throughout, and no fundamental division into shelf and basin facies occurs as in the Dublin and Craven Basins in early Viséan times. Rapid differential subsidence between this area and the Shannon Estuary began during deposition of the late Courceyan to early Chadian Waulsortian facies but was less marked in the remaining Viséan when much of the volcanic topography was preserved by rapid basinal subsidence. There was basinal inversion in the late Dinantian to lower Namurian, followed by renewed subsidence in mid‐Namurian times. This contrasts with the continuous rapid subsidence of the area further west on the Shannon Estuary. This behaviour, together with a comparison of that of nearby Carboniferous basins such as the Dublin, South Munster, and Craven Basins, which lack substantial volcanic sequences, suggests an origin in a transtensional regime rather than one of simple crustal stretching.
Age of the ordovician andesitic conglomerate of castle hill, Montgomery, Powys, Wales
Authors: Cave R. , Dean W. T. , Hains B. A.
Published: July 2010

Marine fossils including Broeggerolithus broeggeri (Bancroft) and Salterolithus caractaci (Murchison) collected from strata surrounding the andesitic conglomerate of Castle Hill, Montgomery prove that the volcanic event which produced it, and possibly also the andesite of Moel‐y‐Golfa 10 miles to the NNE, was of Caradoc (early Soudleyan) age.
Anomalous vergence patterns on the rhoscolyn anticline, anglesey: Implications for structural analysis of refolded regions
Authors: Lisle Richard J.
Published: July 2010

Traditional methods of mapping folded regions rely heavily on vergence or minor structures (folds and intersecting foliations) to confine the position of major folds of the same generation. It is argued on theoretical grounds that in certain circumstances the vergence of early structures can become reversed by later deformation. Natural examples of this vergence reversal occur on the NW limb of the Rhoscolyn Anticline in Anglesey. Lack of awareness of the possibility of this phenomenon could lead to serious misinterpretation of data from less completely exposed folded regions.
The lower carboniferous (dinantian) of the Swords area: Sedimentation and tectonics in the Dublin Basin, Ireland
Authors: Jones Gareth L. L. , Somerville Ian D. , Strogen Peter
Published: July 2010

The litho‐ and biostratigraphy of the Lower Dinantian succession in a deeper part of the Dublin Basin is described. The sub‐Waulsortian Malahide Limestone Formation (emended) is described fully for the first time, and has proved to be very much thicker than was previously suspected, in excess of 1200 m. Succeeding the ‘Lower Limestone Shale’ unit, which is transitional from the underlying Old Red Sandstone facies, the following six new members are recognized: Turvey Micrite Member, Swords Argillaceous Bioclastic Member, St. Margaret's Banded Member, Huntstown Laminated Member, Dunsoghly Massive Crinoidal Member and Barberstown Nodular Member (top).

The Malahide Limestone Formation is overlain by ‘Waulsortian’ limestones of the Feltrim Limestone Formation (new name) which form overlapping and isolated mudmounds with complex relationships with their enclosing non‐mound facies. Though very much thicker, the Courceyan succession is comparable with that elsewhere on the south side of the Basin, and is part of the Kildare Province (Strogen and Somerville 1984). Isopach maps for the region show that this province and the North Midlands are separated by the deepest part of the Dublin Basin, named the ‘East Midlands Depocentre’, in which a shale‐dominant facies is present. The top of the ‘Waulsortian’ is of early Chadian age. Formations younger than this are dominated by basinal calcareous shales (Tober Colleen Formation) and by storm deposits and calciturbidites with appreciable terrigenous input from the east (Rush Formation).

The Courceyan main shelf conodont biozones are also greatly thickened in this area. ThePseudopolygnathus multistriatusBiozone (> 300 m thick) is succeeded by a very thick (> 900 m)Polygnathus mehliBiozone. The base of the Chadian is considered to occur below the top of the Feltrim Limestone Formation and, although equivocal, may be diagnosed in the Dublin Basin by the first appearance of the problematic microfossilSphaerinvia piaiand a primitive form of the calcareous algaKoninckopora.

In the late Courceyan, the Swords area was part of a gently sloping shelf extending northwards into the basin. During deposition of the Feltrim Limestone Formation there was major deepening and there is evidence of initial break up of the Dublin Basin by faulting into separate blocks. By Chadian time the Basin was definitely subsiding by fault displacements and basinal limestones contain shallow water faunas and littoral sand and pebbles derived by turbidite flows from the margins of the higher blocks. The early subsidence was apparently by pure flexure, but in the Viséan the Dublin Basin was fault‐controlled, differing from the adjacent Shannon Basin in having both margins strongly faulted.
The farnacht formation along the south side of the clew bay fault zone, Western Ireland: Its chemistry and age of metamorphism
Authors: Max M. D. , Rex D. , Winchester J. A.
Published: July 2010

The tectonically isolated Farnacht Formation consists of calc‐alkaline dacitic‐andesitic lavas of volcanic arc affinity. It is situated immediately to the south of the Clew Bay Fault Zone (western continuation of the Highland Boundary Fault Zone of Scotland) in the northeast corner of the Lower Palaeozoic South Mayo Trough in northwest Ireland. It has been metamorphosed to biotite grade greenschist facies following the development of a pervasive, c‐s composite muscovite, quartz, and feldspar schistosity. The Farnacht Formation may comprise a terrane that is directly unrelated to nearby Ordovician and Silurian rocks; its present position was fixed largely by Wenlock times.

The age of the Farnacht Formation and the deformational event(s) that produced the schistosity are not known. 40Ar/39 Ar step heating from four specimens have dated the crystallization of biotite at from 422 ± 2 to 405 ± 14 Ma with a mean age of 413 Ma. These ages date either the post‐D2, pre‐D3 metamorphic peak, or a hornfelsing of the same structural age related to an unseen thermal source, and provide a minimum age for the end Silurian ‐ early Devonian Caledonian tectonothermal activity in the northeast part of the South Mayo Trough.
Soil‐zone microfabrics in calcrete and in desiccation cracks from the upper Jurassic purbeck formation of dorset
Authors: Andrews Julian E.
Published: July 2010

Soil‐zone microfabrics, alveolar‐septal structure, needle‐fibre calcite, and calcans are described from horizontal calcrete layers, stringers, and infillings in vertical desiccation cracks from an Upper Jurassic limestone in the Lower Purbeck Formation of Dorset. These calcrete palaeosols occur in an oolitic limestone (the Hard Cap) which represents former evaporitic lagoonal to carbonate mudflat environments. The calcretes occur 6‐10 cm below the Great Dirt Bed, a former rendzina soil with rooted tree remains. Desiccation cracks and vugs formed in the oolitic sediment before Great Dirt Bed times. After formation of the Great Dirt Bed, soil‐water rich in dissolved CaCO3 preferentially flowed through natural conduits in the underlying sediment, namely the desiccation cracks and vugs. Calcrete precipitated in these cracks and vugs around decaying plant roots, and probably, during more arid (evaporative) climatic periods. These palaeosol microfabrics are among the first to be described from the British Jurassic and were probably preserved due to the semiarid Lower Purbeck climate where rapid oxidation of organic matter limited the amount and strength of carbonic acid generation, thereby limiting extensive dissolution of early formed soil‐zone carbonate. Early diagenetic cementation of the sediment also aided microfabric preservation by sealing off soil‐zone structures from subsequent diagenetic fluids.
The arenig in South Wales: Sedimentary and volcanic processes during the initiation of a marginal basin
Authors: Traynor John‐Joe
Published: July 2010

Marine clastic sediments and volcanics of Arenig (Ordovician) age crop out in South Wales. These were deposited after presumed late Tremadoc erosion and subsequent arc volcanicity. Arenig sedimentation was transgressive, and followed significant erosion of the arc volcanics. Arenig conglomerates, sandstones, and mudstones were deposited in deltaic and turbiditic systems. Storm and tidal processes influenced the shallow marine deposits. The minor rhyolitic volcanics extruded during the Arenig reflect the development of Ordovician marginal basin‐type volcanics across Wales. Five sandstone petrofacies are defined and reflect differing proportions of these volcanics and of Cambrian and Precambrian basement material. Sedimentation patterns were controlled by intra‐Arenig tectonism during an overall rise in sea level. Facies and petrofacies were ponded in small, interconnected, marine sub‐basins. Earliest Arenig tectonism and sedimentation, also recognized in North Wales, reflects the initiation of a marginal basin in Wales.
An ordovician fauna from Lough Shee, Partry Mountains, Co. Mayo, Ireland
Authors: Harper D. A. T. , Graham J. R. , Owen A. W. , Donovan S. K.
Published: July 2010

An hitherto undocumented early Ordovician fauna from mudrocks at Lough Shee in the Partry Mountains contains species of sponge, machaeridian, bivalve, gastropod, cephalopod, brachiopod, and trilobite, together consistent with a deep‐water setting marginal to the North American province. The trilobite and brachiopod data suggest a correlation of the Lough Shee mudrocks with the upper Whiterock Stage (equivalent to a level near the D. ‘bifidus’ – D. murchisoni boundary, within the middle Llanvirn). The sparse, low‐diversity assemblage is specialized and demonstrates the development of aspects of the Whiterock fauna in the South Mayo Trough.
Storm‐influenced shelf deposits from the silurian of Western Ireland: A reinterpretation of deep basin sediments
Authors: Nealon T. , Williams D. Michael
Published: July 2010

The Lough Muck Formation (Wenlock) is part of the Silurian succession of North Galway, western Ireland. The formation had originally been interpreted as a transitional sequence between shelf and basinal facies in the succession. Its three members (1, 2, and 3 of Laird and McKerrow 1970) were envisaged as representing deposits of the continental rise, slope, and shelf respectively. A subsequent interpretation suggested that the two upper members were of shallow marine origin and that the proposed major Wenlock regressive event was already extant by the time of deposition of Member 2. In this paper we examine Member 1 to ascertain its environment of deposition and thus refine the sea level curve for this element of the Silurian.

Member 1 may be divided into five lithofacies A to E. Facies A comprises amalgamated sandstones with low‐angle cross‐stratification. Facies B consists of couplets of erosively based coquinas containing a low‐diversity parautochthonous fauna and graded, laminated sandstones. These couplets are interbedded with thin laminated siltstones. Facies C is characterized by parallel laminated siltstones and discontinuous, erosively based sandstones. Facies D consists of fossiliferous siltstone and Facies E of thin sandstones with low‐angle cross‐lamination. Facies A and B are interpreted as shoreline deposits based upon comparison with published descriptions of such deposits elsewhere. Facies, C, D, and E, lateral equivalents of the first two facies, are interpreted as deposits which accumulated further offshore. The presence of couplets consisting of a coquina and overlying laminated sandstone, and fossil distribution, the presence of amalgamated beds and low‐angle cross‐stratification suggest the influence of storms on this shallow‐water sequence. A palaeoreconstruction is proposed which envisages a shelf deepening to the southeast off a shoreline which had an approximately northeasterly orientation.