bluuebunny/crossref_metadata_2025 huggingface dataset:
Brecciation textures and tepee structures in Quaternary calcrete (caliche) profiles from eastern Spain: The plant factor in their formation
Authors: Klappa Colin F.
Published: July 2010

Field studies of brecciation textures and tepee structures in Quaternary calcretes from eastern Spain reveal that vegetation plays a fundamental role in their formation, alteration and destruction. Biophysical and biochemical activities of higher plant systems produce brecciation textures and some tepee structures. Brecciation of indurated calcrete profiles form rhizo‐breccias which may be used as indicators of terrestrial conditions in ancient successions.
Aspects of the sedimentology, palynology and palaeobotany of the Upper Devonian of southern Kerry Head, Co. Kerry, Ireland
Authors: Bridge J. S. , Van Veen P. M. , Matten L. C.
Published: July 2010

The uppermost 220 m of Upper Devonian sedimentary rocks of southern Kerry Head are described in terms of three lithofacies associations. Facies association 1 (about 49 per cent of succession) comprises fine to medium grained sandstones, with basal erosion surfaces and intraformational breccias, dominantly cross‐stratified, and usually displaying a multistorey character. They are interpreted as deposits of laterally migrating and aggrading single‐channel rivers, flowing in a southerly direction. Facies association 2 (43 per cent) comprises interbedded fine to very fine grained sandstones and siltstones, displaying a diversity of sedimentary structures, rapid lateral and vertical facies transitions, and occurring as broad sheets or channel‐filling sequences. They are interpreted as crevasse, levee, and channel‐fill deposits. Association 3 (8 per cent) is dominantly siltstone, with lenses and sheets of very fine sandstone, interpreted as the floodbasin deposits of a semi‐arid alluvial plain.

Macrofloras and spores occurring in association 2 indicate: (1) major plants (woody seed ferns) grew in areas very close to palaeochannel margins; (2) a phytogeographic location within the Munster Basin comparable with Hook Head; and (3) a Late Devonian age for the succession.
Fold and cleavage development within cambrian metasediments of the vale of ffestiniog, North Wales
Authors: Hawkins T. R. W. , Jones F. G.
Published: July 2010

New road cuttings have exposed a large part of the Merioneth Series. The rocks are low‐grade thinly layered metasediments which have undergone extensive buckling resulting in tectonic ripples, mullions, and crenulations. It is suggested that the periclinal form of these structures may be the result of buckling layered sequences with longitudinal and transverse zones of constraint (heterogeneities). The process is analogous to ‘quilting’ of thin metal sheets and the heterogeneities are perhaps due to layer thickness variation. There are two foliations; which may form a progressive sequence of cleavage development during the evolution of the fold style.
Aspects of the geology of the south Irish Sea
Authors: Whittington R. J. , Croker P. F. , Dobson M. R.
Published: July 2010

Seabed samples, consisting of shale of Lower Liassic age and limestones of Upper Liassic age, have been recovered from the northwest flank of the St. George's Channel basin. These data have made possible the calibration of parts of lines 6 and 11 of the I.G.S. deep seismic survey. An updated and refined version of the geology of the south Irish Sea is presented which incorporates the new information and indicates the extent of the Precambrian and Lower Palaeozoic basement that is now thought to subcrop beneath the Pleistocene cover southwest of the Lleyn Peninsula. In addition the offshore extension of the Bala Fault is suggested to be an intra‐basin fault across Cardigan Bay and St. George's Channel.
The boyndie syncline, a D1 structure in the Dalradian of Scotland
Authors: Treagus J. E. , Roberts J. L.
Published: July 2010

The structure of the Dalradian rocks of the Banffshire coast has been re‐examined. It is shown that D1 structures face upwards along the entire section and the major Boyndie Syncline (Sutton and Watson 1956) must also be of D1, age and not D3 as proposed by Johnson (1962). D2 structures are developed in the west, most strongly in the Portsoy Group and Cowhythe Gneiss where they may be related to the Portsoy Thrust (Elles 1931). East of the Cowhythe Gneiss D2 structures are not developed but D3 structures are of local importance. Porphyroblast growth is considered to be post‐D1, pre‐D3 related to the ‘active’ D2 deformation in the west (Barrovian) and to the ‘static’ D2 interval in the east (Buchan). The wider implications of these conclusions for Dalradian structure are briefly considered.
The ‘old red sandstone’ of county mayo, Northwest Ireland
Authors: Graham John R.
Published: July 2010

The distribution and stratigraphic relations of the Old Red Sandstone of the Clew Bay area. County Mayo are described. They comprise two groups both dominated by conglomerates, one Lower Devonian and one Middle Devonian, which have differing clast contents and which are separated by faults. The sediments are described in terms of five facies which are all interpreted as alluvial fan deposits. Provenance data from palaeocurrents and clast composition suggest transport predominantly to the west‐northwest but one formation shows an opposite sense of transport. The rocks are folded about northeast‐southwest axial traces and are affected by numerous faults. Structures are more complex than those of the Lower Carboniferous rocks which unconformably overlie the Devonian. A similar tectonosedimentary setting to the Old Red Sandstone of parts of the Scottish Caledonides is indicated.
The ashgill rocks of the glyn ceiriog district. North wales
Authors: Hitter N.
Published: July 2010

The Ashgill rocks of the Glyn Ceiriog district comprise a relatively thick sequence of mudstones and siltstones with subordinate sandstones and locally developed limestone members. Closely related deposits are found in the inliers of Cym‐y‐brain and Mynydd Cricor to the north. Correlation with other areas of Ashgill rocks suggests that the Dolhir Formation, of the Glyn Ceiriog district, can be dated as mid‐Cautlcyan to Rawtheyan while the overlying Glyn Formation is high Rawtheyan to Himantian. In the inliers to the north, that part of the Cyrn‐y‐brain Formation which is exposed is dated as Rawtheyan and both the Plas Uchaf Formation (Cym‐y‐brain) and Cricor Formation (Mynydd Cricor) are taken to be Hirnantian.

The succession is interpreted as a transgressive‐regressive sequence in which shallow shelf mud‐stones and siltstones with storm‐sand and coquinid layers are overlain by shallow water shoreline deposits.

Although the base of the Ashgill is not exposed in the inliers to the north, in the Glyn Ceiriog district it is seen to rest unconformably on older Ordovician strata; in all three areas the Ashgill is apparently conformably overlain by Lower Llandovery shales and sandstones.
Beaconites antarcticus: a giant channel‐associated trace fossil from the lower old red sandstone of south wales and the welsh borders
Authors: Allen J. R. L. , Williams B. P. J.
Published: July 2010

Trace fossils of Beaconites type are found abundantly and widely in the Old Red Sandstone magnafacies of the British Isles, particularly in fluviatile deposits, where they occur in or closely associated with channel sandstones. Because of their giant size, however, terminations to the sediment‐filled burrows are almost impossible to detect, and it has hitherto been uncertain whether the Beaconites organism dwelt in or near active rivers, or merely colonized the sandy deposits at their abandoned sites. At Llanstephan in southwest Wales B. antarcticus is preserved in a laterally accreted sandstone, a unique example of the trace fossil being truncated by an erosion surface cut during the sideways growth of a presumed point bar. The Beaconites organism is therefore thought to have lived in and near active river channels, where a moist environment was provided.
The Ordovician biostratigraphy of Portugal—A review with new data and re‐appraisal
Authors: Romano Michael
Published: July 2010

The history of research on the Ordovician rocks of Portugal is briefly outlined and the biostratigraphy of different regions is reviewed. Ten stratigraphic columns are presented for selected areas and the lithological and faunal characteristics are described. The trilobites belong to the Selenopeltis province and evidence is given for the recognition of two faunal subprovinces (termed associations by Henry 1980) in north and central Portugal during the Arenig to Llandeilo. The current state of knowledge of Ordovician palaeogeography in Portugal is discussed and maps are presented for the Arenig and Llandeilo Series.
The last glaciers (Loch Lomond Advance) in Snowdonia, N. Wales
Authors: Gray J. M.
Published: July 2010

Evidence for 35 former cwm glaciers has been mapped in Snowdonia, N. Wales. Glacial limits are based on end moraines, boulder and drift limits, and the down‐valley extent of hummocky moraine. Protalus ramparts indicate that at least 16 semi‐permanent snow beds down to altitudes of 150 m also existed. Radiocarbon dates and pollen stratigraphy indicate that the glaciers and snow beds belong to the Loch Lomond (Younger Dryas) Stadial. The existence of a large number of ‘Older Series Moraines’ is questionned. Glacier reconstruction and contouring allows calculation of fan line altitudes, and trend surface analysis indicates that they rise from 450 m in the southwest to 700 m in the northeast. It is inferred that mean July temperature at sea‐level was around 8·5°C. Two differences between north and south Britain are recognized. Firstly in Snowdonia, as in the Lake District and Southern Uplands, the dominance of southerly air streams appears less than in the Scottish Highlands. Secondly, whereas in the Scottish Highlands, the glaciers appear to have stagnated in situ following initial active retreat, some of those farther south were active during much of the time their margins retreated.
Petrology of an ophiolitic cumulate sequence from Pindos, Greece
Authors: Capedri Silvio , Venturelli Giampiero , Toscani Lorenzo
Published: July 2010

The ophiolitic sequence which crops out along the Aspropotamos Valley, Northern Pindos, Greece is composed from the bottom to the top of cumulates, dolerites, basaltic lavas, upper pillow lavas with basaltic/andesitic composition, and scarce basaltic dykes. The intrusive sequence, which is the subject of the present paper, exhibits magmatic layering more pronounced at the bottom than at the top where isotropic gabbros occur; they grade into the overlying dolerites. Troctolites with rare ultramafites prevail in the lower section and olivine gabbros in the upper section; at the top two‐pyroxene gabbros appear. The rocks are mainly adcumulates and mesocumulates with subordinate heteradcumulates. The cumulus phases separated in the order: olivine and Cr‐spinel, plagioclase, clinopyroxene, orthopyroxene. Olivine, plagioclase and pyroxenes frequently exhibit adeumulus overgrowth. Intercumulus phases may be plagioclase, clinopyroxene, orthopyroxene, pale brown amphibole and magnetite. Where pore material is present, it is composed of plagioclase, clinopyroxene, orthopyroxene, hornblende and ores. Cr‐spinel occurs mainly at the bottom of the sequence (Cr2O3 between 30·5 and 39·8 per cent), while magnetite appears as a very rare phase in the upper section. Olivine, orthopyroxene, clinopyroxene exhibit slight cryptic variation (Mg × 100/(Mg + Fe) in the range 90–79, 90–70, 93–72 respectively). The investigated dolerites are non‐cumulus rocks where clinopyroxene may be more magnesian than in the uppermost gabbros. The cumulate sequence and dolerites underwent variable but generally slight spilitization, in contrast to the overlying lavas. The sequence was generated through crystal accumulation probably from periodic pulses of tholeiitic magma; newly injected magma batches mixing with magma fractions already differentiated in the magma chamber. The high fluid pressure evidenced by the fluid inclusions in plagioclase and the whole chemical trend of the cumulate sequence are consistent with a genesis above a subduction zone, as already hypothesized for the overlying lavas.
Petrology of nepheline syenite gneiss from Amazonian Brazil
Authors: Lowell G. R. , Villas R. Netuno
Published: July 2010

Nepheline syenite gneiss is exposed in three localities near the village of Boca Nova (47·04′W, 1°51′S) in northeastern Pará, Brazil. Isotopic and chemical evidence for an igneous premetamorphic history include: (1) bulk compositions which plot in the Q–Ne–Ks system on a peralkaline fractionation curve; (2) bulk compositions which fall on the Hviddal igneous trend in the SiO2–Al2O3–Na2O + K2O molecular diagram; (3) an average K/Rb ratio identical to the average for nepheline syenites of the Khibina massif; (4) K/Rb ratios which lie on the ideal igneous fractionation curve; (5) Nb(Ta) contents far in excess of average crustal abundance; and (6) a low Sr87/Sr86 value (0·7034) characteristic of mantle derivation.

Post‐kinematic lit‐par‐lit injections, discordant veins, and concordant pods of leucocratic nepheline–alkali feldspar pegmatite partially replaced the metamorphic assemblage and destroyed any microscopic equilibrium texture that may have been present. The final disequilibrium assemblage consists of Fe‐rich biotite and two generations each of sodic plagioclase, microcline, and nepheline. Some minor metasomatic chemical effects may be present in the rocks but a case for nephelinization of crustal rocks cannot be documented. Field, petrographic, and chemical constraints indicate that the Boca Nova gneiss is an early‐stage migmatite formed by anatexis of metamorphosed igneous nepheline syenite or its volcanic equivalent. Regional metamorphism and partial melting opened the Rb‐Sr system so that the whole‐rock Rb/Sr isochron age of 724 m.y. has no unambiguous interpretation. A K/Ar age of 580 ± 10 m.y. from biotite denning the metamorphic foliation is regarded as a minimum date for the regional metamorphism and anatexis. No other alkaline rocks of comparable age are known in the Sao Luis Craton.
Intrusive relationships between young and old Archaean gneisses: evidence from Ivisǎrtoq, southern West Greenland
Authors: Hall R. P. , Friend C. R. L.
Published: July 2010

Relict discordant relationships between the c.3000–2800 Ma old Nǔk granitic (s.l.) gneisses and the c.3700 Ma old Amǐtsoq gneisses of Ivisǎrtoq clearly indicate that the Nǔk gneisses originated as intrusive sheets and bosses. The older gneisses are preserved as continuous banded units which are injected by thin granitic dykes and sills and become progressively disrupted by increasing proportions of intrusive Nǔk granitic material until they occur merely as discrete xenoliths and enclaves dissemminated within a younger gneiss matrix. The Nǔk granites were emplaced into the cores of developing large scale folds within intercalated oceanic and ancient continental portions of the Archaean crust, previously interleaved by thrusting.
Brachiopods from a Lower Palaeozoic mass flow deposit near Llanafan Fawr, Central Wales
Authors: Lockley Martin G.
Published: July 2010

Brachiopod‐dominated assemblages from the Allt y Clych conglomerate near Llanafan Fawr provide good evidence for a Silurian (Lower Llandovery) age. The conglomerates are interpreted as mass flow deposits and are related to the revised stratigraphy of Davies (1980) by emendation of some of the author's previous interpretations.
Structure of the Ordovician succession around Aberdaron, southwest Llŷn, North Wales
Authors: Hawkins T. R. W.
Published: July 2010

Three deformation phases are recognizable within the Lower Ordovician metasedimentary sequence of the Aberdaron area and they are similar to those described for Lower Palaeozoic sequences in other parts of North Wales. There is no certain evidence however for a major Aberdaron Syncline as described by some previous workers. The first deformation phase produced southcast verging mesoscopic folds with steep to moderate dipping axial surfaces and a sporadic axial plane cleavage. The second deformation was relatively weak and produced only a low‐dipping crenulation cleavage at a few favoured localities. The third phase gave rise to numerous small buckle folds, kinks in some pelitic units where the first cleavage was well developed, an axial plane cleavage, and a suite of quartz veins. The orientation of the third phase minor structures is not uniform and the fold trend and strike of axial plane cleavage varies from east‐northeast to south‐southeast, although retains a constant angular relationship to the local strike of bedding. The distribution of the third cleavage is bimodal and the third deformation phase may have been brought about by conjugate shears during a late brittle fracture stage of NW–SE compression. The structural sequence affecting the Ordovician cannot be correlated with that in the Mona Complex and it seems likely that the Mona Complex was deformed before the Arenig.
Palinspastic reconstruction of the Grenville terrane in the Blue Ridge Geologic Province, southern and central Appalachians, U.S.A
Authors: Bartholomew M. J.
Published: July 2010

Examinations of Grenville massifs in the Blue Ridge Geologic Province of Virginia and North Carolina indicate that the country rocks (∼ 1100–1450 Ma) are layered gneisses that were metamorphosed during Grenville orogenesis (∼ 1000–1100 Ma) to amphibolite to granulite facies and intruded by plutonic suites. Subsequently, the Grenville terrane was intruded by a suite of peralkaline granitic plutons (∼ 700 Ma) and progressively overlapped westward by Upper Precambrian to Cambrian sedimentary and volcanic rocks.

Following deposition of Upper Precambrian and Palaeozoic rocks, the Blue Ridge Geologic Province was subjected to Taconic metamorphism (∼ 450–480 Ma) which generally increased in intensity southeastward from greenschist (chlorite grade) to upper amphibolite (sillimanite grade) facies. Large‐scale late Devonian thrusting (∼ 350 Ma) along the Fries fault system and the Brevard zone‐Yadkin fault system produced the present day distribution of juxtaposed Grenville massifs and Palaeozoic metamorphic zones in the Blue Ridge Geologic Province.

Palinspastic restoration of the Taconic metamorphic zones to their pre‐late Devonian relative positions yields an ∼ 50 km displacement on the Fries fault system near the Grandfather Mountain window and and an ∼ 80 km displacement on the Smith River allochthon farther east.

Restoration of the Grenville massifs to this same palinspastic base shows that Grenville metamorphic grade decreased southeastward from the deeper granulite facies (opx + gar) to the shallower granulite facies (opx ± amp) to amphibolite facies.
Note on the age and fauna of the Lynton Beds (Lower Devonian) of north Devon
Authors: Evans K. M.
Published: July 2010

The Lynton Beds represent shallow marine sediments with a restricted fauna dominated by brachiopods. The age indicated by the brachiopod fauna is late Emsian, although the possibility of a younger date for the uppermost horizons cannot be discounted.
Geophysical down‐hole recognition of the Lower Devonian‘Psammosteus’Limestone and Townsend Tuff Bed, South Wales
Authors: Tunbridge I. P.
Published: July 2010

Geophysical down‐hole logs from the Maesteg and Senghenydd boreholes permit the recognition of the Townsend Tuff Bed and‘Psammosteus’Limestone markers on the basis of distinctive log motifs. The thickness of the interval between these markers is greater than at basin‐margin localities and may be an indication of rapid deposition in the centre of the Anglo‐Welsh basin in Lower Devonian times.
Tectonic relationships of the Leinster Granite, Ireland
Authors: Cooper M. A. , Brück P. M.
Published: July 2010

The Leinster Granite in southeast Ireland comprises five plutons, which were diapirically emplaced into the Lower Palaeozoic rocks of the Leinster Massif. The pre‐existing Caledonian cleavage was exploited during intrusion which has resulted in an en echelon development of plutons as the granite belt cuts obliquely across the regional cleavage trend. A foliation map of the Leinster Massif illustrates how the foliation trend is modified from the regional trend within a shear zone approximately coincident with the granite belt. The shear zone has a sinistral sense of shear and developed before the plutons were fully consolidated. The shear strain decreases from 5 at the northern end of the shear zone to 0·6 near its termination at the southern end of the granite.
The Origin of late Devensian sands and gravels, southeast Anglesey, N. Wales
Authors: Helm D. G. , Roberts B.
Published: July 2010

The Lleiniog Sand and Gravel Formation, of late Devensian age, has been divided into four Members. The sediments are interpreted as the sequential products of the wasting of a single ice lobe. Member I formed where subglacial streams debouched into a pro‐glacial lake and is noteworthy for the occurrence of a bedform, hitherto undescribed but which may be common in many outwash sequences; Member 2 consists of channel sands and gravels deposited by pro‐glacial streams; Member 3 has the characters of a melt‐out till deposited after a readvance; and Member 4 accumulated in pools of meltwater on the irregular surface of Member 3.

Clasts above granule grade are dominantly of locally‐derived Carboniferous rocks although a far travelled component from northern England and southern Scotland can be distinguished as well as a small but constant input of Lower Palaeozoic rock types from the Conwy area. The sand grade is dominated by quartz grains released from Permo‐Triassic sandstones. Clay grade material has been derived from Carboniferous shales.
Fluidized mixtures of magma and rock in a late Caledonian breccia dyke and associated breccia pipes in Appin, Scotland
Authors: Platten I. M.
Published: July 2010

This paper describes an unusual occurrence of igneous material as clasts in dyke and pipe breccias associated with late Caledonian minor intrusions. It is shown that the clasts were in a plastic condition when incorporated into the breccia rock. These igneous clasts were derived from magma disrupted at depth and then transported into the fluidized breccia columns where they were mixed with large numbers of clasts derived from the quartzite wall‐rocks. Textures and planar fabrics developed during collapse of the fluidized system are described and shown to be separable from the later compaction associated with extensive pressure solution of the fine matrix. Most Caledonian breccia pipes lack igneous clasts and it is considered that this group of breccias represent the rarely‐preserved boundary zone between active magma and breccia systems.
Arenig trace fossils from the Salamanca area, western Spain
Authors: Pickerill R. K. , Romano M. , Meléndez B.
Published: July 2010

Trace fossils are recorded at two localities from the ‘Armorican Quartzite’ (Lower Ordovician) in the Salamanca area, western Spain. Sixteen ichnospecies, belonging to twelve ichnogenera, are described; all ichnospecies occur in the upper part of the unit, only four in the lower part. The ichnogenera comprise Arthrophycus, Cruziana, Daedalus, Didymaulichnus, Diplichnites, Diplocraterion, cf. Gor‐. dia, Monomorphichnus, Muensteria, Palaeophycus, Planolites, and Rusophycus. The presence of Cruziana furcifera, C. goldfussi, C. rugosa, and C? cf. imbricata indicate that the upper part of the unit is of Arenig age. The lower part has yielded only the two former ichnospecies and may extend down into the Tremadoc. The species of Cruziana and their stratigraphical significance are discussed.
Ordovician rocky shoreline deposits–the basal Trenton Group around Quebec City, Canada
Authors: Harland T. L. , Pickerill R. K.
Published: July 2010

Around Quebec City the lowest Trenton Group sediments rest directly upon a highly irregular Precambrian surface and represent the deposits of a high‐energy, irregular, rocky shoreline which developed as the Ordovician sea onlapped a major positive topographic feature known as Montmorency Promontory. The complicated lithofacies mosaic developed along this shoreline consists of: (1) Arkosic sandstones, representing reworked regolith and marginal marine elastics; (2) Solenopora gravels, which comprise partly reworked colonies from the bare rock substrate and partly reworked algal maerls; (3) Fine‐grained limestones, which were deposited in low energy environments between and in the lee of numerous islands and shoals; (4) Skeletal limestones, representing island fringing shoals and ephemeral beaches, with extensive thickets of the ramose bryozoan Hallopora; (5) Bryozoan liméstones, which represent low‐energy, subtidal deposits with abundant delicate bryozoans; and (6) Coquina limestone lenticles, which accumulated in channels cut into the subtidal Bryozoan limestones. The absence of older Ordovician and Cambrian sediments in the vicinity of Quebec City indicates that Montmorency Promontory at the time of deposition of these Trenton deposits was probably manifested as a rugged archipelago. This represented the remnant of large‐scale topographic highlands which had developed at the continental margin during the late Precambrian in association with extensional rifting, transform faulting, and the inception of the Iapetus Ocean. Gradual subsidence of this topographic high and the development of the rocky shoreline relates to the subsequent development of a compressional system and initiation of ocean closure in the early Middle Ordovician.
Petrogenesis of the gabbros from Mt. St. Hilaire, Quebec, Canada
Authors: Greenwood R. C. , Edgar A. D.
Published: July 2010

Mt. St. Hilaire occurs as a small funnel‐shaped intrusion in the Monteregian petrographic province of Quebec and consists of alkali gabbros and later nepheline syenites. Based on field relations, petrography, and geochemistry, five types of gabbro are recognized. In order of intrusion these are: leucogabbro, foliated gabbro, kaersutite‐biotite gabbro, kaersutite gabbro, and a gabbro‐melagabbro series. Based on analyses of the early‐forming ilmenite‐titanomagnetite, the gabbros crystallized under high fO2 conditions which lead to subsequent crystallization of olivines with high MnO contents. Fractionation of ilmenite and titanomagnetite was a major control on the Ti and A[TV]concentrations in the clinopyroxenes. Plagioclase compositions in the gabbros became richer in Ab contents in the sequence gabbro‐melagabbro to leucogabbro. Whole‐rock analyses suggest that the parental magma of alkali basaltic composition was fairly evolved prior to emplacement. Lack of olivine in the cumulate gabbro‐melagabbros and low Ni and Cr in all gabbros may reflect either extreme olivine fractionation and/or a very low olivine content in the source material for these basalts. Differentiation of the gabbros occurred both pre‐ and post‐emplacement, probably by a process of crystal‐liquid fractionation at depths between 3‐5 and 8 km. This is in accordance with geophysical measurements for other Monteregian intrusions. A model is presented for the mechanism of emplacement.
Age of the Lough Talt and Easky adamellites in the central Ox Mountains, N.W. Ireland, and their structural significance
Authors: Long C. B. , Max M. D. , O'Connor P. J.
Published: July 2010

The Lough Talt and Easky adamellites in the north‐central Ox Mountains inlier were originally regarded as being nearly synchronous in age of emplacement with the more strongly deformed c. 480 Ma Ox Mountains granodiorite. They are now shown by Rb‐Sr whole‐rock dating to be significantly younger at c. 400 Ma. This recognition of the emplacement of late Silurian/early Devonian Newer Caledonian granites in the central Ox Mountains inlier indicates that the thermal overprinting by the adamellites of the regionally metamorphosed Ox Mountains succession is not an early Ordovician event. Earlier interpretations, using deformationai events and igneous intrusions, advanced by others to suggest that the Ox Mountains succession is pre‐Caledonian are now greatly weakened since the deformationai sequence in the Ox Mountains succession is now known to span a longer period of time, ranging from Grampian (late Cambrian to early Ordovician) to Caledoniansensu stricto, and therefore leaves fewer events to have occurred prior to the early Ordovician emplacement of the Ox Mountains granodiorite.
Ordovician and Silurian coronates (echinodermata) from Czechoslovakia
Authors: Paul C. R. C.
Published: July 2010

Coronates form a small but distinctive group of lower Palaeozoic echinoderms, most closely related to eublastoids. The coronate fauna of Czechoslovakia includes Mespilocystites bohemicus Barrande 1887 from the Lower and Middle Caradoc, characterized by a conical theca, coronal processes which diverge markedly upwards, and distinctly angled radial furrows; Stephanoblaslus mints (Barrande 1887), from the Wenlock, typified by an elongate bud‐shaped theca with three radiating keels at the base and a very narrow stem; and ‘Stephanocrinus’ gemmiformis (Hall 1852) from the Ludlow, with a cup‐shaped theca and low coronal processes. ‘S.’ gemmiformis has not previously been reported from outside North America or above the Wenlock.
The geometry of ductile conjugate fold systems in the Ardnamurchan Moine, Scotland
Authors: O'Brien Brian H.
Published: July 2010

Four ductile phases of superimposed deformation are regionally mappable in the Ardnamurchan Moine in the Western Highlands of Scotland. These deformations are recognized on the basis of their individual geometrical characteristics and are named, in ascending order, the Kentra phase (D1), the Ardtoe phase (D2), the Glenmore phase (D3), and the Claish phase (D4). Non‐systematic earlier structures (pre‐D1), possibly coeval with the climactic metamorphism, are locally observable. Folds and fabrics produced by the D2, D1, and D4 deformations, however, developed as conjugate sets.

There is a significant spatial variation in the distribution and intensity of each of the D1‐D4 phases. The regional deformation of the Moine schists is notably inhomogeneous due to the nature of the D1‐D4 incremental strains. In the areas affected by large finite strains, pervasive, normally composite LS‐fabrics are developed. In the areas that persistently suffered negligible strain increments, right‐way‐up rocks commonly display several mineral foliations lying at various angles to bedding. The conjugate systems of folds and fabrics appear to be related to the evolution of a ductile shear belt in Ardnamurchan.
Optimized similarity matrices applied to the study of carbonate rocks
Authors: Hennebert Michel , Lees Alan
Published: July 2010

The primary and early diagenetic components of carbonate rocks are commonly arranged systematically in a sort of ‘relay’ along a gradient formed by one or several environmental factors. Such a relay, if present, can be revealed by the optimization of a matrix of similarity coefficients. The technique presented uses presence/absence data and is simple and rapid. An illustration is given using data from some Dinantian limestones in southwest Britain.
Facies variation in a Late Pleistocene supraglacial outwash sandur from the Isle of Man
Authors: Thomas G. S. P. , Connaughton M. , Dackombe R. V.
Published: July 2010

The Orrisdale Outwash Member was deposited during retreat of the Late Devensian Irish Sea ice‐sheet in a series of diachronous marginal sandur formed on an unstable, ice‐cored supraglacial topography. Sedimentation was controlled by dead‐ice ridges running parallel to the ice‐margin but as buried ice melted the topographic constraints diminished and individual sandur systems widened and coalesced. The sediments are characterized by very rapid lateral and yertical facies variation caused by channel migration, abandonment, and adjustment to a rapidly‐changing ice and sediment substrate. Facies assemblages consequently show marked lateral transition from high energy, laterally impersis‐tent, gravel dominated longitudinal bar sequences to extensive, low‐energy overbank flood basin successions.
The Late Devensian glaciation along the border of northeast Wales
Authors: Thomas G. S. P.
Published: July 2010

The glacigenic succession along the border of northeast Wales records the advance, coalescence and subsequent uncoupling of Welsh and Irish Sea ice‐sheets during the Late Devensian cold stage. During coalescence, extensive basal tills were deposited and considerable diversion of pre‐existing drainage was accomplished by subglacial meltwater. Analysis of borehole data and quarry exposure indicates that a complex assemblage of ice‐contact, proglacial fluviatile and lacustrine environments was developed during uncoupling and subsequent retreat. Neither of the previously proposed models for the formation of the so‐called Wrexham ‘delta‐terrace’ are adequate to explain the wide variety of sedimentary successions observed and the feature is a complex, diachronous structure that reflects rapidly changing depositionai conditions, including ice‐front alluvial fans, sandar and proglacial and ice‐contact lakes, formed at the margin of a retreating ice‐sheet.
INTAL–an expert system for the identification of igneous rocks in the hand specimen
Authors: Hawkes Donald D.
Published: July 2010

INTAL is an expert system which will identify igneous rocks in the hand specimen on the basis of a description given to the computer by an inexperienced geologist. It assumes only that the user can identify the common rock‐forming minerals and has a rudimentary knowledge of the jargon of an igneous petrographer. The computer has no control over the user's initial description, which is freely written in English, and only partial control over any subsequent interactive dialogue. INTAL is programmed in BASIC and may be used on a small microcomputer. The program works by repetitively scanning all user input for significant keywords until the attributes of a production rule are assembled and the rock is identified.
The Courceyan stratigraphy of the Pallaskenry Borehole, County Limerick, Ireland
Authors: Somerville Ian D. , Jones Gareth L. I.
Published: July 2010

The Pallaskenry Borehole, Co. Limerick, Ireland provides an almost complete Courceyan (Dinantian) succession from Old Red Sandstone facies up to Waulsortian limestones. A revised lithostratigraphic‐al nomenclature for this succession is presented. Examination of the conodont and coral faunas in the borehole has enabled biozones to be defined which can be recognized throughout the Limerick Province. Biostratigraphical correlations are made with Courceyan successions at Hook Head, Co. Wexford, in the Mendip Hills and in Knap Farm Borehole in the Southwestern Province of Britain. Conodont taxa show a clear distinction betweeen the shelf faunas of the Limerick Province, Hook Head and eastern Mendip, and distal shelf faunas from south Cork, Knap Farm and Dinant, Belgium, which probably reflect their different palaeogeographical positions.

Acknowledgements. The authors wish to express their thanks to Professor G. D. Sevastopulo, Drs. R. L. Austin, J. R. Nudds and P. Strogen and Mr. M. Mitchell for constructive criticism of the manuscript. We would also like to thank Dr. T. R. Reilly, Mr. C. McDermot and Dr. A. Sleeman of the Geological Survey of Ireland, and Dr. M. E. Philcox for fruitful discussion on the Iithostratig‐raphical nomenclature. G. LI. Jones was a Research Fellow at Trinity College, Dublin during the period of this work. He was funded through the Upper Palaeozoic Atlas of Ireland (UPAIR) Project, financed by the Department of Energy and administered through the Geological Survey of Ireland and Trinity College. He gratefully acknowledges the organization and supervision provided by Professors C. H. Holland and G. D. Sevastopulo and Dr. D. Naylor; and the assistance with conodont processing given by Ms. B. Thornbury. Thanks are also extended to Mr. J. Kennedy and Mr. P. Moffat for assistance with the diagrams.
The shipway limestone of gower: Sedimentation on a storm‐dominated early carboniferous ramp
Authors: Faulkner T. J.
Published: July 2010

A detailed sedimentary study of the Lower Carboniferous (Courceyan) Shipway Limestone Formation at Three Cliffs Bay on the Gower Peninsula (South Wales) has shown that the bioclastic limestones represent a storm‐dominated sequence that contains the storm‐related sedimentary structure hummocky cross‐stratification (HCS). Conformably overlying the Shipway Limestone is a cross‐stratified oolitic sandbody with evidence of subaerial exposure. Six sedimentary lithofacies are identified in these two formations which record a distal to proximal, shallowing‐upward trend that passes from beneath mean wave‐base to above fairweather wave‐base.

The shallow marine facies model constructed by Wu (1982) from his study of the Lower Carboniferous limestone sequences of South Wales is re‐evaluated. Modifications proposed for the model include the addition of two distal tempestite facies and a proximal oolite sand body. The Shipway Limestone and Brofiscin Oolite record the first major, basin‐wide, shallowing‐upward phase of the Lower Carboniferous in South Wales.
Pedogenic dolomites from the oolite group (Lower Carboniferous) South Wales
Authors: Searl Alison
Published: July 2010

Within the Lower Carboniferous Oolite Group of South Wales dolomites occur as 0.1 to 3 m thick stratiform bodies, sharply bounded against both underlying and overlying limestones. They contain rootlets and other plant remains and are often laterally equivalent to calcrete horizons. The dolomites are interbedded with thin coals and organic‐rich shales. In thin section a fine‐grained, xenotopic, slightly ferroan, inclusion‐rich ‘early’ dolomite forms a matrix to scattered moulds after ooids, shells, and evaporite minerals. The moulds are filled with ferroan calcite, early dolomite, and ‘late’ strongly ferroan saddle dolomite. The early dolomite is highly subzoned under cathodoluminescence whilst the late dolomite is nonluminescent. Whole rock analyses have δ18O = −5.95%, to −0.80%, and δ13C = +0.50%, to +2.80%. The early dolomite is believed to have precipitated from low sulphate, low Eh fluids within the waterlogged soil of a schizohaline coastal swamp. The late dolomite may also have formed within the pedogenic environment as a precipitate from highly evolved swamp waters, heavily enriched in organically‐derived compounds. Alternatively the later dolomite may have a hydrothermal origin as is more commonly associated with saddle dolomite.
High‐level peperitic sills in the English Lake District: Distinction from block lavas, and implications for borrowdale volcanic group stratigraphy
Authors: Branney Michael J. , Suthren Roger J.
Published: July 2010

Criteria by which such sills can be distinguished from block lavas include discordance and fault‐controlled geometry, vesiculation and homogenization of sediments adjacent to upper contacts, and the presence of pillows or peperites at upper contacts. Because sills do not always show these characteristics in the field, an extrusive origin for a sheet should be demonstrated and not assumed. However, it is not always possible to make the distinction, in which case the non‐genetic termsheetcan be usefully applied.

Field studies suggest that a substantial part of the Borrowdale Volcanic Group is composed of sills. Thus previously erected lithostratigraphic schemes may not correctly indicate the sequence of magmatic events, and the correlation of locally defined stratigraphies will not be possible until the regional importance of high‐level intrusive bodies has been established.
The North cotentin shear‐zone (Normandy‐France): Variscan mobilization of the cadomian basement and its palaeozoic cover
Authors: Dissler E. , Gresselin F.
Published: July 2010

Detailed structural analysis of the northern part of the Cotentin Peninsula provides evidence for major Variscan reworking of Proterozoic structures. Two stages in the regional evolution of the Variscan orogeny are distinguished: the Palaeozoic Siouville Syncline was formed before the development of a south‐facing ductile overthrust. This latter stage is dated as Carboniferous in age from its relationship with the synkinematic intrusion of the Barfleur granitic pluton.
The Distribution of Chadian and earliest Arundian strata in North Wales: Implications for Dinantian (Carboniferous) lithostratigraphy and palaeogeography
Authors: Davies J. R. , Riley N. J. , Wilson D.
Published: July 2010

The late Chadian Foel Formation, previously thought to be confined to the Dyserth area of North Wales, forms a poorly exposed but persistent basal unit to much of the Dinantian crop east of the Clwydian Range, necessitating a revision of the local lithostratigraphy. The formation comprises a peritidal heterolith which, together with the lowest few metres of the overlying Llanarmon Limestone, yields microfossil assemblages diagnostic of the Eoparastaffella Cf4α Subzone. Succeeding strata, containing the lowest archaediscid foraminifera, provide the first record of Cf4β assemblages from North Wales and establish an early Arundian age for these beds.

The Foel Formation was deposited as an aggradational sequence on the northern flank of St. George's Land during a pulsed transgression which began in late Chadian times. The widely recognized basal Arundian transgression is represented by the contact between the Foel Formation and overlying platform carbonates. The latter overlap the Foel Formation in the southernmost part of the Clwydian crop demonstrating, for the first time, southwards onlap on the northern side of the Bala–Bryneglwys Fault System.
Wrench faults, pull‐apart basins, and volcanism in central Oregon: A new tectonic model based on image interpretation
Authors: Gutmanis J. C.
Published: July 2010

A tectonic study of the Newberry Crater region of central Oregon has been based on the interpretation of Landsat Thematic Mapper imagery. Two major faults, the Brothers‐Tumalo and Eugene‐Denio Faults, pass NW‐SE through the region and step to the right at the eastern margin of the Cascades Range. Dextral wrench faulting on these structures during the Tertiary controlled the formation of the La Pine Basin, a pull‐apart structure containing Tertiary and Quaternary sediments and volcanics. Tertiary wrench faulting appears to have been associated with rotations of crustal blocks at a plate margin, but was superseded in the Quaternary by extensional faulting of the Basin and Range province. Newberry Crater and other major bimodal volcanic centres in the NW Cordillera (Crater Lake, Medicine Lake, Mt. St. Helens) seem to have a similar tectonic setting in crustal pull‐aparts. A relationship between magma type and fault trend at Newberry and Medicine Lake is suggested.
Palaeoecology and significance of barnacles in the mid‐Pliocene Balanus Bed of Tobago, West Indies
Authors: Donovan Stephen K.
Published: July 2010

The Balanus Bed of the Rockly Bay Formation (mid‐Pliocene) of Tobago is a sequence of orange‐brown sands with laterally equivalent muds. The invertebrate macrofauna is dominated by the balanid barnacle Megabalanus tintinnabulum (Linnaeus) sensu lato, with associated oysters, pectinaceans, gastropods, bryozoans, regular echinoids, and rare crabs and sharks. Vertical burrows in muddier substrates are good evidence that this assemblage was living littorally or shallowly sublittorially. Previous analyses of the Rockly Bay Formation of the type area have erroneously suggested that it represents a lenticular deposit. It is now recognized to be a transgressive unit, unconformable on the underlying Mesozoic basalts. The sediment of the Balanus Beds was derived from the in situ weathering of basalts, producing a gradation from sandy (near shore) to muddy substrates. Balanids grew singly on the weathering basalt, but suitable substrates for attachment in the muddy environment were rare, so barnacles are found clustered in close association. The primary substrates for attachment in the muddy environment were disarticulated balanid plates, mollusc valves and small pebbles. Although the base of the Formation is not seen in Rockly Bay, a basal conglomerate overlain by a horizon of dissociated valves of the large ark Anadara patricia (Sowerby) is exposed in nearby Little Rockly Bay. Apart from the two fossiliferous horizons mentioned, the Formation is barren of marine microinvertebrates. The Rockly Bay Formation appears to have formed in response to the mid‐Pliocene rise in sea level. Horizons dominated by balanids may be useful indicators of sea‐level rise, at least in the Neogene, Darwin's ‘Age of Barnacles’.
Magmatic evolution of the Løkken SSZ Ophiolite, Norwegian Caledonides: Relationships between anomalous lavas and high‐level intrusions
Authors: Grenne Tor
Published: July 2010

The Lower Ordovician Løkken ophiolite fragment shows a tripartite subdivision of its thick volcanic sequence into: (1) an Upper Volcanic Member (UVM) of transitional MORB/IAT character, comprising basalts or, in a related, thrust‐bounded sequence, a bimodal basalt‐rhyolite assemblage; (2) a Middle Volcanic Member (MVM) derived from widely variable, generally MORB‐related magmas; and (3) a Lower Volcanic Member (LVM) of N‐type MORB basalts which locally passes into an underlying sheeted dyke complex. The UVM and LVM were fed from relatively deep‐seated magma chambers, and lavas were erupted at moderate flow rates to form predominantly pillow lavas. The whole sequence is interpreted as having formed in a marginal basin setting.

The MVM is characterized by abundant voluminous sheet basalts thought to have been erupted at high flow rates. The volcanites had their source, through extensive dyke swarms, in high‐level magmas which intruded the sheeted dyke complex and parts of the LVM, possibly in a near‐axial seamount setting. The magmas differentiated to form plagiogranitic melts, with a wide range of conjunctive, mafic to intermediate cumulates. This plutonic assemblage, possibly in crystal mush form, was subsequently intruded by new, mafic magma, leading partly to large‐scale remelting or assimilation of cumulus phases. These processes are reflected in the MVM by common hybrid flows, as well as local intermediate lavas having the geochemical characteristics of cumulates, erupted during a period of intense faulting. Major tapping of the primary, mafic magma occurred toward the end of the period of MVM volcanism. A predominance of voluminous, apparently fluid, massive flows in the MVM is mainly ascribed to the shallow depth of magma reservoirs.