bluuebunny/crossref_metadata_2025_split 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

AbstractField 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

AbstractThe 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

AbstractNew 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

AbstractSeabed 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractTrace 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

AbstractThe 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

AbstractEvidence 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

AbstractThe 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

AbstractNepheline 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

AbstractRelict 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

AbstractBrachiopod‐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

AbstractThree 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

AbstractExaminations 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.
Geophysical down‐hole recognition of the Lower Devonian‘Psammosteus’Limestone and Townsend Tuff Bed, South Wales
Authors: Tunbridge I. P. 
Published: July 2010

AbstractGeophysical 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

AbstractThe 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

AbstractThe 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

AbstractThis 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

AbstractTrace 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.