bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geophysical investigations of the sea floor
Authors: Mason R. G. 
Published: February 2007

AbstractSeismic refraction measurements show that the earth's crust thins from about 35 km. under the continents to 6 km. under the oceans, also that the oceanic crust has a layered structure. The sediments that cover it are much thinner than expected, which suggests that the oceans are perhaps younger than was thought, or perhaps the sediments have become engulfed in lavas. Great fracture zones cross the floor of the north‐east Pacific and there is evidence for strike‐slip movements of more than 200 km. along them. The discovery that heat flow rates for continents and oceans are approximately equal upsets previous ideas about radioactive heat sources. A pattern has been observed in the heat flow associated with an oceanic rise. It has been suggested that both are related to convection in the mantle. Subcrustal drag by convection currents may explain the fracture zones.
The history of Chirotherium
Authors: Swinton W. E. 
Published: February 2007

AbstractCheirotherium was the name given to a hand‐like imprint believed in 1835 to be a mammal. Similar footprints have long been found in Cheshire and much work was done by J. Lomas and H. C. Beasley upon them. The genus is now known to occur in America as well as in Europe and 34 species have been described. The history of discovery, the validity of species, and the classification are discussed here. The animal that made the prints is identified as a pseudosuchian reptile.
The succession and structure of the Borrowdale volcanic rocks Northwest of Ullswater
Authors: Moseley F. 
Published: February 2007

AbstractThe succession consists of Skiddaw Slates followed by Borrowdale Volcanic rocks (Ordovician) and is very similar to that previously described southeast of Ullswater (Moseley 1960). The Ullswater Group, more than 4000 ft thick forms the lowest part of the volcanic succession and consists of tuffs, basalts, basic andesites, and andesites. Above this about 1000 ft of the rocks of the Birk Fell Group, which are dominantly felsitic, are exposed.Important structural elements are the Ullswater Anticline, the Ullswater Thrust and the high angle faults. The anticlinal axis follows Ullswater as far as Glencoynedale and can be demonstrated only in the Borrowdale Volcanic rocks. The anticline does not appear to continue downwards into the Skiddaw Slates which are not only of different tectonic facies to the volcanics, but are separated from them by the southeasterly dipping Ullswater Thrust. This thrust was induced by the disharmony between the competent volcanics and the incompetent Skiddaw Slates, and is thought to be an imbricate thrust complex rather than a single dislocation.The high angle faults, the third important structural element, have northwest, northerly and westerly trends. It is probable that the northwesterly faults, at least, are wrench faults, although a strike slip component can be demonstrated in one instance only. The nature of the movement of the northerly and westerly faults cannot be ascertained.
Deformed acid intrusions in the Manx Slate Series, Isle of man
Authors: Simpson Alexander 
Published: February 2007

AbstractPrevious research by the present author has established the Caledonian polyphase tectonics (F1, F2, F3) of the Manx Slate Series. Emplaced along the bedding or the first axial‐plane cleavage (S1) in these strata, and confined to a relatively narrow belt following the middle of the island, is a swarm of acid sheets which dip steeply and strike to the northeastern quadrant. Associated with these minor intrusions in the northeast of the island is the small Dhoon granite. The latter appears to have the form of a thick, lenticular sheet emplaced along S1 and inclined steeply southward.All these intrusions are post‐F1 in age. The field and textural evidence demonstrates their syn‐tectonic emplacement close to the hinge of the large‐scale F2 Manx synform near the beginning of the F2 episode. The strong deformation which they display was largely acquired during the F2 movement. This includes shearing parallel to the margins of the intrusions, penetration by the second axial‐plane cleavage (S2), flexuring by minor F2 folding and injection by syn‐tectonic F2 quartz‐veining. The F3 phase has also left a mild imprint upon the deformed intrusions.
The stratigraphy and composition of the Latterbarrow and Redmain sandstones, Lake District, England
Authors: Allen P. M. , Cooper D. C. 
Published: February 2007

AbstractThe Latterbarrow Formation, 400 m thick, has been mapped and subdivided informally into three members. These consist of quartz wacke sandstone and, in the upper member only, intercalated mudstones. The formation unconformably overlies the fossiliferous Skiddaw Group of late Tremadoc to middle Arenig age and is overlain disconformably by volcanic rocks that have been attributed to the Borrowdale Volcanic Group. Chemically, the sandstones are characterized by very low concentrations of CaO, Na2O, and K2O and unusually high total iron. MnO and MgO, such that iron, as Fe2O3, exceeds Al2O3. Mudstone in the upper member is illite rich, has a high K2O content and is compositionally similar to K‐bentonites derived from volcanic ash. Sedimentary structures and petrography suggest that the sediments were deposited in a sandy estuary and were derived from a similar source area to that of the Skiddaw Group. Throughout the succession there is evidence of distal volcanism, probably representing the earliest eruptions of the Borrowdale volcanic episode.The Redmain Formation, 100 m thick, is unconformably overlain by Carboniferous rocks but its relationship to the underlying Skiddaw Group is unknown. Though this lithic arenite shows some petrographic and geochemical similarities with the Latterbarrow sandstone, differences are such that it is possible they are not equivalent in age. The Redmain sandstone may be derived from the erosion of Skiddaw Group rocks.
Petrology, structure and age of the Rough Point sill, Donegal
Authors: Elsdon R. 
Published: February 2007

AbstractThe Rough Point sill, which is one of the thickest of a large number of sills intruded into the Appin Group metasediments of the Dalradian sequence in north Donegal, contains a number of internal features including mafic:felsic banding, pegmatite bands and significant variations in grain size. There are also appreciable variations in mineralogy, particularly the proportions of plagioclase and amphibole, and in the major and trace element chemistry. Together these features indicate that the sill is, like the metasediments which it intrudes, inverted, and is therefore older than the Caledonian F2 structures which caused the inversion. Disruption of the sediments at the sill contact is also earlier than the F2 event. The timing of the basic magmatic episode together with the geochemistry of the sill invite comparison with the metadolerites of the southwest Highlands of Scotland.
Stratigraphic approaches to hydrocarbon exploration and exploitation
Authors: Mazzullo S. J. 
Published: February 2007

AbstractThe stratigraphic approach toward hydrocarbon exploration and exploitation is a fundamental aspect of the continued development and consequent future addition of new reserves from mature basins. This approach, albeit not novel, involves systematic attempts at locating subtle stratigraphic reservoirs and traps, as well as methods of enhancing hydrocarbon recoveries from existing fields, by coordinating petrophysical studies and conventional subsurface mapping techniques.
The formation of large diameter plant fossil moulds and the Walton theory of compaction
Authors: Thomas Barry A. 
Published: February 2007

AbstractHollow plant organs can react in different ways to the forces exerted during compaction of the surrounding sediments. Large infilled lycophyte stems, lying flat in the sediments, flatten and expand in width. The width of the mould that is ultimately formed will therefore approach half the original circumference of the stem rather than being equal to its original diameter.
The Pyroclastic deposits of Mount Etna volcano, Sicily
Authors: Chester D. K. , Duncan A. M. , Guest J. E. 
Published: February 2007

AbstractThroughout most of its geological evolution Etna has been characterized by the eruption of lava flows of a predominantly hawaiitic composition, but within the stratigraphical record there are four major sequences of pyroclastic materials: the Acireale tephra and lahars (˜100000 B.P.); the ‘lower tephra’ and Milo lahars (both ˜26000 B.P.); the Biancavilla ignimbrites (15–15500 B.P.) and the ‘upper tephra’ (˜5000–6000 B.P.). This paper reports investigations carried out on these deposits in order to determine their stratigraphy, petrology, sedimentology, and likely origins. Whereas the Biancavilla ignimbrites were generated when a more evolved, gas‐charged magma (benmoreite) was being produced by the volcano, the other suites of pyroclastic deposits were erupted from hawaiitic magmas—similar to those that have characterized the volcano during historical times. These deposits resulted from two processes: violent strombolian activity producing lapilli‐rich. coarse, but well‐sorted sediments, and hydrovolcanism when the mixing of water and magma in the conduit, brought about more violently explosive activity, giving rise to highly fragmented, poorly sorted, airfall tephra and lahars. Conditions favouring hydrovolcanism occurred at times in the volcano's history when palaeoenvironment and palaeogeography were conducive to the retention of large amounts of surface and subsurface water. Although climates favouring the retention of water at high levels on the volcano have occurred on many occasions in the history of the volcano, at ˜26.000 and ˜5000‐6000 B.P. these occurred in conjunction with a construct of sufficient height and suitable configuration to allow storage of water and give rise to hydrovolcanic activity. The nature of the mechanisms responsible for the emplacement of these hydrovolcanic deposits is considered and it is concluded that airfall is the most probable process. Finally, the implications of this research for the assessment of hazard are reviewed.
The Structure and Stratigraphy of the Western External Sierras of the Pyrenees, Northern Spain
Authors: Nichols G. J. 
Published: February 2007

AbstractThe External Sierras of the southern Pyrenees represent the frontal thrust complex of a south Pyrenean thrust sheet which was active from the late Eocene to early Miocene. Triassic, Cretaceous and Eocene limestones, sandstones and mudstones involved in this thrusting can be divided into eight mappable units. Mapping and the construction of serial sections across the Western External Sierras show that the amount of southward translation of the thrust sheet increases eastwards from the thrust tip. There is an increased slip of at least 5km along 30km of the External Sierras. Structures show a progressive development from a “primitive” form in the west to a more complex thrust and fold geometry in the east. The general pattern is one of thrust and fold development in response to compression from the north. Backthrusting has occurred on the forward side of the frontal thrust complex. These backthrusts cut up section towards the north and form triangle zones where they intersect thrusts which cut up sections towards the south. The latest thrust movements deformed early Miocene fanglomerates and were out‐of‐sequence reactivations of earlier thrusts.
The age of the Oughterard Granite, Connemara, Ireland
Authors: Kennan P. S. , Feely M. , Mohr P. 
Published: February 2007

AbstractDespite a wide latitude for interpretation of previous Rb–Sr isotopic data on the Oughterard Granite the age of this intrusion has been regarded as a critical time‐marker in resolving the Caledonian evolution of Connemara. New isotopic data suggest that the age of the intrusion be revised from c. 460 Ma to c. 400 Ma, thus making the Oughterard Granite one among the many Newer Caledonian Granites in Ireland. The preferred age is 407 ± 23 Ma, and the initial 87 Sr/86Sr ratio is 0·7076 ± 1. Heterogeneity within the granite is demonstrated, which explains the difficulty in obtaining reliable isotopic ages from this intrusion.
Metamorphic carbonate–mafic amphibolite interactions from Arinteiro, northwest Spain
Authors: Williams Patrick J. 
Published: February 2007

AbstractSome contacts between interlayered marbles and amphibolites at the Arinteiro copper mine are associated with zoned metasomatic calc‐silicate assemblages. Textures indicate that formation of the calc‐silicate zones involved mass transfer over distances up to 15 cm and that pore fluid solution (infiltration) may have been a significant reaction mechanism. The sequence of minerals is very similar to previously described products of metasomatic interactions between marbles and pelites. Similar metasomatic processes involving primary concentrations of carbonates can be invoked to explain the common occurrence of zoned calc‐silicate patches and folia in metaigneous amphibolites both near Arinteiro and in other terrains.
Sr‐Nd isotope compositions of cenozoic granitoids along a traverse of the central Peruvian Andes
Authors: Soler Pierre , Rotach‐Toulhoat Nelly 
Published: February 2007

AbstractSr‐Nd isotopic compositions of late Eocene to Pliocene intrusive rocks from a traverse (⋍11° lat. S) of the central Peruvian Andes are presented. The data set suggests that the calc‐alkaline magmatism is mainly the end‐product of the evolution at deep crustal levels of magmas derived from a slightly depleted, but not MORB‐type, subcontinental mantle, which have assimilated crustal material and have mixed with new batches of primary magma. Assimilation of crustal material increased eastwards and with time. The evolution of Sr‐Nd isotope compositions in time and space along the traverse reflect both the lateral heterogeneities in the subcontinental mantle, the lower crust composition, and the progressive tectonic thickening of the crust during the Cenozoic. No granulitic basement akin to the early Proterozoic south Peruvian Arequipa massif has participated in the genesis of the central Peruvian calc‐alkaline and alkaline magmas.
A sulphur isotope study on selected Caledonian granites of Britain and Ireland
Authors: Laouar R. , Boyce A. J. , Fallick A. E. , Leake B. E. 
Published: February 2007

AbstractA sulphur isotope study was carried out to assess the value of such isotopic data in constraining the contributions of igneous and sedimentary protoliths for British and Irish Caledonian granites. Conventional separation techniques yielded sulphides from only 19 of the 50 selected granites, including both Newer and Older intrusions. These sulphides are dominated by pyrite, with lesser pyrrhotite, and rare chalcopyrite.Two groups emerge from consideration of δ34S in conjunction with δ18O, initial 87Sr/86Sr (ISr) and age; Group I have δ18O generally < + 10·5‰, ISr in the range 0·703 to 0·708, and are younger than 435 Ma. δ34S of this group ranges from −4·5‰ to +4·4‰ x̄ = +0·7 ± 2·6‰ (n=40:1σ). Group II have δ18O generally > + 10·5‰, are generally older, ISr between 0·710 and 0·7208, with δ34S in the range +6·2‰ to +16‰: x̄ = +9·5 ± 3·3% (n = 13:1σ). The source region for group II granites contained a significant sedimentary component.Since sulphides in Lower and Middle Dalradian metasediments are characterized by unusually high δ34S values, between +11‰ and +17‰. we suggest that group II granites contain a significant proportion of sulphur derived from these rocks.
Desilication of Caledonian granites in the Barnesmore complex, Co. Donegal: The origin and significance of metasomatic syenite bodies
Authors: Dempsey C. S. , Meighan I. G. , Fallick A. E. 
Published: February 2007

AbstractThe ca. 400 Ma Caledonian Barnesmore complex, Donegal, includes a 1·5 km2 area in the Main Granite (G2) in which pristine biotite monzogranite has undergone in situ alteration to brick‐red, two feldspar, chloritic syenite which is virtually quartz‐free. The principal chemical changes involve major elements (Si, Al, Ca, Na, K) rather than trace elements. Stable isotope mineral data (O, H) show essentially magmatic values. It is proposed that a silica‐under‐saturated, volatile (halogen?) — and alkali (+Al)‐enriched, late‐stage, aqueous magmatic fluid was channelled into vertical conduits, dissolving quartz, precipitating feldspar(s) and disrupting the fabric of the host granite. The resulting syenitic bodies and vents exposed elsewhere in the complex are believed to represent different levels in such pipes. The mineralogical and chemical modification recorded here has important implications for the study of granitic rocks elsewhere in the world in that more subtle degrees of alteration may have escaped recognition and other equally drastic examples may have associated mineralization potential.
Microgranular enclaves as indicators of hybridization processes in granitoid rocks, Hercynian Belt, Spain
Authors: Castro A. , Moreno‐Ventas I. , de la Rosa J. D. 
Published: February 2007

AbstractMany Hercynian granitoids of calc‐alkaline composition are characterized by the presence of microgranular enclaves of tonalite to diorite composition. Though some differences in size, shape, and relative abundance of the enclaves are observed between deep‐seated, high‐level, and subvolcanic plutons, there are considerable similarities in texture, grain size, and composition. In magma interaction zones where basic and silicic magmas mingled, enclaves were generated from the disruption, by convective flow, of synplutonic dykes of basic, fractionated, perhaps hybrid, magmas. Many enclaves can be interpreted as non‐consolidated portions of basic magma in thermal equilibrium with the host granitoid. Under such condition, enclaves are easily disaggregated and mixed with the host granitoid, contributing to the hybridization of the latter. The process implies the development of special textures in both enclave and host granitoid, and may be tested by chemical variations and correlations, suggesting that the presence of enclaves, with these particular textures and compositions, may imply that a form of hybridization was involved in the genesis of the host granitoids.
The devonian and carboniferous volcanism of the peloritan mountains (sicily) and the evolution of palaeozoic basins in the calabrian‐peloritan arc
Authors: Acquafredda P. , Lorenzonis S. , Lorenzoni E. Zanettin 
Published: February 2007

AbstractVolcanic rocks from three Palaeozoic low‐grade metamorphic sequences of different age from the Peloritan Mountains, Sicily, have been analysed for major and trace elements. On the basis of the relative abundances of certain comparatively immobile elements (especially Zr, Ti, Nb, and Y) the petrogenetic affinities of the volcanic rocks in each area have been established. The Fiumara Fitalia sequence contains Lower Devonian within‐plate alkaline basalts, the Ogliastrello sequence contains Upper Devonian continental within‐plate calc‐alkaline basalts and the Randazzo‐Floresta road sequence contains Lower Carboniferous calc‐alkaline basalts probably of island arc affinity.When account is taken of their stratigraphic positions, geochemical characteristics of the volcanic rocks indicate Devonian extensional conditions and Lower Carboniferous compressional conditions. Evidence for Lower Devonian extension is present in several circum‐Mediterranean basins (i.e. Calabria, Sardinia, Carnic Alps). In the Peloritan Mountains, as well as in Calabria and Sardinia, extensional conditions were already present in the Cambro‐Ordovician. The compression in the Calabrian‐Peloritan Arc was probably related to a period of subduction during the Hercynian orogeny and resulted in the closure of the basins in the Carboniferous.
Genesis of lithium pegmatites from the leinster granite margin, southeast ireland: Geochemical constraints
Authors: O'Connor P. J. , Gallagher V. , Kennan P. S. 
Published: February 2007

AbstractExtensive and economically‐important lithium pegmatites have been described from the eastern flank of the large S‐type peraluminous Leinster Granite batholith in southeast Ireland. This flank area is also the locus of a major dip‐slip ductile shear zone which was active during emplacement of the Tullow Lowlands pluton of the batholith. All the known bedrock occurrences of lithium pegmatite are contained within this marginal deformation zone.Most previous studies have suggested derivation of the lithium pegmatites by fractionation from the Leinster Granite itself, though none are conclusive. More recently, an anatectic model has been proposed whereby the pegmatites were derived by melting of Li‐rich sediments adjacent to the batholithic contact. Our investigation has been concerned with a detailed study of the Rb‐Sr isotope systematics and trace element geochemistry of the pegmatites and their host granitoids in an attempt to resolve the problem of pegmatite genesis.The results suggest a strong geochemical and temporal coherence between the Leinster Granite and the lithium pegmatites. A model is proposed in which Li enrichment in residual magmas may be linked to the development of muscovite instead of biotite in the Leinster Granite itself. The Li excluded from entry to biotite then accumulates in highly mobile, low‐viscosity pegmatitic fluids which migrate into the marginal shear zone of the Tullow Lowlands pluton where they crystallize at considerably lower temperatures.
Depositional and tectonic relationships of upper ordovician and lower silurian strata around dinas mawddwy, mid‐wales
Authors: James D. M. D. 
Published: February 2007

AbstractThe field evidence for the lateral impersistence of the Garnedd‐wen Formation (Hirnantian) and Derwen Formation (Aeronian) immediately northeast of Dinas Mawddwy is reviewed and the evidence for strike faulting as inferred by W. J. Pugh (1928) is reassessed. It is concluded that little if any strata are missing and that surfaces of non‐deposition, rather than fault cut‐out, better explain any strata that are locally abnormally thinned. However strike faulting is newly proven west of Dinas Mawddwy and accounts for much of the rapid apparent thickness variation in the Broad Vein (Rawtheyan) there. The newly constrained thickness estimates strongly imply that sedimentation was influenced by a basement fracture at Dinas Mawddwy. Structural reasoning and palaeocurrent evidence from the Garnedd‐wen Formation suggest that this fracture probably parallels the Corris‐Llangranog fracture to the southwest.
Reversals in the polarity of structural facing across an early ductile thrust; the Central Donegal Slide, northwest Ireland
Authors: Alsop G. I. 
Published: February 2007

AbstractThe Dalradian succession of central Donegal represents a tectono‐stratigraphic sequence everywhere separated into two distinct successions by the Central Donegal Slide. Each stratigraphic package consistently youngs away from this major D1structure which originated during lower greenschist facies metamorphism and corresponds with the development of locally preserved penetrative S1fabrics. The tectonic slide and associated reversal in the direction of structural facing are commonly marked by mylonites and tectonic schists, which have been subsequently folded and reactivated by kilometric‐scale sheath folds and the Ballybofey Nappe.Structural correlations with northwest Donegal suggest that the Central Donegal Slide relates to the Knockateen Slide, and represents an early thrust with top to the northwest sense of shear. The Central Donegal Slide cuts up‐section through the Middle Dalradian sub‐basin centred on southern Donegal, emplacing younger, anoxic basinal sediments and turbidites over an older, inverted, shelf succession. The location of the Central Donegal Slide adjacent to the margin of this sub‐basin suggests that the siting and form of ductile thrusts may be strongly influenced by the geometry of the pre‐existing sedimentary basin.