bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Lundy Complex: Its petrology and tectonics
Authors: Dollar Archibald Thomas John 
Published: October 2009

The Lundy igneous complex projects through the Palaeozoic floor of the Bristol Channel at a point 24 miles due west of Ilfracombe, North-West Devonshire. Its subaerial part lies about the intersection of parallel 51° 11′ N., and meridian 4° 40′ W.
Unique alike in structure and composition among insular masses of the Severn estuary, it affords evidence of former crustal weakness and associated vulcanicity in a region situated near both the northern boundary of the Cornubian Permo-Carboniferous igneous province, and the southern boundary of the Hebridean Tertiary igneous province.
It is a composite block of alkaline granites intruded among contorted slates, altered calcareous grits and thin marbles, with a swarm of basic, intermediate and acid dykes cutting both granites and sediments in a dominantly north-westerly direction. Erosion of the resulting complex has reached a stage such that only Lundy Island, the central and eastern part of its rugged core, now remains above sea-level. This core rises abruptly from an irregular base of uncertain submarine extent to a maximum height of 47·5 feet above mean sea-level. From north to south its subaerial length is 3·1 miles; its average width is 0·6 miles, and its superficial area is nearly 1·7 square miles. Of the subaerial volume approximately 91·4 per cent is granite and microgranite; 6·4 per cent is altered sediment and 2-2 per cent is dyke-rock. The island is surrounded by an indented shore-line with steep cliffs, the latter being united to an undulating table-land at 350 feet above mean tide-level by
Stratigraphy and Structures East of Oxford
Authors: Arkell William Joscelyn 
Published: October 2009

I. I
ntroduction

T
he
Geological Survey 1-inch map of Oxford (1908) shows to the east of the city a remarkable belt of faults, running from north-west to southeast for 12 miles and passing at its nearest point within three miles of Magdalen Bridge. Starting in the Great Oolite and Forest Marble of Islip, the faults cut through the Corallian rocks between Elsfield and Beckley and bound the Corallian limestones of Wheatley. They also shift the Kimeridge Clay, Portland Beds and Shotover Sands of Forest Hill, Great Milton and Great Haseley, as far as the margin of the overstepping Gault.

Closer inspection of the map makes it clear that these are by no means simple faults. In fact, no satisfactory interpretation of the structure is possible from the arrangement of outcrops and faults shown on the map. The explanatory memoir (1908), by T. I. Pocock, H. B. Woodward, and G. W. Lamplugh, contains no chapter on structural geology. There are, however, scattered references to structure in the stratigraphical chapters, and these were reproduced without alteration in the second edition (Pringle 1926 1). The authors referred to trough-faulting with displacements of 200 feet and 80 feet, to step-faulting, and to a " general Hne of fracture and displacement " which " owing to the meagre field-evidence, could not be deciphered in detail ". No mention was made of folding, and for the most part the mapping shows that none was envisaged.
In the light of experience gained in mapping other “lines of
Intrusive rocks of the Shelve area
Authors: Blyth F. G. H. 
Published: October 2009

In the discussion on the above paper Professor W. G. Fearnsides said that the " abundance of separated jointed blocks and heavy scree on the south-east side [of Corndon Hill] and comparative absence of litter towards the west required an explanation ". To the writer this appears to be a geomorphological problem directly related to the glacial conditions which prevailed during Pleistocene times, an aspect which was not discussed at the reading of the paper.
The distribution of drift in the Welsh Borderland has much in common with that of the Isle of Man, both local and extra-insular drift being involved. In the words of Lamplugh (Geol. Surv. Mem. Isle of Man, 1903, p. 352), "Their relative distribution is everywhere in keeping with Mr. Kendall's supposition that only the lower layers of the ice-sheet were drift-laden, and that these were diverted by the steeper hill slopes and swept round the flanks of the massif as an undercurrent."

Applying this principle to the Shropshire area, it is clear that hills such as Corndon and the Breidden, to select two examples, must for long have remained as outstanding
nunatakkr
similar to those of the Nordenskiöld Glacier of Spitsbergen at the present day. Their western or ice-ward flanks were directly exposed to the oncoming Welsh ice, although the pure upper ice would have little abrasive power. The eastern or leeward flanks were zones of pluck, a process responsible for the disintegration and removal of the rock-face from top to bottom during the progressive
The stratigraphy, structure and mineralization of the Greenhow mining area, Yorkshire
Authors: Dunham Kingsley Charles , Stubblefield Cyril James 
Published: October 2009

Summary

The primary object of the work was the investigation of the geological environment of the galena-fluorite-barite deposits. The Carboniferous Limestone Series, over 1400 feet in maximum thickness, was mapped in six divisions covering faunal horizons from ?C
2
S
1
up to and possibly above D
2
. The Millstone Grit Series rests unconformably on horizons from the
Davidsonina
[
Cyrtina
]
septosa
band in D
1
up to beds with
Orionastraea
, the relations being ascribed to a pre-Millstone Grit uplift, possibly domal in form, accompanied by faulting. Within the Millstone Grit the "Top Limestone" (renamed the Cockhill Limestone) was proved to be characterized by
Cravenoceras cowlingense
(E
2
). Two higher marine horizons, well known elsewhere, were established here by many exposures : the Colsterdale Marine Beds, characterized by
Cravenoceras nitidum
(E
2
), seen in the same section as the Cockhill Limestone, and the glauconitic Cayton Gill Beds. A structure-contour map based on horizons in the Millstone Grit mapped at surface and underground shows that the anticline in the southern part of the area, trending east-north-east, has an amplitude of about 1000 feet, and that a series of domes and basins have been developed along its crest. The North Craven Fault, runniilg along the southern flank of the anticline, is a complex fracture-belt enclosing a tight syncline in the western part of the area, degenerating eastwards into a small strike-fault. The eastern half of the Bycliffe Vein-system is mineralized up to the Cayton Gill Beds but the remaining veins are mineralized only in the Carboniferous Limestone. The most important ore-shoots are found in the upper division of D
l
, in limestone underlying either shales low in the local D
2
or the basal shale of the Millstone Grit, depending on the position of the unconformity. Less important ore-shoots are found at various horizons from ?C
2
S
1
up to D
1
. It is suggested that extension of mineralization in depth beyond the limits so far revealed is possible in the case of ore-shoots related to shale overlying D
1
limestone. There is a crude zonal arrangement of minerals. Palaeontological notes are included on
Hederella
cf.
chesterensis
(of a suborder new to Britain) and on two new forms,
Productus (Eomarginifera) tissingtonensis cambriensis
and
Eumorphoceras bisulcatum grassingtonensis
.
The Arvonian rocks of Arvon
Authors: Greenly Edward 
Published: October 2009

Summary

The Arvonian formation consists, in situ, of a granite, a quartz-rhyolite, and a pyroclastic series, but other members were formerly present. The granite, very coarse at Caernarvon,
1
slowly grows finer eastward, until it graduates into the rhyolite. There are coarse agglomerates, and three groups of finer tuffs. In all, nine members can be distinguished, and there is an order of superposition. Is the formation Cambrian, or is it somewhat older, with a measure of unconformity ? Balance of evidence seems to be in favour of unconformity. Correlation is considered, though very cautiously, with Uriconian and Pebidian.

The term " Arvonian " was proposed by the author in 1930 (
Geol. Mag.
lxvii, 1930, p. 287) to denote the ancient volcanic series of the country between the Menai Strait and Snowdonia, which comprises the well-known rhyolite of Llyn Padarn, the rhyolite between Bangor and Caernarvon, and the pyroclastic rocks of Bangor itself. When originally described, the formation was referred to as the " Bangor Volcanic Series ", but in the course of the recent detailed survey it was found to be very much more extensive than was formerly recognized, occupying indeed as much of Arvon as its other three major formations combined (Fig. 1). The thickness of the Arvonian formation is great, and its importance in the early volcanic history of Britain is second only to that of the Mona Complex.

The formation appears to be entirely igneous, for no sedimentary rocks have been found. In situ at the present time it
On some new Permian fossils from the Magnesian Limestone near Sunderland
Authors: Trechmann Charles Taylor 
Published: October 2009

Summary

Practically all the species of invertebrates in the Permian of England had been discovered before 1850, almost the only exception being the record of
Chonetes davidsoni
in 1864, from the Lower Magnesian Limestone at Hartley's Quarry west of Sunderland. The present paper deals with some new occurrences in these beds rather farther to the west, at Ford Quarry, Claxheugh, 2 miles west of Sunderland. They include two new species of
Chonetes
, one of which resembles a Spitsbergen form, a
Camarophoria
apparently identical with
C. purdoni
of the Russian and Himalayan Permian, and at least two lamellibranchs with Russian and German affinities. The early collectors paid little attention to the vertical or lateral distribution of their fossils; in the middle beds most of the fauna is crowded in a line of reef knolls in which the species die out progressively upwards. Among other localities, the classical knoll of Humbleton Hill has been re-examined, and at the top, facing west, a dolomite with the impoverished fauna, only three genera of Brachiopoda, has been found. The thrusts and other abnormal junctions of the Permian of North-East Durham have been re-investigated and their possible connexion with solution of sulphates and with faunal and reef-knoll distribution is mentioned.
The Geology of the Prescelly Hills, North Pembrokeshire
Authors: Evans William David 
Published: October 2009

Summary

The Ordovician rocks of this district range from the Arenig to the Bala, with the succession generally ascending northwards. The rocks usually possess a Caledonoid strike and are disposed about two eastwardly pitching anticlines and a complementary syncline, which are dislocated by faults and overthrusts to the south-east. The Sealyham Volcanic Series is composed of rhyolites and tuffs in the western part of the area, but in the east the formation is almost entirely represented by trachytes. The
Didymograptus bifidus
beds occupy nearly the whole of the Prescelly Hills and they are mainly composed of shales and mudstones. The Fishguard Volcanic Series consists of fine-grained spherulitic and flow-brecciated rhyolites with thick beds of tuffs and local developments of ashy shales and mudstones. Sills of quartz-dolerites (among them the “spotted dolerite” which has been described as the analogue of the blue-stones of Stonehenge) and a single intrusion of a keratophyria rock occur in the Arenig and Llanvirn rocks but do not penetrate the shales, mudstones and sandstones of the Llandeilo and Bala formations. Petrographic descriptions of the igneous rocks are given, as well as a figure illustrating the stratigraphical correlation of the beds with those of other areas.
The gabbroic complex of Belhelvie in Aberdeenshire
Authors: Stewart Frederick Henry 
Published: October 2009

Summary
The Belhelvie igneous complex is a mass of basic and ultrabasic rocks, exposed over an area of about seven square miles, which intrudes and metamorphoses sillimanite-cordierite-gneisses and quartzose gneisses of the Dalradian Series. It is younger than the regional metamorphism of the gneisses and older than a patch of Old Red Sandstone conglomerate exposed near the intrusion. The general succession of rock types from west to east is : dunite-serpentine and peridotite, troctolite, hypersthene-gabbro, olivine-gabbro, and end-stage derivatives of olivine-gabbro and hypersthene-gabbro. The main conclusions reached in this paper have been derived from a study of this succession and of small-scale rhythmic banding and allied structures shown by many of these rocks. The evidence indicates that the various rock types have been formed largely by differentiation in place by crystal settling under the influence of gravity, and that at Belhelvie a section is exposed through a layered concordant mass similar in many respects to the large layered intrusions of Bushveld type. Study of the primary banding has led to the conclusion that the mass may have been tilted considerably since its consolidation, so that the bands have a nearly vertical dip. An alternative suggestion—gravity differentiation in another chamber and intrusion in a mushy state—is not supported by the petrological evidence, but the question must remain open until more knowledge is available of the structures of the gneisses of this part of Scotland.
At the eastern side of the complex is a large area of uralitized derivatives of olivine-gabbro and hypersthene-gabbro, and the more normal rocks to the west have been uralitized in many places. This uralitization is considered to have been due to the action of end-stage liquids or vapours (introducing water and silica) from the basic magma. Serpentinization of olivines is widespread, and microscopic evidence indicates that the main serpentinization took place before the main uralitization, and that both were preceded by the development of hornblende-spinel reaction rims round the olivines.
Intraformational Contorted Rocks in the Upper Carboniferous of the Southern Pennines
Authors: Cope F. W. 
Published: October 2009

An occurrence in Ireland similar to those described by Mr. Cope from the southern Pennines seems worthy to be placed on record. In the face of the large quarry at Noughaval, Co. Clare (1-inch sheet 123, 6-inch Clare 9) there is a band of contorted shale about nine to twelve inches in thickness lying between beds of undisturbed black shale some three feet above a bed of phosphorite, which in turn is a few feet above the top of the Carboniferous Limestone. The phosphorite is supposed, from the associated goniatites, to lie very near the R and H zones of the Millstone Grit; so that the stratigraphical position of this bed is comparable with that of some of Mr. Cope's examples. The general dip of the beds is about 5° the strike of the intraformational shear-planes being essentially that of the major formations. The feature provided a considerable puzzle before Mr. Cope's explanation was published. A tectonic origin in this case is not, however, altogether convincing, since the regional dips are as a rule less than 50° and much lower than those generally encountered by Mr. Cope.
A subsequent attempt at detailed description by the writer was frustrated by the filling.in of the quarry section without previous notice, so that it is no longer visible. There is one photograph, but this is unfortunately not good enough to provide a satisfying record.
The petrology of two granite-slate contacts at Cape Town, South Africa
Authors: Walker F. , Mathias M. 
Published: October 2009

Most geologists acquainted with the wonderfully clear contact sections of the Cape Town granite will doubtless be inclined, like Sir Lewis Fermor, to follow Darwin and Lyell in regarding them as typical examples of igneous intrusion. This does not, of cmirse, mean that there is nothing more to be learnt about the process which they illustrate. I have spent a considerable amount of time in the area since I first described cordierite from it, having ranged much farther afield on the granite than the paper takes us. I was particularly interested in the problem of the large felspars, to the occurrence of which attention was first drawn by A. W. Rogers. Their similarity to the pseudo-porphyritic crystals seen in the granite, not only here, but in the part of Dartmoor with which I am familiar, is most marked. They also closely resemble the large microclines in the Matopo granite, near which I am writing, this being part of a mass of “ Old Granite ” so big that it extends beyond the boundaries of Rhodesia, in spite of the fact that the country is much larger than Britain. The Cape granite does not belong to this ancient group, but is one of a younger series to which the well-known Bushveld Complex is probably related, a point which is certainly worthy of attention.
At the Cape contact, though the margin of the altered sediments is often felspathized, just as it is on the north side of Dartmoor, this does not appear
Slumping in the Carboniferous rocks of Pembrokeshire
Authors: Kuenen Philip Henry 
Published: October 2009

The coastal cliffs between Tenby and Telpyn Point afford a fine section through part of the Carboniferous strata of southern Wales. Here the writer came across some thirty localities showing evidence of slumping. The evidence takes several forms : (1) contortion and slip-bedding; (2) slump-ball structures of a few inches to 24 feet across, generally composed of sandstone and embedded in mudstone. Lumps of clay-ironstone, resembling concretions, appear to have a similar origin; (3) crumpled balls, resembling the slump balls, but of a less compact structure, of only a few inches across and occurring embedded in sandy shale; (4) slipped blocks, giving the appearance of cross-bedding. These occur amongst other slump structures, as separate masses, generally a few feet across, which have slid without much internal distortion; (5) pseudo-ripple marks, which are regular slight folds measuring a few inches from crest to crest, each crest persisting only a short distance along the strike. They resemble ripple marks, but through a thickness of a few feet all laminae are bent in “similar folds” with the crests directly above each other.
The thickness of the slump sheets varies from a foot or less to about 15 feet. For each sheet the thickness remains almost constant over large areas. The most extensive sheet is exposed for a mile along the coast around Telpyn Point and for 200 or 300 yards at right angles to this direction. At Waterwynch Bay four sheets are superposed. These larger sheets are composed of slump balls embedded in mudstone. They alternate with undisturbed beds. The slopes on the sea-floor during the slumping must have been exceedingly slight, since there is plentiful evidence of shallow water. Moreover, most individual, undisturbed beds can be traced for considerable distances, each showing a constant thickness.
The slump balls are explained by quasi-turbulent motion of the sliding mud. An experimental investigation of the mechanics is being conducted in conjunction with Dr. van Straaten.
Difficulty is sometimes found in distinguishing between slump structures and buckling in anticlinal cores, the two features frequently being closely associated in the field. Although it is not deemed probable, the possibility must be admitted that the so-called buckling is due, at least in part, to slumping. Anticlines, also, may have tended to form where slumping had previously caused irregularity in the bedding.
The geology of the Llandovery district: Part II. the Northern Area
Authors: Jones Owen Thomas 
Published: October 2009

Summary
The area described lies north-east of Llandovery and within about seven miles of that town; it is largely exposed, heather-clad upland. The adjoining area to the south was dealt with by the same author in a paper published in 1925.
The three divisions (A) Lower, (B) Middle and (C) Upper Llandovery, established in the south, are recognized in the Northern Area, but here they vary greatly in thickness and some even disappear locally.
Along the western boundary the Lower Llandovery rocks are faulted against Upper Bala mudstones with thin grits. Due east of the town only the lower part of the Lower Llandovery occurs between the Western Boundary Fault and the Upper Llandovery, but farther north, in the Crychan valley, the higher parts of the formation appear for a short distance. East of Noethgrug the whole subdivision is overstepped by the Upper Llandovery.
The Middle Llandovery first appears in the Crychan valley about three miles northeast of the town, and after trending to the north and then the south disappears under the Upper Llandovery three miles east of the place where it first appears. North of these two points the subdivision is represented probably to its full thickness and in places yields many graptolites.

The Upper Llandovery maintains its general characters through Cefn-y-gareg and Noethgrug, but near Craig-wyddon thinning sets in and within about three miles the main development is reduced to only 40 feet of
Pentamerus oblongus
sandstones. The uppermost part of the formation consists of green mudstones with some thin siliceous bands. The Upper Llandovery below these mudstones near Llandovery consists largely of greenish, sheared-looking mudstones but becomes more sandy to the north-east. It is significant that not only the Upper Llandovery but also the Middle and Lower Llandovery in the Noethgrug area develop coarse sandy and pebbly beds. At the extreme north-east of the district the base of the Upper Llandovery can be seen resting on Upper Bala mudstones.

The structure of the area is relatively simple; to the east of the Western Boundary Fault the Lower Llandovery rocks dip with few exceptions very steeply, or are even vertical. In the succeeding Middle and Upper Llandovery of Gefn-y-gareg the dip lessens, and between Cefn-y-gareg and Noethgrug the beds turn over in an impressive pitching syncline.
On Noethgrug the rocks dip west at moderate angles, but south of that region they turn over in a broad anticline with a southerly pitch. On the eastern limb of the anticline in the Craig-wyddon ridge they again become vertical. The core of the Noethgrug anticline is occupied by Upper Bala mudstones which are partially surrounded by a strong escarpment of Lower Llandovery rocks. The dips in the folds suggest a push from the north-west.