bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHARNOCKITES AND THEIR ASSOCIATED GNEISSES IN THE PRE-CAMBRIAN OF CEYLON
Authors: COORAY PERCIVAL GERALD 
Published: October 2009

The Pre-Cambrian rocks of Ceylon are divided into the granulite-facies Highland Series (metasediments and charnockites) and the almandine-amphibolite facies Vijayan Series (granites, granitic gneisses, and migmatites). The Vijayan Series represents, in part, Highland Series rocks which were further altered during a later metamorphic episode or episodes. At the junction of the two series is a transitional zone which possesses lithological, structural, and metamorphic features characteristic of each. Charnockites are abundant in the Highland Series and rare in the Vijayan, and charnockitic biotite-gneisses are widely developed in the transitional zones.
The field-relations, structures, tectonics, lithology, and grades of metamorphism of the major Pre-Cambrian units are described and the relations of these units to each other are discussed. It is shown that in the course of retrogressive metamorphism (probably in the presence of water) that converted Highland Series rocks to Vijayan types the charnockites were first altered to charnockitic biotite-gneisses and ultimately to non-charnockitic biotite- and hornblende-bearing rocks.
TERTIARY WELDED TUFFS IN EASTERN ICELAND
Authors: WALKER GEORGE PATRICK LEONARD 
Published: October 2009

The welded acid tuffs that are a minor constituent of the volcanic pile are hard felsitic rocks, usually highly vesicular, with a basal glassy layer. They usually have the characteristic microtexture of welded tuffs, but field criteria are more reliable in distinguishing them from lavas and non-welded tuffs. An isopach map is given of the Skessa tuff, which is the product of a single subaerial eruption. The original extent of the welded parts of this tuff is estimated to have been 100 square miles, and its average thickness 25 to 30 feet ; peripheral outcrops are not welded, and cover an additional 70 square miles. In the welded parts the tuff particles were deformed, roughly aligned, and welded together under their own weight and momentum and the accumulated tuff remained plastic long enough for vesicles to form.
A classification of tuff deposits into five grades is proposed which is based on the plasticity and temperature of the tuff particles. The Skessa tuff is a representative of the rather rare grade in which the particles had the highest plasticity and, presumably, temperature. Bubbles of basaltic glass that occur in the tuff appear to indicate simultaneous eruption of acid and basic magma.
THE STRUCTURE OF THE NORTH-EASTERN TRACT OF THE DARTMOOR GRANITE
Authors: BLYTH FRANCIS GEORGE HENRY 
Published: October 2009

The granite margin from Sticklepath to Bridford, of which the only map hitherto available has been the one-inch Old Series sheet 25 dating from 1866, has been re-mapped, together with the rest of the area lying north-east of the Lustleigh-Sticklepath fault-system (
Blyth 1957
). Complex faulting in the Lustleigh area is described.

The fracture-pattern consists of a late NW.-SE. fault-system with associated NNW.-SSE. faults, which is superimposed on an earlier series of fractures including joints, aplites, and tourmaline and haematite veins.
The northern part of the Dartmoor granite is visualized as a thick intrusive sheet with an outwardly dipping contact against Lower Culm sediments. More than one episode of movement on the NW.-SE. and NNW.-SSE. faults is postulated, and some part of it is thought to be of Tertiary age. This has resulted in an area of broken granite which has been more readily eroded than the area to the south-west of the faults.
The Breiddalur central volcano, eastern Iceland
Authors: WALKER GEORGE PATRICK LEONARD 
Published: October 2009

The Tertiary central volcano of Breiddalur, the first to be described of several—perhaps many—such volcanoes in Iceland, has a volume of about 100 cubic miles of basic, intermediate, and acid lavas and pyroclastic rocks, with a maximum thickness of 5000 to 6000 ft. The basic lavas are unusually thin owing to the fact that they were erupted on a sloping surface. The central volcanicity contrasts with the flood-basalt fissure-eruptions of the surrounding country; at times the volcano stood up as a co ne above the flood-basalt plains, but flood-basalts were all the time being erupted; they were interdigitated with the products of the volcano (so strikingly that the term ‘cedar-tree volcano’ seems appropriate), and later completely buried it.
The core of the volcano is marked by a profusion of acid lavas, pyroclastic rocks, and minor intrusions; in it the rocks are drastically altered and show variable and sometimes abnormally high dips indicative of cauldron-sub- sidence. A swarm of dykes locally constituting as much as 20 per cent of the country passes through the core.
The rocks above the core probably in part occupy a crater or caldera; they include agglomerate containing blocks of granophyre, granite, and gabbro from inferred syngenetic intrusions below the volcano; a palagonite-tuff and breccia with basalt pillows, probably form- ed in a crater lake; two welded acid tufts; and a thick rhyolite flow joined to its plug-feeder.
Acid rocks are mostly concentrated in or near the core, except for a spectacular group of parasitic rhyolites in which all stages in uncovering of the plug-feeders by erosion are seen. Simultaneous eruption of basic and acid magma from the same orifice is evidenced by one rock, which represents an emulsion of the two magmas, and also by a composite lava, with basic and acid components, which was erupted from a composite dyke.
Tilloids in the West Congo geosyncline
Authors: SCHERMERHORN LODEWIJK JACOB GERARD , STANTON WILLIAM IREDALE 
Published: October 2009

In the West Congo geosyncline, which stretches from Gaboon far into Angola, the Lower and Upper Tilloid Formations extend continuously over more than 100 000 square kilometres. Of Late Pre-Cambrian age, they are most probably equivalent to the
Grand
and
Petit Conglomérats
of Katanga. They have generally been thought to consist of tillites and periglacial beds, but detailed study in north-west Angola has led to their reinterpretation as submarine mudflow deposits.

The tilloid formations are generally well-bedded sequences consisting of tilloids (till-like pebbly mudstones and greywackes), conglomerates, greywackes, mudstones, quartzites, and limestones, with transitional rock-types. The tilloid clasts comprise angular to rounded intrabasinal fragments eroded from preceding strata, well-rounded extrabasinal crystalline stones, and (in the Lower Tilloid Formation only) debris from intraformational spilite lavas. Graded bedding occurs, sometimes in the tilloids and frequently in the quartzites and greywackes.
Each formation marks the beginning of a sedimentary cycle within the West Congo geosyncline major cycle, and was laid down in a sharply subsiding basin after emergence and slight erosion of the preceding beds. Each is followed by rhythmically bedded turbidite formations. Tilloids at other levels in the West Congo System are also described.
In each formation marine sediments are intercalated among tilloids, ruling out the possibility of a continental origin. Lithological, stratigraphical, and other evidence is over-whelmingly against a glacio-marine origin.
It is suggested that the tilloids were deposited from mudflows formed by the slumping of unconsolidated sediment on the shelf, incorporating mud, sand, gravel, and stones up to large boulder size. This material, of both intrabasinal and extrabasinal provenance, was thoroughly mixed as it flowed far into the geosyncline to be redeposited as tilloid. It is proposed to distinguish ‘flow tilloids’ of this kind from ‘slide tilloids’, less well mixed and smaller in size, formed by less mobile submarine slides. It is thought that they reflect a special tectonic environment of deposition (abrupt subsidence of the geosyncline with only slight elevation of the adjacent land areas) which gave rise to unusually dense turbid flows; tilloid deposition is thus seen as a special type of geosynclinal turbidite sedimentation.
Flow-tilloid formations appear to be characteristic of Late Pre-Cambrian geosynclines. The acceptance of a non-glacial origin for the West Congo tilloids would necessitate the re-examination of the evidence for a Late Pre-Cambrian glaciation.
The Lewisian complex of South Harris With some observations on the metamorphosed basic intrusions of the Outer Hebrides, Scotland
Authors: DEARNLEY RAYMOND 
Published: October 2009

The metamorphic petrology and history of the Lewisian rocks of South Harris are described.

The paragneisses in each of the two main belts are divided into three lithological and possibly stratigraphical units, the disposition of which indicates folding in tight plunging isoclines along
Nw–Se
(Early Laxfordian) axes. Relic textures indicating an early (pre-Lax-fordian) metamorphism and folding are recognizable in the paragneisses and also in the pyroxene-granulites which appear to intrude the paragneisses. This early metamorphism is probably Scourian in age. The pyroxene-granulites are earlier than and are not comagmatic with the igneous complex.

The igneous complex, which is a metamorphosed differentiated (and possibly originally layered) anorthosite–gabbro–tonalite mass, together with the metamorphosed basic intrusions in its immediate vicinity and the widespread metamorphosed basic dykes and sills in the Outer Hebrides, constitute an essentially non-orogenic suite of post-Scourian pre-Early Laxfordian age. The geochemistry of this suite shows it to be tholeiitic in character and probably closely related to the Scourie dykes of the Scottish mainland.

Early Laxfordian granulite-facies metamorphism associated with the main
Nw–Se
folding of the area followed the emplacement of the non-orogenic igneous suite. A south-easterly plunge and north-easterly overturning characterize the folds to the north-east of the igneous complex; to the south-west the plunge is north-west, and the overturning is to the south-west.

A Late Laxfordian injection-complex situated to the north-east comprises extensive areas of migmatization and granitic intrusion and is associated with a front of hydrous retrograde metamorphism which strongly affects the Langavat paragneisses and parts of the igneouscomplex. The sinuous trend of the Langavat paragneisses is attributed to cross-folding of thisdate.
All the earlier rock-types are cut by a suite of Late Laxfordian granite pegmatites containing uranium, thorium, and rare-earth minerals.
The succession and structure east of the Glaslyn River, North Wales
Authors: BEAVON ROY VERNON 
Published: October 2009

The succession and structure of some mid-Ordovician sedimentary and volcanic rocks are described. Marine slates and grits are succeeded by welded and bedded rhyolitic pyroclastic rocks which are overlain by basic tuffs, lavas, and intercalated slates. A local intravolcanic unconformity cuts out over 5000 ft of strata below part of the Snowdon Volcanic Series. The fragmented debris of the missing strata forms a mixed deposit of breccias which overlies the unconformity in places. Normal faulting of Lower Caradoc age is postulated, and it is suggested that the unconformity is part of a buried volcanic collapse-structure. Timerelations suggest that the collapse was initiated by concealed intrusive activity near Aberglaslyn. The intrusion produced local thermal metamorphism and tourmalinization of the early Caradoc sediments in post-Harnagian and pre-Longvillian times.
The main structure is the south-westward continuation of the Dolwyddelan syncline, flanked to the west by a complementary anticline.
The Leannan fault
Authors: PITCHER WALLACE SPENCER , ELWELL ROYSTON WILLIAM DUNLOP , TOZER CHARLES FALLOWS , CAMBRAY FRANK WILLIAM 
Published: October 2009

A powerful north-east-trending fault cuts right across the north-west corner of Ireland and forms the most important member of a system of steep wrench-faults that dissect the Dalradian rocks of Donegal into parallel strips.
The contrast between the rocks flanking this Leannan fault is very marked. On the north-western side the outcrops of the same succession of metasediments run parallel to the fault-line for over 60 miles; over this distance they show little change in lithology, structure, or metamorphism. On the other side the geology varies considerably along the fault, and, except in the north-east, the outcrops run at a high angle to the fault-line; as a result, several different rock-groups are brought against the fault. The metamorphism increases progressively to the south-west so that rocks of kyanite grade are finally brought against others of chlorite grade.
The main movements on the fault are shown to have occurred between the deposition of red beds, presumably of Lower Old Red Sandstone age, and the deposition of Viséan marine sediments.
The fault-zone generally consists of one main break accompanied by two others of lesser importance: together these fractures isolate narrow strips of metasediments in which inverted sequences are the rule. It is argued that the inversion of these strata predates the faulting, and that they were derived from the now eroded limb of a great recumbent fold. Along the main fault a total of 60 yards of intense deformation is usual, and black schist, platy siliceous mylonites, and quartzitic breccias are the result; the steep platiness is always set at an acute angle to the fault. Two separate movements are shown to have occurred; a downthrow to the south-east amounting to several thousand feet is combined with a left-handed displacement, the amount of which, though difficult to estimate, may be as much as 25 miles.
The Leannan fault is directly in line with the Great Glen fault and the possibility that it is a continuation of this structure is discussed.
Gravity measurements in the north-eastern part of the Irish Sea
Authors: BOTT MARTIN HAROLD PHILLIPS 
Published: October 2009

During the summer of 1961 124 new gravity measurements were made in the north (mainly north-east) Irish Sea with an underwater gravity meter.

In north-west England, south-west Scotland, and Northern Ireland a regional rise in the Bouguer anomaly is observed on approaching the north Irish Sea; a high regional Bouguer anomaly of more than 40mgal is also characteristic of the Isle of Man. The author considers that this reflects either a crustal thinning of about 3 km or a denser crust (by about0 03g/cm
3
) beneath the Irish Sea; denser basement rocks may in part be responsible.

Over most of the sea area surveyed negative gravity anomalies of 20mgal to 40mgal amplitude are superimposed on the high regional Bouguer anomaly. Both the shape of the anomalies and their correlation with the surrounding coastal geology suggest that they are essentially caused by large sedimentary basins. The two main negative anomalies thus interpreted are (
a
) between the Point of Ayr, the Solway Firth, and Wigtown Bay (thought to be at least 2130 m [7000ft] deep), and
(b)
between south Cumberland and the Isle of Man (probably at least 2440m [8000ft] deep). Coastal geology suggests that Carboniferous and New Red Sandstone rocks form the major 'fill', although sediments of Old Red Sandstone or post-Triassic age cannot be ruled out.

A negative anomaly of nearly 20mgal amplitude forms the south-eastern continuation into Luce Bay of the negative anomaly over the Stranraer New Red Sandstone basin. It closes to the south-east near the mouth of Luce Bay. As on land, it is interpreted as an asymmetrical basin of New Red Sandstone and earlier sedimentary infill with a steep (? faulted) northeastern margin, reaching a maximum depth of at least 1340 m (4400 ft).
A single gravity traverse westwards from Peel reveals a sharp gravity drop of about 15mgal immediately off shore; this is interpreted as a sedimentary basin lying off the west coast of the Isle of Man. The Isle of Man thus appears to be an uplifted horst-like region of Lower Palaeozoic rocks with the northwestern and south-eastern coastlines controlled by the margins of steep-sided sedimentary basins of post-Lower Palaeozoic age.
Lower Palaeozoic plankton
Authors: BULMAN OLIVER MEREDITH BOONE 
Published: October 2009

The graptolite biocoenosis is accepted as the epipelagic or oceanic plankton fauna of the Lower Palaeozoic, although the geosynclinal deposits in which graptolite remains occur are not typically oceanic. Local variation within geosynclines implies a measure of permanence and stability in their faunas, but the general similarity in graptolite successions calls for frequent intercommunication, and epipelagic plankton probably drifted into geosynclinal seas from outlying oceanic areas. The location of these oceans introduces the problem of continental drift.
Reconsideration of morphological evidence suggests that nema (or virgula) attachment was the exception in the adult graptoloid but may have been more prevalent in juvenile stages; the occurrence of a general ‘size limit’ for stages with prominently developed nema could prove functionally significant. Some form of vacuolated extrathecal tissue seems the most plausible alternative buoyancy mechanism for adult forms. There is some evidence of attachment in (adult) Tremadocian dendroids, and the origin of the Graptoloidea may be causally related to a phase in the development of Sargasso-like seas.
Other constituents of the plankton are briefly reviewed; the few organisms that appear acceptable are principally algae (including filamentous blue-green algae and hystrichosphaeres), radiolaria, coelenterates (various medusae, siphonophores, and ? ctenophores), small inarticulate brachiopods, conodonts, possibly certain small trilobites, and small orthoconic nautiloids.

The suggestion that graptolites lived at various depths is not accepted. Temperature, however, might well have affected their geographical distribution.
Nemagraptus gracilis
and
Monograptus turriculatus
range from nearly 40° s to about 75°
n,
but if related to latitudes indicated by palaeomagnetic evidence, both approximate more closely to a warm-temperate or tropical zone. Relation to ‘pre-continental drift’ positioning of the Americas introduces anomalies.

Further work on the distribution-patterns of individual graptolite species may provide evidence on the presence of an early Atlantic Ocean; failing this, the central parts of various geosynclinal seas would provide the only indication of epipelagic regions (other than the Pacific) throughout the Lower Palaeozoic.
The stratigraphy and structure of the Silurian (Wenlock) rocks south-east of Hawick, Roxburghshire, Scotland
Authors: Warren P. T. 
Published: October 2009

From Dr R. B. Rickards:
Work on the Cautley area undertaken during the last few years, and completed since the reading of Dr Warren's paper, has shown that the graptolite zones recognized by Watney & Welch (1911; and see Warren 1964, p. 207) are in need of considerable revision.

Cyrtograptus rigidus
of Watney & Welch is very close to
C. symmetricus
Elles (1900
). But it has been shown that the latter species is conspecific with
C. rigidus
Tullberg (
v
.
Gortani 1922
); and this has been confirmed by other workers (e.g.,
Bouèek 1933
). The species described by
Elles (1900)
and Elles & Wood (1913) as
C. rigidus
is distinct from
C. rigidus
Tullberg (1883)
and has been renamed
C. ellesi
by Gortani (op. cit.). The zones established by Elles in the Welsh Borders, therefore, now read, from the base up:
C. murchisoni, M. riccartonensis, C. rigidus, C. linnarssoni, G. ellesi, G. lundgreni
(see
Bouèek, 1933
;
Evans 1961
).

However, although
rigidus
sensu Watney & Welch is very close to
rigidus
Tullberg, it is intermediate in some characters between the latter and
C. ellesi
Gortani. Furthermore, as shown below, it occurs at an intermediate horizon, namely the zone of
C. linnarssoni,
and may represent an evolutionary stage leading from
rigidus
Tullberg to
ellesi
Gortani. Its intermediato nature was appreciated by Watney & Welch (1911, p. 234) and also by Elles herself, since a specimen in the Sedgwick Museum (a 22459) presented by Wood, is labelled '
C. symmetricus
mut.
cautleyensis
Elles MS'.

The
A reinterpretation of the breccias in the Meneage crush zone of the Lizard boundary, south-west England
Authors: LAMBERT JOHN LEWIS MACKENZIE 
Published: October 2009

Breccias exposed north of the Lizard boundary in east Meneage have hitherto been regarded as tectonic in origin, and the area occupied by them has been called the
Meneage crush zone.

The characters and relations of the rocks of this zone are most clearly seen in the coast section between Nare Point and Porthallow. Unstratified clastic sedimentary rocks that make up the bulk of this section consist of four divisions: siltstone breccia, slate with phacoids of greywacke, conglomeratic pebbly slate, and conglomerate. Somewhat similar rocks are poorly exposed inland and are also found at one locality on the west coast of the peninsula.
The rocks have been deformed tectonically but it is concluded that their lack of stratification is due to a process that operated soon after deposition, most probably subaqueous slumping. There is no evidence to support the hypothesis of large-scale northward thrusting of the Lizard series.
Granite beneath Viséan sediments with mineralization at Rookhope, northern Pennines
Authors: DUNHAM KINGSLEY CHARLES , DUNHAM ANSEL CHARLES , HODGE BRIAN LESLIE , JOHNSON GEORGE ANTHONY LOBJOIT 
Published: October 2009

The geological results of a borehole drilled to investigate the coincidence of centres of a zonal pattern of mineralization (
Dunham 1934
) with areas of strong negative Bouguer anomaly are presented. The presence of a granite batholith with cupolas, postulated by Bott & Masson-Smith (1957) has been proved; the top surface of the granite was found at 1281ft depth and the boring was continued to 2650 ft in granite.

The section begins in the Great Limestone at the base of the Namurian; a normal succession in the Middle Limestone Group (Lower Carboniferous) is revealed, the Smiddy Limestone with
Girvanella
Band being reached at 1056 ft 6in. The Lower Limestone Group differs from the section in Teesdale and the Pennine escarpment; in particular, beds equivalent to the Melmerby Scar Limestone, identified by their fauna of algae, corals, and brachiopods, have a rubbly lithology and are split by bands of seatearth, sandstone, and shale. Beneath them, clastic sediments 38 ft thick with marine fossils rest on the weathered surface of the granite.

Two quartz-dolerite sheets were proved; the Little Whin sill, 6ft, is in the Three Yard Limestone as at Stanhope, while the Great Whin sill, 192ft 9in, lies beneath the Jew Limestone, stratigraphically lower than in Upper Weardale.
The Weardale granite, carrying biotite and abundant muscovite, has a low-dipping foliation in the upper part, but this becomes less obvious below 2225ft depth. Preliminary X-ray studies indicate that low albite, orthoclase, maximum microcline, and forms intermediate between the last two are present. Analyses of representative rocks for major and trace elements are given. Xenoliths are conspicuously absent, but aplites and pegmatites are common. The mineralogical and chemical effects of weathering before Carboniferous sedimentation, and of the mineralization, are described.

The borehole was sited near the crossing of the Boltsburn lead vein
(ene-wsw)
and the Red fluorite-iron vein
(ese-wnw),
both of which dip towards it. Strong metasomatic mineralization, including green fluorite, blende, and quartz occurs in the Tynebottom, Jew, and Lower Little limestones. Numerous small veins were also cut both in the sediments and the granite. Though chalcopyrite is present against the lower sediments, there is no evidence of a concentrated copper zone. Fluorite continues into the granite, and pyrrhotine, not present above, is found from 1355 ft depth. Mineralization continues to much greater depths than have previously been proved in the area; its source presumably lies beneath the granite cupolas, which may, however, have guided the rising fluids.