bluuebunny/crossref_metadata_2025 huggingface dataset:
GEOLOGY OF THE REYDARFJÖRDUR AREA, EASTERN ICELAND
Authors: WALKER GEORGE P. L.
Published: October 2009

A succession of nearly 15,000 feet of volcanic rocks, mostly plateau-basalt lavas, is described from the Reydarfjördur area. This area is in the middle of the large Tertiary outcrop of eastern Iceland, and the rocks described constitute the lower parts of the exposed succession there. They dip uniformly west-south-west at 3–7 degrees.

Tholeiites, olivine-basalts, and porphyritic basalts rich in phenocrysts of basic plagioclase make up the bulk of the lava pile, and there is little sign of any systematic distribution of these types. Lavas of a particular type tend to form groups of flows, and these can be readily mapped in the field and clearly have a wide horizontal extension.

Two long periods of acid volcanism are distinguished, both having given rise to a considerable bulk of acid and intermediate lavas and pyroclastic rocks. Two more acid volcanic episodes are represented in the mapped ground by acid tuffs, and a fifth is represented by the copious outpourings of acid and intermediate lavas and pyroclasts of the Thingmuli central volcano which was later built on the platform of plateau lavas described in this paper.

The bulk of the lavas are regarded as the product of fissure eruption, and two examples have been found of a lava connected to its dyke feeder. The dyke swarm in the area is estimated to contain over 500 dykes, mostly basic, with a general northerly trend.
THE OSTRACOD FAUNA OF THE SHALE FACIES OF THE CAWDOR LIMESTONES, NORTH END OF CAWDOR QUARRY
Authors: ROBINSON JOHN ERIC
Published: October 2009

A series of 45 samples has been collected systematically from the shale overburden of Cawdor Quarry, Matlock, and examined for their microfauna. Of the several fossil groups represented, only the ostracods, by reason of their abundance and diversity of form, are considered in this account.

A total of 16 genera and 20 species, including one new genus and six new species, have been identified and their distribution in the varied lithologies of the shale succession recorded. The faunal assemblage has been given a precise stratigraphic significance by the discovery in the same beds of the goniatite
G. granoaus,
indicating an horizon in the lower P
2
subzone.
THE SUCCESSION AND STRUCTURE OF THE BORROWDALE VOLCANIC ROCKS SOUTH-EAST OF ULLSWATER
Authors: MOSELEY F.
Published: October 2009

The lower 8500 feet of the Borrowdale Volcanic succession is exposed in the Ullswater region and is divided in this paper into four groups. The lowest, the Ullswater Group, faulted against the underlying Skiddaw Slates, consists of about 2700 feet of basalt and basic andesite, followed by 1500 feet of flow-brecciated andesite. Above this, the variable Birk Fell Group (approximately 1300 feet thick) consists of rhyolite, felsitic tuff (including streaky welded tuff), and andesitic tuff. The succeeding Place Fell Group (2500 + feet) is formed of andesitic and felsitic tuff with flows of basic andesite and basalt. There is some evidence that the andesitie and basic rocks were derived from the south-west and the felsitic rocks from the east. The highest beds mapped are the Angle Tarn Andesites, probably to be correlated with the Wrengill Andesites of other parts of the Lake District.

The principal structural feature is a broad north-easterly trending asymmetrical syncline, which is continuous with that of Scafell and Helvellyn. Cleavage is moderately developed and also has a north-easterly trend (average 054°), with a near-vertical dip. Of several well-developed fault systems, the most important has a north-westerly trend (average 305° and consists of dextral wrench-faults with large strike and dip-slip components. It is suggested that there was an early phase of wrench-faulting and a later phase of normal faulting along the same lines. Another important group of faults are northerly (354°) high-angle dip-slip faults, terminated by the north-westerly faults and possibly contemporaneous with the suggested later phase of movement of these faults. There are joint systems with the same trends as these two groups of faults, and also a strong north-north-westerly (324°) group of joints interpreted as tension structures of the main folding. Most of the mineral veins seem to be related to the later normal faulting and may be post-Carboniferous. The Skiddaw Slate–Borrowdale Volcanic junction is everywhere faulted. This is interpreted as a thrust and probably reflects the disharmonic relations between the two groups.
THE HELL’S MOUTH GRITS: CAMBRIAN GREYWACKES IN ST. TUDWAL’S PENINSULA, NORTH WALES
Authors: BASSETT DOUGLAS ANTHONY , WALTON EWART KENDALL
Published: October 2009

The paper is an attempt to reconstruct the nature and position of the source, the mode of transportation and the envi ronment of deposition of the alternating grits and mudstones of the Hell’s Mouth Grits of the St. Tudwal’s Peninsula.

The grit beds are very uniform in lithology and in thickness when traced along the outcrops, with a gradual thinning southwards. They exhibit the characteristic textures and structures of greywackes but differ from the normal type in being relatively well sorted and commonly laminated. They are dominantly lithic (low-rank) greywackes with a small percentage of feldspathic greywackes. The directional structures––current-markings and cross-lamination–indicate a northerly source, the composition suggests a source like the Pre-Cambrian of Anglesey and the texture implies transportation by turbidity currents and deposition below wave-base.

The intercalated mudstones are more variable both in thickness and in lithology. They contain laminated mudstones rich in sponge remains, white-weathering pyriteless mudstones, small lenses of a peculiar mud-pellet rock and thin intercalations of lenticular siltstone and grits. The lenticular nature of the bedding and the variable nature of the cross-lamination suggest deposition above wave-base.

The contradictory nature of the evidence is not fully understood but a somewhat similar association of features can be inferred from the results of recent work on deep-sea sediments.
THE GEOLOGY AND PETROLOGY OF THE MURRUMBIDGEE BATHOLITH
Authors: SNELLING NORMAN JOHN
Published: October 2009

The Murrumbidgee batholith is a composite body cropping out over an area of 550 square miles to the immediate south-west of Canberra, Australia. It intrudes Lower Palaeozoic deposits of the Tasman geosyncline and is probably late Silurian or early Devonian in age. The batholith is an elongated body concordant on a large scale with the regional meridional trend. Nine separate componentshave been mapped, the rock types ranging from tonalite to granite
sensu stricto
; the dominant rocks are biotite granodiorites.

The rock types can be divided into three groups, namely: contaminated granites
sensu lato,
uncontaminated granites
sensu lato,
and leucogranites, probably in that order of intrusion. The uncontaminated granites are believed to represent the parental magma from which the contaminated granites were derived by the assimilation of semi-pelitic and pelitie sediments and, in one component, basic igneous rock. The contaminated granites appear also to have been enriched in some of the minerals which would have been precipitated during the early stages of crystallization. The composition of the leucogranites places the min the residual system of petrogenesis and they presumably represent the residual liquids resulting from the crystallization of the other rock types, the amount of these liquids being enhanced by the salie and less refractory material “sweated out” of the assimilated sediments. The place of the Murrumbidgee batholith in the plutonie history of the Tasman geosyncline is briefly discussed.
Sessile marine organisms and their significance in pre-Mesozoic strata. (Anniversary Address, 1960)
Authors: STUBBLEFIELD C. J.
Published: October 2009

I
t
is common knowledge that a salient difference between most plant and animal life on land is that the plant exists almost from birth to death fixed in one small place, that is, it is sessile; and resulting from this, in certain circumstances, coal, lignite or peat deposits are formed. Most land animals, however, are freely mobile and show varying degrees of speed; some even take to the air; but in the sea, many kinds of animals, having spent their larval life swimming freely as plankton, adopt in one way or another, attachment to extraneous material, such as the sea-bottom, stones, some other animal or to sea-weed which itself is sessile. Presumably the merit of an existence at a chosen sea anchorage compared with that of a nomad is that the sessile organism's metabolism is in balance with constant and adequate food supply in conditions of acceptable temperature, light intensity, salinity, sedimentation and depth.

Although plants take their food as liquids or gases, and green plants use photosynthesis to assist this, animals require protein as well as gas and liquid. To acquire food the sessile marine animals depend on sea-water and plankton, either exclusively or with the addition of suspended organic matter; but I should recall that living exceptions to this generalization include certain anthozoa which ingest larger animals including small fish (
Yonge 1949
, p. 82). The usual method of taking in suspended food, be it plankton or other organic matter, is by currents activated by the animal's cirri or
THE LOWER PALAEOZOIC ROCKS OF SOUTH-WEST MURRISK, IRELAND
Authors: STANTON WILLIAM IREDALE
Published: October 2009

The general geology of an area of Ordovician and Silurian rocks in North Connemara is described. The oldest strata are the Arenigian Sheefry Grits, a thick marine series of slates and greywackes derived from the south. Many of the beds exhibit perfect grading; they are thought to be the deposits of turbidity currents. The Glenummera Slates follow conformably, and are succeeded by the deltaic Mweelrea Grit series, of Middle Ordovician age. Marked facies changes show that the source of sediment lay to the south, and many of the conglomerate pebbles can be referred to the Connemara Schists.

In the lower part of the Mweelrea Grits are thick persistent beds of welded tuff, possibly the products of eruptions of Peléan type. Massive graded tuff-beds in the Sheefry Grits are thought to have had a similar origin.

Silurian (Llandovery?) quartzites and slates, with a basal conglomerate, rest un-conformably on the Ordovician rocks. A small late Caledonian granite pluton was emplaced by stoping, and associated with it are acidic and appinitic dykes.

Minor disturbances occurred during the Upper Ordovician, but the main folding was Caledonian. Right-handed stresses involving the formation of two large tear-faults swung the Caledonian strike round into a west-north-westerly direction.
THE STRUCTURAL GEOLOGY OF THE BOULE AND BOSCHE RANGES IN THE CANADIAN ROCKY MOUNTAINS
Authors: O’BRIEN CHRISTIAN ARTHUR EDGAR
Published: October 2009

The paper records the results of geological mapping over the Boule and Bosehe Ranges which form a part of the Front Ranges and adjacent foothills of the Rocky Mountains of Canada in an area near the Athabaska River Valley.

The structure of the area comprises a series of individual thrust-blocks, each successively overlying the contiguous block from south-west to north-east. Each block has been subjected to intense folding and faulting. Folding is moderately disharmonic at the surface, with the sedimentary column displaying three competent groups separated by incompetent formations with strong tendencies towards plastic deformation.

Near the base of the column is a thick section of chloritic shales of Lower Cambrian age, whose importance is stressed as a potential lubricating medium for the main thrust movements.

The possibility of the existence of a plane of
décollement
in this lubricating medium is discussed, with the attendant suggestion that the Front Ranges may have been pushed north-eastwards over a largely unbroken Lower Cambrian and Pre-Cambrian basement.
THE EPIFAUNA OF A DEVONIAN SPIRIFERID
Authors: AGER DEREK VICTOR
Published: October 2009

A detailed study was made of the organisms found attached to shells of
Spinocyrtia iowensis
from the Upper Devonian Cedar Valley Limestone of Iowa and adjacent states. Four common symbiotic associates were recognized: two polyzoans, a tabulate coral and a serpulid worm. An account is given of the order in which they usually attached themselves to their host and of their most favoured positions on the shell. The possible inter-relationships between all the organisms concerned are discussed. Several comparisons are made with studies on the epifaunas of present-day organisms.
THE STRATIGRAPHY AND STRUCTURE OF THE ORDOVICIAN ROCKS OF THE RHINNS OF GALLOWAY
Authors: KELLING GILBERT
Published: October 2009

Re-examination of the stratigraphy and structure of Ordovician rocks in the northern part of the Rhinns of Galloway has led to amplification and some reinterpretation of the concepts of succession and structure advocated by Poach and Horne (1899). A stratigraphical succession within the greywackes has been erected on the basis of palaeontological and lithological evidence, and with the aid of “way-up” criteria. Stratigraphical groups have been subdivided on petrological grounds. The intercalation of at least two bands of Glenkiln (black) shale in a relatively thin greywacke sequence has been detected as far north as Broadsea Bay, and it can be demonstrated that a few miles farther north these black shales are represented by at least ten bands of fissile siltstone with black graptolite-bearing films, separated by some 6000 feet of greywackes. Relatively rapid cross-strike variations in thickness and lithological character have been found in several formations, amounting in the Glenkiln rocks to a general southward attenuation and concomitant increase in the proportion of shale and siltstone in the sequence. Palaeontological evidence shows that all the greywackes are of Glenkiln age, with the exception of the uppermost beds, the Portpatrick Group, which is probably Hartfell.

Structurally the area is believed to comprise four main units, namely, three major complex monoclinal structures of Caledonoid trend with vertical northern limb and tightly folded and otherwise complicated southern limb, and one complex synclinal structure. The units are separated by major faults, mainly thrusts but including the Southern Uplands (= Glen App) fault, which is here normal, throwing south. Minor faults, especially wrench-faults, are of considerable importance.
THE GLACIAL DRIFTS OF THE SOUTHERN PART OF THE SHROPSHIRE-CHESHIRE BASIN
Authors: POOLE EINAR GEORGE , WHITEMAN ARTHUR JOHN
Published: October 2009

Official work on the Nantwich district (Sheet 122) showed t h a t the sequence of two boulder-clays with associated fluvioglacial deposits, previously recognized only in the northern part of the Shropshire–Cheshire basin, also extended into its centre. Subsequent private research has shown that this sequence may be distinguished throughout the whole basin and in a critical region beyond its south-eastern margin—in total an area exceeding 3000 square miles.

The recognition of glacial lake features cut into the Upper Boulder-clay in the Nantwich district and elsewhere necessitates a revision of current ideas about the origin of Lake Lapworth and the age of the Severn terraces above Ironbridge.

Accepted correlations relating to the basin and its adjacent areas, the status of the “Little Welsh Glaciation” and the Newport–Wolverhampton esker chain are discussed. A new interpretation of the Pleistocene and Recent history of the region is presented.
THE GEOLOGICAL STRUCTURE OF THE AREA SOUTH OF LOCH TUMMEL
Authors: STURT BRIAN ALBERT
Published: October 2009

Three distinct stages of folding have been recognized in the area investigated. The earliest folds (F1), on approximately ENE.–WSW. axes, are (from south to north) the asymmetrical Creag na h-Iolaire anticline closing to the south, the Sròn Mhòr syncline, and the asymmetrical Loch Tummel anticline which closes to the north. The Creag na h-Iolaire anticline is correlated with the Aberfoyle anticline (Shackleton 1958). To the north of the River Tummel the general structure consists of a series of overturned folds, whose axial planes dip to the south (cf.
Bailey 1925
); according to A. L. Harris considerable northward movement has taken place here on a series of south-dipping slides. The Sròn Mhòr syncline occupies a central position between the two sets of oppositely directed overfolds, and represents the highest structural level exposed in the area. This fold is comparable in structural position with the Loch Awe syncline.

The primary folds have been refolded during two subsequent phases of folding. The second-phase folds (F2) produced considerable deflexions of strike and the general trend of their axes is NNW–SSE. These folds display a considerable variety of styles. The third phase of folding (F3) is associated everywhere with diaphthoresis Few major structures were formed in the area during the F3 folding, but abundant minor structures were produced.
MAJOR EARTH-FLEXURING IN THE ZAGROS MOUNTAINS OF SOUTH-WEST IRAN
Authors: FALCON NORMAN LESLIE
Published: October 2009

Geological evidence is given for the existence of a major flexure, trending NW.–SE., the amplitude of which is 40,000 feet in the Bakhtiari and Kuhgalu Mountains. decreasing to the north-west and south-west. The date of the major flexuring is discussed and is it concluded that it is to some extent contemporary with the folding of the foothill belt. Gravity profiles are given which provide supporting evidence for the flexuring.
INTRUSIVE LIMESTONES IN THE KESHYA AND MKWISI VALLEYS, NORTHERN RHODESIA
Authors: BAILEY DAVID KENNETH
Published: October 2009

Two intrusive limestones in the valleys of the Keshya and Mkwisi streams, tributaries of the Kafue River, are described : the Keshya limestone, which intrudes the roof-migmatite zone of the Kafue Gorge granite, and the Mkwisi limestone, which intrudes a series of late Pre-Cambrian metasediments and contains xenoliths of similar granite. Brecciation of the country-rocks is extensive and the intrusions are irregular in form. Xenoliths are abundant in the limestones, which are coarse-grained, impure calcite-marbles with accessory magnetite, haematite, pyrite, apatite, rutile, monazite and xenotime. Alteration of the country-rocks is characterized by the introduction of alkali-feldspars, phlogopite and titanium minerals.

The origin of the limestones is discussed and it is concluded that they represent an unusual type of carbonatite activity, resembling hydrothermal vein-like deposits in some of their characteristics but probably emplaced by a process of fluidization.
A GEOCHEMICAL SURVEY OF THE NOTTINGHAMSHIRE OIL-FIELDS AND RELATED SEDIMENTS
Authors: EVANS WILLIAM DAVID , COOPER BRIAN S. , CORBETT DAVID WALTER , GOUGH KENNETH
Published: October 2009

T
he possibility of geochemical prospecting for oil depends upon the escape of hydrocarbons through the ‘cap-rock’ of the reservoir deposits to produce a definitive geochemical anomaly representative of the oil beneath. In view of the very large number of petrographical and structural factors that can interfere with the development of such an anomaly, it is not surprising that geochemical methods of prospecting for oil have not always met with conspicuous success. Geochemical anomalies of various types have been recorded over known oil-fields, but the discovery of identical anomalies in unknown territory has not always coincided with an occurrence of oil beneath. The object of the investigation described in this paper was to initiate similar studies in Great Britain using techniques that had not previously been fully exploited.

The oil-fields of Nottinghamshire offer exceptional opportunities for investigating the possibility of the migration of hydrocarbons through a variety of sediments and discontinuous structures. Initially, it was our intention to investigate the following criteria:
(i)
that hydrocarbons migrate vertically above all types of oil accumulations; (
ii
) that the physico-chemical processes governing the movement of hydrocarbons are not greatly influenced by the petrographical and structural characteristics of sediments; and
(iii)
that such geochemical concentrations can be identified amidst the organic components of soils and subsoils (the so-called ‘background organic matter’).
AN OUTLINE OF THE LEWISIAN COMPLEX OF THE OUTER HEBRIDES IN RELATION TO THAT OF THE SCOTTISH MAINLAND
Authors: DEARNLEY RAYMOND
Published: October 2009

The main structural and metamorphic features of the Lewisian rocks of the Outer Hebrides are outlined and compared with those of the Lewisian on the Scottish mainland. In each area three structural zones are recognized, characterized by folding of different styles and periods. The three zones of the Outer Hebrides are closely analogous to the Scourian and Laxfordian zones of the mainland.

Evidence of three periods of folding and metamorphism in varying degrees of intensity may be seen in the Outer Hebrides. The first and second periods were separated in time by the intrusion of a non-orogenic suite of basic sills and dykes of tholeiitic affinities, possibly associated with the plutonic centre in South Harris. This basic suite is regarded as equivalent to the Scourie dykes of the mainland.

The first period of folding and (granulite-facies) metamorphism is recognized in the gneisses above the Outer Isles thrust-plane and in a narrow belt along the Sound of Harris, and is correlated with the Scourian of the mainland. After the intrusion of the basic suite, the rocks were affected by a second period of folding and granulite-facies metamorphism which converted the basic intrusions to garnet-pyroxene-amphibolites. The Scourie dykes of the mainland retain evidence of this metamorphism in the form of corona garnets, garnetiferous border zones, and clouded feldspars. The second folding and metamorphism is regarded as Early Laxfordian because the folding has the same trend as that accompanying the third and last period of metamorphism, which is a retrograde type associated with migmatization and intrusion of granites and pegmatites and is known from absolute age-determinations to be equivalent to the Lax-fordian of the mainland.

The positions of the Lewisian metamorphic and structural zones on the opposite shores of the Minch do not coincide, and the offset can be adequately explained only by later wrench-faulting. Evidence is presented to support the existence of the Minch fault, a sinistral wrench-fault with an approximate displacement of 77 miles, comparable in direction and magnitude with the Great Glen fault.
A LOWER TERTIARY OUTLIER IN THE CENTRAL ENGLISH CHANNEL, WITH NOTES ON THE BEDS SURROUNDING IT
Authors: CURRY DENNIS
Published: October 2009

A series of rock-samples has been obtained from the bed of the English Channel within an area of about five hundred square miles about halfway between the Isle of Wight and Cherbourg. In the north of this area Kimeridge Clay has been proved; farther south, Chalk surrounds an elongated outlier of Lower Tertiary beds, which include representatives of the Reading Beds, London Clay, and Bracklesham Beds. Analysis of the microfaunas of the Cretaceous samples reveals the presence of beds of Santonian, Campanian, and Maestrichtian age. The microfauna of the Bracklesham Beds contains indigenous and derived elements. The indigenous fauna compares most closely with that of the Sables de Cuise. The sources of the derived fauna are of Campanian, Maestrichtian, and Danian ages.
ON FOLDING DURING THREE-DIMENSIONAL PROGRESSIVE DEFORMATION
Authors: FLINN DEREK
Published: October 2009

This paper is concerned with the geometry of homogeneous strain in rocks. Equations relating rotation of planes and lines to the deformation of the rock containing them are derived with the aid of the deformation ellipsoid. The Fresnel construction is borrowed from optical mineralogy to determine from the deformation ellipsoid the principal axes of compression and extension in any plane, and an expression is derived for determining the lengths of these axes. Further equations are derived which define the surfaces of no infinitesimal strain and no finite strain for all possible ellipsoids, and it is shown that these surfaces may be used for rapidly determining whether the principal axes in any plane have suffered shortening or extension.

With these tools the rather complex geometry of three-dimensional homogeneous strain is examined in detail. It is shown, for instance, that during deformation planes and lines develop preferred orientations reflecting the symmetry of the deformation, and pre-existing folds rotate bodily in space and either open or close or both during the deformation. In order to draw further conclusions of general interest the condition of homogeneous strain is relaxed in order to consider the deformation of layered rocks with competence differences between the layers. It is argued that during the deformation of such rocks folds and boudinage form parallel to the principal directions of strain in the layers. The conditions that determine whether folds or boudinage are formed are examined and the subsequent development of the structures after their generation is followed. These methods of analysis are used in the construction of models of superimposed fold-systems which are shown to be similar to some recently described field examples.

It is argued that the tectonic axial cross must be replaced by the deformation ellipsoid. The structures treated in the paper are usually derived by shear-plane hypotheses, but it is considered that such hypotheses are superfluous.
The Lower Palaeozoic stratigraphy of central Murrisk, County Mayo, Ireland, and the evolution of the south Mayo trough
Authors: DEWEY JOHN FREDERICK
Published: October 2009

The Ordovician and Silurian rocks of central Murrisk, County Mayo, Ireland, are described with reference to their stratigraphy, provenance, and conditions of deposition; 36 000 ft of Ordovician rocks are overlain, unconformably, by 5600 ft of Silurian strata.

The Arenig rocks are divided into two series: the Owenmore Series (2000 ft) below and the Murrisk Series (15 000 ft) above. The Owenmore Series (boulder-slides, turbidites, and black slates) was derived entirely from the north; the Murrisk Series (tuffs and turbidites) was derived from the east and south.

The Glenummera Series (4000 ft of green slates with thin psammitic turbidites) follows and is overlain by the Partry Series (15 000 ft). The Partry Series is divided into two groups; the Mweelrea Group below, and the Maumtrasna Group above. The Mweelrea Group (7000 ft of current-bedded deltaic grits) contains six beds of ignimbrite, deposited by
nuées ardentes
with a south-easterly provenance. Periodic westward tilting caused the eastward recession of the delta-front with the concurrent development of boulder-slides and turbidites. The Maumtrasna Group is similar to the Mweelrea Group but contains no ignimbrites, and the grits are coarser, with many interbedded conglomerates.

The Silurian rocks are divided into the Lower Owenduff Group (Upper Llandovery, 0 to 20 ft) below, and the Croagh Patrick Series (Wenlock, 5600 ft) above. The Lower Owenduff Group was deposited in a complex littoral environment and contains a large amount of pyroclastic material. The Croagh Patrick Series is divided into six groups (Cregganbaun Group, 500 ft; Pollanoughty Group, 450 ft; Oughty Group, 360 ft; Fiddaunarinnia Group, 600 ft; Lough Nacorra Group, 1500 ft; Owenwee Group, 2000 ft), the Oughty Group containing five tuff bands. The Croagh Patrick Series was deposited in a northwardly transgressive littoral and sub-littoral belt and was derived exclusively from the north and east.

The Silurian rocks rest unconformably upon the Owenmore Series as the result of strong pre-Upper Llandovery thrusting, concentric folding, and uplift.

During most of Ordovician times, the northern margin of an
e-w
trough (the South Mayo trough) was denned by a normal fault. The southern margin was defined throughout most of Ordovician times and the whole of the Silurian by a rising Cordillera in Conne-mara. Dal radian rocks provided the source for nearly all the clastic material.
The evolution and classification of the graptoloidea
Authors: BULMAN OLIVER MEREDITH BOONE
Published: October 2009

In no other group of colonial organisms has the form of the colony played such a prominent role in taxonomy as in the graptolites. The regularity of the colony in respect of branching and gross rhabdosomal characters, the occurrence of progressive thecal modification (thecal gradients), and, in cyrtograptids, the production of cladia with their integrated thecal gradients, imply an unusual degree of morphogenetic control which appears fully to justify the use of colonial characters in taxonomy. The main outlines of the evolutionary history of the group have been made familiar by the work, especially, of Lapworth and Elles; but a greater emphasis is here placed on the importance of abrupt rhabdosomal modifications followed by extensive thecal differentiation. It is suggested that many of the major rhabdosomal changes could be interpreted as evolutionary grades (J.S. Huxley) with subsequent thecal differentiation representing the ensuing cladogenesis, though the extension of these concepts to colonial organisms is tentative. The main evolution of the graptolites is briefly surveyed and possible taxonomic implications are discussed. Jaanusson’s suborder
Didymograptina
is accepted for the dichograptids, leptograptids, and dicranograptids; his separation of the suborder
Glossograptina
from the
Diplograptina
is welcomed despite its limited cladogenetic differentiation; and the magnitude of the advance represented by the monograptid grade is considered to warrant the recognition of a fourth suborder (
Monograptina
) for the scandent uniserial rhabdosomes. The processes of thecal differentiation and the taxonomic significance and practical utility of various genera and subgenera that have been proposed are discussed with reference to the diplograptids and monograptids. An outline classification at and above family level is appended.
Seismic investigations of the rocks beneath the northern part of Cardigan Bay, Wales
Authors: BLUNDELL DEREK JOHN , KING ROY FAVELL , WILSON CHARLES DOUGLAS VERNON
Published: October 2009

Griffiths, King & Wilson (1961) described geophysical work in Tremadoc Bay resulting in the recognition of three layers of differing seismic velocities. The thickness and velocity of the uppermost, 'layer 1', and the velocity of 'layer 2' beneath it have now been determined more completely by further seismic refraction observations. Layer 1 has been shown to underly Morfa Harlech in the form of a valley, being the southward extension, some 1000 ft deep, of the Glaslyn valley at Portmadoc. This channel probably continues across Morfa Dyffryn and farther to the south-west. It is filled with material having seismic velocities in the range 5000 to 7600 ft/s, the upper 250 ft of which are thought to be of post-glacial age. The lower part may be Pleistocene material, but is more likely to be older.

The seismic velocities found for layer 2 have been compared with measurements made on nearby Ordovician and Cambrian sediments and with results from the Permo-Trias and Carboniferous of the Midlands. This new evidence supports the hypothesis of the previous paper that the northern part of Cardigan Bay is underlain (beneath the more recent cover of layer 1) by Ordovician rocks.
Stratigraphy and structure of the Purbeck inliers of Sussex (England)
Authors: HOWITT FRANK
Published: October 2009

The Purbeck Beds exposed in Sussex are redescribed together with new sections exposed in gypsum mines workings and boreholes. Comparisons are made with Purbeck Beds elsewhere in southern England in boreholes and at outcrop.

A new map of the Purbeck inliers is presented and the structure is discussed. Conditions of sedimentation are illustrated by isopachyte maps.
A new vertebrate fauna from the Triassic of the Deccan, India
Authors: JAIN SOHAN LALL , ROBINSON PAMELA LAMPLUGH , CHOWDHURY TAPAN KUMAR ROY
Published: October 2009

Recent work on the Upper Gondwana Maleri Formation has enabled a more accurate and extended faunal list to be given, consisting of various kinds of fishes (dipnoans, subholostean, pleuracanth), reptiles (especially rhynchosaur, phytosaur, and aetosaurid), and a metoposaurid amphibian. A better estimate can thus be made of the age of the Maleri Formation as Upper Triassic, equivalent to the Carnian–Middle Norian Zones (inclusive) of the standard marine Triassic sequence.

An Upper Gondwana inlier south-southeast of the main Maleri outcrop contains fossiliferous Maleri red clays and also a second red clay belt with a different vertebrate fauna, the Yerrapalli fauna, consisting of reptiles (including a large dicynodont and probably a theriodont and an erythrosuchoid) and amphibians, one of which may be a very large capitosaur. The new fauna seems similar in age to that of the South African
Cynognathus
Zone, i.e. late Lower Triassic. A fauna of this age has not previously been found in the continental Gondwana rocks of India, and if the preliminary results are confirmed it will be necessary to recognize a separate Yerrapalli Formation within the Gondwana sequence.
DISCUSSION OF PAPERS PUBLISHED IN PREVIOUS PARTS OF THE
QUARTERLY JOURNAL
Authors: Turner D. C.
Published: October 2009

From Mr C. N. Okezie:

The writer recently mapped a small portion (about 200 square miles) of the basement complex of the Kafanchan area, in the Nigerian Younger Granite province. He also mapped a very small Younger Granite stock, the Nok granite, within this area.

As a result of this work it became apparent to the writer that the trends of some intrusive Older Granites, their consanguineous granitic pegmatite dykes and sills, and the few basic dykes found in the area appear to have been controlled by four main structural planes of weakness in the basement rocks. These planes are the roughly north-south schistosity and foliation and three inferred sets of master-joints striking roughly
nw–se, ne–sw
, and
e
-w.

Careful examination of the Younger Granite complexes of this province as seen on the 1 : 2 000 000 geological map of Nigeria or on pl. vii of the Society’s
Memoir .No
. 1 shows also that these four planes of weakness appear to have exercised a significant control in the emplacement of the Younger Granites. This is shown by the fact that groups of these complexes are often aligned while individual complexes are often elongated parallel to any one of these four directions. The position is illustrated as follows:

Aligned complexes

(1) Banke-Kudaru-Rishua-Kerku-Nok-Afu (N-S)

(2) Banke-Liruei-Suku-Tongolo-Dagga Allah-Kwandon-Kaya-Kofayi (
nw-se
)

(3) Kwandon-Kaya-Jos-Bukuru-Vom-Kagoro (
ne
-sw)

(4) Burra-Ningi-Kila-Wurji-Fagam (
e
-w)

(5) Zuku-Saiya-Shokobo-Jere-Sanga-Buji-Jos-Bukuru-Rop (
n-s
)

(6) Sara-Fier-Sha-Kaleri-South-Mada-Afu (
ne-sw
)

Elongated complexes

(1) Liruei, Kwandon-Kaya, Kofayi (
nw-se
)

(2) Afu, Fagam (
ne
-sw)

(3) Sara–Fier, Nok, Rishua, Kudaru (
n––s
)

(4)
Strike-slip faulting in the Vaporum region of the Moon
Authors: FIELDER GILBERT
Published: October 2009

Deformed lunar ring-structures are compared with clay models carrying circular forms that are subjected to various types of stress. It is concluded that the ellipticities of the rings in the Vaporum region of the Moon were imposed not through elementary lateral squeezing but, principally, through right-handed multiple shearing movements. The results find confirmation in the direct observation of offsets.
A gabbro—granodiorite association in Singapore Island
Authors: HUTCHISON CHARLES STRACHAN
Published: October 2009

The syntectonic tin-bearing granite batholith system of the Thai-Malayan orogeny is associated in several places from north Thailand to Singapore with satellitic bodies of basic composition. In Singapore Island such a body of gabbroic composition is marginally situated within the batholith, and exposures indicate that it is pre-orogenic.

The orogenic granodiorite has intruded the gabbro in the form of irregular dykes, producing at the immediate contact a variety of hornblende-rich rocks by thermal metamorphism and hybridization. The dykes are crowded with gabbro xenoliths in every stage of assimilation.

A similar petrogenetic sequence and enrichment in hornblende is to be found in gabbro-granodiorite associations in most orogenic regions of the world.
The structural history of the Lewisian rocks of Gairloch, Wester Ross, Scotland
Authors: PARK ROBERT GRAHAM
Published: October 2009

The Lewisian rocks of the Gairloch area comprise a small outcrop of older granulite-facies gneisses (the Ialltaig gneisses), the deformation and metamorphism of which is provisionally assigned to the Scourian period, and a much more extensive group of younger rocks (the Gairloch schists and gneisses) considered to represent a series of sediments (deposited unconformably on the older gneisses) and basic igneous rocks, both extrusive and intrusive.

The deformation and metamorphism of the younger group, provisionally assigned to the Laxfordian period, fall into three principal phases designated early, main, and late. During the
early phase,
a foliation was induced during metamorphism, probably of low grade, and large-scale folds were formed that were completely re-oriented or obliterated during the succeeding phase. The
main phase
was characterized by major folds trending
nw-se
with steep axial planes and later by smaller-scale
nw-se
folds and steep axial-plane foliation slightly oblique to the major folds. Several dolerite dykes were intruded at South Sithean Mor after the main-phase folding. Epidote-amphibolite-facies metamorphism accompanied the formation of the main-phase foliation and continued in the
late phase,
which commenced with paracrystalline folds and concluded with brittle structures produced during retrogressive metamorphism. The formation of the gneisses is assigned to the initial stages of the late phase.
Some relationships resulting from the intimate association of acid and basic magmas
Authors: BLAKE DAVID HENRY , ELWELL ROYSTON WILLIAM DUNLOP , GIBSON IAN LETHBRIDGE , SKELHORN RAYMOND RICHARD , WALKER GEORGE PATRICK LEONARD
Published: October 2009

Evidence is presented from Guernsey, Iceland, Ireland, and Scotland that basic and acid magmas have commonly come together. Examples of this are found in surface extrusions and tuffs and in intrusions of various sizes formed at different depths. The basic magma has commonly been chilled against the acid, and the relationships indicate that the acid component was highly mobile; these two facts are thought to be intimately related, in that the mobility of the acid magma is due to the transfer of heat from the basic magma.

Consequences discussed include the question of the relative age of contiguous intrusions where basic rock is veined by acid: the age-sequence may be the reverse of that normally postulated. The possibility is also considered that basic magma may occasionally be necessary for the uprise of acid magma to high crustal levels.
The deformation of some banded gabbros in the northern Somalia fold-belt
Authors: DANIELS JOHN LEONARD , SKIBA WLADYSLAW JAN , SUTTON JOHN
Published: October 2009

More than 20 layered basic intrusions are known among the crystalline rocks forming an isolated part of the late Pre-Cambrian and Lower Palaeozoic fold-belt in north-east Africa and the Red Sea region.

This paper discusses metamorphic and structural changes in and around five intrusions in an area between 20 and 40 miles north of Hargeisa and some 200 miles south-south-west of Aden: the Dudub, Rakdasafaka, Hamar, Ubali, and Gul Sakar gabbros. These consist largely of melanocratic olivine-gabbro with subordinate pyroxenite, peridotite, troctolite, and anorthositic leucogabbro. They were intruded into rocks that had already reached the amphibolite or granulite metamorphic facies during an early period of regional metamorphism and migmatization. Parts of these gabbros and country-rocks were later metamorphosed and deformed in a period of regional metamorphism that followed the intrusion of the basic rocks and was accompanied by the intrusion of granite. This late metamorphic event was only patchily developed and some gabbros retain many primary features, including rhythmic and cryptic layering, irregular layering, orbicular textures, poikilitic pyroxene, and flow-oriented olivine and plagioclase. The Hamar gabbro retains an incomplete contact-aureole and contains large country-rock inclusions believed to represent projections from a side wall.

The primary layering in all five intrusions now dips steeply and in three intrusions has been folded into structures a mile or two across. During the late movements, parts of the intrusions were converted to metagabbro or amphibolite and developed secondary structures which include shear-belts, minor folds and lineation, and oblique schistosity. Many of these structures have their equivalents in the country-rocks, which were affected by the later metamorphism and in which pre-gabbro high-grade mineral assemblages were partially replaced by lower-grade assemblages. The deformation of country-rock and gabbro is compared and three stages in the conversion of layered gabbro to concordant lineated and foliated metagabbro are recognized. The Somali layered intrusions are compared with deformed basic intrusions in other fold-belts and the deformation of such intrusions is briefly considered.
The structure and metamorphism of the mantling Karagwe–Ankolean sediments of the Ntungamo gneiss dome and their time-relation to the development of the dome
Authors: NICHOLSON ROBIN
Published: October 2009

The Ntungamo gneiss dome has a quartzo-feldspathic core that has an abrupt and generally concordant margin with the overlying Pre-Cambrian Karagwe–Ankolean metasediments. The sediments, which dip off the dome on all sides, lie in synclinal belts around it and between the Ntungamo dome and adjacent domes. There is no good evidence of the intrusive character of the granitic rocks of the dome, and it is suggested that they are deformed Karagwe-Ankolean basement. The deformation history of the metasediments is divisible into two phases separated by a time-interval during which porphyroblasts of andalusite, kyanite, and staurolite developed. The schistosity of the sediments was formed in the first phase and was deformed in the second; the dome and synclines were produced in the second phase. This interpretation differs from earlier ones in which all the Karagwe-Ankolean structures were described as forming in one deformational episode, the schistosity being produced during dome-forming movements that were themselves the result of granite intrusion.
A chemical study of some rocks of the Moine Series of Scotland
Authors: BUTLER BARRY CONRAD MILNE
Published: October 2009

The Moine Series in Ardnamurchan consists of three types of lithological unit: psammites, striped schists, and garnetiferous mica-schists. Chemical analyses and variation-diagrams show that the mica-schists that occur as thin bands in the psammitic and striped schist groups of the Moine Series are of pelitic character, but the garnetiferous mica-schists are comparable with greywackes, especially in their low K
2
O and high CaO and Na
2
O contents. The garnetiferous mica-schists are similar to some rocks from other areas in the Moine Series that have been described as injected, permeated, pegmatitized, or migmatized, and thus have been assumed to have different chemical compositions from those in which they were formed as sediments. All but one of the analysed Ardnamurchan rocks come from west of the belt of regional injection of the Moine Series, and textural, mineralogical, and chemical evidence shows that there are no grounds for supposing that the injection process was effective west of the injection-belt. It is concluded that the garnetiferous mica-schists represent immature poorly sorted sediments of greywacke or silt composition that have not changed appreciably in composition as a result of mechanical or chemical processes of regional injection. The occurrence of this rock-type as an important constituent of the Moine sediments suggests that some of the Moine rocks described as injected may be rocks of greywacke composition that have acquired an ‘injected’ appearance as a result of small-scale differential mobilization during isochemical metamorphism, rather than originally pelitic rocks into which new material has been introduced during the regional metamorphism.
Intertidal flat sediments and their environments of deposition in the Wash
Authors: EVANS GRAHAM
Published: October 2009

The Wash is an area of extensive intertidal-flat sedimentation. Seven sub-environments of deposition can be distinguished on part of the Lincolnshire coast. They are roughly parallel to the coastline and are, from landward to seaward: the salt marsh; higher mudflats; inner sand flats;
Arenicola
sand flats; lower mud flats; and lower sand flats. Cutting across these is the sub-environment of creeks and bordering areas. Each sub-environment is characterized by distinctive surface features, associations of organisms and sediments with differing composition, texture, and sedimentary structures. The sediments contain small amounts of calcium carbonate, organic matter, and iron concentrated in the finer-grained sediments. They also contain small amounts of feldspar and heavy minerals. The tidal waters decrease in competency and capacity as they move inland over the intertidal zone, depositing sediments that decrease in grain-size when traced from low- to high-water mark. Secondary agents such as waves and organisms modify this simple arrangement. The deposits of each sub-environment are thought to develop as sheet-like units over these to seaward, the creek and bordering region units cutting across them perpendicularly to the shore. The floors of the North Sea and the Wash and the eroding boulder-clay cliffs and adjacent sea-floors, of Lincolnshire to the north and Norfolk to the east, are thought to be the chief sources of the sediments.
The Foraminifera and stratigraphy of the Melinau Limestone, Sarawak, and its importance in Tertiary correlation
Authors: ADAMS CHARLES GEOFFREY
Published: October 2009

The stratigraphy of the Melinau Limestone, a pure shallow-water carbonate deposit in north-east Sarawak with a maximum thickness of about 7000 ft, is described. Dating of this sequence is based almost entirely on larger Foraminifera. The changing faunal succession from Upper Eocene through the Oligocene into the Lower Miocene is described and discussed. The probable conditions of deposition are considered and a correlation between the Melinau Limestone sequence and other limestone successions elsewhere in Sarawak is proposed. The criteria usually used for dating mid-Tertiary sediments of similar type in the Tethyan region are reviewed, and an attempt is made to correlate the Melinau succession with comparable successions elsewhere in Indonesia, the Pacific, India, and the Middle East. One new genus,
Wilfordia,
and three new species of Foraminifera,
Dictyoconus melinauensis, Neoalveolina inflata,
and
Wilfordia sarawakensis,
are described.
Dictyoconus
is recorded for the first time from strata of Oligocene age.