bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between gold and manganese mineralizations in the Birimian of Ghana, West Africa
Authors: Ntiamoah-Agyakwa Y.
Published: May 2009

Studies on the distribution of manganese-bearing rocks in the Birimian and their relationship with gold mineralization are still in progress. Both manganese and gold occur as stratabound lenses within volcano-sedimentary sequence. Evidence of pre- and post-tectonic mineralizations are present. Sedimentological evidence also suggests both may have been contemporaneous with their host rocks in an environment that was strongly Eh and pH controlled. Under present tropical conditions, other elements associated with Birimian gold mineralization, notably copper and arsenic, are highly mobile to remain in residual soils. However, manganese, like iron, remains in residual soils as oxides and could be a useful pathfinder element in the search for gold in tropical lateritic soils derived from Precambrian greenstones.
Influence of organic reefs on the evolution of post-Palaeozoic algae
Authors: Elliott G. F.
Published: May 2009

In reviewing those fossil algae associated with biotic reefs since the beginning of the Mesozoic, examples are discussed of algae showing evolution attributed to reef or peri-reefal conditions, those showing diversification attributed to reef environments, and those with frequent occurrence in reef conditions but with evolution not directly attributable to reefs.
The formation of fibrous texture in some veins
Authors: Finlow-Bates T.
Published: May 2009

Evidence is presented that some fibrous veins may be formed by recrystallization of the original rock in place. It is suggested that water in a joint promotes pressure solution of the adjacent wall rock. Redeposition under conditions of tensile strain crystallization causes growth of crystal fibres into the joint and into the wall. The effects of this process are revealed by reference to fibrous veins that are present in the laminated, dolomitic, quartz sediments at Mount Isa Mine.
Early Tertiary bentonites from Svalbard
Authors: Dypvik H. , Nagy J.
Published: May 2009

Paleontological and petrological studies of clay beds in the Basilika Formation (Tertiary age) are presented. The petrology of the beds indicates that their main constituents were derived from volcanic activity and represent bentonites. Differing composition between beds suggests several spatially separated eruptions. The volcanic source area probably lay towards the N of the present Tertiary outcrops of Svalbard. Two foraminiferal assemblages are found in the bentonites: the lower is dominated by arenaceous forms while the upper consists of calcareous species.
Intercumulus igneous layering in the Kalka Layered Intrusion, central Australia
Authors: Goode A. D. T.
Published: May 2009

Igneous layering resulting from variations in intercumulus mineralogy has been observed in the Kalka Intrusion in central Australia. The layering is parallel to cumulus layering, and is outlined by a mottled heteradcumulus ‘clump’ texture in leucogabbros, which occur in a generally adcumulate anorthositic sequence. Such intercumulus layering is thought to originate in slow cooling intrusions at times of slow crystal accumulation and/or relatively high rates of intercumulus crystallization when a zone of melt supersaturation (the cumulus nucleation zone) rises above the intrusion floor leaving the intercumulus melt undersaturated with respect to the settled cumulus phases. Adcumulates are produced when the supersaturated zone is coincident with the top of the crystal pile. The morphological elongation of clump plates parallel to the gross layering is probably controlled by the cumulus plagioclase fabric which tends to be planar laminate.
Surface roughness measurements and the analysis of petrofabrics
Authors: Deelman J. C.
Published: May 2009

A technique is described for direct analysis of rock-fabric, utilising hardness differences between various mineral constituents. This renders unnecessary the intermediate step of measuring optical orientations. The direct relation that exists between hardness of the components making up a particular fabric and the start of plastic deformation of each mineral can be measured quantitatively on the basis of polishing hardness differences. If the surface roughness signal is digitalised, then it is possible to automatically construct a microtopography, with contours delineating resistance of individual minerals.
A Precambrian trondhjemite boulder in Palaeozoic mudstones of NW Malaya
Authors: Stauffer P. H. , Snelling N. J.
Published: May 2009

A boulder of plutonic igneous rock, petrologically perhaps best termed a trondhjemite, which occurs as an isolated megaclast in slumped mudstones of the Singa Formation (mainly Carboniferous) at Pulau Tepor off NW Malaya, has been dated by the potassium–argon method. Two feldspar fractions, thought to represent alkali feldspar and plagioclase (though both are highly sodic) yield ages of 1029±15 Ma and 575±10 Ma, respectively, while a whole-rock sample yields an age of 264±4 Ma. The highest age is taken to give a minimum age for the rock, and the lower ages to indicate differential argon loss. This is the first radiometrically proved Precambrian rock from the Malay Peninsula, and tends to reinforce earlier inferences of a Precambrian continent as a source area for Palaeozoic sediments in the region.
Rb-Sr and U-Pb isotopic ages of granites in the central Transantarctic Mountains
Authors: Gunner J. , Mattinson J. M.
Published: May 2009

Granitic rocks in the central Transantarctic Mountains were emplaced and crystallized during the Early Ordovician Period, as indicated by Rb-Sr whole-rock isochron dates (488 and 463 Ma) and a concordant U-Pb date on sphene (476 Ma). Other U-Pb data provide evidence for an old inherited component of zircon in the granites.
New fusulinid evidence for the Permian age of the Palaeozoic rocks of Hydra, Greece
Authors: Stow D. A. V.
Published: May 2009

The Palaeozoic rocks of Hydra consist of a sequence of limestones and dolomites with some interbeds of shales and sandstones. Fusulinid foraminifera indicate the sequence is entirely Permian in age and not Carboniferous and Permian as previously thought.
Direct evidence of present-day serpentinization in the Jimberlana Intrusion, Western Australia
Authors: Campbell I. H.
Published: May 2009

Four vertical holes drilled into the olivine cumulates of the Jimberlana Intrusion all show a decrease in serpentinization with depth, suggesting that serpentinization can be a low temperature, present-day process.
Comparison of experimental and natural boudinage
Authors: Sen R. , Mukherjee A. D.
Published: May 2009

Strain distribution inside an elliptical shaped boudin under normal compressive stress is calculated by photo-elastic methods following Frocht (1966). The strain magnitude varies horizontally within the boudin and the value increases gradually from the central part of the body to the margin. The magnitude is nearly constant along the vertical central part of the boudin. Around the margin, inside the body, it shows an average value of the vertical and horizontal stress magnitudes. No actual change in the direction of shearing stress in different parts within the boudin is noted, hence no directional change of strain. Petrofabric diagrams of different parts of natural boudins showing the quartz (0001) plots, indicate no variation in the pattern of orientation in different parts of the body. However, the elongation ratio of quartz grains shows a correspondent increase with the increment of stress magnitude as noted in the experiments.
Flora and vertebrate fauna of the Barrington Beds
Authors: Gibbard P. L. , Stuart A. J.
Published: May 2009

Pollen analyses from sediment adhering to fossil mammalian bones from Barrington, Cambridgeshire, have demonstrated that the deposit is of Ipswichian zone IIb age. This is also indicated by the mammal fauna. Herb-dominated communities, which appear to have been largely maintained by the activities of herbivorous mammals, grew locally on the river floodplain, whilst temperate mixed-oak forest was present further away.
Hexactinellid faunas in the Chalk of England and Ireland
Authors: Reid R. E. H.
Published: May 2009

The Chalk of England contains three main Hexactinellid faunas, of Lower Cenomanian, Middle and Upper Turonian, and Lower Senonian to Maestrichtian age respectively. The third is also represented in Ireland. A number of minor faunal changes can also be recognized. The three main faunas have little in common, and their relationship is not evolutionary; the changes appear to be due to migrations. By analogy with modern forms, this is likely to reflect changes in the pattern of current circulation in the Upper Cretaceous ocean.
Sedimentology of the Ghazij Formation, Harnai, Baluchistan
Authors: Kazi A.
Published: May 2009

A petrographic study of the sediments of Ghazij Formation, supplemented by field observations, has been made with a view to studying the environment of sedimentation in the Ghazij Basin. It is concluded that the sediments were formed in marine and fluviatile environments. The principal source area lay to the north-west of Harnai and a palaeogeographic reconstruction of Ghazij times is attempted.
Alignment of dolines north-west of Lake Constance, Germany
Authors: Matschinski M.
Published: May 2009

An account is given of the karst features of a given area, and ways of finding some order in their apparently chaotic arrangement. The simplest characteristic to study is the alignments of the karst features. These can be determined either subjectively (following the simple overall impression given by the area), or objectively (on the basis of various mathematical or graphical operations).

A distinction between “local” and “general” alignment by an elementary statistical-graphical method is proposed. This method is applied to the Lake Constance area, and the results are interpretated in relation to the geological features of the area. It is concluded that (a) the structural features of an area have a strong influence on the karst phenomena, and (b) there is a possibility of revealing, and even making geometrical determinations of, some geologically fundamental directions, e.g. tectonic—from an analysis of the distribution of such relatively superficial phenomena as karst features.
An analysis of cross-stratification of Gargaresh Calcarenite (Tripoli, Libya) and Pleistocene palaeowinds
Authors: Hoque Mominul
Published: May 2009

The Pleistocene Gargaresh Calcarenite is a series of fossil dunes parallel to the Mediterranean coast of Tripoli; it is composed of medium-grained skeletal carbonate sand with abundant cross-stratification. Analyses of 321 azimuthal readings show that the distribution is bimodal with modes in the NE and the SE sectors. The distribution of modes indicates that the morphology and the orientation of eolian dunes were largely controlled by the then prevailing winds, and that the overall palaeowind pattern, although generally similar to the present-day system, might have undergone periodic changes due to Pleistocene climatic ups and downs.
Wenlock plant spores and tetrads from County Mayo, Ireland
Authors: Smith David G.
Published: May 2009

A rock sample from the Lettergesh Formation, most probably from the centrifugus Zone of the early Wenlock on graptolite evidence, has yielded microfossils including spores, most of which occur in tetrads. The spores are described and illustrated and are compared with Ambitisporites avitus Hoffmeister.
Caradoc turbidites at Poppit Sands (Pembrokeshire), Wales
Authors: James D. M. D.
Published: May 2009

The sedimentology of a key locality in the Caradoc of SW Wales is discussed for the first time. Five facies are described and interpreted: mudstones and siltstones (A), turbidite arenites (B), rudites (C), a diamictite of massflow origin (D), and muddy arenites rich in shaleclasts (E) which show a transition from massflow deposits to immature turbidites. Closely adjacent sections illustrate considerable lateral variations within an assemblage suggested to be of proximal turbidite character and to represent deposits high on a Middle Fan environment.
The Silurian and Lower Devonian graptolite-bearing strata in the USSR (a review)
Authors: Koren' Tatjana N.
Published: May 2009

The Silurian and Lower Devonian graptolite-bearing strata are widely distributed in both the platform and geosynclinal areas in the USSR. They are represented by black clay and siliceous shales, marlstones and argillites. In the main area of their distribution the regional zonal standard is established based on graptolites. They serve as the most detailed stratigraphical base for geological mapping and exploration and are used in the regional and inter-regional correlations. Correlation with other countries and continents is carried out by comparison of regional zonal successions with the unified standard of graptolite zones. The latter is compiled from the regional zonal subdivisions of the British, Czechoslovakian and Polish type sections. The zonal stratigraphy based on graptolites allows the establishment of the limits of the Silurian System and Stages/Series in the USSR. The Silurian and Lower Devonian sediments in the USSR are characterized by various geographically widespread graptolite assemblages. The most complete zonal subdivision is worked out for the Lower Silurian. The Upper Silurian and Lower Devonian zonal stratigraphy requires elaboration and precision in the future. The importance of graptolites in solving general geological problems particularly for establishing detailed stratigraphy of regions of industrial explorations considered.
A palaeomagnetic argument concerning post-Devonian displacement along the Great Glen Fault
Authors: Turner P. , Tarling D. H. , Archer R , Donovan R. N.
Published: May 2009

The validity of using Devonian palaeomagnetic data to determine a post-Devonian displacement along the Great Glen Fault is assessed and it is concluded that there is no statistically significant difference between previous magnetic vectors E and W of the fault and thus no palaeomagnetic evidence for a large sinistral displacement in post-Devonian times. New palaeomagnetic results are presented which suggest that the Devonian red sandstones in the Orcadian Basin have such a complex diagenetic and palaeomagnetic history that they will then be unsuitable for such tectonic evaluations in the foreseeable future, although palaeomagnetic dating can be used to resolve some diagenetic-sedimentary features.
Cleavage formation in the Skiddaw Slates of the Northern Lake District, England
Authors: Roberts D. E.
Published: May 2009

Cleavage structures from two localities in the Northern Lake District, England, are described, and they are discussed critically in relation to the tectonic de-watering hypothesis. It is concluded that, whilst tectonic de-watering may aid in the formation of a slaty cleavage, strain is the primary mechanism for producing such structures.
Non-metals in soils of the Teign Valley of SW Devon as indicators of mineral veins
Authors: Merefield J. R.
Published: May 2009

Quantitative methods of X-ray fluorescence analysis have been employed to the determination of Pb, Zn, Ni, As, Rb, Ce and Y, in soils of the Teign Valley of SW Devon. The results enable a comparison to be made of the ore metal and non-metal anomalies found, and demonstrate the applicability of non-metals as lode indicators.
Potassium–argon ages from the Tertiary Ring Complexes of the Ardnamurchan Peninsula, Western Scotland
Authors: Mitchell J. G. , Keen K. P.
Published: May 2009

Potassium–argon age studies on the central intrusion complexes of Ardnamurchan, Western Scotland, indicate that they were emplaced at a time between 59 and 61 Ma ago. The time period associated with the cooling was probably less than of the order of a million years. The temporal setting of the Ardnamurchan complexes in the context of the other British Tertiary igneous centres is examined in the light of the new data.
The Contact Relationship of Charnockite and Biotite Gneiss at Bauchi, Northern Nigeria
Authors: Oyawoye M. O.
Published: May 2009

Petrographic and chemical study of biotite gneiss and charnockite and the gradational transition zone between them suggests three probable modes of origin: (i) that charnockite was regionally widespread and the biotite gneiss was derived from it by retrograde metamorphism; (ii) that the charnockite represents a conformable intrusive igneous rock which with biotite gneiss was subjected to high-grade metamorphism; (iii) that the charnockite was derived from the biotite gneiss, by the introduction of some ferrous-iron rich juvenile solution.

The latter is preferred by the author because it explains better the physical, chemical, and mineralogical characteristics of the charnockite.

Evidence is presented to show that the hornblende in the charnockite was not due to retrograde metamorphism and the conclusion is drawn that the crystallization of hypersthene is not evidence of dry conditions of metamorphism.
On Geosynclinal Nomenclature
Authors: Kay Marshall
Published: May 2009

The geosynclines of North America were a subject of study and classification by the writer some twenty years ago. In the succeeding years, field studies have been directed toward solving some of the problems that appeared. The following is written to bring out the reasons why geologists from different regions, having differing experiences, reach conflicting opinions about relationships and terminology, and the history of the origin of some of the terminology has not been published previously.
The Structure of Brøggerhalvøya, Spitsbergen
Authors: Challinor A.
Published: May 2009

Brøggerhalvøya is situated on the north-west coast of the island of Vestspitsbergen. It is shown to contain a fold and overthrust complex of Tertiary age. Large northerly movement of Pre-Cambrian rocks, previously metamorphosed in the Caledonian diastrophism, occurred over deformed but unmetamorphosed Permo-Carboniferous and Tertiary rocks on a major curved over-thrust. The structure is complicated by rapid plunge variations and subsidiary faulting. The existence of a large klippe is demonstrated and the formation of curved thrust surfaces is discussed.

A brief summary of the stratigraphy is given and its important relationship to the structure discussed. A new lithostratigraphical scheme of nomenclature is proposed.
Graptolite Evidence for Rocks of Llandoverian (Silurian) Age in South-western Andorra
Authors: Oliver P. G.
Published: May 2009

Preliminary mapping of south-western Andorra has disclosed the presence of late Llandoverian graptolites in rocks of previously unknown age
The Cambrian Lower Boundary Problem
Authors: Rozanov A. Yu.
Published: May 2009

Based on the study of distribution of assemblages of skeletal organic remains we have established the synchronous appearance of a skeleton in certain fossil groups; this enables us to draw the lower boundary of Cambrian according to the first zone with a certain assemblage of skeletal fossils.

Wide distribution, in sections of various parts of the world, of deposits having no trilobites but containing similar assemblages of other skeletal fossils, has made it possible to distinguish them as an independent Tommotian stage. In Siberian sections this can be subdivided into three zones based on archaeocyathans.

The deposits of the Tommotian stage are underlain by deposits containing no skeletal fossils; in their carbonate composition they are, as a rule, rich in oncolites and catagraphs (algae of uncertain affinities or products of algal activity), and stromatolites of a socalled “Vendian” or “Yudomian” assemblage.

A regular distribution of assemblages of organic remains in the Cambrian-Pre-Cambrian boundary layers point to a leading role for a biostratigraphical method in the solution of the problem of the Cambrian lower boundary.
Deformation of Pebbles in Lower Old Red Sandstone Conglomerates Adjacent to the Highland Boundary Fault
Authors: Ramsay Donald M.
Published: May 2009

The deformation produced by the pre-Upper Old Red Sandstone movements on the Highland Boundary Fault in a zone close to the fault was sufficiently intense to rupture the pebbles in conglomerates. The patterns of pebble fracturing are similar in type and orientation over a wide area and are comparable with the patterns obtained in the experimental deformation of brittle materials. In experimental deformation a direct relationship has been established between the fractures and the causal stresses and so from a statistical orientation of the fractures in the pebbles the directions of the principal stresses can be deduced.

The principal compression in the vicinity of the Highland Boundary Fault acted N.W.–S.E. varying in places to N.N.W.–S.S.E., normal to the trend of the fault, while the least principal stress acted parallel to the strike of the fault.

The orientation of the least principal stress parallel to the direction of the fault in the conglomerates arises through increased stress in a vertical direction due to the nature of the downbuckling of the rocks on the southern side of the fault.

The orientation of the maximum compression confirms the Highland Boundary Fault as a reverse fault of late Caledonian age rather than a Proto-Armorican wrench fault produced by N.N.E.-S.S.W. compression.
An Analysis of the Areal Distribution of Soil Size Facies on the Lower Greensand Rocks of East-Central England by the Use of Trend Surface Analysis
Authors: Chorley Richard J.
Published: May 2009

Progressive fitting of linear, quadratic and cubic partial trend best-fit surfaces to median grain size (X1, in mm.) and percentage of silt and clay sizes (X3) of soil samples taken from fifty locations on the Lower Greensand outcrop between Ely and Leighton Buzzard in east-central England permit up to about 40 per cent of the total sums of squares to be “explained”. The successively higher levels of mathematical generalization of regional soil size distribution indicate a decrease in soil grain size towards the south-east, a disparity between the alignment of the soil facies and the strike of the present outcrop, and the existence of zone of abnormally coarse soil facies just to the west of the line of the rivel Ivel. These three features of the regional distribution of soil sizes are interesting in that they correlate with observations which have been made on the regional distribution of bedrock size facies. Finally, a suggested correlation is made between the local zones of small median grain size and abnormally high proportions of silt andclay soil sizes—isolated as “deviations or residuals” from the fitted regional surfaces—and localities where small admixtures of glacial drift (evidenced by the presence of flints) have been observed.
Strain Slip Cleavage in the Ordovician Sediments of Central Victoria
Authors: Beavis F. C.
Published: May 2009

At a late stage of folding, strain slip cleavage was imposed on the pelitic sediments of the Ordovician greywacke-slate association in Central Victoria. The nature of the cleavage surfaces was controlled by the type of sediment in which they were developed. In the coarser siltstones, and in the interlaminated zone of oscillatory graded beds, they are second order shear zones. In the finer siltstones and slates they are thin continuous shear domains of the first order.
The Stratigraphical Nomenclature of the Lower and Middle Jurassic Rocks of the Hebrides
Authors: Morton N. , Hudson J. D.
Published: May 2009

The stratigraphy of the Lower and Middle Jurassic rocks of the Hebrides is briefly summarized, and the lithostratigraphical nomenclature reviewed. To replace the inappropriate name “Inferior Oolite” for the lower marine part of the Middle Jurassic a new name, Bearreraig Sandstone Series, is proposed. This series is defined, and the succession at the type section is summarized.
Magnetic Grain Fabric Studies of the Middle Coal Measures of the Southern Part of the South Staffordshire Coalfield
Authors: Iorwerth H. ab , Hamilton N. , Loveland P. J.
Published: May 2009

Measurement of the anisotropy of magnetic susceptibility of Westphalian sandstones from the southern part of the South Staffordshire Coalfield shows that there is a weak preferred grain orientation. There is a significant within-sample consistency of fabric lineation and the results agree with other geological evidence. The palaeocurrent pattern is complex as may be expected within a fluvial or deltaic regime. This preliminary study suggests that this magnetic fabric technique may be used to determine the detailed palaeocurrent pattern within the Upper Carboniferous of the Midland Province.
Contraction Crack Networks in Basalt Flows
Authors: Smalley I. J.
Published: May 2009

The traditional concept of contraction crack formation is based on a model having a regular arrangement of stress centres. A more realistic result is produced if the model consists of a close random packing of stress circles; this gives a crack configuration very close to that observed in real basalt flows.
Tertiary and Cretaceous sediments in solution pipes in the Devonian Limestone of South Devon, England
Authors: Brunsden D. , Doornkamp J. C. , Green C. P. , Jones D. K. C.
Published: May 2009

Large sediment-filled solution pipes in Middle Devonian Limestone near Newton Abbot are described. A succession of gravels, sands and clays is identified in the pipes, and the presence of umber, ochre and residual clays is noted. The unusually large size of the pipes is discussed and the infilling sediments are related to the Cretaceous and Tertiary formations of the nearby Bovey Basin and Haldon Hills.
Greenstone assimilation by tonalite magma, Atikwa Lake, Ontario
Authors: Heimlich R. A.
Published: May 2009

In the Atikwa Lake area biotite tonalite grades into a peripheral zone of hornblende tonalite as the contact with greenstone wallrock is approached. Greenstone inclusions, common within the hornblende tonalite, exhibit varying degrees of digestion and the host becomes more mafic near many such inclusions. The hornblende tonalite is more heterogeneous than the biotite tonalite, particularly near the contact with greenstone where inclusions are abundant. Modal analyses indicate the presence of large amounts of hornblende near the contact. Spectrographic analyses of composite tonalite samples show that silica decreases while alumina, iron oxide, magnesia, lime, titania, nickel, chromium, and vanadium increase toward the contact. As a whole the data support the conclusion that the peripheral hornblende tonalite is a contamination product which resulted from the assimilation of greenstone by intruding biotite tonalite magma.
Zonal schemes in ancient ignimbrites
Authors: Lock Brian E.
Published: May 2009

Zonal arrangements in ancient ignimbrites have usually been interpreted as a reflection of variations in welding. Detailed study of two Lower Palaeozoic ignimbrites from Newfoundland demonstrates that crystallization zones can also be recognized and that in some cases it is these zones which are responsible for the gross features of the cooling unit.
Reinterpretation of the Aravalli basal conglomerate at Morchana, Udaipur district, Rajasthan, western India
Authors: Naha K. , Majumdar A.
Published: May 2009

The supposed Aravalli basal conglomerate near Morchana, considered to mark an erosional unconformity above the older Precambrian Banded Gneissic Complex in central Rajasthan, is a tectonic mélange in a terrain involved in superposed deformations. The supposed pebbles represent tectonic inclusions of various shapes, formed by isoclinal folding, stretching and disruption of concordant, pre- or early-kinematic vein quartz and rare pegmatite sheets in the Aravalli mica schist during the first folding.
Aeolian cross-stratification in the Devonian of the Dingle Peninsula, County Kerry, Ireland
Authors: Horne Ralph R.
Published: May 2009

Cross-stratified units, of the order of 1 to 12 m thick, are described from the Devonian Slieve Mish Group in the Dingle Peninsula of south-west Ireland. They are composed entirely of purplish-red or yellowish-grey and violet, medium- to fine-grained sandstone. An aeolian origin for this cross-stratification is indicated by the large size and morphology of the fore-sets, the excellent sorting of the sandstones and the associated evidence of aridity in a continental environment within a restricted basin.
Orford, Suffolk: Further Data on the Quaternary Evolution of the area
Authors: Carr A. P.
Published: May 2009

Boreholes at, and seaward of, Lantern Marshes shed additional information on the Quaternary evolution of the Orford, Suffolk, area. The logs indicate:

(i) a more complex surface to the London Clay, which is shown to reach depths below those formerly thought;

(ii) the reality of the lower planation surface previously recorded. The surface is, however, cut across Scrobicularia and Butley (Red) Crag to a greater extent than anticipated. It proves that at least part, and probably all, of the −8.5 to −11 m surface is post Ludhamian.

(iii) a peat sample from −9.4 m indicates that relative mean sea level at 7010 B.P. was at approximately −10.7 m. The peat is overlain by shingle and confirms the residual shingle structures as later than that time.
A note on an analcite-bearing lamproite from Devonshire
Authors: Velde Danielle
Published: May 2009

The olivine minette described by Tidmarsh from the Holmead Farm, Lox-beare, contains analcite microphenocrysts in addition to olivine, biotite, clinopyroxene and alkali-feldspar. A new chemical analysis shows that the rock is undersaturated with respect to silica. This is still another example of analcite occurring in a potash-rich rock.
Particle rounding in beach gravels
Authors: Bluck Brian J.
Published: May 2009

Splitting, crushing and spalling which occur when boulders move against each other, generate fine material and so give rise to angular large and small sizes. The nature of the rounding process can be deduced from the analysis of moments of the roundness frequency distribution of the size range 4–128 mm. A low standard deviation indicates the dominance of one process—either abrasion or breakdown; a high standard deviation indicates the presence of both. The relationship between mean roundness, standard deviation of roundness, skewness of roundness and mean size allows for an analysis of the size reduction processes at work on the sediment; and for a comparison between the reactions of different rocks. A model, based on actual data, is given for the evolution of roundness of limestone clasts on a beach.
On the usage of nepheline-basalt, olivine-nephelinite, olivine-nemafite, and similar rock names
Authors: Morgan W. R.
Published: May 2009

The usage and synonymity of the names of some olivine-bearing feldspathoidal extrusive rocks is discussed. In the nephelinic rocks it is suggested that the terms nepheline-basalt and olivine-nemafite be abandoned, and that the use of olivine-nephelinite be continued. A similar recommendation is made for other feldspathoidal rocks.
Mafic hybrid rocks from the New England Batholith, New South Wales
Authors: Phillips Evan R.
Published: May 2009

Intrusion of an adamellite with K-feldspar megacrysts into metadolerite wall-rock has produced a hybrid rock with K-feldspar porphyroblasts and quartz “ocelli” rimmed by hornblende. This indicates a high-level development of the feldspar and suggests that mafic contamination is an important factor in the genesis of the xenolith-rich porphyritic adamellite.
The Basal Rocks of the Tertiary at Uloa, Zululand, South Africa
Authors: Frankel J. J.
Published: May 2009

At Uloa in Zululand a nodule bed is the basal formation of a thin group of Tertiary sediments that rests on nearly horizontal Senonian silty mudstones. It contains mammillary, botryoidal, and cylindrical nodules, remanié Lower and Upper Cretaceous mollusca all ferruginized and partly pyritized, silicified Cretaceous wood, worn Tertiary sharks' teeth, and cetacean bone, phosphatized nodules of both Upper Cretaceous and Victoriella-bearing Eocene, and Tertiary glauconitic sandstone pebbles dated at 55 million years.

A coquina-like limestone (“Pecten Bed”) overlies the irregular upper surface of the nodule bed disconformably. Consideration of some of the megafossils, the absence of larger Foraminifera, and the presence of Orbulina universa suggest that the “Pecten Bed” is Middle to Upper Miocene in age.

Alternations of coarse and fine grained calcarenite layers that overlie the “Pecten Bed” disconformably, may be of youngest Miocene age.

The nature of the Tertiary rocks suggests shallow water sedimentation from the Eocene to latest Miocene, with several periods of transgression and regression, and slight epeirogenic or eustatic movement only.
Metamorphosed Lamprophyres and the Late Thermal History of the Moines
Authors: Johnson M. R. W. , Dalziel I. W. D.
Published: May 2009

Certain lamprophyres in Moidart exhibit at least three sets of minor structures (cleavages, lineations and small-scale folds). During the formation of the first set the lamprophyres acquired a schistose fabric: hornblende and biotite laths crystallized along the axial surfaces of tightly compressed folds. The deformation episodes recognized in the lamprophyre sheets post-date the main episodes of major and minor folding (F1-F3) that affected the surrounding Moine gneisses. The existence of a metamorphic fabric in these lamprophyres raises interesting problems—was the thermal energy required to “metamorphose” the lamprophyres derived from deformational heat, or by a heat flow from the Moine country rocks, or were the lamprophyres deformed during cooling and consolidation from the magmatic state (autothermal metamorphism) ?
Joints: Their Initiation and Propagation with Respect to Bedding
Authors: Hill Patrick Arthur
Published: May 2009

Joints (fractures) are propagated from areas of high to areas of low stress. They may originate at inhomogeneities on, or by slickensiding along bedding planes. Plumose marks on the surfaces of joints radiating from volcanic, meteor, or man-made explosion craters should, in stratified rock, reveal whether the joints were propagated with their leading edge convex or concave forward.
The Structure of the North Island of New Zealand
Authors: Lauder W. R.
Published: May 2009

The structure of the North Island of New Zealand is dominated by a central volcanic high with girdles of Tertiary sediments concentrically about it.
F1 Cross-folding in the Manx Slate Series, Isle of Man
Authors: Simpson Alexander
Published: May 2009

The acute F1 folds in the Isle of Man possess Caledonoid axial planes and plunge predominantly to the north-eastern or south-western quarters at a low angle. Synchronous F1 cross-folding is locally developed and plunges steeply to the north-west or south-east. The axial planes of these acute structures have the same steep Caledonoid orientation as their orthodox associates and they share the same first axial-plane cleavage (S1). The generation of the cross-folding is related to original culminations and depressions in the Caledonoid hinges of the large-scale F1 folds. Comparison is made with early cross-folding in other parts of the Caledonides.
Centre-finding in Systems of Lines
Authors: Frost Michael J.
Published: May 2009

Methods for studying the geometry of radiating and concentric features are described and compared. The method favoured for radiating features is to assume that the straight lines, which represent the trends of the features, are of infinite length. Then, for each point on a grid, calculating the mean of the perpendicular distances from the point to each of the lines. These values are then contoured, and a centre minimizing the value of the mean estimated visually.

The methods are applied to finding the centre of the Lyttelton volcano from the external contours and finding a radiation centre for its radial dykes.
Chronostratigraphy and Biostratigraphy
Authors: Hedberg Hollis D.
Published: May 2009

Comments are given on a number of papers dealing with principles and procedure in stratigraphic classification which have appeared in British journals during 1963–65. It is emphasized that a clear distinction should be made between biostratigraphic units—bodies of rock strata characterized by certain palaeontological features and bounded by the limits of known occurrence of such features—and chronostratigraphic units—bodies of rock strata characterized by representing the rocks formed during certain time-spans of earth history and bounded above and below by isochronous surfaces. Biostratigraphic zones and the chronostratigraphic terms chronozone and stage are discussed.
A Spiral Brachidium in the Jurassic Chonetoid Brachiopod Cadomella
Authors: Cowen R. , Rudwick M. J. S.
Published: May 2009

A spiral brachidium has been discovered in the Lower Jurassic brachiopod Cadomella, which is generally regarded as the last representative of the Chonetidina. Cadomella is transferred to the Koninckinidae, which are considered to be spire-bearing Chonetidina rather than aberrant Spiriferida. This interpretation implies another independent evolution of spiralia within the Brachiopoda.
Structures in the Upper Purbeck Beds at Peveril Point, Swanage, Dorset
Authors: Cosgrove M. E. , Hearn E. W.
Published: May 2009

Structures in the Upper Purbeck Beds at Peveril Point, Swanage, Dorset, are described. Interpretation of the overall structural pattern has been attempted by constructing a three-dimensional model of the Broken Shell Limestone surface, upon which the more complex folding of the shales and marbles has taken place. The regional setting of the structures is discussed.
A Study of the Potash Felspar Gneisses of Connemara and Felspar Comparison with the Galway Granite
Authors: Leggo P. J.
Published: May 2009

Eighteen potash felspars from the potash felspar gneisses of the Connemara migmatite belt have been partially analysed and the associated plagioclase optically determined. Comparisons have been made with seventeen similar felspar pairs from the Galway Granite. Albite components are expressed graphically in an attempt to illustrate sodium distribution between associated felspar phases. On such a plot it is possible to contrast the “magmatic” felspars of the Galway Granite with those of the migmatitic gneisses; the separation of the two fields being a function of total rock chemistry. Crystallization temperatures have been determined by the two felspar method and the range 460 to 480° C. is thought to represent retrograde amphibolite conditions in the migmatitic gneisses, while petrographic evidence supports 550° C. as the temperature of amphibolite facies metamorphism in these rocks. Triclinicity measurements have also been made on the analysed potash felspars.
Initial melting in alkali feldspar-plagioclase-quartz systems
Authors: Weill Daniel F. , Kudo Albert H.
Published: May 2009

The beginning of melting of mineral assemblages of alkali feldspar, plagioclase and quartz in the system Ab-Or-Q-An cannot be treated in terms of eutectic points in subsystems which are defined on the basis of the ratio Ab/ An. Such subsystems do not exhibit unique melting temperatures or unique compositions of the first liquid produced. It is shown theoretically and demonstrated experimentally that these three minerals may coexist with liquid over a considerable portion of the melting range.
Pre-tectonic metamorphic crystallization in the Mt. Lofty Ranges, South Australia
Authors: Fleming P. D. , Offler R.
Published: May 2009

Evidence for the growth of andalusite and staurolite porphyroblasts prior to the first penetrative movements in the rocks of the Mt. Lofty Ranges is presented. The implications of this unusual observation are discussed.
The Jimberlana Norite, Western Australia – a smaller analogue of the Great Dyke of Rhodesia.
Authors: Campbell I. H. , McCall G. J. H. , Tyrwhitt D. S.
Published: May 2009

The Jimberlana Norite Intrusion, situated near Norseman, Western Australia, is the first real analogue of the Great Dyke of Rhodesia to be discovered. The intrusion has the external form of a dyke, extends for at least 180 km (112 miles), has a maximum width of 2.5 km (1.5 miles), and follows the general easterly trend of the other members of the Widgiemooltha Dyke Suite, all of which have so far revealed characteristics of true dykes. It has a very steep funnel-shaped cross-section, like the Great Dyke, and shows many internal, canoe-shaped complexes along its length, consisting of cumulate ultramafic and basic rocks together with minor acid differentiates. The ultramafic and basic rocks display phase, rhythmic and cryptic layering. The differentiation sequence from ultrabasic to basic rocks is repeated more than once, and therehave clearly been several pulses of magma up the tensional opening. This is confirmed by the recognition of at least two magmatic unconformities. The broader petrogenetic questions posed by this unusual intrusion are discussed.
Tectonic ripples and associated minor structures in the Silurian rocks of Denbighshire, North Wales
Authors: Warren P. T. , Harrison R. K. , Wilson H. E. , Smith E. G. , Nutt M. J. C.
Published: May 2009

Structures affecting certain bedding planes, and simulating sedimentary ripples, have been found at a number of horizons in the Wenlock and Ludlow rocks of Denbighshire, North Wales. The megascopic appearance of the ripples, including their association with linear structures and their miscroscopical fabric are described in detail; and it is concluded that they are of tectonic origin, being manifestations of bedding-plane slip. The orientations of the ripples and other minor structures suggest that the stress responsible was the regional stress that produced folding, faulting and cleavage.
A method of contouring polar diagrams using curvilinear counting cells
Authors: Denness Bruce
Published: May 2009

A new method of contouring polar diagrams using 1% area curvilinear counting cells is described. The method is fast and accurate over the whole area of the stereogram including the periphery and is, therefore, especially suitable for counting weak or diffuse concentrations.
Sub-marine volcanic explosion during the sedimentation of the Baghdhar Limestone of Dalhousie Chamba, Himalaya
Authors: Saxena M. N. , Singh S. K.
Published: May 2009

Volcanic lapelli, bomb-like fragments and dust, along with other ejectamenta were incorporated in the limestone during its sedimentation. The limestone belongs to the Chail Series of Algonkian age. The volcanic explosion took place under sub-marine conditions.
A Note on Possible Differentiation Trends in Tertiary to Recent Lavas of Kenya
Authors: Wright J. B.
Published: May 2009

The distribution of Tertiary to Recent lavas in part of south-west Kenya is outlined, and attention drawn to the predominance of nepheline-rich Miocene lavas over other types west of the Rift Valley, which contrasts with the Pliocene olivine basalt-trachytecomendite association predominating within the Rift Valley. It is inferred that widespread Miocene phonolites west of the Rift Valley derived from a parent of approximate mela-nephelinitic composition, while within the Rift Valley extensive Pleistocene trachytes differentiated from an olivine basaltic parent. Plots of normative feldspathoid: feldspar versus silica, for analysed lavas from Kenya and Tanganyika, are used to illustrate the trends envisaged. The frequent association of nephelinitic lavas and carbonatite complexes in Kenya is discussed and the possibility mooted that the presence of nephelinite lavas may be indicative of nearby carbonatite complexes.
Significance of the punctation mosaic of the Jurassic thecidellinid brachiopod Moorellina
Authors: Baker P. G.
Published: May 2009

Study of the punctation mosaics of Moorellina granulosa (Moore) and Moorellina ornata (Davidson), revealed by serial sectioning and stereoscan photomicrographs, shows that the apparent random distribution of punctae may be reconciled to two superimposed regular insertion patterns. Careful plotting of the endopunctae of M. granulosa from serial, cellulose acetate peels, reveals the presence of impersistent punctae. A new model is proposed, based on superimposed insertion patterns and offering an explanation for impersistence of punctae.
Craton-Mobile Belt relations with particular reference to the Mosetse-Matsitama area, north-eastern Botswana
Authors: Bennett John D.
Published: May 2009

The Pre-Cambrian rocks of north-eastern Botswana comprise two major geotectonic domains: the south-western extremity of the Rhodesian craton, and the surrounding mobile belts– namely the Limpopo Mobile Belt to the south and the Shashi Mobile Belt to the west-southwest. The Mosetse-Matsitama area bears affinity to both these environments and this contribution attempts to assess the relationships of the area within the context of the regional geological framework. The area is underlain by a supracrustal schist belt which is interfolded with an infracrustal basement of gneisses and granitic rocks. The schist belt includes metasedimentary and probably metavolcanic rocks of low metamorphic grade and, therefore, contrasts sharply with the rocks of higher metamorphic grade which comprise the basement. Only in the south-west of the belt does a transitional relationship between the two major units occur. Geographical and geological criteria characteristic of both the major geotectonic environments are described, and it is concluded that the area shows a transition from a cratonic to a mobile belt environment. Involvement in a developing mobile belt would initially affect the infracrustal basement, allowing the supracrustal rocks to retain their cratonic characteristics to a more advanced stage.
Lava Channels on Tristan da Cunha
Authors: Baker P. E. , Harris P. G.
Published: May 2009

Lava channels flanked by lava levees are described from Tristan da Cunha. These have been formed by the building up of the levees by overflow and solidification of fluid lava from the channels. A distinction is made between the terms “lava levee” and “lava moraine”.
The Geology of the Dinas Cwm-Rheidol Hydroelectric Tunnel
Authors: Adams T. D.
Published: May 2009

The geology encountered in the driving of the Dinas Cwm-Rheidol Hydroelectric pressure tunnel is described.
Composite phonolite tholoids in the Cenozoic volcanic province of Nigeria
Authors: Wright J. B. , McCurry Patricia
Published: May 2009

Small trachyte and phonolite bodies are shown as eroded plugs on published geological maps of part of north-eastern Nigeria. Field relationships at two such ‘plugs’ strongly suggest them to be extrusive in origin, formed of an earlier tholoid-building phase, followed by extrusion of a spine (plug dome) of very viscous lava, now forming the central peak at each locality. Petrographic data show that the tholoid and spine-forming lavas are phonolites of contrasted composition. Eruption of salic lavas from scattered centres appears to have occurred intermittently between mid-Tertiary and Pleistocene times.
An alkaline igneous province in the North-West Frontier Province, West Pakistan
Authors: Kempe D. R. C. , Jan M. Qasim
Published: May 2009

Alkaline microgranites and granite, containing aegirine, riebeckite and astrophyllite, from north-west Pakistan, are briefly described, and tentatively correlated with other alkaline rocks in the region.
Surface textures of sand-grains from the Hertfordshire Pebble Gravels
Authors: Hey R. W. , Krinsley D. H. , Hyde P. J. W.
Published: May 2009

The Pebble Gravels of Hertfordshire are among the earliest Pleistocene deposits of the London Basin. They comprise at least three successive units, and according to the most recent published views the oldest of these is marine, the youngest fluviatile, the intermediate partly marine and partly fluviatile. In the absence of fossils these views have remained open to question. Electron microscope studies of the surface textures of sand-grains suggest, however, that they may well be substantially correct.
Deformed agglomerates near Tintagel, North Cornwall
Authors: Hobson D. M.
Published: May 2009

It is shown that fragments in agglomerates, which occur in chlorite schists near Tintagel, may have been both flattened and constricted. Flattening was probably associated with formation of the schistosity, and constriction with later boudinage.