bluuebunny/crossref_metadata_2025 huggingface dataset:
Procedures in vertebrate taphonomy; notes on a Uganda Miocene fossil locality
Authors: HILL ANDREW , WALKER ALAN
Published: December 2007

Before palaeoecological statements
are made concerning the assemblage of fossil vertebrates at a particular site it is essential to understand the factors which have controlled bone accumulation. In this way some allowance can be made for the biases which must inevitably cause a fossil collection to differ from the living community or communities from which it was derived. In addition to conventional sedimentological techniques and the study of fossils merely as the remains of animals this can be partly achieved by treating bones as an integral part of the sediment. Such studies are the concern of taphonomy (Gk.
tapho—
burial,
nomos
—law) which deals with the processes potentially leading to the fossil-ization of an animal (
Efremov 1940
).

The differences between a fossil assemblage and the original community are particularly great in the case of terrestrial vertebrates, which seldom accumulate in autochthonous circumstances. It is therefore surprising that techniques familiar in invertebrate palaeontology seem rarely to have been applied to terrestrial vertebrates, where perhaps there is a greater need. Most previous work is in fairly recent archaeological contexts, though
Voorhies (1969)
and
Dodson (1971)
provide more strictly geological examples. This note records an attempt to establish a number of simple parameters of a vertebrate assemblage. It is hoped that other workers may be able to supply similar, or suitably modified, information concerning vertebrate accumulations that they investigate, which will then provide a basis for useful comparison.

Bukwa II is an early Miocene fossil locality situated on the northeastern slopes of Mount
The Coastal Batholith of central Peru
Authors: COBBING EDWIN JOHN , PITCHER WALLACE SPENCER
Published: December 2007

A sector of the Peruvian Coastal Batholith 120 km long has been mapped in detail. Little altered volcanics of Cretaceous and Lower Tertiary age make up the bulk of the country rocks and these and their structures are flagrandy cross-cut by a great composite intrusion in which some 16 distinct petrographic units are distributed in many time separated plutons. Though tonalites bulk large, substantial volumes of basic and acid rocks are involved in a clearly marked basic to acid sequence, a primary rhytiim, in the distribution of which there is often a marked symmetry: gabbros on the flanks, tonalites and quartz diorites internally and in a medial position there are centred complexes in which adamellites are particularly important. Each of the main petrographic units involved a secondary rhythm of in situ, high level, differentiation in their emplacement. The adamellites have followed earlier arcuate basic intrusions and the resulting associations of multiple plutons and ring dykes are thought to represent the basal wrecks of volcanoes which were active over the entire intrusion history of the batholith. The space problem has not been fully solved and the resolution of this problem will depend on structural analysis of the envelope over a wide area. It has however been demonstrated that stoping and cauldron subsidence were important and because the attitude of many of the main contacts was controlled by contemporaneous fracturing it seems that a general uplift on faults may have provided some of the space for intrusion.
Letter to the Editor
Authors: TOGHILL P.
Published: December 2007

To the geologist Shropshire is a classical county. The endless variety of the county's rocks and fossils (every geological system except the Cretaceous and Tertiary is represented) has attracted geologists for nearly 200 years including some of the greatest names in British Geology: Murchison, Sedgwick, Salter, Lapworth, Cobbold, Whittard, to mention just a few. Shropshire villages and place-names are recorded in such classic terms as Longmyndian, Uriconian, Wenlock, Ludlow, Farlovian, Dittonian, Caradoc, etc. Almost every turn in a Shropshire lane reveals a place-name engraved in the mind of every geologist, or perhaps a view portrayed in Murchison's Silurian System. The varied geology gives Shropshire a unique and beautiful landscape, as yet relatively untouched, apart from the Coalbrookdale coalfield area, by urbanization.

The publications of the Institute of Geological Sciences; the Church Stretton memoir with its One-Inch map and the admirable new 2

1
2

Inch maps and guides; the Shrewsbury and Oswestry memoirs and One-Inch maps; the recent new editions of the regional guides for the Welsh Border-land and Central England; attract geologists and students to the county in ever increasing numbers. In addition 2

1
2

Inch maps of Telford New Town and the classical Ludlow area will be published soon.

These government publications are supplemented by earlier work of those listed above and by more recent work on the Ordovician by Dean, and the Silurian by Holland, Lawson and Walmsley and other members of the Ludlow Research Group. The Old Red Sandstone has been extensively studied by Ball, Dineley and White, and others.
A tectonic history of northwest England
Authors: MOSELEY FRANK
Published: December 2007

Northwest England has been affected by the Caledonian, Variscan and Alpine orogenies no one of which is entirely unrelated to the others. Each successive phase is partially dependent on earlierones, whilst structures in older rocks became modified by succeeding events. There is thus an evolutionary structural sequence, probably originating in a preCambrian basement and extending to the present.

The Caledonian episodes are subdivided into pre-Borrowdale Volcanic, pre-Caradoc and end-Silurian phases. The recent suggestions of a severe pre-Borrowdale volcanic orogeny are rejected but there is a recognizable angular unconformity at the base of the volcanic rocks. The ‘pre-Borrowdales’; trends and those of the pre-Caradoc movements are variable but are generally northerly and could be posthumous upon a pre,Cambrian basement. The end-Silurian structures include early
n
–
s
and later
ne
to
ene
folding.

The Variscan structures are in part determined by locations of the older massifs and in part they are likely to be posthumous upon older structures with important
n
–
s
and
ne
. elements. Caledonian wrench faults were reactivated, largely with dip slip movement.

The more gentle Alpine structures also follow the older trends with a
n
–
s
axis of warp or tilt and substantial block faulting. The latter was a reactivation of older fault lines and resulted in uplift of the old north Pennine massifs relative to the downwarped Irish Sea Basin and the Vale of Eden.
Lewisian sheets within the Moines around 'The Saddle' of northwest Scotland
Authors: SIMONY PHILIP S.
Published: December 2007

The Lewisian-like rocks occur in the Moines in three zones as sheets up to 150 m thick and intimately interlayered with Moine schists and psammites. They include metagabbro, amphibolite, migmatite, marble and laminated hornblende schist, the latter occurring mainly at the margins of the bodies and is a tectonite derived from the other rock types during the interlayering within the Moines.

The Lewisian sheets are demonstrated to be pieces of the pre Moinian basement tectonically emplaced within the Moine cover during the first of three phases of folding which affected the area. Two northerly zones areinterpreted as the cores of fold nappes having roots to the northwest of the area while the southerly zone is at the base of a thrust sheet, and marks the continuation of the Sgurr Beag slide in The Saddle area.
Fumarole temperature increases on the summit cone of Mount Etna, Sicily, 1972
Authors: GUEST JOHN E.
Published: December 2007

Fumarole temperature increases between March and September 1972 suggest a westward migration of magma from below the Bocca Nuova and a possible renewal of activity near the North East Crater.
Potassium-argon age determinations on some British Tertiary igneous rocks
Authors: EVANS ALED L. , FITCH FRANK J. , MILLER JOHN A.
Published: December 2007

The timing and duration of volcanism within each igneous province of the North Atlantic region during the Tertiary is required to evaluate possible relationships between this magmatism, plate tectonics and continental drift. Published radioisotopic dates from the British Tertiary volcanic province are listed and briefly reviewed in the context of the data available from other North Atlantic areas. New conventional K–Ar and
40
Ar/
39
Ar age spectrum ages of rocks from Mull, Staffa, Arran, Antrim, the Mountains of Mourne, Carlingford, the Cleveland dyke and the North Welsh dyke swarm are reported.

Volcanism began in the British Province around or just before 65–66 m.y. in the latest Cretaceous or earliest Palaeocene. The earliest episode of basalt lava eruption in Northern Ireland may not be represented in the Hebrides. The major plutonic centres are between 60 and 58 m.y. while minor activity continued at various localities until at least 50 m.y. in the Eocene.
A problematic reptile from the British Upper Trias
Authors: ROBINSON PAMELA L.
Published: December 2007

The adaptive significance of the structural changes that led to the differentiation, during the Triassic, of two important stocks of reptiles, the Lacertilia (lizards) and the sphenodontid Rhynchocephalia, is discussed. This provides a context for the consideration of the peculiar combination of characters found in a reptile,
Glevosaurus hudsoni,
from the Upper Trias of the Bristol Channel area, that has some structural affinities with each of these stocks.
Manganiferous stromatolites from the Precambrian of Botswana
Authors: LITHERLAND MARTIN , MALAN STEPHANUS P.
Published: December 2007

S
tromatolitic fragments
were collected by one of us (S. P. M.) from the ore stock piles of the Kgwakgwe Hill Manganese working, near Kanye,
se
. Botswana, southern Africa. Unfortunately the hand cobbing destroyed the external form of the structures, and despite subsequent visits to the locality it has not been possible to find any specimens
in situ.

The manganese deposits are found in an outlier of Precambrian sedimentary rocks which is correlated (
Boocock 1965
;
Crockett 1970
) with the Black Reef and Dolomite Series of the Transvaal System (c. 2000 m.y.). Although the sequence is thin and atypical of the standard succession, the manganiferous mudstones are over-lain by an undisputed Waterberg Succession and thus the upper age limit can be established with certainty.

The following generalized stratigraphic column gives some idea of the lithologies involved as well as the stratigraphic position of the stromatolite occurrence.

The manganese ores of Kgwakgwe Hill are found in two main modes of occurrence. In the first there is the laminated varve-like shale type ore which is variable in composition due to intermixed clays and, or, iron oxides. It is interlaminated with white kaolinitic shale, chert, layers of wad, shale and sandstone. The other consists of discrete nodules of pyrolusite and nsutite set in a light yellowish ironstained mudstone. These nodules, often concentrically laminated, may constitute up to 40 % of the rock and are concentrated along the faint bedding planes of the mudstone. They vary in composition from a high grade nsutite to a ferruginous
Transgressive welded ash-flow tuffs among the Ordovician sediments of NE Snowdonia, N. Wales
Authors: FRANCIS E. HOWEL , HOWELLS MALCOLM F.
Published: December 2007

In the type area, and southwest of it, the Capel Curig Volcanic Formation comprises up to three ash-flow tuffs interbedded with marine sediments. The tuffs are generally massive and welded, but pass laterally and upwards into current bedded, ripple marked tuffs. They are believed to have been deposited in a subaqueous environment, after originating from subaerial eruptions farther north where the Formation is represented by an uninterrupted sequence of intensely welded ash-flows. The lower contacts of the submarine ash-flows contrast with subaerial ash-flows in being welded and by locally transgressing the underlying sediments at angles up to 90°, with minor apophyses resembling magmatic intrusions. Eutaxitic foliation, however, remains generally parallel to the regional dip. The sediments adjacent to the transgressive undersurfaces are disturbed and reconstituted. The irregular contacts, together with adjacent discrete pipe-like tuff bodies are interpreted as down-sags analogous to load casts but of unprecedentedly large scale, up to 100 m, formed by the liquefaction and yielding of the sediments during and after the emplacement of the tuffs.
The application of quartile deviation-median diameter curves to the interpretation of sedimentary rocks
Authors: BULLER ANTONY T. , McMANUS JOHN
Published: December 2007

Textural differences between
present-day
sediments collected from fluviatile, beach and aeolian environments, can be demonstrated by plotting values of quartile deviation measures (QDa) against the medians (Md) on double-log paper for each environment. These plots can be delimited by trend envelopes whose bounding lines represent regressions one standard deviation either side of the average regression lines. Using these envelopes as a framework for comparison, several hundred QDa-Md plots calculated from the grain-size distributions of
ancient
sedimentary rocks have been examined. The majority of these plots fall well within their appropriate environmental envelope thereby demonstrating that the statistical technique is valid for the environmental discrimination of both modern and ancient deposits.
Torridonian tourmaline-quartz pebbles and the Precambrian crust northwest of Britain
Authors: ALLEN PERCIVAL , SUTTON JOHN , WATSON JANET V.
Published: December 2007

Exotic rocks found as pebbles in the Torridon Group span the range of Lewisian events (3000 to 1000 my. B.P.) but were formed at higher crustal levels than the present Lewisian. Their variations southward along the present outcrop seem to reflect changes in the basement as it is traced through Greenland towards Labrador. The new evidence is consistent with the views of previous workers. Tourmaline is used as a 'supracrustal index' and confirmed as a valuable dating mineral.
The structure of the Dalradian rocks in the SW Highlands of Scotland
Authors: ROBERTS JOHN L.
Published: December 2007

The structure of the Dalradian rocks between the Loch Skerrols Thrust and the Highland Boundary Fault in Scotland is related to a regional deformation history of eight fold phases. The first four phases are associated with the formation of early, but not necessarily recumbent, folds such as the Islay Anticline, the Loeb Awe Syncline and the Ardrishaig-Aber-foyle Anticline during the primary deformation. The subsequent phases of deformation are related to the development of secondary structures, such as the Tarbert and Ben Ledi Monoforms, which are superposed on the earlier structures. It is argued that the primary structures formed as a result of lateral compression acting at depth. However, as the Ardrishaig-Aberfoyle Anticline reached a high structural level it collapsed towards the southeast under the influence of gravity to form the anticlinal core to the Tay Nappe. This process was continued during the secondary deformation with the development of the Tarbert and Ben Ledi Monoforrns.
Syndepositional small-scale intrusions in Ordovician pyroclastics, Co. Waterford, Ireland
Authors: SCHIENER ELMAR J.
Published: December 2007

Within a predominantly pyroclastic succession are small-scale intrusive bodies and more extensive pillow lavas and pillow lava breccias of andesitic composition. Sedimentary structures in the vitric rhyolitic tufts intruded by magma, suggest contemporaneous deposition and intrusion. This seems to indicate that intrusion was close to the sediment-water interface. The juxtaposition of basic lavas and tuffs with the contemporaneous products of rhyolitic explosive activity is interpreted as evidence for a deep-water depositional environment, into which the bulk of the acid tufts were introduced by mass transport.
A palaeomagnetic study of Eocambrian tillites in Scotland
Authors: TARLING DONALD H.
Published: December 2007

Two main components of magnetization of the mid-Dalradian Port Askaig formation can be isolated of which one, at least, appears to have been acquired at the time of formation of the deposits. The magnetization was acquired while the rocks were in low palaeolatitudes, less than 10°s., which, if the glacial ice-cap origin is correct, would support the concept of a worldwide glaciation in Eocambrian times. The second component of magnetization appears to have been added in Ordovician-Silurian times during metamorphism, by which time the region was in a latitude of some 40°s. Comparison with coeval results for Greenland and Norway suggests that the proto-Atlantic was small at this time, in contrast to a wide Tethys Ocean. Further studies in the North Atlantic region are required to confirm these preliminary findings.
The petrography and origin of dedolomitized, veined or brecciated carbonate rocks, the ‘cornieules’, in the Fréjus region, French Alps
Authors: WARRAK MOHAMMED
Published: December 2007

Cornieules (or rauhwackes) are essentially dedolomitized, veined or brecciated carbonate rocks or marls with a characteristic porous to cellular appearance. In hand specimen, they can be divided into two types, those with a veined structure, and those showing a brecciated structure. In the Fréjus region and in most other areas both inside and outside the Alps, cornieules are restricted in occurrence to evaporitic sequences. They are frequently associated with gypsum or anhydrite, which suggests a genetic link between cornieule and evaporites. This was confirmed when a full petrographic investigation was carried out, first on a Triassic evaporite sequence and then on cornieules. Field and petrographic evidence has revealed that cornieules are formed from a starting material of gypsum and dolomite that had been fractured, veined and brecciated many times. The causes of fracturing were probably tectonic in the initial phases, and non-tectonic later. Due to the major post F
4
metamorphism, the gypsum was replaced by calcite and the calcite was subsequently dolomitized. Dolomitization was accompanied by a 12–13% increase in porosity. When the rocks were brought near to the earth’s surface, chemically active sulphate-rich percolating solutions invaded the rocks, brought about dedolomitization and formed the cavernous structure of cornieule.
The relationship between kink–bands and shear fractures in the experimental deformation of slate
Authors: ANDERSON T. BERNARD
Published: December 2007

Experiments in the cleavage-parallel compression of slate demonstrate important changes in the mode of deformation with increasing confining pressure. At pressures up to 3 kb shear fractures are dominant. In the range 3.5 to 7.24 kb the rock yields through the development of an intersecting network of narrow kink-bands. The transition is reflected in a marked change in the slope of the Mohr envelope at a confining pressure of 3 kb, indicating that different failure criteria are relevant to the two types of deformation, that also give stress-strain curves of different shape.

The geometrical relationship between shear fractures and kink-bands is described in detail. The shear fractures make a much smaller angle (mean value 30.7°) with the direction of maximum compression than do the kink-bands (mean value 55.4°).

At the highest confining pressures employed (about 7 kb), there is evidence of kink-band growth by lateral migration and separation of the bounding kink-planes. At all lower pressures the length of the rotating, kinked, segment of foliation is determined at inception.
A Bouguer Anomaly Map of southern Great Britain and the Irish Sea
Authors: MAROOF SABAH I.
Published: December 2007

A B
ouguer
anomaly map of the southern part of Great Britain and its filtered derivative are presented. Many negative Bouguer anomalies correlate with known sedimentary basins and granitic intrusions, but the granodiorites of the East Midlands are not associated with negative Bouguer anomalies.

The data used in the compilation were obtained from the following:

Bott
et al.
(1958

&
1971
) for the SW England, north Irish Sea;

Blundell
et al.
1971

for the south Irish Sea;
Griffiths and Gibb (1965)
for Wales; Institute of Geological Sciences for Northern Ireland, England; Dublin Institute for Advanced Studies for the Irish Republic; Cambridge University for the English Channel and E. E.
Cook (1965)
for the North Sea.

Each of the gravity maps obtained from the above sources was digitized by drawing square meshes. Except for a map of a small area of the North Sea, which was digitized at 16 km intervals, the gravity maps were digitized at 8 km intervals, values being interpolated by eye at sampling points. The digitized data were then used to compile a Bouguer anomaly map with a contour interval of 5 mgal. Although the various source maps used were of differing quality, surveying errors have no significant effect on the compiled map at the scale and contour interval presented.

The compiled Bouguer map (Fig. 1) contains anomalies from 16 km in wavelength. The negative anomalies are outstanding, and they correlate well with the large sedimentary basins, such as the Irish Sea basin, North Sea basin, etc. Kent
Editorial
Authors: Leake Bernard E.
Published: December 2007

T
his issue
completes the two year spell of the present Scientific Editor. During this period the backlog of papers awaiting publication, which Dr W. W. Bishop had so magnificently reduced, was finally completely cleared, the period between submission and publication was reduced to 6–7 months for short papers and about 8–10 months for long papers, the average size of papers published was markedly reduced and dispatch was got onto a prompter basis.

At the same time, by utmost stringency in editing and with the invaluable technical advice of our publishers, the financial position of the
Journal
was steadily improved at a time of quite unprecedented rises in printing, postage and paper costs so that the difference between income and outgoings in publishing the
Journal,
a difference the Society has to meet, fell from £7,807 in 1971 to £6,980 in 1972 to £5,313 in 1973. Hopefully, with more realistic pricing and with a increasing print run, this trend will continue. One major source of saving was the reduction in the number of art plates and folders which totalled 33 in 1971, 40 in 1972, 27 in 1973 and only 12 in 1974. Appreciable cuts were made in the size of the proceedings and an increase in the volume of detailed material deposited for reference rather than published.

The speedier publication, which for instance is demonstrated by the present issue which completes the publication of all accepted papers that were first submitted in December 1973 (all earlier accepted papers having
Submarine geology, sediment distribution and Quaternary history of Start Bay, Devon
Authors: HAILS JOHN R.
Published: December 2007

An inter-disciplinary study has been undertaken in Start Bay, Devon. Geophysical data show that infilled channels dissect the bedrock surface of the Bay shoreward of a buried cliffline. Beyond this feature the surface resembles an abrasion platform. The three lithological units within superficial material are referred to as
barrier, bay
and
bank
deposits, Foraminiferal and sedimentological evidence, together with C-14 dates, indicate that a barrier-lagoon complex has migrated to its present position in response to oscillations of sea level during the latter stages of the Flandrian transgression. Analysis of vibrocore and other samples shows that wave and current processes are variously dominant in the upper 2 m of the superficial deposits. The relative stability of the Skerries Bank may be explained by the values of the residual currents which approach zero along its crest. Water particle velocities nearshore off Slapton Beach suggest that short period edge waves are responsible for shoreline cusps observed in the Bay. While experiments with tracer material indicate that longshore movement may variously depend on linear dimension, ratio or shape index, no clear relationship has been established with nearshore wave parameters. Evidence suggests that Start Bay is a
closed system
under present-day conditions, there being no nourishment of the foreshore from outside the area. The 1917 Hallsands disaster can be attributed to the legacy of dredging shingle from the intertidal zone between 1897 and 1902, combined with a critical combination of storm waves, gales and spring tides.
Submarine geology of Start Bay determined by continuous seismic profiling and core sampling
Authors: KELLAND N. C.
Published: December 2007

The major geological features identified include a buried cliffline, buried channels and relict barriers. Three major lithological units have been recognized within the superficial deposits overlying bedrock. The various features and deposits are discussed in this paper in association with maps, seismic sections and interpreted geological profiles which show the morphology of the bedrock surface, the thickness of the overlying superficial sediments and structures within them. The different lithological sequences present in the upper layers of the superficial deposits are illustrated in typical core sections.
Wave conditions in Start Bay
Authors: HOLMES P.
Published: December 2007

Wave refraction computations provide at least a qualitative description of the effects of near-shore sea-bed topography on wave conditions in the breaker zone. For Start Bay the presence of the Skerries Bank is important in that for waves travelling from the NE a considerable degree of focussing occurs. For other incident directions the wave energy is more equitably distributed along the coastline.

Inclusion of shoaling effects and, where justified, other shallow effects and, where justified, other shallow water wave phenomena provides a quantitative measure of wave conditions suitable for the prediction of sediment motion but considerable care needs to be taken in the interpretation solutions.
Small shelly fossils of late Precambrian and early Cambrian age: a review of recent work
Authors: MATTHEWS S. C. , MISSARZHEVSKY V. V.
Published: December 2007

Stratigraphic sections in the high Precambrianlow Cambrian of Siberia are described. They have yielded the variety of fossils—archaeocyathids, gastropods, hyolithids, hyolithelminthids, poriferids, tommotiids and others—that characterize the Tommotian, Atdabanian and Lenian Stages. Some shelly fossils are found high in the Precambrian (Yudomian). The Tommotian Stage is regarded here as the lowest Cambrian unit. Trilobites first appear at the base of the Atdabanian Stage.

A selection of fossils is illustrated and briefly described. Faunas from equivalent levels in Sweden (Tommotian Stage) and England (Nuneaton: Tommotian Stage; Comley: Atdabanian Stage) are cited. Comments are offered on ranges and on distribution (it is already apparent that certain Atdabanian Stage fossils are not restricted to the “provinces” identified for trilobites). The problems of recognizing primary shell-structure, the existence of symmetry-pairings, the manner of coiling of shells and the occurrence of perforations of shells (some seemingly due to boring by predators) are also discussed.
The Fleur de Lys Supergroup: stratigraphic comparison of Moine and Dalradian equivalents in Newfoundland with the British Caledonides
Authors: KENNEDY MICHAEL J.
Published: December 2007

Whereas the NW. Fleur de Lys Supergroup shows many general similarities with the Moine and Dalradian, the SE. Fleur de Lys is dominantly volcanic and has no extensive analogues in the British Caledonides. Equivalents of these rocks may be largely covered by younger sequences on the E. side of the Atlantic.
Basins and swells and the evolution of an epeiric sea
Authors: SELLWOOD B. W. , JENKYNS H. G.
Published: December 2007

During Pliensbachian–Bajocian times northern Europe, including Britain, was covered by an epeiric sea. Sediments formed include clays, sandstones, limestones and ironstones, usually cyclically arranged; different facies were developed synchronously in different areas. There is very little evidence, by way of slumps or turbidites, that redeposition processes were active. The sequence clay, sandstone, limestone/ ironstone is here interpreted as representative of a shallowing. Thus, at any one time, despite differing bathymetric zones, bottom slopes were apparently subdued enough to ensure that sediment displacement did not generally take place.

To reconcile the concept of Jurassic ‘basins’ and ‘swells’ with the subdued bottom slopes of the north European epeiric sea, we suggest that these structural elements were characterized by great and negligible subsidence respectively, but that sedimentation was always rapid enough to maintain a roughly level sea floor. We relate the Mendip, London Platform and Dorset coast ‘swells’ to early Jurassic positive fault motions in the basement. The Market Weighton ‘swell’ is ascribed to relative buoyant rise of a salt pillow or granitic body whose movement was probably triggered by the same motions. These, presumably extensional, tectonics were probably the driving force behind the formation of the whole north European epeiric sea and must be related, in turn, to the opening of the oceanic central Atlantic and Alpine–Mediterranean Tethys.
Mount Olympos, Greece: new light on an old window
Authors: BARTON CLIVE M.
Published: December 2007

Determination of the tectonic vector of a thrust sheet is possible by analysis of the structures associated with emplacement. The orientation of linear structures, asymmetric folds, trust surfaces and high-angle reverse faults indicates the movement direction of an allochthonous sheet. This information may be important in areas where no stratigraphical evidence of transport direction is available, such as Mt. Olympos in N.E. Greece, where an allochthonous metamorphic sheet rests on Mesozoic platform carbonates. The basis of current palinspastic interpretations is that the metamorphic sheet moved across the platform from thrust the N.E. in the Tertiary. Emplacement structures, however, indicate transport in the opposite direction. This was probably as a result of the final closing of a small ocean basin which lay west of Olympos during the Mesozoic. A re-interpretation of the Tertiary structure of the Hellenides is necessary.
Implications of new palaeomagnetic results from the Carboniferous System of Britain
Authors: TURNER P. , TARLING D. H.
Published: December 2007

The Carboniferous Limestone of the Craven Basin (northern England) gives a mean pole position of 40°N, 147°E which confirms the palaeolatitude of Britian relative to other continents at this time. A polarity scale has been constructed for the lower Carboniferous using the Avonian zonal scheme as a basis. The geomagnetic field was mostly reversed in lower Carboniferous times although brief periods normal polarity were not uncommon, particularly in mid-Viséan times.

The evidence for a world-wide polar transition during the Carboniferous has been assessed and found to rest critically on the original evidence from Australia and Africa. The newer European and North American data are best explained in terms of a slow average motion of these two continents relative to the palaeomagnetic pole. They are shown to be mainly in low latitudes but to be rotating slowly clockwise with their southern edges in essentially equatorial locations for most of the Carboniferous.
Strain and deformation rates at the Arabia/Iran plate boundary
Authors: TCHALENKO J. S.
Published: December 2007

The strain-rate along this colliding plate boundary is estimated at 0.5 × 10
−14
s
−1
. This compares well with Price's rates, but not with seismic moment calculations which suggest creep may be occurring. No field evidence of such creep can be found, indicating that the significance of such rates remains elusive.
Ultramafic rocks in Angleseytheir non-tectonic emplacement
Authors: MALTMAN ALEX J.
Published: December 2007

The ophiolitic suite of Monian rocks in Anglesey has been regarded as segments of oceanic crust or upper mantle and sediments that were tectonically emplaced by cold shearing or thrusting during plate subduction. These processes are inconsistent with the field evidence. Deformation related to emplacement is not found in either the igneous materials or the country rocks. Igneous textures and the relatively weak meshtexture serpentine occur at the margins of the serpentinite bodies. An aureole of epidote hornfels is commonly developed in the adjacent country rocks. Both the regional tectonic style and the local structures are inconsistent with major low-angle thrusting. If the ophiolitic rocks are related to oceanic plate consumption, the ultramafic and mafic materials must have ascended as magmas, perhaps along deep vertical fractures formed at the inflexion point of the subducting plate.
A palaeomagnetic study of part of the Lewisian complex, north-west Scotland
Authors: BECKMANN GEORGE E. J.
Published: December 2007

Directions of magnetization have been measured in dykes and gneisses of the Central Zone of the mainland Lewisian and in the Laxford granite sheets. Nine Scourie dykes from an area around Lochinver have yielded closely grouped directions of magnetization giving a mean palaeomagnetic pole at 37.3°N, 274.8°E (dp = 6.9°, dm = 9.6°). The direction for a Scourian granulite falls very close to the mean for the dykes,

A regional difference in magnetic stability has been discovered and this, together with evidence concerning variations in the opaque minerals, has formed the basis of an interpretation in terms of metamorphic history. Stable magnetization was probably imposed in the late Laxfordian metamorphism at about 1800 Ma. Upon closure of the Atlantic Ocean there is good agreement with North American apparent polar wander paths.
Petrochemistry and tectonic significance of Dalradian metabasaltic rocks of the SW. Scottish Highlands
Authors: GRAHAM COLIN M.
Published: December 2007

About 5 km of probable lower Cambrian metamorphosed doleritic and gabbroic sills and overlying submarine volcanics occur in the Dalradian Series of the SW. Scottish Highlands.

An altered, soda-rich group of spilitic affinity, often accompanied by epidotic segregations, is readily distinguished from unaltered basaltic compositions using chemical and modal criteria.

The metabasite suite, of strongly tholeiitic affinities, has a complex differentiation history; evolution towards extreme enrichment in Fe, Ti and P, and depletion in Ni and Cr, is achieved in part by fractionation at greater depth, and partly by differentiation within the thicker sills. Excepting rare quartz kerato-phyres, salic and felsic differentiates are lacking. Consideration of the behaviour of Ti, P, Zr and Y indicates a transitional nature between continental and oceanic tholeiites, and also derivation of the lowest lavas by tapping of the upper portions of underlying differentiating ferrogabbro sills.

Development of this thick sill-flow complex, possibly correlative with the broadly contemporaneous tholeiitic flood basalts and dyke swarms of NW. Newfoundland and Labrador, may reflect continental distension and incipient opening of a Proto-Atlantic ocean in lower Cambrian times.
Large-scale slumping in a flysch basin, southwestern Pyrenees
Authors: RUPKE N. A.
Published: December 2007

Sheets of deformed beds in the Eocene flysch of the southwestern Pyrenees are exposed along strike for over 16 km. The thickness of these sheets in places exceeds 100 m, and their volume is
c.
10 km
3
. The sheets formed by gravity induced slumping, triggered most likely by earthquakes. The velocities of slump transport may have been as high as those of turbidity flow. Directions of slumping are consistent indicators of regional palaeoslopes. The slump sheets do not reflect a particular environment of deposition, but more likely record the seismic regime (periodic earthquakes of great magnitude) of the flysch basin.
The structure of the Dalradian rocks in the North Ballachulish district of Scotland
Authors: ROBERTS JOHN L.
Published: December 2007

The present study, based on the detailed mapping of minor structures, confirms the original interpretation of
Bailey (1910
, 1934)
concerning the Dalradian rocks of the Ballachulish district. The rocks are only affected by two deformation phases of any importance. These are correlated with the D1 and D3 phases in the regional deformation history established by
Treagus (1974)
. The structures formed in response to these phases correspond to the primary and secondary structures of
Bailey (1910)
, respectively. The D1 structures comprise the Fort William Slide, the Appin Syncline, the Tom Meadhoin Anticline, the Ballachulish Slide and the Ballachulish Syncline, arranged in order of structural succession. The slides are lags associated with zones of intense D1 deformation. The Stob Ban Synform is a D3 fold which separates downward-facing D1 structures to the SE from upward-facing D1 structures to the NW.
Ultrabasic rocks of Rhum and Skye: the nature of the parent magma
Authors: GIBB FERGUS G. F.
Published: December 2007

Rocks from the peridotite dykes of southern Skye (
Gibb 1968
) are virtually identical to those found in the large layered intrusions of Rhum and Skye, suggesting that they may have been formed in a similar manner. The rocks of the layered intrusions are generally regarded as having formed by the gravitative accumulation of the early precipitating phases from a basaltic magma, usually with subsequent extensive ad-cumulus growth. Such a mechanism is totally inapplicable to the dykes and it can be established that they were formed by flow differentiation of a suspension of olivine in an eucritic liquid which subsequently underwent near-equilibrium crystallization. The possibility therefore arises that the layered intrusions originated from an ultrabasic magma similar to that which formed the dykes. Consideration of this possibility suggests that the petrogenetic models proposed for the layered ultrabasic intrusions of Rhum and Sgurr Dubh (Skye) (
Brown 1956
,
Wadsworth 1961
,
Weedon 1965
, Wager & Brown 1968) be slightly modified: in particular, that the parental magma was not a basaltic liquid but rather a suspension of olivine in a eucritic liquid. Such a modification is consistent with the features of the layered intrusions and appears to overcome several problems posed by the basaltic liquid hypothesis.
K/Rb ratios and metasomatism in metabasites from a Precambrian amphibolite–granulite transition zone
Authors: FIELD DENNIS , CLOUGH PETER W. L.
Published: December 2007

Potassium and rubidium values are reported for a suite of 181 metabasites from the amphibolite–granulite transition zone in the Precambrian Bamble sector of south Norway. Both alkalis are more abundant, and the K/Rb ratios lower, in the rocks from the amphibolite facies. Rubidium has been strongly fractionated with respect to potassium.

The K/Rb ratios exhibit a regular and systematic variation and this defines a linear trend which is markedly different from established igneous fractionation trends. The chemical fractionation occurred as a result of the metamorphism, and the chemical changes are in keeping with the concept of a vertical chemical fractionation within the continental crust. Similar linear trends established in other high grade metamorphic terrains may have the same (metasomatic ?) origin.
Pre-Caledonian metamorphic complexes within the southern part of the East Greenland Caledonides
Authors: HIGGINS A. K.
Published: December 2007

Isotopic dating and recent regional mapping have led to reappraisal of conventional interpretations of the southern part of the East Greenland Caledonides. The metamorphic complexes of the Scoresby Sund region preserve evidence of Archaean and Proterozoic orogenic episodes, and high grade metasedimentary sequences thought to be late Pre-cambrian Caledonian geosynclinal rocks have yielded middle Proterozoic isotopic ages. The intensity of the Caledonian orogeny is much less than formerly imagined. The interpretations of the Scoresby Sund region are extended northwards into the classic areas of the central metamorphic complex where the widely accepted concept of a deep-seated Caledonian orogeny was developed. A similar development to that of the Scoresby Sund region seems probable, though statements should be treated with reservation until new field work and isotopic studies have been completed. Brief mention is made of parallel developments in the Cale-donian fold belts of northern Europe.
Stratigraphy, structure and metamorphism of Dalradian rocks of the Maumturk Mountains, Connemara, Ireland
Authors: BADLEY MICHAEL EDWARD
Published: December 2007

Appin (lower) and Argyll (middle) Dalradian metasediments and associated igneous rocks are described and a formal stratigraphy proposed. The deformation history has four main phases, D
1
to D
4
. Major "nappe" structures, formed during D
1
and D
2
, were refolded by two phases of approximately coaxial crossfolding developed during D
3
and D
4
. Two of the major F
4
cross-folds, the Connemara Antiform and Joyce's Synform, superficially dominate the structure of the area. The main penetrative fabric in the rocks, an axial planar schistosity, was developed during D
2
. The deformations were accompanied by metamorphism that reached its peak (in the Maumturks) between D
2
and D
3
(MP
2
). The rocks were metamorphosed in the amphibolite facies and show an increase in grade from north to south across the area. It is suggested that the prograde MP
2
metamorphism, with coeval growth of staurolite and sillimanite, was partly caused by heat emanating from the complex of basic, ultrabasic and migmatitic rocks located during MP
2
in the upper limb of the F
1
Lissoughter Anticline, structurally above the present day outcrop in the Maumturks and now occurring mainly in south Connemara.
Early Scourian structures in the Scourie-Laxford region and their bearing on the evolution of the Laxford Front
Authors: DAVIES F. BRYAN
Published: December 2007

Pre-Badcallian layered basic/ultrabasic metaigneous sheets have been used as marker horizons to determine the large scale structure of the region between Badcall and Loch Laxford. The principal structure in the vicinity of the Laxford Front is a large scale overturned synform, occupied by supracrustal rocks, which is older than or contemporaneous with the phase of granulite-facies metamorphism which ended
c.
2800 Ma ago. Late Scourian and Laxfordian structures modified the early Scourian structures but are shown to be less influential south of Loch Laxford than previously suggested. The structural evolution of the area is interpreted in terms of progressive dextral transcurrent displacement acting along the Laxford Front since at least the end of the granulite-facies metamorphism.
A Caledonian plate tectonic model
Authors: ADRIAN PHILLIPS W. E. , STILLMAN CHRISTOPHER J. , MURPHY THOMAS
Published: December 2007

A plate tectonic model for the Caledonides of the British Isles with three non-parallel lower Ordovician-lower Devonian subduction systems is presented. In the north-west, the Caledonian thrust front is interpreted as the site of multiple, slow ESE.-directed subduction (Sd1) of Lewisian-bearing continental foreland plate beneath continental crust containing an ensialic Dalradian basin. South of the continental crust of the Southern Uplands zone lay a ENE.–WSW.-trending plate boundary (Sd2) where Iapetus oceanic crust was subducted to the NNW. The convergence of subducted lithosphere beneath the Moine-Dalradian plate is linked to its prolonged history of diachronous deformation, metamorphism, intrusion and uplift. The oblique subduction on Sd1 and Sd2 caused collision below the Moine-Dalradian outcrop generating sinistral strike-slip faults with downthrown south-east sides, spreading north-east with time. Sinistral displacement on the Great Glen Fault system, and of the Connemara inlier is linked to this model. A third (Ordovician-Silurian) subduction system (Sd3) is defined to the north-west of a volcanic arc from the Lake District in England, through southern Ireland. Iapetus oceanic crust was subducted to the south-east here.

Evidence is presented for oblique collision between Sd2 and Sd3 from late Ordovician to early Devonian, followed by an unstable triple point migrating south-westwards across the British Isles region, and subsequent dextral strike-slip movement on the suture.

Triple-point migration to the south-west is measured using diachronous ending of volcanism and plutonism on Sd
2
and Sd
3
Opposed lower Devonian collision points now appear to be dextrally offset by about 900 km. Calculated closure rates on Sd
2
and Sd
3
give minimum Arenig widths for Iapetus of 600–800 km. About 1270 km of late Ordovician-Devonian dextral displacement on the Iapetus suture could have generated 570 km of foreland convergence in the East Green­land-Scandinavian Caledonides.
Stratigraphic consequences of palaeomagnetic studies of Pleistocene and Recent sediments
Authors: THOMPSON R.
Published: December 2007

Polarity reversals, excursions and secular variation of the geomagnetic field are examined as magnetostratigraphic tools in recent sediments. Polarity reversals and some excursions are recognizable worldwide, whereas secular variation occurs on a more local scale. The reliability of palaeomagnetic directions in recent sediments, as a record of the ancient geomagnetic field, varies widely. The necessity of acceptability criteria for using palaeomagnetic data in chronological studies is emphasized. Low temperature partial demagnetization of Recent sediments is described to illustrate its use, in conjunction with more conventional magnetic and geochemical techniques, in establishing the mode and duration of origin of the natural remanent magnetization.