bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre-Triassic Swallow-holes in the Haematite District of Furness, Lancs: a Glimpse of an Ancient Landscape
Authors: Smith Bernard
Published: May 2009

A Point of economic importance, as well as scientific interest, has been brought out by a study of the occurrences of hæmatite in the Furness district of Lancashire and the neighbouring shores of the River Duddon in the Millom district of Cumberland; namely, that the origin and distribution of the ore-bodies, known as “sops”, is due, in large measure, to the physiographical conditions that existed in this area in post-Carboniferous but pre-New Red times. Future explorations for these profitable ore-bodies may be guided by a true appreciation of the conditions of formation, which are discussed, in somewhat scattered form, in the recently published Geological Survey Memoir on the “Hæmatites of West Cumberland, Lancashire, and the Lake District”.
The Pygidium of the Trilobite
Authors: Raymond Percy E.
Published: May 2009

Although the process of development of the pygidium in the trilobite has been known since the time of Barrande, its significance does not appear to have been appreciated, and much of the modern speculation on the classification of trilobites is based upon the erroneous idea that those species whose form is most annelidan are most primitive. As a matter of fact, the study of both morphology and ontogeny shows that in this group the large pygidium is primitive and the small one specialized.
Man and the Ice Age
Authors: Sollas W. J.
Published: May 2009

The exact and exhaustive study of the Quaternary terraces of the Somme, which we owe to Commont, may well serve as a starting point in any consideration of this subject. In its results it is not without its surprises, for we should scarcely expect to find, as we do, that the gravels which form the earliest deposits on each of the three lower terraces all contain the remains of a “warm” fauna; the third or highest of these terraces affordingElephas meridionalis, the first and secondE. antiquusand its companion Hippopotamus. Associated with these faunas are flint implements of early types. Pre-Chelléan in the third terrace, typical Chelléan in the second, and Chelléan “evolué” in the first. No signs of a cold climate are to be discovered in any of these gravels until we reach that of the first terrace, where a newer gravel is to be seen invading the older and bringing with it Acheuléan implements and the mammoth.
The Superficial Deposits near Sunderland and the Quaternary Sequence in E. Durham
Authors: Coupland George , Woolacott David
Published: May 2009

In this paper it is proposed (1) to describe the superficial deposits along the coast between Sunderland and Ryhope, (2) to give a short account of the beds exposed in the recent excavations at the Sunderland Barracks, and (3) to attempt a correlation of the Glacial and Post-Glacial deposits of the East of Durham. It is felt by the authors that a true conception of the sequence of events during the Pleistocene and Recent periods will be eventually obtained by the examination of typical areas and by the working out of the succession and mode of origin of the deposits in such regions.
Pebbles of Quartzite near Piltdown, Sussex
Authors: Hawkins Herbert L.
Published: May 2009

In July of 1929 I visited the classic locality of Piltdown under the guidance of Sir A. Smith Woodward. After paying homage at the tomb of Eoanthropus we descended from the plateau to the low-level gravel terrace that flanks the flood-plain of the River Ouse. At a place known locally as Sharp's Bridge (marked on the accompanying map by a cross) there is a new but already extensive gravel pit. A spot-level on the map near the pit gives the approximate level of the top of the gravel terrace as 38 o.d.; the face of the pit is dug to a depth of from 8 to 10 feet below this level, and seems to reach down to about the level of saturation determined by the water of the river.
V.—On Secondary Species of Brachiopoda
Authors: Walker J. F.
Published: May 2009

I Have already described in this Magazine several new species of Brachiopoda from the Lower Greensand of Upware; since then I have obtained many more specimens, and much kind assistance from Mr. Davidson, and I now propose to give the result of the examination of the new forms in this paper; also to more fully describe a Rhynchonella from the Inferior Oolite of Lincolnshire, which have named Rhynchonella Crossii.
IV.—Archæastacus (Eryon) Willemœsii, a New Genus and Species of Eryonidæ
Authors: Bate C. Spence
Published: May 2009

The several species of Eryon, described by various authors, appear to be distinguishable as separate genera, which are as definable from one another as from the recent forms of Polycheles and Willemœsia; but the variability appears not to be greater than in those that are separated in time through geological æons, than in those that are contemporaneous in geographical space.
IV.—Note on the Posidonomya Becheri Beds of Budle (Northumberland), with Remarks on the Distribution of the Species
Authors: Lebour G. A.
Published: May 2009

Budle Bay, on the coast of Northumberland, between Holy Island and Bamburgh, is the estuary of the little river Waren. The rocks of the country belong to the Bernician Series or, in other words, to the alternating grits, limestones, shales, and coals which in northernmost England represent the Carboniferous Limestone Series. The northern shore of the Bay is a broad expanse of sand stretching as far as Fenham Flats and Holy Island, but the southern is rocky though not lofty. The Great Whin Sill (the well-known intrusive sheet of Basalt) is present here, and the late Mr. G. Tate of Alnwick has more than once described it as it occurs here, associated with the beds which form the subject of this note. In 1872 he wrote: “At Budle the basalt is nearly connected with an indurated, jointed, red shale (containing Posidonomya Becheri, etc.), which overlies a limestone; for the basalt is in the hill a little above the schist, and on the sea-shore to the east; so that the jointed and indurated condition of the schist is probably due to the action of the Basalt.”
IV.—On the Recent Discovery of the Wing of a Cockroach and two Scorpions in Rocks of Silurian Age
Authors: Goss Herbert
Published: May 2009

Up to December last the most ancient fossil insects known were the six fragments of Neuroptera, obtained by Mr. C. F. Hartt, from the Devonian rocks of New Brunswick, which were described by Mr. Scudder in Vol. V. of this Magazine. Although these six fossils were the oldest known insects, it seemed unlikely that they, or even the families or genera to which they belonged, were the most ancient representatives of their class. The first appearance of insects on the Earth was probably contemporaneous with that of land plants, and as remains of this division of the Vegetable Kingdom had been discovered in Silurian rocks, it seemed not unreasonable to assume that insects might have existed at an earlier period than the Devonian. The recent discovery of the wing of a cockroach in rocks of Silurian age at Jurques, Calvados, France, no longer leaves the question of the occurrence of insects at an earlier period than the Devonian a matter of speculation.
I.—On A Collection of Fossils From the Lower Greensand of Great Chart, in Kent
Authors: Gregory J. W.
Published: May 2009

The rarity and imperfect preservation of the fossils in the upper part of the Lower Greensand, in the south-east of England, has always added considerably to the difficulties in the study of that series. The Atherfield Clay and the Hythe Beds both have well-marked faunas, though fossils are often absent from the latter. The palæontological evidence is, however, much less satisfactory in the case of the two uppermost of the four divisions into which the Lower Greensand is usually divided. A fair number of fossils occurs in these at Folkestone, but further to the west the lithological nature of the beds changes, and fossils are found in but few localities.
IV.—An Interesting Contact-Rock, with Notes on Contact-Metamorphism
Authors: Hutchings W. Maynard
Published: May 2009

For a considerable time past I have been engaged, in collaboration with Mr. E. J. Garwood, in an investigation of the rocks in contact with the Whin Sill. The results of our joint work, geological, petrographical, and chemical, will be published in detail in due course. In the meantime there are some special observations, made on some of the rocks in question, which have more or less bearing on some of the points dealt with in a paper I contributed to the Geological Magazine last year (Geol. Mag. 1894, pp. 36 and 64).
Sedimentation in an intracratonic extensional basin: the Karoo of the Central Morondava Basin, Madagascar
Authors: Nichols G. J. , Daly M. C.
Published: May 2009

The late Carboniferous to Triassic Karoo Supergroup of Madagascar is a sequence of predominantly continental clastic sediments deposited during a long period of regional crustal extension. In the Morondava Basin of western Madagascar the lower two divisions of the Karoo sediments – the Sakoa and the Sakamena – are deposits of fluvial and lacustrine sedimentation systems supplied from the Precambrian metamorphic basement terrain to the east. East–west crustal extension produced a series of graben and half-graben structures after the Sakoa period which were reactivated after the Sakamena. The position and orientation of these half graben, which were marginal to a larger rift system to the west, were partly controlled by the steep NNE–SSW mylonitic fabric in the metamorphic basement. Palaeocurrents in the braided river deposits of the Sakoa and Lower Sakamena indicate flow to the southwest and west in both sequences. The rivers followed a regional palaeoslope to the southwest/west and were apparently not significantly influenced by the local structural trends which were oriented perpendicular to this slope. The absence of local structural control is attributed to extensive erosional events which followed each tectonic episode and preceded the onset of further sedimentation which took place on an essentially peneplained surface. The tectonic episodes brought about changes in base level which caused this part of the basin to fluctuate between erosion and deposition.
The Adola Fold and Thrust Belt, southern Ethiopia: a re-examination with implications for Pan-African evolution
Authors: “Beraki W. H. , Bonavia F. F. , Getachew T. , Schmerold R. , Tarekegn T.
Published: May 2009

The Adola Fold and Thrust Belt of Ethiopia is a late- Precambrian, north–south trending belt of volcanic-sedimentary and ophiolite–like units overlying ‘basement rocks’ (gneisses and granitic gneisses). Detailed structural analysis and data from microfabrics have documented two thrusting events (D1, D5) and three folding phases (F2, F3, F4). All deformations have affected both the rocks of the Adola Fold and Thrust Belt and the ‘older basement’. The structural history is recorded as follows: (1) formation of ductile shear zones (Dl); (2) progressive development of recumbent folds (F2); (3) a superimposed north-south trending, tight to isoclinal, upright penetrative folding phase (F3), which imparted the dominant structure of the region; (4) F3 was later gently affected, at right angles to F3, by the last folding event (F4). Metamorphic conditions during this deformational cycle reached highest greenschist to medium amphibolite facies conditions. Close to major thrust contacts imbrication produced metamorphic discontinuities. Marked retrograde metamorphism in narrow horizons indicates a continuation of minor movements along the major thrusts, postdating the metamorphic peak. Evidence of a second thrusting/faulting episode (D5) is only recorded at the mesoscale. This latter event was accompanied by very low to low grade metamorphic conditions. In accepting the previously reported age of 1030±40 Ma for the volcanic–sedimentary unit of the Adola Fold and Thrust Belt, and the interpretation of these units as an immature island arc, a possibly early Pan-African oceanic accretion is postulated.
Probable microbial origin of Ordovician (Arenig) phosphatic pebble coats (‘ Bolopora ’) from North Wales, U.K.
Authors: Niedermeyer R.-O. , Langbein R.
Published: May 2009

Results are presented of thin-section, SEM, X-ray and microprobe investigations on problematical phosphatic accretions (‘ Bolopora ’) from the St Tudwal's area of North Wales. The data supplement investigations made by H. J. Hofmann on the genesis of the accretions, and indicate a microbial (bacteriogenic) origin. The bacteriogenic pebble coats are of dahllite. Microbial relics suggest water–sediment interface-linked formation of the coatings under subtidal, and oxic to anoxic, environmental conditions during a sedimentary hiatus.
Palaeomagnetism of the Bayan Gol Formation, western Mongolia
Authors: Evans D. A. , Zhuravlev A. Yu. , Budney C. J. , Kirschvink J. L.
Published: May 2009

Oriented samples of the Lower Cambrian Bayan Gol Formation from Salaany Gol, Mongolia, were collected at roughly 5 m stratigraphic intervals for palaeomagnetic analysis. Progressive alternatingfield and thermal demagnetization isolated two magnetic components: a present-field overprint, typically removed by 10 mT fields and ~200°C heating; and a high-coercivity, high-unblocking-temperature (550–600 °C), predominantly single-polarity component that was imparted to the rocks prior to early or middle Palaeozoic deformation. Single-polarity magnetization at Salaany Gol contrasts with results from Lower Cambrian rocks on the Siberian platform, previously considered correlative with the Bayan Gol Formation, which show a prominent change in polarity bias near the top of the Tommotian Stage. Two hypotheses can explain this discrepancy. First, the entire Bayan Gol Formation may correlate with the predominantly reversely polarized, lower half of the Tommotian Stage in Siberia. This model is consistent with plausible interpretations of δ13C profiles for the Zavkhan basin and the Siberian platform. Alternatively, the characteristic magnetic direction from our samples may be a pre-fold overprint. If post-accretionary, then comparison with Siberian palaeomagnetic results suggest a Silurian–Devonian remagnetization age, and existing bioand chemostratigraphic correlations provide the most reliable spatial and temporal links between the Zavkhan basin and the Siberian platform. If the observed magnetic directions are primary or an immediate overprint then they may be used to constrain the early Cambrian palaeogeography of the Zavkhan basin and the Palaeo-Pacific Ocean. Mean inclination of 62 ±4° corresponds to a palaeolatitude of 44 ±5°, several thousand kilometres from the equatorial Siberian craton
Geology and geochronology of Inaccessible Island, South Atlantic
Authors: Chevallier L. , Rex D. C. , Verwoerd W. J.
Published: May 2009

Inaccessible Island is the eroded remnant of an extinct, comparatively small intraplate volcano dominated by flows of alkaline olivine basalt. The oldest stratigraphie unit is a hydrothermally altered basement of somewhat questionable early Pliocene (6.5 Ma) age. This is unconformably overlain by a volcanic superstructure built up during the last three million years. The two formations have different trace element signatures that may be attributed to different mantle sources. Boulders of gabbro are common but the presence of an in situ plutonic intrusion could not be confirmed. Their K-Ar age of 12.8 Ma may be spurious and their possible relationship with the volcano is uncertain. Reliable age determinations of 0.95–0.72 Ma were obtained on lava flows of the second volcanic stage, subdivided into four units or stratigraphie members. The latest unit consists of plugs, sills and flows of an evolved magma fraction (benmoreite and trachyte) of which benmoreite is considered to be the more voluminous. Several dyke swarms of different ages reveal the internal structure of the volcano. It is concluded that the main volcanic centre was located immediately offshore to the northwest and that the edifice was attached to an east–west volcanic rift zone. Apart from marine erosion, massive land-sliding probably took part in shaping the island and its submarine platform.
Global ocean—atmosphere change across the Precambrian—Cambrian transition
Authors: Brasier M. D.
Published: May 2009

The late Precambrian and Cambrian world experienced explosive evolution of the biosphere, including the development of biomineral skeletons, and notably of phosphate and siliceous skeletons in the initial stages of the adaptive radiation. Ongoing research indicates profound changes in climate and atmospheric carbon dioxide over this span of time. Glacial conditions of the Varangian epoch occur enigmatically at low latitudes, associated with carbonate rocks. Later changes in palaeogeography, sea level rise and salinity stratification encouraged prolonged ‘greenhouse’ conditions in both latest Precambrian and Cambrian times, with indications of relatively low primary production in the oceans. The Precambrian–Cambrian boundary interval punctuated this trend with evaporites, phosphogenic events and carbon isotope excursions; these suggest widespread eutrophication and conjectured removal of carbon dioxide from the atmosphere. Whatever the cause, nutrient–enriched conditions appear to have coincided with the development of phosphatic and siliceous skeletons among the earliest biomineralized invertebrates.
The Devonian System in Iran: a review
Authors: Dastanpour Mohammad
Published: May 2009

Upper Devonian strata are distributed widely throughout Iran. A review of all available literature on the Devonian, together with information from recent studies in the Kerman region, provides a basis for correlation and description of facies successions for the whole country. In most sections the local base of the Upper Devonian sits disconformably on older rocks, whilst the upper contact with the Carboniferous is almost everywhere transitional. There is everywhere an apparent hiatus spanning a probable early and mid Devonian interval. Lower and Middle Devonian fossils have not yet been discovered, but for the Upper Devonian there are abundant fossil data indicating the widespread occurrence of Frasnian and Famennian shallow marine deposits. A palaeogeographical map for the Upper Devonian of Iran is constructed.
Geophysical investigation of the Beinn an Dubhaich Granite, Skye
Authors: Goulty N. R. , Darton C. E. , Dent A. E. , Richardson K. R.
Published: May 2009

There has been a long-standing controversy concerning the form of the Beinn an Dubhaich Granite, which intrudes Cambro-Ordovician limestones and contains enclosures of limestone at outcrop. We have undertaken a three-part geophysical investigation with the aim of resolving some issues raised by previous workers. Our most significant finding results from the measurement of a gravity profile across Beinn an Dubhaich. It reveals a negative anomaly of more than 2 mGal over the granite outcrop. Our preferred model to fit this anomaly is a steep-sided granite stock extending down to about 1 km depth, which implies that the limestone enclosures are roof pendants. In a supplementary study, we measured magnetic profiles across dykes in some of the limestone enclosures in order to determine the depth to the contact with the underlying granite. However, in the most clear-cut cases we could only determine a minimum depth of 20 m, and were unable to constrain the maximum depth. In hindsight, we suggest that microgravity surveying would be a better method for determining the thicknesses of the limestone roof pendants. In the third part of the investigation, we measured a tight grid of magnetic profiles to the northeast of the granite outcrop to test a previous suggestion that dyke-like lobes of granite intrude pre-existing fractures in the overlying limestones. We located several large magnetic anomalies associated with outcropping doleritic dykes and concluded that these had not been correctly identified in the earlier work. Consequently, the ground magnetic profiles acquired to date provide no valid evidence to support the idea of an interfingering contact between the limestones and the underlying granite.
Age and significance of Upper Cretaceous siliciclastic turbidites in the central Pindos Mountains, Greece
Authors: Wagreich M. , Pavlopoulos A. , Faupl P. , Migiros G.
Published: May 2009

A significant 5- to 30-metre-thick interval of siliciclastic turbidites forming the First Flysch is present in the deep-water succession of the Pindos Zone. Nannofossil investigations in the central parts of the Pindos Mountains of mainland Greece indicate an assemblage of theMarthasterites furcatuszone (CC13). The presence ofM. furcatus, together with commonQuadrum gartnerisuggests that the turbidites were deposited mainly during the middle to upper part of the late Turonian. The siliciclastic turbidites are interpreted as deposits of a lowstand fan as a result of a pronounced short-time eustatic sea-level drop in the late Turonian.
Single zircon evaporation ages constraining the growth of the Archaean Aravalli craton, northwestern Indian shield
Authors: Roy A. B. , Kröner A.
Published: May 2009

Single grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan, northwestern Indian Shield. The protolith ages for two gneisses, collected from east of Udaipur, are ˜3230 Ma and 2887 Ma respectively. The granitoids display an intrusive relationship with the gneisses and yielded ages ranging between 2666 Ma and 2620 Ma. These ages provide the basis for a geochronological model of evolution of the oldest basement of the Aravalli craton.
The graptolite nema: problem to all our solutions
Authors: Rickards R. B.
Published: May 2009

Lack of understanding of the graptolite nema and virgula is probably the main cause of the general failure to arrive at a general mode of life theory for planktonic species. The nema and virgula are shown to be different structures. The nema may have had a rhabdosome rotational function at early growth stages; the primary function of the virgula may have been rhabdosomal rotation, whilst a secondary function was as a stipe growth guide. Rotational function would be inapplicable for pseudovirgulae and in synrhabdosomes.
Albitized microcline grains of post-depositional and probable detrital origins in Brøttum Formation sandstones (Upper Proterozoic), Sparagmite Region of southern Norway
Authors: Morad S.
Published: May 2009

Untwinned albite (Ab99.4An0.4Or0.2) grains, forming during diagenesis and very low-grade metamorphism, are common in sandstones of the Brøttum Formation (Upper Proterozoic) in the Sparagmite Region of southern Norway. These untwinned albite grains are usually clouded by vacuoles and tiny inclusions which are mostly made of carbonaceous material (although some albite grains also contain some combination of carbonates, quartz, phengite, chlorite, pyrite, halite and anatase). The presence of microcline grains replaced partly by albite indicates that the albite grains are pseudomorphs after microcline. Chessboard albite which occurs in the Brøttum Formation is suggested to be detrital in origin.
Determining the representative composition of a set of sandstone samples
Authors: Philip G. M. , Watson D. F.
Published: May 2009

The description of sandstone samples, defined by three components, is introduced through non-parametric sample density description. The composition of a particular sample defines a direction from the origin of the Cartesian reference frame. Radial difference between individual samples then provides the measure of their similarity. A sample set can be viewed as a bundle of compositional axes with a corresponding density distribution on both the ternary diagram (or unit constant sum plane) and the positive octant of the unit sphere. Because radial differences are disproportionately displayed on the ternary diagram, radial density calculations on the sphere are to be preferred. The mode of the sample set, the implied centre of greatest data concentration, is considered to be the most meaningful representative value, as the component joint mean can lie outside the data field with certain data configurations. In addition, the component joint mean cannot provide a useful representative composition for samples drawn from a bimodal distribution. Sample density distribution not only provides a data defined approach to describe sample dispersion, but also furnishes an indication of sample sufficiency in displaying the degree to which modes are supported by surrounding observations.
Structural evolution of a frontal ramp section of the West Spitsbergen, Tertiary fold and thrust belt, north of Isfjorden, Spitsbergen
Authors: Wennberg Ole Petter , Andresen Arild , Hansen Sigurd , Bergh Steffen G.
Published: May 2009

The geometry and kinematic evolution of a frontal ramp section associated with the Tertiary West Spitsbergen Orogenic Belt has been investigated in a small area (Lappdalen) north of Isfjorden. The previously recognized thrust front corresponds to a complex step or ramp in the position of the sole-thrust in the area. The sole-thrust is localized to the evaporites of the Permian Gipshuken Formation to the west of the footwall ramp, whereas to the east it continues as a bedding-parallel thrust in Triassic shales (Sassendalen Group). The area to the west of the footwall ramp is characterized by large scale thrusts and folds involving the Permian Gipshuken and Kapp Starostin formations and the lower part of the Triassic Sassendalen Group. East of the footwall ramp both Permian and Triassic strata are sub-horizontal and apparently undeformed. Three major thrust sheets are recognized. Based on the geometric relationship between folds and faults in the area, both fault-bend and fault-propogation mechanisms of folding are inferred. Restoration of the Kapp Starostin Formation to its pre-deformational state indicates a minimum of 35% shortening. Structural observations within the Sassendalen Group in the study area and on Dickson Land suggest that some of this shortening is transmitted eastwards along one or more bedding parallel thrusts in the Sassendalen Group.
Post-impact deposits in Tvären, a marine Middle Ordovician crater south of Stockholm, Sweden
Authors: Lindström M. , Flodén T. , Grahn Y. , Kathol B.
Published: May 2009

The well-preserved Tvären crater is noteworthy for being one of a small number of Early and Middle Ordovician impact structures formed in a marine environment. It is demonstrated to be an impact structure by the presence of a breccia lens, consisting of crystalline basement rocks, and shocked quartz. The breccia lens formed under dry-hot conditions after expulsion of sea-water by the impact. Resurging sea-water thereupon deposited a positively graded, 60 m thick turbidite-like unit. This graded resurge deposit is a previously unknown feature, to be expected in open-sea impacts. Breccia in the lower part of this graded deposit contains fragments of a remarkably complete orthoceratite limestone succession that existed at the site of impact, resting on non-lithified sand of probably Early to earliest Middle Cambrian age. A sedimentary succession was deposited inside the crater at depths decreasing from more than 200 m in the initial stages to some 100 m at the time of deposition of the youngest preserved beds. The environment within the crater thus favoured deposition of an essentially complete stratigraphic succession with depth-controlled palaeoecology for a significant time interval after the impact. Whereas planktonic members, like graptolites and chitinozoa, are present throughout the post-impact succession, and asaphids, almost as persistent, became established at an early date, burrowers were somewhat reluctant to enter and remopleuridids and small strophomenids came in at a late stage. We suggest as a result of this study that structures formed by impact may offer unique information about the palaeogeology and palaeoenvironment of the region hit by the impact.
Geochemistry of the Sunnfjord Melange: sediment mixing from different sources during obduction of the Solund–Stavfjord Ophiolite Complex, Norwegian Caledonides
Authors: Alsaker Einar , Furnes Harald
Published: May 2009

The Sunnfjord Melange is a strongly tectonized sedimentary assemblage occurring tectonostratigraphically below the Solund–Stavfjord Ophiolite Complex of Ashgill age, and upon continental margin deposits of Wenlock or older age. The Sunnfjord Melange, which probably started to form within an oceanic transform fault, developed further during obduction of the Solund–Stavfjord Ophiolite Complex. The Sunnfjord Melange is divided into two units, the lower Øyravatn Unit of predominantly fine grained calcareous quartz-bearing chlorite–muscovite schists, and the upper Markavatn Unit, mainly metagreywackes. Both units contain blocks of metabasalts, marble and meta-arkose. Serpentinite blocks are restricted to the Markavatn Unit. The appearance of serpentinite detritus is marked by much higher contents of Cr and Ni in the metasediments of the Markavatn Unit than in those of the Øyravatn Unit. The geochemistry of the metasediments from the Øyravatn Unit and the Markavatn Unit is compatible with mixing of detritus from continental and ophiolitic sources. Despite the strong and pervasive deformation of the Sunnfjord Melange, its geochemical composition from the lowest to the highest tectonostratigraphic levels reflects that of the inverse pseudostratigraphy of the Solund–Stavfjord Ophiolite Complex. Thus, only metabasalts of the Solund–Stavfjord Complex and continental meta-arkoses yielded detritus to the schists of the Øyravatn Unit. The compositions of the schists and metagreywackes of the Markavatn Unit, on the other hand, show that a multicomponent detritus derived from metabasalt and serpentinite of the Solund–Stavfjord Ophiolite Complex, mixed with the detritus from continental meta-arkoses.
Geology and geochemistry of the volcanic rocks of the Pioneer Formation, Bridge River area, southwestern British Columbia (Canada)
Authors: Dostal J. , Church B. N.
Published: May 2009

The Pioneer Formation of southwestern British Columbia (Canada) is composed predominantly of middle to late Triassic pillow basalts. These rocks are an integral part of the Cadwallader and the Bridge River terranes that were delaminated from the oceanic lithosphere and stacked against the continental margin of the North American craton by middle Jurassic time. The basalts are underlain and locally intercalated with ribbon cherts and argillites that range in age from Mississippian to Triassic. The Triassic basalts are conformably overlain by clastic sediments containing late Carnian–Norian conodont fauna. The tholeiitic basalts have enriched and depleted REE patterns, and have been emplaced in an oceanic environment. The compositional variations of the basalts are attributed to dynamic partial melting of source rocks that are believed to have been part of the rising mantle diapir. According to our model, after initial melting in the garnet stability field, the mantle diapir rose up to the spinel stability field where it underwent subsequent melting. The reconstructed stratigraphy of the Bridge River area may be interpreted in terms of an oceanic plate moving over a mantle plume and into a trench where offscraping preserved tectonic lenses of the subducting plate in an accretionary prism.
First record of the Devonian lycophyte Leclercqia from South America
Authors: Berry Christopher M.
Published: May 2009

A single leafy stem from the Middle or lowermost Upper Devonian Campo Chico Formation, Sierra de Perijá, western Venezuela, is the first record of the important Devonian herbaceous lycophyte Leclercqia from South America, usually considered as part of western Gondwana. The seemingly cosmopolitan distribution of this genus is discussed in relation to coeval assemblages and palaeo-continental reconstructions.
Nd isotope chemistry of Tertiary igneous rocks from Arran, Scotland: implications for magma evolution and crustal structure
Authors: Dickin A. P.
Published: May 2009

The geochemistry of Tertiary igneous rocks from Arran, western Scotland, provides a probe for the structure of the crust in the region of the Highland Boundary Fault (HBF). New Nd isotope data, coupled with other geochemical evidence, point to variable contamination of primitive mantle-derived magmas during magmatic differentiation in the crust. Two different isotopic contamination trends are seen. The northern granite was generated by contamination of basic differentiates by crust resembling exposed Dalradian units. Data for the central granite, and several other minor intrusions from south of the HBF, trend towards the reported isotopic signatures of granulite-facies xenoliths from the Midland Valley. However, quartz porphyry intrusions in the south of the island are compositionally similar to the nothern granite, and were probably intruded southwards across the HBF in dykes. Hence the isotopic signatures of the Tertiary intrusions reflect the different character of the crustal units on either side of the fault.
Compressional and extensional tectonics in low-medium pressure granulites from the Larsemann Hills, East Antarctica
Authors: Carson C. J. , Dirks P. G. H. M. , Hand M. , Sims J. P. , Wilson C. J. L.
Published: May 2009

Meta-sediments in the Larsemann Hills that preserve a coherent stratigraphy, form a cover sequence deposited upon basement of mafic–felsic granulite. Their outcrop pattern defines a 10 kilometre wide east–west trending synclinal trough structure in which basement–cover contacts differ in the north and the south, suggesting tectonic interleaving during a prograde, D1 thickening event. Subsequent conditions reached low-medium pressure granulite grade, and structures can be divided into two groups, D2 and D3, each defined by a unique lineation direction and shear sense. D2 structures which are associated with the dominant gneissic foliation in much of the Larsemann Hills, contain a moderately east-plunging lineation indicative of west-directed thrusting. D2 comprises a colinear fold sequence that evolved from early intrafolial folds to late upright folds. D3 structures are associated with a high-strain zone, to the south of the Larsemann Hills, where S3 is the dominant gneissic layering and folds sequences resemble D2 folding. Outside the D3 high-strain zone occurs a low-strain D3 window, preserving low-strain D3 structures (minor shear bands and upright folds) that partly re-orient D2 structures. All structures are truncated by a series of planar pegmatites and parallel D4 mylonite zones, recording extensional dextral displacements.

D2 assemblages include coexisting garnet–orthopyroxene pairs recording peak conditions of ∼ 7 kbar and ∼ 780°C. Subsequent retrograde decompression textures partly evolved during both D2 and D3 when conditions of ∼ 4–5 kbar and ∼ 750°C were attained. This is followed by D4 shear zones which formed around 3 kbar and ∼ 550°C.

It is tempting to combine D2–4 structures in one tectonic cycle involving prograde thrusting and thickening followed by retrograde extension and uplift. The available geochronological data, however, present a number of interpretations. For example, D2 was possibly associated with a clockwise P–T path at medium pressures around ∼ 1000 Ma, by correlation with similar structures developed in the Rauer Group, whilst D3 and D4 events occurred in response to extension and heating at low pressures at ∼ 550 Ma, associated with the emplacement of numerous granitoid bodies. Thus, decompression textures typical for the Larsemann Hills granulites maybe the combined effect of two separate events.
The Holocene lithostratigraphy of Fenland, eastern England: a review and suggestions for redefinition
Authors: Wheeler A. J. , Waller M. P.
Published: May 2009

The Fenland basin is filled with unconsolidated Holocene marine and freshwater deposits. Stratigraphic studies of the basin date back to 1877. This paper reviews the various lithostratigraphic schemes which have been proposed. Particular attention is paid to the presently accepted lithostratigraphy. Examples and a case study of a newly surveyed area are used to highlight its failings. Many of the difficulties experienced in Fenland are common to problems of lithostratigraphic classification in coastal lowland environments, as is demonstrated by reference to recent debate in the southeastern North Sea. In Fenland, as a result of the shortcomings of the various schemes, it is proposed that a new lithostratigraphy with formal stratotypes is devised. Suggestions are made as to the form this new stratigraphy could take. In the meantime, an informal lithostratigraphy should be adopted which has no regional or chronostratigraphic connotations.
The Variscan thermal history of west Clare, Ireland
Authors: Fitzgerald E. , Feely M. , Johnston J. D. , Clayton G. , Fitzgerald L. J. , Sevastopulo G. D.
Published: May 2009

Vitrinite reflectance data from Namurian rocks in west Clare suggest that high maturation levels, corresponding to palaeotemperatures of 340–370 °C, were attained prior to Variscan deformation. Fluid inclusions in syntectonic quartz veins homogenize between 330 °C and 50 °C with an accompanying decrease in salinity from 27 to 5 eq. wt % NaCl. Maximum fluid inclusion entrapment temperatures ranged from more than 300 °C to 250 °C during Variscan folding in County Clare. The observed maturation levels (c. 7.5% Rmax) far exceed values for simple burial maturation based on the estimated burial history and ‘normal’ geothermal gradients, and do not increase with depth in the Doonbeg No. 1 exploration well. Fluid advective heating is suggested as the most likely mechanism consistent with the Clare reflectance and thermometric data. Vein and shear zone dimensions preclude rapid vertical movements of hot fluids through the section, and extensive lateral fluid migration from sedimentary basins undergoing tectonically driven dewatering to the south or west is therefore proposed.
Palynology of the ‘Lower Old Red Sandstone’ at Glen Coe, Scotland
Authors: Wellman Charles H.
Published: May 2009

‘Lower Old Red Sandstone’ deposits preserved by cauldron subsidence at Glen Coe, Scotland have hitherto lacked secure biostratigraphical age constraint. A sporomorph assemblage recovered from basal sediments of these deposits permits age determination, despite being highly carbonized. The sporomorph assemblage is correlated with the micrornatus-newportensis Sporomorph Assemblage Biozone, indicating a late early-early late Lochkovian age (early Devonian). Sporomorph assemblages from basal sediments of the ‘Lower Old Red Sandstone’ sequence at nearby Lorne, a suggested correlative of the Glen Coe deposits, are older (latest Pridoli-earliest Lochkovian age). However, the new biostratigraphical data do not preclude the possibility that the Glen Coe and Lorne deposits are lithological correlatives and the basal sediments are diachronous.
Cambrian–Ordovician Boundary beds at Tônismägi, Tallinn, North Estonia
Authors: Kaljo D. , Heinsalu H. , Mens K. , Puura I. , Viira V.
Published: May 2009

The Cambrian–Ordovician Boundary beds at the Tônismägi section in Tallinn, North Estonia, are represented by siltstones and sandstones with interlayers of clay and kerogenous argillites. In this section, three conodont zones –Cordylodus proavus, C. intermediusandC. rotundatus-angulatus– were established. Graptolites of theRhabdinopora flabelliformegroup were found in the upper part of theC. proavusZone. This section demonstrates that in suitable facies, species ofRhabdinoporamay appear earlier than usually considered.
Litophragmatoceras incomptum gen. et sp.nov. (Cretaceous Ammonoidea), a cryptic micromorph from the Upper Cenomanian of Arizona
Authors: Kennedy W. J. , Cobban W. A.
Published: May 2009

Litophragmatoceras incomptum gen. et sp.nov. is a small dimorphic planulate ammonite from the Upper Cenomanian Metoicoceras mosbyense Zone of Arizona in which microconchs are adult at as little as 5 mm diameter and macroconchs at 23 mm diameter or less. The quinquelobate suture is very simple, with entire lobes and saddles. It is distinct from all contemporaneous ammonites and is referred, with no great certainty, to the otherwise exclusively Upper Albian and Lower Cenomanian Flickiinae Adkins, 1928.
A deep-marine ichnofaunal assemblage from Llandovery strata of the Welsh Basin, west Wales, UK
Authors: Orr Patrick J.
Published: May 2009

In the Welsh Basin, turbidites of Llandovery age at Cwmerfyn, near Goginan (Devil’s Bridge Formation) and Neuadd Fawr, near Lampeter, contain similar, diverse, ichnofaunal assemblages, despite strong sedimentological differences between the two localities. The sediments at Cwmerfyn are a series of very thin- to thin-bedded silt/mud couplets. The silt-grade lower half of each couplet is ripple-cross- and/or planar-laminated; the mud-grade upper part is massive. At Neuadd Fawr, the strata are thin- to medium-bedded, and composed of fine- to medium-grained sand; individual beds are parallel-laminated or display pronounced convolute lamination. At both localities, the ichnofaunal assemblage is dominated by endostratal pascichnia observed on intrastratal, bedding-parallel, planes of splitting. All the ichnofauna is post-depositional. Both assemblages are dominated by examples ofNereites cambrensisandmacleayii; examples ofNeonereites uniserialisandbiserialis, Protovirgularia dichotoma, Chondrites, Dictyodora scotica, Helminthoida crassa, two other ichnospecies ofNereitesand examples ofNereitesisp.,Palaeophycus tubularis, Macaronichnus segregatus, Planolites beverleyensisandmontanusand a ‘braided trace’ are also present. In contrast, the diverse ichnofaunal assemblage recorded from the Aberystwyth Grits Group by others is both pre-depositional and post-depositional in origin. The former include agrichnia (PaleodictyonandSquamodictyon) and cubichnia (AsteracitesandBergaueria), observed as secondary casts on the soles of turbidites. The differences in composition between this ichnofaunal assemblage and those at Cwmerfyn and Neuadd Fawr are interpreted to be a result of the degree of oxygenation of the sediment profile. In the Aberystwyth Grits, the producers of the agrichnia and cubichnia would have been able to tolerate reduced oxygen levels in the sediment profile, because they maintained a connection with an oxygenated water column. The post-depositional component of the Aberystwyth Grits assemblage is interpreted to represent opportunistic colonization of the sediment profile during short intervals of elevated oxygen conditions produced by episodic turbidite deposition. The producers of the endostratal pascichnia at Cwmerfyn and Neuadd Fawr did not maintain connections with the water column, implying the presence of oxygenated interstitial porewaters during their emplacement.
Diagenesis of ferriferous phases in the Northampton ironstone in the Cowthick quarry near Corby (England)
Authors: Gehring A. U.
Published: May 2009

Berthierine, siderite and pyrite are the major ferriferous phases in the Northampton ironstone (NIS). Mineralogical and chemical data suggest a formation of these phases in a diagenetic marine environment changing from post-oxic to sulphidic conditions. Berthierine was formed first when the Fe2+ activity in the diagenetic system increased. Later, this phase was partially replaced by siderite and/or pyrite. A second stage of the diagenetic development in the NIS with increasing CO2 partial pressure (PCO2 ) is documented by siderite. The isotopic composition (δ18O mean value: –1.7‰PDB; δ13C mean value: –8.6‰PDB) points to siderite precipitation from a marine porewater environment with a microbial CO2 source. The shift from post-oxic to sulphidic conditions is indicated by the occurrence of pyrite and can be considered as a final stage. The diagenetic processes in the marine environment and the formation of the ferriferous phases were stopped by the influx of brackish or fresh water when the Midland Shelf turned estuarine.
Perim Island, a volcanic remnant in the southern entrance to the Red Sea
Authors: Mallick D. I. J. , Gass I. G. , Cox K. G. , De Vries B. V. W. , Tindle A. G.
Published: May 2009

Perim Island is an eroded fragment of the southwest flank of a late Miocene (10.5 ± 1.0 Ma) volcano whose centre lay on the southwesternmost tip of Arabia. The volcano is the westernmost of the E–W line of six central vent volcanoes (the Aden Line) that extends 200 km along the south coast of Arabia from Perim to Aden. Major oxide and trace element abundances are given for 35 Perim specimens and these show that the volcano has within-plate trace element characteristics and consists of a petrographically and geochemically simple suite of alumina-poor olivine basalts, andesites, and transitional andesite–trachyandesites. Six specimens, however, are markedly enriched in Al2O3 and CaO, and contain abundant (20–30 mode %) highly calcic (An77–83) plagioclase phenocrysts. Geochemical modelling suggests that the main Perim volcanic sequence was produced by the fractional crystallization (o1 + cpx + Ti-mt + plag) of a silica saturated (SiO2 c. 45%) basic melt. The high A1, high Ca, magmas appear to be mixing products of plagioclase-enriched basic magmas with more evolved melts. Perim is the oldest volcano of the Aden line, which becomes increasingly younger and alkalic eastward. It is suggested that the volcanism is related to an eastwards-propagating rift produced before the most recent stage of sea-floor spreading in the Gulf of Aden (4.5 Ma–present).
Elastic flexure with compressive thrusting of the Green River Basin, Wyoming, U.S.A.
Authors: Jie Tang , Lerche Ian , Cogan Jeff
Published: May 2009

An inverse elastic flexural model with compressive thrusting is applied to the northern Green River Basin, Wyoming. A combination of six parameters in the model determines the deformational processes of basement due to sediment load and compressive thrusting: flexural rigidity, lateral stress, bending moment, initial load, dip angle of the basement, and length. The results suggest that the northern Green River Basin develops dominantly as an elastic flexural response to the deformation of basement due to compressive thrusting of the Wind River Mountains. From the unloaded basement configuration we estimate that by latest Cretaceous time the thrust fault activity of the Wind River Mountains led the basement to uplift about 7 km above the hinge point at the margin of the basin and to form a complex faulted mountain system. The maximum uplift rate is about 100 m/Ma at the Wind River Mountains. Also we predict the sedimentary pattern, and provenance of sediments of Tertiary units, from the unloaded basement geometry. Thus the inverse elastic flexural model can be used to assess the evolutionary processes involved in a basin under compressive thrusting.
Vendian strata in their type area
Authors: Yakobsan K. E.
Published: May 2009

In the Eastern European region Vendian strata are divisible into two complexes: the lower one, only locally developed, is composed of alternating tillites, volcanics, sandy–clay rocks and dolomites; and the upper one, of alternating sandstone, siltstone, and mudstone strata with medusoid fauna, resting transgressively on the lower complex and older rocks. The lower complex is associated with sheet glaciation; the upper one was formed in a post-glacial isostatic basin. The name ‘Vendian’ should be applied only to the upper complex; the lower one should be called ‘Waranger’.
Systematic status of Pseudohibolites Blüthgen, 1936 (Belemnitida, Coleoidea) from Kong Karls Land, Svalbard
Authors: Doyle Peter
Published: May 2009

The belemnite genus Pseudohibolites Blüthgen, 1936 was erected without designation of a type species and is invalid according to Article 13b of the International Code of Zoological Nomenclature. The species P. nathorsti Blüthgen and P. caroli Blüthgen are reinterpreted using topotypes from Kong Karls Land and are considered species of Hibolithes Montfort, 1808.