bluuebunny/crossref_metadata_2025 huggingface dataset:
Tremadoc faunas from the Carmarthen district, South Wales
Authors: Owens R. M. , Fortey R. A. , Cope J. C. W. , Rushton A. W. A. , Bassett M. G.
Published: May 2009

A diverse fauna of trilobites, graptolites, inarticulate brachiopods, sponges, and a worm is described from the Tremadoc rocks cropping out in the Llangynog district, SW of Carmarthen. It permits identification of theClonograptus tenellusZone and older Tremadoc strata; younger Tremadoc strata are apparently absent. The fauna shows closest affinities with the Shineton Shales of Shropshire, while some of the trilobites also indicate a close relationship with those from the Tremadoc of NW Argentina.
Calymene quadrata King, 1923 and allied species of trilobites from the Ashgill Series of North Wales
Authors: Price David
Published: May 2009

Calymene quadrata King is re-described. Two new species of similar age and provenance are erected and considered to be closely allied to quadrata; all three forms are thought to be best placed in genus Gravicalymene Shirley. G. pontilis sp.nov., the stratigraphically oldest form suggests derivation of the group from an ancestor such as G. deani Ingham. G. arcuata sp.nov. is the youngest form. Variation in the preglabellar area between the three forms argues for an expansion of the diagnosis of genus Gravicalymene; this would allow it to contain forms previously placed in genus Sthenarocalymene Siveter.
New Arctocephalitinae (Ammonoidea) from the Middle Jurassic of Kong Karls Land, Svalbard
Authors: Rawson P. F.
Published: May 2009

Costacadoceras bluethgeni gen. et sp.nov. and Articoceras harlandi sp.nov. are described from the base of the Kongsøya Formation of Kong Karls Land, Svalbard, and dated as mid boreal Bathonian (early ishmae Zone).
Fission-track dating of British Ordovician and Silurian stratotypes
Authors: Ross R. J. , Naeser C. W. , Izett G. A. , Obradovich J. D. , Bassett M. G. , Hughes C. P. , Cocks L. R. M. , Dean W. T. , Ingham J. K. , Jenkins C. J. , Rickards R. B. , Sheldon P. R. , Toghill P. , Whittington H. B. , Zalasiewicz J.
Published: May 2009

Fission-track dating of zircons and apatites from tuffs and bentonites has produced the first isotopic ages for the type sections of the Ordovician and Silurian Systems. In the Ordovician the following ages have been determined: lower Arenig 493 Ma, lower Llanvirn 487 Ma, lower Llandeilo 477 Ma, upper Caradoc 463 Ma and upper Ashgill 434 Ma. In the Silurian, the following: lower Llandovery 437 Ma, lower Wenlock 422 Ma, upper Wenlock 414 Ma and Ludlow 407 Ma. The Ordovician-Silurian boundary is interpreted as occurring at about 436 Ma. Three North American Rocklandian bentonites yielded zircons whose ages average 453 Ma. This is about 10 Ma younger than supposedly correlative units in the British type sections.
Rift and thrust tectonics associated with a translational block slide, Abbotsford, New Zealand
Authors: Bishop D. G. , Norris R. J.
Published: May 2009

The East Abbotsford translational block landslide failed suddenly on 8 August, 1979, after months and probably years of slowly accelerating movement. A displacement of about 50 m occurred on a bedding plane dipping 7°, about 30 m below ground surface, at or very near the contact between two formations.

The complex graben formed around the head of the landslide is a small scale example of extensional (rift) tectonics. A wedge and prism model is developed to fit the geometry, and meet the constraints of preserving the cross-sectional area and stratal length of the beds involved and also to account for the sequential retrogressive failures of the trailing edge of the sliding block.

Reconstruction of the failure sequence at the toe shows the compressional zone to be dominated by overthrusting on upward sloping surfaces or ramps, with subsidiary backthrusting and buckling.

The energy expended in overthrusting, coupled with the decrease in mass (and hence driving force) resulting from the retrogressive spalling of the trailing edge of the slide block, indicates that the phase of rapid movement was accompanied by a sudden decrease in resistance on the failure surface for a movement of 50 m to have occurred.

Both the rift and thrust structures associated with the landslide have large scale tectonic analogues.
Gas filter-pressing origin for segregation vesicles in dykes
Authors: Sanders I. S.
Published: May 2009

Segregation vesicles have been recognized in two plagiophyric dolerite dykes in northwestern Ireland. The vesicles are each outlined by a rim of tangentially arranged plagioclase, and filled to a variable extent by a fine-grained, crescent-shaped lining of fractionated residual melt. They closely resemble segregation vesicles reported from Atlantic ocean-floor basalts.

It is suggested (1) that the vesicles began as CO2-rich bubbles released during decompression; (2) that these bubbles grew very little during crystallization, while H2O became concentrated in the residual melt; and (3) that exsolution and expansion of H2O-rich vapour forced interstitial residual melt through the rigid but permeable framework of crystals and into the existing CO2-rich bubble cavities.
K—Ar ages of alkaline igneous rocks in the northern Oman mountains, NE Arabia, and their relations to rifting, passive margin development and destruction of the Oman Tethys
Authors: Lippard S. J. , Rex D. C.
Published: May 2009

K–Ar ages of biotites from a variety of alkaline volcanics and minor intrusive rocks in the nothern Oman mountains allochthon give a range of ages from Triassic (230 Ma) to mid Cretaceous (92 Ma) and represent igneous activity on the Oman continental margin throughout the Mesozoic. This was a passive margin destroyed by the emplacement across it of a pile of nappes in the late Cretaceous, including a largely intact thrust sheet of Upper Cretaceous oceanic lithosphere (the Semail ophiolite). Biotite ankaramite dykes, cutting compositionally similar volcanics, in the thrust complex immediately beneath the ophiolite, give Triassic ages and are related to the rifting and break-up of the northeast Arabian margin at the beginning of formation of the Oman Tethys. Mid Cretaceous (Cenomanian–Turonian) ages are mostly recorded from the northern part of the mountains where there are alkaline tuffs in a sedimentary melange. They are approximately the same age as the ophiolite and may be related to tectonic instability of the Oman margin immediately prior to ophiolite emplacement. Alkaline sills, intrusive into a variety of rocks, including Triassic volcanics, give Jurassic and Cretaceous ages and are interpreted as periodic alkaline activity on the Oman margin throughout passive margin development.
An analysis of the molluscs from an Ipswichian interglacial river channel deposit at Maxey, Cambridgeshire, England
Authors: French C. A. I.
Published: May 2009

A freshwater and land molluscan assemblage from an Ipswichian stream channel at Maxey, Cambridgeshire, is discussed. The presence of Belgrandia marginata and Vallonia enniensis suggests that summer temperatures may have been somewhat warmer in the Ipswichian period. The assemblage represents the silting processes under relatively quiet water conditions, possibly in a side channel or backwater of a meandering river system.
A mechanism forming silicic segregations from basaltic magma discovered in igneous rocks of Western Sicily
Authors: Lucido G.
Published: May 2009

Summary. Mechanisms forming silicic segregations from basaltic magmas are considered of primary importance when dealing with magmatic problems. However, the processes which give rise to silicic segregations from basaltic magmas are so far obscure. Fortunately, the discovery of spheroidal felsic masses in some basic rocks of Western Sicily throws light on this subject. To clarify the relationships between felsic and basic fractions particular attention has been paid to the interactions which occurred at their contact. Textural evidence indicates that the accretion mechanism of the Sicilian felsic segregations tends to obliterate the silicate liquid immiscibility effects and suggests that the formation of silicic segregations is a consequence of liquid unmixing phenomena.
A silica deposit of possible Tertiary age in the Carboniferous Limestone near Birr, County Offaly, Ireland
Authors: Beese A. P. , Brück P. M. , Feehan J. , Murphy T.
Published: May 2009

Summary. Stony clays, comprising weathered bryzoan-rich chert and silica clay, are found adjacent to Carboniferous Limestone on the west and a weathered dolomitized zone on the east near Birr, County Offaly, Ireland. A gravity survey together with a stratigraphy obtained from boreholes and other test borings suggests a depth of about 40 m and a surface width or diameter of approximately 60 m for the deposit. Indirect evidence points to a possible Tertiary age. The interpreted origin of the stony clays is by silification of Carboniferous Limestone and preservation by solution subsidence along a possible fault zone.
Outflow ignimbrite sheets from Late Carboniferous calderas, Currabubula Formation, New South Wales, Australia
Authors: McPhie J.
Published: May 2009

Regionally mappable, silicic, outflow ignimbrite sheets are interbedded with fluvial volcanogenic conglomerates and sandstones of the Late Carboniferous Currabubula Formation of north-eastern N.S.W. Four of the most widespread of these ignimbrites are described and defined as members. The oldest member is comprised of many thin, originally non-welded flow units. Interbedded accretionary lapilli horizons may indicate phreatomagmatic activity at vent during the eruption in addition to local rain-flushing of co-ignimbrite ash clouds. Of the three other members, two are multiple flow-unit sheets, 160–180 m in aggregate thickness. Substantial portions of these sheets were originally welded. The remaining member is a simple welded ignimbrite characterized by abundant spherulites and lithophysae. Irregular pre-eruption topography and contemporaneous erosion were responsible for thickness variations of the ignimbrite sheets. Some palaeovalleys, now delineated by the ignimbrites, persisted in spite of repeated pyroclastic influxes. Relic pumice, shards and crystal fragments are ubiquitous components of the sedimentary facies of the Currabubula Formation, and were probably derived from originally poorly consolidated pyroclastic deposits such as airfall ash layers and non-welded ignimbrites. No surface trace of the sources of these ignimbrites exists. However, internal facies, thickness variations and volumes of the ignimbrites indicate that they periodically emanated from a multiple-caldera terrain which was continuously active during the Late Carboniferous, and located several kilometres to the west of present exposures.
Two new Ordovician volcanic centres in the Shelve inlier, Powys, Wales
Authors: Lynas B. D. T.
Published: May 2009

Summary. As a direct result of new work in the Shelve Ordovician inlier, two new important extrusive andesitic members of a revised Stapeley Volcanic Formation, are described. These members were originally regarded as extrusive. However, they have for over half a century been considered intrusive and a brief literature review attempts to account for this anomaly. A palaeogeographic reconstruction suggests that the members represent the remains of two Llanvirn volcanic islands which, following subsidence, were overlapped and buried by later Llanvirn sedimentation. This reinterpretation considerably increases the volume of andesitic material known to have been erupted in Llanvirn times in this part of the Welsh borderland.
Mélange within subduction–accretion complex rocks of Fredriksen Island, South Orkney Islands
Authors: Storey B. C. , Meneilly A. W.
Published: May 2009

Summary. A m´lange on Fredriksen Island, South Orkney Islands, is part of a Mesozoic subduction- accretion complex which formed along the western, Pacific side of Gondwana. It consists of a chaotic arrangement of irregular sized blocks, up to 8 m across, of basic pillow lava, chert, felsite and epiclastic sandstone in a pervasively sheared cataclastic matrix. Inclusions are typically lozenge-shaped and are characteristic of a tectonic m´lange. As the m´lange incorporates both possible ocean floor material that was accreted on to the continental margin and inner slope basin sediments it probably formed beneath the trench-slope basin along a shear zone at a high level in the subduction complex.
The chronometric age of the Sinian–Cambrian boundary in the Yangtze Platform, China
Authors: Zichao Zhang , Guogan Ma , Huaqin Lee
Published: May 2009

The Cambrian and Precambrian sedimentary strata in the centre and west part of the Yangtze Platform are in continuous successions, in which the Tiantzushan Member and the Meisuchun Formation are exceedingly rich in shelly fossils. In Co-operation with the stratigraphic study in depth and in order to determine the isotopic age for the Precambrian–Cambrian boundary in the Yangtze Platform, a number of isotopic age determinations by different techniques have been made in the laboratories of the Yichang Institute of Geology and Mineral Resources and the Research School of Earth Sciences, Australian National University, mainly on the sequences in the Yangtze Gorges area together with those from some other areas in the Yangtze Platform. In this paper, the authors summarize all of these results and infer 610±10 Ma as an age for the Sinian–Cambrian Boundary in the Yangtze Platform if the ‘golden spike’ is considered to be placed at the bottom of the Meishucun Stage.
Box-fault systems and ramps: atypical associations of structures from the eastern shoulder of the Kenya Rift
Authors: Griffiths P. S.
Published: May 2009

Box-fault systems are striking arrangements of short faults that are associated with complex groups of elongate, tilted fault blocks (ramps). They occur within the faulted eastern shoulder of the Rift Valley, close to the equatorial bend in its alignment. This association of small-scale structures is shown to be integrated within the large-scale, asymmetrical structural pattern of the equatorial bend.
The pelvis of Archaeopteryx
Authors: Walker A. D.
Published: May 2009

Examination of the Eichstätt specimen of Archaeopteryx shows that the pubis agrees with those of the Berlin and London specimens in indicating a downward and backward inclination of some 135° relative to a line drawn through the lower extremities of the iliac blade. The greater part of the backward rotation of the bird pubis had thus taken place by the Kimmeridgian Stage (sensu anglico) of the Upper Jurassic. A definite pectineal process is present in Archaeopteryx, indicating the existence of a well-developed ambiens muscle. Some preliminary remarks are made about the skull of Archaeopteryx.
A palaeomagnetic analysis of Miocene fluvial sediments at Pertusa, near Huesca, Ebro Basin, Spain
Authors: Turner P. , Hirst J. P. P. , Friend P. F.
Published: May 2009

In the Miocene fluvial system of the Huesca area, in the Ebro Basin, northern Spain, rivers radiated outwards, to the south and west, from a small sector of the northern margin of the basin. The deposits of the system extend about 60 km radially from this sector and then pass into calcareous and gypsiferous deposits.

The magnetostratigraphy of two logged sections, 1 km apart, within this system consists of an upper zone of normal polarity and a lower zone of reversed polarity. The lithostratigraphy and magnetostratigraphy are parallel.

The sands and silts are dominated by angular quartz, intraformational clay lithograins and calcite lithograins. They are mainly pale yellow brown to dusky yellow, and magnetic tests indicate that the magnetization is carried dominantly by ferric oxyhydroxides (haematite and gôethite). The higher temperature Natural Remanent Magnetization is probably due to detrital haematite which would have been partially aligned during fluvial deposition. Post-depositional modification (PDRM) may have occurred during dewatering.

Haematite pseudomorphing pyrite framboids indicates that early reducing conditions were succeeded by a more oxidizing regime which produced secondary magnetizations associated with fine-grained haematite and goethite.

Complete polarity zones are not delineated, but the thicknesses present are not excessive compared with other continental Miocene deposits. The average palaeolatitude of 22° is lower than would be expected for the Miocene of northern Spain, probably due to incomplete averaging of secular variations and other sources of error including possible ‘inclination error’.
Upper Cambrian Archaeocyatha from Antarctica
Authors: Debrenne F. , Rozanov A. Yu. , Webers G. F.
Published: May 2009

Reconnaissance geological mapping (1962–75) followed by detailed geological investigations (1979–80) in the Ellsworth Mountains of west Antarctica have established the existence of extensive Middle and Late Cambrian strata. Forms tentatively referred to Archaeocyatha have been examined by F.D. and A.R., who concluded that, despite the commonly held opinion that the phylum became extinct at the boundary of the Lower and Middle Cambrian, the Ellsworth Mountains' forms represented Irregularian Archaeocyatha which survived in protected niches into the Late Cambrian. The age of the fauna containing the archaeocyaths is firmly dated by abundant trilobites including species of Homagnostus, Pseudagnostus, Kormagnostella, Erixanium and Onchopeltis.
Lower Palaeozoic convergent plate margin volcanism on Bømlo, southwest Norwegian Caledonides: geochemistry and petrogenesis
Authors: Furnes Harald , Brekke Harald , Nordås Jan , Hertogen Jan
Published: May 2009

Major and trace element analyses of a Lower Palaeozoic metavolcanic sequence of convergent plate type from Bømlo, southwest Norwegian Caledonides, are presented and discussed. This sequence ranges in age from the Upper Cambrian through the Lower Silurian. Petrogenetic models for the lavas in terms of partial melting and crystal fractionation are discussed. Two models are presented for the metabasalts in order to explain their different trace element abundances and ratios:

(1) REE modelling, assuming a mantle source with REE abundances twice chondritic, suggests progressively more varied sources with time. Thus the metabasalts from the oldest (Upper Cambrian–Lower Ordovician) Geitung Unit of primitive island arc type, and those of the mid-Ordovician Siggjo Complex of ‘Basin and Range’ type can be modelled in terms of high (around 25%) and moderate (around 5%) degrees of partial melting of spinel lherzolite, respectively. The metabasalts of the post-Ashgillian Vikafjord Group of typical continental flood basalts are compatible with moderate (c. 5–10%) degrees of partial melting of spinel- and garnet-lherzolite sources. The supposed Lower Silurian Langevåg Group of calc-alkaline ‘Andean’ type metabasalts, grading into alkaline to tholeiitic metabasalts of early marginal basin (youngest) character, require low (<5%) to moderate degrees of partial melting of amphibole-, garnet- and spinel-lherzolite sources, respectively.

(2) Source heterogeneity, produced by subduction zone-derived enrichment of LIL elements, and contemporaneous stabilization of minor phases which accommodate HFS elements. This process, combined with possible continental contamination, may possibly yield the trace element concentrations and ratios of the different metabasalts by partial melting of modally similar mantle sources.
Controlling factors in the evolution of the graptolites
Authors: Kirk N. H.
Published: May 2009

Recent ideas on evolution in the graptolites have been based upon an assumption either of passive flotation and passive feeding, or of active and co-ordinated ciliary feeding resulting in automobility. These ideas are compared and a possible evolutionary consequence of automobility is suggested.
A review of the tectonics of the northern Middle East region
Authors: Lovelock P. E. R.
Published: May 2009

The structure of the northern part of the Arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region. The Palmyra and Sinjar zones share a common history of development involving two stages of rifting, one in the Triassic–Jurassic and the other during late Cretaceous to early Tertiary times. Deformation of the Palmyra zone during the Mio-Pliocene is attributed to north–south compression on the eastern block of the Dead Sea transcurrent system which occurred after continental collision in the north in southeast Turkey. The asymmetry of the Palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow Triassic evaporites. An important NW-SE cross-plate shear zone has been identified, which can be traced for 600 km and which controls the course of the River Euphrates over long distances in Syria and Iraq. Transcurrent motion along this zone resulted in the formation of narrow grabens during the late Cretaceous which were compressed during the Mio-Pliocene. To a large extent, present day structures in the region result from compressional reactivation of old lineaments within the Arabian plate by the transcurrent motion of the Dead Sea fault zone and subsequent continental collision.
Devonian brachiopod biostratigraphy of China
Authors: Hong-Fei Hou
Published: May 2009

Two Devonian biogeographic provinces are recognised in China, based on brachiopod distribution. The Junggar-Xinan Province to the north shows a mixture of European and North American elements, but notably no stringocephalids are present. The South China Province, which is subdivided into three subprovinces possesses more elements of European type.
Hardgrounds in the Lower Leintwardine Beds (Silurian) of the Welsh Borderland
Authors: Cherns Lesley
Published: May 2009

The base of the Lower Leintwardine Beds (Silurian-Ludlow Series) in the shelf sequences of the Welsh Borderland is marked by a widespread development of shelly conglomeratic limestone beds. Borings into some intraclasts indicate that they were hardgrounds. The early lithification, sometimes in situ, of both sand-grade and mud-grade carbonates is demonstrated by the conglomerates. Some compound intraclasts (‘hiatus concretions’) indicate a complex history of deposition, scouring and lithification. Boring of clasts which have not been further eroded is inferred to have taken place locally. The borings are of the narrow, single entrance form referable to Trypanites. The distribution of the conglomerates relates closely to Leintwardinian palaeogeography. Repeated hardground formation in sequences of inner shelf areas reflects episodic deposition alternating with periods of omission and erosion. There is evidence throughout the shelf of a break in sedimentation with hardground formation at the end of Bringewoodian times. The nature of the conglomerates suggests that they formed in shallow water conditions; there is no lithological indication of sub-aerial exposure. The absence of the Aymestry Limestone in the SE shelf is more probably due to its non-deposition or lateral lithological change to muddier beds with a different faunal assemblage than to its subsequent removal by erosion.
Petrology and geochemistry of the alkaline intrusion, Jombo Hill, Kenya
Authors: Nyambok I. O.
Published: May 2009

The field occurrence and the known immiscibility between silicate and carbonate melts suggest the Jombo alkaline intrusion and Mrima carbonatite intrusion have come from the same magmatic source. However, only the ijolite series apparently originated from a magma body at Jombo hill intrusion, while the feldspathoidal syenite series appears to have resulted from metasomatic alteration of the country rock-sandstone. The K/Rb ratios seem to indicate a mantle origin for the ijolites and a crustal one for the feldspathoidal syenites. The feldspathoidal syenite series were presumably formed by alkali metasomatism, resulting from magmatic fluid infiltration through intergranular movement. It is suggested that the partitioning of K and Na components in the metasomatizing fluid and solid feldspar phases at different temperatures, was the cause of two rock types – albite nepheline syenite and orthoclase nepheline syenite.
Primary igneous load-cast deformation structures in the Fongen-Hyllingen layered basic intrusion, Trondheim Region, Norway
Authors: Thy P. , Wilson J. R.
Published: May 2009

Load-cast structures in the Caledonian, synorogenic, Fongen-Hyllingen layered basic complex closely resemble those deformations resulting from reverse density stratification in experimentally studied, water-saturated sediments. The mushroom-shaped structures are apparently restricted to a single horizon within an interlayered, metamorphosed, dunite–troctolite sequence. They generally have a symmetrical form, revealing a polygonal pattern in the plane of the layering. The density contrast between an olivine-rich crystal mush overlying a plagioclase-rich crystal mush, both very close to the igneous sediment–magma interface, is believed to have caused the deformation. Subsequent consolidation occurred by adcumulus growth.
Geochemical surveys for Sn, Nb, Cu and Au mineralization, Mueilha-Dungash area, Southeastern Desert, Egypt
Authors: Soliman M. M.
Published: May 2009

Geochemical stream sediments and bed-rock surveys were carried out on an area of about 400 km2 in the Muelha-Dungash area. Results indicated that Sn and Nb anomalies are concentrated near Gabal Mueilha and are related to the greisenized and albitized granites. Disseminated-type and vein-type gold mineralizations occur in propylitized granodiorites and quartz veins at Samut. Cu anomalies show wide distribution, with a large proportion confined to the central and southwestern parts of the district, where signs of hydrothermal alterations are clear. Most of the Cu, Sn and Nb anomalies coincide with ‘deep-seated tectonic zones’ having the direction of the Red Sea Rift System, which are characterized by anomalous radioactivity and intense metamorphism as well as metasomatism and mineralization caused by acidic intrusions. Under the arid conditions of the Southeastern Desert of Egypt, stream sediments and bed rock surveys proved to be suitable methods of prospecting.
The problem of the Precambrian—Cambrian boundary
Authors: Rozanov A. Yu. , Sokolov B. S.
Published: May 2009

In the last few years the problem of the lower boundary of the Cambrian has been dealt with in dozens of works which considered not only the history of the question but all the current material available. It is a subject discussed at many national and international symposia. Although great progress has been achieved in drawing together the points of view on the position of the boundary (compare the results of the symposia held in Paris in 1958 with that in 1974), the range of different opinions still remains wide, particularly with regard to the zonal scales (for example, in Siberia, from the base of the Nemakit–Daldyn horizon up to the base of the beds with Fallotaspis). First, therefore, we give consideration to those questions which often constitute a stumbling block. It seems necessary to make a reservation that some of the difficulties arising may undoubtedly be referred to as purely psychological.
A contribution to the nomenclature and classification of volcanic rocks
Authors: Middlemost E. A. K.
Published: May 2009

At present one is not able to devise a single, standard classification of igneous rocks that is acceptable to all petrologists. This is mainly because igneous petrology consists of an uneasy union between the descriptive science of petrography and the explanatory science of petrogenesis, and at present the latter discipline is unable to provide a coherent model, or series of models, that can account for the origin and evolution ofall igneous rocks. Some of the more significant concepts used in the classification of volcanic rocks are examined, and three separate, yet complementary, classifications are presented.
Taxonomy and distribution of chasmopine trilobites
Authors: McNamara K. J.
Published: May 2009

The Ordovician pterygometopid subfamily Chasmopinae is considered to include not only Chasmops McCoy, 1849, and Uralops Ancigin, 1970, but also a number of other genera which encompass species previously referred to Chasmops. These are: Toxochasmops McNamara, 1979; Scopelochasmops gen.nov.; Bolbochasmops gen.nov.; and Rollmops gen.nov. A close correlation is shown to exist between distribution of chasmopines and lithofacies, which indicates habitation in ashallow water environment. A westerly spread of chasmopine species at various times from eastern Baltoscandia is considered to correspond with a similar spread of the shallow water environment. This is shown by the periodic appearance of members of the subfamily in the Oslo region and Britain. Thereis a general reduction in number of chasmopine species and genera away fromthe eastern Baltic.
The Vendian System of Siberia and a standard stratigraphic scale
Authors: Khomentovsky V. V.
Published: May 2009

In Siberia Vendian is equated with a Yudoma Complex or Yudomian. Yudomian deposits of the Siberian Platform and adjacent geosynclines differ greatly in facies and thickness. According to the composition and structure of Yudomian deposits, four facies provinces may be recognized on the platform. Local stratigraphic charts for each province are presented and their correlation and possibility to subdivide the Vendian System in Siberia into three horizons or stages are substantiated. The upper stage (Nemakit–Daldyn), on the basis of palaeontological evidence, is in its turn subdivided into two zones: Anabarites trisulcatus and Purella antiqua.

The most important Early Baikalian rearrangement is proved to take place around 800±50 Ma. The pre-Vendian (Late Baikalian) movements, though less intensive, make the determination of the Yudomian lower boundary easier.

The specific character of Vendian biostratigraphy is discussed involving all groups of the organic remains, that causes the necessity of recognition, subdivision and correlation on the basis of the whole complex of data.

The boundary between the Vendian System and the Lower Cambrian Tommotian Stage (in type section) is proved to conform to the base of the Pestrozvet Formation, which divides the A. sunnaginicus and P. antiqua zones.
Stratigraphical characteristics and development of Vendian–Cambrian boundary beds on the East European Platform
Authors: Mens K. , Pirrus E.
Published: May 2009

The present paper serves as a review on the stratigraphy and lithological characteristics of the Cambrian–Vendian boundary beds in the northwestern part of the East European Platform. This transition interval is represented by clastic rocks accumulated in humid climatic conditions. According to the lithological and palaeontological data the corresponding (transition) interval comprises two regional series: the Valdai Regional Series and the Baltic one. They both are divided into two regional stages (from below to top): Redkino, Kotlin, Rovno and Lontova.

The Redkino–Kotlin and Kotlin–Rovno boundaries are characterized by distinct contacts reflecting various changes in the sedimentary environment whereas the boundary between the Rovno and Lontova regional stages drawn on the basis of the palaeontological data only falls within the interval of continuous sedimentation.

Proceeding from the study of the fossil distribution and their living conditions during late Vendian and early Cambrian on the East European Platform the lower boundary of the Cambrian is most likely situated at the base of the Baltic Series.
Palaeozoic studies in honour of Sir James Stubblefield
Authors: Stubblefield James
Published: May 2009

Sir James was born on 6 September 1901 at Cambridge where he attended the Perse School. He received his geological education at Chelsea Polytechnic and the Royal College of Science. In 1923 he was appointed demonstrator in geology at the Imperial College of Science and Technology, London University, where he stayed until 1928; for his last two years there he also served as Warden at the pioneer Imperial College hostel. While at Imperial College he studied the Shineton Shales of the Wrekin district of Shropshire under the guidance of W. W. Watts and in collaboration with his life-long friend O. M. B. Bulman, and was awarded a Ph.D. in 1925. This work in Shropshire provided the stimulus for his continuing contribution on the Cambrian system and its faunas, and on trilobites of all ages. During this period he also recorded his observations on Tertiary crabs from Zanzibar, a group he was to return to in later years. In 1928 he obtained one of the two posts offered by the Geological Survey, being appointed Geologist. He undertook field work in the Dorking district as a prelude to an intended posting to the Survey office at York, but the death of G. W. Lee, then palaeontologist in Edinburgh, determined that Stubblefield should remain at the headquarters of the Survey at Jermyn Street in London. Internal transfers of the palaeontological staff left no member available to determine the fossils then accumulating from the current survey of the Shrewsbury district, and Stubblefield was asked by the Director to undertake this task because of his knowledge of the Lower Palaeozoic faunas of Shropshire. This transfer became long-term and thus began his association with, and eventual leadership of, the Palaeontological Department of the Survey, and secured the continuation of his notable contributions to palaeontology. The Shrewsbury commitment led to visits to the area during which new faunal horizons were discovered in the local Cambrian and Ordovician, including the Nemagraptus gracilis fauna from the Breidden Hills; other finds included the then earliest British eurypterid subsequently described by L. Størmer as the type of a new genus under the name of Brachyopterus stubblefieldi.
Silicified Lichidae (Trilobita) from the Middle Ordovician of Virginia
Authors: Tripp R. P. , Evitt W. R.
Published: May 2009

The trilobite family Lichidae is represented in the Middle Ordovician of Virginia by silicified remains of species of Hemiarges and Amphilichas. One new subspecies, Hemiarges turneri Chatterton & Ludvigsen rasettii, is described. Development stages of both genera are illustrated. The bulla of H. turneri rasettii appears in the meraspis, whereas it is present in the protaspis of a Devonian species. The late metaprotaspis of Amphilichas has a small fixigenal spine, a feature shared with protaspides of the family Odontopleuridae.
Early Tournaisian rocks at Lilleshall, Shropshire
Authors: Mitchell M. , Reynolds M. J.
Published: May 2009

Reidentification of the macrofossils from the lowest Dinantian limestones of Lilleshall, northeast of Telford, indicates that these beds are older than previously reported and that they can be correlated with the early Tournaisian Hastarian Stage. The conodonts recovered confirm this age and are characteristic of the Siphonodella–Polygnathus inornatus Assemblage Biozone. This reassessment affects the Dinantian palaeogeography of the Midlands of England and the early Tournaisian coast-line in the Lilleshall area can be redrawn further to the north than it has usually been placed.
A new interpretation of Ordovician stratigraphy in the Bahçe area, northern Amanos Mountains, south central Turkey
Authors: Dean W. T. , Monod O.
Published: May 2009

Lower Ordovician rocks in the Bahçe–Fevzipaşa district of the northern Amanos Mountains, previously divided into three separate formations, are referred to the Seydisehir Formation. Shaly strata that crop out southeast of Bahçe and have been termed Kizlaç Formation, Ayran Series or Bahçe Formation, described variously as being of Ordovician or Silurian age, are referred to the lower shale member of the Bedinan Formation; their sparse fauna includes the trilobitesColpocoryphe, KloucekiaandNobiliasasphusand is of Caradoc age. A single locality containingKloucekia phillipsii(Barrande, 1846) is shown to be that recorded by Frech in 1916 and subsequently lost sight of.
The formation of the trace fossil Cruziana
Authors: Goldring R.
Published: May 2009

Sectioning Cruziana shows that an intrastratal mode of formation is common, as postulated by Seilacher. Beds with Cruziana are typically composite. Burrows were sometimes washed out and then recast by sand with primary structures. Formation as open surface furrows on an eroded and firmed mud, as postulated by others, is sedimentologically plausible in some instances but is unproven and seems biologically unlikely.
A new Oscillatoriaceae-like filamentous microfossil from the Sinian (late Precambrian) of western Hubei Province, China
Authors: Zhongying Zhang
Published: May 2009

One nearly complete specimen of the new Oscillatoriaceae-like filamentous microfossil Doushantuonema peatii gen. et sp. nov. is described from the Sinian (late Precambrian) of western Hubei Province, China. This constitutes the first reliable record of the Oscillatoriaceae-like filaments in the Precambrian rocks of China.
K–Ar dates on granitoids from Archipiélago Cabo de Hornos, southernmost Chile
Authors: Suárez M. , Puig A. , Hervé M.
Published: May 2009

New K–Ar mineral dates from calc-alkaline granitoids of the Archipiélago Cabo de Hornos, in the southernmost tip of South America, range from 97 to 117 Ma. This confirms that the early Cretaceous was a period of major plutonic activity in the region and expands previous radiometric information on the Patagonian Batholith concerning migration of intrusion foci with time.
An example of the automatic contouring of geoelectrical data
Authors: Worthington P. F.
Published: May 2009

Isopachytes of boulder clay in an area of Northwest Lancashire have been constructed from borehole-controlled geoelectrical data by separately using manual and automatic contouring techniques. At the sites of later drillings, the known boulder-clay thicknesses compare favourably with those indicated by both contour distributions, suggesting that the automatic techniques have a useful application in problems of this kind.
The Stokes Magnetic Anomaly
Authors: Wellman H. W.
Published: May 2009

The Stokes Anomaly is traced for over 3000 km, from 700 km S of New Caldedonia almost to the eastern edge of the Campbell Plateau. For most of its length the anomaly is a double feature with positive peaks from 30 km to 50 km apart. From outcrops on the western side of the Southland Syncline it is inferred that the northeastern peak is caused by Permian volcanics, and the south-western peak by the associated Permian intrusives. The anomaly is displaced dextrally by a total of 1000 km where it crosses the New Zealand land mass. About 500 km of the displacement is caused by displacement on the Alpine Fault Zone, and the remainder by distributed dextral shear and by displacement on other sub-parallel faults.
Non-cylindrical folds, linear structures in the X direction and mylonite developed during translation of the Caledonian Kalak Nappe Complex of Finnmark
Authors: Rhodes S. , Gayer R. A.
Published: May 2009

Structural evidence from the Kalak Nappe Complex suggests the operation of layer parallel shearing stresses during the translation of the nappes. A simple shear model invoking irregular areas of high cohesion within individual layer boundaries is used to explain the development of both intra-folial, cylindrical and non-cylindrical folds and a regular zone of syn-folding blasto-mylonite at the base of the nappe(s). Fold hinges that are initially developed parallel to the Y axis of the strain ellipsoid during layer parallel shearing may be rotated towards the X direction as a result of large strains concentrated at points of high cohesion within the layering boundaries.
Recovery of Ordovician conodonts by hydrochloric acid from phosphate nodules reworked into the Sulphur Springs Formation (Devonian) in Missouri, U.S.A.
Authors: Chauff K. M.
Published: May 2009

The Glen Park Member of the Sulphur Springs Formation (Devonian) in east-central Missouri contains abundant phosphate nodules. Dissolution of several nodules in hydrochloric acid yielded a diverse, well-preserved Ordovician fauna, containing diagnostic graptolites, ostracodes and conodonts, demonstrating that the Glen Park phosphate nodules are reworked from the Ordovician. Faunal similarities and the in situ occurrence of phosphorite in nearby exposures of the Mequoketa Shale (Ordovician ) strongly suggest hat phosphate nodules in the Glen Park were reworked from the Maquoketa.
Stratigraphic significance of calcareous microfossils from the Lower Carboniferous rocks of the Skipton area, Yorkshire
Authors: Fewtrell M. D. , Smith David G.
Published: May 2009

Assemblages of calcareous foraminifera and algae have been examined in thin sections of Dinantian limestones from the Skipton, Broughton, Hetton, Eshton, Swinden and Lothersdale anticlines in the Craven Lowlands. Provisional identifications are listed for each assemblage and a correlation of the rock successions is suggested. The assemblages range from late Tournaisian to late Viséan in age, in terms of the Belgian divisions, and from Courceyan to Asbian in terms of the new chronostratigraphic stages of George et al. (1976).
A note on stress relationships determined from Mohr diagrams
Authors: Tremlett C. R.
Published: May 2009

Simple expressions given in terms of Mohr diagram parameters may be used both to check the accuracy of Mohr diagram constructions and/or to replace particular constructions in stress analyses of brittle rock failure. Examples of expressions relating to two common types of composite failure envelope are given together with brief examples of their possible application.
Subtidal flat-pebble conglomerate from the Upper Devonian of Poland: a multiprovenant high-energy product
Authors: Kaźmierczak J. , Goldring R.
Published: May 2009

Calcirudites in the Upper Devonian (Frasnian) of Central Poland are often couplets with a laminated intrapelsparite upper part and a lower section of intraformational calcarenitic and micritic flat pebbles. The pebbles are associated with bioclasts derived from 3 offshore environments: I, a fully marine area (echinoderms, rugose and tabulate corals, brachiopods, trilobites and conodonts); II, phytogenic banks (globose stromatoporoid stromatolites and Renalcis); III, restricted lagoons (ramose stromatoporoids, calcispheres, ostracodes and peloids). Many of the flat pebbles are only slightly displaced and had been partially cemented before being reworked. The depositional environment was subtidal. The considerable size of the flat pebbles and the complex nature of the surrounding matrix suggest that storm surges or tsunami may have disrupted beds and led to channelling and pebble formation.
Concealed Eocene outcrop beneath Shoreham Harbour, Sussex
Authors: Thomas L. P. , Gray D. A.
Published: May 2009

Evidence from a series of boreholes in the Shoreham area demonstrates the occurrence of an outcrop of Woolwich and Reading Beds lying beneath the drift deposits which form the floor of Shoreham Harbour. The classification of the Eocene strata, their structural relation to other deposits in the area and their conditions of deposition are examined.
Tuffisite with topaz from the Nigerian Younger Granite province — the Balfour Hill ‘sediments’
Authors: Wright J. B.
Published: May 2009

Near one of the Younger Granite intrusives of the Jos Plateau is a series of steeply dipping dark and predominantly fine grained rocks. Originally interpreted as argillaceous sediments thermally metamorphosed by the adjacent granite, with development of andalusite, later work established their volcanic origin but did not account for the andalusite. Field relationships and petrography of the rocks suggest they are tuffisites, emplaced by volcanic fluidization processes into part of the fracture system associated with the Younger Granite magmatism. The ‘andalusite’ is topaz, widespread in this province, mainly in the Younger Granite tin veins and greisens, sometimes as an accessory in the granites themselves, but not known from the volcanics — yet abundant in some of these tuffisites. It occurs in well formed crystals, displaying a ‘chiastolite-cross’ arrangement of inclusions, characteristic of andalusite but appearing not to have been previously recorded in topaz. The origin of the topaz must lie either in late-volcanic emanations or in hydrothermal fluids from the mineralizing stage of Younger Granite emplacement.
Marsupiocrinidae of the Laurel Limestone of southeastern Indiana
Authors: Frest T.
Published: May 2009

Three new species of Marsupiocrinus are described from the basal Wenlock Laurel Limestone of southeastern Indiana. Although the earliest representatives of the genus yet known, they display fully the specialized characters peculiar to it. Two new subgenera of Marsupiocrinus are erected on the basis of arm structure and cup shape.
The inifiltration rate into an aquifer determined from the dissolution of carbonate
Authors: Spears D. A. , Reeves M. J.
Published: May 2009

Changes attributable to weathering have been detected in Quaternary sediments overlying an important aquifer in the Vale of York. Solution of carbonates is quantitatively the most important effect of weathering. The amount of carbonate dissolved can be estimated from whole rock analyses. The length of time of weathering is known and an equivalent surface lowering rate for limestone can be calculated which is consistent with rates obtained by other workers.The volume of water required to give the observed compositional changes is calculated from porewater analyses. The time period is known and hence the rate of infiltration and the average recharge rate of the aquifer can be determined. The calculated rate of recharge is consistent with rates determined using other methods.
Shore platforms and wave ramps
Authors: Sherbon Hills E.
Published: May 2009

Examination of rocky coastal profiles in Australia and Europe suggests that two major and genetically distinct types of erosional surface should be recognized, one of these being the shore platform, whether sloping or horizontal, smooth or rough, which is best developed on promontories and terminates in a low-tide cliff, the other being the wave ramp, often exposed in bays, which slopes gradually down from about high water level to merge with the submarine slope near-shore. A modified terminology for erosional surfaces on rocky coasts is proposed.
Variably oriented co-planar primary folds
Authors: Borradaile G. J.
Published: May 2009

Curved and other variably oriented minor F1 folds with a common axial–planar cleavage are described from the Dalradian of the South-West Scottish Highlands. An explanation for the varying orientations is offered in terms of progressive deformation following the arguments of Flinn (1962) and Ramsay (1967).
Early Tertiary volcanic rocks on the Agulhas Bank, South African Continental Shelf
Authors: Dingle R. V. , Gentle R. I.
Published: May 2009

Tuffs, trachybasalts, aegirine–augite trachytes and aegirine–augite phonolitic trachytes occur on the continental shelf at the southern tip of Africa. They have been radiometrically dated at 58(±2.4) million years (Palaeocene), and together with other alkali-rich basic intrusions onshore form the Alphard Tertiary Igneous Province. Both onshore and offshore sites of intrusion appear to be strongly tectonically controlled.
The R. M. Brydone Collection of Cretaceous membranimorph Bryozoa
Authors: Medd A. W.
Published: May 2009

A revision of the species of the Upper Cretaceous membranimorph Bryozoa, established by R. M. Brydone between 1906 and 1941, has led to a considerable reduction in the number of species assigned to this group. These species are listed with the writer's opinion as to their more probable taxonomic position.
Discovering a meaning in scenery
Authors: Crickmay C. H.
Published: May 2009

A problem is seen in the claim (made ten years ago) that, under certain conditions, either during uplift of the crust or statically at high levels, denudation alone might develop a peneplain. Observations are now brought forward which seem to indicate that uplift, when active, exceeds the rate of stream erosion, which in turn always exceeds the rate of denudation; and from this, doubt arises as to the postulated peneplain origins.