bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hardgrounds in the Lower Leintwardine Beds (Silurian) of the Welsh Borderland
Authors: Cherns Lesley 
Published: May 2009

SummaryThe 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

SummaryThe 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

SummaryLoad-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

SummaryGeochemical 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.
A contribution to the nomenclature and classification of volcanic rocks
Authors: Middlemost E. A. K. 
Published: May 2009

SummaryAt 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

SummaryThe 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

AbstractIn 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

AbstractThe 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.
Silicified Lichidae (Trilobita) from the Middle Ordovician of Virginia
Authors: Tripp R. P. , Evitt W. R. 
Published: May 2009

SummaryThe 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

SummaryReidentification 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

AbstractLower 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

AbstractSectioning 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

SummaryOne 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

AbstractNew 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

SummaryIsopachytes 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

SummaryThe 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

SummaryStructural 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

SummaryThe 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

SummaryAssemblages 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

SummarySimple 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

SummaryCalcirudites 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

SummaryEvidence 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

SummaryNear 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

SummaryThree 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

SummaryChanges 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

SummaryExamination 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

SummaryCurved 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

SummaryTuffs, 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

SummaryA 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

SummaryA 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.