bluuebunny/crossref_metadata_2025_split huggingface dataset:
EVOLUTION OF ZIRCONS IN SEDIMENTARY AND METAMORPHIC ROCKS: A DISCUSSION
Authors: KALSBEEK F. 
Published: June 2006

SUMMARYSaxena's (1966a) paper on the “Evolution of zircons in sedimentary and metamorphic rocks” is discussed. The arguments for the stability of zircon during sedimentary and metamorphic processes are reviewed. Saxena's idea of an authigenic origin of the majority of zircons in some sediments seems to be the result of a misidentification of authigenic titaniferous minerals as zircon.
MEASUREMENT OF SAND TRANSPORT IN RIVERS WITH SPECIAL REFERENCE TO TRACER METHODS
Authors: CRICKMORE M. J. 
Published: June 2006

SUMMARYThe paper describes tests made on a small river to examine the practicability of measuring quantitatively, by tracer methods, sand transport occurring over a rippled bed in a natural channel. Three principal tracer methods, all previously verified under steady flow conditions in a laboratory channel, and identified as the spatial integration, time integration and steady dilution methods, were examined by introducing radioactive and fluorescent tracers to represent a narrow size fraction of the bed sand. The serious limitations of the time integration and steady dilution methods under conditions of unsteady solids discharge were exposed by a sudden flood discharge occurring during the course of the study. An approximate method, based on the time integration approach, but also requiring some spatial tracer data, is suggested, whereby an estimate of the transport is possible in the case of highly variable sand discharge. However, it is seen that in the sand case, the spatial integration method offers the most workable and informative tracer method for use in natural rivers. The results, by this method, were generally consistent with those given by the summation of the measured suspended‐solids flux and the transport occurring either by surface creep or in close vicinity to the bed. The latter quantity is determined from the downstream advance of the ripple bed‐forms, and methods are described for its derivation from ultrasonic echo sounder records of bed profiles. Finally sand transport values are calculated for a number of river discharges and for two laboratory channel tests using various well‐known computational procedures—Einstein, Bagnold, modified Einstein, Meyer‐Peter and Muller, and Laursen procedures. Significant differences in the computed values for individual flow conditions are observed.
SOME METHODS TO STUDY SURFACE TEXTURES OF SAND GRAINS
Authors: SOUTENDAM C. J. A. 
Published: June 2006

SUMMARYFor the study of the surface textures of quartz sand grains the normal microscope was used, besides the sofar generally applied electron microscope, and a new method was developed for using incident illumination. Grains from a desert sand and a river sand were studied, the former grains displayed textures not described yet by previous authors, the latter grains possessed a variety of textures, some of which have been found with beach sand grains, others with glacial sand grains by previous investigators.
GENERATION OF CUMULATIVE FREQUENCIES FROM THE CORRECTED PHI SIZE MOMENTS OF RANDOM THIN‐SECTION SIZE ANALYSIS DATA
Authors: SAHU BASANTA K. 
Published: June 2006

SUMMARYThe cumulative frequencies are obtained from the phi size‐distribution moments (duly corrected for random sectioning) based on either weight or number frequency thin‐section size data by the use of Grain‐Charlier approximation. From the cumulative frequency distribution the various size‐distribution statistics can be easily obtained and these statistics are useful for purposes of comparison, correlation, and interpretation of size data.
A QUANTITATIVE STUDY OF A SEQUENCE OF COAL‐BEARING CYCLES IN THE NAMURIAN OF CENTRAL SCOTLAND, 1
Authors: READ W. A. , DEAN J. M. 
Published: June 2006

SUMMARYElectronic computers have enabled the quantitative relationships between stratigraphic variables to be calculated for a sequence of Namurian (E1 zone) cycles deposited in a differentially subsiding basin east of Stirling. Despite their limitations, coefficients of correlation and linear regression equations provide a relatively simple means of expressing the relationships between critical variables and so provide a useful way in which various cyclically deposited sequences can be compared. All possible pairs chosen from eleven variables are investigated, including the total number and average thickness of cycles, total number of coals and total thicknesses of coal, sandstone and shale. These six variables all tend to show a linear relationship with total thickness of strata and hence net subsidence. A second part of this paper, to be published later, will examine the relationships between variables in more detail, using the technique of factor analysis.
EXPERIMENTAL INVESTIGATION ON THE EROSION‐SENSITIVITY OF A SAND‐CLAY LAMINATION
Authors: TERWINDT J. H. J. , BREUSERS H. N. C. , SVASEK J. N. 
Published: June 2006

SUMMARYThis report describes an investigation by means of laboratory tests of the critical shear stress and bed erosion as a function of time and bed shear stress for a sediment consisting of alternating sand and clay layers 0.1–3 cm thick (sand‐clay laminae). This type of deposit occurs quite frequently in estuaries and tidal inlets. The tests were carried out on an original bed deposited in an estuary.The critical shear stress and the degree of erosion in relation to time for the sand‐clay lamination were found to agree in order of magnitude with those for clay layers. The resistance to erosion of the sand‐clay lamination is therefore comparable with that of clay layers.
STATISTISCHE METHODEN IN DER MIKRO‐BIOFAZIES
Authors: ELTGEN HORST 
Published: June 2006

SUMMARY Statistical methods in micro‐biofacies This paper deals with statistical methods as applied to micro‐biofacies problems. The samples for the tests were taken from four quarries in Jurassic and Cretaceous limestones in northwestern Germany. The calculations are based on acetate‐peels. Two millions of figures were considered.The percentages of nine organic and nine inorganic components were calculated, hierarchically. In the beginning, the results were plotted as segments of circles. This way of representing the percentages of components just shows the general distribution of the main components.A more detailed picture can be given by plotting the distribution expressed in percentage, in reference to the distance of sampling points. The figures show the importance, not of the individual amplitudes, but of the average values of all amplitudes measured in one layer. Therefore, the change of the average amplitude represents a micro‐biofacies change of the layer under consideration. The measurements have shown that the differences in the distribution of the organic and inorganic components within the individual layers are not greater than those between the single layers.Correlation‐analyses had no positive results. Also tests of inhomogeneity did not give satisfying results. By decision‐analyses (discriminance‐analyses), however, it was possible to show small differences in the distribution of the components within the individual layers.Differentiations of the homogeneity and of the micro‐biofacies setting can be demonstrated by the intersections of the curves of the decision factors (=discriminance factors) and of the values of the arithmetic mean and sliding mean. By applying the X2‐test and/or variance‐analyses, the boarder lines between fields of homogeneity can be shown accurately.Information about the homogeneity of the tested samples and the number of samples necessary for getting representative data, can be calculated from sequence tests.
THE NATURE AND ORIGIN OF BED‐FORM HIERARCHIES
Authors: ALLEN J. R. L. 
Published: June 2006

SUMMARYThe bed forms generated by liquid flows over loose‐grain boundaries assume only two orientations relative to flow, being either transverse or longitudinal, but range enormously in physical scale. Two types of bed form, current ripples and parting lineations, take a characteristic length (2) which is independent of boundary conditions as expressed by flow depth (d). We have that:λL≤ 0.025 m (parting lineations)λR≤ 0.60 m (ripples).The characteristic length of other kinds of bed form is correlated with flow depth, according to the equations:λD= 1.16D1.1.55 (dunes)λA 6.3d (antidunes, Fr = 1.0)λSR= 1.35d1.31 (sand ribbons)λM ‐ 672d1.11 (meander bars)λT= 116d2 (tidal current ridges)From these relationships can be deduced the compositions of theoretical hierarchies of bed forms, where a hierarchy is defined as a series of bed forms graded as to size which in combination are adapted to a single overall flow condition. The compositions of these hierarchies, which are closely matched by naturally occurring hierarchies, are broadly related to available flow depth, general flow conditions (lower or upper regime), and availability of sediment.Bed forms are considered to be due to unstable interactions between the bed material and the over‐bed flow, of liquid or grains or both.Hierarchies of bed forms arise because the quantities determining the flow are suficiently numerous that several mutually unstable combinations can exist, each combination being expressed in terms of a bed form of a characteristic physical scale and orientation relative to flow.
A SHORT NOTE ON A COMPARATIVE STUDY OF SOME CENTRAL TENDENCY PARAMETERS FOR CIRCULAR DISTRIBUTIONS
Authors: DUMITRIU CHRISTINA 
Published: June 2006

SUMMARYFrom a physical point of view, the mode of circular distributions seems to be the most important central tendency parameter.Therefore, the deviations of the three other parameters of central tendency from the mode were studied, indicating that the vector mean may have the highest degree of stability with regard to the modal value.
EARLY DIAGENETIC CEMENTATION OF RECENT SANDS, FRASER RIVER DELTA, BRITISH COLUMBIA
Authors: GARRISON ROBERT E. , LUTERNAUER JOHN L. , GRILL EDWIN V. , MACDONALD ROBERT D. , MURRAY JAMES W. 
Published: June 2006

SUMMARYModern terrigenous sediments cemented by low‐magnesian calcite are found in distributary channels and adjacent shallow‐water marine localities at the front of the Fraser River delta. These permanently submerged areas are usually covered by sea water, including sea water intruded upstream along bottoms of river channels. The cemented sediments occur as irregular to platy nodular masses at or near to sediment‐water interface, where they are frequently encountered during dredging. The cement consists of small crystals arranged in fibrous rims and other aggregates around and between sand grains. Processes leading to cementation are not yet known, but may include dissolution of calcareous shells by pore waters in buried sediments, followed by precipitation of calcite at higher levels from these fluids as they are expelled upward during compaction.
MEASUREMENT OF PARTICLE SHAPE BY FOURIER ANALYSIS
Authors: SCHWARCZ H. P. , SHANE K. C. 
Published: June 2006

SUMMARYAn objective procedure is described for quantifying the shape of two‐dimensional closed curves from projections or sections of particles, e.g., sand grains. The curves are plotted in polar coordinates r and θ, and a harmonic analysis is made of the function r(θ) by numerical analysis of measurements at equally spaced sample points along the curves. Quantities corresponding to the conventional properties of sphericity and roundness are derived from the Fourier coefficients. Three different measures of roundness are proposed and shown to correlate with visually estimated roundness classes, though also depending to some extent on sphericity. An attempt is described to study the interaction between these two properties by analysis of synthetically rounded plastic particles.
CRINOIDAL TURBIDITES FROM THE DEVONIAN OF CORNWALL AND THEIR PALAEOGEOGRAPHIC SIGNIFICANCE
Authors: TUCKER MAURICE E. 
Published: June 2006

SUMMARYDevonian limestone turbidites from North Cornwall, composed mainly of crinoidal debris, are considered to have been derived from an oceanic rise or schwelle. Large‐scale cross‐bedding (representing division C) occurs in some limestone bands. The turbidites lack a pelitic division and there is usually a sharp contact with the shales above. Typical flutes are rare but broad grooves and channels are present on the soles.
SABKHA CYCLES IN THE ARAB/DARB FORMATION OFF THE TRUCIAL COAST OF ARABIA
Authors: WOOD G. V. , WOLFE M. J. 
Published: June 2006

SUMMARYStudy of 176 ft. (53.7 m) of core from the Arab/Darb Formation of the Umm Shaif Field, Abu Dhabi Marine Areas, has revealed a sequence of sediments which can be related to nine distinct cycles of sabkha formation. The sabkha cycle consists of a basal algal grainstone/boundstone (which is interpreted as a shoal) passing upwards through lagoonal dolomite, intertidal algal mat and into a final supratidal development of nodular anhydrite and associated dolomite. Dolomiti‐sation and the formation of nodular anhydrite were early‐stage products of diagenesis. Poikilotopic anhydrite is common in the lagoonal dolomites but it is thought that this was not formed until the sediment was completely lithified.Stylolites, although of small amplitude, are more common in dolomite than in limestone; a generalisation which is at variance with earlier observations.
EARLY STAGES IN DEVELOPMENT OF OVERGROWTHS ON ECHINODERM FRAGMENTS IN LIMESTONES
Authors: EVAMY B. D. , SHEARMAN D. J. 
Published: June 2006

SUMMARYThe present paper describes the first stages of echinoderm overgrowth by calcite, observed in partially cemented limestones from boreholes in the floor of the Persian Gulf. The overgrowths which develop as spires in the direction of the c‐axis of calcite show all essential features that were inferred in a previous paper for the early stages in development of overgrowths in fully cemented Jurassic limestones.
A STUDY OF THE DYNAMICS OF SUSPENDED MATTER BY MEANS OF NATURAL RADIOACTIVE TRACERS: AN APPLICATION TO THE GIRONDE ESTUARY
Authors: MARTIN J.‐M. , MEYBECK M. , HEUZEL M. 
Published: June 2006

SUMMARYThe determination of the natural radioelements in suspended matter in rivers and estuaries, lead to a simple relation between gamma activity and turbidity T, such as Nt=aTb (Nt counting rate caused by turbidity, a and b experimental coefficients). A new turbidimetry method is based on this relation and discussed here. In situ measurements have been conducted with field gamma scintillometers and compared with different turbidimetry methods, such as nephelometry, gravi‐metry and gamma ray absorptiometry. This method has been particularly convenient to continuous in situ measurements of turbidity from 0.5 g to several hundreds of g/1. This broad range is very well adapted to turbidity studies in estuaries.The new method has been applied to study suspended matter dynamics in the Gironde estuary (France) during November 1968, as a part of a more general study of natural radioactivity in terrigenous sediments brought into the ocean.
OVERCONSOLIDATION BY DESICCATION OF COASTAL LATE‐QUATERNARY CLAYS IN ISRAEL
Authors: KOMORNIK AMOS , ROHRLICH VERA , WISEMAN GDALYAH 
Published: June 2006

SUMMARYLate Quaternary clays in Haifa Bay and Ashdod Harbour are overconsolidated by desiccation. This conclusion was reached through analysis of the pre‐consolidation pressure as function of the actual overburden pressure, and by analogy with clays undergoing desiccation, and confirmed in laboratory experiments. It is in agreement with the known geology of the area.For pressures above 2.0 kg/cm2, a definite statistical relationship was established between the preconsolidation pressure and the in situ void ratio. For lower pressures, the in situ void ratio is mainly governed by environmental conditions during deposition and thought also to be governed by the clay mineralogy.
THE TIDE‐SWEPT CONTINENTAL SHELF SEDIMENTS BETWEEN THE SHETLAND ISLES AND FRANCE
Authors: KENYON N. H. , STRIDE A. H. 
Published: June 2006

SUMMARYExtensive data obtained by side‐scan Asdic and echo‐sounder equipments, viewed in conjunction with bottom notations on navigational charts and some seabed samples, show the widespread occurrence of sand ribbons, sand waves and sand patches on the continental shelf west of the British Isles and France. The close similarity of their directional trends with those of the strongest tidal currents strongly suggests a causal relationship which applies to much of the continental shelf, parts of the upper continental slope and also to off‐lying shoals such as Rockall Bank. The sand transport paths broadly parallel the coasts in the epicontinental seas and on the open shelf west of the British Isles. In contrast, the paths are substantially normal to much of the coast of western France.
LATE PLEISTOCENE DIAGENESIS AND DOLOMITIZATION, NORTH JAMAICA1
Authors: LAND LYNTON S. , EPSTEIN S. 
Published: June 2006

SUMMARYDiagenesis, including dolomitization, of Late Pleistocene reefs of North Jamaica is due to reaction with meteoric water. Although the reactions:

Mg‐calcite—calcite

Aragonite—calcite

Mg‐calcite—dolomite

retain microarchitectural information, complete chemical redistribution takes place so that incongruently dissolved Mg‐calcites, aragonite inversion mosaics (neomorphosed aragonite), and dolomitized red algae have similar isotopic compositions, resembling precipitated calcite cements. The minerals all appear to have stabilized in the meteoric water environment. The dolomite is not widely distributed, and is restricted to replacement of red algae. There has been no net addition of magnesium to the red algal clasts.
CORRELATION BETWEEN PHOSPHATE CONTENT AND THE FORAMINIFERAL PLANKTON/BENTHOS RATIO IN CHALKS (LATE CRETACEOUS, NORTHERN ISRAEL): PALEOENVIRONMENTAL SIGNIFICANCE?
Authors: FLEXER A. , STARINSKY A. 
Published: June 2006

SUMMARYTwo environments of phosphate deposition within carbonate rocks are distinguished on the basis of the relationship between phosphate content and the foraminiferal plankton/benthos (P/B) ratio in Senonian‐Maastrichtian chalks of Galilee, Northern Israel:(1) A normal marine environment of phosphate deposition during Santonian time. This environment is characterized by a low, normal P2O5 content and a positive correlation between P/B ratio and P2O5. Since it is assumed that the P/B ratio increases with the depth of the sea, it is suggested that the phosphate content in carbonate rocks can be employed as a bathymetric indicator.(2) An “abnormal” high phosphate deposition environment, found mainly in Upper Campanian sediments and related genetically to the economic phosphorite deposits in the Negev (Central Israel). The negative correlation of P/B ratio to P2O5 is caused by a shallowing of the sea and a continuous increase in P2O5, (e.g., by upwelling currents or a terrigenous supply) throughout the Upper Campanian.
DETERMINATION OF THE TIME OF OIL AND GAS ACCUMULATION BY EPIGENESIS STUDIES
Authors: PROZOROVICH G. E. 
Published: June 2006

SUMMARYThe paper describes a method for determining the time of formation of oil and gas accumulations on the basis of the number of epigenetic minerals contained in granular reservoir rocks. The beginning of the accumulation is established by comparing the epigenesis stage in the oil‐ or gas‐bearing crest areas of the trap with the water‐bearing part of the reservoir at different depths of the geological section. This takes into account that the epigenetic processes tend to intensify with depth and to slow down after the rocks become filled with hydrocarbons.The time of accumulation completion is found by comparing the degree of epigenetic alteration of the oil‐ and gas‐bearing reservoirs with the water‐bearing reservoirs occurring at the oil (gas)‐water interface in the trap. The greater the differences, the older is the age of the pool completion. Lack of a difference indicates a youthful pool completion.In this paper, the ratio of detrital to authigenic titanium minerals, the quantity of regenerated quartz grains, and the pelitization of feldspars have been used.The application of this method is exemplified by oil deposits occurring in the productive Valangien and Hauterive beds (Lower Cretaceous) of the Ust‐Balyk and Megion fields of western Siberia.
GENETIC INTERPRETATION OF THE POLYMORPHISM OF THE KAOLINITE GROUP IN SEDIMENTARY ROCKS
Authors: SHUTOV V. D. , ALEKSANDROVA A. V. , LOSIEVSKAYA S. A. 
Published: June 2006

SUMMARYThe paper presents the dynamics of the structural change of kaolinite and its polymorphous (polytype) modifications at different stages of sedimentary rock formation. Sedimentogenesis is characterized by a gradual disordering of structure of triclinic kaolinite, the degree of disorder produced being proportional to the intensity and duration of the influence of the hydrodynamic medium. Epigenesis (deep) is connected with gradual transformation of kaolinite into dickite through the stage of mixed‐layer growths inheriting the structure of twin rotations of disordered kaolinite from the sedimentogenesis stage.In metagenesis filling of fissures with dickite or nacrite takes place. The former is peculiar to the general thermodynamic medium of deep epigenesis/metagen‐esis, whereas nacrite is an indicator of intense stress and seems to be due to transformation of dickite.
FORMATION OF CARBONATE CEMENT IN CLASTIC ROCKS
Authors: MURAVYOV V. I. 
Published: June 2006

SUMMARYThe texture of carbonate cement in clastic rocks reflects the conditions of: (1) free pore crystallization; or (2) recrystallization under elevated temperatures and pressures. Fibrous carbonate cement may be formed as a result of preferential adsorption of clay particles or colloids in the direction perpendicular to c. Cryptocrystalline carbonate cement is formed in sandstones if the ratio carbonate/ argillaceous matter in less than 5 (for montmorillonite) or less than 3–4 (for illite), especially if it is near 2–1.The maximum amounts of isomorphic admixtures of Mg and Fe in calcite cement (see Fig.2) can be used for temperature reconstructions of the epigenetical environment.In deep‐buried rocks which are almost closed systems, migration rates are lower than diffusion rates and microenvironments of detrital grain corrosion may exist adjacent to those of precipitation of the same mineral.
NEW ASPECTS OF THE OPTICAL STUDY OF LAYER SILICATES
Authors: DRITS V. A. , MURAVYOV V. I. , SHUTOV V. D. 
Published: June 2006

SUMMARYThe structure of multilayer polytype modifications of layer silicates may be regarded as the result of a combination of regularly oriented single layers. Accordingly, the optical constants of a single layer (of a monolayer polytype modification) may be used for the calculation of optical constants of any other multilayer polytype modification of a given type of layers.The formulas connecting the constants of a polytype modification of layer silicates have enabled the establishment of the main parameters (Ng, Nm, Np, 2V) of the muscovites 1M and 2M2 according to the known optical constants of the muscovite 2M1, and the computation of the new constants of kaolinite and nacrite based on the known parameters of dickite. The optical constants established theoretically were confirmed by direct measurements for muscovite 1M, muscovite 2M2 (gämbelite) and kaolinite. The optically positive character of kaolinite with +2V = 25° has been established.The assumption of the optical mixibility of finely dispersed polyminerallic media, in which the dimensions of monotype crystals are smaller than the visible light waves, made it possible to determine the quantitative relations of clay minerals in the mixtures based on optical constants of oriented aggregates.