bluuebunny/crossref_metadata_2025_split huggingface dataset:
LESSONS FROM A FEASIBILITY STUDY FOR COMPUTER MODELS OF COAL‐BEARING DELTAS
Authors: OERTEL G. , WALTON E. K. 
Published: June 2006

SUMMARYA computer‐generated model of a coal‐bearing delta would be desirable if it included enough detail to reproduce the cyclical nature of the sediments. At the present stage of development of computers, and with the present state of knowledge of the quantitative aspects of transportation and sedimentation, it is not yet possible to set up such a model. However, the logical arrangement in a flow‐diagram of the processes and parameters involved in delta formation strongly suggests that cyclical sedimentation can occur without the need for an external cyclical cause, such as tectonic or climatic oscillations. Attempts to provide for appropriate checks of a computer model bring out overall regularities in the assemblages of cyclic types in three different coal basins.
X‐RAY RADIOGRAPHY FOR EXAMINATION OF BURROWING IN SEDIMENTS BY MARINE INVERTEBRATE ORGANISMS1
Authors: HOWARD JAMES D. 
Published: June 2006

SUMMARYExamination of the primary sedimentary texture of rocks and sediments by X‐radiography can be extended to include the study of bioturbation and burrowing by living organisms. This technique involves making time‐lapse X‐radiographs while the animals are in the process of disturbing the sediment.Artificially and naturally stratified sediments are contained in plexiglass aquaria connected to a continuously flowing seawater system. The burrowing animals to be studied are introduced into these aquaria and the effect of their activities on the sediments is recorded by X‐radiography over a period of hours, days or weeks.
A QUANTITATIVE STUDY OF A SEQUENCE OF COAL‐BEARING CYCLES IN THE NAMURIAN OF CENTRAL SCOTLAND, 2
Authors: READ W. A. , DEAN J. M. 
Published: June 2006

SUMMARYThe quantitative relationships between stratigraphical variables from a succession of coal‐bearing cycles deposited in a subsiding basin have been investigated using principal component‐ and factor analysis, in an attempt to reveal simple relationships undetected by conventional qualitative methods. Knowledge of such relationships will undoubtedly be useful in future computer simulation studies of cyclical sedimentation. Principal component analysis and factor analysis yield similar results, which confirm and amplify those of the trend surface analysis described in Read and Dean (1967).
THIN‐SECTION SIZE ANALYSIS AND THE MOMENT PROBLEM
Authors: SAHU BASANTA K. 
Published: June 2006

SUMMARYThe observed size in the thin‐section is less than the true grain sizes of the clastic rock as the thin‐section plane does not necessarily pass through the centre of gravity of the grains. Correction factors based on probability theory give corrected arithmetic moments of the size distribution in the clastic rock from the observed arithmetic moments of the size distribution in the thin‐section. The corrected arithmetic moments so obtained are transformed to their equivalent corrected phi moments which are useful to generate the unknown size distribution of the clastic rock by the help of Edgeworth's series.
TECTONIC CYCLES AND REGULARITIES IN THE DEVELOPMENT OF SEDIMENTARY ROCKS AND PALEOGEOGRAPHIC ENVIRONMENTS OF SEDIMENTATION OF THE RUSSIAN PLATFORM (AN APPROACH TO A QUANTITATIVE STUDY)
Authors: RONOV A. B. , MIGDISOV A. A. , BARSKAYA N. V. 
Published: June 2006

SUMMARYAn attempt was made to find the ways for quantitative estimation of changes of the sedimentation processes and paleogeographic environments in the geological past. Quantitative regularities on the basis of rock volume measurements were found in the history of sedimentation and environmental conditions on the Russian Platform beginning in Late Riphean (Pt3) until Quaternary, through the main geotectonic cycles (Caledonian, Hercynian and Alpine).It was shown that there were no major differences between sand and clay abundance (26.0% and 30.1%, respectively). Limestones are most abundant among carbonate rocks (17.0%), followed by dolomites (10.2%), then marls (7.5%) and finally chalk (2.0%). Surprising was the very high abundance of gypsum and anhydrite (2.7%) and of salts (3.1 %). Being in agreement with data of many other regions of the world, this fact has far reaching consequences, first of all, concerning the history of ocean salinity and, secondly, for the knowledge of geochemical cycles of Na, C1 and S.A predominance of terrigenous sedimentation has been found for the Caledonian and Alpine cycles, whereas a greater abundance of chemical and biochemical sedimentation occurred in the Hercynian (Variscian) cycle. Each of these cycles is characterized by the common scheme of periodical recurrence of main rock types from the initial to the final stages. (Fig. 2).Fig. 8 shows the prevailing role of uplift and erosion on the Russian Platform (76% of the total platform area); only 5.7% of the area falls on the continental sedimentation, 1.8% on the lagoon environments, and 16.5% on the marine sedimentation. This is in contrast to the geosynclines which were dominated by marine sedimentation. Considering now only the regions of stable subsidence and “fixed” sedimentation of the Russian Platform (Fig. 5) we find that here marine sedimentation dominated (68.9% of the areas of stable subsidence) in comparison with the continental environments (23.6%). As well as the abundance of sediments, the distribution of the main types of paleogeographical conditions changed during the cycles with extreme regularity according the periodic law. (Fig. 6,7). The periodicity of sedimentation and the alteration of paleogeographical conditions were finally determined by the periodical rhythm of platform epirogenic movements.
THE MEASUREMENT OF THE SIZES OF NON‐SPHERICAL PARTICLES BY THE HYDROMETER METHOD
Authors: McCANN C. 
Published: June 2006

SUMMARYIt is shown that in calculating the viscous force on a non‐spherical particle suspended in a fluid, it is necessary to use the largest dimension of the particle. This may be calculated from the diameter of the equivalent sphere obtained from a hydrometer analysis provided the shape of the particle is known.
QUANTITATIVE ANALYSIS OF BEACH SAND MOVEMENT, VIRGINIA BEACH, VIRGINIA1
Authors: BOON JOHN D. 
Published: June 2006

SUMMARYA simplified stochastic‐process model involving statistical procedures is used to analyze sand tracer displacement data on an ocean beach. The procedures provide meaningful estimates of the direction and magnitude of the movement of beach sand through set intervals of time.Results of a single tracer experiment are reported for a beach located near Virginia Beach, Virginia. Using a rectangular sampling grid, tracers were recovered at fixed times, then considered as items in a sample of X and Y displacements from the point of release. Comparison of the adjusted means of these samples on a time‐ stratified basis gave estimates of average particle velocity in two dynamic zones:(1) swash zone: v̄(X) = 0.44 ft./min (0.22 cm/sec) longshore; (2) surf zone: v̄(Y)= 0.37 ft./min (0.19 cm/sec) offshore.Using an estimate of the thickness of the mobile layer (the depth interval in which semi‐continuous motion of beach sand occurs), a further estimate of the rate of longshore sand transport was computed at 440 yards3/day (336 m3/day).
FORMATION OF QUARTZ OVERGROWTHS IN THE PENRITH SANDSTONE (LOWER PERMIAN) OF NORTHWEST ENGLAND AS REVEALED BY SCANNING ELECTRON MICROSCOPY
Authors: WAUGH B. 
Published: June 2006

SUMMARYThe development of optically continuous quartz overgrowths is governed by the atomic structure and crystallographic orientation of the detrital quartz grains. Initial growth commences with the appearance of numerous oriented projections, with rhombohedral and prismatic form, on grain surfaces. Merging and overlap of the projections results in the formation of large crystal faces whose form is dependent upon the initial location of the projections with respect to the internal crystallographic axes. Growth is particularly rapid along the direction of the c‐axis. For unicrystalline quartz grains the ultimate growth phase is the production of polyhedral quartz crystals having the appearance of hexagonal dipyramids. In polycrystalline grains each quartz unit within a single grain develops a separate overgrowth, the form of which is similarly controlled by the internal structure of the individual quartz units. Hence, the completed overgrowth shows an irregular distribution of diversely oriented prism and rhombohedral faces.
PROBLEMS OF QUARTZ GRAIN MORPHOSCOPY
Authors: SCHNEIDER HORST E. 
Published: June 2006

SUMMARYIn a historical review of the development of quartz‐grain morphoscopy some unsolved problems such as the real aspects of the details on frosted grain surfaces and the interpretation of the origin of different surface textures are elaborated. Discrepancies in the presentation of quartz‐grain types as observed by electron microscopy are mentioned. It is proposed to relate such investigations to CAILLEUX's (1942) classical morphoscopic method; this could be facilitated by the modern scanning electron microscope. The possibilities and advantages of this instrument for morphoscopic research are presented by first results concerning the surface textures of original quartz grains derived from a weathered granite and of experimentally and naturally etched grain surfaces. For generalized conclusions a greater number of further observations must be made.
MINERAL STUDIES IN THE GRAVITATION‐GRADIENT FIELD, 2. CHANGES OF QUARTZ SAND DENSITY DUE TO NATURAL AND EXPERIMENTAL “MATURATION”
Authors: KATZ M. YA. , KATZ M. M. , RASSKAZOV A. A. 
Published: June 2006

SUMMARYBased upon studies of natural quartz and upon laboratory experiments on mechanical and chemical destruction of quartz, it was established that the statistical density characteristics of detrital quartz change during sedimentary processes. Grains with defective structure, gas‐liquid inclusions, inclusions of organic matter and other lighter minerals have lesser densities, whereas grains with inclusions of heavier minerals have larger densities than those of optically pure grains. The susceptibility to destruction is less for optically pure grains than for grains with lower or higher density. This is responsible for the increasing maturity of quartz sand during weathering and transport as indicated by the increasing percentage of optically pure grains. Mathematical modelling of the dynamics of this process was carried out.
ON THE IDENTIFICATION OF MONTMORILLONITE MINERALS IN THE PRESENCE OF AMORPHOUS MATERIALS
Authors: MURAVYOV V. I. 
Published: June 2006

SUMMARYThe distinction of montmorillonite proper from beidellite is often based on the Li‐test proposed by GREENE‐KELLY (1953). However, when saturated with Li, true montmorillonite samples that contain considerable admixtures of SiO2 or Fe2O3hH2O behave in the same way as beidellites. An irreversible sorption of Li (after annealing at 250°C) is observed in such samples only after the admixed amorphous substance has been removed by leaching with a NaCO3 or HCI solution
MICRITIC ENVELOPES OF CARBONATE GRAINS ARE NOT EXCLUSIVELY OF PHOTOSYNTHETIC ALGAL ORIGIN
Authors: FRIEDMAN GERALD M. , GEBELEIN CONRAD D. , SANDERS JOHN E. 
Published: June 2006

ABSTRACTMicritic envelopes are commonly believed to develop from the lime‐mud infillings of circumferential perforations made in skeletal particles by algae. Because “algae” are usually taken to mean photosynthetic algae, the corollary has been proposed that micritic envelopes would not appear on carbonate skeletal particles originating in waters too deep for active growth of photosynthetic algae. Extensions of this “photosynthetic‐algae‐only” origin of micritic envelopes implies that: (1) the disappearance of envelopes with depth could mark a useful paleobathymetric datum; and (2) preservation of outlines of skeletal particles should be much better in “shallow”‐water carbonates than in “deep”‐water carbonates.We doubt the validity of the depth‐limiting concept of the origin of micritic envelopes for two reasons: (1) petrographic study of a large number of thin sections thought to be representative of various paleo‐depth levels does not indicate any systematic variations in the preservation of the outlines of skeletal particles; and (2) molluscan skeletal debris displaying micritic envelopes and effects of borings identical with those generally ascribed to the activities of photosynthetic algae have been found in an aragonite‐cemented sandstone from the Atlantic shelf where geologic evidence indicates that the water at time of boring was too deep for active growth of photosynthetic algae.Accordingly, we re‐emphasize the fact that organisms other than photosynthetic algae can bore into calcareous materials. In particular, fungi, bacteria, and heterotrophic algae (whose distribution does not depend on the penetration of light into seawater) are known to be active borers. Bacteria can be eliminated as producers of bores having diameters greater than approximately 10 μ. Fungi create boring structures with radiating or branching patterns or bores with nonuniform size. Some fungal bores appear to be indistinguishable from excavations known to have been bored by photosynthetic blue‐green algae. At present we do not know how to distinguish the results of boring activity of photosynthetic algae from those of algae living het‐erotrophically.
BREAK OF SLOPE IN PARTICLE‐SIZE CURVES OF GLACIAL TILLS
Authors: BEAUMONT PETER 
Published: June 2006

ABSTRACTIn studies of particle‐size distribution of the less than 20‐mm fraction of glacial clays in eastern Durham it is noted that one particular characteristic seems common to them all. When the particle‐size data obtained by sieving and hydrometer analysis are plotted on semi‐logarithmic graph paper (BRITISH STANDARDS, 1961) it is seen that almost all the curves are made up of two shallow concave or straight sections separated by a small section of varying convexity. What is perhaps most surprising is that this convexity or marked break of slope is nearly always found in the range 0.2–0.8 mm. The break of slope shows that the material in the finer grain sizes is more abundant than the coarser material.The question arises as to what is the cause of this break of slope and whether it is a sorting characteristic of sub‐glacial processes or is explicable in terms of parent‐material lithology.
DOWNCURRENT DECLINE OF GRAIN SIZE AND THICKNESS OF SINGLE TURBIDITE BEDS: A SEMI‐QUANTITATIVE ANALYSIS
Authors: SCHEIDEGGER A. E. , POTTER PAUL EDWIN 
Published: June 2006

ABSTRACTSedimentologists have noted that turbidite sequences become thinner bedded and finer grained as traced downcurrent. We provide a semi‐quantitative explanation of this behavior based on the idea that turbulence in a turbidity current decays downcurrent so that in its zone of deposition both the total load in suspension and the grain size of that load decrease with increasing distance from the source. Semi‐empirical equations proposed by Chézy, Lokhtin and Sundborg are central to our argument.
FIGURES DE COURANT ET TRACES DE PATTES D'OISEAUX ASSOCIEES DANS LA MOLASSE MIOCENE DE DIGNE, BASSES ALPES (FRANCE)
Authors: BEAUDOIN B. , GIGOT P. 
Published: June 2006

ABSTRACTThe Miocene “molasse” of Digne (subalpine chain) is studied in the profile along the Bramefan torrent. Gross lithological and paleontological contents, textures, structures and sole marks are described. All the types of sole marks are present (cf. the Plates), as in turbidites, but they point sometimes to opposite current directions on the same sole. Large‐scale (decimeter to meter) cross‐stratification is frequent. Graded bedding is very scarce. These observations do not indicate turbidites.These coarse‐bedded, well‐sorted sediments are interpreted as high‐energy deposits. Bird tracks and Mya in living position suggest a beach environment.Some “molasse” formations of Rumania and Spain are then discussed, especially with reference to MANGIN (1962) who shows, near a photograph of the Liedena formation, a picture of bird tracks from Barles: this example comes from the abovementioned Digne molasse, and is not an argument for the occurrence of such tracks in a new “flysch” near Digne.
LIMONITIC CONCRETIONS FROM THE EUROPEAN JURASSIC, WITH PARTICULAR REFERENCE TO THE “SNUFF‐BOXES” OF SOUTHERN ENGLAND
Authors: GATRALL MICHAEL , JENKYNS HUGH C. , PARSONS COLIN F. 
Published: June 2006

ABSTRACTLarge discoid (1–30 cm), carbonate‐rich limonitic concretions or “snuff‐boxes” are contained in stratigraphically condensed limestones from the Jurassic of southern England and parts of Europe. Their general association with conglomerates and algal stromatolites suggests formation in turbulent shallow water on submarine swells, or a shallow marginal shelf. The surprisingly uniform growth‐form of the “snuff‐boxes”, together with their gradation into obvious calcareous oncolites and stromatolites, is taken as evidence that they too may have been formed, at least partially, under algal influence.The geochemistry of the concretions, dominantly ferruginous, with subordinate phosphate, suggests deposition in an epicontinental environment, probably under the influence of considerable river drainage. They therefore contrast with the more trace‐element rich ferromanganese nodules which occur in some condensed pelagic sequences.
INTENSITY OF DEPOSITION FROM AVALANCHES AND THE LOOSE PACKING OF AVALANCHE DEPOSITS
Authors: ALLEN J. R. L. 
Published: June 2006

ABSTRACTAn avalanche of granular solids deposits grains once its snout is arrested at the base of the surface of avalanching. During deposition the avalanche behaves as a settling column of dispersed particles; the surface of deposition within the column is marked by a distinct shadow, or continuity wave, which swiftly climbs the sliding mass. Empirically, the high intensities of deposition expected from avalanches behaving in this manner correspond to degrees of packing in the deposits that are very nearly the loosest possible for natural materials. This appears to explain why cross‐stratified sediments have low strengths and are readily deformed.
BEACH STRUCTURES PRODUCED BY CRAB PELLETS
Authors: CHAKRABARTI A. 
Published: June 2006

ABSTRACTIt has been observed that seashore crabs produce various designs by the ejected faecal pellets. Study of such structures shows a clear association of them with different parts of the beach. Mossy structures are found only in the upper beach part, i.e., along the high‐water line, whereas concentric‐radiating and asteroid types are encountered in the middle beach area. In regions above mean high‐tide line burrow openings are surrounded by loose sediments and are devoid of any patterns. In the lower beach zone such structures are lacking. If the beach materials are more silty in character, faecal pellets congregate and stand out as knobby surfaces.Closer examination of such structures, if preserved in ancient sediments, may not only help in delineating the ancient shoreline positions but also may help in demarcating littoral micro‐environments.
ANTIDUNE CROSS‐STRATIFICATION IN A TURBIDITE SEQUENCE, CLORIDORME FORMATION, GASPÉ, QUEBEC
Authors: HAND BRYCE M. , MIDDLETON GERARD V. , SKIPPER KEITH 
Published: June 2006

ABSTRACTThe equation used by Skipper (1971) to derive flow velocity from antidune wavelength is satisfactory for open‐channel conditions, but must be modified for antidunes formed by density currents. Calculations based on the modified equation indicate a much higher flow density than was originally proposed for antidunes of the Cloridorme Formation. It further appears that the water waves accompanying these particular antidunes developed not at the upper boundary of the turbidity current, but at a density discontinuity within a few centimeters of the bed. Textural features of the Cloridorme turbidites are compatible with this interpretation.
BRECCIAS DEPOSITED BY MASS FLOW IN THE BRECCIA NAPPE OF THE FRENCH PRE‐ALPS
Authors: HENDRY HUGH E. 
Published: June 2006

ABSTRACTIn the Lower Breccia Formation (Lower Jurassic), variations in thickness of the breccia sequence, in individual bed thickness, and in size of clasts suggest separate sources to the southwest and north of the study area. Large clasts, poor clast rounding, grading, and restriction of stratification towards the tops of individual beds indicate deposition by mechanisms other than normal marine bottom currents. The deposits are too thick to have been deposited from the bed load of many successive sandy turbidity currents. A mass‐flow origin is therefore favoured. The stratification in the breccias is believed to have formed at a late stage in their deposition. It is considered to be a result of traction of clasts at the tops of beds by fluid entrained by the flow, or turbidity currents associated with the flow.
OBSERVATIONS ON DUNES AND BI‐MODAL SANDS IN THE TÉNÉRÉ DESERT
Authors: WARREN A. 
Published: June 2006

ABSTRACTObservations of dune patterns in the central Ténéré desert, Niger, reveal a significant association between different dune morphologies and sand types. It is suggested that the bi‐modal sands that are associated with low dunes and flat areas can be explained by the protection of fine sands in the inter‐particle voids of the coarse creep fraction.
ORIGIN OF PHOSPHORITE OF THE LATE PRECAMBRIAN GANGOLIHAT DOLOMITES OF PITHORAGARH, KUMAUN HIMALAYA, INDIA
Authors: VALDIYA K. S. 
Published: June 2006

ABSTRACTThe Precambrian Gangolihat Dolomites of the Pithoragarh area in the Kumaun Himalaya, characterized by rich and widespread development of the stromatolites belonging to theBaicalicagroup, are poorly to moderately phosphatic. The intimate and constant association of collophane with the branching stromatolites suggests that algae played a significant role in the localization of phosphate in the dolomites formed in very shallow and warm waters of the sea. The phosphatization of the stromatolites occurred during the later, almost penultimate period of the Gangolihat times, when theBaicalicagroup of algal stromatolites was in its heyday of development. The replacement of carbonates by collophane took place a little before and during the sedimentation of the clastic calcarenites that fill the space between the columns of algal structures. What is uniquely distinctive and significant in the Pithoragarh area is the association with algal bioherms of the lentiform deposits of very coarsely crystalline magnesite. The magnesite that has replaced the phosphatized stromatolite‐bearing dolomites not only preserves excellently the original stromatolitic structure, but its phosphatized parts as well. This shows that the phosphatization pre‐dates the origin of magnesite.