bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE CONDITIONS OF GROWTH OF THE WENLOCK REEFS OF SHROPSHIRE (ENGLAND)
Authors: SCOFFIN TERENCE P. 
Published: June 2006

ABSTRACTDistribution and size of the reefs in the Wenlock Limestone (Mid‐Silurian, Wenlock area) indicate that the most suitable site for growth was at the seaward fringe of the reef belt. The reef development increased through time as clay‐mineral concentration reduced. Many reefs colonized small mounds of coarse crinoidal debris but growth also started on soft muddy substrates. The Wenlock structures have similar characteristics to modern patch reefs: they are small—the average width is 12 m and the thickness 4.5 m—and roughly oval in section. During growth reef surfaces were gently convex and reached heights of between 50 cm and 3 m above the sea bed.The organic framework of all reefs examined consisted of massive and branching tabulate corals, stromatoporoids, branching rugose corals and bryozoans; with stromatolites, laminar corals and stromatoporoids and bryozoans playing the role of reef binders. Most reef builders grew contiguously and are preserved in growth position. Biotic zoning within reefs was not detected. Biomicrites accumulated in interstices near the surface of the reef at the time of, and just shortly after, organic growth. The sea was probably less than 30 m deep and extreme shallowing at the close of the Wenlockian terminated reef development. However, reefs were not broken up by wave or current action. The inter‐reef sediments, which were deposited at the same rate as reef growth, are predominantly argillaceous crinoidal biomicrites alternating with thin shale bands. Very few beds of reef‐derived talus occur (Fig. 13–15). High influxes of clay minerals—especially bentonites—brought about local reef death.Diagenetic processes of dissolution, recrystallisation and compaction greatly modified the original fabric of the reefs.
SEDIMENTATION IN THE ICE‐CONTACT ENVIRONMENT, WITH EXAMPLES FROM SHROPSHIRE (ENGLAND)
Authors: SHAW J. 
Published: June 2006

ABSTRACTGlacial sedimentation is assigned to two environments, the pro‐glacial and the ice‐contact. This paper is concerned with sedimentation in the ice‐contact environment. The sub‐drift topography of the area of study and the direction of ice movement are shown to be conducive to ice stagnation which is necessary for widespread ice‐contact sedimentation. Ridges of glacigenic sediment show faulted, collapsed margins and lateral kettle holes characteristic of ice‐contact landforms. The internal structure of these ridges is analysed in terms of primary and secondary sedimentary structure and texture. The spatial distribution of sedimentary structure and texture is shown to be similar to the fluvial models of Allen (1964) and Visher (1965). The absence of lateral extension of the fluvial members is interpreted as being due to stream training by ice walls preventing lateral migration. Large thicknesses of horizontal stratification and strongly unimodal palaeocurrent estimates are believed to be a result of this low sinuosity. Primary sedimentary structure and texture are used to designate facies. The distribution of the facies is thought to be diagnostic of the ice‐contact environment. Downstream facies migration is thought to have occurred as a result of changes in the ratio of sediment supply to stream power.
LINAER SAND BANKS IN THE SOUTHERN NORTH SEA
Authors: CASTON V. N. D. 
Published: June 2006

ABSTRACTThe majority of the linear sand banks in the Norfolk Banks area of the southern North Sea are considered to be large‐scale mobile bed forms in dynamic equilibrium with the environment, thus confirming much of the earlier work of Houbolt (1968). Sand streams moving in opposing directions on either side of a bank are shown to be deflected to the right, upslope, and converge at the crestline, whilst the asymmetry of a bank is considered to be a reflection of the dominance of one of these streams. Convergence of sand streams causes an accumulation of sand which is believed to result in the continuing growth of the bank parallel to the direction of flow of the tidal currents. Migration of asymmetric banks is in the direction of the steeper side; the predominant direction is to the northeast, but it is suggested that the opposing movement of sand streams may magnify localized irregularities into a complex “S” shaped bank surrounding a pair of ebb and flood channels. The apices of this bank may eventually disappear, leaving a line of en echelon banks. Confirmatory evidence is forthcoming from a study of a linear sand bank lying off the Belgian coast, and it is suggested that the general sequence of bank development may be of far wider application.
GENESIS OF LAMINATED SAND AND GRADED RHYTHMITES IN STORM‐SAND LAYERS OF SHELF MUD
Authors: REINECK H. E. , SINGH INDRA B. 
Published: June 2006

ABSTRACTThe formation of laminated sand and graded rhythmites — so‐called storm‐sand layers — found embedded in shelf mud is discussed. With decreasing energy of a storm, the sand eroded on the coast is transported away by the retreating waters into the open sea, and is retained in suspension because of the high wave energy of the rough sea. With decreasing wave energy, the individual suspension clouds settle, forming parallel sand layers. As generally only slow bottom currents are present, the sediment deposited is not reformed into ripples, but sedimented in the form of laminated sand.
STRUCTURE AND PROCESS IN A BRAIDED RIVER
Authors: RUST BRIAN R. 
Published: June 2006

ABSTRACTThe Donjek is a proglacial braided river with a coarse heterogeneous bedload ranging from −7 to +8 φ. The three reaches studied comprise, in downstream order, a zig‐zag reach formed by the interaction of the river and tributary fans, a straight reach, and a meandering reach, all with internal braids. The straight to meandering junction is unusual in that slope and discharge both increase.The dominant bed‐forms are longitudinal gravel bars, which migrate only during flood. Their internal structure is poorly defined horizontal bedding, which suggests that gravel deposition takes place on the upper bar surfaces, rather than on foreset slopes at the downstream margins. At lower stage sand accumulates in wedge‐shaped units lateral to the bars, with internal high‐angle cross‐stratification and ripple cross‐lamination; other sedimentary structures are rare. A simple facies model can be constructed on the basis of two trends: a proximal‐distal trend, and an active‐stable trend. Both result in the increased abundance of fine‐grained sediment.Random directional measurements give good estimates of the river trend from small‐scale structures (mainly ripples) and from channels, the latter giving the closest approximation. The variability of ripple orientation always exceeds that of channels. Both increase in the meandering reach, although the divergence of the vector mean from the river trend is not significantly greater than in the straight reach.
ORIGIN AND DISTRIBUTION OF CALCAREOUS FINES ON THE CAROLINA CONTINENTAL SHELF
Authors: MOLNIA BRUCE F. , PILKEY ORRIN H. 
Published: June 2006

ABSTRACTThe fine carbonate fraction (less than 63 μ in diameter) in 175 sediment samples collected from the Carolina continental margin has been studied. This fraction, generally under 5% of the total sample, averages 43% CaCO3. By comparison, the CaCO3 fraction of the total samples averages only 25%. On the inner shelf, the percentage CaCO3 in the fine fraction is twenty or more times greater than the percentage CaCO3 in the total sample. With increased distance offshore, the percentages of CaCO3 in the fine fraction and the total sample approach equality. Beyond the shelf break the percentage of CaCO3 in the total sample is greater than that in the fines.The CaCO3 faunal components are primarily foraminifera, fragments of foraminifera, mollusc‐barnacle fragments and echinoid material. Minor constituents include alcyonarian and tunicate spi‐cules, Halimeda and other calcified green algae. Many grains are bored and show solution effects. The coarse carbonate fraction shows distinct regional faunal assemblages, but the fines are essentially uniformly distributed. Two exceptions are a zone of mollusc fragments around Cape Hatteras and a foraminifera zone on a portion of the outer shelf. The average carbonate mineral assemblage consists of 44% low‐Mg calcite, 38% aragonite and 18% high‐Mg calcite. The principal modes of origin of calcareous fines on the Carolina continental margin are probably biological and physical destruction of coarser particles and primary formation in fine size fraction (as in the case of some foraminifera).
EVOLUTION OF ROCK COMPOSITION AND GEOCHEMICAL PROCESSES IN THE SEDIMENTARY SHELL OF THE EARTH*
Authors: RONOV A. B. 
Published: June 2006

ABSTRACTAnalyses of the chemistry of the earth's sedimentary shell (and the crystalline crust) reveal evolutionary trends in sedimentary rock composition, depositional environments, and the intensity and relative importance of geochemical processes. Successive changes in the mode of crustal movement, the intensity of volcanic and intrusive activity, and in the structural plan of continents (reduction of the area of active geosynclines, increase of the area of platforms) caused a regular transformation of the petrographic composition of ancient erosion areas and corresponding changes in the composition of terrigenous material that at different stages was supplied to depositional areas (gradually lower amounts of greywacke, decrease of average Na, Mg, Fe and Al content, inverse development of K and Ca). Sediment‐composition and lithological proportion in the sedimentary shell changed in the course of time: the abundance of volcanogenic rocks decreased, the abundance of carbonates and evaporites increased, the types of prevailing carbonate accumulation changed (siderite→dolomite→calcite), the degree of compositional differentiation of terrigenous sediments increased. These changes were accompanied by regular evolutionary changes in the chemical composition of the most important sedimentary rock types: the lowering of average Na and Fegen contents, the increase of Corg, Ssulf and Spyr concentration, the inverse K development, the increase of the Ca/Mg ratio, the rise of the iron oxidation degree, the displacement of isotope ratios of oxygen and sulfur, etc.A definite trend in the development of the main types of sedimentary geochemical processes is established. The processes of clastogenesis and hydrolysis developed inversely: the importance of the first process decreased, but that of the second increased in the course of time. The intensity of oxidation and precipitation processes also increased through time; chemical precipitation was predominant during the early development stages, and biogenic precipitation predominated during the later stages. Characteristic boundaries in the evolution of sedimentary rock composition and geochemical processes are traced, which correspond to the boundaries A and Pt1, Pt1 and Pt3, Rf3 and V, Pz3 and Mz. Discontinuous variations in the concentrations and ratios of elements in sediments and in the intensity of some geochemical processes are confined to these boundaries. They were determined by changes in the composition of erosion areas, by the increasing importance of platform types of sedimentary processes, by large changes in the biosphere, by the evolution of the atmosphere and ocean composition, and by changes in the types of surface equilibria in the dynamic system: atmosphere‐ocean‐stratisphere.
AUTHIGENIC QUARTZ PRESERVING SKELETAL MATERIAL
Authors: RICHTER DETLEV K. 
Published: June 2006

ABSTRACTAuthigenic quartz crystals formed within skeleton walls frequently contain carbonate inclusions which may characteristically differ from the composition of the skeletons. Whereas the skeletons suffered diagenetic alteration, the inclusions in the quartz crystals were more or less preserved and thus may indicate the original composition of the skeletons, provided the quartz crystals formed not too late in diagenesis. Because they generally grew after the aragonite‐calcite transformation, original aragonite skeletons are characterized by low‐Mg calcite inclusions in the quartz crystals whereas original high‐Mg calcite skeletons differ clearly by the Mg‐content of the inclusions. There is no difference between inclusions within quartz of original low‐Mg calcite and transformed aragonite skeletons, but the former skeletons are well and the latter are poorly preserved.By this method, it is shown that Paleozoic Stromatopora and Actinostroma as well as Triassic Ammonoidea presumably were composed of aragonite, whereas the shells of articulate brachiopods (Stringocephalus, Terebratula, Rhynchonella, Gigantoproductus) were composed of low‐Mg calcite. The skeletons of Crinoidea (Devonian, Muschelkalk, Jurassic) and of Devonian rugose and tabulate corals, however, were composed of high‐Mg calcite.
AN INTERPRETATION AND ANALYSIS OF RECUMBENT‐FOLDED DEFORMED CROSS‐BEDDING
Authors: ALLEN J. R. L. , BANKS N. L. 
Published: June 2006

ABSTRACTThree main kinds of syndepositional deformation are found in cross‐bedded sand‐grade sediments. The first type is characterized by simple recumbent folds of broadly parabolic form. The second is marked by series of folds, with or without overturning. The third type is much more complex, presenting a combination of faulting, folding, and the local destruction of bedding.The type marked by recumbent folds is interpreted as due to the deformation of a liquefied (or perhaps fluidized) sand by current drag following an event in the majority of cases suspected to be an earthquake shock. By reference to empirical and theoretical studies of sedimenting systems, and the behaviour under small shear stresses of liquids of high viscosity, this physical model is developed analytically to yield equations describing the geometry of the deformations in terms of the thickness of the deformed bed, the settling velocity and concentration of particles in the liquefied sand, the viscosity of the liquefied sand, and the magnitude of the deforming force. The equations describe a fold surface that is a portion of a flat‐lying parabola, and show that the proposed circumstances of deformation are plausible in terms of what is known of the real situation. They further reveal that, under the assumptions made in the analysis, the vertical height of the fold hinge above the base of the bed is a function only of the initial shape of the deformed cross‐stratum, the shear rate in the liquefied materials, and the falling velocity and concentration of particles in the liquefied bed. The shapes of deformations calculated from the equations agree well with patterns observed from the geological record.
OBSERVATIONS NOUVELLES SUR LA STRUCTURE DE LA GLAUCONIE EN ACCORDEON (“VERMICULAR PELLETS”); DESCRIPTION DU PROCESSUS DE GENESE DE CES GRANULES PAR NEOFORMATION
Authors: ODIN G. S. 
Published: June 2006

ABSTRACTSince Galliher's studies on the sediments from the Monterey bay (California), vermicular pellets have been considered to be derived from mica flakes by a transformation phenomenon. Generally, it is considered that all the glauconite pellets result from the transformation of degraded smectitic‐ or illitic‐type sheets into more ordered sheets. In the present study, it is shown that the vermicular pellets cannot be derived from the transformation of a mica flake. The mass obtained is several orders higher than the initial mass. Secondly it is noticed that the transformation process invoked do not allow for the continuing existence of the sheets. Finally, the ions of the micaceous sheet are never involved in the “transformation”, for sometimes they are found intact in the vermicular pellet. A study carried out through an electron microscope by reflexion indicates that there is crystal growth between the mica sheets. These sheets are merely a support favourable for glauconite neoformation. If the ions of the mica flake are involved in this genesis to any extent, they yield only a very low quantity of the mass of the final granule. As in the cracks of quartz grains, in feldspar cleavages or in limestone pores, the important surface constituted by the mica sheets is a catalyst for glauconite neoformation.
RAPID FIELD TECHNIQUE USING SPRAY ADHESIVE TO OBTAIN PEELS OF UNCONSOLIDATED SEDIMENT
Authors: YASSO WARREN E. , HARTMAN ELLIOTT M. 
Published: June 2006

ABSTRACTA synthetic rubber base spray adhesive was used to obtain high‐relief, rapidly drying peels of moist unconsolidated beach sand. Samples from vertical planar trench walls and box coring devices were obtained instantaneously and completely hardened in about fifteen additional minutes, with drying times dependent primarily on air temperature. This technique can also be used for preservation of sediment‐core structures in the laboratory.
GEOCHEMICAL HISTORY OF THE CRYSTALLINE BASEMENT AND THE SEDIMENTARY COVER OF THE RUSSIAN AND NORTH AMERICAN PLATFORMS—A DISCUSSION
Authors: SCHWAB FREDERIC L. 
Published: June 2006

ABSTRACTRonov and Migdisov (1971) very effectively document and explain the apparent compositional evolution of the shield and platform rocks of the world in terms of secular changes in source composition, the mode and intensity of weathering (in turn a reflection of secular variations in the composition of the biosphere, atmosphere, and hydrosphere), and compositional differentiation resulting from repetitious episodes of granitization, metamorphism, erosion, and sedimentation. Based on modifications of my own analysis of geosynclinal sediment compositions (Schwab, 1971), I suggest some additional comparisons and interpretations (Fig.1, Table I).
EXEMPLES DE DIAGENÈSE SOUS‐MARINE DANS LES SÈDIMENTS PLIOCÈNES ET PLÉISTOCÈNES: DOLOMITISATION, FERRUGINISATION (MÉDITERRANÉE NORD‐OCCIDENTALE, SUD DE MARSEILLE)
Authors: FROGET CLAUDE 
Published: June 2006

RÉSUMÉL'article présente une étude minéralogique et pétrographique de fragments rocheux pliocènes et pléistocènes recueillis sur le sommet de la pente continentale. Cette étude amène à distinguer trois groupes: Pliocène dolomitisé non ferrugineux, Pléistocène dolomitisé et ferrugineux, Pléistocène ferrugineux non dolomitisé. La diagenèse s'est effectuée en milieu sous‐marin. Les processus de dolomitisation sont discutés. La ferruginisation est rapportée au lessivage de sols riches en fer (limons rouges) élaborés sur le continent lors des périodes interglaciaires. Ces données sont utilisées pour tenter de classer les échantillons dans une chronologie relative.
Clastic sediments associated with radiolarites (Tauglboden—Schichten, Upper Jurassic, Eastern Alps)
Authors: SCHLAGER WOLFGANG , SCHLAGER MAX 
Published: June 2006

ABSTRACTDuring the early Upper Jurassic, widespread deep‐sea radiolarites were deposited in most parts of the Northern Limestone Alps. In the formation described (Tauglboden‐Schichten), these pelagic sediments interfinger with local‐source clastic material. Depending on the topography and the kind of material, either slides and slumps, mudflows, grain flows or turbidity currents operated and formed slump‐folded beds, mud‐flow breccias, fluxoturbidites or turbidites.A breccia had been traced over an area of 20 km2. Its variation is described in terms of lithological columns, bed thicknesses, maximum grain sizes and grain orientations. It forms a tongue‐shaped body, which was probably a part of a submarine fan. The fluxoturbidites of the proximal area grade distally on three sides into turbidites within 3–5 km.The clastic material consists of marls and limestones of Rhaetian and Jurassic age. It was probably derived from a tectonically uplifted palaeo‐high by an interplay of tectonics and gravity. The clastics were deposited on submarine fans bordering this high.In its lithology the formation closely resembles certain marginal facies of flysch troughs.
Markov chain analysis applied to an ancient alluvial plain succession
Authors: MIALL ANDREW D. 
Published: June 2006

ABSTRACTMarkov chain analysis is a comparatively simple statistical technique for the detection of repetitive processes in space or time. Coal measure cyclothems or fluvial fining‐upward cycles are good examples of sedimentary successions laid down under the control of Markovian processes.Analyses of stratigraphic sections commence with a transition count matrix, a two‐dimensional array in which all possible vertical lithologic transitions are tabulated. Various probability matrices may be derived from this raw data, and these are then subjected to chi‐square tests to determine the presence or absence of the Markov property. This technique is applied to four types of stratigraphic succession which occur in the Devonian rocks of Prince of Wales Island, Arctic Canada.(1) A conglomerate succession of alluvial fan origin. Markov analysis is of little or no assistance in the interpretation of these rocks, in which only two principal lithologies are present.(2) A conglomerate‐sandstone succession. Fluvial fining‐upward cycles are detectable by visual examination of the sections and are strongly indicated by Markov analysis.(3) A sandstone‐carbonate succession, of marginal marine origin, and including both marine and non‐marine strata. Cyclicity is weak in these rocks, but analysis suggests that regressions took place much more rapidly than transgressions during their period of deposition.(4) A succession in which the relative proportions of the various lithologies vary markedly with age. The varying nature of the cyclic tendencies is emphasized in this case by dividing the succession into two subintervals, for the purpose of analysis.
Effect of compacton on chemistry of solutions expelled from montmorillonite clay saturated in sea water
Authors: CHILINGARIAN GEORGE V. , SAWABINI C. T. , RIEKE HERMAN H. 
Published: June 2006

ABSTRACTThe total mineralization of solutions squeezed out of montmorillonite clay saturated in sea water was determined at different overburden pressures. The subsequent fractions of expelled solutions were also analysed for various anions (Cl−, SO2‐4, HCO−3, F−) and cations (Na+, K+, Mg2+, Ca2+, B3+).The results indicate that the concentrations of squeezed‐out solutions during the initial stages of compaction (at pressures up to 35 kg/cm2) are slightly higher than that of interstitial solution present initially. The concentration of squeezed‐out solution goes through a maximum, or at least remains constant, before starting to decrease with increasing overburden pressure.