bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURES OF DUNES AT WHITE SANDS NATIONAL MONUMENT, NEW MEXICO (AND A COMPARISON WITH STRUCTURES OF DUNES FROM OTHER SELECTED AREAS)1
Authors: McKEE EDWIN D.
Published: June 2006

The type, scale, and relative abundance of sedimentary structures in four kinds of dunes at White Sands National Monument, New Mexico, were determined by examination of vertical sections on walls of trenches cut through the dunes both in a windward direction and at right angles to this direction. Analysis of cross‐stratification in all dunes examined indicated certain common features: sets of cross‐strata mostly are medium‐ to large‐scale; nearly all laminae dip downwind at high angles (not uncommonly at 30°‐34°); most bounding surfaces between sets of cross‐strata are nearly horizontal on the upwind side, but have progressively steeper dips to lee, downwind; and individual sets of cross‐strata tend to be thinner and the laminae flatter near the top than at the bottom of a dune in vertical section.

Sparse but distinctive structural features that are characteristic of the four types of dunes are varieties of contorted bedding, rare ripple laminae, and either local scour‐and‐fill bedding, or festoon bedding. Other structures, apparently limited to either one or two types of dunes, are the concave‐downward foresets in some parabolic dunes; the low‐angle reverse dips of upwind strata on high transverse dunes; and the almost horizontal laminae which represent apparent dip in sections normal to wind direction in dome‐shaped and transverse dunes.

Describing cross‐stratification in terms of three dimensions, dune structure at White Sands consists dominantly of the tabular planar sets, with units thickest near the dune base, thinner above. To a lesser extent the sets are of simple (non‐erosion) tabular form and relatively uncommonly, of the trough type. Wedge planar forms are scarce. The planar forms characteristically are of two classes in nearly equal proportions: those in which bounding surfaces are virtually horizontal and those in which they dip at moderate to high degree.

A brief comparison is made between the structures of dunes that are characteristic of one effective wind direction, as at White Sands, and certain others formed by winds of two or more directions. Seif dunes of Libya, reversing dunes of the San Luis Valley, Colorado, and star dunes in Saudi Arabia are discussed as examples of complex dunes formed by multi‐directional winds.
AIR AND SAND MOVEMENTS TO THE LEE OF DUNES1
Authors: HOYT JOHN H.
Published: June 2006

The large and extensive transverse and barchane dunes of coastal South West Africa are strongly oriented under the influence of predominantly southerly winds. During periods of strong winds (40–50 miles/h) deposition occurs on the lee slope in three ways: (1) sand is blown over the crest of the dune and falls on the lee slope; (2) rapid deposition near the dune crest results in periodic slumps and slides down the lee slope; (3) eddy currents developed to the lee of the dune pick up sand from the surface downwind from the dune and transport it to the lee slope.

The size and strength of the lee eddy is surprising. With winds in the 40–50 miles/h range frequent gusts lift fine sand from the downwind surface to a height of several feet. Less frequently sand is picked up from a low position on the lee slope and redeposited higher on the slope. The addition of material to the lee slope by the eddy is much less volumetrically than the contribution directly over the dune crest from the windward direction; however, with strong winds the removal and transportation of sand from the area downwind of the lee slope back to the lee slope appears to be important in the deflation of this surface. The width of the area influenced by the lee eddy during strong winds is about equal to the height of the dune.

Observations in low dunes from 1 to 20 ft. high at Sapelo Island, Ga., U.S.A., confirm the presence of a well developed eddy to the lee of these dunes during strong and moderate winds (20–50 miles/h).
AN UNUSUAL SEDIMENTARY STRUCTURE INDICATIVE OF SHALLOW WATER CONDITIONS IN THE GRÈS ARMORICAIN OF FINISTÈRE (FRANCE)
Authors: BRADSHAW J. D.
Published: June 2006

The communication describes dome‐like masses of sand apparently developed by gully erosion on the upper surfaces of Ordovician sandstones. The similarity of these structures to the minor topography of tidal marshes is noted, and it is suggested that similar processes may be responsible.
SEDIMENT SIZE DISTRIBUTION PROFILE ON THE CONTINENTAL SHELF OFF NEW JERSEY1
Authors: DONAHUE JESSIE G. , ALLEN ROBERT C. , HEEZEN BRUCE C.
Published: June 2006

A series of samples from the continental shelf off New Jersey reveals a continuous surface layer of fine sand overlying a variety of sediment type. Ripples and shell debris suggest the fine sand is reworked and is in adjustment with the present shelf environment.
THE ANGLE OF REPOSE FOR A SINGLE GRAIN ON A FIXED ROUGH BED
Authors: MILLER ROBERT L. , BYRNE ROBERT J.
Published: June 2006

The angle of repose under water is experimentally determined for a single particle on a fixed rough bed.

The effect of grain shape, size and sorting of the bed and ratio of particle diameter to average bed grain diameter are taken into account. An empirical equation is given for predicting angle of repose as a function of the above factors. The accuracy of fit of this equation is quite good. Several other conclusions drawn for the case of a single grain on a fixed rough bed are:

Angle of repose increases with decrease in size, departure from sphericity and increased angularity.

Angle of repose increase with decrease in sorting.

A single angle of repose for sand size grains is not valid. Variation ranges from nearly 90° to less than 20°, depending on the values of the factors given above.
THE STUDY OF ARENACEOUS SEDIMENTS BY MEANS OF ACETATE REPLICAS
Authors: BJØRLYKKE KNUT
Published: June 2006

The present paper describes the use of cellulose acetate replicas in the study of silicate rocks, particularly indurated sandstones. The procedure of Boardman and Utgaard (1964) for the reproduction of surface structures of polished limestone slabs for the study of Paleozoic Bryozoa, was modified and applied on silicate rocks using HF instead of formic acid as the etching agent.

The polished slabs are etched with 40 % HF for 5–10 seconds and then washed, dried, wetted with acetone and gently pressed towards a mount of cellulose acetate. After drying, the specimen is quickly removed and an imprint is left on the acetate peel. By using thick (1.6 mm) cellulose acetate sheets no mounting on glass slides is needed, and the replica can be studied directly under the microscope or be used as a photographic negative.
THE PRESENTATION OF SUBJECTIVE SHAPE AND ROUNDNESS DATA
Authors: SMALLEY I. J.
Published: June 2006

If a modified version of the Zingg system is used particles can be subjectively classified into four shape classes. The roundness of a particle can be estimated by assessing the flat/convex/concave ratio and can then be represented as a point on a triangular net; this point can also indicate the Zingg class of the particle.
COMPARATIVE STUDY OF DEVIATION INDEX Hqa, Qd AND So
Authors: POMEROL CHARLES
Published: June 2006

The deviation index Hqa is studied by use of the A.F.N.O.R. set of sieves (the geometrical progression of mesh‐size has a ratio 1010 # 1.259). The author shows the connection between Hqa and the sorting index (So) of Trask, and the connection between Hqa and the Qdφ index of Krumbein (Hq= 3 Qdφ, approximately).
EVOLUTION OF ZIRCONS IN SEDIMENTARY AND METAMORPHIC ROCKS: A DISCUSSION
Authors: KALSBEEK F.
Published: June 2006

Saxena'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

The 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

For 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

The 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

Electronic 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.
THE APPLICATION OF INFRA‐RED ABSORPTION SPECTROSCOPY TO CARBONATE MINERALOGY
Authors: CHESTER R. , ELDERFIELD H.
Published: June 2006

The data given in the literature for the infra‐red identification of carbonate minerals is summarised, and a technique is described which may be used to identify magnesite, smithsonite, dolomite, rhodochrosite, calcite, aragonite, strontianite, cerussite and witherite by means of their infra‐red absorption bands. Two quantitative applications of the use of infra‐red spectroscopy are considered and techniques are outlined for the determination of calcite‐dolomite ratios in carbonate rocks, and calcite‐aragonite ratios in shell material.
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

This 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

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

The 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

From 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

Modern 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

An 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

Devonian 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

SUMMARY

Study 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

SUMMARY

The 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

The 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

Late 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

Extensive 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

Diagenesis, 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

Two 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

The 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

The 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

The 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

The 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.
TURBIDITES OF THE NORTHEAST PACIFIC1
Authors: HORN D. R. , EWING M. , DELACH M. N. , HORN B. M.
Published: June 2006

The northeast corner of the Pacific Ocean is a region of turbidity‐current activity. Cores from this area are dominated by very fine‐grained sand and medium‐grained silt that grade upward to clay. The results presented in this article are based on 217 textural analyses of turbidite layers comprising 30 piston cores.

It is possible to distinguish proximal and distal facies of turbidites using characteristics of layering, grading and texture. Features of the proximal facies include wide range of layer thickness, maximum layer thickness, non‐grading, truncation of grading, textural reversals, and sand at the base of graded layers. Areas beyond main routes of submarine flows are sites of episodic addition of silt‐through clay‐sized sediment. The proportion, thickness, and mean grain size of the silt decreases with increasing distance from the main avenues of flow.
NUMERICAL ESTIMATES OF ANCIENT WAVES, WATER DEPTH AND FETCH
Authors: TANNER WILLIAM F.
Published: June 2006

A series of carefully controlled marine experiments, in which sand of known grain diameter and essentially perfect sorting was exposed to waves of various sizes, was supplemented by study of lakes of various widths (and hence differing values for fetch), in an effort to obtain relationships between parameters measurable in sedimentary rocks (i.e., ripple‐mark spacing) and paleogeo‐graphic information (water depth, wave height, wave length, and fetch). The results were subjected to regression analysis.

Two equations were obtained, relating ripple‐mark spacing to grain size, water wavelength and water depth, with predictive abilities higher than 80%. Two equations were obtained, relating ripple‐mark spacing to grain size, water wave‐height and water depth, with a predictive ability of 75%‐80%. Two useful equations involved water wave‐length, and two involved water wave‐height; in general those based on water wave‐length were superior to those based on water wave‐height.

In shallow‐water work, the pairs of values which can be obtained from equations included in this paper are highly limited in range, and thus define the paleogeographic unknowns reasonably closely. These pairs (or single values, as may be appropriate) can be inserted into three additional equations, which relate fetch to various wave parameters.

An application is made to Jurassic rocks (lower Morrison sandstones) in northern New Mexico, which are interpreted as deposits of a large, shallow lake. Shorelines, where they cannot be located by inspection of the rocks, can be inferred fairly closely from the fetch data.
AN APPLICATION OF REFLECTED‐LIGHT DIFFERENTIAL‐INTERFERENCE MICROSCOPY: BEACH STUDIES IN EASTERN LONG ISLAND (U.S.A.)
Authors: WARNKE DETLEF A. , STAUBLE DONALD K.
Published: June 2006

A significant recent advance in microscopy has been the introduction of differential‐interference contrast (DIC) optics. In reflected‐light instruments, one “Nomarski prism” (a modified Wollaston prism) is used both for beam splitting and combining. In effect, two deformed wave‐fronts are produced which are laterally separated by a distance below the resolving power of the microscope. They are brought to differential interference by the analyzer, the effect being one of oblique illumination of the object.

This system can be used in the study of mineral‐grain surfaces. For this purpose, conventional replicas of the grains are placed on petrographic slides which in turn are placed over a silvered mirror on the microscope stage. The Nomarski prism is then adjusted until the best contrast is achieved.

For a test study, samples were collected from the intertidal zone of the Atlantic shore of eastern Long Island, mostly at localities which earlier were sampled by Krinsley et al. (1964) and studied in a classical investigation of quartz‐grain surface features by transmission electron microscopy. In the present study, a semi‐quantitative evaluation of surface features was attempted, using as guide the criteria set up by Krinsley and his school. The results of this study are tentatively interpreted as reflecting pronounced erosion in the study area, and increasing energy levels from East Hampton to Montauk Point.
VOLCANIC QUARTZ AS INDICATOR MINERAL IN GRAYWACKES
Authors: REIMER THOMAS O.
Published: June 2006

Samples from an uninterrupted sequence of Early Precambrian graywackes were investigated in order to disclose whether the amount of “volcanic” quartz, i.e., quartz without undulatory extinction, can give indications of quantitative changes in the composition of the source area. As non‐undulatory quartz usually is enriched in the smaller‐size fractions, only grains with an above average grain size were considered. The minimum grain size was fixed at 0.1 mm. In each thin section 100 grains were counted and separated into two groups, one without and one with undulatory extinction. Their relation to each other was then determined and plotted in a stratigraphic column. In the same column the relation of porphyry and tuff fragments to lava fragments was plotted. The resulting similarity of the two curves shows that the quartz ratio, as introduced here, can give indications about changes in the source area of graywackes.
COMPARISON OF SIEVING AND SETTLING TECHNIQUES FOR SIZE ANALYSIS, USING A BENTHOS RAPID SEDIMENT ANALYZER
Authors: SANFORD ROBERT B. , SWIFT DONALD J. P.
Published: June 2006

Grain‐size distributions of sand samples by means of a Benthos Rapid Sediment Analyzer were determined, using SCHLEE'S (1966) fall times. The results were compared with analysis of the same samples by sieving. The Rapid Sediment Analyzer (RSA) consistently overestimated the mean diameter of fine samples and underestimated the diameter of coarse samples relative to sieving. Since we used a wider settling column and a smaller sample weight than did Schlee, we infer that the differences were due to weaker grain interaction effects in our analyzer. Thus, by using Schlee's fall times, we overcompensated for these effects. We conclude that the “new grain parameter” of fall velocity (SENGUPTA and VEENSTRA, 1968) is indeed valuable. MIDDLETON'S (1967) psi transform is more convenient than the analogous phi transform in that it yields Middle‐ton sand classes of 0 to 5 psi, as compared to Wentworth‐Krumbein sand classes of ‐1 to 4 phi. However, use of fall velocity does not completely obviate the need to determine grain diameter, since this is the most expedient criterion with which to correct fall velocity to standard fall velocity.
AEOLIAN BEDFORMS—THEIR DEVELOPMENT AND ORIGINS
Authors: WILSON IAN G.
Published: June 2006

Bedforms are defined and their variety outlined. Aeolian bedforms are shown to arise spontaneously by a two‐way interaction between surface form and airflow involving piecemeal material transfer between them. They eventually reach a dynamic equilibrium and transverse elements migrate downwind.

Aeolian bedforms may be compounded of elements from four groups i.e., draas, dunes, aerodynamic ripples and impact ripples, each subdivided into transverse and longitudinal elements. There are no transitional forms between the elements of one of these eight subgroups and those of another and they are interpreted as being formed by different mechanisms. The possible nature of these mechanisms is considered and qualitative models for the development of generalised transverse and longitudinal elements given. Transverse and longitudinal elements may be combined in three different ways according to whether or not one element is displaced half a wavelength on crossing the other.
FEATURES OF THICK‐BEDDED SANDSTONES IN A PROXIMAL FLYSCH SEQUENCE, UPPER CAMBRIAN, SOUTHWEST TASMANIA
Authors: CORBETT K. D.
Published: June 2006

The Upper Cambrian Singing Creek Formation, southwest Tasmania, includes a number of thick‐bedded, generally non‐graded or poorly graded sandstones as well as normal graded sandstones (turbidites), laminated siltstones, conglomerates, and numerous slump sheets. Most of the thick beds occur in composite units up to 30 m or so thick, within which there is interfingering and inter‐grading with thinner sandstones, and frequent amalgamation of beds. The composite units are separated by siltstone sequences, and in some cases at least appear to be large lenses. They are interpreted as being mainly channel deposits in a submarine fan complex.

Many of the thick beds are either structureless throughout or have only a thin division of flat lamination (with parting lineation) near the top, followed in some cases by ripple mark. Some beds, however, show unusual wavy lamination or “dish structure” beneath the flat lamination, and this in turn may be underlain by contorted lamination. Narrow vein‐like de‐watering channels (elutriation columns) occur in the wavy‐laminated division of some beds.

The thick beds form a gradational series with the normal graded beds, and apparently represent the over‐thickened basal parts of such beds, i.e., they are lateral variants of the normal turbidites. Similar beds called “grain‐flow deposits” by Stauffer (1967) also appear to be proximal turbidites. The origin of the wavy lamination and dish structure is problematical but could be related to mass shearing and dewatering during consolidation in the manner observed by Middleton (1967) for experimental high‐concentration underflows.
ARAGONITIC OOIDS1: EXPERIMENTAL PRECIPITATION FROM SEAWATER IN THE PRESENCE OF HUMIC ACID2.
Authors: SUESS ERWIN , FÜTTERER DIETER
Published: June 2006

Humic acid dissolved in artificial seawater influenced the morphology, internal structure, and composition of aragonite when precipitation was induced with dilute Na2CO3 solution. At sodium humate concentrations of around 20 mg/1, numerous brownish spherical aragonite bodies developed within one day at 25 °C. The spheres ranged in size from 10–100 microns and resembled natural marine ooids. They formed with gentle agitation of the solution as well as with no water movement at all. The typical structure of natural ooids consisting of concentric alternating aragonite and organic laminae was experimentally duplicated as layers of aragonite crystals alternating with humate membranes; however, in contrast to natural ooids, the individual aragonite crystals here were oriented radially with their c‐axes. The aragonite of the spheres contained about 20 wt. % more strontium than the aragonite precipitated experimentally without the addition of sodium humate, and organic carbon content of the spherical aragonite was about 7% by weight.
An appraisal of the computation of statistical parameters in grain size analysis
Authors: SEWARD‐THOMPSON B. L. , HAILS J. R.
Published: June 2006

A computer program has been written to overcome the limitations of two published programs that compute statistical parameters in grain size analysis. This program uses all available data, obtained from standard sedimentological analyses, regardless of phi interval, and computes statistical parameters by direct integration of a linear approximation to the cumulative curve. This has the advantage that the distribution curve is known and hence the limitations of the parameters obtained can be assessed. Furthermore, it is argued, with examples, that this approximation introduces no greater degree of inaccuracy than is already present in standard sampling and analytical procedures.
Clay mineralogy of Triassic sediments in southern Israel and Sinai
Authors: HELLER‐KALLAI L. , NATHAN Y. , ZAK I.
Published: June 2006

The clay mineral composition of Triassic sediments in the Negev and Sinai depends upon the environment of deposition. Kaolinite predominates in continental and epicontinental sediments. The mineralogical composition of the marine clays resembles that of corresponding samples from North Africa and Europe, which comprise various mixtures and interstratifications of illite, montmorillonite, vermiculite and chlorite. Evaporitic sediments are poor in clay minerals and those present are largely detrital.

The results presented suggest that chlorite was formed diagenetically by prolonged percolation of seawater through pervious layers overlying impervious ones (hard beds).
Incorporation of uranium in modern corals
Authors: AMIEL ABRAHAM J. , MILLER DONALD S. , FRIEDMAN GERALD M.
Published: June 2006

Uranium occurs in corals at three sites: 1, in organic matter; 2, adsorbed on the surfaces of skeletal aragonite; and 3, in the aragonite lattice. Organic matter incorporates from sea water by chelation 40–70 ppm uranium; skeletal aragonite incorporates only 3 ppm. However, as the organic fraction is low (0·1%), its high concentration of uranium does not significantly affect the total concentration of uranium in the coral. A negligible concentration of uranium, 40–60 ppb, is adsorbed on skeletal aragonite from which it is readily leached or exchanged. This low concentration of adsorbed uranium (<2% of the total uranium in skeletal aragonite) is related to the very small specific surface area (1·5–1·8 m2/g of the corals.
Diagenetic development of a Precambrian limestone as interpreted from a modern analogue
Authors: MÜLLER GERMAN , SCHÖLL WALTER U. , TIETZ GERD
Published: June 2006

A strong correlation in the geometry and mineralogy of two cement generations of a Quaternary with a Precambrian calcarenite enables us to reconstruct the diagenetic history of the Precambrian limestone. Both calcarenites contain two cement generations (A and B) of which A consists of dolomite, B of calcite.

The following diagenetic stages can be recognized: after deposition of the allochems in a shallow marine environment, cementation in the intertidal zone with magnesian calcite (cement A) led to the formation of beachrock (Stage 1).

By lowering of the sea level, the beach rock was shifted into the supratidal zone, but still remained under the predominant influence of the sea water (breakers, spray). During longer periods of aridity, the magnesian calcite of cement A and of the allochems was transformed into dolomite by brines derived from sea water with very high Mg/Ca ratio (> 15), whereas aragonite and calcite remained unaffected.

After further lowering of the sea, an increasing influence of meteoric water caused the wet transformation of aragonitic allochems to sparry calcite and to the precipitation of sparry calcitic cement B.
Phase differences between bed configuration and flow in natural environments, and their geological relevance
Authors: ALLEN J. R. L.
Published: June 2006

In nature where unsteady flows prevail, the characters of bed configurations lag, or differ in phase from, the flow conditions. This is demonstrated from quantitative data for dune beds in the Fraser River (Canada) and the Gironde Estuary (France), where the flow conditions change ahead of the bed form by as much as 1/4 period. Qualitative evidence for lag abounds, for instance, substantially unmodified dunes exposed during low water.

The existence of lag appears to confuse attempts to establish from field data the relationships between bed‐form properties and flow conditions and, at the same time, makes difficult the confident application to field situations of formulae based on steady‐state experiments or theories. Unfamiliar types of field study and experiments are needed to increase understanding of the degree and precise significance of lag.