摘要:

ABSTRACTStatistical data computed from analyses of present‐day sediments may be useful for the recognition of ancient environments. Phi‐based measures may be used for the separation of sands. An arithmetic technique is suitable for suites of samples with a considerable range of grain sizes. This paper presents a re‐exploration of arithmetic scales and statistical measures which may facilitate environmental recognition. To test this technique, analyses from approximately 800 samples were used. Quar‐tile and median values were substituted into Trask's arithmetic measures of quartile deviationQDaand skewnessSka. Values ofQDawere plotted against the medianM/dmm on double‐log paper for four environments. On each graph the plots indicate a linear trend and both the positions and slopes of the individual trend curves are different. There is a decrease of gradient of the curves in the sequence: aeolian‐fluviatile‐beach‐ “quiet‐water”. Values ofQDaagainstSkawere plotted similarly, the gradients of the curves decreasing in the reverse sequence. Thus each set of curves (QDavs.Mdmm;QDavs.Ska) establishes a method for comparing and differentiating sediments fr

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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 applic

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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 condense

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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 deforme

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

ABSTRACTSemi‐quantitative clay. mineral analysis was carried out on the clay and silt fractions of approximately three hundred Black Sea core samples. Relative abundance of montmorillonite, illite, kaolinite and chlorite was determined.Illite is the most frequent clay mineral in the Black Sea surface sediments. Highest values are obtained in the northern and central Black Sea. Approaching the Anatolian coast, the illite portion gradually decreases at the expense of montmorillonite. Chlorite and kaolinite occur generally only in small quantities. The lateral changes in the composition of the clay minerals can easily be traced back to the petrology of a northern (rich in illite) and a southern (rich in montmorillonite) distributive area.In almost all cores a periodical fluctuation of the montmorillonite/illite ratio with depth could be observed which may be related to the changing influence of the two distributive provinces during the Holocene and Late Pleistocene (Würm). Higher montmorillonite contents indicate arctic and subarctic climate periods in the northern distributive area during which the illite supply was diminished to a large exte

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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 laminat

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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‐envir

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

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 interpretatio

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Book reviewed in this article:Petroleum Economics and Offshore Mining Legislation.A. P. H. VAN Meurs.Sedimentografia‐Atlante fotografico delle Strutture Primarie dei Sedimenti.FrancoRicciLucchi.Le Dolomiti. Geologia dei Monti tra Isarco e Piave.P. Leonardi.Sedimente und Sedimentgesteine (Sediments and Sedimentary Rocks).H. Fücht‐bauerand GermanMüller.Geochronology of Phanerozoic Orogenic Belts—Eclogae Geol. Helv., 63(1). E. Jäger, M. Grünenfelderand R. Herb(Editors).Physical Processes of Sedimentation.J. R. L. Allen.African Magmatism and Tectonics.T. N. Cliffordand I. G. Gass(Editors).Les Formations sèdimentaires tertiaires et quaternaires de la Cuvette tchadienne et les Sols qui en dèrivent (Mèm. O.R.S.T.O.M., 43). J. Pias.Flysch Sedimentology in Northern America.J. Lajoie(Editor).Development of the Northern Apennines Geosyncline.G. Sestini(Editor).Ancient Sedimentary Environments.richardC.selley.Introductory Petrography of Fossils.A S.horowitzan

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1972.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY