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In Dutch sub-tidal waters, mud settling from suspension can produce a layer with a thickness of only some millimetres in one slack-water period. However, consolidated mud layers of 10–25 mm thickness in sub-tidal deposits are often observed. This indicates that mud may be preserved over several slack-water periods. This is only possible if the critical shear velocity (U∗c) for the initiation of sediment movement is not surpassed after slack water. Tube and flume experiments reveal: (1) Thicker mud layers have smaller initial consolidation rates and lower values of U∗c. (2) A higher sand content of the mud always gives a more rapid initial consolidation. The U∗c-values increase to a maximum which is reached at a sand content of 40%. Higher sand contents lead to decreasing values of U∗c. (3) For one particular mud sample the U∗c-values increase linearly with the mud concentration Of the bed material. (4) After three hours of consolidation a mud layer may carry a sharply bounded sand layer 0.5 cm thick. By application of the results of the experiments to natural conditions in tidal water some tentative explanations are possible of the formation of flaser, lenticular and sand-clay alternating bedding. [ABSTRACT FROM AUTHOR]

Relative mineral frequencies (number or weight) are not suitable to study variations in the absolute frequencies of individual heavy-mineral species in a turbidite. A particular grain size can be selected as the "nominal grain" and numbers of grains of a particular mineral in all size classes can be converted to nominal grains. The total number of nominal grains per gram of sediment sample has been defined as the "nominal grain abundance", which is a function of the volume (or weight) of the total mineral in the sample. Study of a simple, graded, Tertiary turbidite indicates that the least vertical change in heavy-mineral content occurs at, or slightly above, the middle part of the bed. Heavy minerals in the distal part of the turbidite have more uniform vertical distribution than in the proximal part. [ABSTRACT FROM AUTHOR]

A simple method to estimate the degree of ‘crystallinity’ of illite has been used for several years in three French laboratories. Many results, which are unpublished, were obtained; three examples are presented in this paper. They show the sensibility of the method, which allows one to appreciate, above all other methods, burial diagenesis, the front of metamorphism, or some regional areas of very weak metamorphism. [ABSTRACT FROM AUTHOR]

The observed size in the thin-section is less than the true train 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 elastic 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. [ABSTRACT FROM AUTHOR]

Indices based on Wentworth phi values of Q1, Md and Q3 are used for textural classification of sediments. Wentworth phi values enable a detailed subdivision. A nomenclature based on the Wentworth phi indices is developed. The indices, and to a smaller degree the names, show sorting and skewness based on integer phi units. The classification scheme gives a continuous scale from gravel to fine clay. The Q1MdQ3-indices can be used for distinction of river, marine and loess deposits. The addition of indices of the 1st and 99th percentile, giving 5-digit indices, augments the Possibilities for a determination of the environment: river deposits can be distinguished from beach and dune sediments and in more detail from shallow marine and coastal deposits. The indices can be handled by data-processing machines. [ABSTRACT FROM AUTHOR]