GRAIN‐SIZE INDICES, CLASSIFICATION AND ENVIRONMENT

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Abstract
SUMMARY: 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.
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