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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Despite the many excellent papers on classification of sedimentary rocks, there is still so much loose and variable usage of names that it is not possible to be certain--or, at times, to have even a good notion--of the intended meanings of names found in the literature. If intelligible communication contributes anything to progress in sedimentary petrology, then the existing state of affairs must constitute an appreciable drag on progress. This paper is presented to re-draw
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attention to this lamentable state, to plead for wider employment of clearly defined names, and to offer a general system of nomenclature which could provide a means of achieving greater uniformity and precision in terminology.
This system is not in the least revolutionary but merely proposes restricted meaning for many existing names and a general scheme for systematically deriving other names. Guiding principles are: (1) names should be based on petrographic features; (2) these features should be established, not inferred; (3) the system for naming rocks should be flexible enough to apply both in the field and in the laboratory; and (4) names should be just as quantitative as the means of examination permits.
The classical concept of sedimentary rocks as mixtures of mechanical and chemical fractions is the principal nomenclatural basis in this system. The main name reflects the most abundant constituent of the dominant fraction. A finer division of silicate sandstone than is customarily made is believed practical and desirable.
Three terms are proposed to fill a conspicuous gap in terminology. Aggregal and integral describe textures of mechanical and chemical origin, respectively, but are defined petrographically. Accretic, a correlative term with clastic, describes aggregal textures composed of grains formed by accretion. Integral textures include those which are crystalline and amorphous.
The most important point concerning nomenclature is that the reader understand the terminology employed by the writer. This can be assured by reference to an explicit classification or nomenclatural system.
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