Page 18 - Volcanic Textures A Guide To The Interpretation of Textures In Volcanic Rocks

The problem of in-built genetic interpretation is more deposits. Nevertheless, the borrowed terms are the best
serious for naming deposits with volcaniclastic textures. currently available and will remain so, until the
There is no terminology that applies generally to all nomenclature problem is solved by agreement among
volcaniclastic deposits without genetic implications. volcanologists and sedimentologists. Out of necessity,
Relatively non-genetic terms have been borrowed from the borrowed terms are used in the scheme for building
sedimentology (Fisher, 1961) (Table 2) and, for that descriptive names for volcaniclastic deposits (Table 2).
reason, are far from satisfactory. In other contexts, these For these deposits, genetic interpretation seeks to
terms are used for epiclastic deposits, and in volcanic discriminate between four main categories that are
terranes, only some of the volcaniclastic deposits have based on fragmentation and transport processes ─
that origin. Furthermore, if these terms are used in a autoclastic, pyroclastic, resedimented syn-eruptive
general descriptive sense, they are no longer effective as volcaniclastic, and volcanogenic sedimentary (epiclastic
terms specifically for volcanogenic sedimentary volcanic). In each case, there are finer scale genetic

Fig. 4 Characteristics of resedimented syn-eruptive volcaniclastic deposits (Part 4).

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