Page 157 - Volcanic Textures A Guide To The Interpretation of Textures In Volcanic Rocks

B. The basal contact (C) of the coarse, polymict
volcaniclastic lithic breccia truncates bedding (S 0) in
underlying cream, medium bedded sandstone (St).
The coarse lithic breccia consists of angular to
subangular, feldspar-phyric volcanic lithic fragments,
dark grey mudstone clasts (M) up to 11 m in length,
and a sparse matrix of crystal and pumice fragments.
Some mudstone clasts are blocky but others have
irregular shapes suggesting that they are intraclasts
which were not fully lithified at the time of
incorporation into the breccia.

Mount Read Volcanics, Cambrian; Hall Rivulet
Canal, western Tasmania.
C. Clasts in the polymict volcaniclastic lithic breccia
(31.28) are very closely packed. The dominant clast
type is pale, angular, feldspar-phyric silicic lava (V).
Dark grey, irregular mudstone intraclasts (M) are
also evident.

Mount Read Volcanics, Cambrian; Hall Rivulet
Canal, western Tasmania.

Plate 32 — Submarine, lithic-rich, volcaniclastic mass-flow deposits

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