phenoclasts

phenoclasts

[′fen·ə‚klasts]
(petrology)
The larger, conspicuous fragments in a sediment or sedimentary rock, such as cobbles in a conglomerate.
References in periodicals archive ?
1999), where thick units (10s m) of pyroclastic material with large quartz and feldspar phenoclasts (up 10 cm in length) are preserved.
Considering the lack of marginal quenching and flow foliation, as well as the rheology of the phenocryst-rich siliceous magma (discussed below), it is probable that exsolved gases from the magma (fluidization) enhanced dyke emplacement (Clarke 1992); fluidization is consistent with the angular to subrounded nature of xenoliths and the rounding and fragmentation of phenocrysts that are now best described as phenoclasts.
By further contrast, on the "lower" Tetagouche River near Vallee Lourdes about 9 km east-northeast downstream of the Little Falls locality, the Vallee Lourdes conglomerate, interpreted to be a debris flow (Rice and van Staal 1992), contains a few large rounded, Mesoproterozoic, unfoliated and foliated granodiorite clasts as much as a metre in diameter and abundant quartz phenoclasts derived from felsic volcanic rocks (van Staal et al.