clast

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Related to clasts: clastic rock, Lithification

clast

[klast]
(geology)
An individual grain, fragment, or constituent of detrital sediment or sedimentary rock produced by physical breakdown of a larger mass.
References in periodicals archive ?
Sandstones in several intervals contain quartz pebbles, up to 3 cm large, and clay clasts, which give evidence of high current velocity.
Strata-bound conglomerates with clasts identical to those in the proximal facies occur locally within the Sam Rowe Ridge and, more rarely, the Ellen Wood Ridge Formation.
In the first type, the sandstone is covered by a thin muddy lamina (up to 1 mm thick), in which tiny clasts are only exceptionally visible (Fig.
The groundmass surrounding the glass clasts and crystal fragments seem to be flushed with organic matter with different sizes and structures showing different degrees of biodegradation and alteration to amorphous organic matter (AOM).
The phreatomagmatic deposits are rich in wall-rock lithoclasts and nonvesicular to weakly vesicular essential clasts.
Iron-rich sandstone clasts are common in the CB/C horizons, and several were observed in the >16mm fraction of the A1 horizon (Fig.
The sediments composed medium tocoarse pebble sized, poorly sorted, mainly ophiolitic clasts composed mainly of serpentine, altered olivine and pyroxenes.
Although it is obvious that continental glaciers carried their clasts and smalls to the south and sea abrasion and accumulation to the north, precise elucidation of their distribution in the Quaternary deposits can be done only by detailed geochemical mapping.
The subjacent Bryantsville Breccia has subaerial laminar crust enclosing micrite tidal clasts.
The age of the Buchans Group is based on Whiterockian conodonts recovered from carbonate clasts (Nowlan and Thurlow 1984, 1987) and U-Pb zircon ages (462 [+ or -] 3 and 465 [+ or -] 3 Ma) from the upper part of the unit (Zagorevski et al.
The equivalent diameter of the porphyric clasts exceeds 20x to 100x the average diameter of the samples.
However, the apparent lack of the dolomite (indicated by low CaO and MgO, Table 1 and analysis of XRD spectra) in the shale clasts precludes their identification as Lower Silurian Estill Shale.