Sediment in which at least 50 percent of the constituent particles were derived from
erosion, weathering, or mass-wasting of pre-existing earth materials, and transported
to the place of deposition by mechanical agents such as water, wind, ice and gravity.
Choice of 'clastic' is purposful. Other suggested labels for this category include
siliciclastic and terrigineous clastic. Siliciclastic is considered too limiting because
the category includes rocks that consists clasts of carbonate minerals, e.g. epiclastic
detritus eroded from carbonate rock. Terrigineous clastic was considered and rejected
first because it is considered redundant, anything that is terrigineous is clastic.
Second, it is questionable if clastic sediment derived by submarine processes (fragementation
by gravity sliding, faulting, or volcanic activity, with transport by sediment gravity
flow or submarine currents) is terrigineous, but it is clastic and is meant to be
included in this category.