CONGLOMERATE
Conglomerate is a siliciclastic sedimentary rock consisting of a mix of large &
small grains (it is poorly sorted). The larger grains (pebbles or cobbles
or boulders) in conglomerates are rounded to subrounded in shape. The
finer-grained matrix is usually sand or mud.
Shown below is a quartzose conglomerate, having
rounded quartz pebbles and quartz sand. Some conglomerates are
feldspathic - they have an abundance of K-feldpar pebbles. Some
conglomerates are lithic - they have an abundance of large clasts composed of a
variety of other rock types.
Most conglomerates were deposited in alluvial fan
environments, in many stream/river environments, and in some very shallow
marine environments.
Conglomerate (quartzose conglomerate)