Definition of group

i. The lithostratigraphic unit next in rank above formation, consisting partly or entirely of named formations. A group name combines a geographic name with the term 'group,' and no lithic designation is included; e.g., San Rafael Group.

Ref: AGI

ii. A stratigraphic sequence that will probably be divided in whole or in part into formations in the future.

See Also: analytic group

Ref: AGI

iii. A general term for an assemblage or consecutive sequence of related layers of rock, such as of igneous rocks or of sedimentary beds.

Ref: AGI

iv. A more or less informally recognized succession of strata too thick or inclusive to be considered a formation.

Ref: AGI

v. A number of shots sufficiently close together to be treated in common in respect to preparation for firing.

Ref: BS, 12