A lithologically (rocky) homogeneous body of strata characterized by certain observable physical features, or by the dominance of a certain rock type or combination of rock types.

Rock-stratigraphic units include groups, formations, members, and beds.

A composite diagram which illustrates in a columnar form which illustrates the subdivisions of the oldest rocks at the bottom showing the geologic times when they existed: There are sequences of stratigraphic columns with their horizontal layers of a given region on the walls of the geology class.

The professor of geology discussed the chronological or vertical arrangement of rock units that were illustrated by their stratigraphic columns during his lecture.