Group (stratigraphy)

[1] Groups are useful for showing relationships between formations, and they are also useful for small-scale mapping or for studying the stratigraphy of large regions.

[2] An example of a group is the Glen Canyon Group, which includes (in ascending order) the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone.

Each of the formations can be distinguished from its neighbor by its lithology, but all were deposited in the same vast erg.

[5] Some well known groups of northwestern Europe have in the past also been used as units for chronostratigraphy and geochronology.

[7] As with other lithostratigraphic ranks, a group must not be defined by fossil taxonomy.