The grey to green bioturbated siltstones interbedded with thin sandstone layers bear lenticular shell beds.

Other parts of the formation contain yellow-green limy shales and grey sandy limestones.

Coquinas often fill gutter casts and included brachiopods, trilobites, bivalves and nautiloids.

The sediments were deposited in an open marine environment.

[1][2][3][4][5] The species Coxiconchia sellaensis was named after the formation.