#stratigraphy definition
- Autunian — A transitional geological stage located at the base of the Lower Permian (or late Upper Carboniferous), defined by successions of oil shales rich in fossil flora (Callipteris conferta) historically researched in the basin of Autun, France; as an adjective, it refers to the formations, rocks, or fauna specific to this time interval.
- Auversian — A regional subdivision or transitional geological stage of the Middle Eocene within the Paleogene period, defined by the fossiliferous sand deposits researched in Auvers-sur-Oise, Paris Basin (France); as an adjective, it denotes the sedimentary formations or marine fauna characteristic of this epoch.