| Ada Formation | |
| Type: | Formation |
| Age: | Late Pennsylvanian |
| Namedfor: | Ada, Pontotoc Co, OK |
| Region: | Oklahoma |
| Country: | United States |
The Ada Formation is a geologic formation in Oklahoma, within and to west of Ada.[1] It consist mainly of shale with numerous limestone layers which get thinner and eventually disappear to the south, where they are replaced by fine-grained sandstone. Fossils are rare.[2] Disarticulated remains of Eryops, Diasparactus, and Ophiacodon from the Ada Formation represent the first finds of these genera in Oklahoma.[3]