formation | Command (military formation) | Elliot Formation | Lance Formation | Crato Formation | Chinle Formation | Two Medicine Formation | Tamayama Formation | Missing Man Formation (band) | Missing Man Formation | Marcellus Formation | Kirkwood Formation | Gettysburg Formation | Clarens Formation | Whitby Mudstone Formation | Tunbridge Wells Sand Formation | Santana Formation | Phalanx formation | phalanx formation | Mahantango Formation | Leduc Formation | Identity formation | Hanson Formation | Formation (stratigraphy) | formation (stratigraphy) | Formation | Centre International de Formation Européenne | Bakken formation | Yixian Formation | Vectis Formation |
When first studied by Leo Lesquereux and John Strong Newberry the Bridge Creek flora was thought to be Miocene age, while Frank Hall Knowlton placed the flora into the Eocene Clarno Formation in 1902.
While collecting fossils with Alonzo W. Hancock in the Clarno Formation of Oregon in 1941, Arnold and Hancock recovered the most complete Miomastodon skull known to date.
While collecting fossils in the Clarno Formation of Oregon during 1941, noted paleobotanists Alonzo W. Hancock and Chester A. Arnold recovered the most complete Zygolophodon skull known at the time.