German geologist and paleontologist, who was one of the most important early stratigraphers (stratigraphy). Oppel was a professor at Munich from 1861. In studying the Swabian Jura he discovered that paleontologic and lithologic zones need not be identical or even mutually dependent. His use of ammonite fossils in dating Jurassic (Jurassic Period) rocks (146,000,000 to 200,000,000 years old) was adopted by other scientists.