1856, in geology, "pertaining to the Tertiary period between the Eocene and the Miocene," now defined roughly as 34 million to 23 million years before the present, coined in German (1854) by paleontologist Heinrich Ernst von Beyrich (1815-1896), from oligo- "small, little, few" + -cene. So called because few modern fossils were found in Oligocene rocks, which were especially prominent in northern Germany.
