a. Geol. [f. Tongres, in Belgium, where developed + -IAN.] Name for marine strata of the Lower Oligocene of Belgium.
1883. [see RUPELIAN].
1885. Geikie, Text-bk. Geol. (ed. 2), 864. The Tongrian deposits contain an abundant marine fauna = the Egeln beds of Germany.
1885. Lyell, Elem. Geol., xv. 202. The lower division [of the Oligocene], or Tongrian, includes the sands in the neighbourhood of Tongres, and … corresponds with the upper part of the Gypseous series of Montmartre, and with the Headon series of England.
