a. Geol. [ad. F. Urgonien (D’Orbigny, 1852), f. Orgon (see def.).] Forming or belonging to a series of massive limestones of the Lower Cretaceous system as developed at Orgon in the Durance valley.
1856. Quart. Jrnl. Geol. Soc., XII. 69. M. d’Orbigny’s Urgonian series, or upper division of the Neocomian group.
1888. Dawson, Geol. Hist. Plants, 282. These beds are regarded as Lower Cretaceous (Urgonian).
