We don't have synonyms for volgian yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are vosgian.
(n) :
(geology) An obsolete regionally defined geological unit in Russia, in part Jurassic and in part Cretaceous, corresponding to the Tithonian and part of the Berriasian, and perhaps even part of the Kimmeridgian.
(n) :
(geology) An obsolete regionally defined geological unit in Russia, in part Jurassic and in part Cretaceous, corresponding to the Tithonian and part of the Berriasian, and perhaps even part of the Kimmeridgian.