Definition of post-Tertiary in US English:

post-Tertiary

adjective

Geology Physical Geography
  • Of, relating to, or designating the post-Tertiary; formed or occurring subsequent to the Tertiary period.

Origin

Mid 19th century (in an earlier sense). From post- + tertiary.

Pronunciation

post-Tertiary

/ˌpəʊs(t)ˈtəːʃ(ə)ri/