Alternative form of オルドビス紀 (Orudobisu-ki, “Ordovician”)

geology

one thing

geological features

age, era, period (of time) / the times, spirit of the age / antiquity / a time in one's life, one's days (in college etc.)

scholarship; learning; knowledge

a target, a mark, a bullseye / an objective, an object (of doing something)

as far as ... is concerned; in terms of ...

narrative; account

rule; regulation / age; era; period / to record; to write down