Upper Carboniferous period vs Upper Carboniferous

Upper Carboniferous period and Upper Carboniferous both are nouns.

Word	Noun	Adjective	Verb	Adverb
Upper Carboniferous period	Yes	No	No	No
Upper Carboniferous	Yes	No	No	No

As nouns, Upper Carboniferous period and Upper Carboniferous are synonyms defined as:

Upper Carboniferous period and Upper Carboniferous: the period from 310 million to 280 million years ago; characterized by warm climate and swampy land

Other synonyms of Upper Carboniferous period include Pennsylvanian, Pennsylvanian period.

Upper Carboniferous period (noun)	Upper Carboniferous (noun)
the period from 310 million to 280 million years ago; characterized by warm climate and swampy land	the period from 310 million to 280 million years ago; characterized by warm climate and swampy land