RICHMONDIAN STAGE

division of Ordovician time in North America; the Richmondian is the last stage of the Upper Ordovician Cincinnatian Series of rocks (the Ordovician Period began about 500,000,000 years ago and lasted about 70,000,000 years). In the northeastern regions of the continent, the progressive coarsening of Richmondian sediments as well as the presence of the reddish sediments, as seen in the Queenston and Juniata formations, record a withdrawal of the seas and rising highlands. Limestones are abundant elsewhere.