Imbrian System

Imbrian System

(im -bree-ăn) One of the stratigraphic systems of the Moon, defined by the deposits of the Imbrium Basin and covering the period from about 3.85 to 3.15 billion (109) years ago. It includes the Orientale Basin, most visible mare deposits, and many large craters. See also Copernican System; Nectarian System.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006