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