MENDOCIAN STAGE

lowermost and oldest major division of Lower Cretaceous rocks and time in Chile and Argentina (the Cretaceous Period began about 136,000,000 years ago and lasted about 71,000,000 years). It consists of about 300 metres (1,000 feet) of marine black shales and dark limestones that are rich in the remains of ammonite cephalopods (mollusks). To the east, thick shell beds represent the Mendocian Stage. The Mendocian Stage underlies the Huitrinian Stage.