Sierra Madre Formation (original) (raw)

The Sierra Madre Formation is a geologic formation in Chiapas state, southern Mexico. It consists of marine dolomites and limestones. The formation dates to the Middle Cretaceous, spanning from the Aptian of the Early to the Cenomanian of the Late Cretaceous. The dolomites, dolomitic breccias and limestones of the formation have been deposited in a lagoonal to estuarine environment and contain many fossil fish, flora and rudists, typical reef-building organisms of the Cretaceous.