 Oolites and fossils of reefal organisms (mainly corals) are common in places.This region is affected by the spectacular karst features known as "tsingy" and for this reason most of the area is part of the Tsingy de Bemaraha National Park, included in the UNESCO World Heritage Sites list.The facies in the eastern belt is made up mainly of fine-grained and well-bedded limestones with the average thickness of the individual beds being a few tens of centimeters.