BIOSTRATIGRAPHY OF MAASTRICHTIAN BENTHIC FORAMINIFERA FROM THE BERIVOTRA SECTOR (MAHAJANGA BASSIN),MADAGASCAR

Earth Sciences

The physico-chemical analysis carried out in this work constitutes an important study of the marly sediments of the Maastrichtian. It is based on the analysis of 45 samples taken from the Berivotra sector (Miadana, Anembalemba and Berivotra) in the Mahajanga Basin. The area is very rich in macro and micro fossils. The present study considers the assembly of benthic foraminifera. The base of the outcrop is characterized by a small quantity of microfossils (Bolivinoides draco, Ammobaculites luckei, Textularia faujasi). The middle part constitutes a very fossiliferous benthic-pelagic zone (Marssonella oxycona, Lagena hispida, Glandulina parallela, Gavelinopsis acuta). The summit is represented by large foraminifera (Siderolites calcitrapoides, Laffiteina mengaudi). The Maastrichtian biostratigraphy of the Berivotra sector is represented by three biozonations from bottom to top: (Bolivinoides draco biozone, Gavelinella danica biozone and Siderolites calcitrapoides biozone). The Maastrichtian of the Mahajanga Basin seems quite homogeneous, with an association that evokes a marine environment with normal salinity and optimal temperature with warm influence. It indicates an external platform environment and the neritic zone, which is to say between the platform and the flexure of the continental slope (150m to 200m).

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