A new model for the evolution of the volcanic island of Réunion (Indian Ocean)

Abstract

The island of Réunion has been studied using data from airborne and shipborne magnetic surveys. The subaerial history of Réunion spans the last 2.1 million years. The Brunhes‐Matuyama geomagnetic reversal enables differentiation of volcanic rocks older and younger than 0.78 Ma. The lower submarine flanks are poorly magnetized and are interpreted as landslide deposits. The core of the island is composed of highly magnetized rocks. Piton des Neiges volcano is composed mostly of rocks older than 0.78 Ma. Only its western flank and central area include thick piles of younger rocks. Piton de la Fournaise is a highly and normally magnetized edifice, but its northern and eastern flanks are underlain at shallow depth by reversely magnetized formations. The latter are regarded as remnants of Les Alizés volcano, associated with the Grand‐Brûlé hypovolcanic complex. At the Matuyama‐Brunhes transition the island was composed of at least two main volcanoes (Piton des Neiges and Les Alizés) and perhaps also of a third old volcano (Takamaka) at the center‐north of the island. Piton de la Fournaise grows on the flank of Les Alizés and is a relatively young focus of volcanism. These volcanoes have had successive phases of construction and destruction. The analysis of magnetic anomalies over Réunion was decisive in defining a new coherent model for the evolution of the island.