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

The island of Reunion has been studied using data from airborne and shipbor ne magnetic surveys. The subaerial history of Reunion spans the last 2.1 mi llion years. The Brunhes-Matuyama geomagnetic reversal enables differentiat ion of volcanic rocks older and younger than 0.78 Ma. The lower submarine f lanks 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 f lank and central area include thick piles of younger rocks. Piton de la Fou rnaise is a highly and normally magnetized edifice, but its northern and ea stern flanks are underlain at shallow depth by reversely magnetized formati ons. The latter are regarded as remnants of Les Alizes volcano, associated with the Grand-Brule hypovolcanic complex. At the Matuyama-Brunhes transiti on the island was composed of at least two main volcanoes (Piton des Neiges and Les Alizes) 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 Alizes and is a relatively young focus of volcanism. These volcanoes have had successive phases of construction and destruction. The analysis of magn etic anomalies over Reunion was decisive in defining a new coherent model f or the evolution the island.