An Outline of the Geology of Madagascar

Abstract

Madagascar is one of the larger islands in the world, and although there has been a geological survey which was active extending back well into French colonial times, in the non-French-speaking world our geological understanding of the island has remained inadequate. This is despite the interest which might have been assumed to have accrued, first as a result of Wegener’s theory and then from its later reactivation as a result of geophysical research. Half a century after Wegener there is still no agreement as to whether in continental reconstructions Madagascar should be placed adjacent to the Tanzanian coast to the north (e.g., McElhinny and Embleton,1976), against the Mozambique-Natal coast (Flores 1970), or basically left where it is (Kent 1974, Nairn 1978). There have been few attempts apart from McKinley’s (1960) comparison of the Karoo succession of southwestern Tanzania with that of Madagascar to follow the famous geological precept of “going to sea.” One critical reason is that although there may be a bibliography of several thousand items dealing with Madagascan geology as Besairie (1971) claims, they are items not generally available. The vital information gained of the geology of the offshore area by post-World War II petroleum exploration has remained largely proprietary. Without such data any account is inevitably incomplete. Indeed, the principal source of information, a source upon which this article draws heavily, is Besairie’s (1971) Geologie de Madagascar, and a later précis (Besairie, 1973).