MOZAMBIQUE‐MADAGASCAR GEOSYNCLINE, II: PETROLEUM GEOLOGY

The Mozambique‐Madagascar geosyncline may rank above congeneric borderland down warps along the western Indian Ocean in its hydrocarbon exploration quality. On the Mozambique flank, gas in significant quantities has been produced on test. On the Madagascar flank, bitumen in equally significant quantities has been outlined. Exploration of the geosyncline as a whole has included the drilling of more than 30 wells on the Mozambique flank, and more than 40 wells on the Madagascar flank. Of this total of more than 70 wells, 15 exceed 4,000 m in depth. Objectives almost untouched by the drill are the Karroo strata below basalt on the Mozambique flank, Karroo strata below marine Jurassic onlap on the Madagascar flank, and Karroo strata that this writer believes should exist in continental and mixed facies at the center (below deep waters of the present Mozambique Channel). Considerable depth of burial of all these Karroo objectives should enhance the maturation of their original organic matter to the hydrocarbon stage, even though that matter was initially vegetal and palynomorphic. Post‐Karroo objectives may be limited to the geosynclinal flanks, because pelagic facies may have dominated the center throughout post‐Karroo time. Limitation to the flanks, however, does not adversely affect depth of burial in many areas. Post‐Karroo strata, in fact, may rival their Karroo predecessors, especially considering the presence of marine intercalations. Principal exploration parameters such as sedimentary volume, source rock, reservoirs, and present density of drilling, are favorable or good. They suggest that the Mozambique‐Madagascar geosyncline is a prospect worthy of much additional deep drilling to find major reserves of petroleum.