Oceans, New Frontier in Exploration

Attractive hydrocarbon prospects of the offshore do not end or necessarily diminish at the edge of the continental shelf. Large geosynclinal basins along continental margins offer interesting targets for exploration in deeper water. Continental margins are broad boundary zones between ocean basins and continents. Two basic types are distinguished: Atlantic-type margins, where collapse and exension tectonics combined with regional subsidence led to the formation of marginal geosynclines; and Pacific-type margins, following the trend of active orogenic systems, where repeated phases of tectonic and related magmatic activity created a complex array of basins and uplifts. Seismic profiles from the offshore of the African continent and northwest Australia illustrate the tectonic framework of Atlantic-type margins. The Sunda arc is shown as a typical example of Pacific-type margins.