Abstract

The Sunda arc (Sunda Trench) represents a large convergent margin system that extends of about 5,000 km from the Bengal Fan to the south of Sumba Island in eastern Indonesia. The arc displays morphology of trench, slope basin, outer arc ridge, forearc basin and volcanic chain. From the trench to the outer arc ridge, the structure has been filled in by sediment. This structure was deformed by tectonic activity that forms the accretionary prism.

The combination of remote data and insitu data such as refraction and reflection seismic methods together with magnetic, gravimetric, and bathymetric measurements has led to a significantly improved understanding of the composition, structure, and tectonic evolution of the convergent margin system off West Java and South Sumatra. This data was acquired during a cruise conducted using Research Vessel SONNE belonging to the government of Germany. Analyses of sediments, rocks, and benthic fauna, recovered during the offshore work of the project, provided new information on the sedimentary processes in the convergent margin system.

These results show the difference of lithologic condition and geological process of convergent margin system between Java and Sumatra. The seafloor depth in the fore-arc basin is 3000 m off West Java and around 2000 m off the Sunda Strait and southern Sumatra. The Sunda trench marks the deepest part of the survey area. Water depths are more than 6500 m off Java and more than 6000 m off Sumatra