Publications

Recent analyses of SAR-maps covering South Sumatra show WNW-ESE, N-S, NW-SE and k N 30",E dominant trends (or fault strikes).Similar trends were recognized earlier (1990-1991) from Landsat studies and aerial photo/SAR interpretations backed up by geological field data in the Garba Area and Negara Batin (Lampung) sub-basin. Previous seismic work in the Palembang Basin (also) revealed the WNW-ESE, N-S and N 30",E trends as major deepseated faults.The complex lineament pattern on the maps are seen as a combined expression of structural phenomena induced by main diastrophic events (or tectonic phases) within this part of Sundaland.Therefore, to distinguish structural patterns of same genetic origin or related to a particular tectonic phase in this region with a convergent plate tectonic setting since the Jurassic, is necessary. The principle of rockfailure with inherent main stress direction and intensity due to the colliding and subducting Indian oceanic plate upon Sundaland is integrated in the study.The distribution of granitoid intrusives of Jurassic and Cretaceous ages previously mapped by the Directorate of Geology and also known from oil companies drillings, has been reviewed in this study and proved to be of utmost importance to explain the geological evolution of Sundaland since Jurassic times.Ellipsoid models for Mid-Mesozoic (Upper Jurassic - Lower Cretaceous), Upper Cretaceous - Lower Tertiary and Mid-Tertiary (Mid-Miocene) main tectonic phases, clearly discern wrench, normal and upthrust components for each phase among the recognized dominant trends.Hence, the conclusion that initiation of the South Sumatra back-arc basin took place in the Paleogene by way of subsiding ",block-areas", along an established framework of primarily WNW-ESE (Lematang) and N-S trending strike-slip faults of Pre-Tertiary origin which became rejuvenated as normal faults with the start of (Tertiary) basinal history.Compressive tectonics in the Neogene marked the South Sumatran back-arc basin development a.o. inducing inversion of faulted block areas along the WNW-ESE trending faults.The NW-SE (Barisan or Semangko) trend clearly offsets the WNW-ESE trend and presently is encountered as an active strike-slip faultzone at crestal parts of the Barisan Mountain Range.