Publications

Indonesia is surrounded by subduction zones which are the cause of the intense seismicity and volcanic activity in the region. Subduction has been the most important tectonic driver and has led to the collisions that caused growth of continental SE Asia, and more recently to the development of Australia-SE Asia collision in eastern Indonesia. In eastern Indonesia there are subduction zones at different stages of development, from mature examples, such as the Banda system that began to roll back from about 16 Ma, to younger systems such as North Sulawesi. There is a close relationship between subduction and extension, and this has caused both dramatic elevation of land regions and exhumation of deep crust, and similar spectacular subsidence of basins, which are imaged by oil exploration seismic and multibeam data sets. It is difficult to quantify the amounts of uplift of land surfaces, although close to areas that now include young granites and high grade metamorphic rocks at elevations of up to 3 km are shallow marine and alluvial late Neogene sediments implying vertical movements of several kilometres. Offshore there are valuable markers provided by carbonate reefs that formed close to sea level, now found at depths of up to 2 kilometres. Dating all these rocks is a challenge but it appears that subsidence and uplift takes place during very short time intervals and at very high rates, and is associated with rapid extension and rollback of subduction zones. Reconstructions, modelling and theoretical studies can provide valuable insights into the geological history of unique regions such as eastern Indonesia. However, it needs to be recognised that much of the literature concerned with this challenging region is the product of multiple recycling events and it is frustrating and common to read conclusions based on premises that are clearly wrong. There is still a need for new studies that can provide material, for example to reliably identify and date tectonic events, and field-based studies continue to provide surprises, new insights and data essential for sound interpretations.