RIFTING AND MOUNTAIN BUILDING ACROSS SUNDALAND, A PALYNOLOGICAL AND SEQUENCE BIOSTRATIGRAPHIC PERSPECTIVE

摘要

The broad Sunda region formed as a result of the rifting of fragments of Gondwana, their northward movement, and their collision with Asia from the Triassic, and was essentially in place at the beginning of the Cenozoic. The region subsequently underwent extensive deformation and rifting, with the docking of the E Java/W Sulawesi Terrane, the formation of the Makassar Straits dividing west Sulawesi from Borneo during the Eocene, and the formation of numerous rifts in the western and northern part of the region, ranging from West Java Sea, through Sumatra, across the South China Sea to West Natuna and Nam Con Son, and northward to mainland Thailand. The opening of the South China Sea and northward movement of the Australian Plate also resulted in widespread uplift, especially in Borneo, the character of which remains unclear. Understanding the relationships between these different rifting and uplift events, and also their timing, requires good dating, and this is often difficult to achieve in essentially non marine basins, of which all of the rift systems were composed in their initial stages. This paper emphasises the use of palynological data combined with marine microfossil assemblages from the more distal basins to demonstrate that when approached from a sequence biostratigraphic perspective, many questions can be resolved. The paper discusses the timing of the opening of the Makassar Straits and associated basins and the subsequent stepwise uplift history of the circum Borneo region. For the western and northern rifts, discussion centres on the timing of rifting, their scale, longevity of the rift lakes and the extent of associated uplands, and makes comparisons with the present day East African rift system.