Publications

The Neogene climate history of the broad Makassar Straits region has been assessed by combining palynological studies of two well dated Late Quaternary cores from the ocean floor with analyses of cuttings samples from shelf and slope exploration wells from the Makassar Straits, emphasising the Attaka region. The wells penetrate the Early Pleistocene to Middle Miocene. The two Late Quaternary cores are: 1) Papalang-10 core, spanning about 30.000 years (30 ka) and located at the base of the Mahakam fan, close to the equator, and 2) Sangkarang-16 core, offshore South Sulawesi, in a subequatorial setting at about 6oS, and spanning about 95 ka.The Papalang-10 core provides a record of the former vegetation and climate history for the Mahakam catchment, and indicates the continued presence of rain forests throughout the last 30 ka, but with a cooler last glacial maximum, contradicting previous palynological studies of cores taken from the Mahakam Delta. The Sangkarang-16 core probably provides a record of the vegetation which grew within the catchment of the large river system that occupied the current Java Sea during oxygen isotope stages 2-4 (last glacial period), and shows the significant development of grasslands during this time, suggesting a distinctly seasonal climate, especially during the last glacial maximum. Based on a simple climate model constructed from these two cores which links sea level change with change of temperature and seasonality, the history of sea levels, vegetation and climate for the Makassar Straits can be extrapolated back to the Middle Miocene using the palynological record obtained from shelf and deep water exploration wells. Particular emphasis is placed on the Attaka region with attention being given to using the climatostratigraphice rcord, calibrated by high resolution nannofossil data, to help to understand shelf to slope correlation issues and overall sedimentation patterns for the Attaka area. The Mio-Pliocene climate history for the area is also discussed in relation to existing climatostratigraphic successions from the Natuna and Malay Basins in order to provide a regional perspective of Neogene climate change across the Sunda region. It is thought that the continually everwet climate of equatorial Borneo, at times of low sea level, was a key factor in the development of organic rich deep water source rocks in the circum-Borneo region.