Abstract

Two modern sediment cores from the Makassar Straits have been analysed in detail (every 10 cm) for foraminifera and palynomorphs. The Papalang-10 core (650 cm) was collected from the basin floor distal of the Mahakam Delta from 2345 m water depth, whereas Sangkarang-16 (490 cm) was collected from offshore Sulawesi from 793 m water depth. The topmost sample from about 60 additional cores from various localities and from 100 m to 2400 m water depth have been analysed for foraminifera and palynomorphs to provide control with respect to the water depth relationships of foraminifera, and patterns of transportation from shorelines with respect to palynomorphs. The Sangkarang-16 core penetrates the last interglacial (in oxygen isotope stage 5), whereas Papalang-10 bottoms in isotope stage 3 in the last glacial.

The analysis of foraminifera from the surface samples indicates that benthonic foraminifera in Makassar Straits show little variation with water depth, and data from the two boreholes show little temporal variation between glacial and interglacial periods. This is thought to be due to the effect of the Mindanao Sill (1500 m) that limits the flow of deep Pacific water into the Makassar Straits. With respect to foraminifera, the main difference between 'high' and 'low' sea level periods probably relates to surface water productivity, indicated by planktonic abundance.

The results of palynological analyses reflect the history of vegetation within the region, which relate to patterns of climate change, and provide a proxy for a level change. Comparison of the palynological succession with that recorded from nearby cores that have been dated radiometrically provides time control. The pollen record of coastal vegetation (e.g., mangroves) also provides data on patterns of sea level change.

The combination of foraminiferal and palynological analysis provides a strong tool for the characterisation of regional climate and the nature of water masses during periods of low, rising and high sea level, which may be applied directly to Makassar Straits Neogene well sections to augment sequence stratigraphic interpretations.