THE LATE QUATERNARY ESTUARINE EVOLUTION OF SUNGEI NIPAH, PASIR PANJANG, SINGAPORE : A GEOMORPHIC AND GEOGRAPHIC INFORMATION SYSTEMS INTERPRETATION

Abstract

Borehole cores of the Sungei Nipah area are examined in an attempt to reconstruct the late Quaternary estuarine evolution and sea level changes in the region. Radiocarbon and TL dating techniques have been used to determine the ages of the sediments. In addition, GIS and DEM have been used to ascertain the geomorphic changes within the area due to anthropogenic activity during the last century. Apparently, Sungei Nipah was a small fluvial stream before (>137,000 years BP) the Last Interglacial. Marine sediments built up rapidly with the rise in sea levels during the Last Interglacial about 130,000 years BP. As eustatic sea levels fell once again, the stream switched back into a fluvial mode depositing possibly the younger units of the "Old Alluvium". There was a gap in sediment history between 130,000 to 63,000 BP and 40,000 to 9,000 BP indicating periods of non-deposition or erosion. The Post-glacial Marine Transgression resulted in eustatic sea level rise and the infilling of the valley by Holocene marine muds. Sea levels rose rapidly and peaked 2 to 3 metres above present between 6,000 and 3,500 BP. A peat swamp phase occurred in the upper and middle section of the estuary in the mid-Holocene (6,000 to 3,500 BP) at 1.36 to 2.16 metres above present mean sea level. As peat development declined, estuarine and/or fluvial facies completed the sequence. By the beginning of the twentieth century, the area was rapidly developed and the natural landscape was drastically altered, reducing the natural floodplain in area and replacing some of the geomorphic units such as mud flats and coral reefs by reclaimed land.