The old alluvium of Singapore and the extinct drainage system to the South China Sea

Abstract

In both sand quarry faces and boreholes the Old Alluvium of Singapore is a matrix supported pebbly sand with minor beds of better sorted sands and clays. The beds can be grouped into four textural classes (pebbles, coarse sand with fine pebbles, medium to coarse sand, clay, and silt), each with characteristic sedimentary structures. The deposit appears to be the proximal facies of an ancient braided river alluvium of possible Pleistocene age.This widespread but scattered alluvium is found both on land and offshore on the Sunda Shelf in Southeast Asia. It is believed to have been deposited during low sea levels. In Singapore, the mineralogy of the grains forming the Old Alluvium suggests a mixed provenance of granitic and low-grade metamorphic origin. The volume and freshness of the deposited material indicate an environment of considerable relief, seasonal rainfall, and extremely active erosional processes, conditions considerably different from the current ones. The Old Alluvium was probably deposited by seasonal rivers which experienced periodic large floods. Such regional conditions could have prevailed over much of Southeast Asia at the time of deposition of the Old Alluvium.

Mammals of south‐east Asian islands and their Late Pleistocene environments

“…During the glacial periods, climates may have been drier, colder and more seasonal (Verstappen, 1975, 1980, 1997; Gupta et al , 1987; Stuijts et al , 1988; Thorp et al , 1990; Thomas et al , 1999). Some authors have therefore suggested that during the LGM, the land between Borneo, Sumatra, Java and the mainland was covered in savanna‐type vegetation (Muller, 1975; Morley, 1981; Morley & Flenley, 1987; Broecker et al.…”

Unchanged nitrogen isotopic composition of organic matter in the South China Sea during the last climatic cycle: Global implications

“…During glacial times, vast shelf areas in the northern and especially in the seahern SCS emerged, generally leading to an increased terrigenous input into the basin of up to fivefold [SchOnfeld and Kudrass, 1993;Huang and Wang, 1998;Wang, 1999] and the development of additional drainage systems on the emergent shelves [Molengraaff, 1921;Gupta et al, 1987]. Glacial primary production, as inferred fi'om organic carbon and opal accumulation rates [Sarnthein et al, 1988;Thunell et al, 1992;Lin et al, 1999] and the species assemblages of planktonic and benthic foraminifera [Miao and Thunell, 1996;Huang et al, 1997;Kuhnt et al, 1999], as well as nutrient concentrations, as inferred fi'om the foraminiferal carbon isotopic composition [Wang et al, 1999] and Cd/Ca ratios of planktonic foraminifera [Lin et al, 1999]…”

Geomorphological Evidence for Quaternary Climatic Change in the Low Sino‐burman Ranges

“…Pediments on the lowlands of Peninsular Malaysia appear to have formed in relatively dry conditions under a fairly open vegetation cover. Active erosion of unweathered rocks, short distance transport and rapid burial by a seasonally flooding braided river system have been suggested for Pleistocene Singapore when the site lay 300 km inland (Gupta et al, 1987). The sediment deposited was coarser and less well sorted than that being deposited by contemporary rivers which bears comparison with the situation in the Nam Khong area.…”