Abstract

The Quaternary stratigraphy of many coastal areas in Southeast Asia is poorly understood. Developing a detailed framework is important as many coastal cities are built on these unconsolidated coastal-marine sediments. This study reviews the current understanding of Quaternary deposits in the Kallang River Basin, Singapore, using 161 boreholes to create 14 cross-sections and a 3D geological model. The dataset is augmented with a similar to 38.5 m long sediment core obtained from Marina South (1.2726 degrees N, 103.8653 degrees E), and a previous record from Geylang (1.3137 degrees N; 103.8917 degrees E), to provide age constraints and stratigraphic reference. A new Quaternary stratigraphic framework for Singapore is presented here, constrained by new radiocarbon and Optically Stimulated Luminescence (OSL) dating, and identify palaeo-features that record the geomorphic and sedimentary evolution of the basin. Fluvial deposits of Pleistocene age are uncomfortably overlain by littoral/tidal sands and subsequently marine clay possibly during Marine Isotope Stage (MIS) 5e (similar to 125 ka BP). Subsequent subaerial exposure and weathering of the marine clay during the last interglacial produced a 'stiff clay' layer. The stiff clay is unconformably overlain by Holocene transgressive sands and pears from similar to 9.5 ka BP, followed by marine clays with a maximum basal age of similar to 9.2 ka BP. Regressive sandy/peat units were subsequently deposited beginning similar to 6 ka BP. Here the new Quaternary stratigraphic framework for Singapore is presented, as well as provide important constraints on the regional sea-level history and geomorphological evolution of Singapore's southern coast from MIS 5e to present. The work also highlights the complexities of geoengineering work in such subsurface terranes.