Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes A new Quaternary stratigraphy of the Kallang River Basin, Singapore: Implications for urban development and geotechnical engineering in Singapore Stephen Chua a,⁎ , Adam D. Switzer a,b , Timothy I. Kearsey c , Michael I. Bird d,e , Cassandra Rowe d,e , Kiefer Chiam f , Benjamin P. Horton a,b a Earth Observatory of Singapore, Nanyang Technological University, Singapore, 50 Nanyang Ave, S639798, Singapore b Asian School of the Environment, Nanyang Technological University, Singapore, 62 Nanyang Dr, S637459, Singapore c British Geological Survey (BGS), Edinburgh, Currie EH14 4BA, United Kingdom d ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University, Cairns, QLD 4870, Australia e College of Science and Engineering, James Cook University, Cairns, QLD 4870, Australia f Building and Construction Authority, 52 Jurong Gateway Road, #11-01, S608550, Singapore ARTICLE INFO Keywords: Quaternary Stratigraphy Geotechnical engineering Coastal evolution Singapore 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 ~38.5 m long sediment core obtained from Marina South (1.2726°N, 103.8653°E), and a previous record from Geylang (1.3137°N; 103.8917°E), to provide age constraints and stratigraphic reference. A new Quaternary stratigraphic framework for Singapore is pre- sented 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 (~125 ka BP). Subsequent subaerial exposure and weathering of the marine clay during the last interglacial pro- duced a ‘stif clay’ layer. The stif clay is unconformably overlain by Holocene transgressive sands and peats from ~9.5 ka BP, followed by marine clays with a maximum basal age of ~9.2 ka BP. Regressive sandy/peat units were subsequently deposited beginning ~6 ka BP. Here the new Quaternary stratigraphic framework for Singapore is pre- sented, 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. 1. Introduction Global relative sea level fuctuations of up to 120 m during the present and last interglacials have been determined through the inter- rogation of past proxy records and statistical modelling (e.g. Lambeck and Chappell, 2001; Hanebuth et al., 2009; Grant et al., 2014; Dutton et al., 2015). These continue to generate great interest with implica- tions for future sea-level rise (SLR) projections (e.g. Church et al., 2013; Horton et al., 2014) and concomitant efects on the coastal zone (e.g. Nicholls and Cazenave, 2010). Such past sea-level changes have pro- found impacts upon the broad, relative low relief Sunda shelf (Tjia, 1980; Hanebuth et al., 2011); a key feature of maritime Southeast Asia. Although previous studies have shed light on the late Quaternary stratigraphic architecture and evolution of the outer and middle Sunda shelf (e.g. Hiscott, 2001; Hanebuth et al., 2011; Alqahtani et al., 2015), we still know little of inner shelf stratigraphy. Singapore lies at the core of the palaeo-geographical area of Sundaland and thus provides an excellent location to study this inner shelf stratigraphy (Fig. 1A). Much of the current understanding of Singapore’s Quaternary geology was developed by studies in the 20th Century (e.g. Scrivenor, 1924; Alexander, 1950) and later through several geotechnical-focused reports (PWD, 1976; DSTA, 2009). Very recent work has comprehen- sively covered the pre-Quaternary bedrock geology and fault systems of Singapore (Dodd et al., 2019; Gillespie et al., 2019; Leslie et al., 2019; https://doi.org/10.1016/j.jseaes.2020.104430 Received 25 September 2019; Received in revised form 25 May 2020; Accepted 28 May 2020 ⁎ Corresponding author at: Earth Observatory of Singapore, Nanyang Technological University, Block N1.3-B1-15, 70 Nanyang Drive, S(637457), Singapore. E-mail address: stephen.chua@ntu.edu.sg (S. Chua). Journal of Asian Earth Sciences 200 (2020) 104430 Available online 12 June 2020 1367-9120/ © 2020 Elsevier Ltd. All rights reserved. T