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​PhD Oral Defense of Stephen Chua: Quaternary Palaeoenvironments of the Kallang River Basin, Singapore

Published on: 21-May-2019

Event Type: Oral Defense
Event Date: 21 May 2019 - 1:00pm to 2:30pm
Venue: ASE 3D Viz Laboratory Room (N2-B1c-16c)
Speaker: Stephen Chua

About the speaker:

Stephen Chua received his B.A. (Hons) in Geography in 2003 and MSc (Environmental Science) in 2010 from NIE/NTU. His undergraduate dissertation focuson reconstructing palaeoenvironmental changes to the Sungei Buloh-Kranji mangrove coast, while his Master’s work involved monitoring and predicting potential impacts of sea level rise on the Pasir Ris mangroves. Stephen joined the Interdisciplinary Graduate School NTU as a Ph.D. student under the supervision of Associate Professor Adam Switzer (ASE) and Dr Beverly Goh (NIE) in 2014. He received an Endeavour Research Fellowship in 2017 to conduct isotopic analysis of sediments at the Advanced Analytical Centre, James Cook University, Cairns. Stephen was a recipient of the Outstanding Student Poster Award at the American Geophysical Union Fall Meeting in 2018. During his Ph.D., he used borehole data to conduct geological modelling of the Kallang River Basin, and used sedimentological and geochemical records from sediment cores in Singapore to reconstruct past sea level, morphological and environmental changes.

About the event:

The Quaternary period (last ~2.6 Ma) was marked by a series of >50 glacial–interglacial climate cycles. Palaeoenvironmental records from this period enable us to reconstruct past changes in sea level, climate and associated environmental response, and provide critical information to prepare for future environmental change. Unfortunately, there remains a paucity of such records in the Sunda shelf region where > 450 million people face environmental risks associated with future climate change, with a significant number living in coastal megacities built on Quaternary coastal-marine sequences. Singapore lies near the relatively tectonically-stable core of Sundaland, which coupled with a low tidal range (~2.2m) and relatively low-energy wave regime result in reliable sedimentary archives recording palaeoenvironmental coastal change.

 I present the Quaternary stratigraphy, sea level, and coastal change, of the Kallang River Basin (KRB) based on high-resolution sedimentological and geochemical analysis of a ~38.5 m sediment core (~-50m MSL) sediment core (MSBH01B), constrained by 17 14C AMS dates, and augmented by borehole data within the KRB.  First, I created the first 3D geological model with chronology constrained by radiocarbon and OSL ages. I also added 4 new sea level index points (SLIPs) to existing SLIPs, and used a Bayesian modelling approach to produce a revised and extended Holocene sea level history for Singapore. Finally, I present an early-mid Holocene coastal evolution model for Singapore showing that coastal mangroves succeeded in colonising the early Holocene Singapore coast but eventually succumbed to continued rise in sea level as recorded by a prograding delta system by ~7.8 ka BP, coeval with global delta initiation. This study improves our understanding of Singapore’s Quaternary stratigraphy and contributes new knowledge about early-mid Holocene sea level and environmental change in Singapore and the region.

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