Bulletin of the Geological Society of Malaysia, Volume 62, December 2016, pp. 47 – 56
1School of Marine & Environmental Sciences, Universiti Malaysia Terengganu, Terengganu, Malaysia
2State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
*Corresponding author: email@example.com
Abstract: Architecture and morphology of the paleo-incised valleys in Penyu Basin, South China Sea (SCS) was investigated using high-resolution two-dimensional (2D) acoustic profiles. Acoustic surveys were conducted in 2009 using a CHIRP sub-bottom profiler. The paleo-valleys were formed during several phases of regression and subsequent Last Glacial Maximum (LGM) when the sea level was approximately 123 ± 2 m lower than present-day mean sea level (MSL). These valleys were filled during lowstand and subsequent postglacial marine transgression and subsequently submerged during last glacial cycle. Holocene shallow-marine cover healed the ravinement surface. Three distinct facies and two bounding surfaces are categorized in the CHIRP profiles. Lithified pre-glacial deposits (Unit-III) are characterized by possible previous highstand deposit and regressive shoreface deposits. The erosional surface is demarcated as lowstand sequence boundary that overlain by transgressive fluvial deposits. Several stages of the incision and infilling are identified, possibly caused by fluctuating sea level transgression. The average late-Pleistocene (LGM) surface lies between 53 to 64 m below present-day MSL in the study area with ~ 16 to 50 m of valley incision. The valley slope varies 35 to 85° correspondent with the horizontal horizon. The Holocene shallow-marine cover thickness varies from 3 to 10 m.
Keywords: CHIRP acoustic profile, paleo fluvial geomorphology, sea level change, sequence stratigraphy, Last Glacial Maximum