Facies And Biofacies Of The Late Quaternary Deposits At West Johor, Malaysia: Indicators For Sea-Level Changes, Palaeoshoreline, And Palaeonvironment

In this study, sedimentological and foraminiferal analyses were conducted on two borehole samples (BH1 = 42 m and BH2 = 39 m) at Pontian in west Johor, Peninsular Malaysia. The sedimentological description established ten facies (A to J). They comprised three associations and two sedimentary environments (i.e., estuary and delta plain). The foraminiferal analysis identified four distinct biofacies through similarity plots of taxonomic compositions and their respective groups for each borehole. Each group was designated as Biofacies Ia to Id for BH1 and IIa to IId for BH2. The deposition began with the formation of a small tidal-dominated estuarine basin in the flooded palaeovalley and the subsequent development of a peat-forming estuarine channel that resulted from the flooding of a supratidal zone. Relative sea-level changes were assumed localised to a basin scale. The maximum limit of tidal influence was benchmarked using a mangrove classification for a terrestrial boundary. Based on the foraminiferal analysis, this study identified a few episodes of flooding events, implying the occurrence of several migrations of the paleoshoreline throughout the sequence that traced the configuration of the maximum paleoshoreline.