Evolution of sedimentary environment in the Gulf of Thailand since the last deglaciation

Understanding marine sedimentary process and the land-sea interaction is vital to human production and life. Gulf of Thailand is a hotspot of such research due to the strong erosion, transportation, and deposition processes under the control of the monsoon climate in the region over the last deglaciation. Based on comprehensive analyses of lithology, grain size, and element index of core BT-7, we revealed that the sedimentary history of this region could be divided into three stages: (I) 13.5-7.5 cal ka BP, continental deposition period, when the central Gulf of Thailand was completely exposed to the surface; (II) 7.5-6.2 cal ka BP, land-sea interaction period, when the material source varied abruptly and the weathering intensity changed significantly, corresponding to frequent climate fluctuations between cold and warm, along with intermittent sea-level still stands; and (III) after 6.2 cal ka BP, period of stable marine sedimentary facies, when the seawater inundated the central Gulf of Thailand, the weathering intensity was slowly weakened with no significant change, and the climate fluctuated with a trend from warm to cold. Notably, since 3.5 cal ka BP, the weathering intensity has been rapidly weakened, entering a small ice age, and the relatively stable sea level has led to a consistent sedimentary environment in the Gulf of Thailand into modern times. Therefore, this study reveals the evolution of sedimentary environment at the interaction of the Indian Ocean and the Pacific Ocean over the last deglaciation. Based on the robust evidence, our findings could help improve the understanding of the sedimentary patterns and land-sea interactions in history.