Investigating the main driving factors in the Holocene evolution of Qing’ao Embayment, Nan’ao Island, southern China
Monday, June 15, 2015: 2:30 PM
Adam Switzer1,2, Jeremy Pile1, Fengling Yu3, Meyer Zhao-Zheng4, Harry M Jol5, Deli Wang3, Bishan Chen4 and Minhan Dai3, (1)Earth Observatory of Singapore, Nanyang Technological University, Singapore, Singapore, (2)Nanyang Technological University, The Asian School of Environment, Singapore, Singapore, (3)Xiamen University, State Key Laboratory of Marine Environmental Sciences, Xiamen, China, (4)Sun Yat-sen Universtiy, School of Earth Science and Geological Engineering, Guangzhou, China, (5)University of Wisconsin Eau Claire, Eau Claire, WI, United States
Abstract:
This study investigates the Holocene evolution of the Qing’Ao embayment, a small coastal embayment on Nan’Ao Island in southeast China. The results of sedimentary lithology, grain size, loss on ignition, pollen and foraminifera suggest three main phases of Holocene evolution in the embayment. The first phase (~8400-6000 cal yr BP) is characterized by a basin wide shell-rich sandy, silty, clay facies of early Holocene age that overlies presumably older but chronologically unconstrained marine transgressive sand deposits. Collectively, the first phase records an initial sedimentation phase associated with the early Holocene transgression into the embayment and a highstand of relative sea level. The basal facies grades upward to a mixed sandy coastal system consisting of 2 small lagoons and associated sandy tidal flats formed between 6000 and 1300 cal. yr. BP that appears coincident with the falling regional sea level and reduction in sediment accommodation space. The final phase, is characterized by a thin terrestrial sequence dominated by fluvial floodplain facies, that spans the last ~1300 cal. yr. BP, and is capped by contemporary soils. As climate during the Holocene in this region was relatively stable our model suggests that changes in the falling sea level and reduced accommodation space are the two main driving mechanisms for the Holocene evolution of the Qing’ao embayment. In the small embayments of southeast China like Qing’Ao the influence of sea level change and accommodation space is likely much stronger agent of coastal change and evolution than that of monsoon variability and may have overwritten the monsoon signal. The later phases of the embayment record the clear impact of humans.
