台灣濁水溪口晚第四紀的陸海相互作用及海岸環境變遷 The Land-Sea Duel and Coastal Environmental Change in the Late Quaternary at the Mouth of Zhuoshui River, Taiwan
地点：希平楼 C2-301，Xiping Bldg
主讲人/主办人：刘祖乾，教授 James T. Liu, Prof.
背景资料：【来访单位Institution】: 台湾中山大学，台湾 National Sun Yat-sen University, Taiwan 【邀请人Host】: 余凤玲， 副教授 【联络人Contact】: 陈敬艳 Chen Jingyan, email@example.com Abstract: The transition between sedimentary environments is compressed along land-sea boundaries in space and time. At river mouths on high standing islands, sedimentary records with high temporal resolutions formed as a result of large sediment loads and pervasive post-glacial sea level rise. Here we report on sediment core records covering the late Quaternary from the mouth of a small mountainous river in Taiwan. Results show that the study site was initially terrestrial under fluvial control. Beginning at about 10,000 yr BP (before present) the site became inundated by the rising sea and the environmental facies transitioned from a floodplain/incised river valley to a succession of marine environments, from shoreface to offshore. As the rising sea level came to a pause at 6000 yr BP, fluvial processes became dominant and sediments began to aggrade at the river mouth. After 4500 yr BP, the accumulated sediment began to prograde seaward, taking on the form of a river delta, and subtidal sand ridges appeared in the nearshore. This also introduced the deltaic development, which was limited by topography of the receiving basin. The chronology expresses the duel between sea level and fluvial processes that determined the depositional environments along the land-sea boundary at the study site. Using the sediment grain-size frequency distribution of modern coastal environments as a key, we also found progressive changes in coastal forcing on the paleo-deltaic sediments in the late Quaternary in the development of the delta.