闽江河口第四纪沉积特征及演变历史

Quaternary sedimentary characteristics andevolvement of the estuary of Minjiang River

本文研究了闽江河口钻孔揭示的第四纪沉积物的生物、粒度和矿物特征,并探讨了闽江河口的演变历史。在中生代构造运动所奠定的地貌基础上,闽江自第三纪至第四纪早期以上升剥蚀为主,第四纪初期沙溪、富屯溪、建溪等河流即已流归闽江,形成了一条较大的河流,但当时河床大多基岩裸露,直至晚更新世晚期始接受洪冲积相沉积。随着末次冰期的结束,海面不断上升,但早全新世早期闽江河床仍高居于海面之上,仍以河流相沉积为主;早全新世晚期,海水开始侵入闽江,形成了湖沼—河口相沉积。至中全新世,海面已上升至现今海面位置,海水沿闽江河谷入侵,闽江河口退至白沙附近,琅岐岛一带为海湾环境,并接受了相应的沉积。晚全新世河口下移,琅岐岛附近成为河口环境,形成了一套以河口沙坝相和河口相为主的沉积。

In this paper, the characteristics of the biology, mineralogy, and the grain-size of the Quaternary sediment were studied based on the data from the drilling cores of the Minjiang River estuary.The evolutional history of the Minjiang River estuary was also discussed.During early Quaternary, the Minjiang River as a major river system took the shape confined by the Mesozoic tectonic configuration.The bedrock of the river at this stage was most likely exposed and did not receive sediments until late Pleistocene.The evidences of biological mineral and grain-size analyses show that the late Pleistocene deposits are mainly of diluvial-alluvial facies, the early Holocene deposits are dominated by river facies and estuarine-littoral facies, and that of the middle Holocene are chiefly of gulf facies, whereas the late Holocene estuarine sandbar and estuarine facies.