摘要
对珠江三角洲西江河口附近PRD05孔(113°11′02″E,22°31′24″N)的岩性和介形类的高分辨率分析表明,受海平面变化和河流作用的影响,研究区晚第四纪经历了多次环境变化。26600aBP以前为河流环境,底部为河道沙砾沉积,随后水动力条件减弱,发育河漫滩沉积。26600—13400aBP前期发育泛滥平原相沉积,后期受末次冰期的影响,本区暴露地表遭受风化剥蚀,泛滥平原相沉积的上部风化成杂色黏土。珠江口地区冰后期海侵应开始于约13400aBP。13400—9000aBP为海侵初期,本区形成沼泽相沉积。9000—4850aBP为全新世大海侵时期,本区为持续的河口海湾环境,发育以海相—半咸水型为主的介形类动物群,发生了3次小规模的海平面波动,导致水体条件发生变化,从而影响了介形类动物群的组成和丰度。最大海侵发生于7500—7140aBP之间,PRD05孔主要介形类属种的丰度在这一阶段达到全新世最大值。4850aBP以来为持续海退期,河流作用增强,本区逐渐转变为上三角洲平原环境。
A high resolution study has been carried out on the sediments and ostracod faunas of borehole PRD05 drilled near the Xijiang inlet in the Pearl River Delta area. The analytical results suggest that the interplay between sea level fluctuations and river processes led to the environmental changes in the study area during the Late Quaternary. A fluvial environment began to develop before 26 600 a BP. Coarse-grained sediments at the bottom of the core indicate a very high energy condition. The reduction of grain size upwards implies a decrease of energy and fluvial overbank was developed. Between 26 600 and 13 400 a BP, the environment was characterized by a flood plain. The upper part of the fluvial sediments experienced weathering and erosion during the last maximum glacial episode and was changed to the variegated clay. The postglacial transgression occurred around 13 400 a BP. In the first phase of transgression, a marsh environment dominated in the study area. At around 9 000 a BP, the rate of sea level rise rapidly increased and an estuary environment with marine-brackish ostracod faunas continuously existed until 4 850 a BP. Three second-order sea level fluctuations can be recognized based on the composition and abundance of ostracods. The maximum transgression occurred between 7 500 and 7 140 a BP, evidenced by the highest diversity and abundance of ostracods in the borehole. Since 4 850 a BP, a regressive trend was recorded in the borehole. The environment gradually changed into a deltaic plain with the increased influence of river processes.
出处
《古地理学报》
CAS
CSCD
2008年第3期313-322,共10页
Journal of Palaeogeography：Chinese Edition
基金
国家自然科学基金重点项目(编号:40331007)
广东省自然科学基金项目(编号:04009757)
中国科学院边缘海地质重点实验室资助
广州地球化学研究所开放研究基金(编号:MSGL07-18)资助
关键词
珠江三角洲
介形类
高分辨率
晚第四纪
古环境
Pearl River Delta, ostracods, high resolution, Late Quaternary, palaeoenvironment
