台风对珠江口全新世沉积序列的建造作用

Typhoons play a critical role in the construction of sedimentary sequeces in the coastal waters. A pilot study (Huang and Yim, 1997) identified a number of storm beds in the offshore cores of Hong Kong. This project is designed to reconstruct Holocene record of typhoons through the examination of offshore cores from the Pearl River Estuary together with historical records and instrumental observation. The main objectives of this project are: to examine historical and instrumental data to provide a means of checking against the Holocene record of typhoons which can be obtained from sediment cores; to analyse the forcing mechanism responsible for typhoon-induced seabed erosion and deposition across the estuary, to identify typhoon signatures from cores through examining physical, chemical and biological characteristics of sediments; to reconstruct the Holocene sedimentary sequence of typhoons; to separate typhoon variability from sea-level change and compare the findings to regional and global records. Combining with seabed sampling, water-column and hydrodynamic observation are applied to examine typhoon-induced sediment resuspension, transportation and deposition across the estuary. Carbon isotopes(δ13C), C/N, diatom and foraminiferal techniques are applies to examine typhoon signatures in offshore cores.

上世纪90年代，申请人在珠江口香港水域的全新世地层钻孔中发现有多层沉积组分和结构异常的沉积体，并首次将其定为台风暴潮沉积。本项研究将在此基础上对珠江口台风沉积机制及其对全新世地层序列的建造作用进行全面深入的研究，利用水下观测、历史记录对比、海底采样测试、数字模拟等多种技术手段，揭示在正常气候条件下与极端性台风作用下现代珠江口的沉积动力机制、沉积特点和分布规律；利用海底观测以及沉积物的物理学、化学和生物学组合特征，分析沉积后期改造和保存机制；利用钻孔岩芯样品，进行测年、磁化率、X透视影像、粒度、有机碳同位素 (δ13C)和碳氮比（C/N）、硅藻、有孔虫、软体动物贝壳等分析，提取全新世沉积物记录的台风信息，通过多钻孔剖面的时空对比，结合气候演变、海平面变化、海岸变迁、河流水量变化等影响因素，建立珠江口全新世台风沉积的时空序列，重塑河口和三角洲沉积演化模式。

本项研究对珠江口台风沉积机制及其对全新世地层序列的建造作用进行全面深入的研究，利用水下观测、历史记录对比、海底采样测试、数字模拟等多种技术手段，揭示在正常气候条件下与极端性台风作用下现代珠江口的沉积动力机制、沉积特点和分布规律；利用海底观测以及沉积物的物理学、化学和生物学组合特征，分析沉积后期改造和保存机制；利用钻孔岩芯样品，进行测年、粒度、有机碳同位素 (δ13C)和碳氮比（C/N）、生物标志物（正构烷烃组合及长链烯酮）、软体动物贝壳等分析，提取全新世沉积物记录的台风信息，通过多钻孔剖面的时空对比，结合气候演变、海平面变化、海岸变迁、河流水量变化等影响因素，重塑河口和三角洲沉积演化模式。本项目的主要研究成果：（1）根据现代沉积物测试，基于碳同位素率、长链烯酮浓度和正构烷烃指标建立了珠江口沉积物的海陆来源分布模式；（2）揭示了珠江口表水稳定同位素比率δD与 δ18O的空间分布特征，建立了二者与盐度的线性相关系；（3）发现并探索大屿山南部钻孔沉积中断及贝壳富集层的成因问题；（4）重建了珠江口全新世海侵、沉积速率、水动力与SST的历史变化；（5）解释了全新世海平面变化与珠江三角洲地层的演化。