珠江三角洲晚第四纪环境演化的沉积响应

珠江三角洲是一个复杂的网状河三角洲沉积体系,目前对其第四纪环境演化的历史仍存在多种认识。为进一步查清珠江三角洲地区第四纪环境演化的过程,对位于珠江口西岸的QZK6孔,在沉积结构、构造等研究的基础上,利用AMS14C和光释光(OSL)测年、有机碳同位素、粒度等对第四纪地层的形成年代和沉积特征进行了详细分析。结果显示,该孔39.40~27.38m发育晚更新世风化层、河流等陆相沉积体系,27.38~2.00m发育全新世三角洲沉积体系。其中全新世三角洲沉积又可分为27.38~5.30m由三角洲平原、三角洲前缘和前三角洲组成的退积式三角洲沉积体系,以及5.30~2.00m的河口湾-三角洲前缘进积式三角洲沉积体系。该孔第四纪沉积特征揭示的环境变化,是对末次冰期低海面、早中全新世海面升高及晚全新世下降的响应。

Sedimentary response to the Late Quaternary envi-ronmental evolution in Pearl River Delta

Pearl River Delta is a complex anastomosed delta system, and a number of debatable views concerning the environmental evolution during Quaternary period have existed since the 1970s-1980s. For a better understanding of the process, multidisciplinary approaches to the Core QZK6, drilled recently in the west bank of Pearl River estuary, have been carried out for exploring the environmental changes superimposed upon the depositional characteristics, including depositional structure and texture, grain size and organic carbon isotope analyses, AMS ¹⁴C and OSL (optically stimulated luminescence) dating. It is indicated that the terrestrial sedimentation of weathered layers and fluvial deposits at the depth of 39.40~27.38m formed in the Late Pleistocene, the retrograde delta sedimentation of delta plain, delta front and prodelta at the depth of 27.38~5.30m developed during the 10.982~2.087ka cal BP, and the prograding delta sedimentation of estuary to delta front at the depth of 5.30~2.00m deposited during the 2.087~0.203ka cal BP, were responses to the sedimentary environments with a low stand sea level during the last glacial period, a growing sea level during the Early to Middle Holocene, and a falling sea level during the Late Holocene respectively.