长江河口沙坝全新统沉积特征和环境变迁

长江口崇明、长兴、横沙等岛屿是由全新世长江的河口沙坝孕育而成。晚更新世末长江门曾遭受了强烈的侵蚀,古河谷切割甚深。嗣后,在此地质背景上发育了河口沙坝,其全新世沉积相当完整。它们是研究长江河口三角洲形成史和沉积过程的有力证据。笔者着重探讨全新统的沉积环境变迁,旨在为研究长江三角洲发育及其经济区的开发提供地质依据。

SEDIMENTARY CHARACTERISTICS AND EVOLUTION OF HOLOCENE RIVER-MOUTH BARS IN THE CHANGJIANG ESTUARY

The islands in the Changjiang estuary, such as Chongming, Changxing and Hengsha, are originally of Holocene river-mouth bars. The Holocene sedimentary sequence fully developed due to the deep Late-Pleistocene valley of the Changjiang River. The Holocene sediments of the islands can be divided into six subfacies (from bottom to above): drowned valley, nearshore, shallow sea, delta front, river-mouth bar and delta plain. These subfacies sections differ from each other in sedimentary texture, structures, heavy mineral association, pollen and spores, and micro-paleontology, etc.In the course of the Holocene transgression and regression, the area of the river-mouth bars has experienced in an orderly way as the following environments: drowned valley, nearshore, shallow sea, delta front, river-mouth bar and delta plain.