香港岛水域全新统重矿物与硅藻记录及其古环境意义

通过对香港岛水域V10柱样中化石硅藻与重矿物的鉴定分析，结合14C年代数据，探讨了该区全新世环境的演变过程及硅藻组合和重矿物组成对海洋环境变化的响应。结果显示：全新世该水域硅藻始终以沿岸半咸水种占据绝对优势，其次为咸水种，基本不见淡水种；重矿物中自生黄铁矿和菱铁矿占有相当大的比例，共同反映该区自全新世以来为近岸低盐的海洋环境，沉积界面以强还原条件为主。受全球及区域气候变化影响，该区全新世气候与环境变化呈现出阶段性和复杂性：其中，约11 650―10 650 cal. a BP，气候由冰期的寒冷转向温凉，海平面上升；10 650―7 200 cal. a BP，气候温暖但可能较为干燥，海平面的变化仍主要受海侵的影响；7 200―6 000 cal. a BP，气候温暖湿润，夏季风降水大幅增加，海平面继续上升，到6 900 cal. a BP达到最高海平面；6 000 cal. a BP之后，夏季风减弱，海平面回落，气候可能又变为温干。

Diatom and Mineral Records in Core Sediments from Hongkong During the Holocene and Their Paleoenvironmental Significance

Based on the identification and analysis of diatom fossiles and heavy minerals, and combined with 14C ages in the V10 core from Hongkong, we discussed the evolution of Holocene environment in the studied area, as well as the responses of diatom assemblages and heavy mineral compositions to the marine environment changes. The diatom analysis results show that coastal brackish water species always occupied absolute advantage during the Holocene, followed by the marine species, and almost no freshwater diatoms were detected. Meanwhile, mineral analysis reveals that authigenic pyrite and siderite possessed a large percentage in heavy mineral composition. So, these two indexes together indacate that the studied area was in low-salinity inshore environment over the last 10 ka, and the depositional interface was strong reducing condition during the most time of the Holocene. Affected by the global and regional climate change, the Holocene climate and environment of the studied area evolved in phase. From 11 650 to 10 650 cal. a BP, the climate became warm or cool after the cold last glacial period, and sea-level began to rise. During 10 650~7 200 cal. a BP, the Asian summer monsoon intensified, the climate became warm but may be relatively dry, the sea-level change was still mainly controlled by the global transgression, and the water salinity maximum occurred during this stage. The period of 7 200~6 000 cal. a BP was a warm and humid stage. At this time, the sea-level continued to rise and reached its highest point around 6 900 cal. a BP as a result of increased summer monsoon precipitation and freshwater discharge. After 6 000 cal. a BP, sea-level fall, and the climate might become warm and dry again.