高频海平面的波动与全球气候变化之间的联系,由于区域海平面升降指标、构造沉降、降雨和沉积物年代等诸多因素的困扰,长期难以达到统一的认识,影响全球变化的2个重要因子海平面升降和气候变化之间驱动与响应机制的讨论。以珠江三角洲3个代表性钻孔为例,基于旋回沉积学和磁化率值大小变化地层对比的基础上,以SX97钻孔记录的地磁倾角变化与从亚洲其它湖泊重建的地球磁场长期变化曲线相对比,确定沉积物的年代学框架。进而以环境磁学参数chi_(ARM) /SIRM为高频海平面波动的替代性指标,讨论珠江三角洲百年-千年尺度海平面变化与全球气候变化之间的联系。结果表明,珠江三角洲的初次海侵发生在约9. 2 ka BP,在9.1 ~7. 7 ka BP和4. 0 ~ 3. 2 ka BP分别存在2个高海平面阶段,几次显著的低海平面时期,如1. 2 ~ 1. 5,3 ~ 3. 2,4.0~4.75, 5. 25 ~5. 75, 6.2 ~6. 3和7. 25 ~7.75 ka BP与全球变冷事件或东亚夏季风的减弱相一致,说明在全球尺度,高频海平面的波动与全球气候的变化存在同步响应的特征。
英文摘要:
High frequency sea-level fluctuations and their response to global change in the Pearl River Delta, adjacent to South China Sea, is still an open question due to uncertain dating and complicated facies changes. In this paper, we correlate the sediments of three cores, selected from the delta, using magnetic susceptibility stratigraphic and cycle stratigraphic methods. The geomagnetic inclination change recorded in sediments of core SX97 is compared with the geomagnetic paleosecular variation profiles recorded in sediments from the Shuangchiling Lake in Hainan Island, Erhai Lake in Yunnan province and Biwa Lake in Japan. Based on this correlation, age-depth models of three cores are then established. The magnetic grain size indicator chi_(ARM) /SIRM, coeval with the susceptibility, is used to serve as a proxy of sea-level fluctuations during the Holocene. Two high sea-level episodes occur at 9. 1 - 7. 7 ka BP and 4. 0 -3. 2 ka BP, and several sharp sea-level falls appear at about 1. 2 - 1. 5 ka BP, 3 -3. 2 ka BP, 4. 0 -4. 75 ka BP, 5. 25 -5. 75 ka BP, 6. 2 -6. 3 ka BP and 7. 25 -7. 75 ka BP, corresponding to impacts of cold climate in the North Atlantic and weakened monsoonal activity in Asia, respectively.