【摘要】 中国广东沿岸作为一个冰川均衡调整(GIA)“远场”地区,按照水动型均衡理论,应存在全新世中期高海平面。本文通过海平面标志物重建了广东古海平面的历史,结果显示出在粤东、粤西与珠江三角洲的海平面历史存在明显的差异。若将海平面历史与GIA模型结果对比,可以看出广东沿岸在全新世以来具有微小的区域性地壳沉降。这种大区域的沉降可归因于华南陆块向南延伸所引起。此外,粤西雷州半岛因新构造运动,于全新世早中期有轻微抬升。珠江三角洲盆地则因断裂构造沉降和沉积物压实作用,重建的中全新世海平面明显低于GIA结果。更多还原

【Abstract】 This study aims to investigate the influence of tectonic activity in the Holocene sea-level records.The coast of Guangdong was selected because of its active tectonics during the Late Quaternary.Due to the fact that the tectonic movement during the Holocene has been very small in magnitude,a careful sea-level reconstruction is needed.With the high precision reconstruction,this study is able to reveal some important features of tectonic movement and evaluate its impacts on the sea-level history.Most important in sea-level reconstructions is the ability to precisely determine the vertical relationship(also called indicative meaning) of a sea-level index point to its associated reference water levels.This study employed a scheme to help quantify this relationship for 15 types of sea-level indicators,which are commonly obtained from this coast.Once the palaeo-sea-level height was established by the above method,a sea-level curve for a small area was developed.To identify tectonic component within the sea-level records,the newly developed global eustatic history and a laterally heterogeneous earth model coupled with a deglacial model were used to generate predictions for the Holocene eustatic sea-level history and the effects of glacial-isostatic adjustments(GIA) for the study area.A comparison between the reconstructed sea-level history and the GIA history shows valuable information about the influence of tectonic movement.Results show that along the west coast of Guangdong there are few good quality sea-level data for the period before 7700 year.A group of high quality data from coral samples of Leizhou Peninsula suggests a small magnitude of uplift,whilst data from estuarine environments of this coastal area show the coast was tectonically stable and the GIA was the main process that determines the mid-late Holocene sea-level history.Within the Pearl River deltaic basin,sea-level data suggest subsidence and possible sedimentary compaction.Further study is needed to quantify the tectonic component in the sea-level history.In the case of East Guangdong,the sea-level data scatter around the eustatic sea-level curve,with some data points(in Mid-Holocene) appearing below the eustatic curve and some others(in Late Holocene),above the GIA curve,implying a complex history of tectonic movement.This study concludes;(1) The Guangdong coastal area in general has experienced a slight subsidence during the Holocene,possibly a result of the long-term continental extension that has caused the subsidence of northern continental shelf of the South China Sea;(2) Due to a change of the stress field in Late Quaternary,many NW-SE faults became active in this coast,resulted in differential,local subsidence and uplift,with estuaries and deltaic basins being mainly subsiding;(3) Leizhou Peninsula,an tectonically active area with the Hainan Island,shows evidence of uplift during the Holocene,reflecting the fact that this area has a long history of volcanic activity and earthquake throughout the Quaternary;(4) The data from the Pearl River Delta may show a combination of tectonic subsidence and sedimentary compaction due to dewatering of the sedimentary sequence.更多还原