南极威德尔海沉积盆地重力异常特征

Gravity anomaly characteristics of sedimentary basin of Weddell Sea in Antarctica

本文将卫星重力数据与威德尔海船测重力数据进行对比验证,利用Parker方法获取威德尔海沉积盆地布格重力异常;在此基础上建立沉积盆地模型,计算莫霍面补偿效应和沉积过程的重力效应比值,探索威德尔海沉积盆地重力异常与波长之间的联系;采用Airy-Hesikanen均衡模型计算均衡异常,探讨海陆边界的均衡状态.结果表明:(1)威德尔海沉积盆地布格重力异常值随波长变化呈现不同特征:波长为200~600 km(对应沉积盆地宽度为100~300 km)的布格重力异常主要呈现正值,而波长为80~200 km(对应沉积盆地宽度为40~100 km)的布格重力异常主要为负异常.(2)基于沉积盆地模型分析表明,威德尔海沉积盆地重力异常正值可能并不是由地壳长期底侵作用形成,而是沉积作用与裂隙作用共同导致的结果.(3)威德尔海沉积盆地边界的均衡重力异常表现为高负值,反映了威德尔海盆地沉积过程与冰架排挤系统有关.

The latest gravity data calculated from satellite altimetry are tested and verified by the marine gravity data collected in Antarctic Weddell Sea,and the Parker forward method is used to obtain the Bouguer gravity anomaly in the Weddell Sea sedimentary basin.In order to explore the relationship between gravity anomalies and wavelength in the Weddell Sea sedimentary basin,a sedimentary basin model is established to calculate the ratio of the gravity effects of the Moho compensation to sedimentary process.Further,Airy-Hesikanen isostatic model is used to calculate the isostatic anomaly and explore the isostatic state of the boundary.The results show:(1)The Bouguer gravity anomaly in the Weddell Sea sedimentary basin has different characteristics with wavelength changes:the Bouguer gravity anomaly with a wavelength of 200~600 km(corresponding to a sedimentary basin with a width of 100~300 km)is mainly positive,while the wavelength is 80~200 km(corresponding to a sedimentary basin with a width of 40~100 km),the Bouguer gravity anomaly is negative.(2)Further analysis based on the gravity anomaly model of sedimentary basins with varying flexural rigidities shows that the positive gravity anomaly in Weddell Sea may be not formed by the long-term underplating in the crust,but the interaction between sedimentation and rifting.(3)The isostatic gravity anomalies of the sea-land boundary in this region presents high negative values,reflecting that the sedimentary process of the Weddell Sea Basin is related to the ice shelf displacement system.