南极半岛和东南极间南威德尔海陆架的地壳结构

A NOTE ON THE CRUSTAL STRUCTURE BETWEEN THE ANT- ARCTIC PENINSULA AND THE EAST ANTARCTIC CRATON ACROSS THE SHELFOF THE SOUTHERN WEDDELL SEA

重力资料结合磁性体埋深计算和地震折射资料的分析 ,表明在南极半岛和东南极克拉通之间的菲尔希内尔和罗纳冰架之下存在一减薄的地壳。推测该区地壳的减薄主要由南极半岛和东南极克拉通之间的近东西向拉张作用所造成 ,该作用很可能发生在陆架盆地发展的早期。

On the basis of analysis of gravity data across the shelf between the Antarctic Peninsula and the East Antarctic Craton,constrained by magnetic depth estimates and a few seismic refraction data ,the paper is dealing with the crustal structure of southern Weddell Sea and its evolution. The free air gravity anomaly across the shelf of southern Weddell Sea ranges between -10～-50×10 -5 m/s 2,a relatively higher gravity anomaly with the amplitude of 10～20×10 -5 m/s 2 occurs in the middle of shelf. The water depth along the cross-section varies from 400m to 600m with no abrupt changs,except the southeast side where the water is nearly 1000m deep. The geophysicalsurvey indicated that there is a large sedimentary basin under the Ronne and Filchner Ice Shelves,the depocenter being in the middle of basin with a maximum sediment thickness if 10 km. In Airy-Type isostatic equilibrium, a possible 2-D model for the crustal structure under the shelf of southern Weddell Sea is proposed. A particular feature of the model is the requirement for a thinned crust below the sedimentary basin. The younger part of the sedimentary section does not display significant evidence of extensional tectonics. So it is suggested that extension of the crust must therefore have occurred at an early stage of basin evolution or the upper part of the sedimentary section is very young.