摘要
本文系统地分析了南海西南海盆及其邻区的地球物理场特征，对比了海盆中的磁异常条带。将观测的地磁异常进行高通滤波，去掉层２Ａ下洋壳磁性体的影响，然后利用国际地磁年表中的地磁倒转极性事件，采用半扩张速率２．２￣２．５ｃｍ／ａ，在西南海盆对比出１８－１３号磁异常条带，对应的地质年龄为４２－３５Ｍａ。据此认定西南海盆是在晚始新世至早渐新世通过海底扩张形成的。作者基于地震剖面解释。
The characteristics of geophysical field in the SW Subbasin of South China Sea and adjacent area is systematically analysed and the magnetic abnormal lineations in the subbasin is correlated in this paper. By using high-cut filter, the observed magnetic abnormal data is fil- tered, thereby the effect of oceanic magnetic source rock below the layer 2A eliminated. Then referring the magnetic polarity events in the International magnetic age table and 2.2-2.5 cm /a of half-spreading rate, we have calculated and contrasted 18-13 magnetic abnormal lineations to the basin ,the corresponding geological age is 42 - 35 Ma. Therefore, we believe that the SW Subbasin was formed by sea floor spreading in late Eocene to early Oligocene. The seismic pro- file across the subbasin to be interpreted and found that there has the sediments from late Eocene to present in the subbasin, and late Cretaceous to present in it's continental margins. In middle of the Subbasin there has a graben, the interbed of basalt and sediment is filled in the bottom of the graben. The basalt was erupted into the surface after the sea floor spreading. After discussing the tectonic evolution history of the South China Sea in Mesozoic to Cenozoic and talked over the tectonic evolution history of the sedimentary basins in NW and SE margins of the subbasin,the author concludes that there have two kinds of basin in the SE margin: one is the rifting sedimentary basin formed in late Mesozoic to early Cenozoic similar with those sedi- mentary basins in the northern margin of the South China Sea; another one is the foreland basin formed after the collision of the Nansha Block and Kaliamantan-SW Palawan Block. So these basins were formed in the late Oligocene.
出处
《南海地质研究》
1997年第9期20-36,共17页
Gresearch of Eological South China Sea
关键词
南海
海盆
海底扩张
构造意义
海洋地质
:magnetic anomaly lineation, sea floor spreading, collision between the continents, rifting basin, foreland basin.
