莺歌海盆地前新生代基底特征

Basement characteristics of Yinggehai Basin in pre-Cenozoic

结合盆缘露头、盆地基底钻井及重磁震资料,综合研究莺歌海盆地前新生代基底特征。基于盆地西北缘Song Da带18个剖面点地层序列、166件岩石样品密度和2 800套磁化率测量结果,建立密度--磁化率交汇图版,约束盆内地震剖面和重磁异常解释,通过海陆结合的方法填制出盆地基底地质图。其前新生界由前震旦系、寒武系—上三叠统下部、上三叠统上部—白垩系三个构造层构成,它们沿红河断裂呈北西向分布,中间老,为前震旦纪中—高级变质岩;两侧新,向西为中生代沉积岩,向东为古生代浅变质岩、灰岩。

Combining basin margin outcrops with basement drilling and geophysical data, a comprehensive study is conducted on the basement characteristics of basement in Yinggehai Basin for pre-Cenozoic. Based on the sequence stratigraphic data of 18 outcrop sections, density data of 166 rock samples, and 2 800 sets of magnetic susceptibility data collected from the Song Da zone at the northwestern margin of the basin, a density-magnetic susceptibility crossplot is constructed. These data additionally provide geological constraints for the interpretations of the seismic profiles and geophysical anomalies within the basin. A basement geologic map is subsequently drafted with a combination of marine and terrestrial perspectives. The pre-Cenozoic basement is composed of Presinian, Cambrian-lower Upper Triassic, and upper Upper Triassic-Cretaceous. Spatially, they distribute along the Red River fault zone in a NW orientation. Chronostratigraphically and lithologically, they are characterized by a gradual aging trend from the middle to the two sides, and by a lithologie pattern of Mesozoic sedimentary rocks at west and Paleozoic epi-metamorphic rocks at east.