关键词: 三维反射地震, 塔里木, 大陆溢流玄武岩(CFB), 火山机构, 强制褶皱

Abstract:

The volcano edifices from Tazhong-47 exploring area in the middle of Tarim basin are interpreted by 3-D seismological reflection data coupled with physical drilling well logs. Based on seismic profile interpretation and velocity analysis, the structure of the volcano edifices of continental flood basalt (CFB) are studied. The result shows that reflectors beneath the Tazhong-47 volcanic edifice are corresponding to basaltic intrusions, which have average velocity of 5800 m/s, and the clastic wall rocks have average velocity of 3500 m/s. Based on the calculation of the stratigraphical thickness between the two horizontal markers (Permian-Triassic boundary as named “P-top” and top of bioclastic limestone as named “BL-top”) at drilling well, it is found that the basaltic intrusions make the upper layer relative to the lower layer marks move the 159.1 m upward. This is equal to the uplift extent. By using the “velocity pull-up (VPU)” effect, the total thickness of the basaltic sills is calculated to be 167.7 m, which is similar to the uplift extent. This similarity suggests that the uplift at the volcanic center was the result of “forced folding” caused by the intrusion of the magma. This emplacement style is the same as that of the Karoo large igneous province and the North Atlantic igneous province.

Key words: 3-D reflection seismology, Tarim, continental flood basalt(CFB), volcanic edifice, forced folding