Characteristics and petroleum geological significance of pre-Sinian rifts in the Sichuan Basin and its periphery
It has been confirmed that large-scale pre-Sinian rifts are developed in the periphery of the Sichuan Basin,but the distribution and development characteristics of the pre-Sinian rifts within the basin have not been clarified,which,to some extent,restricts the understanding on the deep structural pattern of the basin.On the basis of previous researches,combined with the latest gravity,magnetic and electrical data,this paper studies the Neoproterozoic structural pattern by means of combined interpretation,small subdomain filtering and other new technologies.Then,it is verified by virtue of the fine interpretation of regional seismic section as well as the aeromagnetic data.Finally,the characteristics of the Neoproterozoic rifts and the control effect of the rifts on the sedimentation of overlying strata are analyzed.And the following research results are obtained.First,there are three nearly parallel pre-Sinian rifts developed from northwest to southeast within the Sichuan Basin,among which,the one in the central Sichuan is the largest in scale.Second,a series of secondary normal faults which are nearly parallel to the strike of the rifts are developed within the rifts,and they complicate the structures inside the rifts to form a series of fault depression.Third,on the plane,the faults within the rifts are in the patterns of parallel/oblique,synthetic/opposite parallel and concordant parallel combination,which correspond to the combination characteristics of stepwise,horst-graben type,graben type and half graben type on the profile.Fourth,the outcrops along the northeastern margin of the Sichuan Basin reveal the development of the glacial-interglacial alternating sedimentation in the rifts during Nanhua-Doushantuo period,which is mainly composed of clastic rock and tillite of delta,continental shelf and slope basin facies.In conclusion,the new method of gravity and magnetic interpretation+well-seismic data modification+outcrop section verification confirms that there are pre-Sinian rifts in the Sichuan Basin,the boundary(main)faults of Nanhua rift control the sedimentary paleogeographic pattern of the overlying strata and the development of slope break zones,and some rifts control the distribution of sedimentary centers in the Cambrian or Early Paleozoic,which have an extremely important effect on the formation of later subsidence centers and structural traps and the petroleum systems.
Sichuan BasinNeoproterozoicPre-SinianGlacial-interglacial sedimentationUltra deep explorationGravity and magnetic interpretationStructural stylerift distribution
万方数据
维普
