摘要
In this paper, a tectonic framework with zonal array in NS direction and block division in WE direction was established in deepwater area of Qiongdongnan Basin (QDNB). A key tectonic revolutionary boundary, T70, was identified in QDNB by integrated analysis of tectono-stratigraphy, subsidence history and subsided depocentre migration. Analyses of genetic type and geometry of basin-boundary fault indicate that NW-SE extensional tectonic stress field strongly controlled development of small distributed NE-trending faulted basin group underlying T70 boundary, and nearly SN extensional tectonic stress field resulted in formation of fault-sag basin over this boundary. The evidence of regional and biostratigraphical correlation shows that the age of this boundary is 32 Ma, which is consistent with the time of initial spreading of South China Sea. Thus T70 boundary is a regional tectonic revolutionary boundary.