Discussion on the tectonic attributes of Oujiang Sag, East China Sea Shelf Basin

In order to make clear the tectonic attributes of the Oujiang Sag in the western part of the East China Sea Shelf Basin so as to guide and arrange the next cycle of oil and gas exploration in the region, on the basis of previously studies on the Mesozoic tectonic division and evolution, seismic profile interpretation, balanced profile analysis and land-sea correlation research are conducted in this paper. Comprehensive study shows that the Oujiang Sag is a faulted Cretaceous red basin in which the Jurassic is missing. The structural characteristics of faults, the Cretaceous sedimentary sequences and magmatic activities in the sag are similar to those observed in the Zhejiang-Fujian uplift belt. The Minjiang Sag to the east of Oujiang Sag is a Cretaceous and Jurassic fault-depression and transformation basin filled with marine-terrestrial transitional facies and marine facies deposits. On the seismic profile, the Minjiang Sag and the Jilong Sag in the east constitute an entirety inclined eastward. Sea-land correlation shows that both the Oujiang Sag and the Zhejiang-Fujian Uplift belt were uplifted and denuded in Jurassic, and suffered from faulting and extension in Cretaceous. Therefore, it is inferred that the Oujiang Sag has similar tectonic attributes with the Zhejiang-Fujian uplift belt, and could be regarded as a part of the Zhejiang-Fujian uplift belt, in which the Mesozoic oil and gas resources potential is worse than that in the Minjiang Sag.