Sedimentary characteristics and genetic mechanism of the giant ancient pockmarks in the Qiongdongnan Basin, northern South China Sea

In the late Miocene, giant ancient pockmarks, which are fairly rare globally, developed in the Qiongdongnan Basin. In this paper, to determine the sedimentary characteristics and genetic mechanism of these giant ancient pockmarks in the Yinggehai Formation of the Qiongdongnan Basin, based on high-resolution 3D seismic data and multiattribute fusion technologies, we analyzed the planar distribution and seismic facies of the ancient pockmarks and compared the characteristics of the ancient pockmarks with those of channels, craters, and hydrate pits. Moreover, we also discussed the implications of the fluid escape system and paleo-bottom current activity in the ancient pockmark development area and analyzed the influence of the ancient pockmarks on the paleoclimate in this region. Finally, an evolutionary model was proposed for the giant ancient pockmarks. This model shows that the giant ancient pockmarks in the southern Qiongdongnan Basin were affected by both deep fluid escape and lateral transformation of paleobottom currents. In addition, the giant ancient pockmarks contributed to the atmospheric CO 2 concentration in the late Miocene and played a great role in the contemporary evaluation of deepwater petroleum exploration.