The shelf margin delta is special dynamic delta which has much difference with normal deltas. The investigations can not only help to recognize the characteristics of deltas, but also guide petroleum exploration. The study area mainly focuses on Baiyun sag and Kaiping sag, within the Pearl River mouth basin, northern South China Sea. The interval of interest is the lowstand systems tract（LST） above the SB12.5 and the falling stage systems tract（FSST） below the SB12.5. Adapting Catuneanu systems tracts, utilizing a high-quality 3D seismic dataset, accompanying 2D seismic profiles and well logs, the morphology, architecture and genesis of deltas are researched in this study.
In the LST, the scale is large, the gradient is up to 3°and morphology appears bidirectional wedge in two directions. On well logs, deltas are represented by an overall coarsening-upward pattern. The margin delta mainly developed in the Kaiping sag, which has a maximum height of 200 meter, and range of 200 square kilometres. And it can divide into two stages. The early period is wave-dominated delta accompanied with the MTD. The later period is cotrolled by wave and fluvial, and scouring features can be observed in the western Kaiping sag. In the Baiyun sag, the delta is wave-dominated, whose scale is small, and seismic reflection is characterized by high amplitude and strong continuity. Most of progradations are generally E-W oriented, showing main sources located in north of the survey.
In the FSST, most of the characteristics are similar to the deltas in the LST. The margin deltas are developed apparently in two sags. In Kaiping sag, the distribution range is limited, and it’s wave-dominated, meantime, there is no slope fan developed downstream the delta. In Baiyun sag, delta has a maximum height of 200 meter, range of 200 square kilometres. The deltas are wave-dominated, and NE-SW oriented which also shows main sources located in north.
In conclusion, all the deltas are controlled by wave, and only in LST of Kaiping sag, there is slightly fluvial influence. However, the characteristics are different in two sags, mainly due to different main source. Moreover, the Yunkai Low Uplift also prevented the material transportation between two sags. Eventually, the shelf margin deltas developed are in fine physical properties, and can be favorable exploration targets.
Topics: Deltaic depositional systems , Topics: Shelf and shallow water sedimentation , Topics: Sequence stratigraphy
