In the southwest and west parts of the Nansha Waters, the Paleogene sediments have suffered from strike-slipping extension and compression, and are comprised of the main oil source rocks in numerous large traps over the area.

• 南沙西南及西部的下第三系受到走滑、拉张和挤压的影响，构造复杂，圈闭多，规模大，是主要的生油和储集岩层。