The middle- to late-Miocene South China Sea might be occlusive continent edge sea which communicates with the Philippine sea and Pacific ocean only by Bashi Channel, which sometimes opened and sometimes closed, and when, apart from deep sea in central South China Sea basin, all Dongsha, Zhong-Xisha, and Nansha were shallow sea, bank, or lagoon.4.

中—晚中新世南海曾一度是一个以巴士海峡为开口,与菲律宾海及太平洋时而相连,时而断开的封闭的陆缘海。 因此,除中央海盆水体较深外,东沙、中-西沙和南沙等海域水体均较浅,浅滩和泻湖发育。