The alternation of Quaternary Glacial Period and Interglacial Period led to very strong sea level fluctuation, and the coastline in the east and south of China could advance and retreat for hundreds of kilometers. When the sea level rises during the interglacial period, seawater can reach Baiyangdian Lake, Hongze Lake and Taihu Lake in the east, and Leizhou Peninsula in the south can be submerged at the bottom of the sea. The lowest sea level drop during the ice age is about 1.50m below the present sea level. The Bohai Sea, the Yellow Sea, the East China Sea and the northern part of the South China Sea are all vast coastal plains, and ancient soil, weathered crust and peat may also be formed. At that time, Taiwan Province Province was directly connected with the mainland, and terrestrial organisms were free to travel. About 6.5438 million years ago (after the last ice age melted), the sea level gradually reached its present position.

Figure 10-8 Schematic diagram of Pleistocene sediment profile in North China Plain

(According to China Paleogeographic Atlas, quoted by Liu Benpei, etc., 1996)