Environmental Changes and Ostracoda in the Chen Co Lake of Southern Tibet in Recent 1400 Years
藏南沉错地区近1400年来的介形类与环境变化

The CC1 core, with a length of 216 cm, was drilled in the western part of Chen Co Lake in Tibetan Plateau. The 210 Pb and 137 Cs test indicated that it was a continuous sedimentary sequence since ca. 1400 years. A total of 15 species of ostracodes belonging to 7 genera in the core sediments had been identified. The ostracoda assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes as follows: (1) from the end of the 6th century to the 1370s Chen Co was a deeper water lake. The replenished water that flew into the lake increased obviously and the lake water deepened during ca. 708-780 AD; (2) from the 1370s to the 1890s Chen Co gradually became a shallow water lake. However, the lake level still experienced intensive fluctuation in this period. The lake water impetus was stronger in two stages from ca. 1454 to 1525 AD and from ca. 1803 to 1891 AD, during which sediments were subjected to disturbance, transportation and redeposition. The lake shrank and became a shallow water environment. During the stage of ca. 1645-1670 AD the lake environment deteriorated, which led ostracoda fauna not to be able to live. The lake level rose while the depth of the lake increased relatively during ca. 1731-1803 AD; and (3) from the 1890s to the present Chen Co had evolved from a deeper water lake before the mid-1960s to a shallow one at present. The lake had been shrinking since the mid-1960s and became a shallow water lake environment.