Publikationsdatum:
2017-02-16
Beschreibung:
A series of confirmed and suspected dammed palaeo-lake sedimentary successions is scattered within the middle Yarlung Tsangpo valley in Tibet. However, the chronology, the genesis of the dam and its location, the water level of the dammed lake, the process of dam failure and the spatiotemporal relationships between the sedimentary successions remain controversial. Here, we focus on one sedimentary succession of the suspected dammed palaeo-lake at Xigazê. We measured the grain-size distribution, magnetic susceptibility, organic and inorganic carbon content, and δ 13 C org and δ 15 N total ratios of the sediments. In addition, we measured the δ 18 O shell and δ 13 C shell values of modern and fossil Radix sp. shells, and the δ 18 O water and δ 13 C DIC values of the ambient water with different hydrological regimes. The results indicate that the δ 18 O shell values of modern Radix sp. and the δ 18 O water of the ambient water body significantly depend on its hydrological status. In addition, a strong positive relationship was observed between δ 18 O shell values of modern Radix sp. shells and the δ 18 O water of the ambient water on the Tibetan Plateau. According to this correlation, the δ 18 O water values of the palaeo-water body are reconstructed using the δ 18 O shell values of Radix sp. fossil shells in the Xigazê section. Further, based on the δ 18 O shell values of fossil Radix sp., the reconstructed δ 18 O water of the palaeo-water body and the specific habitats of Radix sp., we infer that the sedimentary succession in the Xigazê broad valley was mainly formed within the backwater terminal zone of a dammed palaeo-lake and that the elevation of the water level of the lake was approximately 3811 m a.s.l. AMS 14 C dating indicates that the deposits of the dammed palaeo-lake were formed at about 33–22 cal. ka BP. Finally, the presence of Radix sp. fossil shells within the Xigazê section suggests that Radix sp. survived the late Last Glacial Period on the Tibetan Plateau.
Print ISSN:
0300-9483
Digitale ISSN:
1502-3885
Thema:
Geographie
,
Geologie und Paläontologie
Permalink
