- 责任者：Liu Haichao (Key Laboratory of Orogenic Belts and Crustal Evolution ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Ji Jianqing
- 刊名：Chinese Journal of Geology
- 出版年：2013
- 卷期：48(3)
- 关键词：重力异常 ; gravity anomaly ; 喜马拉雅山 ; Himalayas
- 页码：p.693-706
- 图表：4 illus., 48 refs.
- 分类号：0400
- issnNo：ISSN0563-5020
- isbnNo：CN11-1937/P
The isostatic gravity anomalies (IGA) on the southern margin of the Tibetan Plateau can be divided in to the quasi-isostasy zone of the plateau, positive IGA zone of the Himalayas and negative IGA zone of the foreland basins, which two forms the spectacular mirrored symmetry on gravity anomaly maps. This paper chooses the IGA data in central and eastern Himalayas and its foreland basins, together with some fundamental geological data on the relief, crustal thickness, precipitation, glacier and sedimentary thickness, to discuss and understand the relationship between the formation of the isostatic gravity anomalies and morphology differentiation. Profile analysis shows that the positive isostatic anomalies in the Himalayas are clearly coupled with regions that are strongly denuded by glacier and rivers, but have no direct relationship with the distribution of precipitation. Also, the negative isostatic anomalies in the foreland basins are clearly coupled with the Cenozoic sedimentary thicknesses, especially with the thicknesses deposited since mid-Miocene. Estimation of the denudation thicknesses indicates that the positive isostatic anomalies in the Himalayas are mainly caused by the under- compensated crust beneath the mountains （the Airy model）, while the negative isostatic anomalies are mainly caused by the distribution of the Cenozoic low density deposition （the Pratt model）. Numerical calculation is then carried out to get the isostatic adjustment time which is on the time scale about 1 Ma for the Himalayas. The comparison result with the landscape response time indicates that just because the morphology evolution is faster than isostatic adjustment, the crust＇s adjustment couldn＇t response the continuous denudation in the ranges and the continuous deposition in the basins to form a ＂mountain root＂, which result in the ＂anti-isostasy＂ movement of the lithosphere to form the spectacular distribution of the isostatic gravity anomalies since about 2.5 Ma on the southern margin of the Tibetan Plateau.