叠加于弧后前陆盆地挠曲沉降之上的另一类沉降--动力沉降

Dynamic subsidence, another kind of subsidence superposed on flexural subsidence of retroarc foreland basin.

弧后前陆盆地挠曲沉降包括逆冲负载沉降和盆地沉积物负载沉降。叠加于挠曲沉降之上还存在另一类沉降,即动力沉降。动力沉降是动力地形的一种,即动力地形低。动力地形一般认为具有两种成因,一种为与超大陆集聚和分散有关的动力地形,另一种为与大洋板片俯冲有关的动力地形。由大洋板块俯冲产生的动力沉降往往分布于弧后前陆盆地区,其幅度、波长与板块俯冲角度、俯冲速率、俯冲板块在地幔中通过的位置和俯冲岩石圈的热年代密切相关。将通过弧后前陆盆地沉积地层的去压实得到的总沉降减去盆地模拟获得的逆冲带负载和盆地沉积物负载沉降可以得到剩余沉降,即动力沉降。从地层资料中定量分离出动力沉降为改进和限制长期以来悬而未决的由洋壳俯冲导致的地幔-粘性流动构造模型提供理论基础和实际资料。

The flexural subsidence of retroarc foreland basin includes those driven by thrust load and by basin sediment load. There is another kind of subsidence, the dynamic subsidence, superposed on the flexural subsidence. The dynamic subsidence is one of dynamic topography, that is, the dynamic topography low. It is generally thought that the dynamic subsidence is associated with supercontinental assembly and dispersion or with subducting slabs. The dynamic subsidence generated by slab subduction could be recognized in the retroarc foreland basin, and its amplitude and wavelength are related with slab dip, subducting rate, slab penetration distance within mantle and slab thermal age. The dynamic subsidence can be calculated by the difference between the observed, decompacted, cumulative subsidence and the amount of subsidence that can be explained by simple flexural loading in a retroarc foreland basin. The quantification of dynamic subsidence from back stripped stratigraphic data may provide a theoretical base and data for improving and constraining the current global model for the mantle-viscous flow, which has not been clarified for a long time.