Typical Fill Sequences in Jurassic Basins in the Northwest Region of China
西北地区侏罗系盆地典型充填序列

The northwest region refers to the vast tracts west of the Helan Mountains in China.At the end of the Triassic,a low mountain_hill_dominated geomorphology with a relatively small elevation difference was formed.There,a series of continental sedimentary basins of varying sizes are distributed.The fill sequence of a basin may be understood as an entirely vertical depositonal sequence developed in the basin.This sequence is made up of several rock associations which appear in a certain order.The alternation of sedimentary systems displays the stages of tectonic evolution and processes of subsidence and deposition and their quantitative relationship.Jurassic sedimentary sections in different tectonic positions of the northwest region are selected in the paper to make an analysis of the fills and determine the major fill sequence types and the sedimentary model.It may been found clearly that there are both general characters and differences in the vertical depositional sequerrces of the basins in different tectonic units of the northwest region of China.