Abstract：To determine the active patterns and controlling factors of faults in the southeast Wulungu depression at Early Mesozoic period,the growth index of faults may reflect the fault activity by determining the axial surface and composition of fault propagation fold caused by synsedimentary reverse fault,therefore the Early Mesozoic growth index of faults in the triangular region of the northeast Wulungu depression between Hongyan step fault zone and Luliang uplift has been analyzed. In the sedimentation stage of Upper Triassic Baijiantan Formation( T_3b),the growth index of Wudong fault is generally about 1. 5,Hongpen fault is usually under 1. 3,and Kalasayi fault is mostly under 1. 2. In the sedimentation stage of Lower Jurassic Badaowan Formation to Middle Jurassic Xishanyao Formation( J_1b-J_2x),the maximum growth index at the sedimentation stage of Lower Jurassic Badaowan Formation( J_1b) attaches to Wudong fault,at the sedimentation stage of the Lower Jurassic Sangonghe Formation( J_1s) attaches to Hongpen fault,at the sedimentation stage of Middle Xishanyao Formation( J_2x) attaches to Kalasayi fault. In the direction of strike,the growth index of Hongpen fault and Kalasayi fault approaches to 1 in the extreme southeast( or east),gradually increases northwestward( or westward),then decreases to 1. The activities of Wudong fault,Hongpen fault and Kalasayi fault have the characteristic of piggyback propagation from northeast to southwest not noly at the sedimentation stage of Baijiantan Formation( T_3b),but also at the sedimentation stage of Badaowan Formation to Xishanyao Formation( J_1 b to J_2x),which also indicate the tectonic dynamic derived from the northeast to the Wulungu depression. The change rule of the above growth index is not only related to fault attribution of different fault systems,but also related to the distance between them. The growth index of Kalasayi fault displays even big difference in the direction of strike,which owes to the combination of other faults.

Keyword：growth index;tectonic migration;Wulungu depression;Mesozoic;