An Analysis of Superposed Deformation and Tectonic Stress Fields of the Western Segment of Daba Mountains Foretland

The typical superposed deformation developed in the western segment of Daba Mountains foreland,which records distinctly its history of tectonic evolution and is beneficial to research on tectonic regimes conversions.Based on analysis of folded forms croped out in the region,combined with observation of bedding plane and fault slip vector,in this paper,we study in detail on two main periods of Mesozioc tectonic compression stress fields,near SN-trending compression during T3—J1 and near EW-oriented compression during J3—K1.At earlier stage(T3—J1),controlled by near SN-trending compression tectonic stress field,a series of near EW-trending folds formed at Daba Mountains,which may be caused by Indosinian movement.At later stage(J3—K1),the tectonic regime changed to near EW-oriented compression,therefore,earlier near EW-trending folds was deformed strongly,and a series of SN-oriented folds developed.Thus,superposed folds of Daba Mountains foreland formed.At the same time,Fangxian—Zhenba fault zone thrusted intensitily westward.The later deformation of Daba Mountains may resulted from Yanshanian Movement.To study on superposed deformation of Daba Mountains bears on importance for research on blocks interaction in this region,and takes an instructive action on oil and gas of the Northern Sichuan.