FAST DETERMINATION OF BASIN'S PALEO-TECTONIC STRESS DIRECTION BY BALANCED CROSS SECTION——A NEW METHOD TO ANALYZE PALEO -TECTONIC STRESS DIRECTION

To determine the direction of paleo-tectonic stress is a very important matter for basin's paleo-tectonic stress field research.A new method has been brought forward to analyze paleo-tectonic stress direction.Firstly,the balanced cross section technique is applied to obtain basin's deformation rates in different directions during each geological stage.Then,the strain rosette method is employed to calculate principal stress direction in mechanics of materials.Further,basin's deformation rates in 3 different directions are equated with strain rosette's linear strains.At last,basin's paleo-tectonic stress directions are figured out using the relevant formulae from mechanics of materials.The directions of the 1st extensional principal stress during Laiyang,Qingshan and Wangshi stages in the Jiaolai Basin have been obtained by this method,approximately NE-SW,NW-SE and S-N respectively.These results accord with those from other traditional geological methods,illustrating the feasibility of the new method.Besides,the changing trend of deformation rates in sections with different directions can reflect basin's mechanical property,so this method is also helpful for analyzing basin type and basin-forming mechanism.Obviously,this new method is convenient and can fast produce results,and is not restricted by strata outcrop condition.