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吉中西保安期地层分布在敦密断裂以北，认为是该区古华北大陆板块北部褶皱带中最下部层位，为一套火山—沉积岩系。从建造组合及岩石化学等方面均反映该期为拉张型被动大陆边缘。该被动陆缘大致有三个连续的演化过程。推测它是在元古早期泛大陆基础上，由裂谷作用和地壳拉伸减薄作用下形成的，属拉张型过渡壳。
The Jixi-Xisi security period strata are distributed to the north of the Dun-Mi fault and are considered to be the lowest volcanic-sedimentary rock series in the northern fold belt in the northern part of the paleo-North China Plate. From the construction and petrochemistry, etc. all reflect the period of tension-type passive continental margin. The passive continental margin has roughly three consecutive evolutionary processes. It is presumed that it was formed on the basis of the Pan-Continent during the Proterozoic and was formed by the rifting and the thinning and crustal crustal extension.