榆社群高庄组中震积泄水构造及成因模式

位于华北克拉通中部、沁水含煤构造盆地核心部位的榆社盆地，是一个上新世至早更新世河湖相沉积的内陆小型盆地，浊漳河的侵蚀导致大量新生界剖面出露地表。野外地质调查发现，榆社群高庄组中发育大量泄水构造，包括砂泥岩脉、砂岩脉、泥岩脉、粘土质团块、片状钙质胶结岩脉、结核等，且相互间渐变过渡。基于饱和松散岩土体，在大于一定强度的外动力扰动下，沿岩层软弱结构面发生逃逸，形成泄水构造。基于泄水构造在本区大范围发育的调查结果以及现代地震诱发砂土液化的研究成果类比可知，地质历史时期的高庄组沉积物（地震发生时高庄组沉积物处于饱和松散状态、中值粒径变化范围在0.055~0.159mm区间、级配良好且富含CaCO3，FeO和MnO等矿物质），是在遭受地震震级MS=5~6的动力扰动下，沿岩层弱面泄水灌入形成了上述泄水构造。地表揭露的各种震积构造关联证据与地震导致饱和松散岩土体液化射流的水动力以及粘粒、砂粒、矿物质等物源供应量变化的形成条件相匹配，构建了表征其成因的“地震液化射流分异模型”。地震液化射流形成不同形态的泄水构造，可作为相变剧烈小型盆地地层识别与对比的良好标志。

INVESTIGATION ON SEISMIC WATER ESCAPED STRUCTURE AND GENETIC MODEL FOR GAOZHUANG FORMATION OF YUSHE GROUP

Yushe basin, located in the central North China Craton and the center of Qingshui coal-bearing basin, is a small scale Pliocene to Early Pleistocene fluvial-lacustrine basin and good outcrops of Cenozoic strata were exposed by erosion of Zhuozhang River. Many water escape structures, including sand-mud vein, sandstone vein, mud vein, mud ball, calcium sheet, concretion, and the gradual transition characteristics among them were observed in Gaozhuang Formation of Yushe Group. Based on theory that when the intensity of outer dynamic disturbance is larger than a threshold, saturated and loose rock mass will escape along the soft rock structural plane and form the water escape structures, and in comparison with the water escape structures induced by contemporary earthquakes, it was suggested that the water escape structures in Gaozhuang Formation were formed along the soft rock structural planes by a MS5~6 earthquake under the condition that sediments were saturated and loose, with 0.055~0.159mm median diameter, good gradation and abundant CaCO3, FeO, MnO minerals. A genesis model, called as earthquake-induced liquefaction jet differentiation model, was proposed according to the matching of the seismic structures in the outcrops with water power of earthquake-induced liquefaction jet for saturated and loose materials and the distribution of clay particle, sand particle and minerals in strata, which controls the supply of material for formation of various water escape structure. Different water escaped structures formed by earthquake liquefaction jet could be acted as the good symbols of strata identification and correlation in small scale basin with fierce face transformation.