山东灵山岛滑塌体内部沉积及构造特征研究

青岛市灵山岛修船厂剖面下白垩统地层中发育良好的滑塌变形体。野外观察可见滑塌体岩性单元主要由厚层砂岩及砂页岩互层组成,其中厚层砂岩根据其沉积构造及成因机制可分为砂质碎屑流沉积及浊流沉积两类;砂页岩互层段砂岩层可见底模构造及粒序层理,为静水环境下远端浊流沉积。滑塌体内部构造主要可分为软褶皱变形、同生断层、透镜状砂质团块三种类型。其中,软褶皱变形根据岩性可分为砂岩软褶皱、砂页岩互层软褶皱及页岩软褶皱,随着变形强度增加,软褶皱枢纽逐渐平行于滑移方向,形成曲脊软褶皱或软鞘褶皱(soft sheath folds);同生断层出现在砂岩层中,根据力学性质分为正断层及逆断层,正断层为剪切拉伸所致,逆断层为软褶皱逆冲所致;透镜状砂质团块包括同沉积布丁构造和同沉积断块。根据滑塌体内部滑移面识别出三期滑塌,完整的滑塌体由底部拆离滑移面、下部厚层砂体、中部砂页岩互层及上部砂页岩互层未变形体组成,其组成特征及各部分接触关系反映了滑塌体中下部沿底部拆离滑移面发生滑塌变形,且于活动末期在相对静水条件下被上部砂页岩互层覆盖这一形成过程。根据滑塌体内部组成特征的有序性、相似性及滑塌体内部沉积构造特征,推测其触发机制可能为沉积物快速沉积所引发的重力滑塌成因。

Qingdao Institute of Marine Geology, Qingdao, Shandong, 266071

Shipyard profile of Lingshan Island showed a very good exposure of slump bodies. According to field observation, the lithology unites consisted mainly of thick sandstone and interbedded sandstone and shale. Based on different sedimentary characters, the sandstones were thought to be formed by sand debris flow and turbidity flow. The interbedded sandstone and shale displayed sole marks and graded bedding, indicating far-end turbidity current in quiet water body. Slump folds, syngenetic faults and sandy lenses were the main structures in the slump body. Slump folds emerged in sandstone, interbedded sandstone and shale ,shale. With the strength of shear, the stretch of hinges of folds was parallel to the slump direction, forming curvilinear folds and soft sheath folds. The syngenetic faults consisted in the sandstone, forming both normal faults and reverse faults under corresponding strain mechanism. The sandy lenses consisted of synsedimentary boudinage and fault block. Three glide surfaces and slump bodies were recognized. An intact slump body was made of bottom glide surface, lower thick sandstone, mediate deformed interbedded sandstone and shale, upper undeformed interbedded sandstone and shale. The arrangement of slump bodies afforded a clue about the forming process of a slump body, i e, the lower and mediate parts slumping along the glide surface and covered by the upper part. On the basis of ordering and similarity ,the gravity slump of sufficient substances was suggested for the slump body.