鄂西奥陶纪两河口期碳酸盐台洼中重力沉积

GRAVITY-DISPLACED DEPOSITS OF LIANGHEKU STAGE (ORDOVICIAN) IN THE INTRAPLATFORM DEPRESSION, WESTERN HUBEI

本文将鄂西奥陶纪两河口早期碳酸盐台洼中重力沉积划分为6种类型:(1)塌积角砾岩;(2)滑动变形岩块;(3)滑塌砾屑灰岩;(4)碎屑流砾屑灰岩;(5)颗粒流含砾砂屑灰岩;(6)近源浊积灰岩.并指出这套重力沉积经历了三个演化阶段:①岩崩塌积阶段;②重力流发育阶段,③重力流衰减阶段.研究结果表明:鄂西低起伏碳酸盐台洼中重力沉积发生在海侵背景下,主要受同生构造活动控制.

In Early Lianghekou stage(ordovician),a series of gravity-displaced deposits developedin the western Hubei carbonate platform of Yangtze passive continental margin. Six types are recognized: (1)collapse breccia; (2)slide deformation block;(3)slump calcirudite; (4)de-bris flow calcirudite; (5)grain flow pebbled calcarenite;(6)proximal turbidite. These gravity-displaced deposits experienced 3 evloution stages:①avalanche-collapse stage;②gravity flow developping stage; ③gravity flow decay stage. The characteristics of sedimentary type and space-time distribution of the gravity-displaced deposits suggest that these deposits taken place in the low-relief carbonate intraplatform depression, on the background of a transgression in Early Lianghekou stage, which were mainly controlled by synsedimentary structural action. The western Hubei intraplatform depression was filled and levelled by carbonate deposits in Middle Lianghekou stage, thus concluded history of gravity-displaced deposits in the intraplatform depression.