【摘要】 在塔里木盆地于奇地区上三叠统的大套泥岩中发现了一个由低速泥岩形成的自东向西的叠瓦状前积地震反射,它本身由三个朵叶体组成,每个朵叶的面积约为30～45km2,厚度为15～20m。如今有三口钻井揭示该前积反射为较低速深灰色纯泥岩所形成,发育于较高速的深灰、暗褐灰色含钙质泥岩背景中。前积体反映的古沉积斜坡坡度约为2.1°。因沉积背景为半深—深湖相,故该前积体可能为湖底泥质重力流沉积。在该区北部靠近轮南断裂附近下降盘相同层位还存在一个自北向南的前积反射,YQ2井揭示该前积体也由低速泥岩构成。更多还原

【Abstract】 An imbricateed progradational reflection caused by low velocity shale is found in Upper Triassic thick massive mudstones.It flows westward and consists of three irregular planar oval shaped lobes,each with 15~20m thick and 30~45km2 sizes.Three borehole data reveal that it is dark grayish pure shale and sandwiched within a background of dark grayish and brown-grayish calcareous claystone.The progradational reflection indicates a clinoform of 2.1 degree of ancient depositional surface.As the depositional background is deeper lacustrine environment,the progradational reflection may be muddy gravity flow deposits.Another similar southward progradational reflection occurred in the same horizon.It is close to down-thrown block of Lunnan Fault,a tectonic fault as the southern boundary of Saya uplift.Well YQ2 located at the southern frontier of the reflection reveals that the progradtional reflection is also caused by a low velocity of shale.Despite seen rarely,shale progradations are seldom found on outcrops.Lack of coarse sediment may be consequence of fine lilthology of eroded source area.更多还原