泌阳凹陷深凹区核三上亚段浊积扇成因及沉积模式

Genesis of Turbidite Fan and Depositional Model in the Upper Member of Eh_3 of Deep Area of Biyang Depression

通过对泌阳凹陷深凹区核三上亚段岩性组合、粒度分析和地震反射特征等方面的研究,认为深凹区滑塌浊积扇来源东北部的侯庄辫状河三角洲,岩性为深灰色中砂岩和细砂岩,多夹于深灰色湖相泥岩中,与泥岩呈突变接触,粒度概率曲线具有"低斜一段"式特征,地震剖面上透镜状地震反射与前积地震反射共存。三角洲向前推进快、朵叶向前延伸较远的时期,易形成数量多、面积大的滑塌浊积扇。东北部三角洲前缘水体浅,湖平面的突然下降使得三角洲前缘出露部分因浮力消失而不稳定,可产生局部滑塌。波浪作用可以强烈剥蚀和改造浪基面附近的三角洲前缘沉积,并在波浪的回流作用下进一步形成浊积砂体,因此,湖平面下降有利于无外界触发机制作用下三角洲前缘滑塌浊积扇的形成。

Through the research of lithologic combination,granularity analysis and seismic reflection characteristic in the deep area of Biyang Depression,it was considered that the slumping turbidite fan in the abyss was derived from Houzhuang braided delta,where lithology was dark grey and medium sandstone and fine sandstone,it was mainly of interlayer in the dark grey lake shale,was abruptly contacted with shale,and it had one section low-slope characteristics in granularity probability curve,with lens seismic reflection and progradation on the seismic section.The period when delta advanced fast forward and lobes extended farther away was a better time for forming the large quantity and volume of slumping turbidite fans.The water is shallow in northeastern delta front,in which exposures are instability due to buoyancy caused by the sudden falling down of lake surface,the local slump lake is produced.Wave was intensely eroded and the sediments of delta front around wave base plane were changed,and turbidity sand was further induced in the action of its reflux.Therefore,the falling down of lake surface is favorable for forming the flux-turbidite in delta front without outside trigger mechanism.