松辽盆地营城组火山地层单元和地震地层特征

Characteristics of volcanic stratigraphy units and seismic stratigraphy of Yingcheng Formation in Songliao Basin,NE China

本文依据对松辽盆地营城组火山岩地层界面特征、构成单元和地震相单元的分析,探讨了火山岩地震、地质特征,得到以下认识:①松辽盆地营城组火山岩地层常见角度不整合和火山不整合界面(由喷发物的堆积方式的差异形成的"角度不整合"),少见平行不整合和整合界面;②根据火山岩的形成过程和岩石界面特征,可将火山岩地层单元由小到大依次分为冷却单元、冷却单元组合、火山机构、火山机构群4级,在现今地震资料分辨率情况下可达到对火山机构群、火山机构的有效刻画;③在营城组一段、三段火山岩地层中可识别出席状、席状披盖、盾状、丘状、透镜状、楔状、扇状、碟状/盘状和筒状等9种基本地震相单元,每种地震相单元可与某种火山机构对应,在同一地震相单元内岩层或岩层组产状从喷发中心向远端倾向相同、倾角变小,根据其叠置关系可建立火山地层(冷却单元组合)的相对地质年代格架。上述成果为火山岩地层的地震刻画提供了理论依据。

Seismic-geology characteristics of volcano stratigraphy of Yingcheng Formation are discussed in this paper by integrated analyses of volcanic boundary,volcanic units and seismic facies units.There are three viewpoints about seismic-geology characteristics of volcanic rocks.Firstly,almost boundaries of volcano stratigraphy of Songliao Basin are the angle or volcanic disconformity;the others are parallel disconformity or conformity.Secondly,volcano stratigraphy units can be divided into cooling units,cooling unit group,volcanic edifices and volcanic edifices group according to the building process and the boundary characteristic.In the resolution of current seismic data can exact reveal the volcanic edifices or its group.Thirdly,seismic facies units of 1st and 3rd member of Yingcheng Formation are divided into 9 types.They are sheet-shaped,sheet-shaped drape,shield-shaped,mount-shaped,lens-shaped,wedge-shaped,fan-shaped,saucer/plate-shaped and pipe-shaped.The seismic facies units can be explained to the volcanic edifices.The dip angle of volcanic rock beds decreases from central to distal parts along a given edifice's limb.The relative geological framework of volcano stratigraphy(cooling unit group) can be built according to the overlap sequence of rock beds in seismic facies units.This is a new way to characterize the volcano stratigraphy.