鄂尔多斯盆地深层中元古界地震波组及构造—地层层序特征

Characteristics of seismic wave groups and tectono-stratigraphic sequences of the Mesoproterozoic in depth layers,Ordos Basin

本文利用最新的测井及地震资料,制作并分析对比了20口井的合成记录,对鄂尔多斯盆地中元古界的地震波组特征展开研究,识别出7个反射界面。其中,T0、T1和T3界面反射波振幅强、连续性好,有着稳定的波形特征,为中元古界主要的区域性不整合面,可作为标志层进行对比。在此基础上,总结了本区中元古界7套地震地层的波组特征,并结合野外露头资料,将研究区中元古界划分为7套构造层,即底部古元古界或太古界片麻岩之上的陆源碎屑沉积岩层Pt2-1(大古石组)、中基性火山岩层Pt2-2(许山组)、酸性火山岩层Pt2-3(鸡蛋坪组)、安山岩夹火山碎屑岩层Pt2-4(马家河组)、碎屑岩层Pt2-5(汝阳群)、泥岩—粉砂岩层Pt2-6(洛峪群)、碳酸盐岩层Pt2-7(蓟县系)。研究发现,鄂尔多斯盆地古元古代末期到新元古代发生了多期裂谷活动,影响了中元古代地层及不整合面的发育。熊耳群为华北克拉通裂谷发育初期,在结晶基底之上沉积的第一套盖层,底部大古石组接受陆源碎屑沉积,此后至熊耳群晚期之间发生的火山活动形成安山岩。裂谷作用晚期,汝阳群粗碎屑岩角度不整合于其上,而后海侵最大,洛峪群泥岩平行不整合于其上。至中元古代末期,海水循环良好,蓟县系碳酸盐岩形成,平行不整合于下伏长城系地层之上。

Based on the latest logging and seismic data,this paper makes and compares the synthetic records of 20 wells,studies the characteristics of the Middle Proterozoic seismic wave set in the Ordos Basin,and identifies 7 reflection interfaces.Among them,the interface T0,T1 and T3 are characterized by high amplitude,good continuity,and have stable waveform characteristics,thus are the main regional unconformities of the Middle Proterozoic,and thus can be used as marker layers for comparison.Based on that,the seismic wave group characters of each seismic stratum among the seven interfaces were summarized,and combined with field outcrop data,the Mesoproterozoic in the study area is divided into 7 sets of structural layers,namely the terrigenous clastic sedimentary layer Pt2-1(Dagushi Formation)above the bottom Paleoproterozoic or Archean gneiss,intermediate basic volcanic layer Pt2-2(Xushan Formation),acid volcanic rock layer Pt2-3(Jidanping Formation),andesite mixed with pyroclastic rocks layer Pt2-4(Majiahe Formation),clastic rock layer Pt2-5(Ruyang Group),mudstone-siltstone layer Pt2-6(Luoyu Group)and carbonate layer Pt2-7(Jixianian System).It is found that there were several stages of rifting from the Late Paleoproterozoic to Neoproterozoic in Ordos Basin,which influenced the development of Mesoproterozoic strata and unconformity.Xionger Group is the first set of cap layer deposited on the crystalline basement in the early stage of the development of the North China Craton rift.The basal Dagushi Formation receives terrigenous clastic deposits,the volcanic activity between then and the late Xionger Group formed andesite.In the late rifting period,the coarse clastic rocks of the Ruyang Group were angularly unconformable above the Xionger Group.Later,the transgression effect was the greatest,and the mudstones of the Luoyu Group were parallel unintegrated on Ruyang Group.By the end of the Mesoproterozoic period,the sea water circulation was good,and the Jixianian System carbonate rocks were formed,which were parallel unintegrated in the overlying Changcheng System strata.