准噶尔盆地陆东地区石炭系地震波组及构造-地层层序特征

Characteristics of seismic wave groups and tectono-stratigraphic sequences of the Carboniferous,eastern Luliang uplift,Junggar Basin

利用最新钻井与地震资料,对准噶尔盆地陆东地区石炭系的地震波组特征展开研究,在此基础上划分了研究区构造-地层层序。通过分析对比30口井的合成地震记录,识别出4个主要反射界面:T_0,T_1,T_2和T_3。T_0和T_2界面反射波振幅强、连续性好、波形稳定,为本区主要的区域性不整合,也是关键的可对比标志层。在此基础上,总结了4个反射界面间各地震地层的波组特征,其中T_1与T_2之间的反射波组整体振幅弱、中-低频和中-差连续,反射外形呈楔状,可作为陆东地区对比的标志层。在不整合面追踪的基础上,结合露头、古生物资料和年代学资料等,将研究区石炭系划分为4套构造层,从下至上分别为:下沉积岩段C_1-s(滴水泉组)、下火山岩段C_1-v(松客尔苏组下亚组)、上沉积岩段C_2-s(松客尔苏组上亚组)和上火山岩段C_2-v(巴山组)。研究认为,石炭系各构造层的分布受基底、构造背景、发育位置及后期改造作用的控制,在弧内断陷和弧前盆地等部位发育的厚度相对较大,在岛弧凸起部位厚度较小;早、晚石炭世末发育的两期构造挤压运动,导致C_1-v与C_2-s之间的地层及C_2-v构造层顶部遭受剥蚀,并使石炭纪断陷发生反转。

We explored the characters of seismic wave groups of the Carboniferous in the eastern Luliang uplift of Junggar Basin under the guidance of the latest drilling and seismic data.Accordingly,the tectono-stratigraphic sequences were identified in the study area.Four main reflection interfaces,namely T 0,T 1,T 2 and T 3,were identified based on analysis and correlation of synthetic seismograms of 30 wells.Among them,the interface T 0 and T 2 are characterized by high amplitude,good continuity,and stable waveform of reflective waves,thus are the main regional unconformities and the critical key beds of comparison in the area.Based on that,the seismic wave group characters of each seismic stratum among the four interfaces were summarized.We thus knew that the seismic wave groups between T 1 and T 2 have low amplitude,medium-low frequency and moderate-poor continuity,and wedge-shaped reflection,thus can be used as the key beds of comparison in the eastern Luliang uplift.Then we traced the unconformities,analyzed the outcrop,paleontological and chronological data,and subsequently subdivided the Carboniferous herein into four tectonic layers.From the bottom to the top,they are the lower sedimentary tectonic layer C 1-s(Dishuiquan Formation),lower volcanic tectonic layer C 1-v(Songkaersu lower group),upper sedimentary tectonic layer C 2-s(Songkaersu upper group)and upper volcanic tectonic layer C 2-v(Bashan Formation).The results can be summarized as follows:(1)the distribution of tectonic layers in the Carboniferous is controlled by the basement,tectonic setting,location of development and later modification.Their thickness is relatively large in the intra-arc fault depression and fore-arc basin,while is relatively small on the island arc convex;(2)two tectonic compression activities developed at the end of the Early and Late Carboniferous respectively lead to the denudation of the strata between C 1-v and C 2-s and that on top of the C 2-v,and the inversion of the fault depression in the Carboniferous.