标准微相类型在碳酸盐岩微相及沉积环境研究中的应用——以塔西南玉北地区奥陶系为例

The Application of Standard Microfacies Types to the Study of Carbonate Microfacies and Depositional Environments——A case study from the Ordovician in the Yubei area,southwestern Tarim Basin

标准微相类型是一种虚拟分类,是对具有相同标志的微相的概括。按照从盆地到地表暴露区的顺序,Flügel将镶边台地不同相带的碳酸盐岩分为26种标准微相类型,即SMF 1~SMF 26,并建立了标准微相类型图版及其分布相带的台地模式。以此为依据,对塔西南玉北地区奥陶系碳酸盐岩的标准微相类型进行了研究。共识别出九种标准微相类型,不同层段均以特定的微相类型组合为特征:蓬莱坝组—鹰山组下段(O1p-O1-2y下)为SMF 15-C、SMF 16-非纹层和SMF 17;鹰山组上段—一间房组(O1-2y上-O2yj)为SMF 16-非纹层、SMF 17和SMF 23;恰尔巴克组(O3q)为SMF 6和SMF12-海百合,以及SMF 1-掘穴;良里塔格组(O3l)为SMF 9和SMF11,以及SMF 15-C、SMF 16-非纹层和SMF 17。同时,分析了不同微相类型的测井响应特征,从而通过测井连井剖面对比来揭示不同微相类型组合的空间分布。根据标准微相类型组合及其空间分布,对不同层段的原始沉积环境进行了恢复。研究表明,玉北地区奥陶系先后经历了开阔台地(O1p-O1-2y下)、局限台地(O1-2y上-O2yj)、斜坡—陆棚(O3q)及台缘—开阔台地(O3l)四种沉积环境的演化。

The Standard Microfacies（SMF） Types are virtual categories that summarize microfacies with identical criteria. SMF 1 to SMF 26 are divided following the order of the facies zones in the rimmed carbonate platform going from the basin to the subaerial exposure areas,and the plates of the SMF Types,as well as the model of the SMF Types distributed in facies zones are developed by Flügel. Based on that,the SMF Types of the Ordovician carbonate in the Yubei area were studied. Nine of the SMF Types have been recognized in total,which always occur in certain assemblages. The assemblages are SMF 15-C,SMF 16-NON-LAMINATEDand SMF 17 in the Penglaiba-lower Yingshan Formations（O1 p-O1-2 ylower）,SMF 16-NON-LAMINATED,SMF 17 and SMF 23 in the upper Yingshan-Yijianfang Formations（O1-2 yupper-O2 yj）,SMF 6 and SMF 12-CRIN,as well as SMF 1-BURROWEDin the Qiaerbake Formation（O3 q）,SMF 11 and SMF 9,as well as SMF 15-C,SMF 16-NON-LAMINATEDand SMF 17 in the Lianglitage Formation（O3 l）. Additionally,the characteristics of the log responses were analyzed for the assemblages of SMF Types,whose spatial distributions were outlined by comparison of the gamma log curves along the well-tie sections. The originally depositional environments were recovered for the Ordovician formations according to assemblages of the SMF Types and their spatial distribution. The study results indicated that the Ordovician had experienced the evolution of four depositional environments in the Yubei area,that is,open marine（O1 p-O1-2 ylower）,restricted marine（O1-2 yupper-O2 yj）,slope-deep shelf（O3 q） and platform margin-open marine（O3 l） in sequence.