鄂尔多斯盆地奥陶系马家沟组标准化层序地层学研究

Standardization of sequence stratigraphy in Ordovician Majiagou formation,Ordos Basin

应用标准化层序地层理论开展鄂尔多斯盆地奥陶系马家沟组层序地层研究。主要采用了露头观察和岩心描述、岩石薄片鉴定、地球化学分析及测井岩性解释方法,确定地层岩石类型、岩相组合特征、层序地层界面特征及其位置,结合绝对地质年龄及天文周期时限作为层序划分主要依据。文中将马家沟组划分为平均时限为3.65 Ma的3个海平面变化层序,根据岩相组合及地层界面将各层序划分为低位、海侵、高位及强制海退体系域,层序界面位于强制海退体系域顶界,形成于最低海平面开始上升时期,以石盐岩到硬石膏岩或硬石膏岩到准同生泥晶白云岩的岩性转换面为特征。研究结果表明,随着海平面升降运动,碳酸盐岩台地上的岩性组合及变化具有明显的规律性,突显了应用标准化层序地层理论建立的层序划分方案的合理性和实用性。

The standardized sequence stratigraphy theory is applied to investigate Ordovician Majiagou formation. According to kinds of data,such as outcrop,core and logs,the lithologic characteristics and litho facies assemblage characteristics combine with absolute geological ages and astronomical period,rejiggering the division plan about standardization of sequence stratigraphy in Ordovician Majiagou formation. The Majiagou formation can be divided into three sea-level change sequence,and according to the method of system tract four-division,the inside of each sequence is classified as Lowstand System Tract（ LST）,Transgressive System Tract（ TST）,Highstand System Tract（ HST） and Regressive System Tract（ RST）. The sequence boundary is located on the top boundary of RST,and formed when sea-level rise from the lowest level. The lithology conversion surface is from halilith to anhydrite,or from anhydrite to penecon temporaneous micritic dolomitein. Research results show that with sea level rise and drop,the rock compositions on the carbonate rock tableland and their change are of regularity. The Standardized Sequence Stratigraphy Theory provides these kinds of formations with the most reasonable and suitable division method,and it also has practical value.