鄂尔多斯盆地东北部马五1+2亚段岩石类型及沉积环境

受多期岩溶叠合改造影响，鄂尔多斯盆地东北部奥陶系马五₁₊₂亚段的原岩组构遭受破坏，制约了对原始沉积环境及沉积相的恢复研究。基于岩芯、薄片及阴极发光研究，通过原岩组构恢复，在区内识别出5种主要的原始碳酸盐岩类型及7种成岩作用产物岩石类型，并总结出5种岩石类型组合，分别形成于局限-蒸发台地内的颗粒滩、滩间海、丘滩复合体、台坪和局限瀉湖沉积环境。纵向上可构成局限瀉湖-颗粒滩-台坪、局限瀉湖-丘滩复合体-台坪等4种典型的向上变浅沉积序列。结果表明，颗粒岩类与含膏模孔泥（粉）晶云岩类是盆地东北部马五₁₊₂亚段最主要的原始岩类，并发育有一定规模的藻黏结岩和泥晶云岩，其中含膏模孔泥（粉）晶云岩与丘、滩向上变浅序列密切相关。这些认识将为深化区内古环境和储集岩类研究提供依据。

Rock Types and Sedimentary Environment of the Ma51+2 Carbonates in Northeastern Ordos Basin

Affected by multi-period karst cumulated influence, the original rock fabric of Ma5₁₊₂ member of Ordovician in the northeastern Ordos basin have suffered a great destruction which restricted the reconstructing study of original palaeoenvironment and sedimentary facies. Based on core, thin section, cathode luminescence and the recovery of the protolith, five original rock types and seven rock products of diagenesis are recognized, and it can be divided into five rock type combinations, which represents about five sedimentary environment in restricted and evaporate platform of study area in the following:grain beach, beach interaction sea, mound-shoal complex, platform inner flat and restricted lagoon. Those rock type combinations constitutes four typical sedimentary sequences in vertical which reflects a drop in sea level, including restricted lagoon- platform inner shoals- platform inner flat and restricted lagoon- mound-shoal complex- platform inner flat. The results show that the grainstones and gypsum mould pore contained mud(bread flour)-crystal dolomitite form the two major kinds of original rock types in Ma5₁₊₂ member of Ordovician in northestern Ordos basin, a certain scale of algal binding rock and mud(bread flour)-crystal dolomitite are also found. Besides, the gypsum mould pore contained mud(bread flour)-crystal dolomitite shows a close relationship with the upward shoaling succession of mounds and shoals. These new recognition can provide the basis for in-depth study of palaeoenvironment and reservoir rocks in the study area.