摘要：

综合野外露头及钻井岩心、薄片观察,总结了鄂尔多斯盆地中东部奥陶系马五₄亚段沉积微相类型及纵向微相序结构类型。并选取膏盐岩累计厚度及膏盐岩累计厚度/地层厚度等单因素,以单因素分析多因素综合作图法理论为指导,对马五₄³、马五₄²、马五₄^1b、马五₄^1a等4个小层进行深入研究。分析结果表明,马五₄亚段沉积时期处于一个干旱炎热、海平面相对较低的沉积环境,其内部存在隆洼相间的古沉积格局,从马五₄³沉积时期至马五₄¹沉积时期,相对海平面逐渐上升,海水含盐度逐渐降低,这些是控制各小层沉积微相发育和空间分布的重要因素。

关键词: 沉积微相, 马家沟组, 奥陶系, 鄂尔多斯盆地

Abstract:

Based on the analysis of outcrops,drilling core samples and thin sections,this paper summarized the sedimentary microfacies and its vertical sequence types of the 4th sub-member of Member 5 of Majiagou Formation in Ordovician of central and eastern Ordos Basin. The palaeogeography of four periods which are M5₄³,M5₄²,M5₄^1b and M5₄^1a of Majiagou Formation is studied,mainly based on the parameters including the cumulative thickness of gypsum-salt rock and its ratio to the whole formation. The result shows that the study area is an arid environment with a low sea level during the 4th sub-member of Member 5 of Majiagou depositional period. The sedimentary pattern was uplifts alternate with depressions. From the early to later,the relative sea-level gradually rose and the salinity reduced,which controlled the development and spatial distribution of sedimentary microfacies of these sub-members.

Key words: sedimentary microfacies, Majiagou Formation, Ordovician, Ordos Basin

中图分类号: 

• P531