塔里木盆地柯坪地区奥陶系鹰山组台内滩沉积特征

通过对柯坪地区蓬莱坝剖面奥陶系鹰山组的野外实测可以将其划分为下、中、上三段，每段都具有不同的相序结构和沉积特征，下段主要以含陆源泥质的泥晶粗砂屑灰岩为主，中段为亮晶粉-细砂屑灰岩和层纹石灰岩互层出现，上段主要为中-厚层状似球粒泥晶灰岩，台内颗粒滩主要发育在中、下两段；柯坪水泥厂剖面也可以划分为三段，但界限没有蓬莱坝剖面明显，主体表现为中层状的亮晶砂屑灰岩和泥晶砂屑灰岩交互出现。通过对蓬莱坝剖面和柯坪水泥厂剖面的岩石进行野外露头、偏光显微镜、扫描电镜等不同尺度的观测及沉积微相分析，理清了柯坪地区鹰山组的岩石类型和相序结构，建立了柯坪地区颗粒滩沉积模式:由于水体深度和能量的差异，柯坪地区发育了四种相带类型--高能颗粒滩相带、滩间洼地沉积相带、低能颗粒滩相带、开阔浅海沉积相带。中-低能颗粒滩相带主要发育泥晶中-粗砂屑颗粒滩，高能颗粒滩相带主要发育亮晶细-中砂屑颗粒滩，并且两种颗粒滩都可以划分出3种亚相--滩主体、滩翼和滩内洼地；在微生物主导的碳酸盐建造向后生动物主导的碳酸盐岩建造转换的地质背景下，柯坪地区在奥陶系鹰山组沉积时期总体处于大面积发育微生物似球粒的浅水环境，沉积物的形成与改造受微生物活动的影响，微生物作用一方面为颗粒滩的发育提供了良好的物质基础，另一方面也控制了该时期颗粒滩的沉积特征。

Sedimentary Characteristics of Lower-Middle Ordovician Yingshan Formation Carbonate intra-platform Shoals in Keping area,Tarim Basin

Three intervals were identified in the Penglaiba Section of Keping area, and every interval has different facies associations and sedimentary characteristics:the lower interval is coarse grains intraclast wackestone or packstone limestones with a little of terrigenous mud; the middle interval is the association of sparry silt and fine grains intraclast grainstone limestones and laminites limestones; the upper interval is medium thickness peloids micrite limestones. And the intra-platform shoals are found in the lower and middle interval. The Keping cement plant cross-section also can be divided into three intervals, but the boundary is not clear, the sparry intraclast limestones and micrite intraclast limestones appearing in rotation overall. According to outcrop observation, thin section identification and sedimentary microfacies analysis to the Penglaiba cross-section and Keping Cement Plant cross-section, we clarified the types of rock and facies association and built up the sediment models of Yingshan Formation:According to the water depth and energy, the Keping area developed four types facies belts-high energy shoals belt, middle-low energy shoals belt, inter-shoals despressions sediment belt, and open shallow marine sediment belt. The high energy shoals belt developed sparry fine-middle grains intraclast shoals and the middle-lower energy shoals belts developed micrite middle-coarse grains intraclast shoal, and every shoal can be divided into three subfacies-shoal body, shoal wing and inner-shoal depression; The Keping area was located in shallow marine environment with extensive microbial peloids and it was a special stage of Ordovician that the carbonate rock transformed from microbial constructions to metazoan constructions in Tarim Basin, so the formation and reform of sediment was affected by microbial activity. On the one hand, microbial action of the Ordovician Yingshan Formation based the material condition for the shoals. On the other hand, it controlled the carbonate sedimentary characteristics of Yingshan Formation.