再论鄂尔多斯盆地寒武纪岩相古地理及沉积构造演化

鄂尔多斯盆地深部是目前我国石油领域研究的热点。在构造控制沉积的思想指导下，运用层序地层学理论，以野外露头观察、岩心观察、测井和地震剖面研究为基础，以单因素分析-综合编图为方法，以盆地寒武纪构造-沉积演化为主线，以储层-成藏为目标，首次编制了三级层序地层格架下的鄂尔多斯盆地寒武纪岩相古地理图。本区寒武纪具有一个由清水与浑水交替出现的碳酸盐岩缓坡向台地、局限台地演化的动态过程，而且古气候也有一个由干旱向相对潮湿演变的趋势。早期近南北分异，晚期近东西向分异。早期南部存在奥拉谷。中晚期除北部和西缘部分地区外，鄂尔多斯古陆基本被海水覆盖，完成了从陆到海的转变，形成了以陆表海浅水台地为主要特点的古地理格局。“古鄂尔多斯海”的形成是环境变化的转折点。晚期西部发生隆起，这是鄂尔多斯盆地“中央古隆起”的雏形。该隆起走向近南北，与奥陶纪中央古隆起范围基本相同。通过构造沉积-演化分析，首次明确了“中央古陆”最早的形成时间为寒武纪芙蓉世到早奥陶世，也明确了鄂尔多斯盆地寒武纪早期潮坪相为优势相带、而张夏组鲕粒滩具环陆分布特点、三山子多孔白云岩主要发生于寒武系上部，具有全区分布特点。怀远运动是寒武系顶部遭受风化剥蚀而发生岩溶作用的主因。祁连洋的俯冲作用是鄂尔多斯古陆发生变异的主要动力。怀远运动形成的寒武系顶部（包括部分下奥陶统）不整合面可能是最重要的深部勘探方向。

Further Study on Lithofacies Palaeogeography and Sedimentary-Tectonic Evolution of Cambrian in Ordos Basin,North China

It is now a hot spot to prospect oil and gas in deep of Ordos basin, North China. Seven new lithofacies palaeogeography maps on Ordos have been sketched out, according to the guideline of which tectonism controls sedimentation, applying the sequence stratigraphy theory, on the ground of field outcrops observations, core observations, logging data and seismic profiles, applying the method of single factor analysis and comprehensive mapping, and taking tectonic-sediment evolution as storyline, and reservoir-accumulation as the goal. The research has shown that there was a dynamic evolution process in Cambrian in Ordos, in which carbonate ramps formed platforms and restricted platforms. The carbonate ramps were characterized by exchanging of clear water and muddy water. The research also shows that drought in early became relative humidity in late. There was a tectonic differentiation in south-north earlier and west-east later. Southern Ordos margin appeared aulacogen. Ancient Ordos Land (AOL) was, fundamentally, covered by seawater except the parts of north and west margin in the Middle-Late Cambrian. A conversion in which land was changed to sea had been completed. The characteristic of palaeogeography was mainly a shallow water carbonate platform on the continental sea. The forming of “Ancient Ordos Sea” (AOS) was a turning point. The west arises in Late Cambrian，which is a rudiment of “Central Paleouplift”(CP) which mainly had formed in Ordovician. The Late Cambrian uplift ran in north to south and is basically the same range as “Ordovician Central Paleouplift”. Therefore, it has been proved that the earliest age of forming “Central Ordos Paleouplift” is from Cambrian Furongian to the Early Ordovician. It has also been proved that tidal flat is dominating facies in the Early Cambrian, oliticbeachs are distributed around the land in Zhangxia Formation in the Middle Cambrian and porous dolostones which distributed in whole areas mainly occur in the top of Cambrian. Huaiyuan movement is a key reason why weathering and karstification took place on the top of Cambrian in Ordos. The subduction of ancient Qilian Ocean led to the chief geodynamic differentiation of Ordos Ancient Land. The unconformity surface of the top of Cambrian and part Lower Ordovician should be the most important deep exploration target.