塔里木盆地轮南古隆起形成时间的判定

轮南古隆起位于塔里木盆地北部，是一个大型基底卷入型鼻状背斜。卷入背斜构造变形的地层包括下古生界及其以下地层。它的形式演化控制着轮南复式油气聚集区的形成与分布。过轮南古隆起的地震剖面上显示，这里发育上泥盆统东河砂岩底、志留系底和上奥陶统底3个与古隆起形成密切相关的不整合面。上奥陶统底是一个低角度不整合面至平行不整合面，地层间断很小。志留系与下伏地层之间是一个低角度不整合接触，存在一定规模的地层间断。东河砂岩与下伏地层之间是一个明显的角度不整合接触，是一个较大的地层间断。东河砂岩直接不整合覆盖在下志留统甚至更老地层之上。上奥陶统至下志留统（中-上志留统缺失）为生长地层；上奥陶统之下的地层是前生长地层；东河砂岩及其上覆的石炭系是生长后地层。根据已有构造分析成果，塔里木盆地中志留世—中泥盆世处于造山后区域性伸展构造背景。据此分析，轮南古隆起（背斜）的构造变形起始于中奥陶世末—晚奥陶世初，持续至早志留世。此后进入风化夷平阶段，古隆起依然存在，但是背斜构造变形已经结束。至东河砂岩沉积时，轮南古隆起基本被夷平，并逐渐被埋于地下。

Timing the formation of the Lunnan paleo-uplift in Tarim Basin,NW China

The Lunnan paleo-uplift located in the northern Tarim Basin is a large basement-involvedanticline. The strata involved into the anticline deformation include the Lower Paleozoic and the rocks below it. The paleo-uplift control the formation and distribution of the Lunnan complex oil-gasaccumulation province. The seismic profiles crossing the paleo-uplift indicate that, there are 3 unconformities related to the formation of the paleo-uplift. They are the bottoms of the UpperDevonian Donghe sandstone, the Silurian and the Upper Ordovician. The bottom of the UpperOrdovician is a low angle or parallel unconformity. It is a little stratigraphic hiatus between theUpper and Middle Ordovician. It is a low angle unconformity with an obvious hiatus between theSilurian and the rocks below it. The unconformity between the Upper Devonian Donghe sandstoneand the rocks below it is a large hiatus. The Donghe sandstone unconformably overlies the LowerSilurian and older rocks. The Upper Ordovician-Lower Silurian is growth strata. Those below it arepre-growth strata and those above it are post-growth strata. According to the previous work, theTarim block was under post-collision regional tensional tectonic setting in Middle Silurian-MiddleDevonian. Obviously, it can be deduced that the deformation of the Lunnan paleo-uplift（anticline）begun at end Middle Ordovicaian-beginning Late Ordovician, and lasted to Early Silurian, and thenevolved into the weathering and eroding stage from Middle Silurian to Middle Devonian when thepaleo-uplift remain a topographic high while the anticline deformation ceased. And then the Lunnanpaleo-uplift was buried underground gradually.