青藏高原北缘玉门红柳峡硅化木成因及其揭示的早白垩世构造及环境

Environment and Tectonic Evolution during Early Cretaceous in Yumen Basin:Evidence from Silicified Woods in Northern Margin of Tibetan Plateau

位于青藏高原北缘玉门盆地红柳峡一带的硅化木化石带是高原北缘地区唯一一处集中连片分布的白垩纪硅化木化石森林带,这种古生物的集群死亡和埋藏常常伴随地球演化灾变性构造事件.首次对该区域产出的硅化木特征及其赋存层位进行了报导,并进一步探讨了该区白垩纪原型盆地的早期演化以及硅化木的成因过程.结果表明:青藏高原北缘玉门盆地早白垩世经历了湖盆的发育、扩展和收缩3个阶段.在早白垩世早期,玉门盆地开始发育并逐渐扩展,该时期气候高温潮湿,在盆地滨湖区域生长了巨大的松柏类乔木森林带;在约102~120 Ma的早白垩世期间,随着阿尔金断裂再次复活,玉门盆地发生大规模的火山喷发,导致盆地植被大面积焚烧死亡和埋藏,最终碳化硅化形成现今集中连片分布的硅化木化石带.早白垩世以来,随着阿尔金断裂持续的左行走滑和向北东方向的扩展,玉门盆地被不断抬升并发生构造旋转,使得下沟组硅化木得以重见天日.

The Hongliuxia region of Yumen basin in northern margin of the Tibetan plateau is the only place where the silicified woods are concentrated and consecutively distributed.These cluster extinctions of the ancient extinct life may be related to the catastrophic event usually.In this paper,it presents an account of the characteristics and strata bearing of the silicified woods,further discusses the evolution of the Yumen basin and the formation of the silicified woods.The results show that the Yumen basin has experienced the growth,expansion and the shrink of the ancient lake.During the growth and the expansion stage of the lake,the paleoclimate was hot and moist,and trees were growing around the ancient lakeside.During the Early Cretaceous between 102-120 Ma,with the reactivation of Altyn Tagh fault(ATF),large-scale volcanic activities occurred in Yumen basin.The volcanism led to the large-scale burning and burial of the tall arbor tree vegetation,finally forming the silicified wood fossil belt.Formation and evolution of Yumen basin are mainly controlled and affected by the activity of the ATF since the Early Cretaceous.