One of most hotly debated topics concerning the Late Mesozoic evolution of Tethyan and the Tibetan Plateau is the timing of the closure of the Meso-Tethys ocean, which is represented by the Bangong–Nujiang suture zone. The Upper Jurassic–Lower Cretaceous Shamuluo Formation, which unconformably overlies the older Mugagangri Group accretionary complex, provides important information on the closure of the Meso-Tethys Ocean. This paper precisely confines the depositional age of the Shamuluo Formation in the western segment of the Bangong–Nujiang suture zone, extending it from the Late Jurassic to the Albian. Combined with the results of previous studies, we suggest that the Shamuluo Formation in the Awengco–Baerqiong region mainly contains a bathyal Berriasian–Hauterivian subunit and a shallow-marine Albian subunit. Provenance analysis indicates that the Berriasian–Hauterivian subunit was mainly derived from the Jurassic southern Qiangtang magmatic arc, while the Albian subunit was derived from the coeval volcanic rocks and the Upper Carboniferous–Upper Permian strata in the southern Qiangtang terrane. Thus, the two subunits of the Shamuluo Formation have significant distinct sedimentary facies and provenances, indicating that they were deposited in different tectonic settings.Based on the regional geological data, we suggest that the bathyal Berriasian–Hauterivian subunit and the shallow-marine Albian subunit of the Shamuluo Formation should be interpreted as a record of the oceanic arc-continent collision and the Lhasa–Qiangtang soft-collision, respectively. Thus, the closure time of the Meso-Tethys Ocean is at least limited to the Albian. 相似文献
毛乌素沙地位于东亚季风边缘区,对于气候变化响应敏感。基于沙地的侵蚀-堆积关系,在侵蚀作用为主的沙地西北部和中部很难找到沉积相对连续且分辨率较高的地层剖面,因此已有的末次冰期古气候环境研究多集中于堆积作用为主的沙地东南缘的萨拉乌苏河河谷地区。本文选取位于沙地腹地,厚度为3.5 m的风成砂-河湖相沉积序列——神水台(SSTG)剖面为研究对象,基于AMS14C和OSL年代数据,推测得出剖面中湖相层的上界和下界分别为约24.2 ka B.P.和42.7 ka B.P.,依据沉积地层和环境代用指标分析结果,针对末次冰期毛乌素沙地湖泊消涨的一般过程进行了探讨。结果表明,自约5万年以来,由神水台(SSTG)剖面指示了两次明显的湖泊主要发育期,时间分别约为42.7~34.3 ka B.P.和31.1~24.2 ka B.P.,期间粘土含量、有机质、红度均表现为低值,为含淡水螺壳化石的典型湖泊相沉积,且与毛乌素沙地已有湖泊发育的年代结果基本一致。在两期湖相层之间的砂层,平均粒径、砂含量表现为峰值,指示了一次明显的湖泊消退的过程,其时间约为34.3~31.1 ka B.P.;在湖相层上下可能均为风力作用为主导的风沙沉积。通过区域对比并初步探讨其可能的驱动机制,结果表明SSTG剖面记录的湖泊消涨过程主要受控于东亚季风强度的变化。