山西左云地区下白垩统左云组沉积相及其古气候意义
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本文为山西省国土资源厅项目(山西晚古生代锯齿龙类脊椎动物化石及地层系统调查)资助的成果。


Sedimentary Facies of Lower Cretaceous Zuoyun Formation and Paleoclimate of Early Cretaceous
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    摘要:

    最近,山西左云地区下白垩统左云组中发现了保存完好的剑龙化石,笔者对左云组的沉积相、剑龙的埋藏环境及当时的古气候和进行了分析。系统的沉积学研究表明,左云组为一套典型的洪积扇沉积,是由泥石流和暂时性水流作用交替发育而形成的产物。根据岩性特征和剖面结构,可将左云组划分为扇根、扇中、扇缘及扇间四个亚相,剖面上可进一步识别出泥石流沉积、主槽—河道、漫洪—漫流带、辫流线四个微相。结合孢粉及古生物数据分析,早白垩世晚期,左云地区总体为亚热带沙漠边缘干旱环境,但仍体现出干旱和潮湿的无规律变化,突发的季节性暴雨或特大暴雨(千年一次)的出现,形成特大洪峰,短时间内形成巨厚的洪积扇砾岩—泥岩。剑龙埋藏环境为扇根—扇中部位漫洪—漫流带,是特大洪水期溢出主槽而于山前形成的“片汜沉积”,剑龙陷于厚层泥质中而被埋藏保存下来。

    Abstract:

    Objectives: Recently,wellpreserved Stegosaur fossils were discovered in the Lower Cretaceous Zuoyun Formation, which is a typical continental deposits, in Zuoyun area, Shanxi Province. Sedimentary facies of the Zuoyun Formation and burial environment of Stegosaur have been analysised based on geological section and sedimentology research. Furthermore, paleoclimate of the Zuoyun stage has been discussed based on aforementioned analysies. Methods: Firstly, we classify the Zuoyun Formation as a set of proluvial fan deposits based on lateral distribution and vertical thickness changes of interbedding of conglomerate and mudstone in the Zuoyun Formation. Furthermore, hydronamic mechanism of proluvial fan has been analysised and subfacies and microfacies have been recognized based on variation of lithofacies,interior fabric,sedimentary structures from the bottom to top. Results: Systematic sedimentology research have disclosed that the Zuoyun Formation belongs to typical proluvial fan deposits,produced by alternative debris flow and temporary stream flow processes. Based on lithologic characteristics and profile section structures, the Zuoyun Formation may be divide into three subfacies, namely the fan top, middle fan and fan margin, further four microfacies can be recognized in the profile, namely debris flow deposits,main ravine—channel, flood zone—flood flow zone,braided stream. Conclusions: Analysis combined with palynological and paleotological data indicates that Zuoyun area was generally dominated during Early Cretaceous by arid environment of subtropical desert periphery, accompanied by irregular alternation of arid and humid, during which catastrophic flood peak formed by monsoonal to millennial sudden rainstorm or extraordinary rainstorm may result in thick proluvial fan conglomerate—mudstone deposits.

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董黎阳,伊剑,刘颖超,续世朝,王锁柱,张财.2018.山西左云地区下白垩统左云组沉积相及其古气候意义[J].地质论评,64(2):392-404,[DOI].
DONG Liyang, YI Jian, LIU Yingchao, XU Shichao, WANG Suozhu, ZHANG Cai.2018. Sedimentary Facies of Lower Cretaceous Zuoyun Formation and Paleoclimate of Early Cretaceous[J]. Geological Review,64(2):392-404.

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  • 收稿日期:2017-07-05
  • 最后修改日期:2017-12-27
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  • 在线发布日期: 2018-03-24
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