柴达木盆地东部上泥盆统—下石炭统沉积分异特征及其主控因素讨论  

Sedimentary differentiation characteristics of and the main factors controlling the Upper Devonian Lower Carboniferous sediments in the eastern Qaidam Basin

作　　者：彭博[1] 刘成林[2] 祁柯宁 刘大鹏 王嘉琦 李宗星[1] 马寅生[1] 胡俊杰[1] PENG Bo;LIU Chenglin;QI Kening;LIU Dapeng;WANG Jiaqi;LI Zongxing;MA Yinsheng;HU Junjie(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;School of Ocean Sciences,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中国石油大学(北京)地球科学学院,北京102249 [3]中国地质大学(北京)海洋学院,北京100083

出　　处：《地学前缘》2021年第1期104-114,共11页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(DD20190107,DD20190094)。

摘　　要：泥盆系/石炭系是广泛的不整合界面。在我国柴达木盆地东部,上泥盆统至下石炭统呈现明显的沉积分异,这种差异代表着晚泥盆世以来沉积环境巨大变迁。为探究二者之间的差异和内在联系,本次利用岩石学研究手段,通过柴达木盆地东部上泥盆统与下石炭统的岩石组合、分布及岩相对比,刻画晚泥盆世至早石炭世沉积物质空间分布特征,并结合地质背景讨论了沉积物质分布差异内在因素。结果认为,柴达木盆地东部上泥盆统与下石炭统物质特征、古地貌特征既有区别又有内在联系。尽管二者存在沉积间断,但早石炭世早期沉积物质仍呈现对前者地貌特征的继承性。受加里东末期南北向应力作用影响,晚泥盆世区内地貌开始呈现南北分异的格局,发育冲积扇火山为特征的沉积体系。早石炭世早期地貌格局呈现更为清晰的继承性,其沉积岩石基本组分与晚泥盆世相似。但造山作用减弱使夷平作用主导,加之气候进一步湿润使其又有所不同,岩石组合自底部氧化色向上演化成灰色、灰黑色,岩相从辫状河转变为混积潮坪,并伴有小规模海侵成因泥灰岩,含生物泥灰岩夹层。早石炭世晚期更多表现为差异性大于继承性,至早石炭世晚期,夷平作用结束。受全球性大规模海侵以及全球冰雪消融、气候回暖、古亚洲洋古特提斯洋扩张和海水向北漫至该区影响导致全面海泛。加之此时柴达木地处低纬度地区温暖气温有助于海洋生物繁盛,最终促使柴东地区大规模陆表海碳酸盐岩沉积。The Devonian Carboniferous boundary is an extensive unconformity.In the eastern Qaidam Basin,typical sedimentary diversity developed in the Upper Devonian Lower Carboniferous sediments,representing a large-scale sedimentary environmental change during the Late Devonian Carboniferous period.To investigate the differences and inherent relations between the Upper Devonian and Lower Carboniferous,we compared the rock assemblage,distribution and lithofacies between the two,using petrologic methods,and described the spatial distribution characteristics of the Late Devonian Early Carboniferous sediments.By combining the above results with geological background,we discussed the inherent factors for the sedimentary distribution difference.The results demonstrate not only obvious sedimentary differences but also inherent correlation between the Upper Devonian and Lower Carboniferous strata in the eastern Qaidam Basin according to material characteristics and paleogeomorphologic features.Although there is a depositional discontinuity between the two periods,the early-stage Early Carboniferous sediments display inherited paleogeomorphologic features of the Upper Devonian.Under the Late Caledonian NS-trending stress,a NS-differentiated geomorphologic framework started to emerge in the Late Devonian,and the area developed sedimentary systems featuring alluvial fan-volcano.In the early-stage Early Carboniferous paleogeomorphologic framework showing more obvious inheritance,the basic sedimentary composition was similar to that of the Late Devonian period.However,deplanation became dominant as orogeny weakened,and humid climate further altered sedimentary morphology.The rock assemblage evolved from the bottom oxide color upward to gray and grayish-black,and the lithofacies changed from discerning river to mixed tidal flat,accompanied by small-scale interbedding of transgressive and biological marls.The late-stage Early Carboniferous exhibited greater variety than inheritance until deplanation ended.The warming of climate caused g

关 键 词：柴达木盆地 上泥盆统—下石炭统 沉积分异 主控因素 继承式沉积 

分 类 号：P534.44[天文地球—古生物学与地层学] P534.45[天文地球—地质学]