美国Bryce峡谷Claron组粒度端元指示的风尘沉积及意义  

Eolian Deposition and Its Significance in the Claron Formation Indicated by Grain-size End Members in the Bryce Canyon,Utah,USA

作　　者：周声芳 刘秀铭[1,2,3] 毛学刚 邢行[1,2] 连悦辰 ZHOU ShengFang;LIU XiuMing;MAO XueGang;XING Hang;LIAN YueChen(State Key Laboratory of Subtropical Mountain Ecology(Funded by Ministry of Science and Technology and Fujian Province),Fujian Normal University,Fuzhou 350007,China;School of Geographical Sciences,Fujian Normal University,Fuzhou 350007,China;Department of Earth and Environmental Sciences,Macquarie University,Sydney NSW 2109,Australia)

机构地区：[1]福建师范大学湿润亚热带山地生态国家重点实验室培育基地,福州350007 [2]福建师范大学地理科学学院,福州350007 [3]Department of Earth and Environmental Sciences,Macquarie University,Sydney NSW 2109,Australia

出　　处：《沉积学报》2023年第4期1011-1024,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41772180)。

摘　　要：美国犹他州西南部广泛出露的古新世—始新世Claron组是研究该时期气候环境变化的优质材料。已有研究认为Claron组为河湖相沉积地层,但是野外考察结果显示一些层位存在显著的风尘沉积特征,因此有必要对该地层的沉积环境进行重新探讨。以Bryce峡谷国家公园的Claron组为研究对象,野外沉积特征和石英颗粒表面结构特征均指示地层红色层以风尘沉积为主。采用非参数粒度端元分析模型对其进行粒度组分分解,得到6个具有不同沉积意义的端元,分别代表成土组分、积水洼地/临时性湖泊静水沉降组分、冲—洪积组分以及风尘沉积组分。其中端元3、4、6(第一众数粒径分别为5.33μm、11.93μm、42.34μm)均被识别为风尘沉积组分,在地层中的平均含量近50%,表明地层一半以上物质来自风尘沉积,且风尘沉积组分在各时期均占有较大比例,是该地层稳定的物质来源。各端元在地层中的比例变化表明地层由风尘沉积、冲—洪积和积水洼地/临时性湖泊交替沉积形成。在冲—洪积和积水洼地/临时性湖泊沉积为主的时期,气候环境湿润;而风尘沉积和成土占据主导的时期,气候相对干旱。The Cenozoic Claron Formation spanning the Paleocene to Eocene,which is widely exposed in the western United States,is suitable for studying climatic and environmental change in this period.The Claron Formation has generally been interpreted as a fluvial-lacustrine deposit,but eolian deposit features are evident from field observations.Therefore,identifying eolian components in the strata and discussing their significance is of vital importance for interpreting the sedimentary environment of the Claron Formation.The area of the Claron Formation covered by this study was the Bryce Canyon National Park.The eolian deposits in the strata were firstly identified by field observation of the sedimentary characteristics and the surface textures of quartz grains.Then the eolian components of the rock were determined by non-parametric grain-size end-member analysis to unmix the grain-size components.It was found that most of layers are red in color,and the deep-to-light variation of the red color of the strata and the off-white color vary overall with the bedding/horizon.The sediments were found to be homogeneous,mainly composed of silt and clay and rich in carbonate,with well developed vertical joints.Aggradational deposit properties were clearly observed in the red layers,evidence that the sedimentation and weathering processes were simultaneous.These field sedimentary characteristics indicate that the red layers are mainly eolian deposits.The quartz grains in the red samples were found to have surfaces characterized by large and small mechanical saucer-shaped pits,deep troughs,round pits,upturned plates and precipitation of SiO2,all of which are indicative of an eolian environment.This provides further evidence of eolian deposition in the red layers.Six end members with different sedimentary significance were obtained from the non-parametric grain-size end-member analysis model:soil-forming components;components of hydrostatic sedimentation formed in soak/ephemeral lake;components transported by high altitude air stream

关 键 词：粒度端元 风尘沉积 Claron组 粒度分布 

分 类 号：P512.2[天文地球—地质学]