美国Bryce峡谷古新统-始新统红色层古土壤微形态特征及其指示意义  

RED PALAEOSOL MICROMORPHOLOGICAL CHARACTERISTICS AND THEIR INDICATIVE SIGNIFICANCE OF PALEOCENE-EOCENE STRATUM IN BRYCE CANYON,UNITED STATES

作　　者：周声芳 刘秀铭[1,3,4] 毛学刚 何玲珊[1,2] 连悦辰 邢行 ZHOU Shengfang;LIU Xiuming;MAO Xuegang;HE Lingshan;LIAN Yuechen;XING Hang(Key Laboratory for Humid Subtropical Eco-geographical Processes of the Ministry of Education,Fujian Normal University,Fuzhou 350007,Fujian;School of Geographical Sciences,Fujian Normal University,Fuzhou 350007,Fujian;Institute of Geography,Fujian Normal University,Fuzhou 350007,Fujian;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生态地理过程教育部重点实验室,福建福州350007 [2]福建师范大学地理科学学院,福建福州350007 [3]福建师范大学地理研究所,福建福州350007 [4]Department of Earth and Environmental Sciences,Macquarie University,Sydney NSW 2109,Australia

出　　处：《第四纪研究》2022年第2期529-540,共12页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41772180);福建省自然科学基金项目(批准号:2020J01141)共同资助。

摘　　要：地层中的古土壤记录了古气候环境演化的重要信息,然而年代越老的地层由于受到后期持续的地质作用,使得古土壤面貌发生很大改变,增加了识别难度。美国Bryce峡谷广泛出露的古新统-始新统Claron组一直被认为是湖相石灰岩,却呈现整体氧化红色,并显示诸多古土壤特征。文章主要采用偏光显微镜和扫描电子显微镜来探究Bryce峡谷Claron组中古土壤特征,并结合X射线衍射特征分析矿物物相,结果表明:Bryce峡谷Claron组红色层是一系列成土深浅程度不同的古土壤层,表现为干旱土和淋溶土;地层中的碳酸盐主要是淀积在土壤下部的成土碳酸盐,碳酸盐富集也表现为土壤淀积的钙结核等钙积层,从土壤学看是钙积干旱土特征而非水中沉积的石灰岩层;深浅不同的红色层代表了粘化层和钙积层等土壤层次变化;不同颜色层代表着不同的形成环境:褐红色层形成于气候比较暖干时期,而灰白色层的形成环境比褐红色层更加湿润,可能每年雨季会形成临时性积水洼地,粉红色层的湿润程度介于褐红色层和灰白色层之间。综合上述分析,本研究不支持Claron组是终年积水古湖沉积环境的看法。Paleosol is a significant archive of paleoclimate and palaeoenvironment,which is a quality material to study past climate and environment.However,the difficulty of identification of the paleosol from the ancient strata is increased due to subsequently continuous geological processes,in which some paleosol features have been changed to a great extent.The Claron Formation from Paleocene to Eocene,widely exposed in Bryce Canyon,USA,have been considered as lacustrine limestone for a long time,but shows a generally red color of oxidation and characteristics of paleosol,indicating the deposit of paleosol occurred in the stratum.Taking the paleosol in the stratum as limestone to indicate the change of climate and environment,the reconstruction of paleoenvironment in this period is illogical.Therefore,the goal of this study is to identify the paleosol from the Claron Formation in Bryce Canyon,and then to discuss its forming environment based on characteristics of paleosol.The study area is located in Bryce Canyon National Park,western United States,37.5°~37.8°N,112°~112.3°W,and at altitudes of 2011~2775 m.The Claron Formation unconformably overlies the upper Cretaceous strata and is the most widely exposed strata in Bryce Canyon.Detailed field observation and sampling of the Claron Formation at Sunrise Point(37°37’42″N,112°09’46″W)and Sunset Point(37°37’21″N,112°09’57″W)was carried out,and 52samples were finally obtained according to the soil layers and different colors.Soil micromorphology is an effective method to identify paleosol from sedimentary rock.In this paper,the characteristics of paleosol of the Claron Formation in Bryce Canyon are mainly studied by polarized light microscope and scanning electron microscope,and the mineral facies are analyzed by X-ray diffraction.It was found in the field that evident palaeosol characteristicswell-preserved root traces,nest of hymenoptera,calcium nodules,reticulate structure,calcic horizons and argillic horizons-occurred in red layers of the stratum.F

关 键 词：土壤微形态 古土壤 碳酸钙 Claron组 古新统-始新统红色层 

分 类 号：P534.61[天文地球—古生物学与地层学] P588.2[天文地球—地质学]