PTME后华北板块南缘生物复苏后期古环境特征:来自豫西登封中三叠统二马营组的证据  

Paleoenvironmental characteristics in the late stage of biosphere recovery in the southern margin of the North China Plate after PTME—evidence from the Middle Triassic Ermaying Formation

作　　者：邢智峰[1,2,3] 张湘赟 李婉颖 齐永安 郑伟[1,2,3] 吴盼盼 张立军[1,2,3] XING Zhifeng;ZHANG Xiangyun;LI Wanying;QI Yong’an;ZHENG Wei;WU Panpan;ZHANG Lijun(Institute of Resources and Environment,Henan Polytechnic University,Jiaozuo 454003,China;Key Laboratory of Biogenic Traces and Sedimentary Minerals of Henan Province,Jiaozuo 454003,China;Central Plains Economic Zone Coalbed Methane and Shale Gas Collaborative Innovation Center,Jiaozuo 454003,China)

机构地区：[1]河南理工大学资源环境学院,河南焦作454003 [2]河南省生物遗迹与成矿过程重点实验室,河南焦作454003 [3]中原经济区煤层气与页岩气协同创新中心,河南焦作454003

出　　处：《地学前缘》2023年第5期491-509,共19页Earth Science Frontiers

基　　金：国家自然科学基金项目(41772110,41872111,41902113);河南理工大学创新型科研团队支持计划项目(T2022-05);河南理工大学博士基金项目(B2020-54)。

摘　　要：三叠纪是二叠—三叠纪生物大灭绝(PTME)之后生态系统恢复的重要时期,也是构造格局的重要转型期。中三叠世生态系统已逐渐恢复,处于生物复苏的后期,该时期的古环境特征、古生物面貌都对生态系统的恢复具有重要意义。本研究通过对豫西地区登封白坪中三叠统二马营组剖面的详细实测和样品的测试分析,运用沉积学和地球化学等方法,进行古环境特征分析。结果表明:(1)二马营组下段以黄绿色细粒长石砂岩与紫红色泥岩不等厚互层为主,发育曲流河的4个沉积旋回;中段底部以厚层黄绿色长石石英砂岩为主,上部出现频繁的砂泥互层,为滨浅湖沉积;二马营组中下段经历了由粗组分为主向细组分为主的多次转变,后期由河流相逐渐转变为滨浅湖相沉积。(2)地化样品中Mg/Ca以及Sr/Cu值(1.8~5.2,均值为3.5)均较低,显示二马营组整体处于温暖湿润的气候条件;Sr/Ba(0.15~0.42,均值为0.29)、∑LREE/∑HREE、Ce异常指数以及氧化还原敏感元素U、V、Cr、Ni、Co等的比值均显示二马营组沉积期为氧化条件为主的陆相淡水沉积环境。综上所述,豫西登封二马营组为一套典型的河湖相沉积,与下伏和尚沟组相比,在古气候方面出现明显的转变,由干旱炎热逐渐转变为温暖湿润的气候,为生态系统的恢复起到了重要的作用。The Triassic is an important period of ecological recovery after the Permian-Triassic Mass Extinction(PTME)and also an important tectonic transition period.As ecosystem recovery was near completion in the Middle Triassic while biosphere recovery was in the late stage,the environmental and paleontological condition of this period was greatly important to a full ecological recovery.Based on detailed geologic profile study and sample testing conducted in the Middle Triassic Ermaying Formation in Baiping,Dengfeng,western Henan,the Middle Triassic sedimentary environment and paleoenvironmental changes were analyzed by sedimentology and geochemical methods.The results show that(1)The lower member of the Ermaying Formation(layers 218)developed four sedimentary cycles under meandering river environment,where mainly composed of yellow-green fine-grained feldspar sandstone and purplered mudstone with unequal thickness interbeds.The middle member(layers 1925)is dominated by thick yellow-green feldspathic quartz sandstone in the bottom and frequently interbedded mudstone and sandstone in the upper,which is the shore-shallow lake deposition.From the lower to the middle member,Ermaying Formation experienced alternating depositions of coarse-grained and fine-grained sediment,and gradually changed from fluvial facies to shore-shallow lake facies.(2)The low Mg/Ca and Sr/Cu ratios(1.85.2,averaging 3.5)of samples indicate the Ermaying Formation was deposited under warm and humid climate conditions.The Sr/Ba(0.150.42,averaging 0.29)and∑LREE/∑HREE ratios,Ce anomaly index and elemental ratios of redox sensitive elements(U,V,Cr,Ni,Co)in the Ermaying Formation indicate its sedimentary environment type is continental freshwater under oxidation conditions.In summary,the Ermaying Formation has typical fluvial-lacustrine sedimentary facies,and,compared with the underlying Heshanggou Formation,its paleoclimate obviously changed from arid and hot to warm and humid,which plays an important role in the ecosystem recovery.

关 键 词：中三叠统 二马营组 古环境 登封地区 生态系统恢复 

分 类 号：Q915[天文地球—古生物学与地层学] P534.51[生物学—古生物学] P532