近7ka以来甘肃民勤青土湖沉积中的介形类及环境演化  

THE OSTRACODS ASSEMBLAGES AND ENVIRONMENTAL EVOLUTION OF THE QINGTU LAKE,MINQIN COUNTY,GANSU PROVINCE SINCE 7KA BP

作　　者：蔡燕凤[1] 张虎才[1] 王强[2] 常凤琴[1] 陈光杰[1] 王熊飞[1] 李华勇[1] 张自强[1] 段立曾[1] 

机构地区：[1]高原湖泊生态与全球变化实验室、云南省'高原地理过程与环境变化'重点实验室、云南师范大学旅地学院,650500 [2]中国地质调查局天津地质矿产研究所,300170

出　　处：《微体古生物学报》2013年第3期263-274,共12页Acta Micropalaeontologica Sinica

基　　金：国家重点基础研究发展计划(973计划)(编号:2010CB950202)资助研究成果

摘　　要：对河西走廊东段石羊河终端湖泊沉积的甘肃民勤志云村剖面研究,发现介形类7属11种,根据其地层分布特征划分出6个组合。通过分析介形类属种生态特征、组合变化和沉积岩性,结合14 C测年数据,对研究剖面所在的青土湖地区6 626aBP(Cal.a BP)以来的环境变化进行了初步探讨。分析结果表明:6 626—6 137aBP时期,湖泊水位由浅变深、水体由咸水变为淡水的状况交替出现,环境由暖干向冷湿转变;6 137—5 817aBP阶段,湖泊水位变浅,处于相对冷干的气候环境控制之下;5 817—2 978aBP期间,湖泊水位很浅且为淡水,为冷干的气候环境,逐渐恶化不利于介形类生存,系5ka余中全新世降温事件至晚全新世开始的环境状况;2 978—1 610aBP,环境继续恶化,水体曾一度退出剖面所在高度,反映的是干旱的恶劣环境;1 610—1 110aBP,气候干旱程度有所缓解,处于相对暖干的气候控制之下;1 110aBP以来,湖泊完全干涸,为典型的暖干状态下的风沙堆积环境,彻底结束了研究区湖泊的存在历史。Totally 11 species of ostracods belonging to 7 genera have been identified from the ZhiYun section which belongs to the terminal lake of the Shiyang River of east Hexi Corridor, Minqin county, Gansu Province and six ostra- cods assemblages can he distinguished. Based on the 14C dating, ostracods ecological characters and sedimentary li- thologicaI characteristics, the present paper discussed the environmental change of the Qingtu lake since 6 620 a BP.The result shows that from 6 626 to 6 137 a BP climate transform from warm-dry into cold-wet, with repeated deepe- ning and freshening water. From 6 137 to 5 817 a BP, the climate was cold and dry with the lake level turning to shal- low. During 5 817--2 978 a BP, the lake was very shallow with fresh waters. the climate was cold-dry and turned to unfavorable for ostracods gradually. It shows characteristics of the Holocene cooling event of ca. 5ka. From 2 978 to 1 610 a BP, the environment deteriorated continuously, and water body was once retreated from the height of the profile, which indicated severe dry environment. During 1 610--1 110 a BP, the climate condition was ameliorated but generally characterized by a relatively dry environment. From 1 110 a BP, the lake was totally dried up and turned to the desert with warm-dry environment.

关 键 词：介形类 7 KA BP环境演化青土湖 民勤 甘肃 

分 类 号：X131[环境科学与工程—环境科学]