摘要
位于西秦岭北缘的漳县盆地渐新统—中新统时期沉积大量湖相碳酸盐岩,其碳、氧同位素特征对揭示这一时期青藏高原东北缘的古环境和古气候具有重要意义。碳、氧同位素研究表明,漳县盆地湖相碳酸盐岩δ^(13)C_(V-PDB)值介于-7.6‰~-2.0‰,平均值为-5.04‰;δ^(18)O_(V-PDB)值介于-9.11‰~1.12‰,平均值为-2.10‰。δ^(18)O_(V-PDB)值与现代封闭湖泊一致,显示漳县盆地在渐新统—中新统是封闭湖泊,古温度平均值为17℃,比现代平均气温高10℃左右,且剖面中含有石膏和芒硝,表明漳县盆地在渐新统—中新统处于较温暖干旱的气候环境;同时,古盐度Z值平均值为116,所以漳县盆地在该时期是一个封闭的半咸水陆相湖泊。通过δ^(13)C_(V-PDB)值可知,其生产力较高,但由于古湖水中含有硫酸盐细菌,还原反应影响有机质的保存,故δ^(13)C_(V-PDB)值偏负。漳县盆地渐新统—中新统古环境和古气候变化与邻区西宁盆地、循化盆地、临夏盆地和天水盆地的记录基本一致,都是逐渐干旱化。造成这种变化的原因主要是全球气候变化,与青藏高原的强烈隆升关系不大。
Zhangxian basin,located in the northern margin of the west Qinling mountains,deposited a large number of lacustrine carbonate rocks during the Oligocene-Miocene.Its C and O isotopic characteristics are of great significance to reveal the paleoenvironment and Paleoclimate of the northeastern margin of the Qinghai Tibet plateau during this periodδ^(13)C_(V-PDB)values ranged from-7.6‰to-2.0‰,with an average of-5.04‰,δ^(18)O_(V-PDB)values ranged from-9.11‰to 1.12‰,with an average of-2.10‰.δ^(18)O_(V-PDB).value is consistent with that of the modern closed lake,which indicates that Zhangxian basin is a closed lake in Oligocene Miocene.The average paleotemperature is 17℃,which is about 10℃higher than the modern temperature,and the profile contains gypsum and mirabilite,which indicates that Zhangxian basin is in a warm and arid climate environment in Oligocene-Miocene,and the average paleosalinity Z value is 116,Therefore,Zhangxian basin was a closed semi saline continental lake in this period.adoptδ^(13)C_(V-PDB)value shows that the productivity is high,but the reduction reaction affects the preservation of organic matter because of the sulfate bacteria in the ancient lake waterδ^(13)C_(V-PDB)was negative.The Oligocene-Miocene paleoenvironment and paleoclimate changes in Zhangxian basin are basically consistent with the Oligocene-Miocene records of Xining basin,Xunhua basin,Linxia basin and Tianshui basin,all of which are gradually arid.The main reason for this change is the global climate change,which has little to do with the rapid uplift of the Qinghai Tibet plateau.
作者
杨晓璇
李雪峰
郭进京
赵海涛
YANG Xiaoxuan;LI Xuefeng;GUO Jinjing;ZHAO Haitao(School of Geology and Geomatics,Tianjin Chengjian University,Tianjin 300384,China)
出处
《西北地质》
CAS
CSCD
北大核心
2022年第2期106-115,共10页
Northwestern Geology
基金
国家自然科学基金项目“西秦岭北缘断裂带新生代构造变形几何学运动学分析及构造变形演化”(41772215)
天津城建大学科研启动项目“西秦岭北缘断裂带构造活动特征研究”(05147201)资助。
关键词
西秦岭
青藏高原东北缘
碳氧同位素
古环境
古气候
west Qinling
Northeast margin of Qinghai Tibet plateau
carbon and oxygen isotopes
paleoenvironmen
paleoclimate
