| 柴达木盆地昆北地区路乐河组/下干柴沟组泥岩地层地球化学特征及古环境意义 |
| |
| 引用本文： | 余平辉,马锦龙,廖建波,李志勇,邸俊.柴达木盆地昆北地区路乐河组/下干柴沟组泥岩地层地球化学特征及古环境意义[J].干旱区地理,2020,43(3):679-686. |
| |
| 作者姓名： | 余平辉 马锦龙 廖建波 李志勇 邸俊 |
| |
| 基金项目： | 国家科技重大专项（2017ZX050002-003)资助 |
| |
| 摘 要： | 柴达木盆地昆北地区位于柴达木盆地西部南区的昆仑山前缘，该地区构造活动频繁，地层完整，是研究古环境和古气候理想地区。通过采集昆北地区切26井新生界下部泥岩样品，对其进行微量元素分析。结果表明：在地层界线附近，路乐河组Cu、U、Cr、Sr元素含量平均值分别为18.34×10-6、3.24×10-6、141.68×10-6、107.10×10-6,下干柴沟组下段为28.17×10-6、3.35×10-6、192.07×10-6、217.05×10-6。下干柴沟组下段微量元素有明显增大趋势，指示沉积环境发生变化。U与陆源碎屑来源指示元素Th相关性差（R2=0.174 5)，表明U主要为自生成因，因此其含量的增加可以指示原始沉积水体还原程度的增强。Cr与U表现为弱相关（R2=0.420
9),表明水体环境的变化对Cr的富集有一定的影响；氧化还原指标U/Th、V/Cr表明研究区古环境为氧化水体沉积环境，U/Th、V/Cr指标在下干柴沟组下段变大表明水体加深，还原性增强。利用Sr/Cu比值变化以及结合化石种属演化等推测地层界线附近古气候经历了干旱—湿润—干旱的旋回变化。
|
| 收稿时间： | 2019-05-15 |
Geochemistry and paleoenvironment significance of
Lulehe Formation/Xiaganchaigou
Formation located in the north area of Qaidam Basin |
| |
| YU Ping-hui,MA Jin-long,LIAO Jian-bo,LI Zhi-yong,DI Jun.Geochemistry and paleoenvironment significance of
Lulehe Formation/Xiaganchaigou
Formation located in the north area of Qaidam Basin[J].Arid Land Geography,2020,43(3):679-686. |
| |
| Authors: | YU Ping-hui MA Jin-long LIAO Jian-bo LI Zhi-yong DI Jun |
| |
| Abstract: | Kunbei area of Qaidam Basin is in front of Kunlun
Mountains in the southern part of Western Qaidam Basin,Qinghai
Province,China.It is adjacent to the Qinghai-Tibet Plateau.Therefore,the
tectonic activities are unusually frequent.Furthermore,very thick sedimentary
strata have remained from the Cenozoic Era.Therefore,it is an ideal area for
studying the paleoenvironment and paleoclimatic evolution.Fresh drilling core
samples were collected,and trace elements were detected in the lower Cenozoic
mudstone samples of Well Qian 26 in Kunbei area.The changes of trace element
contents and their correlations were studied,and the ratio of characteristic
elements was further calculated.The results showed that the average contents of
Cu,U,Cr,and Sr in the Lulehe Formation were 18.34×10-6,3.24×10-6,141.68×10-6,and
107.10×10-6,respectively,near the stratum boundary,while
those in the Lower Ganchaigou Formation were 28.17×10-6,3.35×10-6,192.07×10-6,and
217.05×10-6,respectively.Compared to the
Lulehe formation,the content of trace elements in the lower part of the
Xiagangchaigou Formation increased obviously,indicating that the sedimentary
environment has changed.The correlation between U and Th,the indicator elements
of terrigenous clastic rocks,was poor (R2 = 0.174 5).This indicates that U was mainly autogenic,so the increase in U content
may indicate an increase in the degree of reduction of the original sedimentary
body.The weak correlation between Cr and U R2=
0.420 9) indicates that the change of water environment had some influence on
the enrichment of Cr.The correlation between Cu and U was poor (R2 = 0.123 1),indicating that
the original sedimentary environment had limited influence on the enrichment of
Cu,and the increase of its content may be more controlled by the deposition of
organic matter and terrigenous debris sources.The correlation between Sr and U
was poor (R2 = 0.192
9),indicating that water environment was not the main factor controlling Sr
enrichment.The values of U/Th and V/Cr were 0.19-0.35 and
0.10-0.13,respectively,indicating that the paleoenvironment of the study area
was oxidized water depositional environment.The enhancement of U/Th and V/Cr
indices in the lower part of Lower Ganchaigou Formation indicates that the
water body deepened and the reducibility increased.Based on the Sr/Cu ratio and
the evolution of fossil species,it is inferred that the paleoclimate near the
stratum boundary has undergone drought-humidity-drought cycles.It can be seen
that the evolution of dry and wet paleoclimate led to changes in water depth,which
in turn led to changes in the redox conditions of the water environment.This is
also the reason for the differential enrichment of trace elements. |
| |
| Keywords: | |
|
| 点击此处可从《干旱区地理》浏览原始摘要信息 |
|
点击此处可从《干旱区地理》下载全文 |
|
