干旱区生态环境知识资源中心(Arid): 甘肃兰州盆地古近系泥岩的古盐度分析

Arid

	甘肃兰州盆地古近系泥岩的古盐度分析
其他题名	The palaeosalinity analysis of Paleogene mudstone in Lanzhou Basin,Gansu Province
	李智超 1; 李永项 1; 李文厚 1; 张云翔 1; 谢坤 1; 马瑶 2
来源期刊	地质科学
ISSN	0563-5020
出版年	2016
卷号	51 期号:4 页码:1344-1356
中文摘要	兰州盆地位于青藏高原东北部,祁连山以东,黄土高原以西,古近纪出露地层为细柳沟组、野狐城组和咸水河组下段。作为青藏高原寒区、东部季风区及西北干旱区的交汇地带,兰州地区新生代环境研究受到越来越多的关注,因此有必要对其沉积环境进行研究。本文通过对兰州盆地黄羊头地区古近系进行分段采样,并对泥岩样品的主量元素、微量元素及X射线衍射进行测定,运用硼法、B/Ga值及Sr/Ba值等方法定量一半定量分析兰州盆地古近系沉积时的古盐度特征,同时结合风化指数CIA值的变化特征,综合分析古近系的沉积环境。研究结果表明兰州盆地古近系细柳沟组、野狐城组及咸水河组下段Adams法古盐度值为9. 5%0~14. 0,平均值为11.8;Couch法古盐度值为8.2~12. 8,平均值为10. 8,为内陆半咸水一淡水湖泊。Adams法古盐度值与B/Ga值具有良好的正相关关系,而Adams古盐度值与Sr/Ba值相关性不明显,主要由于地层中生物对Sr的富集作用,导致Sr/Ba值偏大,表明Sr/Ba值不适用于生物富集地层的古盐度恢复。环境研究认为细柳沟期,气候湿润,以冲积扇沉积为主,水体较浅,盐度值较大;到野狐城中期水体加深,变为湖相沉积,气候温暖湿润,盐度值降低,同时存在明显的干冷气候间隙,该间隙期湖盆蒸发量大于补给量,盐度值升高;从野狐城晚期开始湖盆逐渐萎缩,以滨湖相沉积为主,到韩家井期变为河流相沉积,至甘家滩期再次转为湖相沉积,盐度值先升高后降低,但整体风化程度明显降低,表明从野狐城组晚期开始气候逐渐变冷变干。
英文摘要	The Lanzhou Basin is located on the northeast margin of the Tibet Plateau,bounded by the Qilian Mountain to the east and the Loess Plateau to the west,which outcrops mainly Paleogene Xiliugou Formation,Yehucheng Formation and lower part of Xianshuihe Formation. Much attentions have been paid for the Cenozoic environment in the Lanzhou area, as the conjunction of the Tibet Plateau cold region,eastern monsoon region and arid region of Northwest China. So it’s necessary to do researches on the sedimentary environment. Samples in the Palaeogene strata was collected in the different segment of Huangyangtou area in Lanzhou Basin. Major,trace elements and X-ray diffraction was conducted on these samples. The Palaeogene sedimentary environment was revealed by quantitative semi-quantitative analysis involving calculation using boron methods, B/Ga ratio,Sr/Ba ratio and the variation characteristics of chemical index of alteration. Results indicate Adams paleosalinity ranges from 9. 5 to 14. 0, with the mean value of 11. 8%o and Couch paleosalinity ranges from 8. 2 to 12. 8, with the mean value of 10. 8 in Xiliugou Formation,Yehucheng Formation and bottom of Xianshuihe Formation,which show that the Lanzhou Basin was a bracket water to fresh water lake. Adams paleosalinity value exhibits positive correlation with B/Ga ratio and no obvious correlation with Sr/Ba ratio. The Sr/Ba ratio is not suitable for reconstruction of paleosalinity,as Sr was absorbed by the biology in the stratum,which gives rise to the larger Sr/Ba ratio. The Environment research displays that the basin was chiefly characterized by alluvial fan,shallow water,high salinity values and humid climate during the Xiliugou age. With the increasing depth of water it gradually transformed into lake deposits and had low salinity water and warm-humid environment in the middle Yehucheng age. Meanwhile,there was an obvious dry-cold climate interval in that period,during which the lake basin evaporation capacity was greater than the recharge and salinity value increased. The lake basin gradually shrinked and was deposited in a lakeshore facies from the middle Yehucheng age, and into fluvial facies in Hanjiajing age into lacustrine facies in Ganjiatan age. The paleosalinity rose first and then fell, but the whole weathering degrees significantly reduced, which show that climate gradually became cold and dry since late Yehucheng age.
中文关键词	兰州盆地 ; 古近系 ; 古盐度 ; 沉积环境
英文关键词	Lanzhou Basin Paleogene Paleosalinity Sedimentary environment
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:5829704
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/234120
作者单位	1.西北大学地质学系, 大陆动力学国家重点实验室, 西安, 陕西 710069, 中国; 2.西安石油大学地球科学与工程学院, 西安, 陕西 710065, 中国
推荐引用方式 GB/T 7714	李智超,李永项,李文厚,等. 甘肃兰州盆地古近系泥岩的古盐度分析[J],2016,51(4):1344-1356.
APA	李智超,李永项,李文厚,张云翔,谢坤,&马瑶.(2016).甘肃兰州盆地古近系泥岩的古盐度分析.地质科学,51(4),1344-1356.
MLA	李智超,et al."甘肃兰州盆地古近系泥岩的古盐度分析".地质科学 51.4(2016):1344-1356.