柴北缘西段古-新近纪古气候演化

古气候是陆相湖盆层序地层形成的主要沉积动力学因素之一.古-新近纪柴北缘西段及周边地区古气候演化过程复杂，目前就古气候演化过程还存在争议，利用地球化学方法对重点井的岩心和岩屑进行元素、TOC和碳氧稳定同位素测定.各古气候指标之间的相关性分析表明:Sr/Ba、Rb/Sr、Sr/Ca、TOC和氯离子含量可作为研究区恢复古气候的指标，δ13C与δ18O不能指示出该区的古气候演化过程.重点井全井段的岩屑氯离子含量分析表明:柴北缘西段古-新近纪古气候经历了干旱-潮湿-干旱的演化过程，从路乐河组到下干柴沟组上段沉积期古气候由干旱逐渐向潮湿的方向演化，呈现了7个旋回，湖盆水体盐度降低，总体来说气候潮湿，水体为微咸水；从上干柴沟组到狮子沟组沉积期古气候从潮湿向干旱方向演化，呈现了12个旋回，古水介质经历了微咸水至半咸水的演化过程. 

The Paleogene-Neogene Paleoclimate Evolution in Western Sector of Northern Margin of Qaidam Basin

Paleoclimate is one of the main sedimentary dynamic factors for the formation of sequence stratigraphy of continental basin. The Paleogene-Neogene paleoclimate evolution in western sector of northern margin of Qaidam basin and surrounding areas was complex, but now paleoclimate evolution remains controversial. The elements, TOC and C, O stable isotope content of key well cores and rock debris were measured by geochemical methods. Correlation analysis between paleoclimate indicators shows that: Sr/Ba, Rb/Sr, Sr/Ca, TOC and chloride ion content can be the paleoclimate recovery indicators, however, δ13C and δ18O can't indicate the paleoclimate evolution process in the study area. Analysis of rock debris chloride ion data of key wells shows that the paleoclimate evolution process in the study area is arid-humid-arid. From Lulehe Formation to upper Shangganchaigou Formation, the paleoclimate gradually evolved from arid to humid climate, including 7 cycles, and lake water salinity decreased, the climate was humid and water was brackish overall. From Shangganchaigou Formation to Shizigou Formation, the paleoclimate evolved from humid to arid, including 12 cycles, and brackish water changed to medium brackish water.