Paleo-environmental Significance of Oxygen and Carbon Isotopic Records in Lacustrine Limestone from Anjihaihe Formation, Northern Tianshan(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2016年第03期
- Page:
- 398-409
- Research Field:
- 水资源与环境
- Publishing date:
Info
- Title:
- Paleo-environmental Significance of Oxygen and Carbon Isotopic Records in Lacustrine Limestone from Anjihaihe Formation, Northern Tianshan
- Author(s):
- LI Qian; TIAN Xiao-ru; HU Han-wen; GUO Zhao-jie
- 1. Key Laboratory of Orogenic Belts and Crustal Evolution of Ministry of Education, Peking University, Beijing 100871, China; 2. School of Earth and Space Sciences, Peking University, Beijing 100871, China
- Keywords:
- paleoenvironment change; Anjihaihe Formation; Cenozoic; lacustrine limestone; oxygen and carbon isotopes; sedimentary facies; tectonic uplifting; Tianshan
- PACS:
- P66;X141
- DOI:
- -
- Abstract:
- Oligocene Anjihaihe Formation in northern Tianshan represents lacustrine sedimentary before the rapid uplift of Tianshan in Cenozoic. The variation of sedimentary facies at the top of Anjihaihe Formation and overlying Shawan Formation indicates the influence of the uplift of Tianshan. Field measurement was carried out in Anjihaihe section, and lacustrine limestone was sampled from Anjihaihe Formation for sedimentary facies analysis and oxygen and carbon isotopes analysis. The lacustrine environment during Oligocene was reconstructed. Results reveal that Anjihaihe Formation is mostly formed in semideep to deep lacustrine environment and in shore environment at the top. δ18O values and δ13C values in Anjihaihe Formation are relatively higher than normal lakes; δ18O values of the middle part are slightly higher than those of lower and upper parts; at the top of Anjihaihe Formation, δ18O values drift negatively significantly. On the other hand, δ13C values are much higher in the upper and top than those in the middle and lower parts with few exceptions. Regional climatic data and simulation of atmospheric circulation indicate that the variation of isotope in Oligocene is not the result of air mass change and monsoons. Given the data of oxygen and carbon isotopes, along with sedimentary facies analysis, it is concluded that Anjihaihe Formation is characterized by a worm and humid environment while the subsequent top part witnesses an obvious fall in temperature and the climate turns cool and dry. Considering that global climate showes no distinct change at the end of Anjihaihe Formation, this regional change may be to a large degree relate to the active uplift of Tianshan caused by the far field effect of IndiaEurasia Plate collision during Cenozoic.
Last Update: 2016-06-02