PAN Ming1 HAO Yanzhen1,* LYU Yong1 SHAN Keqiang1 Sun Chengjie2
（1.Institute of Karst Geology，Chinese Academy of Geological Sciences，Guilin 541004, China;
2.Sinomine Resource Exploration Co., Ltd., Beijing 100089, China）
Abstract：The marine carbonate rocks of Middle-Late Silurian Licaiba Group in Baoshan area, Yunnan Province, China were collected as the research object to investigate the changes of sea level of this area during the Middle-Late Silurian and its causes, by using the methods of Sr isotope ratio, combining with the petrology and paleobiology. Among those methods, it is the first time to achieve strontium isotopic ratios in this area and the variation trend of sea level reflected by this method has a good coupling with the middle west of the United States. Results show that 87Sr / 86Sr values decrease gradually from first paragraph to the second, indicating that the sea level had gradually risen up during the same period of time; In the second paragraph,87Sr / 86Sr ratio is at a low level as a whole, showing obvious decreasing trend, and sample No.21 reaches the minimum value (0.7105), indicating the occurrence of obvious transgression. In the third paragraph, during a short geological periods, 87Sr / 86Sr values had exhibited the positive offset strongly, reaching the maximum value(0.72849), indicating the strong decline of sea level. In short, from the mid to late Silurian, sea level had showed the process of rising first and then falling. The strong deviation of Sr isotopes and the higher 87Sr/86Sr values in rocks are the reflection of orogenic and sea-level decline events during the same period.
Key words：Yunnan；Silurian；Sr isotope；carbonate rock；geochemistry
EARTH AND ENVIRONMENT Vol.46, No.2, Tot No.322, 2018, Page 129-137
