STRONTIUM ISOTOPE AND TRACE ELEMENT CHARACTERISTICS OF MARINE CARBONATE AND SEA LEVEL FLUCTUATION

94 carbonate samples were collected from Gaoyuzhuang Formation of Mesoproterozoic in Jibei depression to study geochemistry of Sr isotope and trace elements and to analyze its responses to sea-level fluctuation based on sedimentary characteristics of the Formation.The results showed that both strontium isotope and some trace elements gave the same conclusion of the ancient water depth and the sea level fluctuation as that of the study of lithostratigraphy.The early period of Gaoyuzhuang was a vast shallow-water carbonate platform zone.The sea level rose continuously during the middle period of the time and yielded a carbonate platform basin with the depth of water.Late time saw the sea level drop.There is a negative correlation between the ⁸⁷Sr/⁸⁶Sr ratio and the sea level fluctuation.The strontium isotope can reflect the sea level fluctuation trend during deposition of the minerals,and can be used to divide sequence stratigraphic units of the marine carbonate Formation.The study of trace elements indicates that some elements such as K, Ti,V,Rb,Th and Sc have remarkable response to the sea level fluctuation.They increased with the depth of water.Trace element characteristics can be regarded as an important mark in sea level fluctuation and sedimentary facies analysis.