POTENTIAL VALUE OF THE STRONTIUM ISOTOPE STRATIGRAPHY IN DATING MARINE SEDIMENTS
ZHANG Meng, HUANG Si jing, ZHANG Yue, CHEN Xiao dong, QIN Zhi peng (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, China)
The strontium isotope stratigraphy (SIS) is predominantly used for correlation and dating of marine sediments. The recent proliferation of strontium isotope stratigraphic studies has clearly documented that the world sea level change is the main and primary factor to control the strontium isotopic composition, i.e. the variation through geological time is the marine 87 Sr/ 86 Sr. The 87 Sr/ 86 Sr record can be used to date and correlate marine sediments, estimate the duration of stratigraphic gaps, estimate the duration of biozones and stages, and underpin speculation about major geochemical cycles. When SIS is used for dating, the quality of its numeric date depends upon the following several factors: the preservation quality of the original 87 Sr/ 86 Sr of a sample, whether artifacts are introduced during 87 Sr/ 86 Sr measurement , the slope of the curve of 87 Sr/ 86 Sr against numeric age, the accuracy of the age model used to assign a numerical calibration to the isotope curve, and finally, the way of the best fit curve and its associated uncertainty envelope are fitted to the Sr isotope date and used to derive a numeric age.