Strontium isotope evolution: responding to sea-level fluctuation --an example of ordovician in middle tarim area

摘要

The Strontium isotope composition of autogenetic minerals can reflect the sea level fluctuation trend during the minerals were deposited. The analyses of the ~87Sr/~86Sr Sr ratio of Ordovician show the sea level dropped in Early Ordovician, and then the sea level rose Continuously and stayed above the average level in Middle and Late Ordovician in middle Tarim area. The study of isotope geochemistry draws the same conclusion as that of the Sequence stratigraphy, or rather, the middle Tarim area developed two sedimentary Sequences in Early Ordovician and the Middle-Late Ordovician respectively.