Late Cretaceous to early Paleogene strontium isotopic stratigraphy in the Gamba area, Tibet

Abstract：In the geologic record, the strontium isotopic composition of marine carbonate reflects the evolution of the global strontium balance between reservoirs. This balance is thus inherently related to changes in sea level through time. Late Cretaceous-early Paleogene strata in the Gamba area, Tibet, are well developed. Strontium isotope analysis was performed on 26 unaltered oceanic carbonate samples from sections in Zongshan and Zongpu and the evolutionary curve drawn by the data obtained is well correlated with the global oceanic strontium isotope record. The negative extreme values of the curves are nearly consistent with the negative extremes of the stratigraphic boundaries. The negative peak value (0.707612) of the curve of the Zongshan section corresponds to that of the Upper/Lower Cretaceous boundary, and the negative extreme value (0.707761) of the curve of the Zongpu section corresponds to that of the Paleocene/Eocene boundary. The Late Cretaceous-Paleogene strontium isotope curve also agrees with the known sea level change. In addition, the cause for the change in strontium isotope values in the Gamba area is discussed.