REE geochemistry of the Upper Jurassic-Lower Cretaceous carbonate rocks and palaeoclimates in the Nadigangri region,Qiangtang Basin

The relationship between the vertical variations in REE and palaeoclimates in the Nadigangri region,Qiangtang Basin is based on the REE abundances and distribution patterns,and vertical distribution of REE amounts(ΣREE) in integration with total organic carbon(TOC) contents,EF_Mn and Sr/Cu ratios for the carbonate rocks from the Upper Jurassic to the Lower Cretaceous Suowa Formation in the Nadigangri region,Qiangtang Basin.The REE contents range between 8.32 and 81.3μg/g,with an average of 45.3 μg/g(not including Y).LREEs are relatively enriched,and display a slightly right-leaning pattern.There is a good correlation between REE and total organic carbon contents,and a negative correlation between REE and EF_Mn and Sr/Cu ratios.The higher values of ΣREE represent relatively humid climatic conditions,while the lower values of ΣREE represent xerothermic climatic conditions.It is inferred from the REE distribution and sedimentary environments that the Nadigangri region,Qiangtang Basin once went through the alternating changes of xerothermic and warm humid climatic conditions during the Late Jurassic to the Early Cretaceous.