最近在天津蓟县东水厂村附近中元古代高于庄组三段(即张家峪亚组)下部白云岩中发现了一层15 cm厚的凝灰岩夹层,测得其锆石LA-MC-IC......

Along the Proterozoic stratigraphic sections of Jixian, Tianjin, the ??13C values of carbonates are mostly negative in t......