The tuffs from the Jiulongshan Formation in the Chengde Basin, northern Hebei: LA-ICP-MS zircon U-Pb age dating and its geological implications

The first LA-ICP-MS zircon U-Pb age dating is measured for the tuffs from the Jiulongshan Formation in the Chengde Basin, northern Hebei, and gives a weighted average value of ²⁰⁶Pb/²³⁸U ages of 164.1±1.3 Ma. The authors contend from the above result and 1:50 000 geological surveying of the Xinzhangzi and Chengde Sheets that the Jiulongshan Formation should be dated at 158-164 Ma, i. e., the late Middle Jurassic to the early Late Jurassic, or the Oxfordian-Callovian in the international stratigraphic chart. The result of research may provide an important evidence for the division of the Jurassic stratigraphic sequences, construction of chronostratigraphic framework, and further study of Mesozoic magmatic-tectonic evolution in the Yanshan area, northern China.