Zircon U-Pb geochronology of tuffite beds in the Baishugou Formation: Constraints on the revision of Ectasian System at the southern margin of the North China Craton

The Xiamaling Formation of 1.4-1.35 Ga in Jixian Section and adjoining areas represents a unique Ectasian Period (Mesoproterozoic) sedimentary sequence in the North China Craton (NCC). Studies carried out during the last decade have contributed significantly in improving our understanding about the Ectasian sedimentation tectonics in the NCC during this transitional interval between the breakup of Supercontinent Columbia and the assembly of Rodinia. The present study reports, for the first time, tuffite beds interlayered with carbonaceous-siliceous slate-phyllite in the upper Baishugou Formation (western Henan Province), at the southern margin of NCC. The LA-MC-ICPMS U-Pb geochronology of zircons from two tuffite samples has yielded almost identical ages of 1330 +/- 10 Ma (MSWD=0.43,N=38) and 1332 +/- 10 Ma (MSWD=0.90,N=24), that constrain a 1.33 Ga depositional age (Ectasian Period) for the Baishugou Formation. A close similarity in lithological characteristics and their respective superimposed lithostratigraphic relationships of the Baishugou and Xiamaling formations, underline a comparable depositional environment for them. The high-precision geochronology data on the Baishugou Formation would stimulate a relook into the Meso-Neoproterozoic chronostratigraphic framework of the NCC, and further research would lead to a comprehensive understanding of the geological evolution of the NCC during Ectasian Period and its correlation with analogous global events.