The Nanxiong fault zone is a large-scale extension detachment structure. According to the results of Ar-Ar laser stepheating dating of the syntectonic muscovite separated from a mylonite sample in the Nanxiong fault zone

combining with the field surveying and microstructure analysis

the initial extension of the Nanxiong fault zone occurred at 117.3±2.7 Ma in Early Cretaceous.The strong extension and ductile shearing of the fault zone took place at the end of the Early Cretaceous or the beginning of the Late Cretaceous with an Ar-Ar plateau age of 94.6±0.4 Ma. Two obvious latestage thermal perturbations are revealed with the Ar-Ar ages of 88.9±1.0 Ma and 81.1±2.0 Ma. The Ar-Ar chronology data of the Nanxiong fault zone provide a new geochronological constraint on the Cretaceous lithospheric extension in South China.The transition stage from the Early Cretaceous to the Late Cretaceous is an important epoch of the lithospheric extension in the study.