Pyroclastic flow deposits are termed flow units by R. S. J. Sparkes et al. (1973). In the Gulai area, eastern Zhejiang, a typical section on the southeastern margin of the Jiangcun volcanic depression consists from the base upwards of basesurge deposit (a), pyroclastic flow deposit (b, i. e. flow unit) and air fall deposit (c). Its total thickness ranges from 15 to 50 m. The flow unit is composed of a fine-grained basal layer (b_1) and a coarse-grained main portion (b_2). It is mainly characterized by rever...