The anastomosed fluvial depositional systems in the Permian coal measures of the Yongcheng coalfield, Henan

In the third and fourth coal measures of the Permian strata in the Yongcheng coalfield, Henan, the spatial distribution of sedimentary facies,the features of channel-fill sandstones and other evidences have reflected the characteristics of anastomosed fluvial depositional systems, which are developed on the deltaic plain with flat topography and lower gradients against a background of basin subsidence,and governed by synsedimentary structures. The synsedmentary faulting and downwarping have created the permanent low-lying topographic conditions for the long-term and steady development of the anastomosed channels. Furthermore, the luxuriant vegetation,approximate balance between tectonic settling velocity and compensating velocity, and abrupt marine invasion also allow for the long-term and steady development of the above-mentioned channels.