永城煤田二叠纪网状河流沉积体系

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

永城煤田二叠系三、四煤组地层中，沉积相的空间配置、砂体特点等均显示出网状河流沉积体系的特征。这里的网状河流体系是在盆地整体沉降的背景中，在地形平坦、坡降低的三角洲平原上，受同沉积构造控制发育起来的。同沉积断裂和坳陷活动创造了长期相对低洼、可供河道发育的地形条件，加上繁茂的植被、沉降速度与补偿速度大体均衡、突发性海侵等因素的共同影响。

In the third and fourth coal measures of the Permian strata in the Yongcheng coal field,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.