Four isolate barrier beds occurened usually in boundary surface of each internal architecture unit in channel sandbody, i. e. find bed, muddy pebble bed, plant clasts bed and diagenic bed.

在河道砂体内部成的不同次实体界面上，通常存在着4种挡，即细粒挡、泥砾挡、植碎屑挡和成岩挡。