In the initial stage of Devonian Period, seawater is onlaped gradually from the south to the north caused by transgression, so the bottom part of Devonian system is constituted by a set of transgressive clastic sedimentary rock.

• 泥盆纪初期 ,海水由南而北逐渐海侵超覆 ,在泥盆系的底部形成一套海侵碎屑岩系地层 ;