The planation surface (700-950m) in the west of Tinh Tuc forming from terrigenous sediments of Song Hien overlaying on Carboniferous-Permian limestones. It is possible to observe the characteristics from here:
− Residual karst landscape with Fenglins, fengcongs was re-exposed when covering terrigenous sediments were eroded strongly;
− The pyramids with sharp edges , spikes in the water divide area
− Planation surface ( 700-950m) in the east of Tinh Tuc and the valley of Nguyen Binh river with alluvial and its terrace level I.
− Tinh Tuc basin. where tin ores and is exploited, and remnant of old bottom of this basin (Figure VI.2.18).
− Karst canyon is in the top part in the east of this basin.
Figure VI.2.18. Remnant of old bottom of this Tinh Tuc basin