Formation contact relationship-- channel scouring contact

Large scale channel scouring contact (Figure 4-23) develops in the east-west direction Yardang group in the Yardang scenic spot. The bottom part is 1.5 to 2 meters thick coarse sand layer, in which parallel bedding and cross-bedding develop. The upper part is 1.5 m thick muddy layer, with the sandstone lens overlying. The scouring face shows as an angled arc, the bottom of which develops syngenetic boulder and clay whose gravel separation is poor and more angular, and the maximum particle size is 0.1 m. Parallel bedding develops in the bottom while large scale cross-bedding and trough cross-bedding develop in the middle and upper part, which reflects the Quaternary fluvial and alluvial sedimentary environment.

Figure 4-23 river channel scouring contact