三叠纪灰岩出现一正断层，发育断层角砾岩。断层带伸入河中，生成一碳酸盐岩溶溶洞，人称鳄鱼潭。早三叠世是三叠纪三个世之首，距今约2.5亿年。

Triassic limestone arise a normal fault, forming fault breccia. Fault zone stuck into river and generated a carbonate karst cave, so it was calledas crocodile pond.The Early Triassic is the first of the three Triassic ages, about 250million years ago.