English: Sih-de Fossil Valley shares majority of fossils all over Jia-sian. In the past, the place was known for its abundant resources of large fossils such as Jia-sian Pleurotomariidae, Tonnidae, Melongenidae, Acharax, Cucullaea, Atrina pectinata, flamboyant Pectinidae, Korean Lucinidae. Fossils in Jia-sian can be dated back to Miocene Period and belongs to Mt. Guang-dao sandstone layer and also a minority of Nan-jhuang Layer. It is the main composite of the mountains in the southwestern region. The sandstone in Guangdao Mountain has a harder composition than other types of stones in the area, enabling it to withstand weather erosion. This is the only reason why the major terrain in the region is the steeper hill. The sandstone layer, especially in the west of Nan-zih River, opened up five to six times due to a geological fault. This resulted in rows of mountain ridges. The higher part of the ridge has more Guangdao Mountain sandstone, which is younger than Nan-jhuang Layer in the side wings. The two layers belong to Ali Mountain in the category of a local topographic classification.