The Standard Stratigraphic Section of the Mesoproterozoic Era

　　Located in the northern mountainous area of Jixian County, this section starts at Changzhou Village in the northeast of the county and extends in a northeast-to-southwest direction, layer by layer, until it reaches Fojun Mountain near the county town. Here lies a well-preserved ancient stratigraphic section, with a total thickness of 9,197 meters and a profile length of approximately 24 kilometers. It is renowned for its clearly defined top and bottom boundaries, simple structure, minimal metamorphism, and abundant ancient biological fossils. It is estimated that the geological age of this stratum ranges from about 1.9 billion to 850 million years ago. It is divided from oldest to youngest into three stratigraphic units: the Changcheng System, the Jixian System, and the Qingbaikou System, comprising 11 groups and 105 layers. In 1984, the State Council approved the designation of this profile as China’s first national-level geological nature reserve. A museum has been established here, integrating geological data, academic research, and natural landscape, filling a gap in this category of nature reserves in China.