Preliminary Construction of the Standard Stratotype of the Mesoproterozoic in China

The Mesoproterozoic is a key stratigraphic unit in the Proterozoic Eon, recording the critical geological processes ranging from the breakup of the Columbia supercontinent to the assembly of the Rodinia supercontinent. In the Chinese Stratigraphic Chart, the Mesoproterozoic (1.8–1.0 Ga) comprises the Changchengian, Jixianian, and Undefined System. Although the Mesoproterozoic outcrops in China are well-developed and well-exposed, the lack of a complete stratotype, disputes over chronological boundaries, and incomplete evidence chains have persisted, hindering the establishment of a comprehensive standard stratigraphic unit and thereby restricting the standardization of China’s Mesoproterozoic stratigraphic framework and its international correlation. This study systematically integrates research findings from typical stratigraphic sections of the North China Block and the Yangtze Block using multidisciplinary approaches, including zircon U-Pb dating, petrological and geochemical analyses, sedimentary sequence correlation, and stratigraphic contact relationship identification. It elaborates on the basic concepts and scientific basis for constructing a standard stratotype and preliminarily establishes a fundamental framework for the standard stratigraphic unit of the Mesoproterozoic in China. The study preliminarily determines 1.8 Ga (or 1.78 Ga) as the base boundary of the Mesoproterozoic. The Hangaoshan Group and Ruyang Group in the southern margin of the North China Block are selected as the lower stratotype of the Changchengian (1.8–1.65 Ga), while the Changcheng Group in the Yan-Liao area (1.65–1.60 Ga) serves as the upper stratotype of the Changchengian, collectively forming a complete Changchengian that corresponds to the international Statherian. The interval from the Gaoyuzhuang Formation to the Tieling Formation in the Jixian Section (1.60–1.40 Ga) is designated as the standard stratotype of the Jixianian, corresponding to the Calymmian. For the Undefined System, the Shennongjia Group in the northern margin of the Yangtze Block (1.4–1.0 Ga) is chosen as the primary candidate stratotype, corresponding to the international Ectasian and Stenian; the Xiamaling-Longshan-Jing’eryu formations in the northern margin of the North China Block are designated as a parastratotype of the Ectasian. Although this preliminary framework requires further verification, it represents a pioneering endeavor that can provide an isochronous stratigraphic framework for relevant research. It will support the National Commission on Stratigraphy of China in revising the Chinese Stratigraphic Chart and even offer references for the revision of Proterozoic stratigraphic boundaries in the International Chronostratigraphic Chart, which is of great significance for standardizing stratigraphic systems and enhancing China’s international influence in stratigraphy. This study was supported by the National Key R&D Program of China (Grant No. 2022YFF0800302), the NSFC (Grant Nos. U2444209, 42072135, 42502095), and the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (Grant No. 2025ZD1005300).