Chronostratigraphic division of the Jixi Group in eastern Heilongjiang Province and its geological significance

Abstract：Using the latest paleontological, magnetostratigraphic and chronological data and the lasting time of the high-resolution sequences, the authors have made a detailed chronostratigraphic division of the Jixi Group and determined the Jixi Group formed in the Early Cretaceous early Valaginian to middle Albian. In the group, the Didao Formation formed at 130.9±128.3 Ma, the Chengzihe Formation at 125.1±116 Ma, the Muling Formation at 116±106.9 Ma, and the Dongshan Formation at 106.9±101.7 Ma. Through a correlation between the lake-level fluctuation curve of the second-order sequence in the Jixi Group with the curve of global eustasy, it is confirmed that the tectonic movement and paleoclimatic change of the Jixi and Boli basins had the same tectonic setting as the global eustasy. This result provides a precise chronological basis for the high-precision stratigraphic division and an analysis of basin tectonism and the mechanism for land and sea changes in Jilin and eastern Heilongjiang in the Early Cretaceous.