A Study on the Paleoclimate and Sedimentary Environment of the Upper Kuli Formation in the Hailar Basin

Abstract The Kuli Formation in the Hailar Basin has a wide distribution range, complex and variable lithology, and oil and gas indications during field investigations, which has great research significance and value. In order to better understand the paleoclimate and sedimentary environment of the Upper Kuli Formation, this article uses three methods for the first time: heavy mineral analysis, sporopollen fossils identification, and inorganic element analysis. Based on the characteristics of heavy mineral assemblages, sporopollen fossils identification, and element analysis correspond to the five bottom layer combinations of heavy mineral analysis, analyzing their respective combination characteristics and change patterns. With a more comprehensive perspective and higher time resolution, Cross validation improves the accuracy and credibility of its inference. The results indicate that the Upper Kuli Formation can be divided into five combinations from bottom to top. The paleoclimate underwent a transition from a humid environment to a drier environment. The sedimentary environment has undergone a transition from a deep-water environment to a shallow water environment, transitioning from dynamic, rapid sedimentation, and strong terrestrial influences to a sedimentary environment dominated by more static water, chemical precipitation, and diagenesis. This study combines different geological and geochemical analysis methods to provide strong basis for inferring the paleoclimate and sedimentary environment of the Upper Kuli Formation. The research results are of great significance for interpreting geological changes such as paleoclimate change and ecosystem evolution.