Geochemical Characteristics of the Late Cretaceous Lower Zhoutian Formation in the Jitai Basin, Southeast China: Implications for palaeoenvironment and provenance

Abstract

Major, trace and rare earth element geochemistry of the late Cretaceous lower Zhoutian Formation from the Jitai Basin of Southeast China were measured by inductively coupled plasma mass spectromentry (ICP-MS) analysis. The paleoclimate, paleo-environment and provenance of lower Zhoutian Formation in the Jitai Basin are analyzed in detail with these data.According to the research, the range of Sr/Cu values is wide, which indicates the changeable palaeoclimate, the curves of FeO/MnO and Al2O3/MgO are negatively correlated with the Sr/Cu curves. These changes indicate that the palaeoclimate of the late Cretaceous lower Zhoutian Formation in the Jitai Basin was divided into two parts. The lower part experienced two cooling events; the upper part was dominated by warm humid climate.The changes of B/Ga and Sr/Ba curves are similar to Sr/Cu curves. According to these values, the salinity of the late Cretaceous lower Zhoutian Formation in the Jitai Basin was consistent with palaeoclimate. The salinity of lower part changed from salt water to fresh/brackish water. The upper part was mainly fresh/brackish water, and there were many changes from fresh/brackish water to salt water. The values of Ni/Co, V/Cr, V/(V + Ni) and Ce/Ce* are relatively stable, indicating a long-term oxidation environment. The diagrams of La-Th-Sc, Th-Sc-Zr/10, La/Th-Hf and sandstone-siltstone background function show that the provenance in lower Zhoutian Formation mainly is a mixture of upper crust felsic sediments and old components.