Depositional environments of limestones from the Taiyuan Formation in the North China Block interpreted from REE proxies

The predominantly calcareous Taiyuan Formation was formed during the Late Paleozoic period in the southern part of the North China block in the eastern Palaeotethys. We present the rare earth elements (REE) and petrography data from nine limestone beds in the Zhangji mine of the Huainan coalfield as proxies to interpret the depositional environment of Taiyuan Formation. Thin-section petrography indicates that the limestones are mainly bioclastic, in-situ and are characterized by matrix-supported cementation. The REE concentrations and elemental patterns in the limestones reflect deposition in a normal marine environment. The REE analyses show the depletion of light rare earth elements, positive La anomalies, and negative Gd anomalies. Moderately negative δCe anomalies indicate that the limestones are most likely formed in an oxidized setting, typically a shallow marine environment. The positive Eu anomaly suggests deposition in a coastal environment with influx of clastics and terrestrial organic matter, thus indicating a more southerly provenance. Results from this study highlight the utility of REE and trace-element analyses of carbonate rocks for the reconstruction of depositional environments.