## 4 Results
### Sedimentary Environmental Characteristics  
The change in the sedimentary water environment usually elicits a specific geochemical response in sedimentary rocks (shale, sandstone, limestone, mudstone, etc.). Therefore, the parameters of trace elements and rare earth elements in rocks can better reflect the original geochemical information and paleoenvironmental characteristics preserved by source rocks [35; 36]. The enrichment and accumulation of V, Ni, Cu, Zn, and other elements in sediments are controlled by the redox conditions of the sedimentary environment. These elements are typically enriched under reducing conditions [37; 38].  
The V/(V + Ni) ratio can indicate the stratification and redox conditions of the water [37]. When V/(V + Ni) is less than 0.46, it reflects an oxygen-rich oxidation environment; when it is between 0.46 and 0.57, it reflects an oxygen-poor weak reduction environment; when it is between 0.57 and 0.83, it reflects an anoxic reduction environment; when it is between 0.83 and 1, it reflects a static sea environment [37]. The V/(V + Ni) ratio of the Permian Taiyuan Formation shale is 0.76-0.87, with an average of 0.82 (Table 2). This value is significantly higher than the threshold of 0.57, indicating that the ancient water existed in an anoxic static sea environment during the sedimentary period of the Taiyuan Formation. The Cu/Zn ratio can reflect the redox conditions of ancient water. Cu/Zn < 0.21 is an anoxic environment, 0.21 < Cu/Zn < 0.63 is an oxygen-poor environment, and Cu/Zn < 0.63 is an oxygen-rich environment [39]. The Cu/Zn ratio of the Taiyuan Formation shale ranges from 0.16 to 0.23, with an average of 0.22 (Table 2). This indicates that the ancient water existed in an oxygen-poor and anoxic sedimentary environment during the deposition period of the Taiyuan Formation. The Ce anomaly is also a reliable and effective  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample ID**} & \multirow{2}{*}{**Depth (m)**} & **TOC** & **Ro** & **Sapropel-Inite** & **Exinite** & **Vitrinite** & **Inertinite** & **OI** \\  & & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **TI** & **Type** \\ \hline Z-1 & 2845.0 & 2.61 & 3.19 & 84 & 6 & 6 & 4 & 78.5 & II1 \\ Z-4 & 2861.5 & 2.50 & 3.24 & 20 & 10 & 42 & 28 & \(-34.5\) & III \\ Z-6 & 2868.8 & 2.27 & 3.19 & 28 & 12 & 40 & 20 & \(-16.0\) & III \\ Z-7 & 2876.4 & 3.88 & 3.11 & 34 & 14 & 36 & 16 & \(-2.0\) & III \\ Z-8 & 2880.0 & 3.52 & 3.20 & 50 & 16 & 24 & 10 & 30.0 & II\({}_{2}\) \\ Z-11 & 2886.6 & 1.79 & 3.17 & 82 & 8 & 8 & 2 & 78.0 & II\({}_{1}\) \\ Z-14 & 2897.1 & 1.32 & 3.50 & 25 & 8 & 44 & 23 & \(-27.0\) & III \\ Z-17 & 2905.7 & 1.25 & 3.33 & 84 & 2 & 8 & 6 & 73.0 & II\({}_{1}\) \\ Z-20 & 2910.6 & 2.24 & 3.18 & 92 & 4 & 2 & 2 & 90.5 & I \\ \hline \hline \end{tabular}
\end{table}
Table 1: Organic geochemical characteristics and hydrocarbon generative potential of shale samples from the Taiyuan Formation in the SNCB.  
Figure 2: The TOC distribution of Taiyuan Formation shale in the SNCB.  
method for determining redox conditions [40]. Due to the extremely low content of Ce, the Ce anomaly can generally be replaced by the ratio of Ce/La. The Ce/La ratio less than 1.5 indicates an oxygen-rich environment, the ratio between 1.5 and 1.8 indicates an oxygen-poor environment, and the ratio greater than 1.8 indicates an anoxic environment [40]. The Ce/La ratio of the Taiyuan Formation shale ranges from 1.57 to 2.00, with an average of 1.81 (Table 2), indicating that the ancient water existed in poor oxygen and anaerobic sedimentary environment during the sedimentation period of the Taiyuan Formation. In summary, the geochemical parameters of the V/(V + Ni) ratio, Cu/Zn ratio, and Ce/La ratio all indicate that the sedimentary period of the Permian Taiyuan Formation in the SNCB was poor oxygen and anaerobic sedimentary environment of static water.