Fig. 1. Schematic diagram of the position of the sections (a) and the photos of sections [(b): Bole; (c): Jinchuan; (d): Xuwen]

Fig. 2. First derivative of DRS: representative samples of Bole, Jinchuan and Xuwen section

Fig. 3. The variation curves of Characteristic peak height of DRS first derivative of Gt, Hm and Gt/Hm at Bole, Jinchuan and Xuwen section

Fig. 4. The variation curves of chroma of Bole, Xuwen and Jinchuan section with depth

Fig. 5. Scatter plots between DRS parameters and color parameters
(a)—(c): Bole; (d)—(f): Jinchuan; (g)—(i): Xuwen

Fig. 6. Correlation scatter plots of DRS parameters (Gt, Hm) and color parameters (b^*, a^*)

Fig. 7. Scatter plots of average annual temperature, average annual precipitation and the mean of a^* and Gt/Hm