## 4 Results
### Paleoclimate Indicators  
The content, combination, and ratios of elements in sedimentary strata are closely related to the surrounding physicochemical conditions and can indicate changes in paleoclimate [36]. The distribution of the Chemical Index of Alteration (CIA) values is significantly correlated with climatic conditions [37]. The CIA value is proportional to the degree of chemical weathering. Studies have shown that when the CIA value ranges from 50 to 65, it indicates moderate chemical weathering, typically corresponding to semi-arid or seasonally arid climatic conditions. When the CIA value increases to the range of 65-85, it reflects significantly enhanced chemical weathering, representing warm and humid climatic characteristics [38; 39]. Within the study area, the CIA values range from 60 to 85, indicating a moderate degree of weathering and suggesting that the Enping Depression during the depositional period of the Zhujiang Formation was in a warm and humid sedimentary environment (Figure 7d).  
Figure 6: Astronomical forcing analysis of sedimentary noise models. (**a**) Tuned GR data curve; (**b**) 405 kyr filtered curve (passband: 0.0024656 \(\pm\) 0.0001 cycles/kyr); (**c**) DYNOT sedimentary noise model; (**d**) \(\rho\)1 correlation coefficient model; (**e**) International Chronost stratigraphic Chart.  
The differences in the input of terrigenous elastic materials during different periods are usually caused by climatic changes. Therefore, the intensity of terrigenous elastic input can also reflect the climate to some extent. Elements such as Ti and Al are commonly used to trace the source of sediments [40]. In this study, TiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) were selected as geochemical tracers for the flux of terrigenous elastic materials. In Well EP17, the TiO\({}_{2}\) content ranges from 0.2% to 1.4% (mean 0.677), and the Al\({}_{2}\)O\({}_{3}\) content ranges from 5% to 25% (mean 12.038) (Figure 7e,f). Comparative analysis of the CIA curve and the TiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) content curves shows consistency in their vertical variations. This result indicates that when the intensity of chemical weathering increases (higher CIA values), the input of terrigenous elastic materials also increases (Figure 7d-f). This phenomenon reflects a shift in climatic conditions towards a warmer and more humid environment. Conversely, when the CIA value decreases, the intensity of weathering weakens, and the input of terrigenous elastic materials decreases, indicating a shift towards a relatively dry and hot climate.  
Figure 7: Climatic characteristics and sedimentary responses driven by astronomical orbits. **(a)** Lithologic profile of Well EP17; **(b)** Detrended GR data curve; **(c)** Sand–shale ratio curve; **(d)** Vertical distribution curve of CIA values; **(e)** Vertical distribution curve of Al\({}_{2}\)O\({}_{3}\) content; **(f)** Vertical distribution curve of TiO\({}_{2}\) content; **(g)** 405 kyr filtered curve (passband: 0.0024656 \(\pm\) 0.0001 cycles/kyr), E1–E7 represents 7 eccentricity cycles; **(h)** 20 kyr filtered curve (passband: 0.0024656 \(\pm\) 0.0001 cycles/kyr); **(i)** Average summer insolation at 20\({}^{\circ}\) N [5].