In this study, we report a tuned astronomical time scale for a sedimentary formation in Early Cretaceous – the lower Linze Section located in the Zhangye Basin of the central Hexi Corridor, northwestern China. Based on detailed field investigations, we identified this sediment as the Xiagou Formation, which is widely distributed in the region. A thick, prominent limestone layer crops out in the middle portion of the Linze Section, and can be correlated to a similar limestone layer in the Liupanshan Group, which has been dated via high-resolution magnetostratigraphy. This correlation places an age constraint of around 114 Ma for the top of the underlying strata. A total of 1245 samples were collected from the 474-m-thick lower Linze Section, for magnetic susceptibility measurements and cyclostratigraphic analysis. Spectral and continuous wavelet analyses were applied to the low-frequency magnetic susceptibility series and the percentage frequency-dependent magnetic susceptibility series, as well as to specific subsections exhibiting visible rhythmic bedding. A hierarchy of sedimentary cycles was identified, with wavelengths of 21.5–37.0 m, 7.5–9.5 m, 2.1–4.4 m, and 1.4–1.7 m. The ratios between these lengths correspond well to the ratios between the durations of Earth's orbital long-eccentricity, short-eccentricity, obliquity, and precession cycles. We interpret these sedimentary cycles to reflect the effects of orbital forcing on sedimentary processes. Using band-pass filtering to specifically extract eccentricity cycles, we established a tuned astronomical time scale for the Xiagou Formation in the lower Linze Section, with a total duration of about 6.1 Myr (114.1 Ma to 120.2 Ma). Based on this timescale, the sedimentation rate of the Xiagou Formation is estimated to be in the range of 62–105 m/Myr, with most intervals yielding rates in the 70–80 m/Myr range.
- Milankovitch cycles
- Magnetic susceptibility
- Spectral analysis
- Wavelet analysis
- Lithostratigraphy correlation