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• We develop a 10.8-Myr astronomical time scale for the Early Cambrian Stage 2-Stage 3. • ∼1.5-Myr obliquity cycles significantly affect sea-level oscillations in the greenhouse period. • New chaotic resonance of Mars-Earth system may occur in the Early Cambrian Period. • Constraints on the Earth-Moon system evolution in deep time are refined. The early Cambrian was a critical period of Earth history, marked by explosive diversification of metazoans and several profound changes in Earth's surface environments and global climate. A valid temporal framework for the early Cambrian Period and across the major bio-events is poorly constrained, and the key underlying forcings of million-year (Myr) scale sea-level variations in a greenhouse lacking polar ice sheets are still disputed. Here, the high-resolution gamma-ray logs (GR) and Fe/Al records are utilized to conduct cyclostratigraphic analysis of the early Cambrian Stage 2-Stage 3 Qiongzhusi Formation of the Well A borehole in South China. A ∼10.8 Myr-long high-resolution astronomical time scale across Stage 2-Stage 3 is developed by astronomical tuning of gamma-ray logs and Fe/Al series to the stable 405-kyr long-eccentricity cycles. The Myr-scale sea-level fluctuations in the early Cambrian greenhouse are reconstructed through the sedimentary noise modeling of the 405-tuned GR series and agree with sequence stratigraphic interpretations, lithofacies stacking patterns, and depositional environment changes. The antiphase correlation of filtered ∼1.5 Myr cycles of sedimentary noise curves with the ∼1.5 Myr obliquity modulation cycles demonstrates that the variations in land-ocean water exchange linked to changes in poleward moisture and heat transport dominated by ∼1.5 Myr obliquity modulation cycles may be a primary driver for eustasy during non-glacial early Cambrian period. A new resonance state in the early Cambrian Stage 2-Stage 3, manifested by ∼1.5 Myr eccentricity: ∼1.5 Myr obliquity, could be mainly associated with the Earth-Mars secular resonance and constrain the chaotic evolution of the Solar System in deep time. Two independent approaches are employed to reconstruct the history of Earth-Moon system characteristics, including the precession constant, the Earth-Moon distance and the day length. Our results enhance knowledge of the connection of Myr-scale sea-level variations to astronomically induced climate change under greenhouse climate and provide new empirical constraints on the chaotic motion of the Solar System and the evolution of the Earth-Moon System in deep time. [ABSTRACT FROM AUTHOR]

The astrochronology for the Early Triassic has been constructed from well-preserved marine successions; however, astronomical analyses of terrestrial strata have continued to be rare and problematic. Physical logs (natural gamma ray logging data) from two wells in the Junggar Basin, northwestern China cover the entire Lower Triassic terrestrial Baikouquan Formation and have been shown to be a powerful tool in cycle analysis. Therefore, these logs offer an excellent opportunity to detect astronomically forced sedimentation in a terrestrial setting from mid to high latitudes. Power spectral analysis revealed that the sedimentary cycles had wavelengths of 31.3–35.9 m, 8.4–10.0 m, 4.0–4.6 m, and ~4.0 m. These are interpreted to correspond to the orbital eccentricity cycles of 405 kyr and ~100 kyr and to the obliquity cycles of ~51 kyr and ~34 kyr, respectively. We, thus, established an astronomical time scale for the studied interval, assuming that the 31.3–35.9 m cycles represent the 405 kyr eccentricity cycles. This astrochronology indicated that the duration of the Baikouquan Formation was 2.0 ± 0.1 Myr. Statistical evaluations of optimal sediment accumulation rates using the correlation coefficient approach showed that the rates of the investigated successions were approximately 6.0–12.0 cm/kyr. Orbitally controlled climate change was the major dynamic mechanism for the formation of Early Triassic fan delta successions in the Junggar Basin. • Astronomical forcing controlled the Early Triassic fan delta deposition • Astrochronology indicates a 2.0 ± 0.1 Myr duration of the Baikouquan Fm. • Mesozoic fan-delta succession responds to orbitally controlled climate change. [ABSTRACT FROM AUTHOR]