Astronomical cycles of Middle Permian Maokou Formation in South China and their implications for sequence stratigraphy and paleoclimate

- A 405 kyr-tuned ATS is established for Middle Permian in Dukou, South China.
- The durations of the conodont zones of Wordian and Capitanian stages are estimated.
- Middle Permian obliquity modulation cycles have ~1 myr periodicity.
- Obliquity modulation cycles controlled Middle Permian third-order eustatic sequences.

High-resolution (930 samples) magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) analyses were conducted on the ~ 49 m thick Middle Permian Maokou Formation at Dukou, South China. Spectral analysis of covariant MS and ARM series reveal Milankovitch cycles with eccentricity, obliquity, and precession. A 5.7 myr floating 405 kyr eccentricity cycle-calibrated astronomical time scale was constructed and used as a geochronometer for estimating the durations of the conodont zones. The results indicate that the durations of the Jinogondolella postserrata, J. altudaensis, J. prexuanhanensis, and J. xuanhanensis conodont zones were 490 kyr, 560 kyr, 820 kyr, and 750 kyr, respectively. The 405 kyr-calibrated MS and ARM series also show prominent ~ 1 myr cyclicity, which may correspond to the secular frequencies of Earth and Mars, s4-s3, in the Middle Permian. The early Capitanian time interval was synchronous with the Kamura cooling event, and the accentuated obliquity cycling may signal ice-sheet expansion. The modulations of the obliquity have a close relationship with third-order eustatic sequences of the Wordian and Capitanian stages, suggesting a glacioeustatic origin during the Middle Permian.