225 / 2025-04-15 14:27:08

Orbitally-paced climate change and biological disturbance during the Middle Permian in South China

Middle Permian,Cyclostratigraphy,Sea level change,carbon cycle,mid-Capitanian extinction

Theme 3: Earth-Life Co-evolution Through Time > Session 3d: Biotic and Environmental Changes during the Late Palaeozoic Ice Age

The Middle Permian is an important period in geological history, which a series of biological, geological, and environmental events occurred, such as the eruption of the Emeishan Large Igneous Province (ELIP), the end of the Late Paleozoic icehouse, and the mid-Capitanian extinction. However, the lack of a high-precision geological age framework hinders the understanding of the interrelationships between those events and the accompanying fluctuations in Earth's climate and environment. In this paper, we conduct cyclostratigraphy analysis on the GR and MS records of marine carbonate rock sequences in Tieqiao section and Rencunping section of the Middle Permian in South China, in order to construct a high-resolution astronomical timescale of the Middle Permian and decipher the response mechanism of sea level and δ¹³C_carb to astronomical cycles. A 6.05 Myr astronomical timescale was constructed, with a duration constraint of 3.4 ± 0.4 Myr for the Capitanian. The amplitude modulation (AM) of the obliquity extracted from the GR series has a period of 1.04 Myr (s₄-s₃ term), and the consistency with the δ¹³C_carb and sedimentary noise models indicates that the AM of the obliquity drove the sea level changes and carbon cycling in the Middle Permian. In the context of greenhouse climate in the Middle Permian, at the maximum AM of the obliquity, the rise of continental aquifers triggered a decrease in sea level, which in turn led to an increase in the input of terrestrial materials carrying more ¹²C in the sedimentary environment, ultimately triggering a positive excursion in carbon isotopes on a million-year scale. At 262.5 Ma, the minimum of AM of the obliquity led to a decrease in the continental aquifer, while the maximum value of eccentricity resulted in higher annual and summer rates of global surface temperature change, glacier reduction, and a combined rise in sea level. At the same time, volcanic eruptions strengthened seawater stratification, and the resulting ocean hypoxia may have been the cause of the mid-Capitanian extinction.