INTERMITTENT OBLIQUITY-FORCED CLIMATE DURING THE EARLY TRIASSIC
In this study, two equatorial cyclostratigraphic successions, i.e. Chaohu and Daxiakou marine sections from South China are evaluated for astronomical forcing of Early Triassic climate. Astronomical tuning of the gamma-ray series provides a high-resolution timescale for the Early Triassic. A measure for obliquity power/total power is developed for the tuned time series and applied to highlight long-term amplitude modulations of the obliquity variation. In both Chinese records, unexpectedly, enhanced obliquity cycling occurs over multiple prolonged intervals, characterized by a periodicity of 32.8-kyr and strong 1.2-myr period modulations, suggesting a 22-hour length-of-day and representing evidence for 1.2-myr interaction between the orbits of Earth and Mars. These enhanced obliquity intervals coincide with global sea level falls and other evidence for cooling linked to recurrent ocean oxidation/dysoxia and biotic recovery. This evidence suggests that long-term astronomical forcing was involved in the repeated environmental and biotic upheavals that took place during the Early Triassic.