THE GREAT JURASSIC ARIDIFICATION: TRUE POLAR WANDER INDUCED CLIMATE CHANGE COUPLED TO THE DEMISE OF THE YANLIAO BIOTA AND RISE OF THE JEHOL BIOTA

Tectonically-linked drivers of climate change are well-documented during the Cenozoic in Asia. The rise of the Himalayas accentuated the monsoons in India, split the jet stream and led to the late Cenozoic desertification of the Asian interior. A similarly striking change occurred during the Middle to Late Jurassic as much of East Asia transitioned from an extremely wet to drastically arid climate. The timing, scope and especially the mechanism for this aridification are; however, contentious. The drastic environmental change that occurred during the Middle to Late Jurassic witnessed much of East Asia transitioning from a wet seasonal to extremely arid climate. In this study, we report paleomagnetic data and ages from Jurassic volcanic rocks in North China and, for the first time, reveal a large scale southward displacement of ~25° for the Eastern Asian Blocks (EAB) between 174 ± 6 and 157 ± 4 Ma followed by a smaller magntitude northward shift during the early Cretaceous. We argue that the rapid motion documented by our paleomagnetic studies resulted from a massive true polar wander (TPW) rotation that displaced the EAB from the northern hemisphere humid temperate belt into the sub-tropical/tropical arid zone during the late Jurassic. TPW is the motion of the lithosphere and mantle with respect to the Earth’s spin axis that transfers mass excesses towards the equator leading to the redistribution of solar insolation and regional environmental changes. Recent compilations of regional or global Apparent Polar Wander Paths (APWPs) suggest a rapid shift during the Jurassic that likely represents a large-scale episode of TPW The resultant lithospheric motion coincides with the remarkable climate change that occurred over 10,000,000 square kilometers in East Asia between ~165 and 155 Ma. We call this transition the “Great Jurassic Aridification” and argue that TPW induced climatic shifts were also responsible for the large-scale demise of the Yanliao biota. It appears that an early Cretaceous counterclockwise TPW rotation took place and returned much of the region into the humid temperate belt leading to favorable conditions for the rise of the Jehol biota.