Orbital forcing of climate 1.4 billion years ago

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-03, Vol.112 (12), p.E1406-E1413
• Main Authors: Zhang, Shuichang, Wang, Xiaomei, Hammarlund, Emma U., Wang, Huajian, Costa, M. Mafalda, Bjerrum, Christian J., Connelly, James N., Zhang, Baomin, Bian, Lizeng, Canfield, Donald E.
• Format: Article
• Language: English
• Subjects: Climate change; Geochemistry; Physical Sciences; PNAS Plus; Sedimentation & deposition; Sediments
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1502239112

Fluctuating climate is a hallmark of Earth. As one transcends deep into Earth time, however, both the evidence for and the causes of climate change become difficult to establish. We report geochemical and sedimentological evidence for repeated, short-term climate fluctuations from the exceptionally well-preserved ∼1.4-billion-year-old Xiamaling Formation of the North China Craton. We observe two patterns of climate fluctuations: On long time scales, over what amounts to tens of millions of years, sediments of the Xiamaling Formation record changes in geochemistry consistent with long-term changes in the location of the Xiamaling relative to the position of the Intertropical Convergence Zone. On shorter time scales, and within a precisely calibrated stratigraphic framework, cyclicity in sediment geochemical dynamics is consistent with orbital control. In particular, sediment geochemical fluctuations reflect what appear to be orbitally forced changes in wind patterns and ocean circulation as they influenced rates of organic carbon flux, trace metal accumulation, and the source of detrital particles to the sediment. Significance There is a wealth of evidence pointing to dramatic short-term climate change on Earth over the last few million years. Much of this climate change is driven by variations of Earth’s orbit around the Sun with characteristic frequencies known as Milankovitch cycles. Robust evidence for orbitally driven climate change, however, becomes rare as one descends deep into Earth time. We studied an exceptional record of climate change as recorded in 1.4-billion-year-old marine sediments from North China. This record documents regular changes in subtropical/tropical Hadley Cell dynamics. These changes in dynamics controlled wind strength, rainfall, and ocean circulation, translated into cyclic variations in sediment geochemistry, much like the orbital control on climate today and in the recent past.