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7118204 
Journal Article 
Time-calibrated Milankovitch cycles for the late Permian 
Wu, H; Zhang, S; Hinnov, LA; Jiang, G; Feng, Q; Li, H; Yang, T; , 
2013 
1 
Nature Communications
EISSN: 2041-1723 
NATURE PUBLISHING GROUP 
LONDON 
24030138 
WOS:000325533700049 
An important innovation in the geosciences is the astronomical time scale. The astronomical time scale is based on the Milankovitch-forced stratigraphy that has been calibrated to astronomical models of paleoclimate forcing; it is defined for much of Cenozoic-Mesozoic. For the Palaeozoic era, however, astronomical forcing has not been widely explored because of lack of high-precision geochronology or astronomical modelling. Here we report Milankovitch cycles from late Permian (Lopingian) strata at Meishan and Shangsi, South China, time calibrated by recent high-precision U-Pb dating. The evidence extends empirical knowledge of Earth's astronomical parameters before 250 million years ago. Observed obliquity and precession terms support a 22-h length-of-day. The reconstructed astronomical time scale indicates a 7.793-million year duration for the Lopingian epoch, when strong 405-kyr cycles constrain astronomical modelling. This is the first significant advance in defining the Palaeozoic astronomical time scale, anchored to absolute time, bridging the Palaeozoic-Mesozoic transition.