Late Permian Milankovitch Cycles Time Calibrated, Indicate a 22 Hour Day

Time-calibrated Milankovitch cycles for the late Permian

Authors:

1. Huaichun Wu (a,b)
2. Shihong Zhang (a)
3. Linda A. Hinnov (c)
4. Ganqing Jiang (d)
5. Qinglai Feng (e)
6. Haiyan Li (a)
7. Tianshui Yang (a)

Affiliations:

a. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China

b. School of Ocean Sciences, China University of Geosciences, Beijing 100083, China

c. Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA

d. Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154, USA

e. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China

Abstract:

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.