Time-calibrated Milankovitch cycles for the late Permian

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.

High-precision timeline for Earth’s most severe extinction

“…This estimate is three times shorter than reported by Shen et al (3) (Figs. S1 and S2) and is more consistent with the recent estimate derived from astrochronology of 83 ka (20).…”

“…Published estimates of the extinction interval based on radioisotopic dates range from ∼1.5 Mya to approximately <200 ± 100 ka, whereas astrochronological interpretations range from ∼700 ka to as little as ∼10 ka (3,14,15,18,19). Most recently, Wu et al (20) used Milankovitch cyclicity and previously published geochronology to constrain the maximum extinction interval at Meishan to 83 ka. Published geochronology is not sufficiently precise to test this estimate.…”

“…To better understand the relationship between environmental perturbation and biotic response, accurate and precise age models that integrate geochronology, paleontology, and geochemistry must be developed (8,11,16,17). Recognition of astronomically forced sedimentary cycles (Milankovitch cycles) in late Permian and Triassic sedimentary rocks tuned with available geochronology have been used to refine existing age models of the biotic crisis (18)(19)(20). Published estimates of the extinction interval based on radioisotopic dates range from ∼1.5 Mya to approximately <200 ± 100 ka, whereas astrochronological interpretations range from ∼700 ka to as little as ∼10 ka (3,14,15,18,19).…”

The astronomical calibration of the Givetian (Middle Devonian) timescale (Dinant Synclinorium, Belgium)

“…Therefore, even in the Palaeozoic, the stable periodicity of the 405 kyr cycle can be used as a geochronometer (e.g. Hinnov et al 2013;Wu et al 2013). Indeed, a cyclostratigraphy that is based on this astronomical-forcing component reliably estimates the duration of events and stratigraphic intervals.…”

Stratigraphic continuity and fragmentary sedimentation: the success of cyclostratigraphy as part of integrated stratigraphy

“…A prime example comes from the upper Permian marine sections of Meishan, the stratotype for the Changhsingian Stage, and Shangsi in China (Wu et al 2013b). These sections were used to estimate an astronomical duration of 7.793 myr for the Lopingian Epoch.…”