15 Myr high resolution χin in and GRS records of Early Devonian carbonates are presented.
Duration for the Lochkovian stage is 7.7±2.8 Myr and for the Pragian 1.7±0.6 Myr.
Durations are considerably more precise than in current time scales.
405 kyr and 100 kyr cycles are modulated by long term cycles of 1.0 and 2.4 Myr.