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The astronomical theory and its application to sediment cyclostratigraphy have been widely studied over the past thirty years.Especially during the past decade,these have been successfully applied for a continuous high-resolution calibration of portions of the geologic time scale.The method of astronomical tuning enhances the traditional geological dating methods,such as paleontology,paleomagnetism and radioisotope dating.In The Geologic Time Scale 2012(GTS2012),most of the Cenozoic Era was directly calibrated to the absolute astronomical time scale(ATS);however,only a few intervals of the Mesozoic-Paleozoic were scaled by cyclostratigraphy in discontinuous floating segments.Since then,other cyclostratigraphy studies have been published using the most stable 405-kyr long-eccentricity cycle to calibrate portions of the Mesozoic geological time scale.Other than some gaps within the mid-Triassic and Middle Jurassic,it is possible to compile a nearly complete ATS status for the Mesozoic.This chapter compiles and recalibrates an extensive suite of selected paleoclimate proxies series and applies a tuning to the master astronomical scale based on the stable 405-kyr long-eccentricity period.This enables the synthesis of a nearly complete Mesozoic ATS to the base of the Triassic.