Temporal calibration and quantification of Early Trias-sic climatic disturbances through high-precision U-Pb zircon dating and an improved chemical abrasion procedure

Resolving the timing of climate disturbances and carbon cycle fluctuations in the geological past is a pre-requisite to understand the nature of triggers of global change and the timing of environmental and biological feedback. This thesis aims to improve and implement methods to build accurate timeframes, in order to decipher the temporal relationships between triggers and feedbacks of climate disturbances and their environmental impact. This is realized by combining high-precision U-Pb geochronology (CA-ID-TIMS), with the geological, biological and chemical record integrated into a Bayesian age-depth model. Moreover, the conditions of the chemical pre-treatment (“chemical abrasion”) of the zircon ID-TIMS technique are optimized to mitigate the age bias due to loss of radiogenic lead from the crystal structure and to improve the accuracy of the method. The improved protocol is applied to single zircon of volcanic ash beds interspersed with Early Triassic marine sediments (Nanpanjing basin, South China).