High-precision calibration of the Early to Middle Triassic timescale with U-Pb on volcanic zircon

We use high-precision U/Pb geochronology to reconstruct the timing of the disturbance of environment and life. The mineral zircon (ZrSiO4) is an ubiquitous constituent of volcanic ash beds that are interbedded with marine sedimentary rocks. Dating the zircon from these ash beds at the highest level of precision and accuracy will provide us with a precise date for the deposition of the ash, and therefore for the age of the overlying sedimentary layer. The analytical work is done using chemical abrasion, isotope dilution, thermal ionisation mass spectrometry techniques (CA-ID-TIMS). The use of Earthtime tracer and calibration solutions assures opimal precision and accuracy at better than 0.1% for a 206Pb/238U date.

The ash beds comes from Triassic deposits in the Nanpanjiang basin of south China which records sedimentation from the late Proterozoic into the late Triassic. The basin consists of deep water and carbonate platform deposits and provides an unparalleled frequency of Ash beds compared to other Triassic deposits worldwide. This allows for a tight temporal control on information such as diversity dynamics of the palaeontological record and fluctuations of the carbon cycle.