Site construction for the Early Jurassic Earth System and Timescale (JET) project begins at Prees, Cheshire Basin, UK. The principal aim for Prees is to core an expanded 850 m thick Late Triassic to Early Jurassic mudstone succession for integrated astrochronology, biostratgraphy, chemostratigraphy and magnetostratigraphy. The new record will complement ongoing studies of the historic Llanbedr (Mochras Farm) borehole, UK, and the project will lead to a greatly enhanced understanding of major environmental changes and Earth System transitions that took place over this time interval.