Physical properties, in situ structure and cyclicity of 1300 m Early Jurassic mudstones from geophysical logs in the ICDP Mochras borehole, West Wales

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The JET project is a large-scale, multi-faceted, international programme of research with about 50 project partners from 13 countries on the functioning of the Earth system at a key juncture in its history – the Early Jurassic – when it was subject to distinctive tectonic, magmatic, and orbital forcing, and fundamental aspects of the modern biosphere were becoming established in the aftermath of the end Permian and end Triassic mass extinctions. It is planned drilling a 1.9-km-deep borehole at Mochras, West Wales, to recover a 1.3-km-long core representing 27 Ma of Early Jurassic time. The overarching goal of the JET project is to generate a unique Early Jurassic record allowing investigation of the Earth system at a scale and resolution hitherto only attempted for the Cenozoic (i.e. archive sedimentation rate = 5 cm/ka or 20 a/mm), and to use that unique record together with existing data and an integrative modelling approach to produce a step-change in understanding of Early Jurassic Earth system dynamics.Our interpretation of (a) downhole logging data, (b) some additionally acquired physical properties on selected core plugs and (c) seismic reflection data will focus on the following objectives:• the characterisation of the lithology of the sediments including the detection of unconformities and lithological boundaries,• the determination of the paleoclimatic and paleoenvironmental history of this area,• the description of sediment facies and sedimentary cycles; compaction,• the improvement in knowledge about neotectonics and contemporary tectonics,• the integration and calibration of seismic reflection profiles and 3D modelling around the boreholes,• the calibration of sediment core logging properties to the ‘true depths’ of features in the borehole,• to maximize stratigraphic recovery in the most cost-effective manner.