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

JET项目是一个大型的、多方面的国际研究项目，有来自13个国家的约50个项目合作伙伴参与，研究地球系统在其历史上的一个关键节点——早侏罗世——的功能，当时它受到独特的构造、岩浆和轨道强迫的影响，现代生物圈的基本方面在二叠纪末和三叠纪末大灭绝之后逐渐建立起来。计划在西威尔士的Mochras钻一个1.9公里深的钻孔，以恢复一个1.3公里长的岩心，代表早侏罗纪时期的27万年。JET项目的总体目标是生成一个独特的早侏罗世记录，允许以迄今为止仅尝试过的新生代（即档案沉积速率= 5 cm/ka或20 a/mm）的规模和分辨率调查地球系统，并将该独特记录与现有数据和综合建模方法结合使用，以产生对早侏罗世地球系统动力学的逐步变化的理解。我们对(a)井下测井数据，(b)在选定岩心桥塞上额外获得的一些物理性质，以及(c)地震反射数据的解释将集中在以下目标上：•沉积物的岩性特征，包括不整合面和岩性边界的检测，•确定该地区的古气候和古环境历史，•沉积物相和沉积旋回的描述；•整合和校准地震反射剖面和钻孔周围的3D建模，•将沉积物岩心测井属性校准为钻孔特征的“真实深度”，•以最具成本效益的方式最大限度地恢复地层。

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.