Integrated Understanding of the Early Jurassic Earth System and Timescale (JET)

我们提出了一个关于地球系统在其历史上的关键时刻--侏罗纪早期--功能的大规模、多方面的国际研究方案。当时，地球受到独特的构造、岩浆和太阳系轨道的强迫，现代生物圈的基本方面在二叠纪末和三叠纪末大灭绝后逐渐形成。超大陆盘古大陆的解体伴随着航道的建立、大型火成岩省的就位和生物地球化学扰动的发生，包括在海洋变得缺氧的同时，在过去200年里碳循环的最大幅度扰动。持续的环境扰动在三叠纪末期大规模灭绝的复苏、现代浮游植物的兴起、阻止原有海洋动物群的恢复以及催化“中生代海洋革命”方面发挥了作用。然而，现有的知识是基于分散和不连续的地层学数据集，这意味着相关误差(即来自不同位置的数据集之间的不匹配)混淆了推断时间趋势和因果关系的尝试，使我们无法对早侏罗世地球系统动力学进行基于定量过程的了解。这一建议旨在通过观测和建模相结合的方法来解决这一根本知识差距，该方法基于准确地固定在稳健的地质时间尺度上的地层学‘主记录’，并与准确的古气候、古海洋和生物地球化学模型框架相结合。该项目已经从国际大陆钻探计划获得了150万美元，用于在西威尔士莫克拉斯钻一个深井，以恢复一个1.3公里长的新岩芯，这是一个异常扩大和完整的早期侏罗纪地球历史的沉积档案。这个核心将允许以迄今为止仅在过去6500万年来尝试的比例尺和分辨率(即档案沉积速率=5厘米/Ky或20年/毫米)来调查地球系统。我们将利用新记录与现有数据和综合模拟方法，对侏罗纪时间尺度和地球系统动力学的理解产生阶段性变化。除了时间尺度精度的数量级改进外，我们还将：区分天文强迫和非天文强迫古环境变化；使用大气-海洋耦合环流模式来了解对气候系统和海洋环流制度的控制；了解天文强迫环境参数在20KYR至8MyR时间尺度上的周期变化之间的关系历史，并与与接收到的太阳能有关的强迫的具体方面联系起来；使用估计的环境变化速率和时间来测试假定的强迫机制，特别是来自已知地质事件的机制；约束控制碳循环扰动事件的启动、演化和恢复的触发和反馈序列；以及使用地球系统模型来测试对起源的“冰屋”条件的假设。来自13个国家的36个项目合作伙伴大大加强和扩展了以英国为基础的研究。

We propose a large-scale, multi-faceted, international programme of research on the functioning of the Earth system at a key juncture in its history - the Early Jurassic. At that time the planet was subject to distinctive tectonic, magmatic, and solar system orbital forcing, and fundamental aspects of the modern biosphere were becoming established in the aftermath of the end-Permian and end-Triassic mass extinctions. Breakup of the supercontinent Pangaea was accompanied by creation of seaways, emplacement of large igneous provinces, and occurrence of biogeochemical disturbances, including the largest magnitude perturbation of the carbon-cycle in the last 200 Myr, at the same time as oceans became oxygen deficient. Continued environmental perturbation played a role in the recovery from the end-Triassic mass extinction, in the rise of modern phytoplankton, in preventing recovery of the pre-existing marine fauna, and in catalysing a 'Mesozoic Marine Revolution'. However, existing knowledge is based on scattered and discontinuous stratigraphic datasets, meaning that correlation errors (i.e. mismatch between datasets from different locations) confound attempts to infer temporal trends and causal relationships, leaving us without a quantitative process-based understanding of Early Jurassic Earth system dynamics.This proposal aims to address this fundamental gap in knowledge via a combined observational and modelling approach, based on a stratigraphic 'master record' accurately pinned to a robust geological timescale, integrated with an accurate palaeoclimatic, palaeoceanographic and biogeochemical modelling framework. The project has already received $1.5M from the International Continental Drilling Programme towards drilling a deep borehole at Mochras, West Wales, to recover a new 1.3-km-long core, representing an exceptionally expanded and complete 27 My sedimentary archive of Early Jurassic Earth history. This core will allow investigation of the Earth system at a scale and resolution hitherto only attempted for the last 65 million years (i.e. archive sedimentation rate = 5 cm/ky or 20 y/mm). We will use the new record together with existing data and an integrative modelling approach to produce a step-change in understanding of Jurassic time scale and Earth system dynamics.In addition to order of magnitude improvements in timescale precision, we will: distinguish astronomically forced from non-astronomically forced changes in the palaeoenvironment; use coupled atmosphere-ocean general circulation models to understand controls on the climate system and ocean circulation regime; understand the history of relationships between astronomically forced cyclic variation in environmental parameters at timescales ranging from 20 kyr to 8 Myr, and link to specific aspects of forcing relating to solar energy received; use estimated rates and timing of environmental change to test postulated forcing mechanisms, especially from known geological events; constrain the sequence of triggers and feedbacks that control the initiation, evolution, and recovery from the carbon cycle perturbation events, and; use Earth system models to test hypotheses for the origins 'icehouse' conditions. Thirty six project partners from 13 countries substantially augment and extend the UK-based research.