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

我们提出一项大规模的、多方面的、国际性的研究计划，研究地球系统在其历史上的一个关键时刻——早侏罗世的功能。在那个时候，地球受到独特的构造、岩浆和太阳系轨道强迫的影响，现代生物圈的基本方面在二叠纪末和三叠纪末的大灭绝之后逐渐建立起来。泛大陆的分裂伴随着海道的形成，大型火成岩省的就位，以及生物地球化学扰动的发生，包括最近200万年碳循环的最大扰动，与此同时海洋变得缺氧。持续的环境扰动在从三叠纪末大灭绝中恢复，在现代浮游植物的兴起，在阻止原有海洋动物的恢复，以及催化“中生代海洋革命”中发挥了作用。然而，现有的知识是基于分散和不连续的地层数据集，这意味着相关误差（即来自不同地点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，使我们无法定量地理解早侏罗世地球系统动力学。该提案旨在通过一种结合观测和建模的方法来解决这一基本的知识差距，该方法基于精确地固定在一个强大的地质时间尺度上的地层“主记录”，结合精确的古气候、古海洋学和生物地球化学建模框架。该项目已经从国际大陆钻探计划获得了150万美元，用于在西威尔士的莫克拉斯钻一个深孔，以恢复一个新的1.3公里长的岩心，代表了一个异常扩展和完整的早侏罗纪地球历史沉积档案。这个地核将允许对地球系统进行规模和分辨率的调查，迄今为止只有在过去的6500万年中才尝试过（即存档沉积速率= 5厘米/天或20毫米/毫米）。我们将利用新记录与现有数据和综合建模方法，在理解侏罗纪时间尺度和地球系统动力学方面产生一个逐步变化。除了时间尺度精度的数量级提高外，我们还将：区分古环境的天文强迫和非天文强迫变化；使用耦合的大气-海洋环流模式来了解气候系统和海洋环流状态的控制；了解在20kyr至8myr时间尺度上环境参数的天文强迫周期变化之间的关系历史，并将其与所接收的太阳能量有关的强迫的具体方面联系起来；利用估计的环境变化速率和时间来检验假定的强迫机制，特别是来自已知地质事件的强迫机制；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；使用地球系统模型来验证起源“冰窖”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英国的研究。

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.