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

我们提出了一个大规模的，多方面的，对地球系统在其历史上的一个关键时刻-早侏罗世的运作研究的国际计划。当时，地球受到独特的构造、岩浆和太阳系轨道作用力的影响，现代生物圈的基本方面在二叠纪末和三叠纪末的大规模灭绝之后逐渐建立起来。超大陆泛古陆的解体伴随着海道的形成、大火成岩省的就位和地球化学扰动的发生，包括过去2亿年来最大规模的碳循环扰动，与此同时，海洋变得缺氧。持续的环境扰动在三叠纪末大规模灭绝的恢复中发挥了作用，现代浮游植物的崛起，阻止了先前存在的海洋动物群的恢复，并催化了“中生代海洋革命”。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，使我们无法对早侏罗世地球系统动力学进行基于定量过程的理解。该提案旨在通过结合观测和建模方法来解决这一知识上的根本差距，基于精确地固定到一个强大的地质时标的地层“主记录”，结合精确的古气候，古海洋和地球化学建模框架。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Mochras钻探一个深钻孔，以恢复一个新的1.3公里长的岩心，代表了一个特别扩大和完整的27 My早期侏罗纪地球历史的沉积档案。该岩心将允许以迄今为止仅在过去6500万年中尝试过的尺度和分辨率（即档案沉积速率= 5 cm/ky或20 y/mm）对地球系统进行调查。我们将利用新记录、现有数据和综合建模方法，逐步改变对侏罗纪时间尺度和地球系统动力学的理解。除了时间尺度精度的数量级改进外，我们将：区分古环境中天文强迫和非天文强迫的变化;使用大气-海洋环流耦合模式，了解对气候系统和海洋环流状况的控制;了解天文强迫环境参数周期性变化之间关系的历史，时间尺度从20 kyr到8 Myr，并与与接收到的太阳能有关的强迫的具体方面联系起来;使用环境变化的估计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强迫机制;限制控制碳循环扰动事件的启动、演变和恢复的触发和反馈的顺序;使用地球系统模型来检验起源的“冰库”条件的假设。来自13个国家的36个项目合作伙伴大大增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