Collaborative Research: A Proposal for the Cosmic-Ray prOduced NUclide Systematics on Earth (CRONUS-Earth) Project

摘要：1986年首次证明了地表暴露测年和其他地球科学应用的地球原位宇宙核素（TCN）方法。在随后的17年中，这些方法已发展成为现代地球科学的许多领域，包括古气候学、地貌学、构造学、水文学和火山学等，用途广泛和不可或缺的工具。已被证明广泛适用的TCN有3H、10Be、14C、21Ne、26Al和36Cl。方法的进步促进了这一快速发展，包括取样策略、样品制备程序和宇宙核素分析（通过加速器质谱法和惰性气体质谱法）的改进。为了保持在地球科学的前沿，TCN方法的准确性必须得到显著提高。然而，该领域的从业者一致认为，进一步的发展反而走向了僵局。这种限制不是由于方法学上的考虑，而是由于对基本物理过程的不完全理解，以及不同研究者和方法之间缺乏严格的可比性。宇宙成因核素产量的全球分布取决于许多相互关联的因素，这些因素必须同时得到控制，以便得出准确定义所有地点和地质时期的产量的方程和参数。这项任务远远超出了任何单个调查员的能力。为了实现这一必要的下一步，CRONUS-Earth计划被提出。该项目有以下目标：(i)为不同研究人员对不同核素的测量之间的相互比较建立一个严格的基础；（ii）在宇宙射线物理学和宇宙射线产生的TCN的系统学之间提供一个牢固的联系；（iii）为计算TCN的产生提供普遍接受的公式和参数。最终目标是将所有TCN方法的精密度和准确度从目前的~10%到20%提高到5%的水平。这个项目被设想为一项国际合作的努力。CRONUS-Earth由六个主要部分组成：(i)方法上的相互比较，包括样品制备和分析测量。㈡宇宙射线通量的时空分布，通过“挖掘”现有中子监测仪数据集，模拟中子监测仪的响应，以及测量饱和的原位14C高度/纬度剖面图。（三）为3He、21Ne、10Be、32P和36Cl的生产设置人工指标，将当代宇宙射线通量与生产率和比例因子联系起来。（iv）使用实验室中子束测量生产截面。进行数值模拟工作，以综合观测资料并计算过去地磁和古气候变化对宇宙成因核素产生的影响。根据世界各地独立定年的地表对核素产生率进行地质校准。这些地点将根据质量分为主要校准地点和次要或“验证”地点，这些地点将用于测试整体生产率模型。这六个组成部分构成了一种协同和协调的方法，以解决显然超出个人和小型研究团队范围的问题。我们建议采用联合体的方式来管理项目，包括多名调查人员，每年召开会议来监督进展，汇编数据，并与社区交流，快速电子分发结果，并通过一个负责向社区传播结果的项目办公室整合最终产品。相关的CRONUS-Europe提案已提交给欧盟，并将与CRONUS-Earth密切协调。CRONUS-Earth项目将通过建立一个改进的、定量的、基于物理的、对TCN产生和积累的理解来解决美国国家科学基金会的智力价值审查标准，该标准可用于解决地球科学中的各种问题。该项目将通过提供公式、参数和计算机代码来解决更广泛的影响标准，这些公式、参数和计算机代码将构成一个智能基础设施，使TCN方法在地球科学中得到更一致、更准确和更广泛的应用。此外，该项目将为今后采取更正式和更有组织的办法促进TCN方法的一致性提供基础，例如设立委员会为参数提供建议值。最后，它将包括一个直接让本科生，特别是少数民族学生参与与CRONUS有关的地球科学方面的研究的组成部分。

ABSTRACTTerrestrial- in situ- cosmogenic nuclide (TCN) methods for surface exposure dating and otherearth-science applications were first demonstrated in 1986. During the subsequent 17 years these methods have developed into versatile and indispensable tools in many fields of modern Earth Sciences, including paleoclimatology, geomorphology, tectonics, hydrology, and volcanology. The TCN that have been demonstrated to be widely applicable are 3H, 10Be, 14C, 21Ne, 26Al, and 36Cl. This rapid development has been facilitated by methodological progress, including improvements in sampling strategies, sample preparation procedures and analyses of cosmogenic nuclides (by accelerator mass spectrometry (AMS) and noble gas mass spectrometry). In order to remain at the cutting edge of the earth sciences the accuracy of TCN methods must be significantly improved. However, it is the consensus of practitioners in the field that further developments are instead moving toward an impasse. This limitation is imposed, not by methodological considerations, but rather by incomplete understanding of the fundamental physical processes, and by lack of rigorous intercomparability between different investigators and methods. The global distribution of cosmogenic nuclide production depends on a number of interrelated factors, and thesefactors must be simultaneously controlled in order to arrive at the equations and parameters that accurately define production rates at all points, and over geological time. This task is far beyond the capability of any individual investigator.In order to achieve this next, necessary, step the CRONUS-Earth Project is proposed. The projecthas the following goals: (i) to establish a rigorous basis for intercomparison between measurement of different nuclides and by different investigators, (ii) to provide a firm linkage between cosmic-ray physics and the systematics of the TCN produced by the cosmic rays, and (iii) to produce generally-accepted formulations and parameters for calculation of TCN production. The ultimate goal is to advance the precision and accuracy of all TCN methods from its current range of ~10% to 20% toward a 5% level. This project is envisioned as an international, collaborative effort. CRONUS-Earth consists of six major components: (i) A methodological intercomparison, including sample preparation as well as analytical measurement. (ii) Spatial/temporal distribution of cosmic-ray fluxes, through "mining" existing neutron monitor datasets, modeling of neutron monitor responses, and measurement of saturated in situ 14C altitude/latitude profiles. (iii) Emplacement of artificial targets for 3He, 21Ne, 10Be, 32P and 36Cl production, to link contemporary cosmic-ray fluxes to production rates and scaling factors. (iv) Measurement of production cross-sections using laboratory neutron beams. (v) A numerical modeling effort to integrate the observations and to calculate the effects of past geomagnetic and paleoclimatic changes on cosmogenicnuclide production. (vi) Geological calibration of nuclide production rates, based on independently-dated surfaces worldwide. These will be classified by quality into primary calibration sites and secondary, or "verification", sites that will be used to test the overall production-rate model. These six components comprise a synergistic and coordinated approach to a problem that is clearly beyond the scope of individuals and small research teams. We propose a consortium approach to managing the project, involving multiple investigators, annual meetings to monitor progress, compile data, and exchange with the community, rapid electronic distribution of results, and integration of the final products through a project office charged with disseminating the results to the community. A linked CRONUS-Europe proposal has been submitted to the EU and will be closely coordinated with CRONUS-Earth.The CRONUS-Earth Project will address the NSF intellectual merit review criterion throughestablishing an improved, quantitative, physically-based, understanding of TCN production andaccumulation that can be applied to solve a wide variety of problems in the earth sciences. The Project will address the broader impacts criterion by providing formulations, parameters, and computer codes that will constitute an intellectual infrastructure enabling more consistent, accurate, and widespread application of TCN methods in the earth sciences. Furthermore, the Project will provide a basis for a more formal and organized future approach to promoting consistency in application of TCN methods, such as committees to provide recommended values for parameters. Finally, it will include a component to directly involve undergraduates, and especially minority students, in research in aspects of earth science related to CRONUS.