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首页> 外文期刊>Journal of quaternary science: JQS >Cumulative probability functions and their role in evaluating the chronology of geomorphological events during the Holocene
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Cumulative probability functions and their role in evaluating the chronology of geomorphological events during the Holocene

机译：全新世期间累积概率函数及其在评估地貌事件年代中的作用

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Cumulative probability functions (CPFs) for large numbers of radiocarbon age determinations are increasingly being used by scientists as a methodology to discern environmental histories. While the recent compilation of regional databases of the radiocarbon dating control for fluvial sediment sequences has been beneficial for identifying gaps in knowledge and stimulating new research, there are a number of problems that critically undermine the use of these CPFs as sensitive hydroclimatic proxies. (i) The CPF method is underpinned by the assumption that each radiocarbon measurement is a true age estimate for a point in time, whereas each measured age in fact forms a scatter around the true age of the sample; (ii) calibration of radiocarbon ages is responsible for much of the structure in CPFs and compounds the problem of scatter and smears the chronological control; (iii) the databases incorporate multiple types of environmental changes differing chronological relationships between the 14C measurements and the dated events, with pre-dating, dating or post-dating chronological control each displaying variable length temporal lags all mixed together in the same analysis; and (iv) the radiocarbon ages from individual case studies need to be more robustly tested before being incorporated into regional databases. All these factors negate the value of CPFs as sensitive proxies of environmental change, because peaks in probability for individual radiocarbon measurements are likely to be an incorrect estimate for the age of a geomorphological event and this problem is compounded by combining probabilities for multiple unrelated events. In this paper we present a critical analysis of CPFs and their interpretation before suggesting alternative approaches to analysing radiocarbon geochronologies of geomorphic events, which include: (i) Bayesian age modelling of river terrace development; (ii) developing regional databases that test specific geomorphic hypotheses; (iii) Bayesian age modelling of palaeoflood records; and (iv) analysis of sedimentation rates.
机译：科学家越来越多地使用用于确定大量放射性碳年龄的累积概率函数（CPF）作为识别环境历史的方法。尽管最近对河流沉积物序列的放射性碳测年控制区域数据库的汇编对于识别知识差距和刺激新研究是有益的，但仍有许多问题严重破坏了将这些CPF用作敏感的水文气候代理。 （i）CPF方法的假设是，每次放射性碳测量值都是某个时间点的真实年龄估计，而实际上每个测得的年龄都会在样品真实年龄周围形成分散; （ii）放射性碳年龄的校准是造成CPF中大部分结构的原因，并加剧了散射和拖延时间控制的问题; （iii）数据库结合了14C测量值和日期事件之间不同时间关系的多种类型的环境变化，并且在同一分析中，前，后或后时间控制分别显示了可变长度的时间滞后; （iv）在将案例研究中的放射性碳年龄纳入区域数据库之前，需要进行更严格的测试。所有这些因素都否定了CPF作为环境变化的敏感代理的价值，因为单个放射性碳测量的概率峰值可能是对地貌事件年龄的不正确估计，并且此问题通过合并多个无关事件的概率而变得更加复杂。在本文中，我们提出了对CPF及其解释的批判性分析，然后提出了分析地貌事件放射性碳年代学的替代方法，其中包括：（i）河阶地发展的贝叶斯年龄模型; （ii）建立测试特定地貌假设的区域数据库; （iii）古洪水记录的贝叶斯年龄模型; （iv）分析沉降速率。

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