Seeing red in cyclic stratigraphy: Spectral noise estimation for astrochronology
Seeing red in cyclic stratigraphy: Spectral noise estimation for astrochronology
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DOI：
10.1029/2012pa002307
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发表时间：
2012-09
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--
通讯作者：
S. Meyers
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作者：
S. Meyers
[1]天文时标发展的基础是认识到地层数据中的振荡变异性，并相对于零的“噪声”假设对其进行评估。在这项研究中，蒙特卡罗模拟被用来调查两种常用的噪声假设(“常规”和“稳健”AR1方法)的适用性，结果突出了这两种方法在旋回地层学应用中的重要局限性。也许最有问题的是，稳健的AR1方法可能导致夸大的置信度估计和频谱的低频部分内的错误阳性过度聚集，特别是当潜在的噪声过程具有高滞后-1自相关性时。给出典型的旋回地层记录，这种技术往往会造成“显著”的偏心波段变异性，即使是在纯AR1噪声的情况下也是如此。为了克服这些问题，提出了另一种谱噪声估计方法，该方法同时允许偏离AR1假设，并获得高统计功率--即当天文信号存在于数据中时准确识别它们的能力。我们将该方法应用于来自塞拉隆起中新世沉积物的未调谐δ18O数据，表明在与Weedon等人发表的轨道解释一致的频率上具有统计上显著的光谱功率。(1997年)。此外，使用用于天体年代学测试的平均光谱失配方法对重要空间叠层周期的频率安排进行评估，结果表明，可以高度置信度(99.8%置信度)拒绝没有轨道影响的零假设。
[1] Fundamental to the development of astronomical time scales is the recognition of oscillatory variability within stratigraphic data and its evaluation relative to a null “noise” hypothesis. In this study, Monte Carlo simulations are used to investigate the suitability of two commonly used noise hypotheses (the “conventional” and “robust” AR1 approaches), and the results highlight important limitations in both for cyclostratigraphic application. Perhaps most problematic, the robust AR1 method can result in inflated confidence level estimates and excessive clumping of false positives within the low frequency portion of the spectrum, especially when the underlying noise process has a high lag-1 autocorrelation. Given typical cyclostratigraphic records, this technique will often impose “significant” eccentricity band variability, even in the case of pure AR1 noise. An alternative spectral noise estimation method is proposed to overcome these problems, which simultaneously allows for departures from the AR1 assumption, and obtains high statistical power—that is, the ability to accurately identify astronomical signals when they are present in the data. We apply the method to un-tunedδ18O data from Miocene sediments of the Ceara Rise, indicating statistically significant spectral power at frequencies that are consistent with the published orbital interpretation of Weedon et al. (1997). Furthermore, evaluation of the frequency arrangement of the significant spatial bedding periods, using the average spectral misfit method for astrochronologic testing, reveals that the null hypothesis of no orbital influence can be rejected with a high degree of confidence (the 99.8% confidence level).