Abstract The main cycles of Earth's eccentricity as recorded in paleoclimate archives signify 2nd order terms, combining two g-frequencies associated with the precession of perihelia of the inner planets and Jupiter. However, many weaker cycles are present and may be documented as well. Here we report on a thus far unnoticed ~200-kyr cycle observed in rhythmically bedded marine marls and limestones of early Paleocene age in NE Spain and adjacent France. This cycle is expressed as alternating distinct and less distinct ~100-kyr CaCO3 maxima and associated magnetic susceptibility (MS) minima, which correspond to successive minima of the short ~100-kyr eccentricity cycle. The most plausible explanation is that this ~200-kyr cycle represents a weak but real cycle in eccentricity. Due to its weakness, this cycle is only expressed as alternatingly strong and weak ~100-kyr minima in eccentricity time series, a pattern that is identical to what we observe in the proxy records and outcrop. Its origin as eccentricity cycle is complex as it is composed of 4 to 6 individual components. A simplified solution solely based on the five leading g-frequencies reveals that most of these components originate from combinations of these 5 frequencies. However, they do not correspond to 2nd order terms, which underlie the principal short and long eccentricity cycles, but to much weaker higher order terms. Three of them have been identified as 4th order terms and two as 6th order terms, representing combinations of 2nd order terms, such as the first harmonic, 2(g2 – g5), of the 405-kyr cycle and related components. It is for the first time that the combined effect of such weak components has been identified in paleoclimatic records, which is only possible because they are not overwhelmed by much stronger 2nd order terms in this frequency band. Finally, the typical pattern that results from interference with the much stronger ~100-kyr cycle might be used as a template for testing the accuracy of astronomical solutions in the future.

中文翻译：

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古气候记录首次揭示了难以捉摸的~200-kyr 偏心率周期

摘要 古气候档案中记录的地球离心率的主要周期表示二阶项，结合了与内行星和木星近日点进动相关的两个 g 频率。但是，存在许多较弱的循环，并且也可能被记录在案。在这里，我们报告了迄今为止在西班牙东北部和邻近法国的古新世早期有节奏的层状海洋泥灰岩和石灰岩中观察到的迄今为止未被注意到的~200-kyr 循环。该循环表示为交替的明显和不太明显的 ~100-kyr CaCO3 最大值和相关的磁化率 (MS) 最小值，它们对应于短的 ~100-kyr 偏心率循环的连续最小值。最合理的解释是，这个 ~200-kyr 循环代表了一个微弱但真实的偏心率循环。由于其弱点，这个周期仅表示为在离心率时间序列中交替强弱~100-kyr 最小值，这种模式与我们在代理记录和露头中观察到的模式相同。它作为偏心循环的起源很复杂，因为它由 4 到 6 个独立的组件组成。仅基于五个主要 g 频率的简化解决方案表明，这些组件中的大多数来自这 5 个频率的组合。然而，它们并不对应于二阶项，二阶项是主要的短和长偏心周期的基础，而是对应于弱得多的高阶项。其中三个被确定为四阶项，两个为六阶项，代表二阶项的组合，例如 405-kyr 循环和相关分量的一次谐波 2(g2 – g5)。这是第一次在古气候记录中确定了这种弱成分的综合影响，这只是因为它们没有被这个频段中更强的二阶项所淹没。最后，由于干扰更强的~100-kyr 循环而产生的典型模式可能会被用作未来测试天文解决方案准确性的模板。