Interannual-to millennial-scale climate cycles have been recognized in ancient sedimentary strata and may be closely associated with solar activity. However, the physical driving mechanisms of such cycles remain a mystery. To better understand the nature and evolution of suborbital cycles in ice-free conditions, we performed a quantitative analysis of high-resolution phosphorus (P), gray-scale values, and iron (Fe) data obtained from a core deposited in a mid-latitude lake (Funing Formation of the Subei Basin) during the Late Paleocene-Early Eocene. Time series analysis reveals evidence for ∼88-yr and ∼ 11-yr solar activity cycles in the gray value data, and ∼ 20-kyr precession cycles, ∼10-kyr half-precession cycles, and ∼ 2-kyr solar activity cycles in the Fe data. The data indicate that paleoclimate changes in the Subei Basin at this time were driven by both orbital and suborbital cycles. Amplitude modulation analysis suggests that ∼20-kyr precession modulated the amplitude of the observed 2-kyr cycles. It is inferred that the Earth's climate is driven not only by eccentricity-modulated precession cycle, but also by precession-modulated millennial cycles.

中文翻译：

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华东苏北盆地古新世晚期—始新世早期陆地地层的轨道和亚轨道气候旋回


在古老的沉积地层中，人们已经认识到年际到千年尺度的气候周期，并且可能与太阳活动密切相关。然而，这种循环的物理驱动机制仍然是一个谜。为了更好地了解无冰条件下亚轨道循环的性质和演变，我们对晚古新世至早始新世期间沉积在中纬度湖泊（苏北盆地阜宁组）的岩心获得的高分辨率磷 （P） 、灰度值和铁 （Fe） 数据进行了定量分析。时间序列分析揭示了灰度值数据中 ∼ 88 年和 ∼ 11 年太阳活动周期的证据，以及 Fe 数据中 ∼ 20-kyr 岁差周期、∼ 10-kyr 半岁动周期和 ∼ 2-kyr 太阳活动周期的证据。数据表明，此时苏北盆地的古气候变化是由轨道和亚轨道周期共同驱动的。幅度调制分析表明，∼20-kyr 进动调制了观察到的 2-kyr 周期的振幅。据推断，地球的气候不仅受偏心率调制的岁差周期驱动，还受岁差调制的千年周期驱动。