Long-period Milankovitch cycles from the Late Triassic and Early Jurassic of eastern North America and their implications for the calibration of the Early Mesozoic time–scale and the long–term behaviour of the planets
Long-period Milankovitch cycles from the Late Triassic and Early Jurassic of eastern North America and their implications for the calibration of the Early Mesozoic time–scale and the long–term behaviour of the planets
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DOI：
10.1098/rsta.1999.0400
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发表时间：
1999-07
期刊：
影响因子：
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通讯作者：
P. Olsen;D. Kent
中科院分区：
文献类型：
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作者：
P. Olsen;D. Kent
在三叠纪晚期和侏罗纪早期，美国东北部的纽瓦克裂谷盆地积累了超过5公里的陆相地层，主要是湖相地层，以前被解释为热带气候的天文强迫造成了深刻的旋回。纽瓦克的记录是科学和其他取心的结果，几乎完全为人所知，它提供了可以说是现有的最长的气候循环记录之一。在这一记录中，水深和气候的两个指标是沉积结构(深度等级)和沉积物颜色的分类。深度、等级和颜色深度序列显示了与气候进动有关的所有周期。在这里，我们调谐深度等级和颜色记录到404ka的天文周期，并使用这个调谐记录来探索非常长周期气候的存在和起源。在1.75 Ma、1 Ma和700ka左右的周期中，我们不仅在深度等级和颜色记录中发现了非常显著的气候进动调制周期，而且在由调谐过程得出的沉积速率曲线中也发现了非常显著的周期。然后，我们使用颜色和深度等级时间序列来构建晚三叠世天文调谐的时间尺度。虽然调制进动的纽瓦克高频偏心周期与今天没有什么区别，但1.75 Ma周期与基于目前行星基本频率(即2.5 Ma)的预测有很大不同，并提供了内行星混沌行为的第一个地质证据，否则只能通过数值计算得知。
During the Late Triassic and Early Jurassic the Newark rift basin of the northeastern US accumulated in excess 5 km of continental, mostly lacustrine strata that show a profound cyclicity previously interpreted as caused by the astronomical forcing of tropical climate. The Newark record is known virtually in its entirety as a result of scientific and other coring and provides what is arguably one of the longest records of climate cyclicity available. Two proxies of water depth and hence climate in this record are a classification of sedimentary structures (depth ranks) and sediment colour. The depth rank and colour depth series display a full range of climatic precession related cycles. Here, we tune the depth rank and colour records to the 404 ka astronomical cycle and use this tuned record to explore the existence and origin of very long–period climate. We find highly significant periods of climatic precession modulation at periods of ca.1.75 Ma, 1 Ma and 700 ka in not only the depth rank and colour records, but also in the sedimentation rate curve derived from the tuning process. We then use the colour and depth rank time–series to construct an astronomically tuned time–scale for the Late Triassic. While the Newark higher–frequency eccentricity cycles that modulate precession are indistinguishable from today, the 1.75 Ma cycle is significantly different from predictions based on the present day fundamental frequencies of the planets (i.e. 2.5 Ma) and provides the first geological evidence of the chaotic behaviour of the inner planets, otherwise known only from numerical calculations.