Walker J C, Zahnle K J
Department of Atmospheric and Oceanic Sciences, The University of Michigan, Ann Arbor 48109, USA.
Nature. 1986 Apr 17;320:600-2. doi: 10.1038/320600a0.
The pace of tidal evolution for the past approximately 450 Myr implies an Earth/Moon collision some 1,500-2,000 Myr BP, an event for which there is no corroborating evidence. Here we present the first direct determination of the lunar distance in the Precambrian. We interpret a 23.3 +/- 0.3-yr periodicity preserved in a 2,500 Myr BP Australian banded iron formation (BIF) as reflecting the climatic influence of the lunar nodal tide, which has been detected with its modern 18.6-yr periodicity in some modern climate records. The lunar distance at 2,500 Myr BP would then have been about 52 Earth radii. The implied history of Precambrian tidal friction is in accord with both the more recent palaeontological evidence and the long-term stability of the lunar orbit. The length of the Milankovitch cycles that modulate the ice ages today also evolve with the Earth-Moon system. Their detection in the Precambrian sedimentary record would then permit an independent determination of the lunar distance.
在过去约45亿年里，潮汐演化的速度意味着在约15 - 20亿年前发生过一次地月碰撞事件，但目前并无确凿证据支持这一事件。在此，我们首次直接测定了前寒武纪时期的地月距离。我们在一块25亿年前的澳大利亚条带状铁建造（BIF）中解读出了一个保存下来的23.3±0.3年的周期性，它反映了月球交点潮的气候影响，在一些现代气候记录中已检测到其具有18.6年的现代周期性。25亿年前的地月距离约为52个地球半径。前寒武纪潮汐摩擦的隐含历史与更近的古生物学证据以及月球轨道的长期稳定性均相符。现今调节冰期的米兰科维奇循环的周期也随着地月系统而演化。在前寒武纪沉积记录中对它们的检测将能够独立测定地月距离。
