4.8 Article

Milankovitch cycles in banded iron formations constrain the Earth-Moon system 2.46 billion years ago

出版社

NATL ACAD SCIENCES
DOI: 10.1073/pnas.2117146119

关键词

Earth-Moon system; Milankovitch cycles; Precambrian; banded iron formations; cyclostratigraphy

资金

  1. Dutch National Science Foundation [NWO ALWOP.192]
  2. Swiss National Science Foundation [200021_169086]
  3. Natural Sciences and Engineering Research Council of Canada [RGPIN-2019-07078]
  4. Dr. Schurmann Foundation [2018-136, 2019-145]
  5. Swiss National Science Foundation (SNF) [200021_169086] Funding Source: Swiss National Science Foundation (SNF)

向作者/读者索取更多资源

Cyclostratigraphic analysis and high-precision U-Pb zircon dating of the lower Paleoproterozoic Joffre Member of the Brockman Iron Formation in NW Australia reveal evidence of Milankovitch forcing and provide insights into the Earth-Moon system evolution.
The long-term history of the Earth-Moon system as reconstructed from the geological record remains unclear when based on fossil growth bands and tidal laminations. A pos-sibly more robust method is provided by the sedimentary record of Milankovitch cycles (climatic precession, obliquity, and orbital eccentricity), whose relative ratios in periodic-ity change over time as a function of a decreasing Earth spin rate and increasing lunar distance. However, for the critical older portion of Earth's history where information on Earth-Moon dynamics is sparse, suitable sedimentary successions in which these cycles are recorded remain largely unknown, leaving this method unexplored. Here we present results of cyclostratigraphic analysis and high-precision U-Pb zircon dating of the lower Paleoproterozoic Joffre Member of the Brockman Iron Formation, NW Australia, pro-viding evidence for Milankovitch forcing of regular lithological alternations related to Earth's climatic precession and orbital eccentricity cycles. Combining visual and statisti-cal tools to determine their hierarchical relation, we estimate an astronomical precession frequency of 108.6 +/- 8.5 arcsec/y, corresponding to an Earth-Moon distance of 321,800 +/- 6,500 km and a daylength of 16.9 +/- 0.2 h at 2.46 Ga. With this robust cyclostratigraphic approach, we extend the oldest reliable datum for the lunar recession history by more than 1 billion years and provide a critical reference point for future modeling and geological investigation of Precambrian Earth-Moon system evolution.

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