A transient swing to higher oxygen levels in the atmosphere and oceans at similar to 1.4 Ga

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

  • Wei Wei
  • Frei, Robert
  • Robert Klaebe
  • Dongjie Tang
  • Guang-Yi Wei
  • Da Li
  • Lan-Lan Tian
  • Fang Huang
  • Hong-Fei Ling

The mid-Proterozoic (1.8-0.8 Ga) may have witnessed persistent and predominant anoxia at the Earth's surface. However, recent studies suggest that there was a period around similar to 1.4 Ga where oxygen levels might have been transiently elevated, both in the atmosphere and oceans. In order to shed light on this debated topic, we analyzed rare earth elements plus Y (REY) and Cr isotope profiles of the carbonate rocks from the similar to 1.44-Gyr-old Tieling Formation consisting of the lower Daizhuangzi (DZZ) and upper Laohuding (LHD) Members at the Jixian section, North China. The DZZ samples are characterized by middle REE enriched, hump-shaped REY distribution patterns, while those of the LHD Member display seawater-like REY patterns with slightly negative Ce anomalies (0.67 <Ce/Ce* <0.87). Although differing greatly, the REY profiles both in the DZZ and LHD Members indicate the presence of Mn oxyhydroxides and thus an oxygenation at least locally in the shallow seawater of the North China Platform at similar to 1.44 Ga. The middle LHD Member records positive authigenic delta Cr-53 up to 0.48 parts per thousand, indicating an enhanced continental oxidative weathering transiently occurred at similar to 1.44 Ga with pO(2) higher than 1% of the present atmospheric level, and extending the mid-Proterozoic sedimentary record of positive Cr isotope fractionation to as early as similar to 1.44 Ga. Combining the investigations in this study with other published geochemical evidence from the North China Platform and elsewhere, we suggest that there was a transient and global swing to higher oxygen levels in the atmosphere and oceans at similar to 1.4 Ga.

OriginalsprogEngelsk
Artikelnummer106058
TidsskriftPrecambrian Research
Vol/bind354
Antal sider10
ISSN0301-9268
DOI
StatusUdgivet - 2021

ID: 261380422