TY - JOUR

T1 - A transient swing to higher oxygen levels in the atmosphere and oceans at similar to 1.4 Ga

AU - Wei, Wei

AU - Frei, Robert

AU - Klaebe, Robert

AU - Tang, Dongjie

AU - Wei, Guang-Yi

AU - Li, Da

AU - Tian, Lan-Lan

AU - Huang, Fang

AU - Ling, Hong-Fei

PY - 2021

Y1 - 2021

N2 - 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.

AB - 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.

KW - REY

KW - Cr isotopes

KW - North china platform

KW - Mid-proterozoic

KW - Oxygenation

U2 - 10.1016/j.precamres.2020.106058

DO - 10.1016/j.precamres.2020.106058

M3 - Journal article

VL - 354

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

M1 - 106058

ER -