TY - JOUR
T1 - Sufficient oxygen for animal respiration 1,400 million years ago
AU - Zhang, Shuichang
AU - Wang, Xiaomei
AU - Wang, Huajian
AU - Bjerrum, Christian J.
AU - Hammarlund, Emma U.
AU - Canas Portela Costa, Maria Mafalda
AU - Connelly, James
AU - Zhang, Baomin
AU - Su, Jin
AU - Canfield, Donald E
PY - 2016/2/16
Y1 - 2016/2/16
N2 - The Mesoproterozoic Eon [1,600-1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0.1% of present levels, sufficiently low to have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon-oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels >4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.
AB - The Mesoproterozoic Eon [1,600-1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0.1% of present levels, sufficiently low to have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon-oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels >4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.
KW - Animals
KW - Atmosphere
KW - Biological Evolution
KW - Oxygen
KW - Respiration
KW - Water
KW - Journal Article
KW - Research Support, Non-U.S. Gov't
U2 - 10.1073/pnas.1523449113
DO - 10.1073/pnas.1523449113
M3 - Journal article
C2 - 26729865
SN - 0027-8424
VL - 113
SP - 1731
EP - 1736
JO - National Academy of Sciences. Proceedings
JF - National Academy of Sciences. Proceedings
IS - 7
ER -
