New Oxygen research; pre-Ediacaran (Introduction)

by David Turell , Monday, July 18, 2016, 14:22 (3050 days ago) @ David Turell

Oxygen levels were very low before the Ediacarans appeared. Using Rock salt researchers have measured the trapped atmospheric gases and found oxygen rising rapidly: - http://geology.gsapubs.org/content/early/2016/07/08/G37937.1.full.pdf+html - "ABSTRACT
We present a new and innovative way of determining the oxygen level of Earth's past
atmosphere by directly measuring inclusion gases trapped in halite. After intensive screening using multiple depositional, textural/fabric, and geochemical parameters, we determined that tectonically undisturbed cumulate, chevron, and cornet halite inclusions may retain atmospheric gas during crystallization from shallow saline, lagoonal, and/or saltpan brine. These are the first measurements of inclusion gas for the Neoproterozoic obtained from 815 ± 15-m.y.-old Browne Formation chevron halite of the Officer Basin, southwest Australia. The 31 gas measurements afford us a direct glimpse of the composition of the mid- to late Neoproterozoic atmosphere and register an average oxygen content of 10.9%. The measured pO2 puts oxygenation of Earth's paleoatmosphere ~100-200 m.y. ahead of current models and proxy studies. It also puts oxygenation of the Neoproterozoic atmosphere in agreement with time of diversification of eukaryotes and in advance of the emergence of marine animal life. - "CONCLUSIONS
We provide the first direct measurements of the oxygen content of the Neoproterozoic atmosphere. After extensive and careful screening of ancient halite crystals, our analysis of Neoproterozoic halite inclusions and their gases sealed during crystallization confirms that average oxygen levels ~815 m.y. ago were 10.9%. Our
atmospheric oxygen measurements indicate an oxygenated environment in which complex life could have emerged and flourished in advance of the Ediacaran and Cambrian explosions. Our direct analysis of gas-bearing inclusions in halite places atmospheric and shallow ocean oxygenation ~100-200 m.y. in advance of most
proxy-based models. Inclusion gas analysis of primary halite is a new and novel paleobarometer of atmospheric oxygen with many potential terrestrial and extraterrestrial applications." - Comment: There is a diagram in the conclusion showing he relationship of this rise in oxygen to the later appearance of the Ediacarans and then the Cambrians. Oxygen is very necessary for animal life, we know, but the availability of oxygen only unlocked the opportunity for its development, and did not demand or produce its development. We are still left with wondering how it came about. was there an underlying drive.