THE EARLY HISTORY OF ATMOSPHERIC OXYGEN: Homage to Robert M. Garrels

TLDR

The geologic record of atmospheric oxygen is sparse and uncertain, providing only a fragmentary and imprecise picture of its evolution. The paper reviews the Precambrian history of atmospheric oxygen, beginning with a discussion of life before the evolution of oxygenic photosynthesis. The authors summarize evidence constraining oxygen levels, review processes regulating concentrations, and present models of Precambrian oxygen evolution. Oxygen levels rose over time but fluctuated markedly, exhibiting significant swings to both lower and higher concentrations.

Abstract

▪ Abstract This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion of the possible nature and magnitude of life before the evolution of oxygenic photosynthesis. This is followed by a summary of the various lines of evidence constraining oxygen levels through time, resulting in a suggested history of atmospheric oxygen concentrations. Also reviewed are the various processes regulating oxygen concentrations, and several models of Precambrian oxygen evolution are presented. A sparse geologic record, combined with uncertainties as to its interpretation, yields only a fragmentary and imprecise reading of atmospheric oxygen evolution. Nevertheless, oxygen levels have increased through time, but not monotonically, with major and fascinating swings to both lower and higher levels.