Presentation description

The modern Earth's atmosphere and oceans, rich in molecular oxygen (O2), provide the chemical energy needed for the demanding metabolisms of complex life. Yet, for the initial half of our planet's existence, this life-supporting gas was almost entirely absent. Ushered in by the evolution of oxygenic photosynthesis, the initial rise of O2 in surface environments around 2.5-2.2 billion years ago, dubbed "The Great Oxidation Event" (GOE), represents a dramatic and profound turning point in Earth's history that eventually paved the way for the origin and evolution of complex life. It is now recognized that instead of a simple, short-lived rise, the GOE was a protracted episode where O2 concentrations ebbed and flowed across orders of magnitude before stabilizing at the GOE's terminus. While significant progress has been made in understanding the timing and tempo of oxygenation near the end of the GOE, the dynamics of its early stages remain less well-known. In fact, even questions such as when the GOE begins are still a matter of debate. To remedy this, we take a step back and analyze a large compilation of geochemical data spanning 3.0-2.0 billion years ago, which provides insights into the timing of oxygen rise during this interval. We plan to supplement this work by zooming in to a moment during the early stages of the GOE, where we will apply an emerging tool for tracking the oxygenation of past oceans: thallium isotopes ratios.