The oxygenation of the atmosphere was a pivotal point in Earth’s evolution. Punctuated environmental perturbations in its run-up laid the foundations for this event.

The rise of oxygen in the early Earth’s atmosphere remains enigmatic in its timing and extent. Insights from thallium isotopes in Archean shales suggest that it may have experienced flips in oxygenation on a global scale prior to 2.5 billion years ago.

Atmospheric oxygen, supplied from the oceans, dramatically rose during the Great Oxidation Event. Our examination of the preceding evolution of seawater oxygenation revealed that the redox state in seawater oscillated between oxic and anoxic conditions before oceanic oxygenation again increased towards the dawn of the Great Oxidation Event.

Deep marine shelf environments experienced fluctuating levels of seawater oxygenation before the Great Oxidation Event, as reflected by oscillations between nitrogen fixation and denitrification recorded by nitrogen isotopes in banded iron formations.

Oxygenated bottom water existed transiently on continental shelves with O₂ penetrating into underlying marine sediments by about 2.65 billion years ago, according to a study of thallium isotopes in Archaean shales.

Before the Great Oxidation Event there was regional-scale, full water-column oxygenation above the continental shelf, according to molybdenum and thallium isotope records that indicate massive manganese oxide burial.

Periods with enhanced iron and sulfide availability that promoted recycling of bioavailable phosphorus from sediments contributed to episodic development of oxygen oases in the Archaean ocean, according to analysis of trace metals, phosphorus and iron from 2.9-billion-year-old sediments.

Biologically available nitrogen in the form of ammonium was abundant in the Late Archaean ocean, according to nitrogen isotope and proxy analyses on 2.7 billion year old shales from Zimbabwe.

The oxygenation of Earth may have been delayed due to high late Archaean extraterrestrial impact rates, which acted as a fluctuating sink of atmospheric oxygen, according to a reassessment of past impactor fluxes and atmospheric chemistry modelling.

Iron input into the ocean is a key control on mineral–organic preservation, and therefore the accumulation of oxygen in Earth’s atmosphere, according to a theoretical model and supported by proxy records for iron phases and cycling.