Earth's history: ocean bottom cross-section restoration project: Environmental upheaval clarification from the Archean to the Proterozoic

Abstract

Earth is a dynamic system which has been relatively stable for some thousands of years, but has undergone monumental changes during its history. Such changes include snowball Earth, several ice ages, bombardments from meteors and the oxygenation events that changed our atmosphere and made the type of life we have on Earth now, possible. The research explained in this article seeks to understand how such events occurred and what were the factors that led to tipping points and the runaway events that followed. It is vital to understand these in detail so that we can use these as an analogue for what is happening on Earth today. Banded iron formations which now represent huge resources for mining companies, have been the subject of study for many years. However, why these bands formed at various times and sometimes so quickly, remains something of a puzzle. Project leader Prof. Kiyokawa notes that: ‘modern oceans contain very little iron and there are no thick accumulations of iron forming on the seabed’. However, this was very different in the Archean era, from which many BIFs date. The only modern analogues are in areas of hydrothermal activity, in which iron bacteria can thrive and access the ready source of iron being emitted from the vents. The iron in solution is precipitated by the bacteria through oxidation, which then falls to the seabed as sediment. Ancient iron sediments are characterised by a process termed ‘redox’ which is the loss of oxygen, usually owing to the effects of being formed in an aqueous environment. BIFs are important because they also reveal a lot about the level of oxygen in earth’s atmosphere and give clues as the timescales and processes involved in rapid rises in oxygen levels, which led to the evolution of oxygen breathing animals on earth.