It has been thought that ocean temperatures during the early Palaeoarchaean era (around 3.5 billion years ago) were 55–85 °C. But a recent study indicated that the temperatures might be no higher than 40 °C. Here, studies are reported of the oxygen isotope compositions of phosphates in sediments from the 3.2–3.5-billion-year-old Barberton Greenstone Belt in South Africa. The findings indicate a well-developed phosphorus cycle and evolved biological activity in an Archaean ocean with temperatures of 26–35 °C

It has been thought that ocean temperatures during the early Palaeoarchaean era (around 3.5 billion years ago) were 55–85 °C. But a recent study indicated that the temperatures might be no higher than 40 °C. Here, studies are reported of the oxygen isotope compositions of phosphates in sediments from the 3.2–3.5-billion-year-old Barberton Greenstone Belt in South Africa. The findings indicate a well-developed phosphorus cycle and evolved biological activity in an Archaean ocean with temperatures of 26–35 °C