The study of stable oxygen isotope ratios (δ18O) of Precambrian cherts suggests that ocean temperatures during the Archaean era (about 3.5 billion years ago) were between 55 °C and 85 °C, but uncertainty about the δ18O of the primitive ocean has led to considerable debate regarding this conclusion. Here, a combined analysis of oxygen and hydrogen istopes sampled from 3.42-billion-year-old Buck Reef Chert rocks in South Africa indicates that the ancient ocean was much cooler than previously thought.
- M. T. Hren
- M. M. Tice
- C. P. Chamberlain
