The Olduvai magnetic subchron
The magnetic field flips to normal for 150,000 years, giving the hominin record a dated marker.
- When
- —
- Duration
- 147 thousand years
- Known to
- ± 10 thousand years
- Era
- Early Pleistocene, Quaternary
Between roughly 1.93 and 1.78 million years ago the Earth's magnetic field reverses to normal polarity within the otherwise reversed Matuyama chron. Because the polarity of volcanic ash and lake sediment can be read directly, the boundaries of the subchron are traceable worldwide and can be tied to argon-argon dates. It runs straight through the deposits at Koobi Fora, Olduvai and Dmanisi, which is why the early Homo record can be dated as tightly as it is.