Lee and Kodama (2009) present a case for a short normal-polarity magnetozone closely associated with the Paleocene-Eocene thermal maximum (PETM), as recorded in a sediment core from the southeastern Atlantic Ocean. On the grounds that this brief (∼53 k.y.) interval is unique in chron 24r, they argue that the coincidence between it and the PETM implies a causal link. They suggest that a correlative magnetozone has been found at Deep Sea Drilling Project Site 690 in the Weddell Sea (Spiess, 1990), but they fail to point out that this site also provides evidence for several other normal-polarity magnetozones that are not associated with climatic events. This is also the case in a continental section in western Canada (Lerbekmo et al., 2008), which they do not consider. The lack of a unique association between the geomagnetic and climatic signals seriously weakens their argument. Indeed, a convincing case for “coupling between Earth's core magnetofluid dynamo sphere and the atmosphere-hydrosphere during an abrupt catastrophic climate event” (Lee and Kodama, 2009, p. 1047) really demands more than a single example.
The data presented by Lee and Kodama indicate a polarity switch, as opposed to a fluctuation in the strength of the geomagnetic field. Their interval of normal polarity may therefore represent a subchron (Cande and Kent, 1992, p. 13,949). This is the interpretation made by Lerbekmo et al. (2008), who also propose a correlation between their Canadian magnetostratigraphic profile and the “tiny wiggles” found in marine magnetic anomalies spanning the early part of chron 24r. On this basis, Lee and Kodama's “Paleocene-Eocene magnetic reversal” is equivalent to subchron 24r.9n, so there is no need for new terminology.