Abstract
New paleomagnetic data from three lava sequences on Santiago, Cape Verde Islands, are presented. The paleomagnetic data are coupled with Ar 40 / Ar 39 -age determinations, allowing detailed correlations between the three profiles and the Geomagnetic Polarity Time Scale (GPTS). The younger of the profiles, the Ribeira da Barca profile, recorded flows of normal polarity that correlate with the Brunhes Chron, whereas the Porto Formosa profile of reverse polarity correlates with the lower Matuyama Chron. The São Gonçalo profile consists of both reverse- and normal-polarity flows that belong to the Matuyama and Gauss Chron, respectively. Virtual geomagnetic poles (VGPs) from a sequence of flow units in the São Gonçalo profile classify as transitional, and we interpret it as a geomagnetic event (SG-I). Well-defined Ar 40 / Ar 39 ages bound the occurrence of event SG-I to the interval 2.37–2.43 Ma ( ± 2 σ ), which is synchronous with the timing of cryptochron C2r.2r-1 in the marine magnetic anomaly record. This study therefore confirms the existence of cryptochron C2r.2r-1 and indicates that it was a global-scale phenomenon. The VGPs indicate that the field was in a meta-stable transitional state during cryptochron C2r.2r-1, and that it spent some time in or around the paleomagnetic transitional VGP-cluster patch close to Australia.
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