Preliminary palaeomagnetic stratigraphy of the Tertiary Yemen Volcanics

Mainly basaltic samples from 60 sites in the Yemen Volcanic Group show somewhat high degrees of between-site directional scatter, but enable normal, reversed and intermediate polarities to be identified during thermal demagnetisation. Individual chrons cannot be assigned directly from the available stratigraphic controls, but can be estimated using published 39Ar/40Ar determinations. The Yemen plateau basalts appear to have begun eruption during chron C11r.1r , some 29 Ma ago, and eruption persisted for some 3 to 4 Myr, probably terminating during chron C8, some 26 Ma ago. While such an initial assessment needs further substantiation, it demonstrates that the combination of radiometric and palaeomagnetic methods provides far greater reliability than either individual technique alone.