Palaeomagnetism of the Exeter Lavas, Devonshire

The directions of magnetization and the magnetic properties of the Exeter lavas and the associated red sediments have been measured. The lavas have been placed in the Stephanian on the basis of recent age determinations (280 m.y.) but they are interbedded with the desert type sediments typical of New Red Sandstone times in southwest England. The directions of the lavas generally show little scatter and are very resistant to both thermal and a.c. demagnetization. This is probably connected with the fact that their remanence is to a large extent due to haematite and a crystallization remanence (CRM). It is likely that the CRM was formed when the lavas were exposed to weathering soon after they were extruded in desert conditions. The palaeomagnetic pole position agrees with that established by an earlier investigation of the lavas. The associated sediments are not altogether satisfactory for rock magnetic studies owing to their friable nature but yield a pole position similar to that of the lavas.