The Implications for Palaeomagnetism of the Chemical, Opaque Mineralogical and Magnetic Properties of some Baked Contacts

A combined magnetic, chemical and opaque mineralogical study of baked rocks of different lithologies adjacent to dolerite dykes has shown that only in the case of red sandstone contact rocks does significant chemical interference by the baking dyke take place. Transfer of iron from the dyke and decrease in the ratio of Fe2O3 to FeO + Fe2O3 are the notable chemical effects. In spite of this chemical interference the combined evidence suggests that baked rocks tests for the antiquity of the NRM of baking rocks are generally valid.