The Remanent Magnetization and Magnetic Properties of Red Sediments

The characteristics of the remanent magnetization of red sediments are first considered, followed by a brief account of present ideas on the origin of these rocks. Possible processes by which sediments in general might acquire a remanent magnetization are postulated, with reference to chemical and depositional remanent magnetization, and these hypotheses are then discussed both from a geological standpoint and in connection with the observed characteristics of the remanence. The experimental work done on the magnetic properties of red rocks is summarized, and this is followed by a discussion of all the available evidence on the origin of the remanent magnetization of red beds, with particular reference to whether it is of a chemical or depositional nature. The importance or otherwise of the red iron oxide in the rocks in contributing to the remanence is also discussed. From the evidence available at the present time no general process of magnetization can be adduced for red sandstones, nor can the NRM be attributed to either the red or black iron oxide present. Chemical magnetization is favoured as the most likely process in many formations.