The magnitude of the palaeomagnetic field: a new non-thermal, non-detrital method using Sundried bricks

A new method for determining the magnitude of the palaeomagnetic field is described. The material used is adobe Sun-dried mud brick, and some of the magnetic properties of these bricks are described. The magnetization acquired by the mud in the higher coercive force region seems to be caused by shear strain (squeezing) alone. This magnetization is called an SRM. The method is tested on a modern adobe brick from Lima, and it is shown to be accurate and repeatable. The method may also be used to determine values of D and I, if the adobe brick is found in situ. Three results from old adobe bricks — two from Peru and one from Egypt — are presented and are compared with the world-wide average of published ancient VDM's.