The Magazine Hill clay stratum is a weathering product of the black shale facies beds of the Woocalla dolomite and of the siltstones of the Yudnapinna Beds. Some evidence suggests that the stratum was formed during a pre-Marinoan marine regression and that the clays could be a palaeosol. Other evidence suggests they were formed more recently, by deep weathering. The clays are leached, residual material formed from underlying dolomitic shales and siltstones. Where derived from black shales, the final product of this weathering process is a bleached, white kaolinitic clay, the purest deposits of which may have some economic worth. Where the parent shales originally contained a metal-rich component, soluble metals might have been removed, and redeposited to form mineralized bodies.