A Westphalian Tonstein From South Staffordshire

Summary This study is based on a thin band of kaolinite mudstone, a tonstein, of Westphalian age from Hilton Main Colliery in the South Staffordshire Coalfield. Normal petrographic and geochemical methods have been used to study both the rock and fractions separated from it by heavy liquids. In addition to the major elements the following trace elements have been analysed: U, Th, Ga, Pb, Ag, Sn, Zn, Sr, Ba, V, Cr, Mn, Co, Ni, Cu and Be. It is postulated that the tonstein originated as a soil which was subjected to a high degree of chemical weathering in an oxygenated environment on the land before it was eroded and deposited in water where conditions became reducing some time after deposition. Finally the nature and position of the land mass from which the soil was eroded is discussed.