A Contribution to the Petrology of the Permian Evaporite Deposits of North-Eastern England

Summary The carbonate associated with the evaporites is dolomite; magnesite has not so far been found. The following sequence of deposition was accompanied by metasomatism at each stage :— Dolomite→ Anhydrite→ Halite. Evidence of replacement of dolomite by anhydrite includes irregular-sided veins, replaced fossils and pseudo-ooliths, porphyroblastic and poikiloblastic crystals. Evidence of normal primary precipitation is also presented. No pre-anhydrite gypsum has been found; this mineral occurs as porphyroblasts and fibrous veins later than anhydrite. Minor occurrences of fluorite and barite in the evaporites are noted. Carboniferous limestones in the “high” beneath Billingham have been replaced by dolomite and ankerite.