The Study of Nature and Origin of the Tobra Formation in the Eastern Part of the Punjab Salt Range

Abstract

The Tobra Formation of the Early Permian age exposed in the Salt Range, shows different modes of deposition. While the lower part is predominantly of glacial origin, the upper horizon indicates lateral variations from giacio-fluvial to esturine and marine conditions. In the eastern Salt Range the formation can be divided into six units on the basis of colour, lithology and the particle size. The lower part is a petromict boulder bed but the upper levels are dominantly composed of coarse sandstone and gritstone. The material constituting the Tobra Formation may have been transported from Rajisthan and further south from Peninsular India or even beyond the present boundaries of the Sub-continent. The rocks exposed in the Aravalli Outliers are much different from the rock assemblage in the Tobra Formation. The Pre-Cambrian-Cambrian rocks of the Salt Range are also missing. It may be assumed that parts of the area south of the Salt Range might have been covered by thick alluvium during Late Palaeozoic time.