Memoirs of the Geological Survey of India. Vindhyan Sedimentation in the Son Valley Mirzapur District

In the Son Valley the 'transition' rocks have long been suspect, and the view that the Bijawar tract of this region includes also older rocks has been given expression to in the new edition of the geological map of India on the scale of 1=32 miles, upon which the Son Valley strip of Transitions ' has been arbitrarily divided into a northern strip of Bija- wars and a southern strip of Dharwars. [...] The characteristic mem- ber is the basal conglomerate,) well seen at the top of the ridges south of Kajrahat, south-west of Billi, along the left bank of the Rihund, and south-west of Gangi. [...] There is certainly no doubt about the tuffaceous nature of the beds by Hardi, Harra and eastwards to Khurdan Hill, and it seems that the eastern part of the area recently examined was sufficiently close to the eastern of the two centres of volcanic eruption to show an increase in the amount of clearly recognisable tuffs. [...] Apart from the tuffs and tuffaceous sandstones, silicification of which does not obscure the nature of the parent rock, the origin of the other types of porcellanite is difficult to determine. [...] (2) Vredenburg was unaware of the existence of the Markundi- Jamual fault, and marked all the stages of the Semri series as swing- ing round the projection of Bijawar rock north of Agori.