BARR CONGLOMERATE

Occuring on the western flank of the Middle Proterozoic Delhi fold belt in Western India, this is an exceedingly deformed conglomerate, first mapped by Heron in 1936 who described the shapes of very highly oblate pebbles as truncheons, torpedoes, cuttle bones etc. There is a downdip stretching lineation developed on the fabric planes which dip subvertically to the east. The strain gradually increases from Megardha to Giri through Barr and Biranthia for a length of 26 km. Roday and Katpatal carried out strain determination in 1992 on detailed lines and showed that the strai magnitude for similar shapes progressively increased from Megardha to Barr. The pebble axes or shapes are "exreme" with X about a metre, Y about 20 cms and Z only 2-3 cm on the average. The strain studies revealed that the principal positive extensions swapped during the course of progressive deformation, giving rise to two subperpendicular lineations. The photograph is of S plane near Giri taken by Y G Katpatal.