84 
Records of the Geological Survey of India. 
[vol. VIII. 
filled with rock; but it is quite open to supposition that the filling rock was in great part 
trap. The unquestionable tact, that the main Narbada valley itself, formed on the south by 
scarps of Mahadeva strata, is re-excavated out of the covering trap-formation-^the floor of 
the valley being still of this rock at many places in front of the Mahadeva scarp—removes 
any apparent improbability in such a conjecture as that here made regarding the inner vallies 
of tho basin and the pretrappean denudation of the Mahadeva formation. A just estimate 
of this feature is an important factor in our judgment upon the time-relations of the Maha¬ 
deva series, the top member of which is the Jabalpur (Rajmahal) group, in comparison with 
the Bagh series (cretaceous) in this region; and also upon the distinction of the Deccan and 
Rajmahal trappean formations. 
Quaetz-veins and faults. 
The frequent occurrence of strong and continuous quartz-veins is perhaps the most pecu¬ 
liar feature of tho southern zone of this rock-basin. Along the 
Quartz-veins: composition, northern margin, where the contortion of the strata is locally 
greater than here, I have not observed a single case of quartz-veining ; and in other basins 
of these formations the thing is almost unknown. There is, however, one marked feature of 
these veins that has long been familiar to us in many parts of India in metamorphic and 
transition rocks—a peculiar pseudomorphic structure, thin shining plates of pearly white 
quartz, either in parallel arrangement or confusedly entangled, with empty interstices. I do 
not recollect noticing this form in vein-stones of other countries; but in India it seems to 
be nearly universal. The fine lines on these shining plates have suggested that they may be 
after micaceous irou. Stains of iron are common, but there are no signs of any other metal 
in these veins. There is often associated brecciated quartz. 
The whole rock was for long currently designated amongst us as ‘ fault-rock.’ In highly 
contorted and altered strata, where this stone was most familiarly 
Not fault-rock. known, it is generally difficult to establish the fact of faulting; but 
in these little disturbed and unaltered deposits the evidence is often complete. From many 
observations made in this field I can say that this rock seems rather to shun a connec¬ 
tion with faults, as if they were related to opposite results of disturbing action—such as if 
faults occurred along lines of maximum compression and these veins along lines of tension. 
The vein forming the core of the ridge between the Suki and Bhoura streams is at least 
eight miles long, varying from one foot wide m the Takhir clays to six feet in the sandstones. 
In the masive uustratified clays vertical dislocation might not be detected, but there is little 
or no sign of crushing or rubbing alongside the vein, clear sections of which are abundantly 
exposed in the broken ridge south of Deter. In the sandstone it is quite surprising how this 
Assuring of tho rock and introduction of foreign matter does not even locally derange 
the moderate dip of the bed; an indurated shell of sandstone of variable width commonly 
adheres to the south face of the vein, to the rise of the dip ; and in this, as well as in the 
strips of rock enclosed by the ramifications of the. veinstone, the low northerly dip is uniformly 
undisturbed. The best defined and most continuous of the quartz-runs correspond with this 
description. The few cases where the quartz appears locally near the Dolari and Machua 
faults might be quoted on the other side; but besides that these spots are quite local as com¬ 
pared with the length of those faults, it can generally be seen, as in the Tawa and the Phopas, 
that the quartz is located in broken flexures adjoining the fault, where no vertical displacement 
lias occurred, and does not represent what is properly designated by the term fault-rock; it is 
simply veinstone. One of the veins which have given rise to the group of sandstone 
ridges north-west of Shapur is seen on the path descending the Amdhana gorge to the 
south, to run continuously into the gneiss as a comb-vein one foot wide. 
