PAUT 4 .] 
Ball: Mahanadi basin and its vicinity. 
181 
rock, not improbably the same bed, is met with between the 90th and 89th milestones, and 
again between the 85th and 84th. In all cases the dip is nearly vertical, and the recurrence of 
the bed may he due to contortion folds. Trap is seen in the intervals. It is a dense dark- 
green rock, and save at Burbruj, was nowhere observed to be amygdaloidal. Near the 
82nd milestone, the road-cutting exhibits sandy grits and shales alternating with trap in 
vertical beds. These imperfect observations were made by me under the very disadvantageous 
circumstances connected with travelling along a road crowded with traffic in the middle of 
May, and at the rate of fifteen miles a day. They do not, however, constitute the first or only 
record of this singular group of rocks. They are mentioned by Mr. W. T. Blanford in 
the manuscript notes of his march from Chanda through the Chhattisgarh country. He 
writes : “ To the east and south of Pallandur* are some hills composed of a singular series 
of formations which have a very sedimentary appearance, hut are, in all probability, decom¬ 
posed volcanic or trappean rocks of ancient date which it is difficult to separate from the 
metamorphics, although their mineral character is veiy unlike that of the hornblend 
rocks, diorite and syenite, usually found associated with the great crystalline formation of 
India. In the hills east of Chisgarh, the rock appears to be mainly composed of quartz 
and felspar. It is pink in colour; associated with it are some red ferruginous shale beds, 
all evidently much altered as if by weathering. In the Garwai Nadi metamorphics occur, 
the peculiar trappean (?) rocks forming apparently a hill range along the south bank for 
some distance, hut the road north of the river crosses a mass of the ferruginous shaly rock 
in one place, and then, about two miles before reaching Chisgarh, ascends a high ghat over 
crystalline and compact trap, probably the undecomposed form of the rock already specified. 
At the base of the ascent are some earthy slaty beds, very similar to those seen in the 
lower Vindhyan sandstones at Nowagaon Tank, but rather more schistose. Some of the traps 
are amygdaloidal, but I do not think there is any probability of their belonging to any 
overlying formation; and although it is possible that they belong to a newer series than the 
metamorphics, they must, I think, until the country is more closely examined, be classed 
with those rocks.” 
Mr. Blanford also mentions the occurrence of conglomerates similar to those already 
described, one of his localities, “ two or three miles east of the Bagh Nadi, ” being probably 
identical with one of those given above. 
Metamokphic Seeies. 
In the wide area under description, the bedded metamorphic rocks very possibly all owe 
their crystalline character to one and the same period of metamorphism; but that they all 
are the result of the metamorphism of hut one uniform series of rocks is most improbable. 
Not only is it possible, to a great extent, to separate these rocks into groups, distin¬ 
guished by marked lithological characters, hut if, as seems probable, the bedding structure 
now seen really corresponds to the original sedimentary sequence, it is scarcely possible to 
conceive that subsequent disturbance could have produced the relations which are sometimes 
found to exist between adjacent sections. On the other hand, such relations might very 
readily be explained by supposing the existence of original unconformity between the beds. 
By some authorities it is maintained that these so-ealled beds are due to foliation on the 
large scale; but when the occurrence in immediate juxtaposition of beds of utterly different 
composition is exemplified by the cases of limestones next to schists and conglomeritic schists 
in contact with crystalline gneisses, and when the cases afforded by the less modified sub- 
metamorphic rocks arc all taken into consideration, the conclusion, that the beds now existing 
* To the south-west of the road section described above. 
