PART 1.] 
115 
Note on the Lameta or Infra-trappean Formation of Central India, by H, B . 
Medlicott, M. a., f. g. s., Deputy Superintendent, Geological Survey of India. 
Recent work enables us to record some fresh observations regarding the formation 
denoted in tko publications of the Geological Survey as the Lamota or the infra-trappeau 
group of Central India. Although never more than from one to two hundred feet 
in thickness it has a wide range, occurring continuously for great distances along the 
eastern base of the Deccan trap; from the Nai’bada valley round by Amarkantak to the 
Nagpur and Chanda country. It is principally of interest for the evidence it may give as 
to the age of the great volcanic formation with which it is so closely connected. Its 
position in this question is apparently conflicting, and offers an interesting test of the 
independent application of palaeontological determinations. Examined from the east 
these deposits would certainly be (and have been) identified with the very similar inter - 
trappean beds occurring in the adjoining sections; and those have been considered to be Eocene. 
This opinion was first formed from th a facies of the fresh water and terrestrial fossils, 
which are the only organic remains found in those intertrappeans in tho upland country; 
but it has received support from the examination of tho few marine fossils found associated 
with the others in the distant outlier at Rajamahindri near the mouth of the Godaveri. 
This position is geographically related to that of the upper cretaceous deposits of Trichi- 
nopoli; but Dr. Stoliczka has found that the marine fossils of the Rajamahindri inter¬ 
trappeans are distinct from any occurring in those topmost cretaceous deposits. On the 
other hand, examined from the west, up the Narbada valley, tbe Lameta beds would be 
(and have been) connected with the infra-trappean deposits of Bagh and Barwai, and these 
are cretaceous (Middle Cretaceous according to Dr. Martin Duncan, Quar. Jour. Geol. Soc., 
London, Yol. XXI, p. 349). 
The last discussion of this question was by Mr. W. T. Blanford (in Yol. VI, Mem. 
Geol. Sur., pp. 156-160 and 207-218, and Rec. Geol. Sur„ Vol. V, pp. 88-93), and a 
strong case was made for the correspondence of certain infra-trappean deposits through¬ 
out the Narbada valley. Mr. Blanford’s remarks upon the eastern area were not all based 
upon his own observations, but partly upon previous work of old date on the Narbada 
coal-basin (1. c., Vol II), in which it was conjectured that the Lamota beds on the east 
might be the equivalent of the Mahadevjt sandstones of the Paehmari hills. Ho was thus 
led to assimilate tho calcareous portion of the Bagh series and tho sandstones conformably 
underlying them to tbe Lameta limestone and to the Mahaddva sandstone respectively. 
Recent detailed work has shown that all the rocks known as Mahaddva in the Narbada 
region belong to a great plant-hearing series, tire youngest member of which is the 
Jabalpur (jurassic) group; the Lamota deposits being totally unconformahle to this group. 
This separation of tho Lameta and Mahaddva groups is so wide tbat were Mr. Blanford’s 
conjectural identification of the sandstones confirmed, it would give very strong presumption 
of the separation of the two limestones ; hut it was upon the correspondence of these that 
Mr. Blanford laid most stress ; and for them tho case stands much as he left it; the 
stratigraphical break between the cretaceous deposits of Bagh and the trap overlying them 
being much less marked than the break between the trap and the nummulitics of Surat 
and Bharoch. Mr. Blanford was disposed to consider tho volcanic formation to be 
more nearly cretaceous than tertiary. The comparison of tho Rajamahindri fossils had 
not then been made, but Mr. Blanford, to some extent, anticipated the result by saying 
that exact specific identity can scarcely bo expected, the Rajamahindri hand being, 
I think, estuarine, while all the Trichinopoli beds are purely marine.” The separation 
of the Lametas from the intertrappeans has not lately been contemplated by any one; 
Mr. Blanford notices (1. c., p. 216,) how undistiuguishable they are lithological’y; and. 
