Reviews—The Geology of India. 321 
depression to great depths in the crust, and by further injection of 
igneous material.” He divides the Archean group in India as 
follows :— 
4, Dharwarian. 
Eruptive unconformity. 
8. Granites, anorthosites, charnockite series, norites, etc., of various 
localities. 
2. Schistose and 
1. Gneissose rocks. 
The Dharwars have attracted a special interest on account of the 
valuable minerals they include: iron-ores in great richness and purity 
in the Central Provinces and Bellary, copper-ores disseminated at 
a particular horizon in Singbhim, and gold in the quartz reefs of 
Kolar are mentioned. 
The Purana Group.—Upon the weathered surface of the highly 
folded Dharwars and the associated schists and gneisses of the Archean 
group enormous thicknesses of sediments were deposited in peninsular 
India. The break in geological time between these two members of 
the Pre-Cambrian, or Azoic rocks, appears to the author so enormous 
as possibly to exceed the entire period of the fossil-bearing rocks, 
i.e. from the earliest Cambrian to recent times. The Purana group 
includes the Cuddapahs of Southern India, amounting to 20,000 feet 
in thickness with several unconformities. Other examples of this class 
occur elsewhere in peninsular India, presenting on the whole a lower 
and an upper series, the latter corresponding generally to the Vindhyans. 
This is a very interesting formation both topographically, as being 
conspicuously displayed along the great escarpment of the Vindhyan 
range, and also lithologically, the rocks being prominently sandstones 
with subordinate beds of shale and limestone yielding lime and 
building-stone of considerable economic value. The system is also 
remarkable for including strata in which diamonds are found, though 
these, we believe, are part of a bedded sediment, and in no sense 
indigenous. The author further speculates on the possible existence 
of representatives of the Puraina group in extra-peninsular areas, 
and notably in the Himalayas, where unfossiliferous beds, occurring 
south of the snowy range and crystalline axis, have been referred, 
without absolute proof, to various members of the regular fossiliferous 
sequence. 
Caupritan AND Post-Cauprian History or Inpra. 
A. The Dravidian Era. 
The oldest fossiliferous strata known in India are found in the 
Salt Range of the Punjab, where beds are exposed with fossils, as 
previously mentioned, whose nearest relatives occur in the Lower 
Cambrian. The Salt Range, we may observe, is both an enigma and 
a godsend to the Indian geologist—an enigma because undoubted 
Cambrian strata repose on a peculiar marl with beds of rock-salt 
and gypsum, which may be of Tertiary age; a godsend, because 
it provides a recognizable base for the paleontological column, but, 
above all, for its wealth in Permo-Carboniferous fossils, which assist 
the interpretation of that system in the Himalayas themselves. The 
DECADE V.—VOL. IV.—NO. Vil. 21 
