150 Journ. of ihe Asiat. Soc. of Bengal. (May & June, 1915. 
basic dykes—chiefly dolerites—which from their freshness and 
the absence of deformation are regarded as post-Archaean, and 
it has been suggested that they may be of Cuddapah (Algonkian) 
he only other rock formation in Mysore is laterite, which 
is of So casters recent (possibly Tertiary) formation and 
forms a horizontal capping on the upturned edges of the much 
denuded Archaeans. There is little doubt that it is mainly al 
alteration product of the underlying rocks, but the subject is too 
complex and variable to permit of further reference to it here. 
oregoing sequence of events in the history of Southem 
India as recorded in the rocks of the Mysore plateau may be 
exhibited i in the following tabular statement. 
Recent soils and gravels. 
1. 
gee aN te Laterite. Horizontal sheet capping Archaeans. 
Pre-Cam- 
brian 3. Basic Dykes. Chiefly various Dolerites. 
Algonkian ? 
Great Eparchaean Interval. 
4. Felsite and Porphyry dyk 
5. Closepet Granite and a tas massifs of coreepna age. 
6. Charno 8 - bah e and Py ni aes dykes 
7. Charno sifs. 
8. Vieiste: homabendic and 5 emer granulite dykes. 
9. Peninsular gneis Gra and gneissi¢ coll 
ex. 
10. Champion gneiss. Granite porphyry, 
gneisses, felsites and quartz 
orphyries usually co we! 
g opalescent quart2 
frequently associated 
; autoclastic conglomerate 
Ss 
¢ Eruptive Unconformity. 
S Including also :— 
Gitte dt Hvper (chloritic) divi- ( Amphibolites, porte 
3 reenstones etc., mostly intrusive ' 
4 ach ‘chlorite schists). Conglomerates (autoclasti) 2 
q Banded - ferruginous-4 
& ~ i Ce 6 i x btful, por 
a6 sibly igneo ists | 
= FS Quartzites ond nd quarts 
> © stly in 
. y fj seoaelbony ; probably eon 
a 
E 12. sate Dah oe di- Mica schists ; metamorphi# : 
g (Epidiorites igneo a 
ral . and. h orn-blendic Intrtatro met f dion 
schists). and diabasic oe 
(Unknown). 
