118 HOLLAND AND TIPPER : INDIAN GEOLOGICAL TERMINOLOGY. 



of Biliar and the Shillong plateau together with the unfolded Gwa- 

 liors ; but he excluded as Older Palwozoic (chap. IV) the Cuddapahs 

 and Kurnools, with the Lower and Upper Vindhyans. In view 

 of the fact that all members of these two great groups of rocks are 

 unfossiliferous and thus of doubtful age, T. H. Holland proposed 

 in 1906 (Trans., Min. Geol. Inst., Ind., I, 47) to recognise the 

 great unconformity between the foliated formations (Dharwars, 

 Aravallis, etc.), and the unfoliated, but often folded, strata 

 (Cuddapahs, Gwaliors, Vindhyans, etc.) as the main dividing 

 line. The former were thus grouped with the Archcean (q. v.) 

 while for the latter the group name Purana was proposed. The 

 Puranas thus present characters which recall those of the pre- 

 Cambrian formations of the great Lakes region in North America, 

 where the Anhnildes and Keweenawans are formations of the 

 rank of systems lying unconformably on the foliated Lower 

 Huronians. Similar unfossiliferous old formations are known in 

 other parts of the world, for instance in Finland, where the Jot- 

 nian and Jatulian systems lie on the Kalevian (J. J. Sederholm, 

 Bull. Comm. de Fin., No. 23, 95, 1907). At any time one may ex- 

 pect to find the Vindhyans yielding Palaeozoic fossils, and thus 

 find it necessary to exclude them from the Purana group ; but it 

 seems likely that further work will merely serve to confirm the 

 pre-Cambrian age of the older Purana systems. The term Tran- 

 sition cannot now be used except in a purely adjectival sense. 

 Synonymous with Transition in the earlier writings of the Geo- 

 logical Survey is the term sub-metamorphic. Vide, e.g., Mem., 

 Geol. Surv., Ind,., XVIII, 73 (1881), and X, 125, (1873) ; also 

 Man. Geol. Ind., Vol. I, XIX, 3, 9, 28 (1879). 



Trappean grits.— Name used by F. Fedden {Mem., Geol. Surv., Ind., 

 XXI, 78, 90, 1884) to distinguish the laminated gritty and 

 trap-like deposits at the base of the traps in Kathiawar where 

 they are only poorly developed. A. B. Wynne (Mem., Geol. Surv., 

 Ind., V. IX, 56, 1872) uses the term Infratrappean grits for similar 

 beds in Cutch (Kachh). 



Trappoid beds.— Name employed by F. E. Mallet to distinguish No. 4 

 of his sub-divisions of the Lower Vindhyans (Mem., Geol. Surv., 

 Ind., VII, 28, 1869). The rocks include felspathic and other 

 constituents which suggested the similarity to igneous rocks. 

 Examination by E. Vredenburg (Mem., Geol. Surv., Ind., XXXI, 

 93, 107, 1901) shows that the so-called " trappoids " and " por- 



