INTRODUCTION. 3 



by other members of the Survey, 1 it is hoped that it will serve to 

 clear up some of the obscurity prevailing regarding the rock systems 

 of the Aravalli and other related regions, and form a nucleus for 

 further work in the surrounding districts and States. 



Although the described area is principally a portion of the 

 metamorphic complex of the Aravalli Range, it 

 Lmks with surround- a i g0 mc ] U( i e8 f certain formations and igneous 

 iug regions. ......... ,, . , ., 



rocks winch link it up on the one hand with 



Cutch 2 and'Kathiawar 3 and on the other with the western or desert 

 portions of Rajputana. 4 



The actual area herein described does not entirely cover the 

 whole of Idar State, but it roughly coincides 



Ar * a Burve y° d ' w itli most of the area of the State that shows 



solid rock. It is comprised within the following sheets of the 1 



inch to 1 mile Bombay Survev, namely, Nos. 118, 119, 120, 143 



(120), 144 (121), 145 (122), 146 (123), 147 (124), 178 (149) and 179 



(150)— the alternative numbers in brackets referring to the same 



sheets numbered according to the Central India and Rajputana 



Survey. 



LIST OF FORMATIONS. 



The following formations, according to my identification, are present 

 in Idar State, arranged in descending order :— 



Formation. Aoe. 



Soil, blown sand, screo accumulations, river gravels, alluvium with 



kankar and kaolin deposits Recent 



( Laterite and Deccan Trap — not actually visible in the described 

 area, but seen on the southern margin) 



Ahmcdnagar (Himatnagar) Sandstone Series — the probable 

 equivalent of the Umia of Cutch, the Drangadra Freestone of 

 N. E. Kathiawar,and the Songir Sandstone of Baroda . . Cretaceous 



Phyllite Series — with Vein Quartz Purana ? 



Delhi Quartzite Series — sparingly intruded by Aplite Veins, 

 Quartz-porphyry and with a magnosian phase (Dolomite, 

 Steatite and Serpentine) at certian localities .... Purana T 



Aravalli system — consisting of Calc-gneiss, Biotite-gneiss, 

 Amphibolites, Mundeti Series, Muscovite-biotite schist, Horn- 

 blende schist and Gneiss — freely intruded b\ Aplite Veins. 

 Quartz Veins, and massive stocks of Idar Granite and Quartz- 

 porphyry and rare Basic Dykes . ... Upper 



Archa-an ? 



1 Heron, Mem., Geol. Surv. India, Vol XLV, pt. 1. 



2 Wynne, Mem., Geol. Surv. India, Vol. IX. pt. 1. 



8 Fedden, Man., Geol. Surv. India, Vol. XXI, pt. 2. 



* LaTouche, Mem , Geol. Surv. foftft, Vol XXXV, pt. 2. 



