8 M1DDLEMISS: THE GEOLOGY OF IDAR STATE. 



thickness and from drawing continuous horizontal sections. The 

 Aravallis, like much of the Archaean rocks in other parts of India, 

 and like' for instance, the Grenville series in Canada described by 

 Adams and Barlow, 1 betray their real lack of any intelligible 

 stratigraphical sequence by this one fact more than any other, 

 namely, the impossibility of ordinary illustrative sections. An 

 endeavour to calculate the total thickness of the Grenville series 

 along certain lines of section, we are informed (p. 33, loc. at.), 

 resulted in a total of 94,000 feet, out of which 50,000 feet were 

 limestones, which is manifestly too large, being more than four 

 times that of any later rocks of Huronian type— and yet much <>i 

 this was supposed to be definitely bedded limestone 1 



Notwithstanding the above, the petrologies! varieties of this 



complex in Idar State, as presently to be 

 appear to col^rolo 8 described, judging by their surface d>s- 

 gother into one system, tribution, all have the appearance of cohering 

 together into one great system that probably arose during an 

 equally extended and continuous period. For all practical purposes 

 in this area they embrace everything in the way of undilYerentiated 

 or dubious metasedimentary material, with included ancient igneous 

 material, that is deemed to underlie and to be older than the 

 great and similarly coherent rock masses of what will be described 

 as the Delhi Quartzite. 



In general terms, comparing them with other so-called Archaean* 



systems, we may apply to these rocks the words 

 General correlation. of chamberlill aud Salisbury, quoting or para- 

 phrasing Van Hise (Bull. 86, U. S. Geol. Sure. p. 476) which are 



as follows : " While, therefore, the variations in the rock of the 



Archsean complex are great, there is, nevertheless, a certain homo- 

 geneity in the heterogeneity of the whole. No one considerable 

 part of the system is very different from any other considerable 

 part, and no definite and orderly relationship between the different 

 parts has been made out over any considerable area. There appears 

 to be no traceable succession of beds and no definite stratigraphical 

 sequence, such as can be made out in any great series of metasedi- 

 mentary rocks, however, much folded and metamorphosed. So 

 similar are the rocks of the Archaean throughout the various areas 

 where the system occurs, that a suite of unlabelled specimens from 



I Geology of the Haliburton and Bancroft Areas. Canada, Department of Mines, 

 Mem. No. b (1810). 



