84 B. KOTO : THE GEOLOGIC STRUCTURE OF 



I. Outer Eastern Archipelago. 



The Tangla Mountains, in the very heart of the ' Roof of the 

 world', lying between the Himalayan and the Kuen-lun system, 

 run from W. N. W. to E. S. E. From the region of mountain- 

 virgation in the East Tibetan frontier, the Tangla proceed in a 

 south-easterly direction towards the ' peripheric ' region, and 

 then, turning to the south, divide up into the parallel chains in 

 Indo-China and Burma, which constitute what is now kr.own 

 as the Further India mountain-system of v. Richthofen. 



The westernmost or Arrakan chain, the youngest of the 

 system, is built up of non-fossiliferous sandstones and shales, 

 usually referred to as Cretaceous,^^ accompanied by serpentine, 

 petroleum wells, salt springs and mud-lumps. It, therefore, re- 

 sembles very closely the Carpathian ranges, the Caucasus, and 

 some parts of the Apennines in many geological features. It has 

 the Flysch facies. Now, this chain (yoma) forms the starting 

 point of the Malayan arc which goes through the small islands 

 of Cheduba and Reguain, the Preparis and the Cocos to the 

 Andamans and the Nicobars, and then proceeds to Babi (Sima- 

 lur), the Miocene coal-bearing Nias, and the Mentawei Islands 

 (volcanic according to Maass) as far as Engano. Along this line 

 of elevations, those of Nicobar G'^roT^p, especially Kar Nicobar, 

 have become, geologically speaking, comparatively well known, 

 through the labours of Hochstetter and C. Schwager.^^ The 

 geologic components of the Nicobars may be arranged in three 



1) Theobald, Geol. Surv. India, 1873. Lately, Noetling has revised the division of the 

 Tertiary system of Burma, and the Axial ridge of the Arrakan-yoma now under consideration, 

 and thinks that they belong to the Cretaceo-Eocene formation. Vide Records Geol. Surv. 

 India, Vol. XXVIII, p. 59. 



2) ' Reise der Novara ', Bd. II, p. 83 et seq. 



