90 



MANUAL or THE NILAGIRI DISTRICT, 



CHAP. V. 



Geology and 

 Mineralogy. 



Upheaval of 

 the ghdts. 



Formation 

 of Nilagiris 



" The first great disturbance which took place was the npheaval of 

 the ghats and the intervening plateau of Mysore, the two main lines 

 of dislocation meeting and possibly terminating in the Neelgherries. 

 The great fault, or system of faults, along which the Neelgherry or 

 Avalanche escarpment of the Kundas was afterwards upraised, 

 probably gave rise to the terminal portion of the Western Ghats, the 

 down-throw at the period being towards the south. Many smaller 

 dislocations, more or less parallel to the two main lines, would be 

 produced during such an upheaval, and in some of these the isolated 

 hill mass of the Neelgherries may have been subsequently upraised 

 to a far greater elevation. 



" The second great disturbance which produced the Neelgherries 

 may have followed the former, either after a certain interval, or as 

 the closing act of a long period of elevation, the upheaving force being 

 more concentrated. The area upheaved was bounded partly by a pre- 

 existing line of fracture and partly by a newly-formed series having 

 an eastern and western direction. During the same period, minor 

 disturbances broke up the country for some miles to the south, and 

 also produced some of those escarpments which have been described 

 as occurring on the Neelgherries, and which were subsequently much 

 modified in form by marine action. It is not improbable that the 

 Neelgherries have been upheaved en masse to some extent since the 

 surface of the plateau received its present form and since that 

 portion of the country has been raised above the sea, for the mural 

 escarpments which bound the Neelgherries are far more precipitous 

 than we could imagine them to have been had they been subjected 

 to marine action during a long gradual process of upheaval from the 

 sea. 



" Of the geological periods during which the disturbances just 

 upheavals not ej^^i^erated took place we can learn nothing in this part of the country, 

 there being no sedimentary rocks that can furnish any clue to this 

 important problem. 



"The Carnatic, and the country through which the Godavery flows, 

 are the districts most likely to afford the much desired information 

 as to the epochs of the disturbance in the Indian peninsula. 



"In describing the great lines of fractux'e in the rocks of the 

 Neelgherries, no notice has been taken of the small quartz veins 

 occui'ring in various parts of the hills, inasmuch as these minor 

 disturbances can scarcely be referred to any distinct system. They are 

 in most cases of no great length or Avidth, and of no economic value. 

 The vein stone in all of them is a pure white quartz, occasionally 

 containing a few crystals of pyrites of tolerable size, and which 

 appear to have the form of the pentagonal dodecahedron. In the 

 vein which is seen cropping out on the hill side where the Avalanche 

 road crosses a stream about seven miles from Octacamund, there is a 

 small quantity of brown haematite (limonite) filling the cavities in the 

 quartz. This is sometimes seen forming irregular pseudomorphs of 

 the pyrites, and it is evident that it has resulted from the decomposi- 



— subsequent 

 in part to the 

 general up- 

 heaval of the 

 country. 



— epoch of 



ascertainable. 



Quartz veins 

 cannot be 

 classed vcith 

 any system. 



— Of no eco- 

 nomic value. 



— Pyrites. 



