821 



Asymmetrical Reejcaps. 



An asjiiiinetrical development of the geanticlinal axis on either 

 side of the higliest points yields asjninieti-ical reefcaps. This 

 asymnietrj is lironglit abont by the variable degree and direction 

 of the horizontal component of the rate of movement. 



We pnrpose to consider this development more particularly in. a 

 plane at a right angle with the geanticlinal axis, an instance of 

 w^hich is found in the island of Rotti and the island of Jamdena 

 of the Teninïbergionp. Here the reefcaps rise from the northwestern 

 coast gradually up to the main watersheds of the islands, thence 

 descending rapidly towards the south-eastern coasts. Parts of the 

 reefcaps have disappeared through erosion. 



The relationship of these asymmetrical reefcaps, to certain crustal 

 movements may be seen fiom the coincidence of the asymmetrical 

 structure with marked outward bends of the row of islands, to 

 which the named islands belong ^). 



The island of Jamdena lies nearly opposite to a depression in the 

 Sahul-bank and Arafura sea; here the geanticlinal axis met with 

 less resistance and consequently could be moved more easily than 

 elsewhere in the direction of the"Vorlaud". The horizontal component of 

 the rate of movement at a right angle with the geanticlinal axis may 

 be considerably largei- than the vertical ; in connection with this 

 the uprise above the sea will be less, while the unequal size of the 

 horizontal components for various points may increase the asym- 

 metrical forms during the development or decrease them locally. 

 Furthermore it follows that what has been said about the develop- 

 ment of the geanticlinal axes for the transverse coast is also appli- 

 cable to the movements along the longitudinal coasts and also to 

 the relative age of reefs, raised to different heights. The asymmetrical 

 reefcaps to whose development the horizontal movements have 

 been highly instrumental, will rise less high above the sea than the 

 symmetrical, supposing the mountain building forces to be equal. 

 In this connection we may compare the reefs of the island of Timor, 



..X 



Fig. 1. 



1) H. A. Brouwer, 1. c, p. 770-772. 



