812 



III this connection it must be kept in \ ievv that Martin ^) adopts 

 eocene age for a portion of the andesite breccias and the andesite 

 tuffs in Java (étage ?>?, of Vkrbeek) and it is not out of the bounds 

 of probability that similar rocks more to the east in the Sunda 

 row of islands and elsewhere are likewise of old-tertiarj' age. 



We have already pointed to the occurrence of numerous tertiary 

 igneous rocks also in the eastern part of the Archipelago, when 

 discussing the previous groups. When we dwelt on the rocks of 

 Timor's north coast we abstained from mentioning that Wanner *) 

 inclines to adopt a young-miocene age for the augite- and hyper- 

 sthene-andesites and the andesite-tuffs in West-Timor between the 

 rivers N. Bonat and Kapsali. 



According to Verbeek the tertiary igneous rocks are independent 

 mountain ridges or cone-shaped hills; the bases of the old, 

 crater-rims of the large, in part still active volcanoes, often made 

 up of pyroxene-andesite and basalt, are probably somewhat younger 

 (pliocene); they cannot, however, be separated from the younger 

 volcanic products and will, therefore be tieated together with the 

 young volcanic products. 



Ad 6. 



The young-volcanic products (pyroxene-andesites to basalts) build 

 up the volcanic massifs, which are often more or less coniform in 

 consequence of the materials being ejected on all sides round the 

 vent of eruption. They were built up from the young-tertiary period 

 through the quaternary into the present time. 



From the above considerations, to which others could be added, 

 it is sufficiently evident that the results of lecent investigations 

 necessitate a revisal of Verbeek's Memoir published in 1908, as the 

 writer himself has anticipated repeatedly. Whereas he confines almost 

 exclusively tlie intrusive rocks to his two oldest groups, it has been 

 proved conclusively that basic and acid intrusive locks occur in 

 totally different geological series, while volcanic eruptions took place 

 down from the young-palaeozoic, through the mesozoic and the 

 tertiary up to the present period. They were extremely violent in 

 the first and partly also in the second period, but seem to have 

 been restricted chiefly to the region now occupied by Timor and 



1) K. Martin. Vorlaufiger Bericht über geologische Forschungen auf Java II. 

 Samml. des geol. Reichsmus. in Leiden. Bd. iX. p. 194. 



-) .f. Wanner. Geologie von West-Timer. Geol. Rundsch. Bd. IV. 1913. p. 146. 



