600 



we can only assume that the andesites were not formed before 

 the deposit of the Tertiary. Again, if the large masses of the old 

 eruptive rocks existed before the folding of the Tertiary, we can 

 expect the tectonic of the Tertiary in the neighbourhood of these 

 massifs to adapt itself in some measure to the large eruptive masses. 

 If, however, the folding of the Tertiary is older than the "Old 

 Andesites", the general tectonic appearance if the Tertiary continues 

 undisturbed up to the eruptive masses. Besides, if the sedimentary 

 Tertiary is younger than the "Old" Andesites we may look for the 

 "Old Andesites" normally disposed, underlying the sedimentary 

 Tertiary in its deep-seated plications. If the Andesites are subsequent 

 in age, we can hardly expect to find their points of emergence in 

 a country so difficult to traverse, but in their neighbourhood the 

 sedimentary Tertiary might show traces of contact-metamorphism, 

 whereas enclosures of sedimentary Tertiary might be found in the 

 Andesites. Facies and tectonic of the sedimentary Tertiary may 

 therefore yield valuable material. We can a priori expect little from 

 a direct comparison of the "Old Andesites" with the recent eruptive 

 rocks in their vicinity. V and F. have already alluded to it that 

 the "Old Andesites" of Java ditfer from the recent Andesites only 

 in being more intensely weathered. If, however, we reflect that the 

 weathering of some recent volcanoes has advanced so far (as instanced 

 by the slopes of Salak and Gedeh) that from the volcanic tuff's 

 colloid matter has been derived, still including recognisable andesite 

 fragments, of a waxy softness, we can realise, that generally the 

 "Old Andesites" can hardly be weathered to a still greater depth. 



Now let us discuss the results of our local inquiry in the direction 

 alluded to: 



When starting from the country-seat Tjiloewar on the road from 

 Buitenzorg te Batavia towards the South-east, ^) one first moves 

 along brownish-red grounds in which occasionally andesitic blocks 

 are revealed at the surface; they are the typical weathering products 

 of the recent Salak-Gedeh tuff" breccia and agglomerates. Prior to 

 reaching the river Tji Keas one descries on some hills yellow 

 grounds, which at the Tji Keas prove to be the weathering product 

 of a bluish-grey, bulbous shaly hard clay (shale), containing in some 

 places little Foraminifera (Rotalidae, Globigerinidae). On the Tji 

 Keas a Globigerina-containing marl-bank occurs in this badly stratified 

 clay (shale), so that the strike and the slope can be measured 

 (N 60°.0, 10°). In some, places the clay — generally fine-grained — 



1) See the accompanying map and profiles. 



