599 



latter — the writers themselves are not quite satisfied. Further on 

 they assert that several eruptions must have taken place in the 

 great old-andesite-massif, and try to substantiate this view by pointing 

 to the facts that, petrographically, the rocks differ rather much, 

 and that remains of different crater-rims are still extant. One 

 of the peaks, however, of these "old" crater-rims — the Goenoeng 

 Limo — is according to the writers a young volcano, while with 

 respect to a second peak — the G. Kentiana — they also suggest 

 the possibility of a younger date, "mais les autres points d'éruptions 

 appartiendront sans doute a I'ancien massif andésitique", (p. 506). 



No conclusive arguments for the high antiquity of the "old" 

 andesites, east of Buitenzorg, are to be found in the text; on the 

 other hand indications are found in the work to show that the 

 writers themselves were wavering in their opinion, and there is, 

 moreover, one important fact that seems to point to a later date. 

 Indeed Vekbeek and Fennema also allude to traces of rather distinct 

 crater-rims inside the massif. If, in addition, we consider that, as 

 they suppose, the "old volcanoes" had to furnish the material 

 for all the strata of the miocene breccia and conglomerates to a 

 thickness of sometimes thousands of meters, and if we also keep in 

 view that, after the miocene, the Tertiary of Java, has undergone 

 at least one intense plication, we can hardly realise that volcanoes 

 should have outlived a very lengthy period of denudation and an 

 intense plication so long as to contain even now distinguishable 

 crater-rims. 



These considerations, which force themselves upon the geologist 

 who travels from Tjiandjoer to Buitenzorg, induced me to make 

 excursions with a view to farther inquiries into the relative age of 

 the Tertiary and the eruptive rocks round about Buitenzorg. From 

 Sept. 1914 to May 1917 I spent 21 days in field work. 



It stands to reason that a minute study of the Sedimentary Tertiary 

 round Buitenzorg can a priori be expected to yield sufficient evidence 

 to decide whether the "Old Andesites" are really older than the 

 sedimentary Tertiary and, consequently much older than the volcanic 

 mantles of Gedeh and Salak, or whether all eruptive rocks about 

 Buitenzorg are coeval. If the "Old Andesites" belong to pre- or old 

 miocene, the miocene strata round these massives must be very 

 coarse-grained ; they must include many fragmentary materials from 

 the old volcanoes near them, they must be "brecciated", as indeed 

 also V. and F. have suggested. If, however, the oldest part of the 

 sedimentary Tertiary in the neighbourhood of the "Old Andesites" 

 appears to be fine-grained and free from or poor in volcanic discharge, 



