814 



For every separate group we will communicate what is known 

 concerning the geological age : 



Group a. The composition of the sandstone formation of Ambon 

 composed of debris of granite, may indicate, but does not prove the 

 occurrence of granites, which are older than upper Iriassic. Besides 

 these we recognize numerous younger, post-jurassic and tertiary gra- 

 nitic and dioritic rocks in the Moluccas, in Celebes and also in the 

 other islands of the archipelago. 



Group h. Of this group rocks of young-palaeozoic, mesozoic, and 

 tertiary age are known. 



Group c. These rocks are known from Timor')'), but no reliable 

 evidence of their age has been brought forward. In South Celebes 

 there are shonkinites and essexites intrusive in the tertiary volcanic 

 series of this region, from which a tertiary age can be deduced for 

 these rocks. 



Group d. Many of the rocks belonging to this group in the 

 Moluccas and in Celebes are of teitiary age, may perhaps go back 

 to a mesozoic age, while the basic representatives of this group 

 among the basic eruptive rocks are numerous in the peimian and 

 old-mesozoic sediment series of Timor and adjacent islands. Among 

 the younger volcanic rocks there are many andesites (in Celebes 

 also acid effusiva). They are often hard to distinguish from the basalts, 

 the two species of rocks being united by numerous transitions. 



Group e. Are numerous in the permian and old mesozoic sediment 

 series of Timor and adjacent islands; a great part belongs to the 

 tertiary eruptive rocks mentioned sub d, a considerable portion of 

 which may perhaps be traced back to the mesozoic. Basalts also 

 are very numerous among the young-volcanic products. 



Group f. We know leucite-bearing rocks of Sumbawa. They 

 seem to be of young-tertiary age '), while even leucite-basanite has 

 been recorded as a lavaflow on the Southern slope of the Tambora *). 

 In Celebes lencite- and nepheline-bearing rocks are abundant. We 

 have already observed that in South Celebes and in Southern Central 



1) A. WiCHMANK. Gesteine von Timor. Samml. Geoi. Reichsmus. in Leiden. 

 Serie 1. 2. p. 85. 



') H. A. Brouwer. Neue Funde von Gesteinen der Alkalireihe auf Timor. 

 GenU-al Bl. fur Min. etc. 1913. p. 570 seqq. 



8) J. Elbert. Die Sunda Expedition. Bd. II. Frankfm-t a. M. 1912. 



Gf. also G. Rack. Petrographische Untersuchungen an Ergussgesteinen von 

 Sumbawa und Flores. Neues Jahrb. fur Min. etc. Beil. Band 34. 1912. p. 42 seqq. 



*) J. J. Pannekoek van Rheden. Voorloopige mededeelingen over de geologie 

 van Soembawa. Jaarb. v. h. Mijnw. 1913. p. 20. 



