806 



From tlie foregoing we feel safe to conclude thut among the so- 

 called old basic eruptive rocks of the Moluccas there are rocks of 

 young palaeozoic, mesozoic and probably of tertiary age, and that 

 nothing can be said for certain about the occurrence of rocks older 

 than permian. 



Ad. 2. 



It lias been supposed tliat the granitic rocks of the Moluccas are 

 of pre-permian age, because, anyhow in Ambon, a young palaeozoic 

 sandstone-formation consists of debris of granite. As observed above, 

 we could for this formation rather assume an upper triassic age and 

 the sandstones may as well consist of the debris of crystalline schists, so 

 that there is no proof for the supposed pre-permian age of granites 

 in Ambon. 



Elsewiiere we reported ') that in the islands of the archipelago 

 outside the Moluccas the occurrence of mesozoic granites has been 

 proved or rendered highly [)lausible by the investigations of Moi-en- 

 GRAAFF, ScRivKNOR (for Malacca), ToBLER, VoLZ and the present writer. 

 To this we can add for Celebes the investigations of van Water- 

 schoot VAN DER Gracht") and Abendanon '), which even lend support 

 to the supposition that tertiary granitic to dioritic rocks occur in 

 this island. For the Moluccas we refer to the following facts: 



a. that granitic to dioritic and gabbro-like to peridotitic rocks 

 sometimes occur in close alliance. Even where dykes of granite 

 occur in peridotites, the granitic rocks can in some places be little 

 younger than the peridotites and may have originated by differenti- 

 ation from the same mother magma. 



b. Investigations in the Sulu-islands by Wichmann*) and myself*) 

 point to the occurrence of post-jurassic granitic rocks in connection 

 with contact-phenomena which have been observed in rocks of 

 Jurassic appearance. 



Again the above warrants the conclusion that no positive evidence 

 has as yet been brought forward supporting the occurrence of pre- 

 permian granitic rocks, whereas it has positively been proved that 



1) H. A. Brouwer. On the post-carboniferous age of granites of the highlands 

 of Padang. Proceed. Kon. Ak. v. Wet. Amst. XVllI. 1915. p. 1513 seqq. 



2) W. A. J M. VAN Waterschoot van der Gracht. Voorloopige mededeeling 

 in zake de Geologie van Gentr. -Gelebes. Tijdschr. Kon. Ned. Aardr. Gen XXXII. 

 1915. p. 118 seqq. en Jaarb. v. h. Mijnwezen. 1914. Vol. II. 



') E. G. Abendanon. Geologische en Geographische doorkruisingen van Midden- 

 Gelebes. Deel I. Leiden 1915 p. 58. 



*) A. WicHMANN. Over gesteenten van het eiland Taliaboe. Versl. Kon. Ak. v. 

 Wet. Amst. Juni 1914. 



s) H. A. Brouwer Geologische Verkenningen enz., 1. c. p. 43. 



