277 



found among true littoral Le|iidot'\'clina-liines and Globigeriiia-limes. 



Lastlj [)iesnmablj jonng-iieogene rocks are to be found to the 

 North and West of Menokwari. Here Globigerina marls and loose 

 limesands, occur, which indeed do not include typical fossils, but 

 which on account of their quite .young habitus are most likely to 

 be reckoned to the younger neogene. This in fact agrees with the 

 circumstance that some limestones in this region are of littoral 

 facies but do not contain Lepidocyclina, Cyclocljpeus or Miogjpsina. 

 Before this a description was published of limestones from the island 

 of Manaswari, near Menakwari, that were considered to be younger- 

 neogene '). 



Between the localities of old-ueogene limes south of Menokwari 

 and those west ot Rumberpon are situated the high Arfak Moun- 

 tains, which according to Verbeek') and Wichmann ^) are composed 

 of granular eruptive rocks, schists and slates. From the i-egion of the 

 Arfak mountains I received three rocks most likely tertiary and built 

 u|) of (letrilus from the Arfnk Mountains. They are coarse-grained 

 arcoses of marine origin, which together with Corals also contain 

 a very few Globigerina. The minerals represented here are much 

 quartz, orthoclase, perthite and less plagioclase and biotite ; apparently 

 we have to do here with the detritus of acid granites. 



Coarse-grained detritus uf old rocks occurs also frequently in the 

 northern part of "the Bird's head" in the rocks of tertiary age — 

 notably in the old-ueogene rocks. This goes to show that below, 

 and perhaps also at the surface, tliere must e.flst a mountain ranfje of 

 older rocks. The localities marked on the map by an o are those 

 where in the limestones transported fragments of quartzite and 

 phyllite occur. A rock from the basin of the Aer Sebjar contained 

 grains of perthite and orthoclase, which remind us of the detritus 

 rocks of the Arfak mountains. 



The future reports of the Mining Department will undonbtedly 

 contain interesting information on these "older rocks" in the" Bird's 

 head". 



1) Nova Guinea. VI. 2. p. 29. 42. 



') Nova Guinea IV. p. 97. 



») Tijdschr. Kon. Ned. Aardr. Geii. (2). 21. 1904. 



