422 



are found hotli in Hie red deep-sea sliale and in (he liornstone and 

 cliert witli radiolaria (radiolarite). 



As to their occurrence the following information ma}' be given: 



a. The author possesses from the iskiul of Borneo a single, 

 mediumsized nodule, ordy collected by van Maarsevken in cherl 

 from the Danau-formation in the bed of the Long Keloh river in 

 East-Borneo. 



h. On the island of Timor nodules of manganese have been 

 observed in several places in deep-sea deposits; a very beautiful 

 specimen (PI. I, fig. 2) was collected in claysliale with radiolaria, 

 probably of triassic age near the hill Somoholle in the Beboki-district, 

 about 720 metres above sea-level. 



c. On the island of Rotti nodules of manganese were found in 

 several localities in siliceous limestones, marls, siliceous and calca- 

 reous clayshales with nodules and flat concretions of chert all of 

 Jurassic age, which are full of tests of radiolaria. Exceedingly well 

 preserved are the nodules of manganese in rocks from fatu Sua liain') 

 on the north coast of Rotti and the author refers to this locality 

 where in the following pages he describes the composition and (he 

 mode of formation of these nodules. They are always macroscopic- 

 ally well demarcated from the enclosing rock and in consequence 

 of their greater resistance to weathering they gradually more and 

 more protude from the red shales, and white marls in which they 

 are found included, and thus often get detached from the rocks by 

 the process of weathering. Such detached nodules of manganese can be 

 collected in quantities on the beach near Sua Lain. Thus there is 

 evidently a great chance that these loose nodules may be incorporated 

 later on in younger deposits. Verbeek, on the island of Rotti near 

 Bebalain, has found nodules of manganese in marls of plistocene 

 age. I have e.xamined these nodules, and have found that they 

 contain radiolaria identical to those which occur in the nodules 

 found "in situ" in radiolarites. of Jurassic age at different localities 

 on the island of Rotti. These nodules of Bebalain evidently have 

 not originated in the marls of plistocene age, but have been in- 

 corporated as such in the rock. 



3. as slabs or flat concretions. The concretions of mangenese often, 

 are flat, and in this case more or less restricted to definite layers 

 of great horizontal extent ; in this way true bedded manganese 

 deposits may originate. 



1) Fatu = isolated rock or isolated group of rocks. R. D. M. Verbf.ek gives a 

 picture of tfie Fatu Sua Lain in his report on the geology of the Moluccas. Jaar- 

 boek van het Mijnwezen. 37. VVetenscli. ged. p. 317 Batavia 1908. 



