247 
composition, to the row Soela-islands—Obi—Misool. The northern 
part of Groot-Obi and the other islands of the Obi-group show a 
close resemblance to the northern Moluccas, as appears from the 
large extension of various intrusive and effusive rocks (a.o. many 
serpentines) and from the development of tertiary limestones, sand- 
stones and conglomerates. A mountain-chain, in which the late- 
tertiary sediments often are intensively folded, continues from N.W. 
New-Guinea over Waigeoe and Salawati up to this region. 
In the northwestern part of Groot-Obi [ found andesite, quite similar 
to many tertiary andesites of the archipelago, concordantly covered 
by serpentine, which points to the conclusion, that at least part 
of the serpentines in the Moluccas must be of effusive origin and 
of relatively late, tertiary or late-mesozoic age. This throws a new 
light on the distribution and age of several eruptive rocks in this 
part of the archipelago. If namely, serpentines are of about the same 
age as the younger effusive rocks — without regard to the youngest 
of the voleanoes — they probably have avery large extension. On 
the larger islands these rocks are denudated over large surfaces 
and the fact that the small islands wholly consist of these rocks, 
does not prove, that centra of volcanic action, which may be connected 
by voleanie fissures have existed here. They may as well be the rests 
of a much larger extension of these rocks in a region, which now 
is covered for the greater part by the sea. 
For the moment we will desist from a subdivision of the various 
younger effusive rocks, because the material has not yet been exa- 
mined microscopically. That the serpentines, at least partly, are not 
older than late-mesozoic, agrees with the original hypothesis of 
VERBEEK *), which holds various gabbros, porfyrites, melafyres, peri- 
dotites and serpentines to be probably of cretaceous age; also at 
other places in the Archipelago similar rocks are of cretaceous age. 
In my opinion the facts, as far as they are known, seem to prove 
that in the eastern Moluccas the following zones occur: 
1. A zone characterized by large overthrusts, which surrounds 
the Banda-sea at the inner side. Only the latest tertiary sediments 
did not take part in these overthrusts ; 
2. A zone without overthrusts, in which the mesozoïe and tertiary 
sediments are sometimes folded intensively, sometimes slightly or not 
at all. This zone is lying outside 1 and near the contact, we find 
1 thrust over 2; 
IR. D. M. VERBEEK. Voorloopig Verslag over een geologische reis door het 
oostelijk gedeelte van den Indischen Archipel in 1899. Extra bijv. Javasche Courant 
1900, NO, 66, p. 11. 
