1147 
which probably begins in the oligocene (gas-, and oil-bearing layers 
from the core of the Sangatta, Bungalun and Sekurau-anticline in 
Kast-Borneo') and continues into the pliocene (oil-layers of P. 
Tarakan). 
MorLENGRAAFF®) demonstrated a short time ago that the tertiary 
oil-deposits of the western part of the East-Indian Archipelago in 
the E., S., and S.W., are marginal to the old ‘Sunda-land” and 
suspects that genetically the oil-formation of North-West Borneo, 
which occupies an analogous situation at the N.W. margin of this 
land-mass, is closely related to the oil deposits on the Dutch terri- 
tories. This view appears to be correct. According to MOLENGRAAFF’s 
conception the origin of the material of the neogene sediments of 
N.W. Borneo must be looked for in the South-East, in the old massif 
of Borneo. Morrey’s (l.c.) view was diametrically opposite to this 
conception. This writer considered the tertiary sediments of Labuan, 
Brunei and Klias to be partly sedimentations at a south-eastern coast 
of a South-Asiatie continent, partly delta-formations of an enormous 
river, which he presumes to have come down from Central-Asia. 
To this divergence of opinion we shall revert presently. 
We will first call attention to the fact that the margins of the 
oligomiocene “Sundaland” will be marked still better by the neogene 
reeflimes than by the diffusion of the oil-, and coaldeposits ; the 
former, whose facies agrees with those of the recent-tropical reeflimes, 
having never been absent from a coastal fringe of any extent, the 
latter originating only under certain favourable conditions of sedi- 
mentation. The most inward oligomiocene reeflime stones, therefore, 
will mark the nearest limit of the border of the island of Borneo 
that was washed by the sea during the neogene. 
When considering the island from this point of view we see that 
there must have been periods in the neogene in which only compar- 
atively small portions of Borneo emerged from the sealevel. 
Beginning in the north we see that neogene reeflimes are known 
of the islands of Balambangan and Banguey*). Of the vicinity of 
Kudat | possess a Lepidocyclina-bearing limestone, found there by 
Dr. W. Horz. Of the basin of the Sg. Kinebatangan miocene litoral 
limes of the G. Gomanton have long been known‘). Of the Batu 
Tjinagat the Geol. Institute of Utrecht possesses a Liepidocyclina- 
1) L. Rurren. These Proceedings, XIX. 1917. p. 728. 
2) G. A. F. Moreneraarr. These Proceedings. XXIII. 1920. p. 440—447. 
8) L. Rurren. Samml. Geol. Reichsmus. Leiden. (1) X. 1915. p. 11—17. 
4) R. Burren Newton and R. Horranp lc. 
74* 
