729 
than !000 m. of the older coal-free tertiary formation crops out, 
whilst in a still larger and deeper folded part between the rivers 
Sangatta and Bungalan nearly 1500 m. of this formation is to be seen. 
In the region of the river Sekurau, where we find likewise a 
great dome-shaped anticlinal, about 800 m. of the older, coal-free 
tertiary formation have been brought to the surface. 
The second section of the Posteocene, consists again partly of 
hard, grey, concretionary shale and of sandstones which, as a rule, 
are less pure than in the lower formation. Limestone, and marl- 
banks oceur now and then: they contain almost always corals and 
small Lepidocyclinae. Characteristic of this formation are especially 
the —- most numerous — strata of black shining, scaly breaking coal. 
Near Balik Papan this section is represented by the greater part 
of the Pulu-Balang group and the bottom part of the Mentawir 
group, together more than 1300 m. thick. 
Near Samarinda the coal-bearing mountains of Batu Panggal and 
the inferior part of the coal formation of Tenggalung Ajam to a 
thickness of nearly 18000 m. are to be considered as belonging to 
this section. 
Near Bontang the section embraces a complex of strata more than 
1500 m. thick, near Bungalun the formation is nearly 1000 m. thick, 
near Sekurau over 1000 m. 
The youngest section of the tertiary formation in East Kutei con- 
sists for the greater part of clays and sands with numerous seams 
of coal and local intercalations of limestones and marls. In contra- 
distinction to the two former groups the habitus of the rocks is 
however much younger. The hard, grey shales especially have been 
replaced by soft, grey clays, often with impressions of leaves into 
the planes of bedding. Instead of sandstones we usually find loose 
sands, and the shining, scaly breaking blackcoal of the older group 
changes towards the top gradually into dead black and browncoal, 
and at last even into peaty coal. The limestones and marls are in 
by far the most cases free from Lepidocyclinae and Miogypsinae, these 
fossils occur only in some places in the lower parts of the forma- 
tion. The thickness of this section — embracing the younger part 
of the Miocene and the Pliocene — is very important. 
Near Balik Papan — where the greater part of the Mentawir 
group and the Pliocene belong to it — it is more than 2000 m. 
thick, and near Bontang, Bungalun and Sekurau it has about the 
same thickness. 
The post-eocene deposits between Balik Papan and Sekurau have 
consequently a thickness of over 4500 m. The facies of these deposits 
