Indonesia has been known quite a long past for its rich coal deposits. Our company was given a reconnaissance permit in coal Blocks No.I and II in North Kalimantan in February of this year and conducted an on-spot survey in the area.
The geological knowledge of this arean was very limitedbefore mapping by the geological survey of sumatra had started. only one observation had been published in the "topographische end geologischetion of south sumatra)
The BT. balirang forms two semi-circular craterwalls, whereas the sekincau is a younger eruption-point. the sekincau does not possess an actual cone - shape; it is rather an irregular dome, concicting of andesitic material.
This sheet encludes the topographical map-sheets 1:100.000 Nr. 32, 42 and 43 and the top.detail -maps 1:25.000 Nr.43 a, b, g and h. During the geological survey mimerous rivers were measured which had been roughly indicated on the topographical maps; the geological maps were brough up to date according to these measurements.
Publishing the first sheet of the geological map of sumatra the principles of this work should be discussedin short. - naturally the results of previous investigations
The mapped area comprises the whole of north sumatra, which morphologically forms a characteristic unit and belongs to the province of atjeh and dependencies and in part to sumatra's eastcoast.
Map P1.XVI, to a scale of 1 : 12500, has been surveyed with the boussole tranche nontagne, as to the main ecasurements, while the interosediary measurements have bean done with measuring-chain and had-compass.