Colony of North Borneo annual report.

  • British North Borneo
Date:
[1959]
Catalogue details

Licence: Public Domain Mark

Credit: Colony of North Borneo annual report. Source: Wellcome Collection.

    201/274 page 165
    raising the sea level by about 300 feet. Thus the mouths and deltas of rivers round most of the coasts became surmerged and extensive mangrove swamps formed. The volcanic rocks of North Borneo include, in addition to those associated with the Chert-Spilite Formation, andesitic tuffs interbedded with Miocene sediments, and lavas of Quaternary age which occur in the southeastern part of the Colony. In central North Borneo, basaltic lavas and tuffs, which are probably older than the Quaternary volcanic rocks, rest on the Crocker Formation and are slightly metamorphosed by plutonic rocks which outcrop nearby. In the southeastern portion of the Colony the volcanic rocks range from basic to acid in composition, and young topo¬ graphical features such as partly dissected volcanoes, plateaux, and valley infillings, present a fascinating study in geomorphology. The intrusive igneous rocks vary in composition from ultrabasic through intermediate types to acid. The ultrabasic rocks are partly sheared bodies of serpentine within the Chert-Spilite Formation, but relatively unaltered dunite, peridotite, and pyroxenite also occur. Some of the ultrabasic intrusions were apparently emplaced at a later date, possibly during the Oligocene; these are found i;i central North Borneo where they form Mounts Tavai and Meliau. Basic plutonic rocks are relatively uncommon, but a layered basic and ultrabasic intrusion has recently been found forming islands in Darvel Bay. The intermediate rocks, mainly dioritic, are usually associated with the earlier period of ultrabasic intrusion and are particularly well exposed in the headwaters of the Segama River. The acid rocks are principally granodioritic with minor amounts of associated granite. Their greatest and most spectacular develop¬ ment is on Mount Kinabalu, and they also form isolated bosses on its eastern flanks. Minor intrusions of granite occur near the centres of igneous activity in southeastern North Borneo. Mineral Resources As a result of geological work during 1959, new discoveries have been made which, in due course, may lead to a mining industry being started in North Borneo. Prospecting for chromite by a mining company has met with encouraging results; research in geochemical prospecting for copper has revealed extensions to known areas of sulphide mineralization; short fibre asbestos has been discovered in the course of routine geological surveying. Progress is being made with installing plant for a limestone quarry on Balambangan Island, and a prospecting permit has been issued to a private company to investigate the resources of the Silimpopon coal field. Numerous enquiries from overseas show that many individuals and companies are interested in prospecting and subsequently developing the mineral resources of this country although, so far, no discovery has been proved to be worth mining.
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