Geology of the Gunung Danum conservation area: Geochemistry and soil aspects

Abstract

The Gunung Danum Conservation area overlies the oldest crystalline basement rocks in Sabah, which is composed of peridotite, amphibolite and basalt. The Middle Miocene Melange occupies the low lying area and is composed of exotic blocks embedded in a sheared pelitic matrix. The major blocks consist of chert, sandstone, basalt, conglomerate and ultramafic rocks. The relationship between the crystalline basement and the melange is interpreted as a sheared zone in which the basement rocks were upthrusted towards the north. Locally, the contact between the melange and the basalt is believed to be a normal fault dipping to the south. The high concentration of Ni and Cr in stream sediments reflect the high content of these elements in the ultrabasic bedrock of the Gunung Danum area. The Cr is present as clastic grains of high density chromite, whereas Ni and Zn are partly transported in solution and partly as suspended particles. The distribution of soil in the Gunung Danum and the neighbouring areas can be classified into three types, namely: the Bidu-Bidu Association, the Mentapok Association and the Bang Association. The Bang Association of mudstone and sandstone origin occupies the low lying areas, while the Gunung Danum area of ultramafic stock is classified as the Bidu-Bidu Association. The soil type in between is the Mentapok Association of which the parent materials are basic and intermediate igneous rocks. Extensive recent muddy alluvium can be traced along Sungai Danum and Sungai Sabran.