Geochemistry of Kalabakan soils

Kalabakan soils have been studied geochemically to understand the source and genetic relations with nearby geologic exposures. The area of Kalabakan village in Sabah is stratigraphically covered in the east by Kalabakan Formation of Early Miocene age which is comprised of shallow marine sandstone, mudstone, shale, and siltstone and interbedded coals. The western part of the area is covered by Kuamut Formation of Middle Miocene age which is lithologically characterized by mélange comprising of basaltic rock, sandstone, mudstone and chert. Towards the south-west, small patches of alluvium are available along the flood plain of River Brantian. A small outlier of Kapilit Formation of Mio-Pliocene age occurs over bukit Tukok. Kapilit Formation comprises of sandstone, mudstone and conglomerates. Study suggests Kalabakan soil is resulted by active erosion of the Mio-Pliocene deposits in the area. The boundary between Kuamut and Kalabakan may be related to a fault through which River Brantian is flowing. Study further suggests that the area at present is more actively washed than eroded. The active washing is carried out through frequent rains and active drainage through river Brantian and its tributaries. High iron concentration in the soil is related to the presence of basaltic mélange in the Kuamut Formation. Iron concentration is very low in Kalabakan soils and in Alluvium. Although the east of the Brantian River is dominated with Kalabakan but samples 5 and 6 are rich in iron concentration suggesting possible presence of basaltic mélange in these locations or subsurface basaltic intrusions even below Kalabakan Formation.