Parent Materials and Climate Control Secondary Mineral Distributions in Soils of Kalimantan, Indonesia

Secondary mineral distributions in soils from Kalimantan, Indonesia, were investigated to examine the effects of the parent materials and climate at different elevations on the distributions. B horizon soils were sampled at 60 sites on gentle slopes at different elevations (20–1700 m altitude). Each major parent material (sedimentary, felsic, and intermediate to mafic) was represented at different elevations. The soil samples were classified from their total elemental compositions using cluster analysis. Secondary minerals were measured by X-ray diffraction and selective extractions. The samples were divided into ferric (high Fe contents), K&Mg (high K, Mg, and Si), and silicic (high Si) groups. The ferric soils were derived from mafic parent materials, whereas the others were derived from felsic or sedimentary parent materials. The K&Mg soils had higher total base contents (suggesting primary minerals) and were less weathered than the silicic soils. Secondary minerals in the ferric soils were characterized by high contents of Fe oxides and gibbsite. The K&Mg and silicic soils had similar secondary mineral (kaolinite and vermiculite) contents, but more mica was found in the former. Only the silicic group soils had secondary mineral contents that changed as the elevation changed (the kaolinite content increased and the vermiculite and poorly crystalline Al and Fe contents decreased as the elevation decreased). Higher temperatures at lower elevations may cause minerals to be altered more. Secondary mineral distributions were primarily controlled by the parent material (mafic or felsic/sedimentary) and, secondarily by the climate, which varied with elevation.