Mineralogy and micromorphology of soil from gneissic rock in East Luwu, South Sulawesi

Abstract

Different type of rock, climate, and topography will produce specific mineralogical and micromorphological characteristic in soils. There were still a few research related to the influenced of several types of rocks to soil mineralogy and micromorphology, especially from metamorphic rocks. The objective of this research was to examine the characteristics of mineralogical and micromorphological of soil formed from gneissic rock in East Luwu, South Sulawesi. The observation of soil profiles were carried out in four profiles. The mineralogical analysis was carried out by X-ray diffractometer, and micromorphologogical analysis was carried out by using the thin section. Gneissic rock consisted of quartz-gneiss and muscovite-quartz gneiss. Minerals in the soil had mesomorphous alteration stage with class of alteration of 2nd and 3rd that had been altering in 25-75%. The minerals were quartz, goethite, muscovite, gibbsite, hematite, boehmite, and ilmenite. Alteration mineral formed sesquioxide horizon in soil. The high intensity of weathering of gneissic rock was influenced by the high intensity of rainfall, reached 3389mm/year. Nodules as the weathering product dominated in typic soil type. The c/f related distribution was enaulic, related distribution was porphyric and b-fabrics were granostriated and stippled speckeld. High content of oxide mineral with stippled speckeld b-fabric showed the advanced stage of pedogenesis process from the gneissic rock.