Revealing granitic basement of Garba Hill, Muara Dua Region, South Sumatera based on landsat images, structure, and petrography

Abstract

The basement that forms the three large basins on the island of Sumatra (North Sumatra basin, Central Sumatra Basin and South Sumatra basin) is very interesting to study. Previous studyers reported the basement phenomenon of South Sumatra basin is very exceptional because all of the basement boundaries are exposed on the surface. The highland of basement that forms the Garba Hill in Muara Dua, South Sumatra has been identified using Landsat Image band 432 and 753. Hue interpretation from Muara Dua’s area landsat image indicates resistance level of rock, water and vegetation.The blue hue on the image portrays river that flows in this area, like Komering River.The pink, gray and light green hues were identified as lack of resistance of bedrock lithology and interpreted as granitic rocks that had been weathered. The dark green to black hue in the form of original hill shape at an altitude of 798 m above sea level illustrates that the vegetations are thick with more resistance of bedrocks lithology, and based on field observation, crystalline rock in the form of granite was found. This interpretation has been supported by structural observation result and petrographic analysis of several samples of the crystalline rock. The basement alignment pattern observed in the SRTM image indicates trends of N320-350°E. This phenomenon is consistent with the NNW-SSE pattern resulted from structural study. This rock has a mineral composition consisting of quartz, orthoclase, plagioclase, feldspar and biotite. This set of minerals characterizes granitic magma. The specialty of basement in South Sumatera basin need to be studied in more detail using the fission track method to know the evolution of the basic thermal history of the bedrock.