Abstract:

The study area, located in the Cappadocia Volcanic Terrain between the dextral Tuz Gölü fault and sinistral Ecemiş fault, was affected by neotectonic forces and accordingly underwent volcanic activity that developed from late Miocene until recent years. Extrusive igneous rocks outcropping in central Anatolia around Susuzdağ (Hamurcu town, Kayseri) and Tekkedağ (Başdere town, Niğde) were mapped using an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral satellite image. Band ratio images of 9/8, (1+4)/(2+3), 6 and (1+4)/(2+3), 8, 4/6 (RGB) were constructed by taking into account ASTER bands corresponding to the characteristic Fe, Al-OH and Fe/Mg-OH absorption features of rocks in the region, and the boundaries of basalt, basaltic andesite/ andesite, dacite and pyroclastic rocks in the region were delineated. It was demonstrated that a band ratio of 9/8 is particularly effective in differentiating basalt and andesite from the surrounding extrusive igneous rocks. In addition, the ferrous iron index, (1+4)/(2+3), clearly indicates dacite domes as bright pixels around Hamurcu town. Incesu ignimbrite covering large areas in the region appears in darker tones than the surrounding rocks in the 4/6 band ratio image due to the fact that it has a relatively shallow absorption feature in ASTER band6. The accuracy of the resultant lithological maps generated from the first-time used band ratio images was verified by comparing the field survey and geological maps. Although there is some uncertainty in discriminating between basalt and andesite, the resultant ASTER images enable us to map extrusive igneous rocks in a cost-effective, reliable and fast manner. The methodology used in this study can be applied for mapping igneous rocks in similar geographic locations in Turkey and around the world.

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