Geology And Fault Analysis Of Gedangan Area, Hargomulyo, Gedangsari District, Gunung Kidul Regency, Special Region Of Yogyakarta

Gedangan area is situated in HargoMulyo, Gedangsari District, Gunung Kidul Regency, Special Region of Yogyakarta, Indonesia. The study area is located in mountainous region, a part of Baturagung Range of the Southern Mountains in East Java. Location of the study area shows longitude extend from 110° 34' 00" E to 110° 36' 30"E and also latitude from 7° 49' 30" S to 7° 52' 00" S. Study on geology and structural geology in Gedangan area have not been done yet. Therefore, this research paper concerns with objectives of updating geological map of Gedangan area in scale of 1:25 000 and to conduct fault analysis and relate it with deformation process in terms of kinematic and dynamic aspect. Methodology done throughout the project was preliminary study, geological mapping, field data collection, laboratory works and structural analysis. The study area was divided into 6 lithologic units; tuffaceous sandstone unit and tuff unit (Kebobutak Formation), tuff breccia unit and tuff unit (Semilir Formation), volcanic breccia unit and andesite unit (Nglanggeran Formation). Their age ranged from Late Oligocene to Early Miocene towards South area and each unit was named based on their dominant lithology. In fault analysis, interpretation of lineament shows that the study area has thrust and strike-slip faults pattern with principal stress trending NNW-SSE. This is supported by kinematic analysis, where Jetis Thrust Fault and Ngalang strike slip fault found in the study area can be correlated with strain ellipsoid. Dynamic analysis then explained the estimation of stress that has affected the rocks to trend NNW-SSE. From kinematic and dynamic analysis, the principal stress was proved to have same direction with lineament, thus the interpretation of occurrence strike-slip faults in the study area are accepted. Results from this research can be used for future studies related to geology and fault topic in Gedangan area and its surrounding.