KAJIAN ANALISIS SESAR DI PERBUKITAN JIWO BARAT, KECAMATAN BAYAT, KABUPATEN KLATEN, JAWA TENGAH

Abstract

Bayat is any one location in Java Island which located at Central Java that found Pre-Tertiary rocks exposures. Many rocks are jointed caused by tectonic activity, so many geological structure can be found on this location. In the fact, it is very hard to find that geological structure, especially fault, and many explanation about it are general. It need detailed explanation and analysis, so fault zones and the forming mechanism are known. Fault zones and its characteristics in West Jiwo Hills, Kecamatan Bayat, Kabupaten Klaten, Jawa Tengah, are this research objects. This research is consist of taking for certain fault zones and its characteristics based on field observation and fault analysis with stereographic projection using joint data in research location, and also to take for certain the forming mechanism of fault zones to know its tectonic setting. The research method of this research is consist of survey method and descriptive method. The analysis method of this research is consist of topographic analysis, petrographic analysis, stereographic projection, and deciding the relatively chronostratigraphic. The stereographic projection is using field joint data that connected with fault zones characteristic, and also using Dips software. Based on its result, the interpretation about the forming mechanism of fault zones in research location can be known. The geomorphology of research location is consist of two landform units, Structural-Steep Hills Landform Unit and Denudational-Wavy Plain Landform Unit. The stratigraphy of research location, older to younger, consist of Metamorphic Rocks Unit, Sandstone Unit, Eocene Limestone Unit, Igneous Rocks Intrusion Unit, Miocene Limestone Unit, and Alluvial Unit. The geological structure zone of research location is fault zones which consist of two types of fault, dextral fault consist of Sesar Mendatar Tugu, Sesar Mendatar Sari and Sesar Mendatar Kebo, and detachment fault consist of Jowo Detachment Fault. Its fault zones has two major orientations, southwest-northeast (N 217o E) and northwest-southeast (N 330o E, N 122o E, dan N 287o E). The fault zones forming mechanism in research location occurred on two tectonic periods, on Last Cretaceous caused by southwest-northeast subduction that forming Sesar Mendatar Tugu and Sesar Mendatar Kebo, and on Last Eocene-Oligocene caused by north-south subduction that forming Sesar Mendatar Sari and Jowo Detachment Fault.