GEOLOGY AND HYDROGEOLOGY OF BAKARA DISTRICT, HUMBANG HASUNDUTAN REGENCY, NORTH SUMATERA

• Main Author: Ghazali Putera, Muhammad
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/29206
• Institution: Institut Teknologi Bandung

The research area is located in Baktiraja District, Humbang Hasundutan Regency, North Sumatera. Geographically, the research area is located at UTM coordinates 253000-263000 mN and 475000 – 482000 mE (WGS 1984 47N zone). The research area is 61 km2. According to the BMB classification, the research area can be divided into two geomorphological units, Toba Plateau Unit and Baktiraja Alluvial Plain Unit. The research area is in Young Geomorphic stage. Stratigraphically, the research area can be divided into five non-formal rock units which were formed during Late Carboniferous – Recent, deposited in open shallow marine to fluvial environment. The sequence from older to younger strata are Sandstone Unit, Pyroclastic Breccia Unit, Tuff 1 Unit, Tuff 2 Unit, and Alluvial Deposit Unit. Geological structures in the research area are Bakara Syncline, Tipang Normal Fault and Toba Caldera Ring Fault. The faults were formed in Late Pleistocene, after Tuff 2 Unit was deposited. Aquifer in the research area is in the Sandstone Unit, Pyroclastic Breccia Unit, Tuff 1 Unit, Tuff 2 Unit, and Alluvial Deposit Unit. The type of aquifer in the research area is unconfined aquifer and all water from springs in the research area are suitable for drinking according to PERMEN No.492/MENKES/PER/IV/2010 based on pH and TDS value criteria. The pH value ranges from 6.87 – 8.12 while TDS value ranges from 28.6-141 mg/L.