REKONSTRUKSI STRUKTUR GEOLOGI DI BINUNGAN BLOK 1-2 DAN PARAPATAN, KECAMATAN TANJUNGREDEB, KABUPATEN BERAU, KALIMANTAN TIMUR

Abstract

The research area is administratively located in Binungan Block 1-2 and Parapatan Block, Tanjungredeb District, Berau, East Kalimantan. Binungan 1 – 2 and Parapatan which owned by PT. Berau Coal, separated by Kelai River. The purpose of this study was to determine the geological structure in both block based on the correlation of the well drilling and surface data. The research used field observations to obtain data on surface geology also well correlation using e-logging data, consist of gamma ray log, caliper log, short density log, and long density log. Surface data analysis using stereonet to get the main stress affecting in research area and evolving types of geological structures. Well correlation is a basic method in geological structure reconstruction, which conducted to determine subsurface condition. Lithology of research area, from old to young consisted of clayey sandstone and sandstone units, which included in Middle Miocene aged, Latih Formation and Holocene aged alluvium sediments. The result of data analysis indicated that the geological structures type that evolved in the research area is a plunging syncline with the axis trending north – south and sinistral – wrench fault trending west – east. Syncline is folded sorrounding rocks on the both blocks and continuous from Binungan 1-2 to Parapatan. The sinistral – wrench fault in Kelai River caused the shifting position of the axis of syncline. The geological structure formed during the Pliocene as a result of the coupling fault sliding motion in north and south area of research location. Mechanism of geological structure formation in research area begins with syncline formation with axis trending north – south, the force continues causes the formation of the third order strike – slip fault from mangkalihat fault. This strike – slip fault causes the folds axis cutted and shifted, also caused the plunging syncline. Keywords: stereografis analysis, correlation, geological structure reconstruction