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.