Hasanuddin University

Paleostress Analysis by Fault-Slip and Calcite Twin Data in the East Walanae Fault Zone, South Sulawesi, Indonesia

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dc.contributor.author Jaya, Asri
dc.contributor.author Nishikawa, Osamu
dc.date.accessioned 2016-01-06T15:04:53Z
dc.date.available 2016-01-06T15:04:53Z
dc.date.issued 2012-09-17
dc.identifier.issn 1348-3935
dc.identifier.uri http://repository.unhas.ac.id/handle/123456789/16829
dc.description.abstract The Walanae Fault Zone is a major tectonic structure with prominent geomorphic feature linearly extending over 150km in NW-SE direction throughout the south arm of Sulawesi. The Walanae fault system comprises of two parallel faults, namely West (WWF) and East Walanae Fault (EWF) which develop along the eastern margin of the Western Mountains Range and the western margin of Bone Mountains, respectively. The geomorphic trace of EWF can be recognized as a distinct line of slope transformation between Bone Mountains and Walanae Depression, around which Oligocene to Plioscene volcano-sedimentary rocks are intensely deformed (van Leeuwen et al. 2010). Therefore it can be considered that activity of EWF have played a major role of Neogene and Quaternary structural development in this region. The motion of EWF assumed predominance of the sinistral strike-slip on the basis of the shear sense of neighboring major faults, represented by Masupu fault (Coffield et al. 1993; Guritno et al. 1996). However, the timing and sense of fault motion and related deformations during Neogene and Quaternary have not been little known, as well as the status of recent activity of EWF is not established. The aim of this study is to clarify stress states associated with the activity of the East Walanae Fault and its contribution to the tectonics in South Sulawesi during Neogene and Quaternary. We carried out peleostress analysis using multiple-inversion method from the data both fault-slip and calcite twins. We also suggest possibility of a recent activity of EWF by radiocarbon dating. Fault-slip and calcite twin data were collected in volcano-sedimentary rocks of the Middle Eocene-Middle Miocene of Salokalupang Formation and sedimentary rocks of Middle Miocene-Pliocene of Walanae and Taccipi Formations around the fault zone. Twin lamellae and c-axis orientation of calcite were measured in three mutually perpendicular thin sections for each sample under an optical microscope using universal stage. Determination of paleostress tensor was performed with MIM software (Yamaji et al. 2010). Because the strata in which fault-slip and calcite twin data were collected are highly tilted by folding, the data has been untilted using the software ‘KUT’ by Tomita and Yamaji (2003). Both fault-slip and calcite twin data yield consistent stress states through the studied area, predominance of E-W to NE-SW trending 1 with highly to intermediately plunging 3. These stress states could activate EWF as a reverse fault and account for deformation structures and geomorphologic features around the trace of the fault. A minor component of NW-SE to NNE-SSW trending 1 may be a record of strike-slip movement in early tectonic stage. The bedding tilt test suggest that most of meso-scale faults and calcite twins were activated before or early stage of folding. Based on the morphology and percentage of twined grain, it can be estimated that strata around EWF deformed at approximately 1-2km in depth. The activity of EWF is probably consequence of collision of Banda micro continent to the Western Sulawesi since late Miocene. The late Quaternary radiocarbon ages (3050 cal BP and 3990 cal BP) of soils sheared indicate present activity of the EWF. en_US
dc.publisher The Geological Society of Japan en_US
dc.relation.ispartofseries Annual Meeting;119-2012
dc.subject Sulawesi, East Walanae Fault, Calcite Twin, Paleostress en_US
dc.title Paleostress Analysis by Fault-Slip and Calcite Twin Data in the East Walanae Fault Zone, South Sulawesi, Indonesia en_US
dc.type Article en_US
dc.UNHAS.email asri_jaya@geologist.com en_US
dc.UNHAS.Fakultas Teknik en_US
dc.UNHAS.Prodi Teknik Geologi en_US
dc.UNHAS.idno 196909241998021001 en_US

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