Portal de Periódicos da CAPES

SE Sundaland accretion: palaeomagnetic evidence of large Plio-Pleistocene thin-skin rotations in Buton

1996; Geological Society of London; Volume: 106; Issue: 1 Linguagem: Inglês

10.1144/gsl.sp.1996.106.01.26

2041-4927

Jason R. Ali, John Milsom, Edward M. Finch, Bundan Mubroto,

Geomagnetism and Paleomagnetism Studies

Abstract The Tukang Besi Platform, an Australian microcontinental fragment, began docking with Sundaland in the Pliocene, impacting on east Buton (SE Sulawesi). Fortuin et al. (1989; Journal of SE Asian Earth Sciences , 4 , 107–124) postulated that south Buton had rotated clockwise through about 60° relative to central/north Buton in response to the Tukang Besi collision. A palaeomagnetic investigation was carried out to test this model. Some 41 (of 72) palaeomagnetic sites from the upper Neogene Tondo and Sampolakosa Formations on Buton yielded interpretable data. Sites from south Buton record locally consistent directions, but at sampling localities < 25 km apart deflections are between 0° and 35° clockwise. There is no trend in these data with respect to the broad geotectonic setting. In central Buton declination offsets are negligible. In north Buton localized (kilometre scale) large (30–60°) clockwise and counter-clockwise declination offsets are observed. Effectively the Buton data provide spot markers on cover sequences that have been locally deformed as ‘thin-skin’ sheets. The underlying basement may have experienced the large relative motions proposed by Fortuin et al. (1989) but the upper Cenozoic cover has not been deformed in such a simple way. This study demonstrates that thin-skin sheets associated with continental collision may undergo 30–60° rotations within very short intervals (< 2–3 Ma).