High slip rate for a low seismicity along the Palu‐Koro active fault in central Sulawesi (Indonesia)

Accurate chronological records are critical for understanding the landformsevolution, and, in particular, of alluvial fan sequences emplaced during glocal/global climatic changes. Toward this end, we measured in-situ-produced 10Be in quartz boulders exposed on top surfaces of Sulawesian Late Quaternary alluvial fans. Combined geomorphic study(SPOT image and field analyses) indicate that this site is composed of twoalluvial fan units. In situ-produced 10Be concentrations suggest that they were emplaced during two successive major climatic events. The calculated minimum exposure ages date the younger unit abandonment at 11,000±2,000 years and seem consistent with a Late Interglacial abandonment age (~120,000years) for the older unit. This study demonstrates that using both the neutron and muon components implicated in the production of in situ10Be, surficial erosion rates can be estimated (~6 m/Ma in Sulawesi )and alluvial fan surfaces dated. In particular, it shows that10Be may be used to date fan surface emplacement during the last 120 ka under humid tropical conditions, significantly helping to constrain continental paleo-climatology in these regions.

[1]  Michel Sébrier,et al.  Is the slip rate variation on the Great Sumatran Fault accommodated by fore‐arc stretching? , 1995 .

[2]  E. Pelinovsky,et al.  The 1996 Sulawesi Tsunami , 1997 .

[3]  Bellier,et al.  Slip‐partitioning and fore‐arc deformation at the Sunda Trench, Indonesia , 1998 .

[4]  O. Bellier,et al.  K–Ar age of the Ranau Tuffs: implications for the Ranau caldera emplacement and slip-partitioning in Sumatra (Indonesia) , 1999 .

[5]  C. Vigny,et al.  GPS compared to long-term geologic motion of the north arm of Sulawesi , 1998 .

[6]  J. A. Katili.  Large transcurrent faults in Southeast Asia with special reference to Indonesia , 1970 .

[7]  C. Laj,et al.  New paleomagnetic constraints on the Cenozoic tectonic evolution of the North Arm of Sulawesi, Indonesia , 1994 .

[8]  Bellier,et al.  Cosmic Ray Exposure (CRE) dating in a wet tropical domain: late Quaternary fan emplacements in central Sulawesi (Indonesia) , 1999 .

[9]  D. Wells,et al.  New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement , 1994, Bulletin of the Seismological Society of America.

[10]  D. Bourlès,et al.  Cosmogenic dating ranging from 20 to 700 ka of a series of alluvial fan surfaces affected by the El Tigre fault, Argentina , 1997 .

[11]  Yehuda Bock,et al.  Rapid rotations about a vertical axis in a collisional setting revealed by the Palu Fault, Sulawesi, Indonesia , 1999 .

[12]  Christophe Vigny,et al.  Monitoring of the Palu‐Koro Fault (Sulawesi) by GPS , 1998 .

[13]  Thierry Beaudouin.  Tectonique active et sismotectonique du systeme de failles decrochantes de sulawesi central (indonesie) , 1998 .

[14]  W. Hamilton.  Tectonics of the Indonesian region , 1973 .

[15]  E. Silver,et al.  Collision, rotation, and the initiation of subduction in the evolution of Sulawesi, Indonesia , 1983 .