Active denudation morphostructures from SAR ERS-1 images (SW Irian Jaya)

Manuel Pubellier CNRS URA 1759, Dept. Géotectonique, UPMC, 75252 Paris, France

now at : URA 1316, Ecole normale supérieure, 24 rue Lhomond, 75231, Paris. e-mail : pubelliesphene.ens.fr

Benoit Deffontaines CNRS URA 1759, Dept. Géotectonique, UPMC, 75252 Paris, France

Jean Chorowicz Dept. Géotectonique, UPMC, 75252 Paris, France

Jean-Paul Rudant Dept. Géotectonique, UPMC, 75252 Paris, France

Haryadi Permana Indonesian Institute for Sciences, LIPI, Geoteknologi, Bandung, Indonesia

ABSTRACT

The geometry of active denudation, commonly observed in old mountain belts, is described for the the first time in an active setting using remote sensing imagery supported by field data. We favoured the use of SAR ERS-1 images assisted by complementary remote sensing devices, (Landsat TM), to analyse small effects of recent deformation. SAR ERS-1 images are sensitive to minute textural or topographic contrasts in an area where extremely dense vegetation earlier lent difficulties to remote sensing studies. We show that the southern flank of the western Fold-and-Thrust Belt of New Guinea in Irian Jaya is the site of an incipient and active tectonic denudation on the southern leading edge of a very recent (Pliocene-Pleistocene) orogen. The morphology described here is the result of polyphased neotectonics developed in three stages. The Pliocene collision was followed by a strike-slip environment that isolated the front of the belt, and by the currently active gravitational denudation.