Geomorphologic Indices for Transition from Subduction to Arc-Continent Collision in Sumba Island, Indonesia

Friday, 19 December 2014
Christine Authemayou1, Bernard Delcaillau2, Gilles Y Brocard3, Stéphane Molliex1, Maelle Nexer2 and Kevin Pedoja2, (1)IUEM Institut Universitaire Européen de la Mer, Plouzané, France, (2)Université de Caen, M2C UMR CNRS 6143, Caen, France, (3)Univ of Pennsylvania, Philadelphia, PA, United States
The Sumba Island lies in a key area to study the eastern Indonesia geodynamics. It is located in the Sunda-Banda fore-arc in the area of transition from subduction of the Indian oceanic lithosphere (W) beneath the Sunda-Banda arc to arc-continent collision between the Australian continental margin and the Sunda-Banda arc (E). East of the Sumba Island, the western boundary of the Savu basin originated during Middle Miocene by the southeastward slab retreat below the Sunda-Banda arc (Rigg and Hall, 2001). Previous studies has detected a global uplift of the island accommodating the Australian plate - South West Banda Arc convergence (Fleury et al., 2009). This uplift is associated with northeastward tilting and gravitational collapse to the South. Analyses of various geomorphic markers (perched low relief landscapes, rockyshore platform, coral reef terraces, drainages) and of morphometric indices allowed us to localise new structures (faults and folds), to determine the chronology of their activation and to better constraint the uplift history of Sumba Island. These results aim to understand the evolution of the deformation in Sumba Island in regard with its geodynamic context from Middle Miocene to present-day.