Effective elastic thickness of the Northern Australia continental lithosphere subducting beneath the banda orogen (Indonesia): Inelastic failure at the start of continental subduction
Pliocene-Recent continent-island arc collision of the northern Australian continental lithosphere across the Banda orogen from Roti to the Kai Plateau (∼ 121-137°E longitude) has formed an underfilled foreland basin within the Timor-Tanimbar-Aru Trough. Continental collision on northern Australian lithosphere is most advanced near central Timor Island in terms of shortening and absorbing the forearc basin (Savu Basin) within the accretionary prism. Australian continental lithosphere north of area around central Timor Island is believed to be detached from the oceanic lithosphere. Effective Elastic Thickness (EET) of the northern Australian continental lithosphere from Roti to the Kai Plateau are derived using an elastic half-beam model. Modeled deflection is matched to the seafloor bathymetry and the marine complete 3D Bouguer gravity anomalies. The EET varies from 27 to 75 km across the northern Australian continental lithosphere from Roti to Kai Plateau when the thickness of the elastic half-beam is kept constant. The highest EET values lies near central Timor. From the shelf to beneath the Banda orogen, the EET of the northern Australian continental lithosphere is reduced from ∼90 to ∼30 km when the thickness of the elastic half-beam is allowed to vary down dip. Elastic half-beam modeling approximates the Banda orogen as a triangular load and hidden subsurface loads as end-point loads. Wider triangular loads modeling the load contribution from Banda orogen need higher values of EET. Such an observation highlights the role of high EET in thin-skinned collisional tectonics by promoting the support of wider accretionary prisms by parts of foreland basins with higher EET. Variations in EET may result from inelastic yielding in the northern Australian continental lithosphere. Oroclinal bending of the Australian continental lithosphere in the east, from Tanimbar to the Kai Plateau, may create additional yielding and further decrease the EET. Change in EET occurred at the start of continental subduction in the late Miocene-early Pliocene boundary due to change in curvature of the northern Australian lithosphere near the shelf-slope, both in map and cross-sectional view. Evidence for the inelastic yielding of the northern Australian continental lithosphere near the present-day shelf-slope at the continental subduction is found in: (1) the maximum change of EET near shelf-slope in laterally variable EET calculations, and (2) in the almost cessation of normal faulting in late Miocene-early Pliocene seen on seismic reflection data from northern Australian continental shelf-slope. Elastic half-beam models across central Timor do not require end-point loads and may imply that there are no slab pull forces from the oceanic lithosphere that are acting on the leading edge of the subducted northern Australian continental lithosphere. © 2000 Elsevier Science B.V. All rights reserved.
Publication Source (Journal or Book title)
Tandon, K., Lorenzo, J., & O'Brien, G. (2000). Effective elastic thickness of the Northern Australia continental lithosphere subducting beneath the banda orogen (Indonesia): Inelastic failure at the start of continental subduction. Tectonophysics, 329 (1-4), 39-60. https://doi.org/10.1016/S0040-1951(00)00187-6