Abstract

The structure of the Philippine archipelago results from the juxtaposition, between the Late Miocene and the present, of a volcanic belt against fragments of the Eurasian margin and associated marginal basins. The southern Philippines offers the opportunity of studying the mechanics of the deformation from active contraction to a more complex post-docking setting. The docking period is characterized by a compression which began during the early Late Miocene in the central Philippines and has been recently studied in the island of Mindanao. There, deformation initiated in the Late Miocene-Early Pliocene on a NW-trending wrench zone, and continued until the Late Pliocene with thrusting on west-verging flats and ramps within the arc and east-verging thrusts within the Sangihe forearc. This deformation is still active to the south in the Molucca Sea. The post-docking period began in the Early Pleistocene in northern Mindanao and is represented by a new geodynamic framework with a paired subduction zone and strike-slip fault. However, convergence is still active in the Manila and the Negros trenches, although the Philippine fault is not offset. Large wrench faults, which reactivate the ramp faults of the collision stage, transfer strain from the Philippine fault to the Manila and Negros trenches. These observations imply active intra-arc extension and fragmentation within the Philippine mobile belt.