Maturity of central Madagascar's landscape — Low-temperature thermochronological constraints

Abstract

Low-temperature thermochronological data from two profiles across central Madagascar give apatite fission track and apatite (U–Th)/He ages ranging between 258Ma and 176Ma and from 239Ma to 48Ma, respectively. Thermal models derived from these data, as well as modelling of basement denudation and the sedimentary record, indicate that first order topography of central Madagascar developed mainly due to flexural uplift during Mesozoic times. This was in response to successive erosion and depositional loading associated with the sedimentation in the Morondava and Majunga basins, both of which are now exposed along the western margin of Madagascar. Our data suggest that the eastern margin of the island had a similar denudation history and was probably at a similar topographic level before the late Cretaceous break-up of Madagascar and the India/Seychelles block. Cretaceous normal faulting, without major amounts of denudation, led to the development of the present east coast topography defined by a tectonically juvenile escarpment. In the centre of the island Cenozoic tectonics and volcanism has had a minor and localised influence on the landscape of central Madagascar.