Neogene and present extension in Madagascar: structural and geophysical data

Field studies and observations from aerial photographs, remote sensing and numerical field models show that the Meso-Cenozoic and Recent sedimentary s equences of Madagascar are affected by normal faults. These faults, north-s outh, north-northeast-south-southwest and north-northwest-south-southeast t rending, are responsible for the following morphological effects: scarps, b lock tilting and opening of faulted basins, the most important of which bei ng the Lake Alaotra Basin. The general orientation of these brittle structu res and some observations in the field show that the horizontal maximum ext ension is roughly eastwest directed. Other lines of evidence, seismic and g ravimetric, confirm that Madagascar is presently submitted to a crustal and lithospheric extension, parallel to that in East Africa and the Mozambique Channel. (C) 1999 Elsevier Science Limited. All rights reserved.