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Imaging of the Moho depth in Madagascar through the inversion of gravity data: geodynamic implications
Author(s) -
Fourno JeanPierre,
Roussel Jacques
Publication year - 1994
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1994.tb00895.x
Subject(s) - geology , precambrian , bouguer anomaly , seismology , lithosphere , rift , continental margin , paleontology , crust , inversion (geology) , african plate , continental crust , tectonics , massif , mantle (geology) , cretaceous , basement , gravity anomaly , oil field , civil engineering , engineering
ABSTRACT Several E‐W profiles of Bouguer anomalies across the Precambrian basement were inverted by applying a linearized inversion procedure in the spectral domain and using a simplified two‐layer model with a crust‐upper mantle interface of constant density contrast. From these inverted profiles, a contour map of Moho topography has been constructed which covers the area of exposed Precambrian basement in the eastern and central parts of the island. Such imaging of the Moho depth in particular exhibits a N20°E‐trending zone of substantially thinned crust along the axis of the island. This parallels the east coast margin which resulted from the northward motion of India relative to Madagascar in the Upper Cretaceous. From combined analysis of geological, tectonic and metamorphic observations, this prominent crustal feature in the Precambrian basement of Madagascar is interpreted as the relic of continental lithospheric extension and thinning possibly related to Panafrican collapse tectonics on the eastern edge of the Mozambique belt. This extensional feature would have been reactivated only in part during the rifting and dislocation stages of the Madagascar and India continental blocks as evidenced by an axis of Cretaceous volcanism emphasized by the Ankaratra and Itasy massifs. Final separation nevertheless occurred further east, at the site of the east coast margin.