Impact of tectonic and volcanism on the Neogene evolution of isolated carbonate platforms (SW Indian Ocean)
Résumé
Understanding the impact of tectonic activity and volcanism on long-term (i.e. millions years) evolution ofshallow-water carbonate platforms represents a major issue for both industrial and academic perspectives. Thesouthern central Mozambique Channel is characterized by a 100 km-long volcanic ridge hosting two guyots(the Hall and Jaguar banks) and a modern atoll (Bassas da India) fringed by a large terrace. Dredge sampling, geo-physical acquisitions and submarines videos carried out during recent oceanographic cruises revealed that sub-marineflat-top seamounts correspond to karstified and drowned shallow-water carbonate platforms largelycovered by volcanic material and structured by a dense network of normal faults. Microfacies and well-constrained stratigraphic data indicate that these carbonate platforms developed in shallow-water tropical envi-ronments during Miocene times and were characterized by biological assemblages dominated by corals, largerbenthic foraminifera, red and green algae. The drowning of these isolated carbonate platforms is revealed bythe deposition of outer shelf sediments during the Early Pliocene and seems closely linked to (1) volcanic activitytypified by the establishment of wide lavaflow complexes, and (2) to extensional tectonic deformation associat-ed with high-offset normal faults dividing theflat-top seamounts into distinctive structural blocks. Explosive vol-canic activity also affected platform carbonates and was responsible for the formation of crater(s) and thedeposition of tuff layers including carbonate fragments. Shallow-water carbonate sedimentation resumed duringLate Neogene time with the colonization of topographic highs inherited from tectonic deformation and volcanicaccretion. Latest carbonate developments ultimately led to the formation of the Bassas da India modern atoll. Thegeological history of isolated carbonate platforms from the southern Mozambique Channel represents a new caseillustrating the major impact of tectonic and volcanic activity on the long-term evolution of shallow-water car-bonate platforms
Domaines
| Origine | Fichiers produits par l'(les) auteur(s) |
|---|---|
| Licence |
