With the Haute Provence region of the external French Alps the internal zone Embrunais-Ubaye nappes rest with a shallow tectonic contact on the Dauphinois external zone. Beneath the Embrunais-Ubaye nappes, the external zone is deformed by south-west facing folds and by thrust faulting, the importance of which has only recently been recognised. The later emplacement of the Embrunais-Ubaye nappes towards the west into the area is generally thought to have been by gravity gliding. Detailed field studies within both the external zone and the Embrunais-Ubaye nappes has allowed the complex Alpine tectonic evolution of Haute Provence to be resolved. These studies have also shown the external zone deformation to be dominated by piggy-back thrust imbrication. A regional transport direction to the south-west and an overall external zone shortening of some 50% have been identified from the investigation of the three-dimensional geometry of thrust surfaces. The prominent south-west facing folds are found to have developed above a major decollement horizon and to have arcuate hinge lines concentric with the Castellane arc. Folds in general are in close association with thrust faults often developing passively as a response to thrust displacement. The Embrunais-Ubaya nappes consist of a number of thrust bounded structural units which have been emplaced into the region in an overstepping sequence. Detailed local mapping of the internal structure of these units has resulted in the identification of a major south-west directed shortening deformation of the Subbrianconnais zone dominated by thrust faulting. A restoration of Subbrianconnais structures gives an estimated north-east to south-west width for the Subbrianconnais zone of over 100km. Although the final emplacement of the Embrunais-Ubaye structural units may have been a superficial gravity gliding phenomenon, possibly as a result of tectonic uplift in the internal zones, the south-west directed thrust shortening of the external zone and probably the Subbrianconnais is the result of thrust displacements climbing from depth reflecting crustal shortening.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637860 |
| Date | January 1987 |
| Creators | Lawson, K. D. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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