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A comparison of inverted basins of the Southern North Sea and inverted structures of the external Alps

1995; Geological Society of London; Volume: 88; Issue: 1 Linguagem: Inglês

10.1144/gsl.sp.1995.088.01.19

2041-4927

Pascale Huyghe, Jean‐Louis Mugnier,

Geological and Geophysical Studies Worldwide

Abstract For several years, the relationships between extensional and contractional features have been studied in detail by numerous authors, and structural rules suggested regardless of the size and the geodynamic context of the inverted structures. Examples from the external part of the Western Alps and its foreland follow these rules (oblique-slip reactivation, buttress effect of normal faults, short-cuts, preserved half-grabens beneath decollement, forced folds, etc.), but are not controlled by the same geodynamic conditions as intra-plate inverted basins. The Jura platform, which is not controlled by extensional tectonics, shows fault reactivation, buttress effects and preserved structures beneath the decollement. Inverted structures are nicely illustrated in the Dauphinois domain of the stretched western Tethyan margin, but the effect of lithospheric weakening inherited from the stretching was reduced at the time of the Neogene shortening, and the maximum burial is induced by nappe loading. Therefore the relative timing of inversion tectonics, maximum burial and maximum temperature are very different in the Bourg-d’Oisans half-graben of the Dauphinois domain than for intra-plate inverted basins of the Southern North Sea, e.g. the Broad Fourteens Basin. Nonetheless, fold structures overlapped by major unconformities developed during early deformation events in restricted areas of the Western Alps. The example of structures in the Devoluy is linked to the inversion of the Vocontian basin, and is followed by a renewal of subsidence prior to the later Alpine shortening. Therefore, the Alps provide geometrical field examples of the interaction between stretching and shortening events, and may give some insight into the geometry of structures on the seismic scale. Intra-plate inverted basins provide examples of folded and faulted structures overlapped by sediments and provide a means of explaining the early shortening events that occurred in the Western Alps which were not related to the alpine evolution.